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cowl Repair

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Old 10-04-2007, 06:50 PM
  #1
PeteS
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Default cowl Repair

I have an old pattern plane, an LA1, that I have been flying for many years. Overall wear and tear has cracked the removeable cowl around the openings for glow plug access and vens.

I bought this plane already assembled and have no experience working with fiberglass. How do you go about fixing this?

Thanks!
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Old 10-04-2007, 09:06 PM
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Default RE: cowl Repair

I suggest the following:

Clean the INSIDE of the cowl thoroughly with alcohol (acetone WILL attack and damage a fiberglass cowl and will also damage an ABS cowl )

Using some 2 oz fiberglass cut patches to cover the areas to be repaired and to extend about 1" beyond any damaged area.

Do this step ONE PATCH AT A TIME and read completely before beginning. Place a patch in place and smooth dowm with your finger. Next put THIN CA on the patch. If the patch needs to be pushed down more use a metal rod with the end rounded to push down the fiberglass patch. If you need to push the patchdown you will need to work quickly since the thin ca will harden the fiberglass within seconds.

My experence has been that fiberglass resin has a couple of problems. If the cowl is fiberglass and you use the wrong type of resin you may be lucky and just have a mess, OR you can damage the cowl. Also, resin does not adhere as well to ABS as thin CA (at least for me it doesn't )

When the ca has dried (typically about 20 minutes ) proceed to the next patch.

When all the patches are in place and dried, clean, then sand the outside of the cowl, then clean again.

Now you can add filler as needed to fill any cracks, etc.
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Old 10-04-2007, 09:13 PM
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Default RE: cowl Repair

I agree with campy. I have actually repaired very badly damaged fiberglass cowls and wing pants. The CA with cure very quickly so plan ahead and measure more then once before you glue. Try not to use accelerator either, I have bad experiances with this because it actually makes it brittle and can even damage the cowl.
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Old 10-05-2007, 12:21 PM
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Default RE: cowl Repair

I don't know what kind of resins you have experience with but neither polyester or epoxy resins are affected by acetone. As a person who does fiberglass boat repairs often (people sized boats), use epoxy resin when making fiberglass repairs. Epoxy is more flexible than polyester and adheres better to cured polyester than polyester adheres to cured polyester...
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Old 11-01-2007, 01:17 PM
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Steve Steinbring
 
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Default RE: cowl Repair

I'd like to add to whats been suggested above. If you have a crack its a good idea to stop drill the crack to keep it from spreading further. Epoxy bonds well with either ABS or fiberglass. I just finished repairing a cowl for a old King Cobra that I'm pulling out of mothballs to fly again.

For my repair I cleaned and sanded the cowl inside and out, stopped drilled the crack. Once that had been done I applied a coating of epoxy to the inside of the repair being sure to glue the crack surfaces and stop drill area well. Applying a piece of masking tape to the outside of the crack line before gluing will help keep the epoxy from weeping out of the crack and keep the adhesive contained to fill the stop drill or any voids. Add a piece of fiberglass cloth overlapping the crack area about 3/4" on all sides, top coat once the fiberglass cloth is in place. Once cured I filled any inperfections on the outside, primed and finished the cowl. Good as new, but stronger.
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Old 11-05-2007, 07:01 PM
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Default RE: cowl Repair

Thanks to all for the suggestions!!
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