Heat in the cockpit - or lacking heat in the cockpit!

I posted about a trip we made where my wife and I froze but didnt want to get off topic on the weekend thread. We were so cold we had to land to warm up. My carbon monoxide detector said it was 21 degrees inside. We warmed up at the airport, found a hole in the clouds and were in sunshine the rest of the trip warming up to about 60 in the cockpit. Thanks for the responses. I am open to suggestions!

I have an old Vans made exhaust with the loaf of bread heat muff. It does not do the trick.

I spoke to Larry V and Clint about it a couple years ago and Clint said he could modify my exhaust so I could add another heat muff. I tried to contact him but no luck. The construction picture shows what I have.

Both my wife and I had heated vests on, she had a blanket and scarf. Next time we will wear ski outfits.

Sealing the canopy. On my tip up, I increased the width of the skirt to overlap the joint to match up with the other panel lines. I also have weatherstripping on the inside. I taped over the air vents on the outside so no air could leak in. My daughter is making me the aileron boots and Im sure that will help. Im thinking of adding carpet under the seats and on the floor around the seats to help both with sound and heat. I have carpet in the baggage area but nothing on the back bulkhead. Im sure air leaks around and under the bulkhead.

I had Abby install seat heaters when she did my seats but had not wired them up. I have been doing that the past 2 days. Im thinking of getting a 12v portable heater to see if that helps.

Question - has anyone put fiberglass or another insulation under the floor panels? Any other ideas on how to get more heat? Im ready to get a new exhaust system with 2 muffs if needed.

Any other ideas?

My wife and I had a nice trip and I dont want to lose her as a passenger.

Turbo heat muffs are pretty nice.. sold on spruce, made by a hangar neighbor, Dave, here in Las Vegas

I have a newly finished and flying RV-9A with a Vetterman exhaust and a heat muff on the right exhaust side. I have quite the opposite problem, TOO much heat. I can’t stand to pull more than 1/4-1/2" on the heat cable knob or I will get roasted out of the cockpit. Last month a put a restriction down to 3/4" opening behind the #3 cylinder baffle where air flows through the tubing down to the heat muff. This was in an effort to limit the amount of heat.

Side note, I have an engine stumble issue below 1,000 rpm’s after the cowl warms and I suspect it’s due to dumping heat off the firewall heat valve back into the lower cowl and heating up the mech fuel pump, etc.

My RV-9A is HOT !

Any other ideas?..

I have a dedicated air supply to my oil cooler and have been experimenting with an automotive type radiator cooling fan. Seems to me that 190 degree air can be used for cabin heat. Hot, high volume and untainted by any possible exhaust leaks. Haven’t tried it yet but I’m heading in that direction.

Biggiesauls said:

I have a newly finished and flying RV-9A with a Vetterman exhaust and a heat muff on the right exhaust side. I have quite the opposite problem, TOO much heat.

.....[snip...............

My RV-9A is HOT !

Click to expand...

Same here, RV-9A...can't pull the red heat knob more than about halfway. I do have a draft somewhere under the panel but even it's never been enough of an issue or made the cockpit cold enough to stimulate me to track it down. Very curious to know what's up with OP's airplane.

rmarshall234 said:

I have a dedicated air supply to my oil cooler and have been experimenting with an automotive type radiator cooling fan. Seems to me that 190 degree air can be used for cabin heat. Hot, high volume and untainted by any possible exhaust leaks. Haven’t tried it yet but I’m heading in that direction.

Click to expand...

I heard this has been tried, and only marginally effective, so they abandoned it..

rockwoodrv9 said:

I spoke to Larry V and Clint about it a couple years ago and Clint said he could modify my exhaust so I could add another heat muff. I tried to contact him but no luck. The construction picture shows what I have.

Both my wife and I had heated vests on, she had a blanket and scarf. Next time we will wear ski outfits.

Sealing the canopy. On my tip up, I increased the width of the skirt to overlap the joint to match up with the other panel lines. I also have weatherstripping on the inside. I taped over the air vents on the outside so no air could leak in. My daughter is making me the aileron boots and Im sure that will help. Im thinking of adding carpet under the seats and on the floor around the seats to help both with sound and heat. I have carpet in the baggage area but nothing on the back bulkhead. Im sure air leaks around and under the bulkhead.

I had Abby install seat heaters when she did my seats but had not wired them up. I have been doing that the past 2 days. Im thinking of getting a 12v portable heater to see if that helps.

