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cabin heat - how much airflow?

KayS

Well Known Member
Hi All, my 7 has a standard cabin heat setup. pick up at the lower right baffle ramp, routed directly to one Vans standard heat muff and from there to the valve at the firewall.

from the beginning my cabin heat was inadequate. it goes from "cold" to "not that much cold anymore". so i tried everything... sealed all kind of gaps in the cabin (canpoy skirt, side rails, openings around seat belts, stick etc.), sealed the heater bypass valve, improved the heat muff with enlarged internal area. but no real success. i am running out of options.

what i noticed is that (if turning on cabin heat) i can feel with my bare hand that it gets somewhat warmer around my lower legs. but i don't feel a real airstream. maybe that is my problem...?

so a question to the 7-drivers with a similar setup... do you really feel a stream of incoming warm air? like a small fan would produce? it's sure hard to quantify but maybe too little airflow is my problem.

would be greatful for any input.
Kay
 
In my 6A I have same set up as you and yes, I get a very pronounced stream of warm air. I only have it on passenger side (for the wife) but feel it fine on pilot side even with battery box and fuel pump and fuel tubing enclosure between vent and me. It will even blow small pieces of paper around on the passenger seat. Very warm air.
 
Exit path ?

This raises an old question that has never been answered for me 😒
Without adequate exit capacity, you are just pressurizing the cabin/tail-cone.
A good negative pressure area for an exit port probably varies with each model and specific build. I have wondered if anyone has tried an NACA vent installed backwards to vent the cabin/fuse. Any feedback appreciated.
 
In my 6A I have same set up as you and yes, I get a very pronounced stream of warm air. I only have it on passenger side (for the wife) but feel it fine on pilot side even with battery box and fuel pump and fuel tubing enclosure between vent and me. It will even blow small pieces of paper around on the passenger seat. Very warm air.

Thanks Philip, i definitely don't have that.

is your heat muff stuffed with steel wool or something like that to increase the heat transfer area?
 
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This raises an old question that has never been answered for me 😒
Without adequate exit capacity, you are just pressurizing the cabin/tail-cone.
A good negative pressure area for an exit port probably varies with each model and specific build. I have wondered if anyone has tried an NACA vent installed backwards to vent the cabin/fuse. Any feedback appreciated.

Larry, here's a discussion that i believe adresses your question: https://vansairforce.net/community/showthread.php?t=9847

i feel that the exit air leaks i still have around the cabin, allow the cold air to enter but prevent the warm air from coming in. seems that the pressure of the cold air is higher than the warm one from the heat muff. that sort of thing...
 
Thanks Philip, i definitely don't have that.

is your heat muff stuffed with steel wool or something like that to increase the heat transfer area?

Steel wool burns:eek:
You can light it by shorting battery terminals or a match.

It makes for a pretty good fire starter so no wool in your muff please.
 
Maybe OP meant something else

I used a stainless-steel scouring pad (Very open weave) and does not block the flow that much. Steel wool might be too much of a pressure reduction if packed well. I do have 2 so not apple to apples but very hot even in an Ohio winter at altitude. (Most of the time I need to close it fairly far)
 
I have separate controls…cabin air and temp. My -9A cabin heat depends on some balance between the cabin air flow control and the cabin heat control. Best heat for me on a cold Minnesota day is black knob (cabin air) about 1/2 - 2//3 out and red knob (temp) all the way out, mixing max muff airflow with moderate cabin air flow. That gives me a nice warm airflow. I have some drafts as well but it helped to add a seal at the rear of the (slider) canopy on fuselage. It’s still draft enough that I can’t see cabin venting as improving anything. I can’t say that cabin heat has been a big problem for me, but just pulling out the heat control if the cabin air control is closed adds very little heat to the cabin.
 
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Larry, here's a discussion that i believe adresses your question: https://vansairforce.net/community/showthread.php?t=9847

i feel that the exit air leaks i still have around the cabin, allow the cold air to enter but prevent the warm air from coming in. seems that the pressure of the cold air is higher than the warm one from the heat muff. that sort of thing...

I struggle to see how that is the issue. Do you get a nice and strong blast of air from the eyeball vents? The pressure of the air coming in via the heat circuit should be at a similar pressure and therefore with everything else being the same, should provide similar behavior. I would be suspecting a different reason for the low pressure or volume.

