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Weak cabin heat?

rdrcrmatt

Well Known Member
We purchased our plane flying, almost finished. Sorry in advance for my ignorance, I'm sure this is a simple problem I'd understand better had I built the plane.

Our cabin heat is really weak. In 0?F OAT we see our breath with the cabin heat on full in front and rear. The rear seats are worst than the fronts.

We have interior, but it's still in boxes. (side note, sorry Jesse Saint, I have your seat covers out of the plane but I forgot to send them. I'll do that this week!!) I'm waiting till spring to do the interior install, so I know that will help. Our door seals are okay, but I do have some cold air coming in front of the right door in addition to the normal leak by the door struts.

That all being said, I'm not convinced air leaking out is main problem. While I'm sure it's leaking a TON, the actual heat coming out the vents is barely lukewarm.

The heat muff intakes were partially covered, I've took care of that.

I checked that the cables are actuating the levers on the heat boxes and the scat tubes are in good shape so I don't suspect any leaks.


Any suggestions?
 
Maybe

Is it possible that the intake restrictions were there to slow the airflow through the heat muff and facilitate heat transfer? If the air is moving too fast through the muff, there will be minimal heat transfer from the exhaust pipe...
 
Is it possible that the intake restrictions were there to slow the airflow through the heat muff and facilitate heat transfer? If the air is moving too fast through the muff, there will be minimal heat transfer from the exhaust pipe...

The plane was from FL, this is its first winter. That's a possibility for sure, but the air flow volume when I stick my hand over the rear heat vent isn't excessive. I'd expect the air to be hotter.
 
Something is amiss.......

RV-10s are notorious for having too much heat. Do a search on tunnel heat for more details.

I flying regularly when the temps are in the single digits. I'll crack open the rear heat about a 1/4" and leave the front closed. I will open the front a bit while taxiing, but shut it down immediately after take off. Otherwise, I would start sweating.

The builder apparently had issues too, since they restricted the intakes.

Even with massive leaks, you should be able to feel heat coming out of both the front and rear vents. If you open them wide open, your hand (or feet) shouldn't be comfortable holding them near the vents very long due to the heat.

My recommendation is to get a copy of the plans and find what doesn't match them. There were many custom mods implemented to deal with the hot tunnel issue. One was to bypass one muff and mix cold air with heated. Who knows what the builder did that caused this issue.

After you resolve this issue, I would recommend taking the plans and review the entire build. Validate that the builder followed the plans. Worse case, it will give you more confidence in the build as well as a better understanding of your aircraft.
 
Weak cabin heat

The cabin is at a lower pressure than the outside, so there is a lot of inleakage. The heaters should put out plenty of heat, assuming they are stock and connected properly.

Pull the tunnel cover. The SCAT routing is circuitous and possibly crushed, kinked, or disconnected. Like Bob said, you should feel the flow behind the front seats where it exits the tunnel. Is the carpet in the way?

Make sure the flapper valves really work. Make sure they seal, too, because you do not want heat in the summer.

Check the SCAT to and from the heaters.

Seal the corrugations in the baggage bulkhead with some kind of foam. A lot of cold air comes forward from the tailcone.
 
Like Bob said - something is amis.

Assuming you checked the cabin heat hoses and control box, perhaps the builder did not use the standard exhaust from Van?s (the one with the mufflers). If not, then how he set up whatever he did use might be the root issue.

Carl
 
If the air is lukewarm coming out of the vents check the engine compartment first. Something is wrong with the SCAT routing or it is blocked. I honestly think the RV-10 could heat our house while sitting at idle! The heat muffs in the 10 are fantastic for putting out heat. We usually fly with only the rear heat on, even in temps as low at 5 degrees at altitude. I would think that even if the scat inside the tunnel was crushed you would still feel very hot air leaking through, and it would definitely be hot coming form the front heat outlets.