Question - has anyone put fiberglass or another insulation under the floor panels? Any other ideas on how to get more heat? Im ready to get a new exhaust system with 2 muffs if needed.

Any other ideas?

My wife and I had a nice trip and I dont want to lose her as a passenger.

Click to expand...

The bulkhead is corrugated. It will leak cold air if you don't block the sides. Also, there is a leaky area around the flap rods.

A 12 volt heater will not give out enough btu's. You don't have enough current capacity. A 100A alternator running at 100% would only produce about 4600 btu..... You need about 15 to 20,000 btu.

rmarshall234 said:

I have a dedicated air supply to my oil cooler and have been experimenting with an automotive type radiator cooling fan. Seems to me that 190 degree air can be used for cabin heat. Hot, high volume and untainted by any possible exhaust leaks. Haven’t tried it yet but I’m heading in that direction.

Click to expand...

In cold weather we have to take steps to keep the oil warm enough. When you most need heat in the cockpit is the same time when there's no spare heat in the oil.

My former hangar partner had "oil cooler heat" in his RV8A - he darned near froze when cruising at altitude... in the summer!

In our Glasair Sportsman the O-360 exhaust is a typical "Cessna-style" unit, complete with a muffler located cross-wise beneath the engine. The outside of the muffler is wrapped in stainless sheet material - this is the heat muff. Some builders complained the cabin wasn't warm enough. I looked at the 1.5" ducting and thought the muffler/muff could produce more heat if it wasn't choked up by the limited flow capacity of the 1.5" duct and cabin heat valve. I up-sized everything to 2". So far I haven't been able to fly with the cabin heat set to max - even in -15C weather. At the freezing point I'm running the cabin heat control at about 10% capacity.

Having excess heating capacity is a huge comfort when flying. The size of the ductwork and the cabin heat valve, thus the flow capacity of the system, are considerations of equal importance to those around the heat muff itself.

I have found that the drafts are what really make it cold. Sounds like you have addressed many. Besides what you have already done, I have put foam in the landing gear leg fairings up near the top under the fairing to the fuselage. Also added some Go-Fast tape around the upper intersection fairing as over the 16 years of flying they have warped a bit and no longer fit as nice as when new. That helped. I also put a strip of foam weatherstripping on top of the spar all the way across to seal any additional leaks under the floor from the gear legs and aileron push tubes.
The main one to get sealed is the back edge of the canopy. air just sucks in there and blows on the back of your neck. Burrrr!

My experience is the same as plehrke and found most heating issues on my-8 to be related to leaks and drafts. When I was living back west in the mountains no amount of heat helped when cold air is blasting in from all angles. I used speed tape, pushrod boots, and weatherstripping on the canopy to cut down on the drafts. To add the amount of heat coming in I added a turbo muff in series with the stock Vans muffler. This dramatically increased the temp of my incoming heated air. With the addition of seat heaters I’m very comfortable in the middle of the winter now.

Aileron pushrod boots

If you are getting air from the bottom of the stick you can add aileron pushrod boots. They are attached with velcro to the fuselage inside and you can install them on a finished plane. With your seat out it would take less than an hour to do both. Those eliminated all the air from below in my RV4. Vendors here sell the kit and it is not expensive.

This topic is one that has thousands of posts on this forum, with dozens of threads. If you put this in a search, you'll be busy reading for quite a while.

cabin heat site:vansairforce.net

It would be helpful to know more about the specifics of your system. I cannot tell anything from your picture.

It is also worthwhile to weigh much more heavily those posts from folks who live in the north. Heating against OAT's of 30F is notably different from OAT's of 0F.

My top things, about the same priority:
1. Too much airflow through the heater. I have one heater with a 2" inlet behind #3 which is almost entirely blocked. The other heater is supplied from a 1.5" scat on the #2 inlet ramp, also 75% blocked. I think a 1" scat would be adequate, and will test one of these years...
2. Almost every RV I've seen utilizes co-current flow, meaning the exhaust and air travel through the exchanger in the same direction. Use counter-current flow - you'll get more heat. This is heat exchanger 101.
3. Heaters do much better on the tailpipes fed by 2 cylinders as opposed to those on the crossovers, which are only 1 cylinder.
4. Stuff a towel between the seat backs and the fuse wall, continuing it all the way forward of the spar carry through.