I get a modest stream of air, but have a restrictor on the input. I have two muffs in series and have learned there is a trade off between volume and heat rise. A lot of air flow produces cooler air and vice versa. Many muffs come with a restrictor built in for this reason. You could open it, but will probably see the same as I did. Many challenges to get adequate heat out of a 6/7 and suggest research. Stopping the cold air from entering the cabin is a big part of making the heat work, just not for the reasons you state. More about leveraging the small amount of heat produced by the muff system.
 
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topping the cold air from entering the cabin is a big part of making the heat work, just not for the reasons you state. More about leveraging the small amount of heat produced by the muff system.

I agree.
Unwanted cold air leaking into the cabin will overwhelm even the best performing cabin heat system.
For the cabin ventilation and cabin heat systems to work properly there needs to be an outflow path for airflow. The problem is that it is possible to have leaks at low pressure areas where air is always being sucked out of the cockpit. If this is happening, it will cause air to always be sucked into the cockpit Through points that otherwise would just be an exit path. A common example would be the openings along the edge of the baggage bulkhead cover that are there because of the corrugation. This is actually a great exit path as long as there isn’t other leaks where air is being drawn out. In that instance the corrugations will then become an entry path.
The RV 10 has a very good cabin heat system but even that will not perform well if cold air is leaking in it. Many years ago when the prototype RV 10 was very new and it still had some pre-production doors installed, they were flexible enough that the longitudinal curve shape of the door would cause it to be sucked outward along the bottom edge. The resulting gap and the low pressure area that was on the outside of the door caused a lot of airflow from inside the cabin to the outside through this path. On one flight in very cold weather I was sitting in the back freezing while the two guys in the front seats were wanting to turn the heat down, and they were just wearing T-shirts. I finally found the leak path and threw a jacket along the base of each door and the back half of the cockpit immediately got warm and I stripped down to a T-shirt as well. The air exiting the bottoms of the doors was causing a strong flow inward through the corrugations in the baggage bulkhead which totally chilled the aft half of the cabin.
A lot can be learned by attaching a small strip of Kleenex or TP to the end of a wood dowel and move it all around the cockpit in flight in search of locations where there is airflow either in or out. Take some extra supplies with you on the flight to add more Kleenex to the end of the dowel because if you get it very close to a high flow point it will leave the cockpit and you will have to reapply. Taking a safety pilot along with you on the test flight is a good idea.
Doing this can be very enlightening when trying to solve a problem with poor cabin heat performance.
On the heating system side of the discussion, using two heat muffs plumbed in the series is highly recommended. It makes a huge difference in the amount of heat delta that you can produce. Adding stainless steel pot scrubber pads to the heat muffs does help some as well. Don’t use steel wool.
 
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Kay, I have the stock vans set up and I have very little flow and a little heat. My eyeball vents will blow your hat off, so I don't think the incoming flow is restricted by a too tightly sealed cabin. Anything under freezing temps at cruise is too cold to be comfortable with the cabin heat on full. I don't have any answers but I have a similar situation to yours.

Harvey Martin
 
I struggle to see how that is the issue. Do you get a nice and strong blast of air from the eyeball vents? The pressure of the air coming in via the heat circuit should be at a similar pressure and therefore with everything else being the same, should provide similar behavior. I would be suspecting a different reason for the low pressure or volume.

I get a modest stream of air, but have a restrictor on the input. I have two muffs in series and have learned there is a trade off between volume and heat rise. A lot of air flow produces cooler air and vice versa. Many muffs come with a restrictor built in for this reason. You could open it, but will probably see the same as I did. Many challenges to get adequate heat out of a 6/7 and suggest research. Stopping the cold air from entering the cabin is a big part of making the heat work, just not for the reasons you state. More about leveraging the small amount of heat produced by the muff system.

but that is exactly what i was talking about... when i open the fresh air vents (eyeball vents) the air is blowing into the cabin like a table fan on steroids. but the warm air from the heat muff, which should have the same or even higher pressure at the air inlet (due to ram effect or so), flows in so restrained that you can count each single air molecule.

my original question was if other guys can feel an pronounced stream of warm air. it seems some people have that. this leads me to believe that something is wrong with my heating system in first place and leaking cold air into cabin via remaining gaps somewhere being the secondary problem.

