best solar vent for sailboat

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Thoughts on Nicro vs. Sunforce solar vents?

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So I've done a little research and have decided to put in at least one, and probably two, solar vent fans. One in the hatch covering the stern lazarette (it already has a passive dome vent in it, which I will replace with a solar vent fan) and probably one in the small acrylic (I think it's acrylic) hatch over the dinette. I figure that way, I can set the one over the dinette to draw air in and fit the one in the lazarette with a hose down to the bilge and set it to draw air out and get a nice circulation through the cabin and bilge. Anyhow, I'm comparing what's out there - Nicro seems to be the most popular name, and based on price and reviews, appears to be perceived as the best out there. I find that Defender has Nicro and Sunforce vents . The Sunforce vents are substantially less expensive and look to be lower-profile - I think aesthetically, they look better than the Nicros. But my experience in life in general and with marine hardware in particular is that you don't get what you don't pay for, so I have to wonder, with the price difference, whether the Nicros truly are that much better that they are worth the big price difference. I have never had an opportunity to actually hold them in my hands and compare - the local West Marine doesn't keep a whole lot in stock, and last time I was there, they had only a couple Nicro vents to look at. Anybody have any experience with either or both or have some basis for comparing? Thoughts, opinions, snide remarks (as if I need to solicit those from this crowd)? Thanks!  

I'll never buy Nicro again. I didn't get even 2 years out the one  

There was a thread on Cruisers recently regarding some disappointed users of the Nicro day/night vent. From what I recall the older units seemed to last longer, especially the electric motors. I bought the Nicro product and installed it in November. It doesn't come close to moving air all night and seems to quit around 10PM. I've not tried to replace batteries becuase at night I don't necessarily need the same level of air flow as I do with the sun beating down on the boat. If I had it to do over again I would buy a straight solar vent without the battery option. Mildly disappointed.  

One issue is the batteries that come with the Nicro vents isn't the best, and replacing them with a high-capacity NiMH rechargeable helps a lot.  

I bought a Sunforce at Fry's Electronics a couple of years ago, and returned it once I opened the package and got a good look at it; it just didn't look like something that would survive on the deck of a boat. Also, I think the reason the Sunforce looks like it's lower profile is that it's a lot larger diameter than the Nicro vent; the actual height above the deck is probably not all that different between the two brands. The Nicro vent I have has lasted several years now. I replaced the C-cell battery with a NiMH and gave the motor shaft a spritz of WD-40 a year and a half ago. It's starting to sound like it needs to be oiled again, other than that it seems to work well.  

SlowButSteady said: I bought a Sunforce at Fry's Electronics a couple of years ago, and returned it once I opened the package and got a good look at it; it just didn't look like something that would survive on the deck of a boat. Also, I think the reason the Sunforce looks like it's lower profile is that it's a lot larger diameter than the Nicro vent; the actual height above the deck is probably not all that different between the two brands. The Nicro vent I have has lasted several years now. I replaced the C-cell battery with a NiMH and gave the motor shaft a spritz of WD-40 a year and a half ago. It's starting to sound like it needs to be oiled again, other than that it seems to work well. Click to expand...

I installed a Nicro 6 years ago and it's still going strong. I removed the battery altogether, so it only runs during the day. Don't like to hear it at night, and don't need air circulation 24/7 (moderate climate).  

The link for the Sunforce posted states 1 year warranty. It is 9.5" in diameter and 3.5" high.  

Attachments

BTW, NiCad batteries don't suffer from a "memory effect" when they aren't charged completely: the effect is supposedly a consequence of repeatedly not discharging completely. In theory, if a NiCad is repeatedly discharged to the same relative charge state, say 40%, again and again the Cd(OH) crystals in the battery that are never reduced to metallic cadmium get too big, and thus resist oxidation/discharge. However, a chemistry-type colleague once told me that NiCads very rarely suffer from a true memory effect. Rather, they get damaged by cheap chargers that over-charge the batteries at the end of their charge cycles.  

silicone spray slideout lube for rv's works great and doesnt attract dirt. lasts longer than wd for me in my rv and on my boat  

OP is right to pick the type with a storage battery, otherwise solar vents run when you don't need them and don't run when you do need them.  

A couple things: 1. If you click on the link for the Nicro , you'll see that it says "High capacity NiMh battery operates vent for up to 40 hours without sunlight on a full charge." So I guess they heard your complaints and no longer use a NiCad battery. 2. If you check out the product manual for the SunForce vent , it states that it has a 2-year warranty on materials and workmanship. So I don't know why their webpage says 1 year warranty - except that the web page says "satisfaction guaranteed." So it very well could be two different warranties - a 1-year satisfaction guaranteed warranty, allowing you do return it if dissatisfied within a year, and a 2-year warranty on defective materials or workmanship. I'm more concerned with the defective item, so the warranty seems to be generally comparable to the Nicro. It also uses a NiMh battery.  

ilikerust said: Anybody have any experience with either or both or have some basis for comparing? Thoughts, opinions, snide remarks (as if I need to solicit those from this crowd)? Click to expand...

We have an older Nicro and I installed a new one 2 years ago over the head. Both are doing well and growing strong. The insect screen is a good feature where we live. I also replaced the low capacity recharable batteries with better ones. It runs stronger and longer...never stops. Dave  

Our Nicro solar vent is at least twelve years old now. We've replaced the battery once, about eight years ago. It runs year round, since the boat is stored outside in winter.  

Reminder - WD40 is not a lubricant! Water Displacement formula #40 was developed for the Atlas missile program in the 60's. There was a problem with condensation in electronics from morning dew. The idea was to use surface tension dynamics to displace moisture with a harmless fluid. 39 formulas were found lacking..... There is nothing wrong with keeping some WD40 aboard for drying out items that were splashed. If I dropped something in salt water like, say, my cell phone or non-waterproof camera I would first dip or rinse it in fresh water. Then fling loose water off and soak it in WD40 spray. Even if it worked right after the incident and a water rinse, I would likely still use the WD40 because corrosion damage happens after the immersion, when air and moisture mix. Practical Sailor did a review of spray lubes for protecting electronics and deck lube tasks. There a number of marine sprays they like for long-lasting lube and corrosion protection. I just tried to find it in my collection without success but I remember they liked the expensive CRC spray and found Boeshield near the middle. I have 20 years experience with Boeshield and like it for light lubrication and electrical protection as it has a strong wicking action. It was developed by Boeing. If you spray Boeshield on a pane of glass and come back a day later you will find the penetrant vehicle has evaporated and what is left is a whitish wax residue which has reasonable staying power. The WD40 company will not discourage you from using their product for just about any purpose - customer ignorance, shadetree mechanic culture and hardware stores all ensure this misused product will be around for a long time but the smart money is on newer and carefully developed formulations.  

Shhhhh..... No one tell my Nicro vent that WD40 is supposed to be such bad stuff; it's still running fine.  