I have seen the lukewarm air being caused by not hooking up the SCAT tubing in the engine compartment, which is very detrimental to the heat muffs/exhaust. They need airflow over them.

It's also a dangerous source of CO.

Vic
 
Perhaps being built for Florida, the builder is just dumping the heat, keeping it out of the cabin.Check the cabin heat valves on the firewall to see if they have been modified to dump the hot air?
 
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Something is amiss.......
<snip>
My recommendation is to get a copy of the plans and find what doesn't match them. There were many custom mods implemented to deal with the hot tunnel issue. One was to bypass one muff and mix cold air with heated. Who knows what the builder did that caused this issue.

After you resolve this issue, I would recommend taking the plans and review the entire build. Validate that the builder followed the plans. Worse case, it will give you more confidence in the build as well as a better understanding of your aircraft.

I do have the plans, I'll review them today, print a copy and review with the plane when I have the cowl off for an oil change later this week. I'll also pull the tunnel cover to check for kinks.

Last time I had the cowling off I did check that the scat tubes were all hooked up and in good condition. The strangest part is that the air is lukewarm. Theres a reasonable amount of flow, just not HOT.
 
Something is definitely wrong. I run cabin heat off off just one muff cuff split to both front and back and we could still bake brownies in the cabin if we wanted to. We completely removed the cuff from the unused side with Vettermen’s blessing and have just a two inch heat shield attached to the can where it is closest to the cowl. Post pix of the system or have an experienced builder look it over. It’s a pretty simple system and my guess is that the problem will be easily found.
 
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I have limited my flying to above 20F because of the canopy and fiberglass canopy skirt shrink so much in the cold that they do not fit the fuselage well and then leak air. I have plenty of heat coming out of the heat duct but when you have -6F air coming in you will not be warm unless you dress in arctic attire.
 
Like Vic said, the RV10 if built per plans will probably never be accused of not making enough heat. It makes way more heat than most people can tolerate. I was flying in -10F weather on New Years Day and we had plenty of heat. No seeing the breath in front of the face or anything. In fact, unless it's a short flight, we don't wear jackets in the plane because you can count on plenty of heat.

You may want to check for in leakage at your baggage bulkhead, but you should have so much heat coming out of the heat inlets that you don't even want it all the way up. When I run my heat on full, the rear seat heater heats so well that my entire front seat frame heats up in the back, and it gets too hot to touch. There's just a lot of heat available there, front and rear....if it's built per plans.
 
Something is definitely wrong. I run cabin heat off off just one muff cuff split to both front and back and we could still bake brownies in the cabin if we wanted to. We completely removed the cuff from the unused side with Vettermen?s blessing and have just a two inch heat shield attached to the can where it is closest to the cowl. Post pix of the system or have an experienced builder look it over. It?s a pretty simple system and my guess is that the problem will be easily found.

I have the same setup as Myron and have sufficient heat. Right side goes into right side muffler shroud and supplies hot air to front and rear. At -18C a while ago with sun shining into cabin it is more than adequate.. No sun then you need more than short sleeves. ( I'm always amazed at the difference the sun makes!!).
Johan
 
Just checked the plans and it is built per plans. I haven't looked in the tunnel yet to confirm in there, I will do that in the next few days.
 
Check for proper flow

Attach a shop vac to the inlet of the heat muffs and see what kind of flow you get in the cockpit.

Vic
 
Attach a shop vac to the inlet of the heat muffs and see what kind of flow you get in the cockpit.

Vic

The scat tubes have less than 100 hours on them. they're all still in great condition. I was able to visually inspect their connections to the heat muffs on the exhaust as well as to the heater boxes on the firewall.

I did the shop vac trick today for the front heat inlet just under the proper governor.

It worked as I expected. I didn't have full suction at the vents in the cabin, but I had a fair amount of air moving. I didn't feel suction at the heater boxes when the heat was set to ON in the cabin. When setting the heat to OFF the door moved and I was getting good suction at the scat tube at the heat box. Again, slightly restricted but still good suction.

