I'm cutting my cowl...

[JimS]

My "6" that I've owned for just over a year has the dreaded "lower rear cowl hinge" problem. i.e. broken eyes and pulled through rivets. I'm going to change to screws as many have. While pushing the lower cowl into position I noticed the the cowl was flexing way up near the front of the snorkel. (and I could barely get those cowl edges up into position) No wonder the hinges can't handle the stress. I've cut the snorkel from the rear up to within about
5" of the intake on each side. Now when I push up the back edges where the hinges were it only takes about 1/3 the effort to get things into place. The exit scoop hangs and there is a gap of about 1" at the cut line at the back.
I will glass,sand,repeat...you know, build a cowl that fits
I am sure others have gone before me doing this same procedure but was wondering if anyone made any additional stress relieving cuts to the cowl.

JimS

 

[rvbuilder2002]

My "6" that I've owned for just over a year has the dreaded "lower rear cowl hinge" problem. i.e. broken eyes and pulled through rivets. I'm going to change to screws as many have. While pushing the lower cowl into position I noticed the the cowl was flexing way up near the front of the snorkel. (and I could barely get those cowl edges up into position) No wonder the hinges can't handle the stress. I've cut the snorkel from the rear up to within about
5" of the intake on each side. Now when I push up the back edges where the hinges were it only takes about 1/3 the effort to get things into place. The exit scoop hangs and there is a gap of about 1" at the cut line at the back.
I will glass,sand,repeat...you know, build a cowl that fits
I am sure others have gone before me doing this same procedure but was wondering if anyone made any additional stress relieving cuts to the cowl.

JimS

Jim,
The original cowl shape for the 6 would fit the airplane without inducing any load. The builder of the airplane must have ended up with a trim profile that caused it to fit as it does (most likely the aft sides not trimmed correctly).
The fix you propose should work fine, but I suggest you have the entire cowl installed on the airplane and fully pinned together while your F.G. layups are curing.
Also keep in mind that changing the exit area that much will definitely effect cooling air flow volume (more). For your airplane that might be a good thing, but for most it would mean slightly lower cruise/top speed with possibly less than optimal CHT's (particularly during winter).