sorry if i was confusing. i'm no english teacher. even would have an hard time to explain that in german.
 
but that is exactly what i was talking about... when i open the fresh air vents (eyeball vents) the air is blowing into the cabin like a table fan on steroids. but the warm air from the heat muff, which should have the same or even higher pressure at the air inlet (due to ram effect or so), flows in so restrained that you can count each single air molecule.

my original question was if other guys can feel an pronounced stream of warm air. it seems some people have that. this leads me to believe that something is wrong with my heating system in first place and leaking cold air into cabin via remaining gaps somewhere being the secondary problem.

sorry if i was confusing. i'm no english teacher. even would have an hard time to explain that in german.

My heat does not blow anywhere near as hard as the vents. I believe this is due to the MANY restrictions in that system. You can look for flaws, but it is not designed to blow a lot of air. When dealing with air heating, you have to have dwell to allow the air to heat up. Rapid air flow doesn't transfer as much heat to that air as slower moving air. If you run two muffs, you can speed up the flow some without the penalty.

I believe the robbins vents that vetterman sells have a restrictor in the muff to slow down the air flow. You could likely increase air volume, but know that increased volume means cooler air. Rick Robbins told me that through testing he found that less volume with more heat was most effective. With two muffs, he recommended cutting out the restriction.

I would also examine the door to see if it is allowing heat air to leak out into the engine area instead of into the cabin.
 
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We don't get much of an opportunity to use cabin heat in Texas...certainly nothing like you have there near the Alps. I actually have a restrictor plate on the baffle for the SCAT tube inlet to the heat by #3 so that more air is available for cooling air to keep CHTs down. Regardless, I don't think you'll ever get a blast of air out of the heat due to the flow restrictions in the system. Certainly nothing like you'll get out of the cool air vents with the NACA inlets.

I have heard some of the guys that fly in colder climates talk about getting a long stainless steel spring and stuffing it in the heat muff to increase surface area for heat transfer. Not sure if that's better or worse than the pot scrubber pads some have suggested--just different.
 
My old RV-6 has so much force behind the heater flow that it overcomes the firewall control valve. Tried tweaking the control valve to improve the shut off, but it isn't the valve, it's the force of the hot air, so I have started disconnecting it for the summer, to keep the hot air out.
 
There are three potential issues with your set-up. Is the problem the tempature of the air comming out, or the volume of the air comming out. If you have adiquate volume, then I would put a second heater muff in series and pack both of them with SS scowering pads.
If it is a flow issue, try tapping into the baffell on the top side of the rear baffell. - How are your CHT's ?
If you have good flow and good temp, then your problem is cabin air leakage.

On my 6, you feel it warm on your legs on the passenger side, you dont feel much on the pilot side; however the caben feels OK.
 
Stop warm air leaving the cabin and being replaced by cold air: SM

I was up this morning doing approaches at 16F and rudely reminded of the problem you describe.

I have a frigid breeze that comes around the seats from the back, and based on Scotts comments, believe it is indeed air being sucked out forward of the seat backs. I know that my tip-up rail on the right side sucks. it is about .030" from allowing the teardrop seal to work. Surely the aft corners are also players, but hard to fly and test that area.

I have used puffy yarn on a telescopic pointer to test, but it is more stiff than TP. That sounds like a good one to test too

I can feel warm air across the feet and side to side at the spar station. My hot air is restricted to a 1" hole, and have a single heat muff. I did wrap the heat muff exterior with fiberfrax and then with aluminum foil to keep the heat in - it helped.

I am considering opening my flow and adding another heat muff. Time to end the suffering
 
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Reminder...we've been moving toward all-electric airplanes for a while. Lots of owners here with two alternators, multiple batteries, etc. After the post-start battery recharge, we tend to have a lot of excess electrical capacity.

So, try a heated vest. Seal the cabin air-tight, because flow isn't required. Heat is immediate. The surprise is how comfortable your hands and feet are if you keep your core warm with a vest under your jacket.

Best of all, you get to banish those scat tubes.
 
Question??

Unwanted cold air leaking into the cabin will overwhelm even the best performing cabin heat system.

Scott, couple of questions - - - any idea what the incoming temps (to the cabin) should be? I can adjust the flow to get this . . .