Still baffled. (no pun intended)
 
Do you have the old single muffler system or the newer dual Vetterman system?

It goes without saying that the muffler shroud should wrap tightly around the edges of the inner can forming an open airspace chamber for the heat to transfer. If somebody errantly packed asbestos type material in there like an old glass pak ATV muffler it could cause your problem. You can easily inspect by removing the two band straps and lifting the outer shroud off. I?ve heard of some people welding little fins on the main can to transfer more heat but I?m telling you, those Vetterman muff cuffs put out massive btu?s when properly operated. Make sure when you put the shroud back on that the two sides seal airtight.
 
Do you have the old single muffler system or the newer dual Vetterman system?

It goes without saying that the muffler shroud should wrap tightly around the edges of the inner can forming an open airspace chamber for the heat to transfer. If somebody errantly packed asbestos type material in there like an old glass pak ATV muffler it could cause your problem. You can easily inspect by removing the two band straps and lifting the outer shroud off. I?ve heard of some people welding little fins on the main can to transfer more heat but I?m telling you, those Vetterman muff cuffs put out massive btu?s when properly operated. Make sure when you put the shroud back on that the two sides seal airtight.

It is the dual system.

I'll take it apart tomorrow night and get pictures.
 
Curious what power settings you use when flying. If low power settings or running lean you might not be producing enough heat in the exh pipes. What is your EGT temps during these conditions.
 
Curious what power settings you use when flying. If low power settings or running lean you might not be producing enough heat in the exh pipes. What is your EGT temps during these conditions.


I usually fly 1400 on the hottest cylinder. ROP or LOP. I'm not sure that's the right way, but it flew smooth LOP that way.

Usually around 20-22" and 2300rpm.
 
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Vic,

Re-did the shopvac trick, this time with one that could actually be hooked up on blow.

I think the culprit was that the cabin heat selector boxes weren't sitting flush on the firewall. They were bent away from the FW about 1/8" on the top and bottom so there was a fair amount of air leaking along the FW. I taped them up using aluminum foil tape (checked the SDS to make sure it's safe).

In flight I can only reach the rear heat, but it was HOT and flowing significantly more air. It was 32?F at altitude when test flown, so I won't really know if this is fixed until it's really cold again.

Thanks for the help everyone!
 
Vic,

Re-did the shopvac trick, this time with one that could actually be hooked up on blow.

I think the culprit was that the cabin heat selector boxes weren't sitting flush on the firewall. They were bent away from the FW about 1/8" on the top and bottom so there was a fair amount of air leaking along the FW. I taped them up using aluminum foil tape (checked the SDS to make sure it's safe).

In flight I can only reach the rear heat, but it was HOT and flowing significantly more air. It was 32?F at altitude when test flown, so I won't really know if this is fixed until it's really cold again.

Thanks for the help everyone!

If there was air leaking on the top and bottom of the boxes, I would highly recommend taking them off the firewall and inspecting them. The fact that they are bent on the top and bottom is a red flag. Also, if my memory serves me correctly the box is sealed on the back side. If air is leaking there, then something had to happen to cause that leak.

I tend to be overly anal when it comes to firewall penetrations to ensure that there can be no CO leaks. Better be safe than sorry.
 
If there was air leaking on the top and bottom of the boxes, I would highly recommend taking them off the firewall and inspecting them. The fact that they are bent on the top and bottom is a red flag. Also, if my memory serves me correctly the box is sealed on the back side. If air is leaking there, then something had to happen to cause that leak.

I tend to be overly anal when it comes to firewall penetrations to ensure that there can be no CO leaks. Better be safe than sorry.


Thank you, I think that's excellent advice.

I didn't see any sealant around the openings so I assume it just wasn't done. I I hesitated taking them in order to just diagnose the issue. I also don't much care for the tape being on there, looks like poor workmanship.

