Looking for forced-air vent recommendations

Lomax

Lomax

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Hi all,

I would like to install a beefy vent in the forward cabin roof, accommodating a 12V fan for forced ventilation. I've seen a lot of "solar vents" around, but I'm looking for something much more powerful, with a proper exhaust fan that can shift a lot of air when needed. I'd also prefer if the internal structure was as low profile as possible; I already have plenty of fittings on deck which protrude 10-15cm, while ceiling height inside the cabin is severely restricted - much better for me if the bulk of the ventilator ends up on the outside. Anyone have any suggestions?
 
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How about using an inline blower? You could put it in a locker and duct it to a deck vent. About £30 for a Rule 240 inline blower which will shift a fair amount of air. I built something similar into the heads of my old HR, ducted to exhaust into the anchor locker, which had lots of gaps around the lid to let the air escape.
 
pvb said:
How about using an inline blower? You could put it in a locker and duct it to a deck vent. About £30 for a Rule 240 inline blower which will shift a fair amount of air. I built something similar into the heads of my old HR, ducted to exhaust into the anchor locker, which had lots of gaps around the lid to let the air escape.
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Only trouble is those Rules are bloody noisy. My Vetus engine room squirrel cage started acting up. I got a 4" Rule, too big then a 3" one, both noisy, almost a high pitched screech. I put up with it until I fixed the squirrel cage. The OP is welcome for a modest beer token contribution for either!
i will have to bring them home on Tuesday if he does.
Stu
 
skipper_stu said:
Only trouble is those Rules are bloody noisy. My Vetus engine room squirrel cage started acting up. I got a 4" Rule, too big then a 3" one, both noisy, almost a high pitched screech.
Click to expand...

Most powerful fans are noisy. Interestingly, my newish Bavaria has a Rule inline fan to cool the engine compartment. What's really interesting is that it's a 24v fan on a 12v supply, and it's fairly quiet. Just a thought.
 
pvb said:
How about using an inline blower? You could put it in a locker and duct it to a deck vent. About £30 for a Rule 240 inline blower which will shift a fair amount of air. I built something similar into the heads of my old HR, ducted to exhaust into the anchor locker, which had lots of gaps around the lid to let the air escape.
Click to expand...

Good suggestion if locker space is ample, and you're able to route the duct out of the way. Won't work in my case though - and as pointed out by @skipper_stu those things tend to make horrible amounts of noise. An axial PC fan would be perfect; plenty enough cfms and far less noise, but they have square frames and won't fit inside the tube of a "mushroom" ventilator. Hmmm.
 
To illustrate with pictures, this is basically what I'm after:

myvent.jpg

Other than the obvious issues with trying to put a square fan in a round hole - which I'm sure that modern applied physics has a clever solution for - I cannot see any logical reason why such a product does not already exist, or why I am unable to locate one.
 
Take this one for example: http://uk.rs-online.com/web/p/axial-fans/1360686/ Sure, pricey at £50, but that's half the price A.S.A.P. charge for the "4dek" monstrosity, and it shoves out three times the cfms (70 cfm vs 25 cfm). All that's needed is a "mushroom" vent with a >=136mm inner diameter, and something to glue into it that will allow me to screw the fan in place. No?
 
I've looked into this for a bit and was similarly disappointed at lack of options and/or funny prices. Our current bodge is a car 12V fan blu-tacked onto the inside of our dorade, blowing air out. By sheer accident they were the same size and this got us through the odd rainy day at anchor in England. We've since sailed on to nicer climates so the fan now serves its original purpose of cooling bodies (although it's been 31°C yesterday and we had to resort to jumping off the back of the boat for that).
 
Resurrecting this thread as I just had an idea I'd like to get some feedback on. Rather than buying (expensive) circular frame fans, and messing around with fitting them inside the vent ducts, how about using standard square frame PC fans (120x120mm) and fitting them inside the ceiling? Something like this:

nY48oxu.gif


Provided the fan housing seals against the roof it should be just as air tight (and damp proof) as a vent duct, and if the opening in the panelling is slightly larger than the fan housing the fan will be easily removable from the inside, for cleaning and replacement (held in place by the internal grille). A sliding hatch to close off the vent when needed takes up minimal height (nothing to knock your head on). What do you guys think?
 

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Lomax said:
Resurrecting this thread as I just had an idea I'd like to get some feedback on. Rather than buying (expensive) circular frame fans, and messing around with fitting them inside the vent ducts, how about using standard square frame PC fans (120x120mm) and fitting them inside the ceiling? Something like this:

nY48oxu.gif


Provided the fan housing seals against the roof it should be just as air tight (and damp proof) as a vent duct, and if the opening in the panelling is slightly larger than the fan housing the fan will be easily removable from the inside, for cleaning and replacement (held in place by the internal grille). A sliding hatch to close off the vent when needed takes up minimal height (nothing to knock your head on). What do you guys think?
Click to expand...

Nice animation! I've seen a very similar arrangement on an Oyster 55, alas, the computer fans had all succumbed to the salty air and died. So make sure they are easy to swap out and carry a supply of spares.

I also find the sliding cover inside a bit unsightly. That boat had none, and to close the vents, you'd take off the exterior mushroom/dorade covers and replace them with cover caps. This was only done while the boat was laid up for winter (with a dehumidifier) and supposedly during rough ocean passages.

Meanwhile, we have discovered a good (and in hindsight obvious) solution for our boat: The Eberspächer diesel heater already has air ducts snaking into every cabin on the boat. Simply popped the duct off the heater and have above mentioned 12V fan blowing into it (using duct tape for actual ducting jobs), which carries a surprising amount of air into the cabins. Might at some point replace it with a properly installed inline blower, but so far, so good.
 