What is the latest thinking on the best internal baffling (muffs) for good heat transfer to the air?

Edit1[ As background, I have aileron boots & urethane plugs in the "I" section of the spar. The plugs stopped the cold breeze in front of the spar. I have sealed the baggage wall correlations with triangular urethane foam. Don't think it did much. I have one heat muff with welded 1/4" pin fins with threads via AWI. I'm not sure how much the tip-u leaks on the corners, but the left side is sealed, the right leaks to exterior along the rail (a lot) although .030" would stop it.]
 
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I have thoughts... My cabin is very comfortable down to about 0F. I have two heaters, not in series. Way back I experimented with different locations, etc. for the heaters. It is much better to put them on the tail pipes, and not the crossover pipes. It is surprising how much more heat comes from 2 cylinders, even though the heaters are further downstream, than from just one cylinder. Having two heaters in series will deliver higher temperature air but with less volume as compared to them being in parallel (more air at a slightly lower temperature is likely better than less air, but warmer). I have one heater's supply air behind #3, feeding 2" scat. I have a ground adjustable throttle at this location, and it is almost entirely closed off. I still get a noticeable warm breeze from that heater. The other heater's supply air is on the ramp just forward of #2 cylinder. This heater uses 1.5" scat. The intake on this one is about 75% covered with aluminum tape. Airflow is totally adequate.

I've tried various inserts, pot scrubbers, etc. Not worth it. If one could find a genuine solid copper pot scrubber, it might help, but I wasn't able to find any. The copper plated ones disintegrate fairly quickly.

I'm confident 1" scat would work, although I've not tried it. It's on my maybe-try-it list of stuff...

Sealing bulkhead "triangles" is a must, as is sealing the canopy and aileron pushrod holes. Stuffing a towel between the fuse exterior and the seat back helps keep cold air in the baggage area from spilling forward. Same between the two seat backs. Wing spar areas also supply cold air if not sealed.

Finally, I've observed that 90%+ of installations have the air flow through the heaters wrong - the cold air should come into the aft port on the heaters, so it goes in the opposite direction to the exhaust flow. This is heat exchanger 101 stuff. I can't say how much better it will be, but it will be better.
 
I have a heated vest that fits well under any coat or jacket and I must say that’s an idea worth considering. I haven’t had the need to fly with it yet (those days are coming, I’m sure), but I do wear it working in the hangar and outside on the tractor blowing snow. I have to say it’s pretty toasty for not much bulk. I get about 4-6 hours out of a fully charged battery pack.
 
The inside of a heat muff on bonanza looks like the the exhaust pipe has a shroud like a porcupine. There are lots of one inch spines the size of an AN3 bolt projecting from a tube around the pipe. Think of them as heat sinks. The location is on the exhaust pipe with all cylinders one one side feeding it instead of just one cylinder.

Thinking outside the box but why not make a heat sink and get much better heat transfer to the air. Take a piece of stainless and cut fins. Wrap it around the pipe and hold in place with some stainless clamps.
 
Thinking outside the box but why not make a heat sink and get much better heat transfer to the air. Take a piece of stainless and cut fins. Wrap it around the pipe and hold in place with some stainless clamps.

Not my idea, but these pics are from a post a couple of years ago. The person who posted said it worked great and made a big difference.

RV-heat-muff-2.jpeg

RV-heat-muff-1.jpeg
 
I was up this morning doing approaches at 16F and rudely reminded of the problem you describe.

I have a frigid breeze that comes around the seats from the back, and based on Scotts comments, believe it is indeed air being sucked out forward of the seat backs. I know that my tip-up rail on the right side sucks. it is about .030" from allowing the teardrop seal to work. Surely the aft corners are also players, but hard to fly and test that area.

I have used puffy yarn on a telescopic pointer to test, but it is more stiff than TP. That sounds like a good one to test too

I can feel warm air across the feet and side to side at the spar station. My hot air is restricted to a 1" hole, and have a single heat muff. I did wrap the heat muff exterior with fiberfrax and then with aluminum foil to keep the heat in - it helped.

