Extractor fans - mushroom vents

[frahkn]

My boat and some earlier ones have small extractor (or two-way) fans located below/in ordinary mushroom vent holes.

 

I am looking to replace mine but have not been able to source 12 volt fans which are small enough to fit the 9 cm diameter holes.

 

Can anyone suggest a supplier?

 

Thanks.

 

Frank.

[kevinl]

Google "small computer fans" world's full of them apparently, for 2 way get a reverse polarity switch.

Here's one costs a fiver from Maplins.

http://www.maplin.co.uk/p/thermaltake-92mm-high-performance-fan-zt86t

K

[Top cat]

Loads of suitable ones on E bay for example

 

http://www.ebay.co.uk/itm/330796978163?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

 

£2.11. That one is not reversable but it gives you a place to search from.

 

Top Cat

[Chalky]

I used a computer fan cut down to fit. Most have a square mounting at each end - this can be trimmed from one end to allow it to fit in the vent. Alternatively use a slim line one that fits between the roof lining and the bottom of the vent.

 

Computer fans use brush less motors. These use a small electronic controller to switch the power to the windings to make the motor turn. They can change speed but they don't run backwards. Changing the polarity will either have no effect or will blow the electronics (depends how cheep the fan is). Check the power draw on the one you choose, some will draw up to 1 amp.

[frahkn]

Thanks for the info so far.

 

My existing fans are permanently mounted in a tube (like a section of drain pipe) which fills the gap between the roof liner and the outside (8 cm). If possible, I want to replace them with similar but cannot find them. Reversibility is not essential, I can always alter the switch.

 

Frank.

[tidal]

On my last yacht I found a couple of round computer CPU fans that fitted a very similar sized tube and there are quite a few small ones that are designed to cool graphics cards that could be adapted easily.

 

Some "bodging" was required but not a lot

 

ETA
However they didn't cope well with the more extreme conditions on a yacht and I eventually replaced the mushroom vents with the expensive solar powered options

Edited October 7, 2015 by tidal

[Boredrider]

I have recently used http://www.quietpc.com/casefans and can recommend them. You will see that they provide details of the amount of air shifted by the various models, the current draw, and the noise generated. The fans fitted in 2002 by the boat builder drew 2.1 amps and were very noisy. I replaced with some drawing .1 amps, shifting nearly as much air, and virtually silent - the technology has certainly moved on.........

[David Mack]

On my last yacht I found a couple of round computer CPU fans that fitted a very similar sized tube and there are quite a few small ones that are designed to cool graphics cards that could be adapted easily.

 

Some "bodging" was required but not a lot

I have heard of folk hacksawing the corners off square computer fans to make them fit mushroom vents.

[Top cat]

I cut off the corners on the downstream side of the fan and inserted it into the vent but left the ones on the upstream side to screw ot to the ceiling.

 

T C

[tidal]

I have heard of folk hacksawing the corners off square computer fans to make them fit mushroom vents.

Hacksaws!!

 

I'm far more civilised than that - I have a Dremel

[tidal]

Joking aside though some board fans come mounted on a 90mm heatsink
Most though are 92mm and a bit of dremelling (or just filing) can reduce the size very easily so they can be push-fitted in place or glued.

As I said in my first post though they can be scuppered by even small amounts of condensation

[spaceyaface]

I installed one of these in the shower, as there's a mushroom just above it.

Works a treat, it's a little noisy but very efficient and only comes on when you switch the gulper on so....

 

http://www.demon-tweeks.co.uk/Product.do?method=view&n=1914&g=242248&p=103265&d=124&c=4&l=2&utm_source=Google&utm_medium=Base&utm_campaign=Cockpit%20Ventilation&gclid=Cj0KEQjwy92wBRCl7trx4PaIo8EBEiQASPhtC0LrRPe4MdN3GAvcdVf6Au3bIEk5jv7LPNSYN2b_yW0aAjx58P8HAQ

 

I just took off the brackets....