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  #1  
Old 12-17-2017, 06:40 PM
msaltzman14 msaltzman14 is offline
 
Join Date: Mar 2017
Location: New York, NY
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Default Adding Second Heat Muff, but into same Heat Box?

Hi All-

I'm trying to increase the heat output on my -9. It's getting cold!

I'm trying to do minimal new cutting of the airplane until I exhaust other options, so this is my current plan:

Add another heat muff on left side exhaust, run intake scat from cowling inlet. Then, instead of running the hot scat from the new muff to it's own heatbox and making a new hole in the firewall, I was thinking I'd join this duct to the existing hot air ducting from the existing muff, before the heat box, thus still just have one hole through the firewall. As of now, the one muff just isn't putting much hot airflow through the existing heatbox, so I'm not too worried they'll crowd each other out. I'm trying to increase the volume of hot air that's coming into the cabin, so this seems like it's worth a try.

Then, if that isn't enough I'll go ahead and add the second heat box, but I'd rather wait on that until I need to.

Have you guys found any good 2-into-1 junctions for Scat tubing? Anything obviously wrong with this plan?

I'm new to this, so if there's anything obviously dumb here, please point it out!

Thanks!
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  #2  
Old 12-17-2017, 06:52 PM
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Dbro172 Dbro172 is offline
 
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Location: West Fargo, ND
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Default

Vans sells one: https://www.vansaircraft.com/cgi-bin...outing-devices.

Before adding a second inlet you could also just try wye?ing off the existing inlet, to a second heat muff and then wye?ing back into the heat box.

And if all that fails, you could go with Vetterman mufflers. I have vetterman exhaust with dual mufflers. I use the stock vans heat setup and it is routed through a shroud around one of the mufflers and then into the heat box. This provides plenty of heat. Haven?t flown too much below 10-20 degrees F. But even at that, I rarely have the heat full open. I just modulate it as needed.
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  #3  
Old 12-17-2017, 07:04 PM
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Carl Froehlich Carl Froehlich is offline
 
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Location: Dogwood Airpark (VA42)
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Running two heat muffs in series works.

As option, try first putting a stainless steel pot scrubbing pad in your existing heat muff. It does two things:
- adds significant heat transfer area
- slows down the air a little so it gets hotter. While you have slightly less air volume, it is much hotter.

I did this on my first RV, and just helped someone do it on his RV-14 (he is flying his first winter in New Jersey). He is now flying warm.

Don?t pack the pad in too hard - leave it a little loose.

Carl
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  #4  
Old 12-17-2017, 08:12 PM
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N941WR N941WR is offline
 
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Get some exhaust wrap and wrap just your heat muff, not the exhaust. That will really increase the heat output.

Buy extra because every condition inspection you will need to remove it.
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  #5  
Old 12-17-2017, 08:19 PM
msaltzman14 msaltzman14 is offline
 
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Thanks guys for the feedback. As of now, I'm getting my inlet from behind the back left cylinder and the volume of air coming into the cabin just isn't much. I'm worried that adding steel wool inside the existing muff might reduce airflow further, even if it makes the air warmer.

I'm going to try adding a second muff and y'ing it back into the existing heatbox. May also run the output from the firewall towards the front of the instrument panel aimed at our bodies, rather than just dumping at the firewall and partially warming my feet.

Thanks all!

Mike
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  #6  
Old 12-17-2017, 08:34 PM
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Dbro172 Dbro172 is offline
 
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Did you flare open the inlets on the cockpit side where the heat box enters the cabin? If your inlet is on the back left cylinder, it is the same as the rest of ours...
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RV-9A #92103 - N803DK
G3X, Superior XO-320, Dual Pmags, Catto 3B
www.mykitlog.com/dbro172/

1974 Bellanca Super Viking - N16AW - Flying
RV-8 #83565 - N184DK - building
1968 Mooney M20C - N6801N - Sold
1956 C-182 - N744W - Sold
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  #7  
Old 12-17-2017, 08:38 PM
msaltzman14 msaltzman14 is offline
 
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Hey Derek-

What do you mean when you say flare open the inlet on the cockpit side?

As of now, their is a flange on the engine side which accepts the scat duct from the muff and it just enters the cockpit via that hole through the firewall, no ducting on the cockpit side of the aircraft.

Am I missing something?
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  #8  
Old 12-17-2017, 09:25 PM
N96TJ N96TJ is offline
 
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Location: Costa Mesa, CA
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Two things I have learned for better heat muff performance:

1) You want the opening in the baffle to the SCAT tube to be no larger that 1" diameter. Use tape or a restriction plate to close it down. You need to give the air time in the heat muff to pick up heat. More air flow than that just means more cold air into the cockpit.

2) Use coiled solid copper wire inside the heat muff to improve heat transfer. 18g or 14g solid wire wound into a tight coil about 1/2" diameter so it looks like a long spring. I use a pencil or a 1/4 socket extension for a mandrel. Take those coils and wrap them around the exhaust pipe inside the muff so the air has to flow between the wire loops on its way to the outlet.
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  #9  
Old 12-17-2017, 09:56 PM
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Captain_John Captain_John is offline
 
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Quote:
Originally Posted by N941WR View Post
Get some exhaust wrap and wrap just your heat muff, not the exhaust. That will really increase the heat output.

Buy extra because every condition inspection you will need to remove it.
Yuuuuuup...

Just do this...
Get the stuff at auto palace.

If you are careful you can re-use it. Mine is going on its third year!

CJ

I bet you wont do this though... Good luck with the plumbing work!

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  #10  
Old 12-17-2017, 10:20 PM
msaltzman14 msaltzman14 is offline
 
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Thanks guys! I'll start with the copper wire and exhaust wrap, that sounds like the path of least resistance for now.

Thanks all-

Mike
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