I’ve used recycled foam board wall calendars as a basis for sidewall insulation…. Glue carpet on the passenger side and a couple parches of Velcro on the other and just stick it to the sidewall. In or out in seconds. Very effective. It’s also flammable, so use at own risk.

Also, heated clothing (vests, insoles, sockets, etc) are very light, require little mods to the airplane (or none, if battery powered), present no risk of carbon monoxide poisoning, and are relatively inexpensive. Also very effective.

I have no other heating systems in my airplanes. If I get one with a heat muff, it comes off and the hole in the firewall is riveted shut.

Cold cabin

Sleeves or pant legs from clothing makes good boots for the aileron push tubes.

Here's what works for me flying year round in Wisconsin. 0* OAT not a problem.

Heated seats.
TWO heat muffs in series, NOT using the crossover pipes.
Stuffed the inside of the muffs with steel wool.
Aileron push tube boots.
Good weather stripping around the tip up.

Cabin heat........

AlexPeterson said:

It is also worthwhile to weigh much more heavily those posts from folks who live in the north. Heating against OAT's of 30F is notably different from OAT's of 0F.

My top things, about the same priority:
1. Too much airflow through the heater. I have one heater with a 2" inlet behind #3 which is almost entirely blocked. The other heater is supplied from a 1.5" scat on the #2 inlet ramp, also 75% blocked. I think a 1" scat would be adequate, and will test one of these years...
2. Almost every RV I've seen utilizes co-current flow, meaning the exhaust and air travel through the exchanger in the same direction. Use counter-current flow - you'll get more heat. This is heat exchanger 101.
3. Heaters do much better on the tailpipes fed by 2 cylinders as opposed to those on the crossovers, which are only 1 cylinder.
4. Stuff a towel between the seat backs and the fuse wall, continuing it all the way forward of the spar carry through.

Click to expand...

Front Range of Colorado. Field elevation: 5119. SuzieQ: RV-4 with a very well-sealed canopy. No push rod boots but fuel lines etc are sealed and stick boots help. Heater: counter-current flow from heat muff with steel wool inside covering most of the two exhaust pipes from cylinders 1 and 3. Air pulled from the back baffling, partially heated by the cylinder heat (yeah, I know: air pulled from the baffling has been previously discussed ad nauseum.) Stainless airflow box controlled from the cockpit with 2-inch hot air entrance just above my right rudder. In the compactness of the -4 cockpit, I usually have to shut it off a little. I'll leave it open if I have a passenger. More than adequate after Winter Solstice (which is today, by the way!). Heater is never blocked off in the Summer and hot air is dumped laterally away from the firewall. I built a heater outlet for the back seat but couldn't figure out an efficient way to get heated air around the spar.... Stays pretty warm back there anyway.

As with any Winter activity, dress for the part. I have base layers under my flight suit, a GOBI heated vest and a Winter Nomex jacket.

YMMV..........

Taltruda said:

Turbo heat muffs are pretty nice.. sold on spruce, made by a hangar neighbor, Dave, here in Las Vegas

Click to expand...

Can you send me contact info or a link? Thanks

AlexPeterson said:

This topic is one that has thousands of posts on this forum, with dozens of threads. If you put this in a search, you'll be busy reading for quite a while.

cabin heat site:vansairforce.net

It would be helpful to know more about the specifics of your system. I cannot tell anything from your picture.

It is also worthwhile to weigh much more heavily those posts from folks who live in the north. Heating against OAT's of 30F is notably different from OAT's of 0F.

My top things, about the same priority:
1. Too much airflow through the heater. I have one heater with a 2" inlet behind #3 which is almost entirely blocked. The other heater is supplied from a 1.5" scat on the #2 inlet ramp, also 75% blocked. I think a 1" scat would be adequate, and will test one of these years...
2. Almost every RV I've seen utilizes co-current flow, meaning the exhaust and air travel through the exchanger in the same direction. Use counter-current flow - you'll get more heat. This is heat exchanger 101.
3. Heaters do much better on the tailpipes fed by 2 cylinders as opposed to those on the crossovers, which are only 1 cylinder.
4. Stuff a towel between the seat backs and the fuse wall, continuing it all the way forward of the spar carry through.

Click to expand...

Thanks for the link. I dont know how I missed that thread.

I am wondering if I am getting enough air through the system. I am considering a small scoop on the inlet to take a little more air. I will have to get one of my grandsons to crawl down under the dash while I am doing a run up to see if the air is hotter and how well it flows.

