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Sealing Flap Push Rod Openings — Good Ideas

Darin Watson

Well Known Member
Friend
I have owned my RV 7 for several years now and have developed excellent canopy seals (slider), implemented a great idea for heat muff surface area increase and sealed the usual wing root and aileron push rod boots spots, all which make winter flying comfortable up here in Calgary, AB.

All that said, the one thing that I don’t have is a good solution for is sealing the pushrod openings for the flap pushrods, and I have tried 3 different designs.

For those with a good solution, please post, preferably with photos. Thanks in advance for sharing the knowledge!
 
Darin I have the same problem and have been wanting to come up with a solution and haven’t had any success. I look forward to what others have done.
 
I have owned my RV 7 for several years now and have developed excellent canopy seals (slider), implemented a great idea for heat muff surface area increase and sealed the usual wing root and aileron push rod boots spots, all which make winter flying comfortable up here in Calgary, AB.

All that said, the one thing that I don’t have is a good solution for is sealing the pushrod openings for the flap pushrods, and I have tried 3 different designs.

For those with a good solution, please post, preferably with photos. Thanks in advance for sharing the knowledge!

Can you elaborate on this great idea? I'd like a little more heat if it's possible from my muff.
 
I have no pictures to show but have thought about sealing the flap push rods similar to how the aileron push rods are sealed entering the fuselage.
A sewed fabric hood attached with Goop to the fuselage and zip tied to the upper rod end would prevent air flow and seal well. The hole in the upper fabric end would be large enough to allow the push rod to be removed for inspection purposes by sniping the zip tie.
I ruled out rubber bellows similar to what’s used on rack and pinion sterling systems because of the cost and a more complicated mounting method.
 
I have not done it yet but plan on chemically/mechanically bonding 1-3mm neoprene around the pushrods. I have not experimented yet but it is quite pliable and offers little resistance in other applications I have used it in.

Just a thought
 
Question

So are you looking to seal them only when the flaps are up, or all the time? Seems to me the seal really only needs to be when the flaps are up?
 
What I have done so far

I will try to answer most of the preceding questions:

@Stewbronco - I misstated wing root faring; what i meant was the wing spar penetration through the side where there is approximately 1/4-3/8" gap on one side and 1/8" on the other. I used pink styrofoam insulation cut to fit reasonably close and then liberal HT - RTV to seal and hold in place.

@birddog486 - see the below photos. A few dollars to have laser cut 1mm stainless steel (photo 1) and then bend ~90 degrees, wrap your exhaust pipe, and twist the "fins" to 90 deg so the the flow is not too restricted (photo 2)...works really good.
Photo 1
Photo%202013-03-01%2C%2014%2033%2013.jpg

Photo 2
Photo%202013-03-01%2C%2009%2030%2007.jpg


I ended up adding a second muff and putting 6 rows spread out on each muff because temperature is fine....but needed more volume. Now there is virtually no temperature issue, per se, except that the flap rod hole still puts a cold knife in you when the OAT is -53C (yes did that once over WY on the way to Mexico!)

@dpansier - what you describe is what has worked best so far. I took fairly thick marine vinyl and made a "pocket" for the arm off the torque tube to tavel inside of while bonding to the floor and side wall of the fuselage...which has been OK, though there is quite a lot of pressure to contain and with the relatively large area the glue will not hold for more that 2 seasons. The pressure created when flying is far greater that the "blow" my shop vac can produce when I duct taped the outlet to the hole in the fuselage ground testing for leaks and any constraint on the flap actuation mechanism. A pure bellows is not feasible as you have to connect to the bottom and the side of the fuselage, though it would be nice if it was just a round hole then one could do like the aileron push rod boots.

@pilotjohns - ideally sealed up or down, but as you say 99% of the time is up, and certainly that is the worst when at altitude and speed as opposed to the <80kts when the flaps are out. Are you thinking something 3D printed that covers the hole and is attached to the pushrod in a fixed location that seals when up?

Please keep the ideas flowing!
 
Direct imbed photos of heat solution

Here are photos of the heating solution, if the link is not working....forgot about the switch over.

25AB3DA6-7021-4FF3-8A70-78A9AF3F79ED.jpeg

FA223DC7-1836-4B56-B980-8A1F50632C41.jpeg
 
I’ve not tried this but I recall someone recommending a throw away sponge paintbrush and cutting off the handle then glued the sponge to the floor with a X-cut in the sponge for the pushrod.
 
I’ve not tried this but I recall someone recommending a throw away sponge paintbrush and cutting off the handle then glued the sponge to the floor with a X-cut in the sponge for the pushrod.

I would not use anything that will hold moisture. That is asking for trouble.
 
I’ve not tried this but I recall someone recommending a throw away sponge paintbrush and cutting off the handle then glued the sponge to the floor with a X-cut in the sponge for the pushrod.

That was possibly me, but I just cut a slit in the foam. Here's the photos from almost 16 years ago. The paint brush foam is reasonably wear resistant and held up well.

Flap pushrod seal 1


flap pushrod seal 2



flap pushrod seal 3

Here is a nifty flap pushrod gap seal that is easily made from the foam of a foam paintbrush. It really does a nice job. The paintbrush foam is soft, yet tough, and conforms nicely around the flap pushrod. The U-shaped piece of aluminum on the bottom was intentionally left rough, not deburred, and drilled full of rough holes so it would grip the foam tightly. That foam is just the ticket.
In the lower right corner you can see a hole which I melted through the foam with a soldering iron. When you install the floorboard, a screw goes through that hole. The foam scrunches down nearly flat, as you can see, and does not cause any fitting problems even though it is between the floorboard and angle on the fuselage.
 
I would not use anything that will hold moisture. That is asking for trouble.

The foam brush material is open cell and dries quickly, if it does get wet, which it rarely does unless someone barfs on it. Speaking of the only time that the foam ever got wet in my plane, well, I think you can infer what happened.

YMMV
 
Foam seal

That was possibly me, but I just cut a slit in the foam. Here's the photos from almost 16 years ago. The paint brush foam is reasonably wear resistant and held up well.

Thanks for sharing Vince...16 years is certainly adequate test period for long term effects.

What model RV is this...the -4 in your signature? Your pushrod penetration looks different than my -7; it has a “notch” up the side wall of the fuselage for the lower rod end and connection to the flap.

The dryer county helps with any corrosion concern, as would a little gun oil in the sponge from time to time. Also the push rod is an easy component to replace if any pitting were ever to show up.

I think we have a winner!
 
i sealed my slider rear and side skirts and the bulkhead triangles but it is still a lot of cold air coming into the cabin.

i'm under the impression that most of the cold air now comes from the flap rod holes, which kinda makes sense as the lower area of the wings/fuse (where the flap rods openings are located) should be a high pressure area and the cabin seems to be low pressure.

i really like the idea to close the flap rod opening via the method shown by Vince. Is there anybody who can say that this mod resulted in an noticable improvement? i am thinking just to glue the foam with epoxy to the inside of the fuse skins.

Thanks
Kay
 
The weather/window sealing from Lowes and HD might be a good choice. Closed cell and has good memory so with some clever adaption, it should make for a very good seal. Used it on a Mooney to seal the notoriously leaky eyebrow access panels that cover those expensive radios. It worked way better than the factory suppled stuff. Keep us informed.
 
I use a stainless steel scouring pad, rip it apart and stuff it into the heat muff, works great!

DAR Gary
 
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