I am considering opening my flow and adding another heat muff. Time to end the suffering

I used to fly a lot in the winter and the 2nd muff makes a big difference. I also attacked the side of the fuse at the spar attach area with foam and RTV, as well as boots for the push tubes. That helps a ton as you could feel a literal breeze moving in that area.

Larry
 
Not my idea, but these pics are from a post a couple of years ago. The person who posted said it worked great and made a big difference.

View attachment 34549

View attachment 34550

Almost exactly what I was thinking. I would put the fins on both sides and get 2 rows from each bolt on.

I would still use worm gear clamps to attach instead of bolts. For 10 bucks, you can get 7 feet of clamps and connectors and roll your own.

This is what I will do when it comes time.
 
Almost exactly what I was thinking. I would put the fins on both sides and get 2 rows from each bolt on.

I would still use worm gear clamps to attach instead of bolts. For 10 bucks, you can get 7 feet of clamps and connectors and roll your own.

This is what I will do when it comes time.

Appears that the hardware store worm drive clamps are only rated to 250 degrees, McMaster-Carr has them rated to 1200 degrees. Not sure what the physical differences are.
 
From Scott McDaniels

"Adding stainless steel pot scrubber pads to the heat muffs does help some as well".

This worked well for me, almost too hot.......:)
 
Muff improvement options

Copper has a thermal conductivity many times better than SS. Will it last 1 yr, 2yr ??
Any body tried it ?
 
"Adding stainless steel pot scrubber pads to the heat muffs does help some as well".

This worked well for me, almost too hot.......:)

Variable to consider. Physical contact with the hot surface for conductivity is essential. The goal is to increase the heat transfer surface area. The careful arrangement of the added SS wool would be very important. That not in contact with the aforementioned would have high resistance and limited effectiveness. It’s very easy to conceive a wide range of effectiveness for different applications.
 
thank you guys for all the inputs.

i had these steel scrubber pads inside the muff but replaced them with the soulution dave has shown. the one with the fins clamped around the exhaust pipe within the heat muff. but no success.

my original question in this thread was about the stream of incoming warm air... if it's somewhat strong or almost not noticable.

i still believe that the pressure loss in my heat system is so large that there's not enough remaining pressure left at the firewall. i checked with Vans and they suggested a device on top of baffle ramp's air inlet.

https://baspartsales.com/a903-1-a911-1-robinson-r22-cabin-heater-outside-air-inlet-w-scoop/

i will investigate that solution to increase the pressure at the beginning of heat system via ram effect. probably that would be more tinkering with the symptoms than curing the desease. :)

meanwhile i will get some electric seat heater from the next auto store. so the 12 V car socket i installed in the panel makes sense for the first time.
 
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Herzlich Gruss Kay. Hopefully you may have already checked this and ruled this out but we just found this out with our 2 year old RV-9. We have the stock Vans supplied heater valve at the firewall. We discovered that the sheathed cable control that we are using to control the valve did not have enough friction to hold the valve completely open to allow the maximum amount of heated air into the cockpit. If that valve is only left open a tiny bit, a large amount of heated air is bypassed at the valve and not routed into the cockpit. We discovered this by manually holding the control knob pulled full out and keeping pressure on it (asking for max heated air) and then feeling with a bare hand at the heated air entry point into the cabin. If you feel improved airflow, then work on a better control cable solution which will hold the valve in its full travel position. Also, make sure your control cable is rigged correctly and that the valve is able to travel to its designed extremes. Hope this may help.
 
thank you guys for all the inputs.

i had these steel scrubber pads inside the muff but replaced them with the soulution dave has shown. the one with the fins clamped around the exhaust pipe within the heat muff. but no success.

my original question in this thread was about the stream of incoming warm air... if it's somewhat strong or almost not noticable.

i still believe that the pressure loss in my heat system is so large that there's not enough remaining pressure left at the firewall. i checked with Vans and they suggested a device on top of baffle ramp's air inlet.

https://baspartsales.com/a903-1-a911-1-robinson-r22-cabin-heater-outside-air-inlet-w-scoop/

i will investigate that solution to increase the pressure at the beginning of heat system via ram effect. probably that would be more tinkering with the symptoms than curing the desease. :)

meanwhile i will get some electric seat heater from the next auto store. so the 12 V car socket i installed in the panel makes sense for the first time.

Could you perhaps post some pictures, particularly of the air intake?
 
