Buldge in upper cowl at hinge pin

[Mike Redd]

The cowl buldges out in flight where the hinge pins are inserted in the cowl to fusalage. This is at the spot you cut out the eyes of the hinge to allow insterting of the pin. Behind the oil door. It's a RV7 IO360. I'm getting a few specks of oil on the windscreen on the passenger side. Looks to me like the oil is coming out the buldge in the cowl. When not flying the cowl lays flat. I've trimmed the bottom cowl outlet even with the firewall. Is anyone trimming more? Ideas?

Mike Redd
Oregon

 

[dan]

The bulge is due to the cowl being "pressurized" and there being no hinge along that stretch of top cowl to keep it from bulging. Mine does the same thing.

In retrospect I would have split the hinge at the center, had less gap between hinge sections, and used an externally removable cover panel so the pins can be removed & replaced outside the cowl (no reaching in). It's not a big deal to reach in, but it can be easier, so why not?

With just a 1" or so gap, instead of 3" or whatever it is now per plans, there would be no pressure bulge (or at least a lot less bulge).

As for your leak...good luck tracking that down.

 

[rv72004]

How about laying up 6 to 8 layers cloth on the bulge area? This should stiffen it up, like a bridge and greatly reduce the bulging.

Also as the extra layups are inside, it wouldnt affect a painted cowling.