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Old Aug 03, 2006, 06:42 AM
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Joined Jun 2006
6 Posts
Help!
Bagging wings - Hmmm, I must be doing something wrong

Hi Guys,

Please assist with a problem I seem to be having on my bagged wings.
When the wing comes out the bag, the surface of the wing is not completely smooth as you would normally expect. If you run your fingers across the surface of the finished wing, in places, you can feel a bit of roughness as if the glass fabric is a bit exposed and careful inspection of the wing you can see fabric pattern on the surface of the wing. Any ideas what could be causing this.

Some more detail:
I'm from South Africa and canít get mylar here so I'm using 0.3mm PVC sheeting, itís extremely smooth on one side and once removed from the bag there is no sign of any of the epoxy still sticking to the pvc. The pvc is polished using car wax and sprayed using normal aerosol spray paint.
The glass is about 30 grams (not sure what the ounce conversion is). Since these are slope wings weight is not a problem so I have always made sure I have used plenty of epoxy on the layups.

I plan on putting a new wing in the bag this weekend so I am looking for suggestions on what to try to avoid the problem.
Any advice would be appreciated.
Thanks
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Old Aug 03, 2006, 09:39 AM
DLD
David Layne
Tracy, Ca
Joined Jun 2004
665 Posts
Normally I would say that the fabric was not completely wet out, but you say you used lots of epoxy. If you are sure that you have been wetting the fabric completely, you might try adding a little silica to the epoxy, it helps the epoxy fill voids and not wick away as much. I always wet out the fabric really well with more than enough epoxy, then soak up excess resin with paper towels before bagging, and never experienced a problem.

Good luck,

David Layne
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Old Aug 03, 2006, 09:52 AM
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Joined Nov 2004
245 Posts
I had this problem on my first attempts at bagging. My glass was not properly wet out because I tried to brush and roll the resin through several layers of fberglass at one time. While this will work with lighter cloth, heavy cloth needs to be wet out one layer at a time. Keep trying, you;ll get there.
Paul
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Old Aug 03, 2006, 10:21 AM
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Joined Jun 2006
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Thanks, the other though I had was that the foam may not be well sanded so the epoxy is pulling into the small cavities in the foam and drying out the glass. I'm using white foam and bagging at about 17 in/hg ??
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Old Aug 03, 2006, 11:10 AM
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chlee's Avatar
Atlanta, GA
Joined May 2000
602 Posts
Is it expanded bead foam? If it is, I wonder if indeed the epoxy is being soaked up in the space between the beads...

Also, does 17 in. of mercury not deform your foam?

- Chung
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Old Aug 28, 2006, 04:50 AM
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Joined Jun 2006
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Feedback

Hi Guys, Just some feedback. Thanks for the assistance and suggestions. The attached pic are the result of my latest attempt. I was quite pleased with how the wing turned out. I made the following changes to my layup
1) Started with using 1oz glass before using the heavier cloth
2) layed out all the glass before applying any epoxy
3) turned down the vacuum a bit
4) Borrowed the electric blanket to keep the wing nice and snug while it cured.

All seemed to turn out OK this time.
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Old Aug 28, 2006, 04:14 PM
chetosmachine's Avatar
Madrid, Spain
Joined Sep 2004
1,102 Posts
If you use a thicker pvc sheet, something around 0'8mm, you will get a better surface.
You talk about 30g glass, that's 1oz. Then you talk about 1oz glass. What has been your lay up?
I'm going to make a phew wings, so any input is welcome
regards,
Chets
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Old Aug 29, 2006, 01:59 AM
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Joined Jun 2006
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Hi Chets,

I found the thicker PVC to be problematic expecially when you try to get it to conform arround the LE. You could however try scraping the LE section of the PVC to try remove some of the thickness.

The layup I used was 30g onto the sprayed PVC then 200g on top of the 30g. Then applied the epoxy to both layers at the same time.


Cheers
A
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