Air venting

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Naughtyjoe

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I’m having real problems with damp in my 33ft Hunter. The lack of ventilation is causing a build up of moisture and I’m getting mould growth a lot quicker than I’ve had on other boats.
I’ve been looking at the solar powered vents to help circulate the air more effectively.
Can anyone give advice of these in comparison to usual hatch/mushroom vents that don’t have a built in fan?
 
We've got four proper dorade boxes and the boat is always dry and we've never had any mould (even though it does currently leak freshwater from a couple of places... to my annoyance!). If they - or other effective vents - are sensibly located fore/aft/port/sbd then natural air circulation means you shouldn't need solar vents.
 
dankilb said:
We've got four proper dorade boxes and the boat is always dry and we've never had any mould (even though it does currently leak freshwater from a couple of places... to my annoyance!). If they - or other effective vents - are sensibly located fore/aft/port/sbd then natural air circulation means you shouldn't need solar vents.
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Yes I’ve had dorade before and found them very good. They need to mounted on a level deck though, and the front half of my deck is quite wedge shaped. There’s currently no vents at all, not even so much as a louvre one in the washboards. As I’m having to put anything in from scratch I just wondered about the solar ones as they’re fairly slimline and unobtrusive.
 
Our deck/coachroof is quite angular and wedge-shaped too (1989 Jeanneau), but - from the factory - there are GRP sort-of trapezoid 'boxes' that raise the dorades and level out the interface with the deck. It would be possible to fabricate something similar, but harder perhaps to make it look decent!

The solar fans don't seem to get a great write-up on here and other forums. But maybe people are looking to vent moisture from cooking/showers (in which case open a hatch!) rather than providing ventilation just while the boat is left longer-term. Some people seem to get on better fitting a computer fan within a conventional passive vent and running them off the boat's solar/wind (if available).

I'd just be worried about cutting the holes for the solar ones, unless someone comes along on here and reassures that they definitely work! (or unless the holes are re-usable for something more conventional)
 
dankilb said:
Our deck/coachroof is quite angular and wedge-shaped too (1989 Jeanneau), but - from the factory - there are GRP sort-of trapezoid 'boxes' that raise the dorades and level out the interface with the deck. It would be possible to fabricate something similar, but harder perhaps to make it look decent!

The solar fans don't seem to get a great write-up on here and other forums. But maybe people are looking to vent moisture from cooking/showers (in which case open a hatch!) rather than providing ventilation just while the boat is left longer-term. Some people seem to get on better fitting a computer fan within a conventional passive vent and running them off the boat's solar/wind (if available).

I'd just be worried about cutting the holes for the solar ones, unless someone comes along on here and reassures that they definitely work! (or unless the holes are re-usable for something more conventional)
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Yes I know why u mean about the holes, I get nervous drilling into anything that’s meant to float.
We have flush fitting, frameless hatches and I was going to fit the vents into them. That way if need be I could just replace them with standard lewmar hatch vents or if worse comes to worse replacing a hatch lid is quite easy.
 
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I fitted a solar fan and yes its great if its a sunny day .I nipped to my boat today and it was jot spinning as I also am trying to dry a boat out.
 
Do you have any leaks in the boat ensuring constant moisture in the cabin? Fresh or salt makes no difference, just fix them. Even leaks from the water system are possible.
Do you shower on the boat? Major source of increased moisture level. Try and dry the shower out after use. Even drying towels out below can add more moisture.
Do you live onboard? Trying to find a balance between keeping warm and ventilation, especially with larger numbers of people on board, is difficult.
Do you cook a lot on board? Burning gas increases moisture levels.
Is you boat salty inside (people sitting on bunks in salty clothes/oilskins)? Salt always attracts moisture.

Static ventilation is what should be fitted. During the winter I have 3 static deck vents (ECS Ventilite Shut Off Vent c/w S/S Cover) on a 32ft yacht and a nice gap at the main hatch. Even though berthed in a marina I do not use a dehumifier and have never had any problem of mould.

Any surface you find that has mould on it except fabric surfaces, wipe down with a mild bleach solution, 6 to 1 of a supermarket own brand bleach as this is unscented. This should kill existing moulkd spores. All fabrics, including bunk cushions covers, should be removed and washed.
 
Concerto said:
Do you have any leaks in the boat ensuring constant moisture in the cabin? Fresh or salt makes no difference, just fix them. Even leaks from the water system are possible.
Do you shower on the boat? Major source of increased moisture level. Try and dry the shower out after use. Even drying towels out below can add more moisture.
Do you live onboard? Trying to find a balance between keeping warm and ventilation, especially with larger numbers of people on board, is difficult.
Do you cook a lot on board? Burning gas increases moisture levels.
Is you boat salty inside (people sitting on bunks in salty clothes/oilskins)? Salt always attracts moisture.

Static ventilation is what should be fitted. During the winter I have 3 static deck vents (ECS Ventilite Shut Off Vent c/w S/S Cover) on a 32ft yacht and a nice gap at the main hatch. Even though berthed in a marina I do not use a dehumifier and have never had any problem of mould.

