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Topic-icon Minor Cowl Repairs

11 months 2 weeks ago #1842

Cowls are considered as secondary structure (not as primary structure) and can easily be repaired and documented in the log books as "minor repair to cowl leading edge". The only time you need an approved material combination is when a repair is made to primary structure, and is documented in a Structural Repair Manual, Section 51. There is no Structural Repair Manual for your airplane, so AC 43.13 is the guidance and authority to be used. To see what Section 51 contains, find someone with a Cirrus. Its on a CD that all owners receive.

As far as doing your repair, there is a bit of a learning curve dealing with composites, so if there is someone you know who has built a composite airplane, they would be a good resource. I like the MGS resin system that Spruce sells, and it is also listed as approved by Cirrus. To make the leading edge more durable, consider using about 3 layers of carbon cloth, where the buildup starts out smallest in width and additional layers are wider in width, overlapping the previous layer's edge. When the resin is cured, sanding will be required to smooth all surfaces. Try to find a rattle can of paint to match as close as possible.

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  • William Rose
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11 months 2 weeks ago #1838

I'm slowly trying to chip away at the worst of the blemishes on my aircraft to stall having to resort to repainting it. Both halves of the cowl are showing their age . . . the bottom half has hundreds of little chips about the size of a pin head; the top edge of the top half is really chewed up. I know there are many figerglass repair products available but is there one that works particularly well on airplanes and/or a product that someone has had personal experience with.

With apologies, I also wanted to ask for a recommendation for the seal that surrounds the firewall that the two halves of the cowl rest on as well as the seal on the lower cowl that reduces vibration, keeps the weather out, and prevents the chafing that can cause the fiberglass to deteriorate. I've looked at several products but none were approved for certified aircraft. This looks like an owner maintenance item but identifying the appropriate product seems to be the elusive part. Thanks

Last edit: 11 months 2 weeks ago by William Rose.

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