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Insulating rear bulkhead

Drippy

Well Known Member
Guys,
I am sure this has been discussed and I am not searching under the proper heading.

I need to insulate the corrugated panel aft of the baggage compartment. Does anyone have a nice solution to filling the "Vs" without cutting individual slices of foam?

Thanks

Drippy
40644
 
I couldn't find any online photos of my RV-10, but it's very similar to what Geoff Combs did in his.

It's basically two pieces of fiberboard. The bottom one is covered with carpet. I also have Geoff's interior panels and carpet installed too. The carpet then is a uniform look with the carpet on the lower side of the baggage area. The top piece is covered in leather with experimental embroidered. The sides are tight with the side panels. This stops any drafts coming through the bulkhead.

It's not really insulation, but I don't think it's needed. This cosmetic upgrade is more than adequate. I fly quite often when it's below freezing. Being cold has never been an issue.

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I bought some aluminum backed felt from Spruce, then cut small strips. They compress enough that they can be forced into the V's against the bulkhead. Stopped the draft.
 
However you end up sealing the bulkhead built in leaks, remember the actual bulkhead and former/frame assembly it is bolted to is a structural setup, and needs to remain strong.

I suggest you DO NOT sandwich anything between the bulkhead and the former it bolts to. Just work on the actual "V" notches.
 
Filling the V

Guys thank you

Thank you for the advice. I have been wondering if I could clamp it to a piece of plywood covered in wax paper and then filling the V's with spray in foam, then putting on a thin layer to protect it.

Anyone try something like that?

Drippy 40644
 
one way

I just recently took some fat, like 3/4" weatherstripping foam, cut individual pieces ( not that hard, took 13 seconds!) and stuck them in each 'vee'.
sliced almost flat with the back surface, so there would be a tiny bit of 'crush' on the foam when mounted, and.........you're done.
invisible, $5, took 10 minutes.

..gained about 3 kts at least! :D
 
I just did my RV-14 bulkhead this week. I used some 1/2 or 3/4" round weatherstrip, just glued in place in the "V" with some clear RTV. There will still be a very little bit of gap, but you can either leave it or seal it with the same RTV. I let it set up a short time before installing the bulkhead wall. Took it back out tonight and looked at it. Should cut down on some of the cold air coming in.

Now, that said, I did NOT seal off every single one of the corrugations. The reason is, with the high flow available with the air vents, you're going to need somewhere for the air to go. If you seal the bulkhead completely you're just going to make the air vents less effective because there will be nowhere for the air to go, and the same with the heater vents. If you are going to flow high volumes of hot or cold air in, you're going to need it to exit too. Also, on the RV-10 when in flight, the doors are being sucked out with quite a bit of suction from the airflow over the airframe. If you add some additional air pressure inside, you're going to potentially make that worse also.

So, in short, I would definitely NOT recommend sealing the entire baggage wall, but just seal it enough that you minimize the amount of cold air that will come in from the tail. Keep a pathway for the hot/cold air from the front to exit. There are lots of other little places where the air will leak out, into the wing roots by the aileron pushrods, and places like that, but some people also have bellows on those too.

Just things to think about.
 
Well, I'd say 'it depends'. I tried to seal up all the corrigations in the aft bulkhead, but not into the wing nor tunnel. Air and heat come into the cabin fine, and alternate static open shows the cabin below outside pressure. So the air gets out somewhere.
 
All of you guys that seal up the aft bulkhead, what do you incorporate to let air (vent and heat) out???

If purposely choose to bring air in, you have to have a path to let air out (or it will try and make its own...like door seals, etc.)

If cabin pressure is below static pressure, it is a good indicator of leaking door seals.
Like Tim said, the fuselage sides are curved and have low pressure on the out side.
That is largely the reason for the stock seals (which people love to hate for some reason)... they seal well through a wide range of gap dimension and any slight movement/flex outward of the door in flight.

When people ask me how to fix cold inflow air leaks..... I always tell them to find and seal the outflow leaks.
 
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If cabin pressure is below static pressure, it is a good indicator of leaking door seals.
s.

Scott, I disagree. If there were absolutely no leaks, the cabin would explode when we climb to altitude. Those leaks go to the low pressure just outside (which we agree on) so even with very good door seals the cabin will be below static pressure.
 
When people ask me how to fix cold inflow air leaks..... I always tell them to find and seal the outflow leaks.

Excellent advice.

If anyone thinks sealing the baggage bulkhead will prevent air from entering the cabin from the tail they should consider that air can just bypass the baggage bulkhead and flow between the floor stiffeners and find its way into the cabin by other routes.

