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-   -   One or two air intakes for heat (https://vansairforce.net/community/showthread.php?t=167432)

RV7 To Go 01-04-2019 09:16 AM

Heater
 
Quote:

Originally Posted by BillL (Post 1313956)
It is easy enough do do the experiment of two heat muffs in series before you undertake the task of another FW flap.

I did (1) insulate the external shell of the muff, (2) have pushrod seals for the ailerons,

Recently, I have sealed the spar gaps, but still have a cool draft at my armpit by the fuse. Not sure exactly where that comes from. Maybe the pleats in the back bulkhead wall, those leak too, or the aft corner of my tip-up.


Good luck in your heat improvement project. Keep all posted with any data you get, and welcome aboard VAF!!

+1 to the above

I installed a second muff in series with the first through a single heat box in my 7. I also wrapped the muffs with a titanium heat wrap (Amazon). They are both piped reverse flow (inlet at the rear). I get plenty of heat through the single box so far, down to -10C at altitude as long as I keep the engine working at 2400+ rpm. Once slowed down in the cct the heat drops off noticeably. I also installed bottom cushion seat heaters. More to soften the memory foam cushions, which are like cement in the cold, than for the heat but it sure adds to the comfort. Most of the first winter was with one muff and no seat heaters. Very much nicer now. Only starting my second winter with plane but happy with the heat so far.

Al

Scott Hersha 01-04-2019 09:35 AM

I used two heat muffs on my first RV8, but with slightly different plumbing. I had the two heat muffs plumbed in series, fed from a single scat hose off the back baffle. There was plenty of volume and the second muff was being fed with already heated air. Inside the cabin I used a couple Y fittings to split off air to the back seat - with their own butterfly shut offs. There was plenty of air coming out in 4 places (2 for the back seat) and it was plenty hot. We live in Ohio and my wife would frequently ask me to turn down the heat. My current RV8 only has one standard heat muff feeding the firewall shutoff, and its not nearly enough. My January project will be to try and correct that, which will be more difficult because I have the AWI exhaust and there are space constraints on the back of the engine.

jcarter 01-04-2019 10:23 AM

Wow. This is a tremendous amount of good info. I'm leaning towards just biting the bullet and making the second air intake but I'm going to have to sit down and think about all the other ideas in this thread as well such as putting the muffs in series and the note about the Y needing to be placed in the right place to balance airflow. Thank you very much for all the data.

lr172 01-04-2019 12:13 PM

I recommend the two muffs in series. This was the recommendation from Robbins wings (the guy who makes the muffs for Vetterman) and has worked well for my 6. I am now pretty comfortable down to about 0* with two muffs in my 6, though I have gone to lengths to seal the cabin up. At 0* I still need a jacket though, so it's still not where I want it. I halted my efforts, as I will soon be flying a 10.

Be sure to carve out the inlet / outlet side of the muff that has the holes drilled. Both should be fully open, without restrictors, when used in series.

With separate inlets for each muff, you'll just get a larger volume of air that is not warm enough. Running in series will actually increase the temp of the incoming air.

Larry

rightrudder 01-04-2019 08:23 PM

Quote:

Originally Posted by krw5927 (Post 1313965)
If you have a Vetterman crossover exhaust, you might consider contacting them about a muffler exhaust. I have their muffler system, and the cabin heat muff surrounds the muffler and is generally much larger than a standard heat muff. It puts so much heat in the cabin using only a single SCAT tube and one muffler shroud, that I cannot ever run the heat on full blast even on the coldest day (RV9A).

^ My experience as well. This heat muff surrounds both crossover tubes, so there is very generous surface area for heat transfer. It's crazy effective!


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