Notices
Scratch Building, Aircraft Design, 3D/CAD If you are starting/building a project from scratch or want to discuss design, CAD or even share 3D design images this is the place. Q&A's.

Spar Strength

Old 04-10-2007, 10:07 PM
  #1  
Balsa Shavings
Member
Thread Starter
 
Balsa Shavings's Avatar
 
Join Date: Jan 2006
Location: Hog Island, NC
Posts: 67
Likes: 0
Received 0 Likes on 0 Posts
Default Spar Strength

Tell me which spar arrangement is the strongest.

Check Out The Diagrams.

Spar 1 : 3/8 X 3/8 Hard Balsa, 1/8 vertical grain shear webbing.

Spar 2 : 3/8 X 3/8 Hard Balsa, 1/16 vertical grain shear webbing.


Keep The Faith: Johnny
Attached Thumbnails Click image for larger version

Name:	Ki20611.jpg
Views:	12
Size:	96.3 KB
ID:	661650  
Old 04-10-2007, 10:29 PM
  #2  
iron eagel
 
iron eagel's Avatar
 
Join Date: Jul 2004
Location: Middleboro, MA
Posts: 3,275
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Spar Strength

I myself use the two 1/6 inch thick shear webs instead of the single 1/8 inch setup because you have more glue area, and the force is spread out over both sides of the spar. Now the 1/8 inch shear web is probably lighter than the two 1/16 inch setup but the force is spread out more with the two shear webs.
So as a guess, my call is the 2 1/16 setup....
And it will resist twisting more.
Old 04-10-2007, 10:38 PM
  #3  
mmattockx
 
Join Date: Apr 2005
Location: Calgary, AB, CANADA
Posts: 2,428
Likes: 0
Received 1 Like on 1 Post
Default RE: Spar Strength


ORIGINAL: iron eagel

I myself use the two 1/6 inch thick shear webs instead of the single 1/8 inch setup because you have more glue area, and the force is spread out over both sides of the spar. Now the 1/8 inch shear web is probably lighter than the two 1/16 inch setup but the force is spread out more with the two shear webs.
So as a guess, my call is the 2 1/16 setup....
And it will resist twisting more.
You are sort of correct on this one.

Actually, both have the same bending strength based on mechanics of materials theory. But the 2x1/16" webs is much easier to build and has better geometry for the glue. It is also the more STABLE arrangement (less likely to buckle elastically) and is indeed better torsionally as well. I use the 2x1/16" version myself simply because it is so much easier to build.


Mark
Old 04-11-2007, 08:37 AM
  #4  
funkworks
 
funkworks's Avatar
 
Join Date: Mar 2003
Location: Houston, TX
Posts: 487
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Spar Strength

I agree with Mark. I personally like to use 1/4'' balsa cut to 3/8'' to 1/2'' side strips (one of my fav tools is a cheap plastic balsa stripper) to use as spars. Then use 1/16'' vert grain balsa sheer webs on both sides.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.