Alex... here's a pic i found from the intake. the ramp should be inclined enough to provide sufficient pressure at the air inlet. on the other hand the intake is at the most inboard position and i wonder if this is too close to the spinner due to turbulences etc.

that raises the question if people with a better performing cabin heat (pronounced air stream) have their inlet in a more suitable position...?
 

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I used to fly a lot in the winter and the 2nd muff makes a big difference. I also attacked the side of the fuse at the spar attach area with foam and RTV, as well as boots for the push tubes. That helps a ton as you could feel a literal breeze moving in that area.

Larry

i did not address the spar attach to the fuse yet. good that you mention that, in a email reply from Vans tech support they highlighted to close that area with foam and stuff.
 
I have separate controls…cabin air and temp. My -9A cabin heat depends on some balance between the cabin air flow control and the cabin heat control. Best heat for me on a cold Minnesota day is black knob (cabin air) about 1/2 - 2//3 out and red knob (temp) all the way out, mixing max muff airflow with moderate cabin air flow. That gives me a nice warm airflow. I have some drafts as well but it helped to add a seal at the rear of the (slider) canopy on fuselage. It’s still draft enough that I can’t see cabin venting as improving anything. I can’t say that cabin heat has been a big problem for me, but just pulling out the heat control if the cabin air control is closed adds very little heat to the cabin.

i have to try that the next flight. what i've done yet was 0 or 1. maybe something intermediate is better.
 
It has been mentioned already but; the heat air intake was moved from the ramp to the backside of cyl 3 on the 8. Before I changed the profile on the inlet ramp, I'd strongly consider such a move. One is a simple extraction point that can be tried and easily eliminated. Changing the ramp profile can easily have other bad consequences and the work/rework would be much more than the other option. Just another thought.

I personally would determining if the (lack of) flow is a byproduct of restriction(s) or inlet design by temporarily bypassing/eliminating components in the path to determine their effects.
 
Alex... here's a pic i found from the intake. the ramp should be inclined enough to provide sufficient pressure at the air inlet. on the other hand the intake is at the most inboard position and i wonder if this is too close to the spinner due to turbulences etc.

that raises the question if people with a better performing cabin heat (pronounced air stream) have their inlet in a more suitable position...?

Hmmm, that could be the problem. I recall from eons ago that the airflow mis-behaves in those inner most areas behind the spinner. Someone did some oil drop tests and showed a reverse flow on the very inboard side, at least at the forward most location.

DanH should be by shortly to comment.
 
+1 for heated clothing

The heater output in my -9A (standard heater setup) is marginal at best. I've also got a ton of cold air being sucked into the cabin at all the normal locations. Slowly working on sealing all that up, but for now, we've solved the problem with heated vests. They really work, and the battery life is very long. Highly recommended.
 
The heater output in my -9A (standard heater setup) is marginal at best. I've also got a ton of cold air being sucked into the cabin at all the normal locations. Slowly working on sealing all that up, but for now, we've solved the problem with heated vests. They really work, and the battery life is very long. Highly recommended.

Which vests are you using? I've seen a million different models on Amazon, but hard to know if there is a trusted brand that won't catch on fire...
 
Good point . . .

Herzlich Gruss Kay. Hopefully you may have already checked this and ruled this out but we just found this out with our 2 year old RV-9. We have the stock Vans supplied heater valve at the firewall. We discovered that the sheathed cable control that we are using to control the valve did not have enough friction to hold the valve completely open to allow the maximum amount of heated air into the cockpit. If that valve is only left open a tiny bit, a large amount of heated air is bypassed at the valve and not routed into the cockpit. We discovered this by manually holding the control knob pulled full out and keeping pressure on it (asking for max heated air) and then feeling with a bare hand at the heated air entry point into the cabin. If you feel improved airflow, then work on a better control cable solution which will hold the valve in its full travel position. Also, make sure your control cable is rigged correctly and that the valve is able to travel to its designed extremes. Hope this may help.
You might be onto something here for the Vans design air door valve. I was shallow thinking when doing my 6 under-the-hood approaches and maybe did not pull my knob fully believing that it was not needed. This brings heat modulation to the front of the conversation with this design, but is something that has not come up in my memory of VAF.
 