I am going to put a 3" Targa cover over the canopy roll bar so it seals the back connection. It will also fix a broken spot that I am not sure how happened but air is coming in through the hole.

I got the seat heaters hooked up today and will give them a try tomorrow. They are good enough for this winter but I want to change how they are wired.

I think I am going to have to get another muff and modify the exhaust system to make a huge difference. Or move away from the north pole. I attached a couple more pics showing the system. It was purchased from Vans but it is not as good for heat at the Vetterman system.

Thanks for the help.

Rocky I hear you. I was freezing my rear for years. Then my Canadian friend suggested a second heat muff, a good buddy from Maryland fabricated two and brought me one. Works like a charm even in the coldest of weather when you feel the control surfaces lost all the play. In addition a full interior and heated seats will make the cockpit very comfy.

PS Thanks for sharing the trip I am a bit jealous

Rocky,

I'll try to sum up our differences.

RV-6A slider vs tip up
Warm inside at 11,500' on an overcast winter Utah day in a light jacket no gloves, and the heater knob pulled halfway out.
Air intake with bug screen on rear baffle vs cowling intake. I suppose the intake air to the heat muff is much warmer coming from on top of the engine.
Single heat muff on right side exhaust. (Carb heat on crossover gives minimal heat rise on intake on runup; haven't measured rise while airborne.)
Air infiltration control: Aileron pushrod boots, weatherstripping on spar entry openings, and flap rod openings. No sealing on baggage bulkhead.
Insulation: Carpet on floor forward of the seats, 1/8" self adhesive foam from AS on the sidewalls, and a moving blanket on the baggage bin floor (I fly dogs with PnP.)

What size scat is that feeding the heat muff and cockpit? 3"? It may be passing so much air that it only gets minimally warmed on its trip through the heat exchanger. My scat is probably 2".

AlexPeterson said:

This topic is one that has thousands of posts on this forum, with dozens of threads. If you put this in a search, you'll be busy reading for quite a while.

cabin heat site:vansairforce.net

It would be helpful to know more about the specifics of your system. I cannot tell anything from your picture.

It is also worthwhile to weigh much more heavily those posts from folks who live in the north. Heating against OAT's of 30F is notably different from OAT's of 0F.

My top things, about the same priority:
1. Too much airflow through the heater. I have one heater with a 2" inlet behind #3 which is almost entirely blocked. The other heater is supplied from a 1.5" scat on the #2 inlet ramp, also 75% blocked. I think a 1" scat would be adequate, and will test one of these years...
2. Almost every RV I've seen utilizes co-current flow, meaning the exhaust and air travel through the exchanger in the same direction. Use counter-current flow - you'll get more heat. This is heat exchanger 101.
3. Heaters do much better on the tailpipes fed by 2 cylinders as opposed to those on the crossovers, which are only 1 cylinder.
4. Stuff a towel between the seat backs and the fuse wall, continuing it all the way forward of the spar carry through.

Click to expand...

I didn't build my airplane (as you know) so I've never really had to understand airplane heat design. I note that mine has a mixer valve on the firewall with outside air sourced from two different intakes...one is direct from the outside and the other routes through the heater muff. Inside, I have a cabin air knob and a heat knob. I note, for reasons I don't know, that I get far more heated air if I open both cabin air and cabin heat than if I open cabin heat. Beyond that, I'm unclear on the details...I only know that my airplane cockpit is toasty warm here in the winter skies of Minnesota and I'm grateful for that. I don't want to have to bundle up in the cockpit, and I'm glad I don't have to. Rocky's description of his frozen flying reminds me of winter flying the local CAP squadron's Cessna 172XP.

..

not cabin heat related but what's your feel?

I know this is not related to cabin heating.
but has anyone noticed that the air box inlet is way too small?
this could be an engine inlet issue, or am I just seeing things funny?

rvator10 said:

I know this is not related to cabin heating.
but has anyone noticed that the air box inlet is way too small?
this could be an engine inlet issue, or am I just seeing things funny?

Click to expand...

Looks normal to me..

rockwoodrv9 said:

!

I have an old Vans made exhaust with the loaf of bread heat muff. It does not do the trick.

Click to expand...

I have the first one ever built which was installed on my airplane for initial testing and it is still in use.
It performs very well, but I have done the necessary work to prevent cold outside air from entering the cockpit.
As others have already mentioned… you can have the best heat muff system that money can buy but if you are leaking 20 deg F air into the cockpit, it will never warm up.
I would bet money that the majority of your problem is cold air leaking in. The tricky part about solving it is the cause is often because interior air is being sucked out which will always cause ( in this case, cold) makeup air to come in to replace it.

