Fiberglass help... Underside Layup

[planecrazzzy]

What I'm going to suggest has nothing to do with fiberglass...

Seems the trouble lies with the aluminum...

When shaping aluminum...it gets hard and a little brittle...
To keep shaping it without damaging it... Heat is applied to neutralize the tension that built up.
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To know how much heat to apply , mark a "Sharpie" line on it...
When the line DISAPPEARS... you have neutralized the tension and can continue shaping it.
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In your case.... If you can use a propane torch "IN-PLACE" , it might help you fasten the piece you already have in place.
Bend a piece of scrap aluminum and test it out... Sharpie and heat
I like the push button propane burners...the larger ones ( $50 ) not the little flame 15 dollar ones...

Make sure anything is COLD when you unscrew anything you heated to stress relieve.
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Gotta Fly...
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[baldcaldwell]

... Heat is applied to neutralize the tension that built up.

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I hear you... Unfortunately major fuel components (gascolator, boost pump & inline filter) are inches away from this panel. The gear struts are also oil filled and have rubber and neoprene surrounding them. Of least concern is that the panel has been painted...

[planecrazzzy]

Well there you go... It can't be done.
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Gotta Fly...

[cub builder]

I've done upside down wet layups with fiberglass and carbon fiber. It's not easy or fun as gravity is always there and this stuff wants to fall off. If you have little composite experience, it's going to be a very frustrating, messy experience. About the only way to accomplish a wet layup while fighting gravity is using the plastic wrap method. I've had some moderate success with this method, but isn't something I'm anxious to do again. It would be easier if you made a jig to hold the piece in the shape you want, then use it as a mold to fabricate a new piece working right side up on a bench. Then it's easy!

One thing I didn't see in your post was what grade and hardness aluminum was used to construct the existing part. Study your aluminums and hardness for forming to what you need. More than likely the existing panel is 2024-T3. Look into 6061 aluminum and the various hardnesses available and their forming qualities. There are a lot of different Aluminum alloys and most are available in various hardnesses. Each one has different working qualities for stiffness, formability, and resistance to cracking. That doesn't look like a difficult piece to form. You could form it from dead soft material, then use that as a form to do a composite layup on the bench.

[baldcaldwell]

I've done upside down wet layups with fiberglass and carbon fiber. It's not easy or fun as gravity is always there and this stuff wants to fall off. If you have little composite experience, it's going to be a very frustrating, messy experience. About the only way to accomplish a wet layup while fighting gravity is using the plastic wrap method. I've had some moderate success with this method, but isn't something I'm anxious to do again. It would be easier if you made a jig to hold the piece in the shape you want, then use it as a mold to fabricate a new piece working right side up on a bench. Then it's easy!

One thing I didn't see in your post was what grade and hardness aluminum was used to construct the existing part. Study your aluminums and hardness for forming to what you need. More than likely the existing panel is 2024-T3. Look into 6061 aluminum and the various hardnesses available and their forming qualities. There are a lot of different Aluminum alloys and most are available in various hardnesses. Each one has different working qualities for stiffness, formability, and resistance to cracking. That doesn't look like a difficult piece to form. You could form it from dead soft material, then use that as a form to do a composite layup on the bench.

All great thoughts! Thank you very much!

[planecrazzzy]

If you used foam to hold your Fiberglass in place... Just sand the foam away after it dries ...?
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Gotta Fly...

[Airmutt]

If installing this panel is a big hassle as you say, it seems to me it would worth your time to build yourself a mold. First question…are you satisfied with the fit and look of your panels once in place? If yes, I would take poster board, not foam board, and create templates at a spacing close enough to capture the compound curve, say at 1 inch spacing. Then take some sandable foam and slice it to match your template spacing. Assemble the templates and foam together and sand your foam till your templates are just exposed. Now you’ve got your shape and you can do your layup without fighting gravity.