Defrost fan

[GalinHdz]

I wired 2 computer fans on the glare shield ducted to the cabin heat box with some SCAT tubing.


I recently placed real fan covers on the glare shield instead of just holes. Makes the installation look more professional.


The fans are controlled via a panel on/off switch.


In winter, with the heat box SCAT tubing connected, they help defrost the windscreen. In the summer, with the cabin heat box SCAT tubing disconnected, they help cool the avionics. They work GREAT.

[comfortcat]

Cool!

Can we see pictures?

CC

Originally Posted by crabandy

I wired 2 computer fans to my master switch, they help defrost the windscreen in the winter and cool my avionics in the summer. A cheap and easy option to add, and yes even the heat from the avionics and fans alone is enough to make a big difference while taxing on the ground in my environment.

[ao.frog]

On my first -7, I used one computer cooling fan.
Allthough this is usable, I used four fans on my second -7 (2+2) installed on each side of the inlet for cabin heat.

For fans, I used the expensive type so the bearings would have better quality.







Here's a closeup of one of the dual fans installation:






And here's the air outlet:



BTW: all hoses where secured with clamps after the install.

The defroster are wired to a separate switch.

I only need it on the ground, because once airborne, the canopy clears quickly.


I have not installed any "air-spread" outlet, because I didn't want to restrict the airflow.
Th right seat is pilot seat so I've installed the outlet in front of the pilotseat.
The top of the windshield is painted flat black so noone sees the hole anyway, at least not on a TW.

The defroster works great for me, and I'm VERY I installed it! I'm using it on every startup from Fall until Spring.

The best reason I can think of for installing a defroster system, is that it would be a VERY difficult job to install it after the plane is done.
In fact, I can't imagine how it'd be possible...

[N427EF]

I have 2 computer fans installed, drawing air out from behind the avionics
And de fogging the windshield at the same time.
The fans draw very little power and I decided to wire them permanently on when the master switch is on.
Triple duty, cooling avionics bay, keeping fog off the windshield and reminding me to turn the master off.
In the old days we had a whining gyro telling you the master was still on.

[airguy]

I went with just a single fan, small computer supply style, more so to draw heat away from the avionics than any perceived need for defrost, since I live in west Texas. I took a 12-volt power supply fan that draws only 190 milliamps, put it in series with a 15-ohm 5-watt resistor mounted immediately below the fan in the airstream for cooling, and wired that to my avionics master with a 1-amp fuse. The 15-ohm resistor gives me a voltage drop of roughly 3.5 volts which slows the fan speed to the point that it's barely audible without a headset and I'll never be bothered by the fan noise.

I think my 430W fan is louder than this defrost fan now.

[MarkW]

Being in Florida I was more worried about the avionics heat. So to kill both birds I installed just two grills. The convection though these is good so I get some defrost and a lot of cooling for the avionics.

[JRichichi]

I'm not flying yet so I don't know for sure how well this works but for most fan installations you want a fan that has a good pressure/flowrate curve. This is especially true if you use any type of ducting. I plan on using two ebm-papst 8312H fans mounted on the F-7106 Forward Top Skin. They work as combination defog/avionics cooling fans. These are 80mm X 32mm fans. They have good flowrate and pressure. Digikey has them in stock for $33.22. Not cheap but these are really nice fans. If you ever need a more powerful fan, the ebm-papst 8212JH4 fan is a 80mm X 39mm fan that has much more flowrate and pressure and will bolt in the same place as the lower power fans. You can find the specs for these fans by doing an online search.

I hope this helps.

Jeff

[BillL]

I opted for a radial fan.

http://www.mouser.com/ds/2/310/13377...ies-476196.pdf

30CFM with no back pressure, the link above has the flow curve.

I plan to have the suction side to come off the top of the heat distribution box. In past posts, Bob Axsom, ( http://www.vansairforce.com/communit...04&postcount=3 )he says without heat it won't work in certain conditions, but with heat, works in all conditions.

The plan is to blow at a with a shallow incidence angle for best velocity across the canopy. A test by blowing into a box and cutting slots and holes, left slots as being the best approach. YMMV.

That ebm-papst 8212JH4 fan is impressive. I might rethink this selection.

[JonJay]

It is a frequent occurance here in the NW. I installed a 72" fan from HartZell. I open the slider about an inch and it is gone in a few sexonds. Never an issue in the air, only on the ground.

[Jrskygod]

Part of what I was looking for was an idea of the size of fan and the cfm that would be used. I'm thinking a 3" dia. and about 80 or so cfm but thats just a wild guess.