What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Defrost Fan Specs

I

iamtheari

Well Known Member
Does anyone know exactly who makes the defrost fans that come in the RV-14 finishing kit, and what their specified airflow is?

I'm looking at upgrading the fans to improve airflow in the hopes of improving the defrosting ability. Newegg carries a case fan with 50mm hole spacing (which is what I measured on the kit-supplied fans) that claims 39 CFM airflow at 20 dB and ships from China. Or, for more money you can get one that claims 17 CFM at 26 dB that ships from America, with most likely a better bearing in it.
 
My main question is how many CFM the kit-supplied fans move. It?s hard to gauge an upgrade without knowing the baseline. I agree that noise level doesn?t matter in this application.
 
Defrost or de-fog?

Not sure if you?re asking a theoretical question (ie not flying yet). If you?re just concerned about de-fogging capability, it doesn?t take much airflow. I use two small muffin fans and they work great.

Defrosting the exterior would be another matter altogether and I doubt a defrost fan would be very practical. Since I hate scraping the glass with anything, I use a spray bottle filled with windshield washer fluid on my truck which parks outside in Canada. Just spray it on and frost melts instantly. Not sure it?s compatible with our plexi windshields but may be worth looking into.

Bevan


iamtheari said:
Does anyone know exactly who makes the defrost fans that come in the RV-14 finishing kit, and what their specified airflow is?

I'm looking at upgrading the fans to improve airflow in the hopes of improving the defrosting ability. Newegg carries a case fan with 50mm hole spacing (which is what I measured on the kit-supplied fans) that claims 39 CFM airflow at 20 dB and ships from China. Or, for more money you can get one that claims 17 CFM at 26 dB that ships from America, with most likely a better bearing in it.
Click to expand...
 
Bevan said:
Not sure if you?re asking a theoretical question (ie not flying yet). If you?re just concerned about de-fogging capability, it doesn?t take much airflow. I use two small muffin fans and they work great.

Defrosting the exterior would be another matter altogether and I doubt a defrost fan would be very practical. Since I hate scraping the glass with anything, I use a spray bottle filled with windshield washer fluid on my truck which parks outside in Canada. Just spray it on and frost melts instantly. Not sure it?s compatible with our plexi windshields but may be worth looking into.

Bevan
Click to expand...
I'm asking a practical question. I was flying the prototype with Mike Seager last week and the fans had a hard time clearing fog from the interior of the canopy. More airflow can't hurt.
 
I've had the same problem (inability to de-fog the windshield). The fans seem very weak, you can hardly feel the flow with your hand. Also there's nothing to dry the air like in an automobile defogger which uses the air conditioner condenser..

I'm also considering a more powerful fan and maybe also running a 1in blast tube from the heater inlet up to the fan intake, just not sure if the localized heating of the canopy in that area would be harmful to the plexiglass. Anyone done something like that?
 
Last edited:
Jake14 said:
I'm also considering a more powerful fan and maybe also running a 1in blast tube from the heater inlet up to the fan intake, just not sure if the localized heating of the canopy in that area would be harmful to the plexiglass. Anyone done something like that?
Click to expand...

The standard cabin heat valve used by Glasair is a rotary selector valve actuated by a Bowden cable. Pull the cable to transition from no heat to full heat; keep pulling and you start to move from full heat to a mix of heat and defrost. The defrost air is supplied to a composite spreader (looks like the vacuum cleaner attachment used to suck dirt off a hard floor) covered by an aluminum plate with several holes drilled in it.

I've flown with this setup in temps down to -20C and it works quite well. It takes only a minute or two to start getting defrost action, and by the time the run-up is done I find I have to push the control in to the point of having just a small portion of defrost and the majority of the heat being dumped on our feet.

As long as you use a diffuser there's not likely to be a high probability of damaging the windscreen. Make sure you feed that diffuser with a smaller-diameter hose - pouring the full effect of the 1.5" SCAT hose onto the windscreen might produce a negative outcome.
 
iamtheari said:
I'm asking a practical question. I was flying the prototype with Mike Seager last week and the fans had a hard time clearing fog from the interior of the canopy. More airflow can't hurt.
Click to expand...

Just curious, was that in flight or only on ground that you had issues? My RV-8 windshield would sometimes fog up on the ground on a cold day but never had any issue in flight. For taxi & preflight run-up I found that opening the canopy just a fraction of an inch was enough to defog the windshield so I never installed any fan. I did drill a bunch of holes in the glareshield which helped to allow warm air behind the panel to escape (mainly to help cool avionics in summer but likely also helped keep windshield free of fog in flight during winter).
 
Our experience testing the prototypes here in the north wet (west) where the dew point spreed is often very small, is that wind screen fogging is usually only a problem on the ground prior to take-off (cabin heat is not really functional).

That was the intend of the defog fans (we have never referred to them as defrost fans.... I don't think the would do anything to remove frost).

Once in the air, the good performance of the cabin heat usually makes using the fans unnecessary.
 
rvbuilder2002 said:
Our experience testing the prototypes here in the north wet (west) where the dew point spreed is often very small, is that wind screen fogging is usually only a problem on the ground prior to take-off (cabin heat is not really functional).

That was the intend of the defog fans (we have never referred to them as defrost fans.... I don't think the would do anything to remove frost).

Once in the air, the good performance of the cabin heat usually makes using the fans unnecessary.
Click to expand...
Fair point. I just looked at the plans and they are indeed "defog fans." I don't mean to imply that they should remove frost any better than the "defrost" in my car does. We just lack the word "defog" here in North Dakota.

It seemed to me that last week's weather really tested the limits of N144VA's fans, which inspired this thread. Do you happen to have the OEM information on the fans that come in the kit as part number ES-00056?

I probably don't "need" to upgrade them since we have nowhere near the humidity that you do in the PNW. But if it's something I can easily do then I am leaning that way.
 
You must log in or register to reply here.
Back
Top