I will pull the boxes off soon. I have an oil change to do and I will be installing TCW's Oil cooler control servo and butterfly valve. I'll go after the heater boxes again then.
 
Update to this..

I went to pick up my sister in law about 30 minutes away on Tuesday. Heat was decent on the climb out. Went LOP, but only for about 10 minutes I had to start the descent and well, wasn't making as much power so didn't think much of getting cold again.

On the way back, again good heat on the way up. Went LOP for cruise and a few minutes later turned back to ask my pilot friend who was now in back how the heat was and I could see his breath and he was very cold.

Could LOP ops be a contributing factor? I add fuel to about 1400?F on the hottest cylinder when LOP. But, with no excess fuel going into the exhaust stream I could see that as a reason why I'm not getting sufficient heat. Perhaps when ROP some fuel is getting burned up in the muffler and keeping it hotter. Just a theory.

I need to fly it again to test this hypothesis, but it's crappy weather for a few days.

Thoughts?

Next flight I will also take a thermometer to test the air temp coming from the heater vents.
 
Update to this..

I went to pick up my sister in law about 30 minutes away on Tuesday. Heat was decent on the climb out. Went LOP, but only for about 10 minutes I had to start the descent and well, wasn't making as much power so didn't think much of getting cold again.

On the way back, again good heat on the way up. Went LOP for cruise and a few minutes later turned back to ask my pilot friend who was now in back how the heat was and I could see his breath and he was very cold.

Could LOP ops be a contributing factor? I add fuel to about 1400?F on the hottest cylinder when LOP. But, with no excess fuel going into the exhaust stream I could see that as a reason why I'm not getting sufficient heat. Perhaps when ROP some fuel is getting burned up in the muffler and keeping it hotter. Just a theory.

I need to fly it again to test this hypothesis, but it's crappy weather for a few days.

Thoughts?

Next flight I will also take a thermometer to test the air temp coming from the heater vents.

No, LOP isn't your issue. I fly all the time in the winter. My local temps are similar to yours (unless you're in northern WI :D). I normally fly with the fronts closed and the rear barely cracked. Other than the initially taxi time, I can take my coat off and be comfortably. Most RV-10s have too much heat.

There is no magic in the heat muff. Look at your EGTs to see what the temps are going through the muff.

If you want to go to the source, give Rick at call at 303-423-7002. He builds the heat muffs for Vettermans.

I suspect you have some leaks someplace. You have to find them and appropriately address the issue. The way you described your heat valves mounted to your firewall also appears to be an issue. There should be no 1/8" gaps. Everything should be flush to the firewall.
 
What Bob says is dead on. We rarely have the front heaters open, and we fly with only a light shirt on in the winter, even at OAT's in the single digits at altitude. Something is wrong with your system,a nd it's a pretty straight forward setup. Is it possible to take pictures of your engine side and then the tunnel side and post them?

If you can't post, then send them directly to me and I will take a look for you.

Vic
 
I always took my coat off in the winter up here in northern Michigan when I flew my RV-10. The Vetterman exhaust/heat muff system is like having a couple high btu torpedo heaters inside the plane. I paid a lot of attention sealing up areas that could leak air in the cabin during the build. I even insulated the hallow cavities of my doors with pour foam which stiffened them up a bit also. I insulated the floors somewhat with a single layer of that insulating HD bubble wrap with silver reflective material before I closed them up. I used that stuff Aviation Depot sells for wrapping water heaters. Yeah,,,I know it burns real easy but it was light and cheap. My interior was the basic RV-10 Flightline Interiors with only a few covered poster-board panels, nothing like the fancy padded stuff other vendors have. You have already verified you are getting good unrestricted airflow through the meat muffs into the cabin so I would start looking for leaks inside the cabin. I don't know what the temperature the air should be exiting the tunnel outlet holes in the front, but it was hot enough that it was uncomfortable to hold my hand directly in front of the outlet.
 
