Crosby CR-4

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Tiger Tim

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Apr 26, 2013
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The stated 600lb higher weight of the CR-4 over the SK-4 seems high, I wouldn't have thought the aircraft large enough to have an extra 600 pounds in it.
IIRC the CR-4 was designed for a much larger engine than what it got so that would explain some of the weight difference. Folkerts’ racers always seemed pretty wispy and minimalistic so that probably accounts for some more. Still, a weight difference of an entire empty Cub between two tiny racers is wild if true.
 

jedi

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Sahuarita Arizona, Renton Washington, USA
IIRC the CR-4 was designed for a much larger engine than what it got so that would explain some of the weight difference. Folkerts’ racers always seemed pretty wispy and minimalistic so that probably accounts for some more. Still, a weight difference of an entire empty Cub between two tiny racers is wild if true.
Was the 600 pound increased empty weight what the CR 4 was the designed as with the larger engine installed. If not part of the weight increase would be in the nose to keep weight and balance in limits.
 

Magisterol

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Jul 22, 2021
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Now that I figured out to attach the spars in the middle, how to build a leading edge with a variable radius along the span?
 

BJC

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Now that I figured out to attach the spars in the middle, how to build a leading edge with a variable radius along the span?
Lots of Midget Mustang leading edges have been formed by clamping boards to the skin trailing edges and bending the skin by pressing the two boards together, using more pressure at the outboard end.

The SX300 kit uses stretch-formed leading edges.

Those are the two extremes in homebuilding. The MM technique takes some finesse.


BJC
 

TFF

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Apr 28, 2010
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I would pull the skin around a leading edge buck; trim excess. Kind of between the two ways BJC offered. Stretch formed would be the nicest if you could pull off the tooling.
 
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