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Vacuum Bag and Polyhedral Wings

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Old 04-10-2011, 05:15 PM
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edulago
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Default Vacuum Bag and Polyhedral Wings

Hi Everybody,

I'm building a new sailplane and this time I would like to try the vacuum bag technique. My question is: What is the best strategy to build a polyhedral wing using vacuum bag? Should I work each panel individually or try to vacuum bag the entire polyhedral wing? Nowadays I build my wings using foam cores and fiberglass spars (one spar each side, a single piece from one wing tip to the other wing tip).

If I work with the panels individually, I will need to split the spars across the panels (I never did this before, I'm afraid this will make the wing weaker to the hi-start), but vacuum bag the entire polyhedral wing maybe will be hard to avoid warp...

I read a lot of articles on the net about vacuum bag, but in all examples people are building flat or low dihedral wings...

Sorry about my newbie question...

Thanks
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Old 04-10-2011, 05:47 PM
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Default RE: Vacuum Bag and Polyhedral Wings

Are you planning on bagging with mylars? If so, you can do small angles but larger ones become problematic. The mylar is unable to handle the compound curves at the junction. Typically 3 degrees is the max. You typically will need tomake a bed with the dihedral in it. The bed is needed to hold everything in the correct orientation (gemetric twist, straight, dihedral angle, etc) while the wing undergoes vacuum.
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Old 04-11-2011, 04:18 AM
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Default RE: Vacuum Bag and Polyhedral Wings

Just built straight panels. I used CF tubes for spars so I made a flat center section, with plug in tips with all the dihedral in them. You could make a Paragon like wing if you accept that you would have to join the center section afterwards.

You could vacuum bag with all the dihedral, but the Mylars would have to be trimmed to fit the joints. You would have to build something to hold the dihedral angle in the beds and cores. Straight panels joined is the way to go.
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Old 04-11-2011, 03:21 PM
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Default RE: Vacuum Bag and Polyhedral Wings

Hi,

thanks for sharing your experience... I will try to work with straight panels this time... I think it will be easier too...

thanks again...
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Old 04-14-2011, 05:44 PM
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Default RE: Vacuum Bag and Polyhedral Wings

Try Phil Barnes videos. Just do a search for his name and vacuum wings or foam. Read the RCG write up too.
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Old 04-15-2011, 10:04 AM
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Default RE: Vacuum Bag and Polyhedral Wings

I have Phil's videos, his wings are all flat panels.
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Old 04-15-2011, 11:10 AM
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Default RE: Vacuum Bag and Polyhedral Wings

One had dihedral but he explained covering it, not joining it.
Now I'm curious to see how he does it.
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