This is an old thread, but I want to ask someone who has installed a Nicro Solar Vent 3000. It is advertised as having a shut off mechanism to keep out green water. I am upgrading my 1973 Pearson 36 to meet the CE standards in the EU and will get the RCD "A" designation. I have to make several upgrades to the boat, double the lifelines, add a switch to the bilge pump and make a way to close off the air vents from the two dorade boxs. An upside down deck plate mounted on the overhead will suffice, but I am curious about the strength of the closing mechanics on the Nicro Solar Vent 3000. Does anyone know how firmly that closing mechanism closes??? Thanks, George DuBose  

I"m concerned that the cheaper Sunforce vent has no positive shut-off for green water in an offshore environment.The nicro has a tubular sleeve that you pull down from inside the trim ring, while inside the boat, to seal the hole off when things get ugly. That alone for me made the decision to go with the more expensive product, compared with the savings offset by the possible monetary damage of shipping a quantity of salt water onto teak and upholstery and personal effects, not to mention the PIA  

My search to find this vestige of knowledge was led by the fear that Defender sent me two "Day & Night" vents but they appear of different makes. One is Nicro and appears to have an older box. The newer one is Marinco but both appear to be from the same manufacture. My concern was that old batteries do not hold up. It sits in the package for years with no charging and there you have it. Some vents last years and and others not so good. So I set out to find out what I already knew. That I need to check the date on the batts. Up date: My suspicion was that Marinco bought out Nicro but I can't find it. The battery in the older appearing box was 30 3 12. The unit was manufacture says 05 10 12 The number not far from the skew says 050912. Marinco is a favorable company to me. They are not far away and any problem I had they fixed beyond my satisfaction. Defender marine will horror themselves if pushed and while the child in me wants to blame the reality is honesty is becoming more and more difficult to find for me. With age comes money to those who can save and there are those will take if you do not know what the value is. The tip off was that they were on sale... ALWAYS check things that have batts for age. A new battery is dated when you buy it for a reason. If it sits on a shelf for a year or two it does matter. I looked at the time to disassemble and replace battery. There is a grease seal and o rings on the panel and screws. Interesting that they say not to smash the O'ring when that is exactly what they did. The older manual says the battery was in a different location. At hundred and fifty bucks these D&N 2000 vents were dearer than I wanted to pay but when I decided to go ahead and sacrifice the money for the good of the boat I never imagined I would not get quality for that price. Most disturbing is how the outside of the package says "battery lasts more than two whole years" which is ironically how old it is. I found the replacement on Amazon but with shipping its 40 bucks. It is not the same as the battery it came with and reviews were not promising. Question: Will this battery be a couple and a half years old too? I will call Marinco in the morning and it's my bet they will make it right. If I have to go to Defender it will cut them deeper. I will ship the kit and kabootal all the way back East for a replacement or refund. Do you think they don't know? Just because you pay the money does not mean you get the quality. At least the computer makes life harder on the saleman. The other unit has no date on the battery but the unit is 2013. I will not like it but I will keep it...  

Marinco and Nicro are the same company. If the batteries die prematurely, Marinco has been known to replace them, IIRC. I think they even use a standard size. Not that you should HAVE to cough up the cash for a new battery immediately after spending a premium for those vents, but at least you know it is an option.  

It is the same company. Marinco bought Nicro and changed the packaging. Marinco also bought Promariner recently.  

On the subject of WD40 lubricant; I am one who listens and keeps fair a bit of company who know and study products even more than do I. As I recall, water displacement is not the strong suit of WD40 and better left to other lubricants. Most especially with electronics... Though its purpose is far reaching in too many areas to recall, it is neither rust resistor or water displacer. I have heard tell though how excellent it is to scent one's fingers when baiting for sturgeon since it is only fish oil with a strong, (annoying to me) perfume. Oiling things is not always advisable though it would seem harmless enough, (except where missiles might be concerned) as noted. There are many things such as sheaves where it is better to leave their cheeks unsoiled by oil which would later attract dirt if not migrate to contaminate the halyard lines. Bearings in certain motors and such where no lubricates are required and thus unwarranted. Loose oil on hinges will migrate and defeat varnishes as well as a host of other future projects like soldering and so on. The use of fish oil lubricants may lure a host of other unwanted critters as well since it is a high calorie scent. Then there is of course peppermint oil which detours said critters who detest even the slightest hint of it. It blocks a rat's sense of smell and makes them mostly blind since their noses are their prime director. Applied to dock lines it is an excellent detour-ant for a wide range of boarders.  

Woodvet said: ...WD40 lubricant...is only fish oil Click to expand...

Thanks Jim, Wish I had come here on the eve of my purchase and garnered a bit of the experiences people have already had. I think we echo in our history with Marinco. A friend helped design some retro fits for electronic buoys and was at once assured they are a great bunch of folks. I fully understand and believe that 'Defender' would make it right but they are over on the East coast. These are not easy batteries to replace. I believe we are suppose to substitute a Sanyo KR- 2000C for the N20590 (1.2 volt) and maybe it's not engineered for the same app since the number and letters diff. The main thing I gather is that the 20 at the beginning since it is the lasting quality and the volts are identical. But of course you once again run the gauntlet of not knowing the age of the replacement. Batteries must be fresh as produce. Thanks again Jim and I salute all of you who took time here to share...  

Not a Rosie picture you paint but now they don't sound so slick as before. There's a gun oil I was told that is the best. So why do sturgeons like it so much if it's a synthetic? "Because they're suckers?" :laugher  

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Yachting Monthly

• Digital edition

Sailing with solar power: A practical guide

• Duncan Kent
• November 13, 2020

The latest solar technology makes self-sufficient cruising much more achievable. Duncan Kent gives the lowdown on everything you need to get your boat sorted

SOLAR POWER ON BOARD

Solar power is fast becoming the most popular and economic method of keeping the batteries charged on a boat.

Particularly now that the efficiency of photovoltaic (PV) panels, charge controllers and batteries is improving every day.

Furthermore, the latest technology in regulators and charge controllers has brought about a noticeable increase in useable power output, so the problems of shading and non-alignment can be compensated for more easily.

Not only has PV equipment become more efficient and cost-effective, but many of the modern devices we want to use on a boat have become less power hungry.

This means it is now far easier to provide your entire yacht’s electrical needs, both 220Vac and 12/24Vdc, from natural energy resources – particularly solar power, even if you are planning on a fully electric boat .

Thinking carefully about how much power you need and how much your boat can accommodate is key to planning a solar array. Credit: Graham Snook

WHAT DO YOU NEED?

For instance, a boat with two new, good quality, deep-cycle house batteries of 100Ah each would supply 100Ah of energy to consume between charges, if you only use the recommended 50% of available charge between each charge cycle to protect the batteries.

From this you could run:

• a modern 12Vdc fridge (approx. 1.5Ah, or 36Ah over 24hrs),
• all LED lighting (say 20Ah per day),
• various small device chargers (20Ah)
• and a number of other items such as water pumps, TVs and stereos (25Ah/day)
• Totalling around 100Ah.
• For this you’d need 400W of solar capacity.

Of course, if you like to run a lot of AC devices off-grid such as hair dryers, microwaves, toasters and the like, then you’re going to need a DC/ AC inverter, which will take you to another level in power consumption terms.

But even then, with careful planning, solar could provide a large portion of the power you need before resorting to engine charging or a generator.

THE AVAILABLE SPACE

In practical terms, a modern 40ft monohull would have the space for around 1,200W of PV panels (cockpit arch, sprayhood top, deck), maybe 1,500W with the addition of a few portable panels for use at anchor.

The 1,200W of fixed position solar array could produce around 360Ah on a sunny summer’s day (zero shading) or more likely 250Ah on the average UK summer’s day.

So that’s enough for your 100Ah general DC consumption plus another 150Ah of AC consumption via the inverter.

