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Broken Cowling Piano Hinge...

Piper J3

Well Known Member
A friend has a Synergy built RV-12 with cowling piano hinge problems. Last year two “lugs” wore thin and broke off the tight side top piano hinge (cowling side) near the oil door. Now there is broken lug (firewall side) on lower piano hinge again on right side of airplane. Synergy did some shotty work on this airplane and perhaps that is problem we are experiencing.

Anyone else have broken piano hinge on RV-12 cowling?
 
I had the same problem, I have a repair method that works great without touching the paint. I’ll find you the post.
 
Not yet, I used the regular JB, it is stronger than the 5 minute version. I have bonded many things in the past that had a lot less surface area that have not failed.
Scuff it up, clean with acetone, have a good fit with minimal glue line thickness, use some clamp pressure, not excessive. Let it completely cure, some heat will accelerate it. Use the remaining mix to test when the mixture is cured.
 
Looks like I have the same problem now.

Makes me want to find all those posts concerning the "dust"/"smoke" on the paint near that hinge, and the responses that say it's no big deal. At just 250 hours, it feels like a big deal.
 
Hinge smoke

The first picture is typical of hinge smoke after a couple hours of flying with the Sensenich prop and dynamically balanced. The second picture is after many hours of flying with the fixed pitch 3-blade Catto. I have over 30 hours now with the Catto and have yet to see any hinge smoke. The Catto is amazingly smooth running. I know not everyone will want to go out and spend a bunch of money on an expensive prop but vibration kills everything eventually. Could be worth the money in the long run.
 

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Tony, do you have a link to that specific product? The Catto web site is not helpful.

They do not have the RV12 propeller package currently on their website. I recommend emailing them or call their phone number and talk to Nicole (Catto) Klith. She is director of sales and handles the RV12 propellers. She will know what you are calling about and can answer questions, 209-754-3553 - [email protected]
 
Can anyone show a picture of the broken hinge?


Is it the same hinge eyelets that are wearing and breaking?


Is there a fix during the build which would prevent this?
 
Can anyone show a picture of the broken hinge?


Is it the same hinge eyelets that are wearing and breaking?


Is there a fix during the build which would prevent this?

Typically the co-pilot side is where the most vibration/ wear occurs. See post #3 of this thread for the repair.
There are 2 types of hinge material. One has rolled eyes the other has machined eyes. The machined ones are far superior and can be bought from Spruce. If I was building that is all I would use.
 
Typically the co-pilot side is where the most vibration/ wear occurs.

I wonder why co-pilot side? P-factor from prop? Turbulence from protruding round exhaust stack? Air turbulence around/thru cowl opening for exhaust stack?
 
I think it's because the pilot's side is stiffened by the fiberglass air ducting. No such support on the right side.
 
Typically the co-pilot side is where the most vibration/ wear occurs. See post #3 of this thread for the repair.
There are 2 types of hinge material. One has rolled eyes the other has machined eyes. The machined ones are far superior and can be bought from Spruce. If I was building that is all I would use.

Thank you.......I will look into the extruded hinge.
 
A follow-up to post #1…. Hinge was replaced and “smoke” pattern from loose hinge loops was noticed on right side of lower cowling. My friend cleaned both halves of the piano hinge with brake cleaner and then used a toothpick to smear some clear GE silicone inside the hinge loops. He let the silicone dry and they reassembled. Hinge pin was a little hard to insert on initial reassemble but result is a clean cowling with no “smoke” trail. Only about 5 hours flying time but results look promising…
 
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