Scott,
Is this the same exhaust system you have? I think I have done pretty good with air leaks. My side skirt overlaps the rail by about an inch and I sealed up around the back bulkhead. I taped off the fresh air vents outside so no leaks in the vents. I dont have the side boots installed yet and Im sure that will make a big difference. I just dont feel much hot air coming in through the vent. I am thinking of adding a small scoop inside the plenum fresh air intake to get more air but not sure it will help.

I had my cowl off today looking for a place to put additional muffs and dont see anywhere that would work. I have a 60 amp alternator and may hook up a circuit for a 12 v portable car heater. If Im going to get my wife back in the plane in the winter I need to get something figured out.

rvbuilder2002 said:

I have the first one ever built which was installed on my airplane for initial testing and it is still in use.
It performs very well, but I have done the necessary work to prevent cold outside air from entering the cockpit.
As others have already mentioned… you can have the best heat muff system that money can buy but if you are leaking 20 deg F air into the cockpit, it will never warm up.
I would bet money that the majority of your problem is cold air leaking in. The tricky part about solving it is the cause is often because interior air is being sucked out which will always cause ( in this case, cold) makeup air to come in to replace it.

Click to expand...

rvator10 said:

I know this is not related to cabin heating.
but has anyone noticed that the air box inlet is way too small?
this could be an engine inlet issue, or am I just seeing things funny?

Click to expand...

This is a better picture of the carb intake as finished.

Rockwood,
As far as getting hotter air with the same setup, I believe Alex mentioned it earlier and forgot I had done the same…….
Use some duck tape to block off 1/2 the inlet to your heat muff and see if that gets the air warmer. I ended up using RTV to block off about 2/3 of the inlet to my heat muff.
Side skirts overlapping may not be enough, with a bare hand can you feel cold air anywhere along the sides of the canopy in flight? If so it needs a seal.
Much harder to feel in flight is the forward canopy skirt, flown a couple tipups that leaked so much cold air in through the front canopy skirt it completely negated the heater.
Good luck!

A other cold -9A

My 9A is in the same category as his: cold! In my case I think it’s uncontrolled drafts from the sides and back of the (slider) skirt, and through the pushrod holes. I added some copper wool and exhaust wrap to my heater muff and got some improvement, but the drafts seem to be the primary culprit. Next project is boots.

The gaps in my canopy sides are large enough that I once lost a sunshade due to the suction! It made an awesome noise as it exited the cabin. I imagine some farmer watching it flutter to the ground and wondering about it…

MacCool said:

Same here, RV-9A...can't pull the red heat knob more than about halfway. I do have a draft somewhere under the panel but even it's never been enough of an issue or made the cockpit cold enough to stimulate me to track it down. Very curious to know what's up with OP's airplane.

Click to expand...

Dugaru said:

My 9A is in the same category as his: cold! In my case I think it’s uncontrolled drafts from the sides and back of the (slider) skirt, and through the pushrod holes. I added some copper wool and exhaust wrap to my heater muff and got some improvement, but the drafts seem to be the primary culprit. Next project is boots.

The gaps in my canopy sides are large enough that I once lost a sunshade due to the suction! It made an awesome noise as it exited the cabin. I imagine some farmer watching it flutter to the ground and wondering about it…

Click to expand...

I get a draft coming from somewhere under the panel. It's not terribly intrusive so I haven't really spent any time tracking it down. I have boots on the pushrods and I suspect the draft/drafts are coming from fuel line and wiring pass-throughs. At one time I did have a draft from the back, which I solved by putting some fuzzy-side velcro around the underside to the rear canopy skirt to act as low-profile weather stripping The (slider) canopy side-skirts are probably leaking a bit too, but not enough to prioritize. I do have small leaks from my eye-ball vents.

My -9A's cockpit isn't roomy enough to wear Minnesota-level winter clothing so I was pleasantly surprised the first time I flew the plane in 0° F temps finding out that the cockpit was warm enough that I only needed a standard winter jacket, gloves aren't usually necessary after the cockpit is at temp -- fortunate because my shooting gloves don't work well with touch screens. I do have a Hornet cockpit heater on the same cell-phone switch as my Rieff pre-heater, which is nice for getting in to a nice warm cockpit with warm seats/warm foam before starting the engine. The pre-heater means that it's blowing warm air immediately.