Which vests are you using? I've seen a million different models on Amazon, but hard to know if there is a trusted brand that won't catch on fire...

I have an Ororo. It works great…better heat distribution than the other one I have (Milwaukee)…but I can’t recommend it as the Ororo battery requires it’s own (readily lost) special charger rather than the ubiquitous 5v USB chargers that everyone else seems to use. The Milwaukee uses the same 12v batteries that my tools use. Very convenient, but also very expensive compared to the multitude of “offshore” brands that litter Amazon.
 
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Heated vests etc.

Which vests are you using? I've seen a million different models on Amazon, but hard to know if there is a trusted brand that won't catch on fire...

My partner works in retail at a "if it ain't here, you don't need it" store JAX, a local and employee owned store. They are very selective as to what they sell, even to the point of not selling "well-known" brands as they are not up to their standards of quality apparel. They sell one brand of heated apparel: GOBI. I have heated sweatshirt and a vest. The vest has fabric similar to Carhart that I wear in the Cub (which basically has no heater and is rather drafty) and am very impressed with how it works. It has three levels of heat. Batteries are rechargeable and duration varies depending on what heat setting is being used. There are two sizes of battery pack, the larger one lasting longer, both still about the size of a deck of cards. She has a quilted vest and a sweatshirt. We like 'em!
 
I have separate controls…cabin air and temp. My -9A cabin heat depends on some balance between the cabin air flow control and the cabin heat control. Best heat for me on a cold Minnesota day is black knob (cabin air) about 1/2 - 2//3 out and red knob (temp) all the way out, mixing max muff airflow with moderate cabin air flow. That gives me a nice warm airflow. I have some drafts as well but it helped to add a seal at the rear of the (slider) canopy on fuselage. It’s still draft enough that I can’t see cabin venting as improving anything. I can’t say that cabin heat has been a big problem for me, but just pulling out the heat control if the cabin air control is closed adds very little heat to the cabin.

My findings have been the same. With cabin heat on and the eyeball vents partially open, I have excellent and even heat distribution. I don't care to speculate on the physics, I just know what works.

Chris
 
Vests

Ours are by Venture Heat, although I suspect a lot of the different brands have the same innards. I've got one that's quilted and one that is just fabric; I wear the latter under insulated coveralls on the very coldest days.

I've also discovered that the quilted one, worn under a good slightly insulated REI rain jacket, is a terrific cold season combo here in (admittedly mild) Virginia.

The Ace Copilot gets cold easily (while also hating bulky coats...) and she is REALLY happy with her heated vest. She declares it to be the best present I've ever gotten her.

Now let's talk hats. :) People lose a lot of heat through their heads. One great advantage of flying your own aircraft is that you can wear absolutely ridiculous hats with almost no chance that anyone will see you. This is an underappreciated bonus! Meanwhile, in-ear headsets let you cover the ears completely....

Yup, you smart people out there recoiling in fashion horror, you guessed it: I'm now recommending use of the FULL ON ELMER FUDD HAT.

I'm telling you, Elmer was on to something!!!! Recall also that Uncle Sam issued them to aircrew (see: Carter in "Hogan's Heroes"). The things are just awesome. Total warmth and extra noise canceling!! You can also get them with ridiculously long bills for those sunset and sunrise flights.

Obviously, the last item in my pre-crash checklist is to remove my hat, as I literally would not want to be caught dead wearing it.

Okay I'll stop now.

Which vests are you using? I've seen a million different models on Amazon, but hard to know if there is a trusted brand that won't catch on fire...
 
For the price of a box of screws, you can practice your welding skills.
 

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Webb, that looks like the AWI produced enhancement for HX. Did you make the end plates too? My AWI system has the "screws" resistance welded to the tube, but is still limited by the internal surface transfer coefficient.

A few questions -is this an inserted piece in the system? - are the studs inserted and welded or just sitting on the surface then perimeter welded?

Showoff - -:D
 
When I replaced the engine on my Bonanza, new mufflers were needed. This is a picture from the inside the heat muff. BTW, the muff is about 5” in diameter. No showing off here, not my work. I just had to write the check….

To me, it looks like the screws are welded on a larger tube and held in place by recess in the end caps. IF I were doing this for the RV, I would braze screws on a flat sheet and then wrap the pipe and bolt for best heat transfer.
 
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