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Here's the only picture I have right now. From when I pulled it all apart, the heat muff is obviously slid forward in this pic.

pYPdy5i.jpg


The muff did not have any restrictors in it like I've seen some others have.

cat-med_cabin-heat-muff.jpg



Work today is canceled (snow day at the schools) so I'll head to the airport and get to work on pictures.
 
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Assuming the SCAT is all good (FWF and cabin), the baffle feed vents are good, and the heater boxes are opening properly, then my money is on the muffs. The heat is so strong and effective in a functioning system that I don't see a leak affecting it as described when wide open.
 
Assuming the SCAT is all good (FWF and cabin), the baffle feed vents are good, and the heater boxes are opening properly, then my money is on the muffs. The heat is so strong and effective in a functioning system that I don't see a leak affecting it as described when wide open.

I followed Vic's suggestion to find any leaks in the system. I put the output of a shopvac on the heater intakes. I found some minor leaks and patched them up. It helped a bit. But otherwise the air blowing out the vents inside was what I expected.

Just to say this again, we don't have interior in the plane yet. So I'm sure that's a huge contributing factor.
 
Just to say this again, we don't have interior in the plane yet. So I'm sure that's a huge contributing factor.

I don't think so -- we're not kidding about the quantity of heat the system puts out. You can not fly with the system fully open for more than a few minutes -- I kid you not.
 
I can't tell from the picture but they didn't ceramic coat the exhaust or something did they?

Lynn
 
There is one on each side. This is just the right side.

Interesting. My muffs do not look like that hence my confusion. My SCAT connections are not in line like the ones in your post, they are roughly 90 deg apart: the forward one is the inlet from the baffle vent and the aft one goes to heater box. Also my muffs are shorter and fatter. Here's a pic of my right muff (the left is a mirror image).

FP14122014A0001U.jpg
 
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:cool:
Yes of course. The muff was just rotated so you can't see the exit in the picture.

Ahh, I had to go pull up your post on my phone as my work computer was blocking your top pic so I was only seeing the bottom pic. I see now that we have the same muffs.
 
I still haven't seen a post (though I might have missed it) regarding you spending any effort on evaluating outside air leaking into the cabin.

I think your heat system is probably working as well as any other RV-10, but that wont matter a bit, if it is fighting to overcome a lot of cold air entry.

Initially, the prototype RV-10 had a serious leak problem with the hurry up and get it finished for OSH doors that were installed.
The front seat passengers would be shedding jackets and turning down the heat, while the back seaters were shivering.

Installing the final design doors and making sure everything was sealed properly made the airplane act the way everyone else here is describing.... without doing anything to the heat system.

I suggest you turn your focus to finding air leaks.
Start with finding leaks where flow is going out.

If air is going out..... cold air has to be coming in to replace it.

Think of the physics of a wing. A convexed or outside radius surface (just like the top of a wing) produces a low pressure zone.

The most common location of undesirable flow going out of any RV is in areas of low pressure. These are usually in the vicinity of the canopy because there a lot of outside radius surfaces (low pressure areas).
A common inflow point is at the back of the canopy where the transition to the fuselage is an inside radius because an inside radius produces a zone of high pressure.

On an RV-10 just about the entire perimeter of the doors is an outside radius, so that is a good place to start looking, because at any point that is not full seal, that has lower pressure on one side than the other, there will be flow of air trying to balance the pressure.
As already mentioned, if there is enough flow going out it can be higher than the flow volume coming in via your heating system, so other flow will occur to try and make up the difference.

A handy tool for finding leaks is a long dowel with a spring clip attached to the end. Attach narrow strips of Kleenex to the clip and move it around in the cabin to find indications of airflow (in or out).
Take extra strips with you because if you get it near an outflow point the Kleenex will disappear and you will have to reapply (the reason for the spring clip).