Any surface you find that has mould on it except fabric surfaces, wipe down with a mild bleach solution, 6 to 1 of a supermarket own brand bleach as this is unscented. This should kill existing moulkd spores. All fabrics, including bunk cushions covers, should be removed and washed.
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Thanks for the advice. I bought her as a bit of a project but I’m pretty sure I’ve sealed all the leaks and she felt pretty dry until about 8 weeks ago.
She’s sat on a river mooring and I get out as much as I can to open her up and get some air blown through but she has no vents at all and the v berth in particular is getting quite damp. I think I just need to generate better airflow and weighing up the pros and cons of various methods.
 
Rhylsailer99 said:
I fitted a solar fan and yes its great if its a sunny day .I nipped to my boat today and it was jot spinning as I also am trying to dry a boat out.
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Don’t think it needs much. If I put a decent size vent in the washboards I was hoping a solar vent might just be enough to draw fresh air though the boat.
 
I have 2 Dorado vents in the saloon and the circular ventilite vents in the heads, fore cabin & rear cabin. Also the fore hatch has a ventilation position so always left in that position. New hatch above the cooker also set to the ventilation position. No problems with condensation. Moody 33. Solar vents are useless in my opinion.
 
Concerto said:
Do you have any leaks in the boat ensuring constant moisture in the cabin? Fresh or salt makes no difference, just fix them. Even leaks from the water system are possible.
Do you shower on the boat? Major source of increased moisture level. Try and dry the shower out after use. Even drying towels out below can add more moisture.
Do you live onboard? Trying to find a balance between keeping warm and ventilation, especially with larger numbers of people on board, is difficult.
Do you cook a lot on board? Burning gas increases moisture levels.
Is you boat salty inside (people sitting on bunks in salty clothes/oilskins)? Salt always attracts moisture.

Static ventilation is what should be fitted. During the winter I have 3 static deck vents (ECS Ventilite Shut Off Vent c/w S/S Cover) on a 32ft yacht and a nice gap at the main hatch. Even though berthed in a marina I do not use a dehumifier and have never had any problem of mould.

Any surface you find that has mould on it except fabric surfaces, wipe down with a mild bleach solution, 6 to 1 of a supermarket own brand bleach as this is unscented. This should kill existing moulkd spores. All fabrics, including bunk cushions covers, should be removed and washed.
Click to expand...


Wot he said. ^^^^^

Have several static vents, including at both ends of the boat (this encourages a through-flow).
Consider fitting a louvred vent to your washboard(s).
If cooking while on board have a hatch open or washboards out.
Leave your lockers and doors open when you leave the boat.
Before washing vinyl etc. down with bleach solution give it a good wipe over with water or soap and water to remove salt (which, as Concerto suggest, absorbs water from the air) and dirt (which encourages growth).
 
Naughtyjoe said:
If I put a decent size vent in the washboards I was hoping a solar vent might just be enough to draw fresh air though the boat.
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There's rarely such a lack of wind or heat differential to warrant a solar vent, which will in any case be pretty feeble in comparison to those factors (and may be fighting against them). Spend the same money on two static vents, placed in different locations about the boat.
 
LittleSister said:
There's rarely such a lack of wind or heat differential to warrant a solar vent, which will in any case be pretty feeble in comparison to those factors (and may be fighting against them). Spend the same money on two static vents, placed in different locations about the boat.
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Thank you. Yes, reading everyone’s comments that’s now the new plan.
 
On a swinging mooring I reckon you need quite a lot of ventilation, plus wedge and tie the interior doors open. To give you some idea on my 30ft yacht I have approx 70mm diameter clear air vent well forward in the cabin, a 35mm x 150mm hole (splash proof) in the washboard, and a similar area large vent in the aft cabin.

The aft cabin vent is plywood box type of thing that is secured over a left open port light located under the cockpit seat inside the cockpit. This can be closed up when at sea.

I would say if it feels noticeably drafty then it will be good.
I have never had much success with simply locking hatches in the vent position. They seem to leak when there is wind driven rain.
 
If it's got damp, take all the cushions home and dry them out.
Remove as much rope and other damp-holding stuff as you can.
Wash and dry the bilges.
If your fore hatch can be locked slightly open, that may help, maybe with a canvas cover to keep the rain off and scoop some wind in.
Louvres in the washboard are good, but you may need some sort of cockpit cover to stop rain blowing in. Drizzle is the worst.
Sometimes, on a river, you are just on a loser because the air is very damp and there will be heavy dew forming inside the boat if you have too much ventillation at the wrong time.
But if you keep the interior obsessively clean, you can avoid too much mould.
Wiping over all hard surfaces with kitchen bleach spray at least once a month helps.
 
I fitted a solar vent with battery in the small forecabin and it stopped all condensation. It also ran non stop for about eight years. The cabin was a fairly small area but the fan was fine. Came from a caravan supplier but was stainless bodied and never corroded.
 
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