Of course, to do this you’ll most likely need to increase your battery capacity to around 400-500Ah for maximum flexibility (you’ll need to store as much as possible during daylight hours), a typical figure for a 40-50ft offshore cruising yacht these days.

Get your solar charging right and you may never need to hook up to shore power

Typical daily inverter loads for a cruising yacht off grid might be:

• induction cooking plate (20min) 60Ah
• microwave (15min) 30Ah
• coffee maker (20mins) 25Ah
• hair dryer (5min) 15Ah
• laptop charger (2h) 10Ah
• or around 140Ah in total.

The trick is to monitor the batteries’ state of charge (SOC) at all times and vary your use of the inverter to suit.

For example, you might want to cook supper mid-afternoon, when solar is in abundance, and then reheat it in the evening when you want to eat it.

In some cases, when you’re cruising in warm climates such as the Med, you might end up with excess charge from your solar panels .

In this situation, many long-term cruisers devise a method of ‘dumping’ the extra energy by heating water for showers.

Do bear in mind if you’re planning to live aboard full time , then it’ll be a whole different story on cloudy days and during the winter, when inverter use might need to be knocked on the head entirely.

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POWER DISCREPANCIES

There’s often confusion as to how much power you can harvest from a solar installation.

A PV panel is nearly always advertised stating its theoretical peak output power (Pw).

But in reality, on a yacht where there are limited areas in which to mount them, they will more likely produce a maximum of 60% of their peak output if mounted horizontally, increasing to 80% if tilted towards the sun and regularly adjusted.

The latter is rarely achievable on a boat, however, as even at anchor it can swing through an arc of 180° in wind or tidal shifts .

Flexible panels can be mounted on sprayhoods or awnings to add power when it’s needed at anchor or in harbour

INSTALLATION

Having trawled through hundreds of ‘deals’ to get the best price on the most efficient panels you can afford you now need to know how to install them to best fulfill your energy generation needs.

The output, even from the highest quality photo-voltaic array, will only be as good as the installation itself.

So following our guidelines should ensure you extract every last drop of energy from your investment.

PANEL MOUNTING

Sailing boats are not the ideal structure on which to mount wide, flat PV panels.

So before you go ahead and purchase what looks like the biggest and best, take a few minutes to decide on exactly where you can mount them, as this will affect what size and type of panels you should buy.

In many cases the first choice would be on an arch, davits or gantry aft, especially if you already have, or plan to fit one.

Dinghy davits, particularly on multihulls, can support a huge solar capacity

These allow a solid metal framework to be constructed that will be strong enough to take the heavier, more productive rigid PV panels.

You can also build in some form of adjuster to the framework that will allow the panels to be orientated towards the sun for the best performance.

With luck (or careful planning) a gantry will also keep them aft of the boom, thereby eliminating loss of output caused by boom shading.

The next most popular position for mounting the panels is on a cockpit sprayhood or bimini, although this will often mean using the flexible or semi-flexible panels, which are generally less efficient than the rigid ones for the same area.

ELEVATED MOUNTING

Alternatively, there are kits available for mounting panels onto lifelines, which can allow their elevation to be manually adjusted to a certain degree.

Pole-mounted panels can be used for maximum adjustability

Finally, panels can be fitted directly onto the deck by either gluing them down using mastic or attaching them onto a rigid support frame.

Once again you will probably need to use semi-flexible panels – especially if the deck surface is curved.

Rigid, glass-coated panels will obviously not be suitable for deck mounting in an area that is frequently walked over.

Don’t be tempted to drill through the panels, even along the edges, as this will invalidate the warranty and possibly damage the panel.

With solid panels, the ability to adjust the angle can add significantly to output

It might seem obvious, but the key to an efficient system is to avoid shading wherever possible.

It’s no good fitting expensive, high-efficiency PVs right under the boom as they’ll perform little better than the cheaper types.

Saying that, in good quality panels each cell will be isolated from the next by a series of diodes (one-way electrical valves), so that if one cell is shaded at least it won’t drag down the other cells within the same panel.

Older panels often didn’t have these, so the slightest partial shading caused the output of the entire panel to cease.

OVERHEATING

Another important factor that is often ignored when installing the panels is that of overheating.

If a PV panel gets too hot, which is quite likely if mounted directly onto a flat surface without an air gap behind, its output will drop quite noticeably.

To allow for some air circulation behind the panels it’s best to apply mastic adhesive in numerous large dabs.

This is best achieved by placing wooden spacer strips between the dabs until the mastic has completely cured, after which the spacers can be removed.

You might need some form of trim around one or more of the outside edges, though, if they are positioned where sheets and other lines might get caught under them.

Raising the panels up will also help water to drain off and thereby helping to avoid possible delamination from sitting in water for too long.

CHARGE CONTROL

A PV module cannot supply an electrical device directly due to the changeability of the sunlight, which in turns varies the current it can produce.

Therefore, it has to be connected to a battery, which stores and smooths its output.

Whatever the size of your solar array you will need to fit a regulator, or charge controller as they are now more commonly known, to the system in order to control the output and to help extract as much power from the panels as possible.

There are two types of PV charge controller.

The older designs, called Pulse Width Modulation (PWM) types, were fairly basic voltage regulators and simply output volts at just above battery level.

The latest controllers use Multi Power Point Tracking (MPPT) technology and can accept much higher input voltages (up to 240Vdc).

MPPT controllers can be up to 30% more efficient as they use the peak output of the panels to charge the batteries, even compensating for partial shading.

BEWARE FAKE GEAR

If you buy online do be careful to ensure you’re getting what you pay for.

There are a huge number of fake MPPTs out there, which are simply the much cheaper PWM dressed up with fake labels.

It’s hard to tell which is which, but the old adage of ‘if it looks too good to be true, it usually is’ makes good sense.

MPPT controllers are usually bigger and heavier than PWMs, but if in doubt call or email the supplier to discuss the pros and cons of their kit before buying.

If they’re not happy to chat and advise you then I would steer clear of their gear.

Some good MPPTs are made in China, but unless they have a UK supplier, I wouldn’t bother with them as you’ll have no follow-up advice.

To calculate what size controller you need simply divide the panel’s peak power in Watts (Wp) by the battery voltage, which will give you the maximum current (Amps) they could theoretically supply.

For example 240W/12V = 20A. Although it’s unlikely you’ll ever get near the peak output from any PV panel, it’s best to go for the maximum possible.

Induction cooking is now a reality on board, even without shore power

PV panels come with a short length of cable, usually around 1m long.

Some are supplied with MC4 connectors already attached but most only provide bare wires.

The latter can be easily extended using proper waterproof connections but thought must be given as to the current rating and voltage drop (usually max 3%) for the size of cable you intend to use.

If in doubt, bigger is better!

Panels can sometimes be ordered with the wiring on the back so that the cable can go straight below deck through a hole under the panel.

You may need to fit extra battery capacity if you want to run an inverter from solar charging

SERIES OR PARALLEL?

A commonly asked question is ‘should I wire my PV panels in series or in parallel?’

The simple answer is, if there’s any danger of frequent shading to one or more of the panels then install them in parallel.

If wired in series the shading of a single panel will drag down the output from all of the others in the same series.

PARALLEL IS PREFERRED

Most commonly, multiple panels are wired together in parallel to a single charge controller, with diodes protecting each panel from discharging the others should one become partially shaded.

With the advent of MPPT controllers, however, there can sometimes be a benefit to wiring two or more identical panels into a series bank, thereby presenting a higher voltage to the controller.

