Cowl Pucker

[brad walton]

The gap in the hinge is per plans. But from this second picture, it looks like installation of the air/ oil seperator interferes with the normal access to insert the pins from inside the cowl and the solution was to insert the pins from outside the cowl. No real harm except the gap from cowl to top skin was widened to permit pin insertion from outside and thus the 3/4 inch gap. Appearance issue and not a danger that I see. Maybe others may have another view on this. You do need some way of keeping the pins from backing out. Maybe someone here can post a picture of the way to make a pin retainer.

[Henryrifle]

Thanks for looking. I don't think there is much likelihood of the pins coming out. They haven't moved in the 26 hours I have put on the plane. Removing and installing them requires a pair of pliers.

Thanks again for all the suggestions,
Hank

[704CH]

Here is the best picture I could come up with explaining the issue. The hinge on the cowl should be one piece with the eyelets cut out. This adds strength to that 3.5 inch gap and it will not pucker during flight. Some builders use two hinge pieces but this is not correct and the gap is not reinforced. You can probably reinforce this after the fact by adding some sort of stiffener in the gap and either fiber glassing it in or rivet it. It looks like your cowl is painted, so riveting might not be a preferred option.

[MikeyDale]

If mine puckers 3/4", the cowl wont be the only thing "puckering!"

[Henryrifle]

Thanks for the education and your ideas. I really appreciate the time and effort it takes to create and convey a descriptive and prescriptive post. I'll take a look at the cowl and see what options exist.

Thank you again,
Hank

[texdog]

My pins are inserted from the oil door. The top cowl has the three inch gap, but it has a 4 inch layer of fiber glass stiffener that keeps it from puckering. I would just add a 1/4 inch of glass and it will reduce the pucker. My pins did work out but I fixed that. The short pin came out once and you couldn't tell it in flight.

[JAT]

Hank,

I think the problem may be helped by adding enough hinge, so the gap is shortened. My hinge gap between the two sides is only three hinge loops and I don't have any problem with getting both wires in. When flying, the rise in the cowling is barely noticeable.

Jim

[Berchmans]

I have the continuous hinge as noted in post 13 on my RV8 and have no pucker issues.

[Steve Melton]

Originally Posted by texdog

My pins are inserted from the oil door. The top cowl has the three inch gap, but it has a 4 inch layer of fiber glass stiffener that keeps it from puckering. I would just add a 1/4 inch of glass and it will reduce the pucker. My pins did work out but I fixed that. The short pin came out once and you couldn't tell it in flight.

you have probably already done this. I bent the pin handles so they interlock if they tend so slide out. I have no additional pin locking method, works great.

[Bud K]

Timely topic. I too noticed that my cowl 'puckers' in the same location. Two piece piano hinges and standard baffles. I usually don't see it since my Stratus blocks my view in that area. Mine is more like a 1/4". My cowl does not have the piano hinge in that section so that appears cause some flex in that area, causing the issue.