Good tips

Going to try the fuzzy velcro approach for the rear of the skirt.

What did you install for canopy side skirts? Currently my canopy sides function as open windows, basically.

My plastic eyeball vents have always leaked. Some day I'll spring for the aluminum one$. In the meantime, in the winter I just cap them with flexible plastic pipe caps.

I have had great results using battery-heated vests. The Ace Copilot declares it's the best gift I've ever given her. Usually enough to keep things warm in the daytime, but whooboy, when that sun goes down...

MacCool said:

I get a draft coming from somewhere under the panel. It's not terribly intrusive so I haven't really spent any time tracking it down. I have boots on the pushrods and I suspect the draft/drafts are coming from fuel line and wiring pass-throughs. At one time I did have a draft from the back, which I solved by putting some fuzzy-side velcro around the underside to the rear canopy skirt to act as low-profile weather stripping The (slider) canopy side-skirts are probably leaking a bit too, but not enough to prioritize. I do have small leaks from my eye-ball vents.

My -9A's cockpit isn't roomy enough to wear Minnesota-level winter clothing so I was pleasantly surprised the first time I flew the plane in 0° F temps finding out that the cockpit was warm enough that I only needed a standard winter jacket, gloves aren't usually necessary after the cockpit is at temp -- fortunate because my shooting gloves don't work well with touch screens. I do have a Hornet cockpit heater on the same cell-phone switch as my Rieff pre-heater, which is nice for getting in to a nice warm cockpit with warm seats/warm foam before starting the engine. The pre-heater means that it's blowing warm air immediately.

Click to expand...

Dugaru said:

Going to try the fuzzy velcro approach for the rear of the skirt.

What did you install for canopy side skirts? Currently my canopy sides function as open windows, basically.

My plastic eyeball vents have always leaked. Some day I'll spring for the aluminum one$. In the meantime, in the winter I just cap them with flexible plastic pipe caps.

I have had great results using battery-heated vests. The Ace Copilot declares it's the best gift I've ever given her. Usually enough to keep things warm in the daytime, but whooboy, when that sun goes down...

Click to expand...

My side skirts don't have anything on them in the way of weatherstripping - they fit pretty snug. The eyeballs are aluminum. Capping them is a great idea. The OB of my plane was really a meticulous guy and the previous owner (guy the OB sold it to) was also quite comprehensive in his attention to maintenance and upgrades. However, I do note that flight, pressures on the canopy do make it leak more. It would probably be a good idea to seal the sides a little and I'm guessing I'd just use the same velcro. That said...the drafts are minor and haven't been intrusive enough for me to be very aggressive in addressing them.

Side skirt

When I had to re-do the foreskin I also extended the site skirts to match the other skin lines. It overlaps the rail by about an inch. Im sure it cuts down the air leaks and I have weatherstripping inside on the rail. The first picture the canopy is not latched so it is up a bit.

rockwoodrv9 said:

Scott,
Is this the same exhaust system you have? I think I have done pretty good with air leaks. My side skirt overlaps the rail by about an inch and I sealed up around the back bulkhead. I taped off the fresh air vents outside so no leaks in the vents. I dont have the side boots installed yet and Im sure that will make a big difference. I just dont feel much hot air coming in through the vent. I am thinking of adding a small scoop inside the plenum fresh air intake to get more air but not sure it will help.

I had my cowl off today looking for a place to put additional muffs and dont see anywhere that would work. I have a 60 amp alternator and may hook up a circuit for a 12 v portable car heater. If Im going to get my wife back in the plane in the winter I need to get something figured out.

Click to expand...

Yes, that is the same heat muff I have.

If you don't even have boots on the aileron push rods yet... you haven't yet done pretty good with air leaks.

As I have written in the past, sealing up the baggage bulkhead is not a solution.

If you want new air (fresh air vents or cabin heat) to come in to the cockpit, there has to be a way for interior air to get out.
The air supplied from the heat valve or the fresh air vents is at a very low pressure delta to what the pressure is within the cockpit... it will not push much air out if there is not an easy path for it to take.

So if an RV actually has all of the potential air leaks sealed up sealing the baggage bulkhead will actually hurt the cabin heat and fresh air vent performance.

The best way to approach this problem is to find were unwanted air is coming in and / or going out.