It’s worth noting that, like batteries, wiring PV panels in series increases the voltage only – the current capacity of the array remains the same as for a single panel.

‘Where’s the benefit of wiring them in series then?’ you might ask.

Well, the higher the voltage fed into the MPPT, the more consistent it will be with its output, which could, in some cases, prove more efficient than a parallel installation with PWM controllers.

It’s also likely to be necessary if you have a 24V domestic system.

SERIES WIRING

Series wiring is usually only done when the cable runs are long, as it helps negate the voltage drop caused by the resistance of the cable.

While a decent controller will have no problem handling the output from four or even five panels wired in series, it is often inappropriate for sailing yachts as shading just one of the panels will reduce the output of the entire series array.

If you need to do so in order to reduce cable runs then it’s best to split the panels between each side of the boat – a series bank on each side.

If you do this, then you would ideally fit a separate controller to each series PV bank and then connect their outputs together in parallel to the battery bank.

Note, however, that panels wired in series must all be the same types with an equal number of cells per panel.

Furthermore, the charge controller needs to be sized for the total of all panel voltages added together and the current rating of one individual panel.

Differently rated panels can be connected together in parallel but only if each panel has its own controller.

The outputs of the individual controllers can then be joined together to go to the battery bank.

BATTERY BANK QUESTION

Another frequently asked question is ‘Can I connect another charging source to the battery bank while the solar array is charging?’

The answer is yes.

Any decent PV controller will be protected against feedback from other charging sources.

Think carefully about where shade from mast, boom and rigging will fall. Credit: Graham Snook Photography

CABLE SIZE AND CONNECTORS

A frequent cause of reduced output from PV arrays is wiring that is too small.

The resistance of a wire conductor increases in direct proportion to its cross-sectional area, so go as big as is practicable for the least cable loss.

Each panel should be supplied with the correctly sized cables for its own maximum output.

But if you’re combining panels, either in parallel or in series, you will clearly need to rate the single feed cable to suit the maximum current available at theoretical peak solar output and to minimise voltage drop.

Likewise, the cable from the controller to the batteries should be sized to suit the controller’s maximum output current and protected with a fuse.

For outside it’s important to use exterior grade cable, which is double- insulated and UV-proof.

WEATHERPROOF CONNECTORS

And wherever possible use compatible weatherproof connectors (usually MC4) to those found on the panels rather than cutting off the plugs and hard-wiring them.

Field- assembly MC4 plugs are available, so you don’t have to drill large holes in the decks or bulkheads when feeding the cables through.

When joining more than one panel together try to use the approved multiway connectors; not only do they keep the wiring neat and tidy, but they also offer a greater contact area than budget terminal blocks.

If you have to use screw-type connectors make sure to fit proper ferrules to the wire first to avoid any stray wires in the multistrand shorting across the terminals.

When feeding a cable from above to below deck, try to go through an upright bulkhead where possible to minimise ‘pooling’ of water around the access hole.

Also, use a proper watertight deck seal that matches the cable you’re using.

If drilling through a cored deck you need to drill a larger hole first, fill it with epoxy resin and then drill the required size hole through the epoxy to ensure no water gets into the deck core.

Ideally, the charge controller should be mounted no further than 2m from the battery bank.

If you need to go further, you’ll require larger cabling to reduce the voltage drop.

A generous solar array will keep you self- sufficient indefinitely. Credit: Graham Snook Photography

CONTROLLER LOAD TERMINALS

There is often confusion over the ‘load’ output of a charge controller (often depicted by a light bulb) and what can safely be connected to these terminals.

Rarely explained in the manual, the load terminals should be pretty much ignored in a marine installation as the output on these terminals is usually very limited (10A max).

Some attach an LED light to them to indicate the controller is operating, but all your usual electrical loads should remain connected to the batteries with the battery terminals on the controller connected directly to that battery bank via a fuse.

It is possible, though, to control a high-current switching relay in certain conditions.

Parallel installation is more resilient to shading, but a series installation will increase peak charging outputs. A combination of the two offers some of the benefit of both

CIRCUIT MONITORING

Unlike most cheap PWMs, the majority of good quality MPPT charge controllers come with an alphanumeric LCD screen to let you know what is going on.

This can either be a remote display or simply one on the front of the box.

It’s obviously a lot better to have a proper numerical display than to rely on a few flashing LEDs to tell you when something’s not right.

So if your chosen controller doesn’t have one be sure to fit a battery monitor (the shunt type) into your solar circuit between the controller and the batteries.

It doesn’t have to be a very ‘smart’ monitor, just one that can display the voltage and current being supplied by the panels.

For smartphone addicts there are several wifi apps that will do the job remotely on your phone or tablet.

DEVICE PROTECTION

All good quality PV panels feature built-in diode protection between each cell to prevent a shaded cell from dragging down the productive ones.

In addition, there will be internal blocking diodes on the final output to protect the panel from polarity reversal and to ensure that the batteries can’t discharge back into the panel during the night.

The latter can be added externally, the former can’t, so check before you buy.

A fuse, rated just above the maximum current available, should be fitted between each panel and the charge controller.

Another fuse should then be installed between the charge controller’s output and the batteries.

In the case of multiple arrays, this second fuse will be rated higher than the individual panel fuses and should match the maximum current rating of the cable.

With this protection installed other charging devices can be connected in parallel at the battery, meaning the solar can be left connected even when you are hooked up to shore power and the battery charger is operating.

In some circumstances, however, this arrangement can affect the sensing of the battery by the charger, causing it to fall back into float mode.

If this becomes apparent it can be overcome by installing a manual/auto switch to disconnect the solar array when on shore power.

Check the flex of the solar panel is sufficient for your deck

EXCESS POWER DUMPING

A solar charge controller works by disconnecting the supply from the PV panels when the batteries are fully charged.

But for some full-time liveaboards in sunny climates that can be considered a waste, when the excess power could be put to good use – heating water, say.

This is commonly done using an inverter to supply AC power to the heating element.

Alternatively, you can now buy a 12Vdc element for your calorifier (hot water tank) and supply this directly from your battery bank.

Both of these methods would require a voltage sensitive relay (VSR) to disconnect the element should the battery voltage drop below a pre-set level.

Don’t expect boiling hot water, as there will probably only be enough spare power to take the chill off it before your battery bank reaches its lower threshold voltage.

A 600W/12V element will draw some 50A, from the batteries, whereas a 1kW AC element run through an inverter will need close to 100A.

A small, semi-flexible panel will be sufficient for keeping batteries trickle charged, but not for heavy use

RIGID, FLEXIBLE, OR SEMI FLEXIBLE?

Despite massive recent improvements in semi-flexible panels in recent years, the solid glass panels still offer a higher power density.

That said, they are heavier, more awkward to mount and can’t be walked on, so unless you have a dedicated gantry aft, you’re better off choosing the more rugged semi-flexibles.

Modules incorporating monocrystalline cells also have a better output than those with polycrystalline cells (that’s cells made from a single slice of silicon as opposed to layers of smaller pieces).

Output voltage also depends on the number of cells on the panel.

In the past this has commonly been 32, but now some 36 and even 40 cell panels are available.

That said, they’re larger, of course, so an array of interconnected smaller panels might be a better solution.

Module efficiency is now more often around the 20% mark, as opposed to 12-15% for older models and semi- flexible (up to 20° bend) are usually better than flexible (up to 180° bend).

