Mega Der Red Max fin question

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rocketpunch

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Hi Guys,

I'm a BAR about to embark on my first mid-power build, a Mega Der Red Max.

A couple of my plywood fins have a slight warp in them. Will these straighten out when I glue the balsa to them? My fear is, even if they come out straight after I glue the balsa on, that over time the plywood will want to go back to it's original shape and warp the fin. Anyone else experienced this? Advice please.

Thanks!
 

JumpJet

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Yes, the fins should come out flat if you assemble and let them dry on a FLAT surface. For my lastest built up fins I used Med CA for laminating the parts together. You have to be quick to position the balsa in the correct place since you only get a few second. Slow setting epoxy works great as well. Just be sure to place something flat over the fins while they are drying and then of course add weight on top of this. When using epoxy and before adding anything on top of the glued fin stack I use just a couple drops of CA in a few places along the edge of the stack so the three laminates of wood don't move. This way why you add your flat plate and weight on top, nothing moves.


John Boren
 

fyrwrxz

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I use two thick glass plates and a bag of lead shot. My buddy uses 1' x 1' ceramic tile and bench weights.
 

dhbarr

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I use two thick glass plates and a bag of lead shot. My buddy uses 1' x 1' ceramic tile and bench weights.
Home Depot / Lowes usually have partial boxes of ceramic tile in clearance, FWIW.
 

TangoJuliet

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Cut your balsa sheeting over-size, brush 30 minute Epoxy onto your plywood internal fin frames, and as stated, weigh it all down and let dry overnight. Once dry, you can trim the balsa sheet to the final outline of the fin and then sand to round off the leading edges.
 
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