Installing a solar vent fan

[Mike Banks]

I have installed a few of these, and for what it may be worth, here is how I install them.

First, having decided the approximate location, I cut a swuare or circular piece of pklywood about half an inch or so thick, if the deck is level, or two or three thinner pieceds if the deck is curved, the pieces are larger than the diameter of the base of the vent, by at least w=rtow inches all around.

Draw a square with rounded corners, or a circle, whichever you prefer, on the deck and remove any paint and finish down to clean glass or plywood. Cut the hole for the vent about five millimetres (about 1/4 inch greater in diameter than the vent duct, so as to allow easy clearance and some room for sealant. Cut the same sixed holes in your plywood mounting board, or your thin sheets of ply for the uneven deck if you have a curved deck.

Mix up some epoxy glue using Cabosil and epoxy, and using clamps through the hole in the deck, clamp your mounting board or boards so they the thickened epoxy squishes out all around the outer and inner edges of the hole and the mounting board.

Using a giant popsicle stic, or a tongue depresser, or a plastic disposable spoon, make a nice fillet around the outer edges of the mounting bioard and remove any from the inside of the hole once it has begun to set and is easily cut with a knife. While it is still not fully cured, and using a vacuum cleaner with a fine filter bag, hand-sand around the inside sucking up any dust with the hose in your other hand. Sand off using a sander with hose attached sand to a smooth surface all of the outer surfaces of your mounting board, and give it one light coat of thinned epoxy, or better still, an epoxy slow-cure penetrating timber preservative.

Cut a sheet of glass cloth, of sufficient size to completely cover the mounting board and some of the surrounding area of pre-sanded deck. Using epoxy resin, carefully brush the resin through the cloth so that no bubbles remain. Once it has taken its initial set, apply a second coat to fill the remaining cloth. Once that has set, you can cut out the circle in the centre using a dremel tool or curved tin snips. Paint the mount using Polu-u 400 primer or something similar, it is epoxy, then the final coat of two-pack polyurethane hull finish with its UV resistance. Once that has set (it pays to do a few of these all at the same time if you are doing more than one vent) you are ready to mount the solat=r vents. I recommend those having a battery--they run all night as well as all day, but they do make a slight sound when running.

I mount mine using the silicon sealant used by plumbers on roofs and gutters. I put it on the base of the vent and twist it to and fro as it seats, but do not crush all of the sealant out. Let it cure.

Then you drill the holes to screw down the vent, and having done so, I pot a little tape over the holes from underneath the deck, so no drips of anything get through to the saloon or cabins beneath. These holes will be the source of problems unless some effort is made to stop water getting down under the screws themselves. I use a cylinder-head sealant such as Hylomar, spray it down the screw holes, on the screws, and make sure that when the screw snugs down, some Hylomar is under the screw head.

Now you have the last and important job--fitting the rope-deflection rails.

I use small hand rails either side of the vents facing athwartships. They will deflect a rope over the vent instead of allowing it to rip the vent from its mounts and send it over the side. They have to be BOLTED to the deck using countersunk bolts. Do the Hylomar trick again under, around and inside the holes you drill. The rails cost about twenty five bucks each, you need one each side of each vent.

If you mount your vents flush on the deck, as like as not they will leak. That half-inch is important, and it regains some of the strength lost when cutting the hole for the vent.

[daviddiscenza]

Originally Posted by travellerw

The fan will come with a gasket (I believe its neoprene). Our fan was installed with that gasket and there is no signs of deterioration even after 3 years (in a Lewmar acrylic hatch). It has never leaked even though its been through some REALLY SERIOUS rains. We used no other sealants.

Now as to the solar fan itself. I probably won't have the popular opinion, but I think they are a waste of money. Frankly I don't think they move enough air to do anything. Even when ours was new it didn't move enough air to make a tissue or toilet paper move when held up close. I have never been able to feel any amount of air movement from it (holding my hand up for instance). To me, its just an overpriced whirly gizmo.

Travellerw, what model fan did you have?

[Fore and Aft]

I am with TravellerW, I have opened a number of closed up boats when doing surveys and still found them hot and stuffy even when you can hear these fans whirling away.
Cheers

[Mike Banks]

I had about four of them in different places in my tri--but if you want to change the air inside a vessel you need to leave a port open somewhere. The one I left open was in the heads. Before I installed the solar fans, the boat was always stuffy and smelled stale. After installing the fans I could return days later and the boat was clean and fresh--and the mould which we always had to remove had all disappeared and it never returned.

Each of those little fans will expel many cubic feet of air in a 12 hour period.

