spar question

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jgnunn

Well-Known Member
Joined
Aug 7, 2005
Messages
175
Location
Jarrell, TX. Fly out of Taylor-T74
hi. I am making routered ply ribs. Regarding the spar apertures in the ribs:

http://www.65degrees.net/Pict0899.jpg

the nature of the router cutter of course causes the corners of the apertures to be radiused...is it safe to round the edges of the spar to fit thru the aperture, thus losing (strength?) material from the spar, or should i go for a smaller radius in the corners of these apertures?
 

Medic9204

Well-Known Member
Joined
Jan 22, 2005
Messages
46
Location
Williamsport, Pennsylvania
Alternative

Instead of rounding the spar to fit, notch the rib to fit using a small hand saw or wood file...router it just a bit heavy and take it down to specs by hand.

You PROBABLY won't compromise the spar by rounding it, but do you want to find out you're wrong at 5,000 ft? I'm pretty sure you'd hit the ground before the wing.
 

jgnunn

Well-Known Member
Joined
Aug 7, 2005
Messages
175
Location
Jarrell, TX. Fly out of Taylor-T74
yeah i decided to tighten the radiuii... i used a smaller bit - 3/16 [3/32 corner radius], i got to thinking removing material from the spar didnt have any feel good factor about it whatsover...
 

Medic9204

Well-Known Member
Joined
Jan 22, 2005
Messages
46
Location
Williamsport, Pennsylvania
That should work, just remember that you don't want to lose strength in your ribs, either. That can be just as problematic, even catastrophic. There's arguably less risk, though.

In the end, I'd just make it to specs unless you're a structural engineer and can do the math.
 

MarkP

Member
Joined
Sep 22, 2005
Messages
9
Location
McKinney, TX
The problem with radiusing the spar is that the design probably shows a spar cap strip, that is glued top and bottom to hold the rib in place and a flat surface to attach the leading edge to. Narrowing that area will cause problems later. I've built several sets of ribs out of plywood and have had no problems, they look weak seperately, but as a wing ,very strong.
 
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