A rigid panel is more efficient, but less robust

There are a huge number of panels on the market, but many use the same cells.

Sunpower Maxeon cells are exceptionally good, as are the Panasonic HIT range and LG, but they are pricey.

If the maker is offering a 25-year guarantee instead of a 3-5 year one, you can be pretty confident they’re good.

When it comes to charge controllers it’s definitely worth paying a little more for a decent MPPT.

A cheap PWM might be okay just to keep a small starter battery charged with a 30W panel, but the MPPT will give you much more when it comes to heavy service.

Victron are probably top of the range, while cheaper brands like MakeSkyBlue and EPever are also good value – but treat imports of unclear origin with care.

ABOUT THE AUTHOR

Duncan Kent has been evaluating and reviewing yachts and marine equipment for the past 30 years

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Get Air Down There: How To Improve Ventilation On Any Boat

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Good ventilation inside your boat is a must for comfort and safety. Here's how to get the cooling breeze flowing.

A wind chute installed over a hatch can help channel airflow below and can even keep light rain out if positioned correctly. (Photos: Fank Lanier)

Nothing enhances the quality of life belowdecks during the heat of summer, or when cruising hotter latitudes, like plenty of cool, fresh air. Good ventilation provides a multitude of benefits including preventing odors, condensation, and mold growth as well as eliminating minor carbon monoxide buildup and its negative effects on crew health (such as headaches and seasickness). Here's a look at ventilation basics and how to make them work for you.

Passive Or Active

There are two types of ventilation systems : passive and active. Passive systems rely on the wind blowing over them to move air belowdecks. They either direct air inside or exhaust it (depending on their type and orientation to the wind). Examples of passive vents include traditional cowl vents, clamshell or scoop vents, louvered hatch boards, and low-profile discs (aka mushroom vents).

Passive vents work best when installed in opposing pairs. While they can move a surprising amount of air on a breezy day, they don't perform well on days with little or no wind.

A solar-powered mushroom vent is ­convenient and easy to install.

Active systems are typically mushroom vents outfitted with a small electric fan installed in the vent body. Some are powered by your boat's 12V DC system; however, most are solar-powered. Many of the solar-powered units contain a rechargeable battery (to facilitate nighttime operation) as well as interchangeable fan blades, which allows them to be used as either an intake or an exhaust.

Ventilation Basics

Efficient airflow requires not only an intake, but also an exhaust. A single intake can't force air into a boat against pressure any better than a single exhaust can remove it against a vacuum.

Assuming a boat is oriented head-into-the-wind (as is typical while at anchor or on a mooring), it's pretty intuitive that opening a forward-facing hatch channels air belowdecks, much like an air ram. Conversely, an open companionway door or aft-facing hatch acts as an extractor, pulling air from belowdecks as the wind passes over it.

Adding a wind chute to your hatch provides even greater funneling ability. The same goes for portlight scoops, which help deflect those cooling breezes down below through vertical portlights.

If your boat has limited or no portlights, consider swapping out some of the “deadlights” (non-opening portlights). Portlights (which open to allow airflow) come in a wide variety of shapes, sizes, and frame materials (e.g., plastic, bronze, aluminum, stainless steel). As such, it is typically easy to find units to replace existing deadlights. When buying portlights, be sure to match the material of the new units to the remaining deadlights or existing boat hardware to prevent the nautical equivalent of an eyesore. Installing portlights , exhaust vents, or even additional hatches over cooking areas can also make a big difference in air quality belowdecks.

Boats at the dock face additional ventilation challenges as they can't orient themselves to the wind. Wind chutes can be repositioned to the sides or rear of a hatch to help funnel air belowdecks, while some traditional hatches are hinged or pinned so that they can be opened to face any of their four sides (a boon in this situation).

Other airflow challenges occur during rainy or stormy weather, which can prevent boats from leaving hatches and portlights open while in port or underway. A tarp or canvas cover rigged over a partially opened hatch keeps rain out and provides ventilation, although the airflow will be less than that of a fully opened hatch or one using a wind chute (which typically can't be used in conjunction with a tarp). The best solution here is a unit that combines the protection of a hatch awning and the functionality of a low-profile wind scoop.

How Much Is Enough?

A well-designed ventilation system should exchange the air belowdecks roughly once every hour. Let's say you have a mid-sized boat with an interior volume of around 1,400 cubic feet. Airflow ratings for passive vents range from 350 to 600 cubic feet per minute (cfm). Intake volume should equal output, so based on the above we would need a minimum of four similar sized vents (two intake, two exhaust) to provide adequate ventilation.

If using two active vents, they should be matched with two passive vents. If four passive vents are installed, they will automatically adapt to intake or exhaust mode as needed (with the exception of improperly aligned cowl vents).

Vents should be arranged to provide as much cross flow inside the cabin as possible. Passive vents should be mounted in pairs at opposite ends of the boat (to the extent possible) with one facing forward and the other facing aft, which provides an intake and exhaust, regardless of wind direction. A combination of passive and active vents provides the same effect with varying wind directions (or in the case of no wind at all).

More 'Cool' Ideas To Beat The Heat

• Use awnings, side curtains, and biminis to provide shade and reduce temperatures belowdecks during the heat of the day.
• Replace heat-producing halogen and incandescent bulbs or fixtures with cool-running LEDs.
• Avoid cooking belowdecks during the heat of the day. Plan around the heat by cooking galley meals in the morning or later in the afternoon while grilling or serving cold meal items for lunch. Barbecuing abovedecks will also keep the cabin cooler at night.
• For boats without an air conditioner, anchor out or take a mooring ball.
• End the day's run early enough so the engine won't be radiating heat well into the night.

Move It Around

While getting fresh air belowdecks is important, it's only half of the ventilation battle. In our example above, four vents may technically provide enough fresh air, however the interior will be broken up into separate cabins or compartments that can restrict airflow throughout the vessel. So simply installing the correct size and number of vents may not be enough to get the ventilation job done. Equally important is moving that fresh air into all the low ventilation spaces.

Drawers, hanging lockers, and other closed storage compartments will benefit from louvered doors or vent grilles. Just remember these spaces require a way for air to both enter and exit in order to provide good cross-ventilation.

Cabins and heads should also have some kind of ventilation installed, particularly if they can be closed off from the rest of the boat. For these and other such living areas, nothing improves ventilation like a few well-placed electric cabin fans . They make a hot bunk bearable, remove heat from the galley, and help reduce odors and keep moisture down in the head/shower area. Unlike the noisy, power-hungry units of yesteryear, today's fans are both quiet and energy-efficient.

My recommendation is that every bunk have a dedicated fan — two if needed due to size. It's almost as if just the soft whirring sound of the fan alone makes the bunk feel cooler. Although many boats suffer from less-than-ideal ventilation, improvements can be made to most any vessel fairly easily and at minimal expense. The effort spent constructing a hatch hood or installing a few fans will pay cool dividends for years to come.

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Frank Lanier

Contributing Editor, BoatUS Magazine

Capt. Frank Lanier is a SAMS Accredited Marine Surveyor with more than 40 years of experience in the marine and diving industries. He’s also an author, public speaker, and multiple award-winning journalist whose articles on boat maintenance, repair, and seamanship appear regularly in numerous marine publications worldwide. He can be reached via his YouTube channel “Everything Boats with Capt. Frank Lanier” and website captfklanier.com.