They do not solve design problems though. All vessels, or most of the ones I have seen, are inadequately ventilated and have pockets where air movement in minimal. Bilges are a case in point. So are prows, the fore peaks and stern peaks in trimarans and cats, and in almost all vessels there was an easy solution that never seemed to occur to designers. Fit ventilation pipes to extract air from these places, allowing fresh air to replace the air removed. Doing it this way removes odours and keeps the vessel dry. 3 inch diameter PVC pipe set against the deck shelf and fitted with a cheap axial fan (which could be connected to a small solar panel) works away hour after hour.

I love solar vents.

[travellerw]

Originally Posted by letoile

Are you sure you have it in the open position... That's when the inner white ring sleeve is pulled down into.the boat and about 3/4" of.the white ring is showing below the black outer housing. Also to increase air.flow remove the Mosquito screen plate. It is not necessary since they can't fly against the air.flow to get in. Works on our boat for sure.

Yup and yup.. had it for 3 years now.. Actually have had 2 as 1 needed to be replaced under warranty. Does very little if anything on our boat.

[daviddiscenza]

Thanks to all who replied. My purpose of installing the plan is to move air and prevent the build up of mold. We had a problem with that over this past winter. If it doesn't work, well... what's another several hundred dollars for new hatch?

[fritzdfk]

I wish they made one that uses ship's electric power. If you have a couple solar panels the power is there to use. I would like one that was somewhat more powerful than the solar models. Also I am in Alaska and often there is not enough sunlight to keep the battery charged on the solar vents.

[skipmac]

Originally Posted by fritzdfk

I wish they made one that uses ship's electric power. If you have a couple solar panels the power is there to use. I would like one that was somewhat more powerful than the solar models. Also I am in Alaska and often there is not enough sunlight to keep the battery charged on the solar vents.

My idea as well and easy enough to do. Get one of these https://noctua.at/en/products/fan that will fit inside an existing dorade box or if you're short on dorades install a new one for the fan. These are the best 12V fans on the market and come in a very wide range of sizes and air flows. Careful which model as some are designed to work on a special controller and won't run on straight 12V. The PWM 4 pin are the ones to avoid, the 3 wire are 12V. Best deals on eBay.

Install the fan inside the dorade and run a small wire from your electrical system and you're good to go.

[ramblinrod]

Originally Posted by daviddiscenza

I'm planning on installing a solar vent fan on the salon hatch. It's one of the clear type of hatches. The manufacturer warns about using a sealent with polysulfide compounds as they may damage the hatch.

I'd like to hear from someone who's installed one of these vents to learn what they used as a sealent. Thanks to all who reply.

I have sold, installed, and owned many.

They are great for moving a little air through a closed up boat, to help with condensation and stale odours.

The most effective method is to put in one that draws air in at one end of the boat (say galley) and another that discharges at the other (in the head).

This avoids head odours / condensation wafting through the entire boat.

With boarding waves they can take a little water in (as can even the best dorades and cowls).

The point is, they are intended for limited ventilation, not intended to cool the boat down. We use Caframo Sciroccos or Bora fans for the latter (when the windscoop won't work).

[daviddiscenza]

Brilliant idea, Skipmac! I'll get some measurements this weekend of my two dorades. My one concern is that these fans look as if they are meant to cool computers. I'm wondering how they'd fare in the elements.

[jamhass]

We have one in our head, mounted in place of an existing dorade. Works great for keeping the head area fresh and a little cooler. Our first one lasted 5 years before the motor finally gave up. So far, no leaks, frees some deck space relative to the dorade, and works just as hoped. No complaints.

[Franziska]

We had old solar vents which where broken. Instead of buying 2 new ones for 250€ I hard wired 2 10€ computer fans into the old housings.
The fans get power from the big solar panels, so in a way they stayed solar fans..

[Uncle Bob]

Originally Posted by daviddiscenza

Thanks to all who replied. My purpose of installing the plan is to move air and prevent the build up of mold. We had a problem with that over this past winter. If it doesn't work, well... what's another several hundred dollars for new hatch?

Hi, my boat had three installed when I got it, two pushing in air and one extracting air, works well and no odours at all. The quality of the fans though is another story.

[Sos]

So what make would advocates of solar fans recommend?
Our rear cabins are where the diesel engines are located, under the berths, and I want to remove the engine smell, while and after they have been run.
I have mushroom vents elsewhere that are great for ventilation but not sure they would remove the smell so well, so thinking the solar fans on extract would work?

[bcboomer]

Sos.

See #23 above. Solar fans will not move enough air for this except when the boat is not in use.

A couple of Noctuas will do the job and they have some designed to move a large volume of air in a low resistance situation. They also now make a PWM controller that will allow speed control without wasting energy to heat.
You could have them on high when the engine is running and quietly ticking over at night.