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What is the hard shell technique?


nadt770
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A search on this doesn't get me much.

Must be the wrong search. :)

 

Open Cozy newsletter #76 here and search within for 'hard shelling'.

 

I found that by searching here for 'hard shelling'.

 

I will admit that was NOT what I thought 'hard shelling' was...

Jon Matcho :busy:
Builder & Canard Zone Admin
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Resume building a Cozy Mark IV

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O.K. thanks. I used "hard shell" for the search. Looks like it is not a good process.

You might want to search the COZY mailing list archives before making that judgement. There have been many discussions over the years on this technique, and it has it's place. When done correctly, the strength is more than adequate.
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You might want to search the COZY mailing list archives before making that judgement. There have been many discussions over the years on this technique, and it has it's place. When done correctly, the strength is more than adequate.

On my dragonfly, I hard shelled the wing and wet lay-upped the canard.

 

I found the hard shelling to be much more time consuming with little real benefit. :mad: If I were to hard shell again, I would peel ply the micro smear.--

 

I shell not do it again, however!

 

Rich

I Canardly contain myself!

Rich :D

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Hard shelling can allow you to do big layups by yourself.

 

The problem I've found w/the conventional approach (spreading micro on surface, then laying down cloth, and then expoxy) is that if you have to move the cloth at all (to straighten the fibers) it tends to pull up the wet micro, leaving patches of foam without micro.

 

This is just a cosmetic issue, as the epoxy still soaks through the cloth and into the foam, but it makes the surface look ugly.

 

On the other hand, hard shelling allows you to easily slide the cloth back and forth to get the fibers perfectly straight. There's no wet, tacky micro beneath to grab the cloth and distort it. This allows you to do big layups by yourself, and it also allows you to break the layup into two parts -- the micro hardshelling, and then the cloth/epoxy application.

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Nice concept but it didn't appeal to me. I tried it on a section of the nose to repair an area. After the top plies hardened I could press against it and it would make cracking sounds like celery or nachos. I'm assuming the hard micro is cracking beneath the glass plies. It doesn't appear to be as strong as when the foam gets wet microed before the plies.

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