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Top 3 Best Solar Panels For Sailboats

Last Updated by

Daniel Wade

June 15, 2022

Choosing whether or not to install solar panels on your sailboat is a big decision. They are not exactly cheap, though they can start to pay themselves off pretty quickly.

This article is going to cover not only why you might want to use solar panels but all the benefits they provide. You will also find a helpful guide on which solar panels would be best for you and your budget. Hopefully, by the end, you will feel confident in your decision to install solar panels on your sailboat and even have an idea of which ones you might like.

Table of contents

Are solar panels on sailboats necessary?

Whether or not you should be installing solar panels on your boat is a matter of choice, not out of necessity. Sailboats get their power from the wind, by harnassing it in their sail. So if you plan to be sailing for the afternoon you probably don’t need solar panels.

You could charge a battery pack from the marina and that will probably see you through several trips. The problems only really start to arise if you are planning to be on your sailboat for longer periods, or even permanently. If you plan to live on your sailboat year-round, even if you spend 80% of it in a marina, you would be better off with some solar panels. Even if it is just as a backup source of power.

Are solar panels on boats safe?

Solar panels are generally pretty safe. They have no moving parts and typically have a very strong protective cover over them so you never come in contact with the electrics themself. So, as a source of power, they are generally pretty safe. The only time they may become unsafe is if they are badly damaged.

Solar panels are often covered by glass plating that keeps them safe. It also helps them absorb sunlight and warmth. This is great, except when the glass breaks. If the glass protective cover on your solar panels should crack and splinter you are at risk of serious injury from sharp shards of glass. Not only is the glass itself dangerous at this point, so are the electronic components inside. They have powerful currents running through them, and if you come in contact with them you may be in for a shock.

Furthermore, if these electronics get wet they can become deadly. Electricity and water do not mix well at all. Being as you are on a sailboat, at sea, the chances of them getting wet is very high. Luckily, the chances of them breaking in the first place are slim to none. The only real way they would break, besides vandalism, is by debris hitting them during a bad storm. There is not often debris at sea, so this shouldn’t be too much of a problem.

What are the benefits of having solar panels on a sailboat?

There are so many great benefits of having solar panels on a sailboat. They can be a lifesaver if you find yourself at sea for a long time. There benefits range from trivial comforts to being the difference between life and death. Here are some of the benefits you might not have considered about having solar panels installed on your sailboat.

Money-saving

Solar panels are not cheap, it is far cheaper to just run a generator or charge your batteries from the marina the whole time. At least, it is in the short term. Over time, it can start to become very expensive. With solar panels, you are looking at a big initial cost (the solar panels themself) and then it’s smooth sailing. You don’t need to pay for power again. Solar panels last for about 40 years before they start to become too inefficient at producing power. The cost of a few solar panels upfront compared to 40 years of marina fees and gasoline for a generator is the financially savvy move.

Emergency power

If you find yourself at sea, the wind dies down (or becomes too strong), and you find yourself stuck bobbing around waiting for more favorable conditions you may run into trouble. Depending on how long you are out there, you may find yourself with dead electronics. Be it a satellite phone, radio, or secondary engine (depending on the boat). Having a set of solar panels and a power bank can be a genuine lifesaver in these situations.

Comfort amenities

Whether you are day sailing or making a week-long voyage, having access to the comforts in life can make the whole journey so much more enjoyable. The amenities may not be available to you without having a constant source of power at sea. Having access to a kettle, tv, videogame system, radio or microwave oven may be the only thing keeping you going at rougher times. As exciting as sailing can be, when you aren’t sailing and are just bobbing around it can be quite dull. The sea is beautiful, but there is only so much time you can spend looking at the water before you miss the comforts of land. With solar panels, you can bring those comforts with you.

Eco-friendly

There are only two alternatives to solar panels. A gasoline generator, and taking power from the grid. Neither of these is good for the environment. Luckily, solar panels are a great third option. Solar panels are completely eco-friendly and are great for the environment. This is not just great for the earth, and your conscience, but for the journey itself. If you are running a gasoline generator at sea you are going to be listening to it thrumming away and smell the burning gasoline. Wouldnt you prefer silence and nothing but the smell of the sea breeze?

How much do solar panels cost?

How much solar panels cost is almost entirely tied into both their voltage/wattage and whether or not they are portable panels. Portable solar panels are great for people who don’t spend a lot of time on their boat or are happy enough living off the marina’s power grid. Permanent solar panels, the kind that may need to professionally installed, can end up costing far more. They are also likely to be far superior and you can pretty much forget about them once they are installed.

Portable solar panels will cost just a few hundred dollars each. You will need a few to be sustainable, but that’s not going to be much of a problem. These portable solar panels can just be rolled out on the deck of your boat, weighed down, and then hooked up to a battery pack. The battery itself here is going to be the most expensive part of the whole set up. A decent-sized battery could set you back a $1000. But, when charged fully it will last days. Even with constant use.

Permanently installed solar panels can cost one or two thousand dollars in some cases. The advantage here though is once they are installed that’s it, you can forget about them. You don’t have to put them up, take them down, and find somewhere to stow them every time they need using. They too will need to be hooked up to a battery, the battery is still only going to cost you $1000. If you are installing permanent solar panels because you plan to be making long voyages, it is ideal to have two or perhaps even three large batteries hooked up to your boat. One to run off, one or two for emergencies.

How do I maintain my solar panels?

Solar panels, unlike gasoline generators, are generally pretty easy to maintain. They have no moving parts and are thus pretty self-sufficient. They don’t need taking apart and they last as long as 40 years. That being said, if they do break they need repairing as soon as possible. The exposed electrics can be deadly when water is thrown into the mix. Which, on a boat, is almost always. The glass cover will need replacing and the electronics inside may need repairing, though not always. Don’t ever attempt to do this yourself unless you are experienced at making these repairs. The cost of hiring someone to do it for you is preferable to being dead. Solar panels have very powerful electric currents, that when in contact with water and yourself can be fatal. As mentioned above, these panels rarely break so you will likely not ever run into this problem. If you do, hire a contractor.

Do my solar panels need cleaning?

Solar panels work by converting the light and heat of the sun into useable power. The process itself is rather complicated but the results are simple to understand. That being said, there are some reasons that your solar panels will stop working as effectively. They all revolve around a lack of sunlight. It could be because it is night time. It could be because it is very cloudy. Or, it could be because they are dirty. If solar panels become too dusty, dirty, and become too covered in grime they stop operating at maximum efficiency. This is not as much of a problem at sea, the sea spray stops dust settling. The biggest thing you will need to clean off your solar panels is salt build-up and slime. This is easy enough to do with some warm soapy water. Freshwater, not seawater. You want to be removing as much salt as possible. Salt is corrosive to electronics, so removing it is important. Never clean your solar panels using pressure washers as they can crack the glass.

Which are the best solar panels for sailing?

There are so many options on the market at various price points. Here are three very different options that will all make good choices, depending on your needs. It is important to consider not just price but power output. Spending a lot of money on solar panels now might not feel ideal, but it is the most cost-effective decision.

1. Renogy Starter Kit

This starter kit is going to be perfect for installing on almost any sized boat. There are four solar panels, each can be fitted permanently to the boat. They can be mounted (and unmounted) easily, for your convenience. They do require a flat surface, but they are small enough that that likely won’t be too much of a problem. This starter kit is very middle of the pack price-wise but should provide enough power for a small to medium-sized vessel easily. It is also possible to buy extra panels individually should you need them.