Seal everything from the firewall to the baggage area. (Don't worry about the baggage bulkhead) This will prevent air from coming in the tail cone.

Pay close attention to the large gap between the spar caps of the wing. The wing root to cabin area is probably one of the areas that has the biggest pressure differential to the cabin. Build some boots to seal the aileron pushrod pass-through holes. Make sure the doors seal.

By doing this it is possible to have -10 that when the air vents are closed, there are no air drafts inside. Also makes it much quieter.
 
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I left the corrugations alone. I painted the rear bulkhead with the same color as the rest of the interior. I used a 1/4" piece of self adhesive black foam on the backside for insulation. Now that I am flying, in hindsight, see that there was no reason to insulate the rear bulkhead. The heat will drive you out and is more than adequate, and the plane is so noisy from everywhere else that insulating the rear bulkhead to help with the noise situation is not needed. Save the weight and use it as a margin elsewhere is my advice.
 
My reason for plugging the V's was that back seat passengers complained about the temperature gradient - their ears were cold while their feet were hot. Cold air mixing in thru the floor is not so bad, as it quickly mixes with the heated air which is also at floor level.
 
Scott, I disagree. If there were absolutely no leaks, the cabin would explode when we climb to altitude. Those leaks go to the low pressure just outside (which we agree on) so even with very good door seals the cabin will be below static pressure.

I never said sealing up door leaks would make a leak free RV-10 cockpit... it wont.
There are still a lot of other little places to leak.

I do know from personal experience that the low pressure areas on the outside of the doors will draw air out of the cockpit. If a lot of the bigger leaks are sealed (baggage bulkhead, etc) it could be enough to pull the cockpit pressure below static.
 
My reason for plugging the V's was that back seat passengers complained about the temperature gradient - their ears were cold while their feet were hot. Cold air mixing in thru the floor is not so bad, as it quickly mixes with the heated air which is also at floor level.

I have experienced it first hand freezing in the back of an RV-10 with the aft heat on full blast and the front heat turned down to just about off because they were getting roasted.

Stuffed a towel around the perimeter of the bottom of each door and within 10 minutes I was in a short sleeved shirt with the heat turned down to about 1/3 on.

Like I said, correct the cause of significant sources of outflow, and you will fix the problem of cold inflow.

Later sealing of the doors properly made even the back of the cabin toasty warm while the baggage bulkhead corrugations were still open to provide a path for heater or vent air to get out.
 
The cabin pressure is always lower than the tailcone. That is why air flows forward through the corrugations in the aft bulkhead. There MUST be a differential pressure for the air to move. So air pressure runs from high (tailcone) to medium (cabin) to low (outside cabin), therefore that drives the flowpath.

The cabin leaks like a sieve. Openings include the control column path into the wings, openings into the tunnel from a couple points, leaking door seals and air vents. A lot comes from the aft bulkhead and causes cold draft complaints from passengers. There is low pressure outside the cabin due to aerodynamic forces and that pulls air out. That is also why the doors will explosively open if they are unlatched.

I stopped air from blowing by the bulkhead corrugations by cutting 1/2 inch thick foam into 2 inch long triangles and used duct tape to hold them in place. As noted before, the baggage compartment bulkhead is a structural member so don't do any mod to weaken it. I would not worry at all about positive pressure in the cabin because this mod should not impact it significantly. An easy test would be to unblock one bulkhead corrugation and see which way the wind blows. Maybe Tim can test it since he left a couple open.
 
So the next question is: Where would be the best place to put a exit air duct on the aircraft? Rather than have all this cabin air squirting out various locations, causing drag, why not an aft facing small duct that draws the air out pointed in the right direction. We spend so much time talking about cooling drag but give no consideration to where the air goes from two 2" full flow vents!
 
The cabin leaks like a sieve.

Only if you let it......

Boot seals on the control sticks, aileron push/pull rod seal boots, blocks of foam stuffed in the rectangular openings of the center section bars , caulking around the gear leg penetrations, and doors seals that actually seal (even in high speed flight) seals up the majority of the leakage path.

Once you do that, the baggage bulkhead corrugations will be the primary path for out flowing air.
 
I have noticed aft facing bluff body ducts on the aft lower fuse of the bonanza. I suspect that there is a duct from that baggage wall vent to that aft facing belly scoop. As the RV10 is not designed for aerobatics this could be an excellent design to copy. I have hesitated copying this on my Rocket as I am concerned about exhaust fumes, in some conditions, for example aerobatics. The limited time that I actually spend in those conditions probably negates the issue. This summer I will do some testing with a cabin pressure indicator and a CO detector. This has been on my long term list of to does for too many years!
 
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