Yngmar said:
Nice animation! I've seen a very similar arrangement on an Oyster 55, alas, the computer fans had all succumbed to the salty air and died. So make sure they are easy to swap out and carry a supply of spares.
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Thank you :) I do like to visualise my ideas; makes it easier to think, and to explain to others how I'm thinking. Yes, I do expect the fans to die a death fairly rapidly, which is why I wanted a solution that makes them easy (and cheap) to replace.

Yngmar said:
I also find the sliding cover inside a bit unsightly. That boat had none, and to close the vents, you'd take off the exterior mushroom/dorade covers and replace them with cover caps. This was only done while the boat was laid up for winter (with a dehumidifier) and supposedly during rough ocean passages.
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Agreed. TBH I have no idea how important it is to be to be able to close the vents; I do intend to live aboard year round though, and suspect that it might be useful during cold winters (like the current one!). But if the vents are to be closeable the mechanism must not protrude too much on the inside; ceiling height is precious! A sliding hatch was the best solution I could come up with that still allows a fan to be installed - many marine vents use a central threaded rod with a knob for closing, but this would interfere with the fan...

Edit: An alternative to the sliding hatch might be a "hit & miss" grille such as the one below - certainly looks a lot better, but also blocks >50% of the "free area"; with the fan already reducing it by 50% in the eyes of the BSC people (or so I am told), I would only get ~25% free area...

Hit___Miss_Adjustable_Vent_229mm_x_229mm_Metal.jpg
 
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Lomax said:
Agreed. TBH I have no idea how important it is to be to be able to close the vents; I do intend to live aboard year round though, and suspect that it might be useful during cold winters (like the current one!).
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Useful to be able to close them in cold UK winters (can recommend sailing south - much milder here in the Algarve). But truly essential during rough weather passages, as all of the Dorade boxes/mushroom vents will get overwhelmed when sufficient water quantities wash over deck or they get submerged, and then large quantities of water can rush in.
 
Just thought I'd share an update on this... No internal grilles yet, nor insulation or panelling, but pretty pleased with how my idea has worked out so far!

masking.jpg silicone.jpg hats_off.jpg mushroom.jpg
insect_mesh.jpg waterproofing.jpg fan_installed.jpg HTF_120_Blende_Single_Classic.JPG

As luck would have it, the mounting holes for the mushroom vents lined up perfectly with the standard monting holes of a 120mm PC fan. I threaded the holes (M6) and used 40mm long brass screws to attach the vents, and the fans simply slip on over the protruding screws on the inside. I made the insect meshes from stainless steel mesh which I cut to size before wrapping the edges with gaffa tape - this doubles as a soft seal against the fan housings, which also reduces vibration. I opted to use silicone for mounting the vents, to make them easy to remove in the future, taking great care to mask off in order not to get any silicone on anything which should be painted (the excess was easily removed after the silicone hardened). The edges around the vents were finished off with a bead of Sikaflex to promote run-off. I also squeezed silicone into the fan electronics to hopefully increase their service life (I have low expectations, but these fans are cheap).

The last picture shows the stainless stell grilles which will go on the inside - these have a wide enough border to fully cover the cut-outs in the panelling, and will allow easy removal of the whole stack from the inside (for cleaning, service and inspection). Closing of vents for cold weather will be done by fixing loose panels on the inside - hopefully with magnets, if the vent grilles prove to be magnetic (as some stainless steel is). Total cost for six complete vents is under £400.
 
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Lomax said:
To illustrate with pictures, this is basically what I'm after:

View attachment 65810

Other than the obvious issues with trying to put a square fan in a round hole - which I'm sure that modern applied physics has a clever solution for - I cannot see any logical reason why such a product does not already exist, or why I am unable to locate one.
Click to expand...

Can't find them on line now but we have several hatch vents which look a bit like the top half of a stainless flying saucer with a clear plastic middle. Computer fans with the corners cut off fit into them OK and the ones in both heads still working after about 15 years. Wouldn't want to try to sleep with one running though.
 
Graham376 said:
Can't find them on line now but we have several hatch vents which look a bit like the top half of a stainless flying saucer with a clear plastic middle. Computer fans with the corners cut off fit into them OK and the ones in both heads still working after about 15 years. Wouldn't want to try to sleep with one running though.
Click to expand...

I guess those are 80mm dia fans? Fan noise increases as fan diameter goes down (for a given amount of air moved) - that's why I wanted to use 120mm vents. Also, computer fans can be PWM dimmed which allows them to run very quietly while still pushing a fair bit of air.
 
Lomax said:
I guess those are 80mm dia fans? Fan noise increases as fan diameter goes down (for a given amount of air moved) - that's why I wanted to use 120mm vents. Also, computer fans can be PWM dimmed which allows them to run very quietly while still pushing a fair bit of air.
Click to expand...

A long time since I fitted them but think they're 4"/100mm, just connected via switches with no speed control, which is fine for the heads.
 
I have two 140mm dia Computer fans in my forward cabin, they move quite a lot of air and are virtually noiseless. I run them through the winter too when the boat is unused for a few weeks using a 12v timer, they use very little power and prevent condensation.
Best of all they cost £9 for two so I don't mind if they only last a year or two
 
The ' flying saucer with a transparent centre ' jobs sound like Mushroom Vents from E.C. Smith - they come in static ( ie not doing much ), solar - not powerful enough for the OP - and I think there are or were powered fan options - a lot of people don't realise for a few £ more there's a version which is closeable in very heavy weather - a snag though is the clear centres always discolour with U/V.

Not really my area of needs but if Vetus are still going I seem to remember they had a range of powered vents - also find out what mobo's use in engine rooms, these should have the bonus of being spark - safe.

How about these ?

https://www.fisheriessupply.com/vents-fans-hatches-and-windows/engine-room-blowers-fans
 
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