BTW, outflow at the baggage bulkhead is desirable as long as you have fixed all of the other leaks so that the only air that flows in is from either the fresh air vents or the cabin heat system. I.E., if you 100% seal up the cabin, those systems can't work very well because there is no way for cabin air to get out, and allow fresh or heated air to come in. That is where the corrugations in the baggage bulkhead can work for you. It provides a flow path out the back so that fresh air or heated air flows from front to back as it moves through the cabin.

So if everything is working the best it can (because all undesirable leaks are sealed, etc.) the only inflow points for air should be the cabin fresh air vents or the heat system, and the only outflow points should be the baggage bulkhead. If everything is working properly, you should never see any inflow at the baggage bulkhead.

I would bet that if you do the test I am suggesting, that air is pouring in at the baggage bulkhead.
If it is, start looking for the locations that it is rushing out...........
 
Hot?

Scott is obviously correct about the flow around the cabin but I believe you said that the heat coming out of the vents isn?t very hot. That is an obvious sign that something upstream from the vents is amiss. Like many have said so far, you shouldn?t be able to put your bare hand in front of a heat vent for very long without feeling serious heat.

This is like a soap opera! Compelling because the solution should be simple yet, you have to come back week after week to figure out how it ends! :eek:
 
This is like a soap opera! Compelling because the solution should be simple yet, you have to come back week after week to figure out how it ends! :eek:

You would think it should be so simple. Unfortunately I didn't build the plane, we purchased it flying so I'm lacking in some experience that would be very helpful. Which is why I turn to the community. I'm not sure I'm on board with the soap opera comment, and it makes me wonder if I'm in the right place. I only get a few hours a week to either work on, or fly the plane so I have to report back at somewhat longer intervals.
 
Misunderstood

You would think it should be so simple. Unfortunately I didn't build the plane, we purchased it flying so I'm lacking in some experience that would be very helpful. Which is why I turn to the community. I'm not sure I'm on board with the soap opera comment, and it makes me wonder if I'm in the right place. I only get a few hours a week to either work on, or fly the plane so I have to report back at somewhat longer intervals.

Matt,
You may have misunderstood my comment. You?ve had 2,822 views of your post and 5 pages worth of responses. This is obviously of interest to fellow RV-10 builders and owners. Why? It?s because every other RV-10 owner with functional heat knows that the airplane puts out more heat then your home oven so everyone is waiting with baited breath to figure out why yours isn?t putting out the heat. It?s that suspense, not your lack of knowledge, that led me to make the comment about the soap opera. No harm intended.

You?re definitely in the right place as you just received feedback from some of the most experienced RV-10 flyers around including from within Vans Aircraft. You won?t find a better knowledge base or community anywhere. Keep letting us know what you find and everyone on here will do what they can to help.
 
Update to this saga.

Temps aren't so ridiculously cold lately so it's tolerable flying the plane with just the minor updates I made, sealing up the edges of the heater flapper boxes on the FW.

I took the advice of this thread and took small strips of paper towel with in the airplane. It was obvious where the air was getting sucked out. The door hinges were the strongest, and the door handles had a little air going out as well.

I was told by someone wise a while back that the door hinges will suck air out like crazy. I can't believe I forgot about that.

We threw some rags in the door hinges and the handles, found a few other much smaller leaks and got back to flying. The heat was better, but still not great, especially in the back.

Right now we're working on interior installation and finally got around to pulling the tunnel cover and I found several small holes in the SCAT tube for the rear heat. I'm going to patch those up or replace the whole thing. The holes are all near points where I can plainly see what the thing was rubbing on so it won't be terribly hard to prevent it from happening again.

Thank you to everyone who's read and replied. As many have said, it was a bunch of little things that added up to a severe lack of heat.

To summarize,

  • Sealed up the edged of the heater boxes on the FW using aluminum tape.
  • Checked at SCAT tubes, found the rear tube in the tunnel is leaking
  • Found several large air leaks in the canopy at the door hinges, door handles, etc using thin strips of paper towel.
  • Stuffed rags in the hinges and the front gets nice and toasty.
 
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