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  #31  
Old 01-20-2022, 11:44 AM
KayS KayS is offline
 
Join Date: Jul 2009
Location: lake constance
Posts: 448
Default

sounds convincing enough. will check ifsome SS is laying around in my scrap metal box.

Thank you for taking the time.
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  #32  
Old 01-20-2022, 11:56 AM
Tailwind/RVGuy Tailwind/RVGuy is offline
 
Join Date: Dec 2018
Location: Holmen
Posts: 58
Default

As a point of reference, I have an 0320 E2C with a cross over exhaust system. I have two heat muffs in series on the tailpipes. The one on the left has the inlet in front and outlet in the rear. It feeds directly across (around the back of the airbox) and into the rear of the one on the right. From the front of the right one, it goes into the cabin.

I originally thought about the wound spring idea but didn't want a bunch of stuff inside the heat muff. I fly all winter in Wisconsin and really don't have any issues keeping warm even 0 degrees F. What is interesting and mentioned in this thread is that if I "throttle" the cabin heat valve closed, the temp of the incoming air goes up because the air is moving slower thru the system and picks up more heat. The downside is that less air is coming in so the total amount of heat in the cabin is less even though it is hotter. I am glad we are having this conversation as many people completely shut down when it gets cold outside and miss out on some great flying.

Keith
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Keith in Lacrosse WI area
Finished Wittman Tailwind in 2016
Flew RV9A and RV6a while building
lurking for years but now paid
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  #33  
Old 01-20-2022, 12:43 PM
Darin Watson Darin Watson is offline
 
Join Date: May 2011
Location: Calgary, AB
Posts: 205
Default Pattern

Attached are the dimensions I used. As it was 2014 I don’t recall if the shop I had do them used 1/16”, 1mm or 1.5mm, as I told them any of those would be fine with whatever they had available. I did find that they charged $4.50/each (CAD) to laser cut them.

Good luck and use at your own risk, no warranty is implied nor given, your specific results may vary, side effect may include dizziness, disorientation, vomiting, diarrhea, headaches, nausea and erectile disfunction, see your doctor if conditions persist.
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Darin
C-GULF RV-7 located in Calgary, AB
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  #34  
Old 01-20-2022, 01:17 PM
KayS KayS is offline
 
Join Date: Jul 2009
Location: lake constance
Posts: 448
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Quote:
Originally Posted by Darin Watson View Post
Attached are the dimensions I used. As it was 2014 I don’t recall if the shop I had do them used 1/16”, 1mm or 1.5mm, as I told them any of those would be fine with whatever they had available. I did find that they charged $4.50/each (CAD) to laser cut them.

Good luck and use at your own risk, no warranty is implied nor given, your specific results may vary, side effect may include dizziness, disorientation, vomiting, diarrhea, headaches, nausea and erectile disfunction, see your doctor if conditions persist.
i am ok with the side effects, except for the last one.

1/16" sounds a bit beefy, i think 1/32 or so should do. the airflow in the heat exchanger shouldn't be that violent.
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  #35  
Old 01-20-2022, 03:05 PM
krhea krhea is offline
 
Join Date: Nov 2011
Location: Peck, Kansas
Posts: 187
Default Heat muff

https://www.amazon.com/s?k=heating+e...f=nb_sb_noss_1i've used a nichrome wire heating element restring kit, usually 11/32" diameter stretch it around the exhaust pipe tightly, anchor both ends. This type of element can be found in appliance repair places as a dryer element restring kit, or HVAC places as a heater element restring kit.

Keith Rhea
RV7
2022 donation

Last edited by krhea : 01-20-2022 at 03:08 PM.
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  #36  
Old 01-21-2022, 08:22 AM
Darin Watson Darin Watson is offline
 
Join Date: May 2011
Location: Calgary, AB
Posts: 205
Default Hi temp corrosion

Quote:
Originally Posted by WiscoMick View Post
Are there any metallurgists out there that could give an opinion on making Darin’s fin assemblies out of Aluminum vs. his SS? Obviously, AL is much easier to source and work with. Thanks in advance.
I am NOT a metallurgist, however, I have invested a career in the power industry dealing with Gas Turbine, coal and pet coke boilers, etc. and suffice it to say I have seen some pretty weird and surprising things with mixed metals, even at trace levels, when they are at high temperatures. Granted we are not talking 2700-3000F, but rather 12-1400F, and I also recognize there are better heat conductors such as Copper and Aluminum. All that said thin laser cut SS, does the trick, clamps are easy to keep tight as there is little to no differential expansion of dissimilar metals, and very most importantly, minimal corrosion or risk of creating a leak through a lose clamp vibrating and abrasion.

IMHO low risk, simple, reliable AND safe trump a theoretically more optimal design from a heat transfer POV, as all designs there are trade offs and i specifically choose the safer one….and it more than meets the heating needs. Please consider this in your own evaluations.
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Darin
C-GULF RV-7 located in Calgary, AB
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  #37  
Old 01-21-2022, 08:46 AM
F1R F1R is offline
 
Join Date: Nov 2010
Location: ____
Posts: 928
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Quote:
Originally Posted by Darin Watson View Post
Somewhat challenged to quantify, but I would say it was chilly at -10C with “normal chothing” prior to shirtsleeves now and at -20C you want to start to zip up your jacket. My wife and I were up at 17,500 on a cold day over Montana once and the OAT was reading -53C on the way to Mexico, and it did get uncomfortably cold…I think it was -30ish on the ground that day.
I think this re-qualifies your wife as a keeper. A lot of wives would consider a flight in an RV at -53C OAT and monitoring that the O2 was still flowing a deal breaker.
I do like your brilliant SS heater strips and the helical airflow and heat transfer they provide.

Last edited by F1R : 01-21-2022 at 09:06 AM.
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  #38  
Old 01-21-2022, 10:46 AM
BenNabors BenNabors is offline
 
Join Date: Mar 2014
Location: Alabama
Posts: 153
Default Galvanic potential

Took me a few days to get around to looking for the galvanic potential between steel and bronze. Looks like there is 0.45 volts potential between them. So galvanic corrosion between dissimilar metals is possible.
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  #39  
Old 01-21-2022, 04:01 PM
Darin Watson Darin Watson is offline
 
Join Date: May 2011
Location: Calgary, AB
Posts: 205
Wink She is a keeper!

Quote:
Originally Posted by F1R View Post
I think this re-qualifies your wife as a keeper. A lot of wives would consider a flight in an RV at -53C OAT and monitoring that the O2 was still flowing a deal breaker.
I do like your brilliant SS heater strips and the helical airflow and heat transfer they provide.
Oh she is a keeper…30 happy years, though it did help to keep a mistress for about 18 of those years….aluminum mistress that is
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Darin
C-GULF RV-7 located in Calgary, AB
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