Wattage: 400/4 (100 per panel)

2. Nature Power Rigid

The nature power rigid is a large, powerful, single solar panel. If you are looking for the right panels to power your entire boat comfortably, these are the ones for you. They are very large so they will need a large flat surface area. alternatively, they can be hung vertically from rails. This is an inefficient way of using them, so you would need to buy more this way. Nature power makes various solar panels so you could find some smaller ones of the same brand to supplement it. This one is not so easy to install, you might need to hire someone to install it for you.

Wattage: 165

3. Nature Power Monocrystalline

Nature power makes a portable solar panel that fits inside a special briefcase. It is perfect for stowing away easily and only taking it out when it is needed. It is decently powerful considering its portable, but there is the inconvenience factor of having to set it up each time. If you planned to buy the nature power rigid, buying one of these portable panels might be ideal for supplementing your power supply when it is especially sunny. Though, it may be cheaper for you to just fit more of the Nature Power Rigids.

Wattage: 120

Hopefully, you now have a good idea about whether solar panels would be right for you and your sailboat. Sailing is great, but the lack of power at sea can be dreadfully boring. Luckily, there are so many great options available on the market. Not just the ones mentioned above. Buying a solar panel is an investment, the initial cost is minor compared to the steady return from all the savings you will make.

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I've personally had thousands of questions about sailing and sailboats over the years. As I learn and experience sailing, and the community, I share the answers that work and make sense to me, here on Life of Sailing.

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Practical Boat Owner

• Digital edition

Banish winter damp: install a solar-powered vent

• Colin Haines
• February 29, 2024

Ten years ago, Colin Haines installed a solar-powered vent on his boat. He shares the results and if it still keeps his boat truly dry

Solar-powered shed ventilator installed on the washboard keeps Colin Haines's boat interior dry over winter. Credit: Colin Haines Credit: Colin Haines

Mains electricity-powered dehumidifiers, are effective but expensive and cost money to run. They also assume that some ‘helpful’ person does not unplug the shore power supply.

I don’t have my boat lifted out of the water during the winter for several reasons.

Stating the obvious, sea water is warmer than sub-zero nights that freeze an entire boat.

Therefore, if there is any damp, the last place condensation will occur is in the warmer bilges .

Also, when stormy winds blow, the boat can heel rather than be held rigidly by the localised pressure points of the cradle or props holding it upright.

Atmospheric humidity is less when the winter sun is shining than during grey, overcast days.

Ten years ago I exploited this fact by installing a solar-powered ventilation fan in the washboard to draw dry air through the boat.

Continues below…

Boat condensation: one sailor’s solution to keep your boat dry

Many boats suffer from water droplets forming on cold windows as a result of hot air or steam becoming cool…

Where is the best place to install a boat vent?

Where is the most effective place to install a boat vent? Surveyor Ben Sutcliffe-Davies has some tips

How to remove mouldy stains from interior woodwork – Ask the experts

Kevin Woods from Dublin writes: “I have a 1991 Feeling 286 Special. Some of its timber interior is stained by…

How do I get rid of a mystery boat smell?

PBO reader Constantin Demner is struggling to get rid of a strange boat smell, which is permeating her clothing and…

Her marina mooring holds her stern facing due south. When the winter sun is at its highest, and humidity the lowest, the solar-powered fan draws the dry air through the boat.

Humidity rises as the sun’s power weakens when it begins to move towards the end of the day and, with less solar power, the fan slows down and stops when the sun sets before humidity rises even further.

On dull days it draws very little damp air into the boat.

As a result, the boat’s interior is always dry when I visit her during the winter to do odd jobs while the batteries are being recharged.

The moisture from my breath has long since gone when I return two months later.

More importantly, with the shore power unplugged for the rest of the time, I don’t have to worry about another boat with faulty electrics turning up and galvanically eroding the saildrive.

Nor does it cost a single penny to keep the interior bone dry.

The fan is designed for shed roofs and when rain is driven against it, no water enters the boat.

Ten years after installing the solar-powered vent fan (they’re available for around £30- £40 nowadays), it’s clear the manufacturer chose to make it from suitably durable materials.

I commend this parsimonious approach to keeping the cabin dry to anybody with a north-south orientated berth, or one that allows the stern to face within perhaps 15° of due south and does not have any problems with shadows.

Enjoy reading Banish winter damp: install a solar-powered vent?

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Simple Tips to Improve Boat Ventilation

As ventilation experts explored ways to make indoor spaces safer during the COVID-19 pandemic, we became curious about ventilation in our boats. What products and practices ensure that we maximize the volume of air exchange belowdecks, as measured in cubic feet per hour (CFH)?

While this exchange of fresh air provides direct benefit to our health, it also provides an indirect benefit by preventing the growth of mold and mildew. Generally, to successfully combat mold in any given space you need at least one air change per hour, and for boats from 25-40 feet that is about 700-1800 CFH. Good ventilation also helps remove warm moist air created during cooking that can condense on the inside of the cabin—creating the moist environment that mold loves.

We’ve looked at ventilation dozens of time over the past 10 years, but most of those previous studies focused on a particular product group—fans, hatches, vents, opening portlights, or air-conditioning systems. In the September 2020 issue we narrow the focus to passive ventilation—cowl vents, dorades, hatches, “wind scoops,” and other ways to boost the exchange of air on board without any mechanical assistance.

Boats are relatively small spaces, and you’d think that it would be easy to keep interior air fresh with a few ports and hatches. As it turns out, where you install your inlet and exhaust vents is as important as the kind of vent (hatch, port, or vent) you use.

Most sailors know that wind blowing across a uniformly smooth surface such as the leeward side of a well-trimmed sail creates a region of reduced pressure. Just as we can use the resulting suction on the leeward side of a sail to pull the boat forward, we can use pressure differentials in the air surrounding the cabin to maximize the ventilation belowdeck.

Understanding the pressure differentials created by the flow of wind over our boat’s deck is vital to the success of any passive ventilation scheme. Mapping this flow (see the below image), helps explain why some areas of the boat seem stuffier than others. It also explains why passive ventilation methods did so poorly in our testing.

Your boat’s cabin trunk has a number of pressure zones, and these zones change depending on the wind direction. At anchor, the front of the cabin trunk is an area of high pressure, and this pressure reduces slightly as you move aft. The pressure differential between locations along the cabin top on depends many factors, including the shape of the cabin and any items on deck that might interfere with flow. In general, the pressure is lowest just behind the front edge of the cabin trunk, slowly rising to neutral pressure as you move aft—depending on the extent of turbulence caused at the front of the cabin trunk or by other interruptions in the smooth surface that would disrupt the flow of wind.

The companionway area has the lowest pressure. Open a hole anywhere forward and air will be sucked out the companionway. In a breeze, the pressure differential is usually so great that air will push out through gaps in the weatherstripping, escaping even if the companionway hatch closed.

Maximizing air-flow through cowl vents is trickier than it might seem. Air-flow can be interrupted not only by insufficient pressure differential, but also by turbulence. The vertical cabin-sides, dinghies stored on deck, masts, changes in wind direction, and even other cowls can dramatically reduce the amount of wind that reaches the cowl.

The most complicated case is when you keep the boat at a dock with everything buttoned up. The wind can blow from any direction, and depending on the amount of protection afforded by the harbor and neighboring boats, the wind will be light most of the time.