A good way to do this is cut a bunch of strips of toilet paper 3/4" to 1" wide and 6 inches long. Take some tape, a 24" long stick, and a friend, and go fly. While you let your friend fly, tape strips to the end of the stick and move it to different places around the cockpit and look for air movement. When you find places where air is sucking out, it will often times suck the paper right off of the stick (that is why you brought extra and a roll of tape).

A commonplace for outflow air is anywhere around the canopy (regardless of what you think yo may have done there to this point). This is because there is so much convexed shape on the outside of the canopies, there are a lot of locations around the canopy that there is lower pressure just outside of where the canopy interfaces with the fuselage (think top surface of a wing). Particularly on side by side RV's with a tip-up canopy.

Once you see what locations have airflow coming in or out, you can work to correct those locations.
Just keep in mind that it is a balancing act. The goal is to seal as well as possible but still have an outflow path (preferably at the back so that heater air moves that direction) that will allow the low pressure air from the heat valve be the primary inflow source.
If you are able to achieve that, the heat muff system you have now will probably be sufficient.

After thought... There is nothing wrong with trying to make the heat muff system perform better, but if you have a rapid air exchange happening in the cockpit because of air leaking out and in, it doesn't matter if you have the best in the world, it will not be able to counter having 20 F air flowing into the cockpit.

Second after thought.... Because a lot of the air that comes in, is the result of it being make-up air for air that is being sucked out, the use of flexible "V" type seals at the outflow locations is a good solution. If the are installed appropriately, any air trying to flow out (usually at a slightly higher pressure which is why it is doing so) will push an the movable flange of the seal and make it seal even harder.

Thanks Scott. I appreciate the info. I like the idea of tp on a stick to check where air is coming from. I will give that a try. My daughter is making the boots for me so I will get them installed as soon as she gets them to me. Im sure that is a huge source of the cold.

Interesting thought on sealing the back bulkhead. It sounds like I am making it worse sealing it off.

One other place I think more air than I thought comes from is the front of the tip up. I dont fly in rain so I dont know how bad it leaks but I plan to put some tape over the joint on the top portion to at least cut about 60% of the joint. I hope that helps too.

I have read mixed results from filling the muff with stainless or copper scrub pads but I may give that a try.

The other item that caught my eye yesterday when I took the cowl off is the cold air inlet inside the air intake is on an upslope because of my plenum. I thought I may need a scoop to get more air but now I am thinking I may be getting too much air into the heat system. I will try reducing the opening and see if I get less but hotter air.

Been flying for 4 years and sealing leaks as I find them, but my heat also works Ok, but would like it to be better. Standard heat muff on the right side exhaust attached to the rear of #3 baffle. Yesterday I captured some data on the heat coming into the airplane and where cold air is flowing.

OAT was 41F and it was 47 in the cabin on engine start. I place a "Meater" temp probe into the fins where the air comes in through the firewall. That also measured 47 degrees.

After warming the oil and doing the run up the cabin was 52F and the heat coming in through the firewall was 128F.

All this is with the heater control full open.

Shortly after takeoff while still climbing to 3,000 the air entering the cabin was 144F and the cabin was 52F. Full throttle really makes more heat for sure.

After takeoff and level at 3,000 the air entering the cabin was 153F, cabin was coming up to temp at 73F, but that's a drafty 73 as it still felt cold in areas.

What I can't tell is the amount (flow) of air coming in at 150+F. It did not feel like my feet were roasting so I am thinking not enough flow because if my feet were that hot I'd feel it.

I also had a stick with paper mache strips and found the rear baggage bulkhead leaking profusely where the ribbed areas are. I also measure the temp of that air using an instant read thermometer and it was below 50F, essentially outside air temp so I'm thinking it's coming into the cabin. For those who say to not seal the baggage bulk-head, why is that? If air will never flow from the cabin rearward through the baggage bulkhead due to air pressure differences why wouldn't I want to seal that cold air coming forward?

I also have air leaking from the forward canopy slide rails (slider) where the outside skin covers that area. I couldn't really tell if this air was coming in or flowing out in that area. If if I touch under the rails here it does feel cold so I'm thinking the air is coming in.

I think my next step is to try reversing the flow on my heat muff so the fresh air enters the rear and exists the front. Seems logical that this should result in hotter air coming out because the heat muff should be hotter in the front than the rear.

I am also going to try to better seal the side rails and maybe the rear bulkhead at some point. Just trying to not make too many changes at one time.

I already have the wing spars at the fuselage sealed and have aileron push boots. I do have air leaking through the fresh air vents, but not very much.

