Cowling Crack Repair?

[inman]

I am finishing up some pretty seroius repairs after a recent ground loop and want to fix some cracks in my cowling. They are making a run for it in the corner of my airfilter cut-out and at a couple of other nose bowl mounting points. I am being told that welding or brazing is not possible and I am wondering if anyone has heard of any sort of material that could possibly be used to backup these areas to hold them together and provide some support. My cowling is actually off of a 1968 C-172 as part of an Avcon Conversion and the air filter opening had to be cut-out larger which left no real structural support. Any and all ideas are appreciated.

[zero.one.victor]

About all I could suggest is to stop-drill the cracks & add doublers.

Eric

[Kyle Wolfe]

I'll add to the fray.... I too have the typical cracks coming in the cowling located in the rear of the cowling and low on each side. Appears that the cowling has been patched with a piece riveted in. But it too has cracked. Almost all 170s that I look at also have cracks in this spot.

Any solution other than "that's just the way they are?"

[GAHorn]

Stop drill, remove the existing paint, add doublers as necessary, and fill with JB Weld. Sand and repaint. It'll look fantastic and last a long time.
On smaller cracks, and even on chafe-throughs, tape can be firmly applied to the outside of the cowl, JB Weld added to the inside and worked into the cracks and chafe-throughs, then after it's cured, remove the tape, and paint. This repair is durable and cannot be detected externally.
I use the 4-minute JB Weld on such items and it's been great.
The lip around the nose-bowl is famous for developing cracks. Using coat-hangar wire to reinforce the lip's circumference on the inside of the nose-bowl, with the wire held in place with JB Weld, such repairs can be darn near undetectable without removing the cowl and add strength and body to the nose bowl eliminating/drastically reducing future cracks. Be sure the inner surface is clean and dry, and slightly roughed up with scotch-brite for good adhesion.

[zero.one.victor]

I've heard of doing something similar on the fiberglas nosebowls that a lot of the Lycoming conversions have. They seem to crack due to the increased vibration (especially at start-up).
Form a steel or aluminum rod around the inside of the cowl opening, as per george's post. The glas it in using fiberglas instead of JB Weld as george describes. Not picking on you George, just detailing the fix as others have described it.
Either JB Weld or fiberglas seems like it'd be pretty heavy in the quantity required for this job.

Eric

[zero.one.victor]

Just looked thru The 170 Book. Page 110 (4th edition) has an article by Illinois member Lou Gauger, where he describes glassing in an aluminum pipe around the lower half of the nosebowl opening, and glassing in a polyfiber rope around the top half of the opening. His installation apparently has a split nosebowl.

Eric

[GAHorn]

I've heard of doing something similar on the fiberglas nosebowls that a lot of the Lycoming conversions have. They seem to crack due to the increased vibration (especially at start-up).
Form a steel or aluminum rod around the inside of the cowl opening, as per george's post. The glas it in using fiberglas instead of JB Weld as george describes. Not picking on you George, just detailing the fix as others have described it.
Either JB Weld or fiberglas seems like it'd be pretty heavy in the quantity required for this job.

Eric

No problem, Eric,...good advice is always welcome! Fibreglas repair kits are available at WalMart and Marine dealers and are good stuff. JB Weld is best only for small cracks/repairs due to expense and working time.

[dave99nt]

Steve, I worked on 19D when the 172 front end was put on. Just wanted to find out how it was going.