Bottom line: Although many passive vents are rated by CFH, these ratings don’t tell the whole story. Flow will vary greatly depending on the location of the vent, and since the rated CFH is typically based on a 10 knot breeze, the rating won’t give a clear picture of air flow when your boat is at the dock. At many marinas around the U.S., the true wind at deck level is less than 5 knots most of the time.

For more on ventilation, see the September 2020 issue of Practical Sailor. If defeating mildew is your main objective, our eBook The Mildew-free Boat will cover everything you need. If boosting breeze belowdecks is your primary aim, the following related Practical Sailor tests will help you improve the flow of air down below.

Ventilation Can be Improved on Any Boat

Deck Vents: Nicros Water Trap and Plastimos Cool n Dry are Clever and Effective

Fabric Hatch Vents: The Breeze Booster Outdraws Windscoop

How to Measure Boat Humidity: Psychrometric Charts Do it Right

Onboard Amenities: Endurance test of 12-volt Fans Wraps Up

Cabin Fan Test Returns

Cabin Fan Test: Hella, Caframo Blow Best Breeze for the Buck

RELATED ARTICLES MORE FROM AUTHOR

Because my last boat (a J/24) stunk of mold, I came up with a solution for my current 38’ sloop that I can recommend without hesitation. I’ve installed an inexpensive modular ‘daisy chain’ of DC USB ‘computer’ fans underneath and behind the boat’s beds, cabinets, and seating areas. The hidden & silent fans are UL Listed and connected to each other via USB-to-USB extension cables (with inline fuse). The fans are each rated to run for 10 years and I’ve run them continuously for the past 5 years with no problems. The fans are all oriented in harmony to increase airflow circulation belowdecks…in and around all of the many spaces where humid air tends to stagnate, and (combined with the Practical Sailor recommended Eva-Dry 2200 dehumidifier) have completely eliminated ‘that boat smell’ caused by mold, etc.. The fans are each rated to run for 10 years and move 64 cubic feet per minute of air, and entire system cost me less than $100 on Amazon. I can recommend it without hesitation.

In light air, no fetch, anchor off the stern. Leave the dodger and Bimini up. Open all hatches, put up the mosquito netting, and the dodger / Bimini act like a BIG wind scoop. The breeze is great and is especially welcome below when the bugs on deck are wrecking your romantic dinner.

We’ve been very pleased with the performance of Karecel fans, which are small and recharge with a USB plug. They have 3 speeds and are nearly silent. We got them from Amazon and the come in black or white. For the price ($18), you can’t beat them.

Your comment above: “The companionway area has the lowest pressure”, conflicts with your diagram showing average pressure at the companionway. Where’s the truth?

If there is one area that needs intensive product improvement it’s marine ventilation! solar vent fans havent been properly updated since the 80’s (and the prices are utterly unjustifiable). There are of course beautiful and justifiably pricey scoops etc in Bronze etc but most of the plastic and resin originated items just don’t address the need for forced air and energy sources most available to small to medium size yachts….Solar solar solar! modular design! micro connectors to discreetly run solar power to various fittings….scoops that really seal, fans that blow and are efficient actually last 5 years! no lousy rusting parts! The biggest culprits are the companies managing the few solar fan products out there….Someone needs to take the challenge and design a growing array of good (affordable) devices to render the interior of yachts habitable! W ith plastic casting and current solar technology there is no excuse for the scarcity of effective devices!

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Solar Vent on a head hatch.

• Thread starter Cat36Amoore
• Start date Jul 22, 2020
• Forums for All Owners
• Ask All Sailors

Cat36Amoore

I would like to install a solar vent on my head hatch. Is it possible to drill the hole using a hole saw with out cracking the lenses? I have a new hole saw bit. Plan on masking tape the lenses and going slowly with the drill. Does anybody have any tips?  

Yes. I’ve done it. No problem  

Mark Maulden

Drill backwards to start with little pressure  

Mark Maulden said: Drill backwards to start with little pressure Click to expand

markwbird said: Yes. I’ve done it. No problem Click to expand

How did it go? I've been thinking of adding a second one. The head hatch would be about right. A PO installed one thru the forward hatch and it came out fine, although it's old and should be replaced.  

And obviously, drill from both sides.  

A bit off-thread, but wondering: what is people's long-term satisfaction level with solar vents? When I bought my boat it had two, in both main overhead hatches. They were ugly and no longer worked. I replaced the NiCd batteries in them, still nothing. I read up on them, there was no longer any support from the manufacturer, and folks had gone to great lengths refurbishing them with quite a dose of MacGyver. I ended up replacing the Lewmar hatch lids at a cost of about $900. Now I have beautiful, clear hatch lids! So, my long-term satisfaction with them is very low. I would be more interested in servos that would keep my Dorade cowls pointed into the wind! (We're on a mooring and the direction of the boat is determined by the current in the river, not the wind.)  

Speaking for myself, it's the only cabin ventilation we have when we close her up. And it's still hot whenever we come out. I run a tiny dehumidifier that doesn't help. Also the refrigeration runs .  

Justin_NSA said: Speaking for myself, it's the only cabin ventilation we have when we close her up. And it's still hot whenever we come out. I run a tiny dehumidifier that doesn't help. Also the refrigeration runs . Click to expand

jviss said: Are the fridge and dehumidifier condensers exhausted to the outside air, or into the cabin? I'm fortunate that I have four Dorades that work pretty well. Click to expand

Only if you never venture offshore. Borrowed an h34 which had some vents installed by the front cabin hatch and we had some unsettled weather approaching Cape May and buried the bow under a swell and had Niagara Falls inside the cabin.  

Benny17441 said: Only if you never venture offshore. Borrowed an h34 which had some vents installed by the front cabin hatch and we had some unsettled weather approaching Cape May and buried the bow under a swell and had Niagara Falls inside the cabin. Click to expand

Ron20324 said: Click to expand

Ron20324 said: .... save the slug for Justin, he has some holes he needs to cover Click to expand

jviss said: A bit off-thread, but wondering: what is people's long-term satisfaction level with solar vents? When I bought my boat it had two, in both main overhead hatches. They were ugly and no longer worked. I replaced the NiCd batteries in them, still nothing. I read up on them, there was no longer any support from the manufacturer, and folks had gone to great lengths refurbishing them with quite a dose of MacGyver. I ended up replacing the Lewmar hatch lids at a cost of about $900. Now I have beautiful, clear hatch lids! So, my long-term satisfaction with them is very low. I would be more interested in servos that would keep my Dorade cowls pointed into the wind! (We're on a mooring and the direction of the boat is determined by the current in the river, not the wind.) Click to expand

I got a couple on Amazon, work very well, and were pretty inexpensive.  

I’ve had 2 Nicro solar day and night fans, first one was original to my ‘82 boat, still going strong when I replaced it 2 years ago with a newer model (early version could not close, new one does). New one works perfectly but I put a higher capacity battery in it (mine sits about 2 feet below the boom, in shadow for a lot of the day). Runs non stop 24/7 even when cloudy for days on end. I close the fan when it’s snotty out, taken waves over the bow no leaks. Not sure why people say they are bad, I haven’t seen any competitors model that’s nearly as good. Whether you want passive vs active ventilation is another issue.  

Cat27rem said: I would like to install a solar vent on my head hatch. Is it possible to drill the hole using a hole saw with out cracking the lenses? I have a new hole saw bit. Plan on masking tape the lenses and going slowly with the drill. Does anybody have any tips? Click to expand

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