What ideas are out there to force a higher volume of the hot air through the firewall? Any way to measure flow there?

dbaflyer said:

I also had a stick with paper mache strips and found the rear baggage bulkhead leaking profusely where the ribbed areas are. I also measure the temp of that air using an instant read thermometer and it was below 50F, essentially outside air temp so I'm thinking it's coming into the cabin. For those who say to not seal the baggage bulk-head, why is that? If air will never flow from the cabin rearward through the baggage bulkhead due to air pressure differences why wouldn't I want to seal that cold air coming forward?

Click to expand...

I already explain that for every cubic inch of air that comes in, there Hass to be a cubic inch of air going out.
If you have air coming in through your heat vents and profusely coming in through the openings in the baggage bulkhead, there has to be a lot of air going out somewhere else.

Your goal needs to be finding those other out locations and stop that flow.

If you do that, then the only out path is around the baggage bulkhead and the cabin heat or fresh air vent air will use that path to go out, instead of cold air coming in.

I have written about this story before, but I guess I will do it again, because many probably have not ever seen it.

Many years ago when the RV 10 prototype was very new and hadn’t yet matured to its final design configuration, I was riding as a passenger in the backseat, returning home from a flyin. It was my first time riding in the back. We had made an early morning departure and were flying high so the outside air temp was very cold. The cabin heat was turned on full blast, and the two people in the front seats were comfortably warm wearing just a tee shirt. I was shivering in the back, even though I was dressed pretty warmly.
I was able to detect that a lot of cold air was coming in around the baggage bulkhead. I understand airflow physics enough to know that for that to happen air must be going out somewhere at a pretty rapid rate.
I began searching for that path.
It didn’t take me long to discover that because of the longitudinal curvature of the fuselage side, the low pressure on the outside was sucking the bottoms of the doors outward, causing enough of a gap that the seal was no longer touching the door, allowing a large volume airflow to move from the high-pressure side within the cockpit, to the low pressure area just outside the door.
I was able to get my travel bag out of the baggage area and pull some loose clothing out which I tossed forward along the base of both doors. It immediately sucked onto the bottom of each door and basically plugged the flow path.
Within two minutes, I was stripping off all of my extra clothing and was sitting there in a T-shirt, very comfortable, just like the guys in the front seats.
After a short time, I was even asking them to turn down the cabin heat flow.

Once a final kit, version of doors was installed, which were much stiffer, this problem, no longer existed, but the story does a good job of explaining what I am trying to convey.

Following along with Scott’s post, the front hinge gaps are a huge air exit if they aren’t well sealed. Mine aren’t sealed well and the vacuum is strong enough to hold my phone or billfold in place to seal the opening. (Probably not my long term solution. ;-)

Very good info here. Thank you Scott and others.

I agree, great thread. I just did a flight where I felt I needed cabin heat for the first time, and found that even fully open it kind of works but isn't doing a great job. The heat muff is built per plans so it's likely not that. I love the idea of toilet paper on a stick to look for airflow. That's the first step I'll be taking.

Seal

I will be going though these during final assembly. Any missed?
Aileron push rod boots
Baggage bulkhead seal
Flap pushrod seals
Rear spar carry through seal

Has anyone a good solution to sealing the baggage bulkhead? Maybe some of that window weather stripping in each corrugated cavity?
I found the original aileron boot template.
Finally, there's the flap actuator rod holes. How did you seal those? That flap rod moves all over the place.
Rear spar carry through may be tricky.

wirejock said:

I will be going though these during final assembly. Any missed?
Aileron push rod boots
Baggage bulkhead seal
Flap pushrod seals
Rear spar carry through seal

Has anyone a good solution to sealing the baggage bulkhead? Maybe some of that window weather stripping in each corrugated cavity?
I found the original aileron boot template.
Finally, there's the flap actuator rod holes. How did you seal those? That flap rod moves all over the place.
Rear spar carry through may be tricky.

Click to expand...

I guess you haven’t read all of the thread…. If you do carefully seal up every pathway, where do you plan to have air exit so that cabin heat or vent air can come in?

Exit air

rvbuilder2002 said:

I guess you haven’t read all of the thread…. If you do carefully seal up every pathway, where do you plan to have air exit so that cabin heat or vent air can come in?

Click to expand...

Yes, I always read every post. Doesn't mean my thick brain understands!
Please give direction. If I'm in Left Field, now is the time to bring my dumb brain Infield.