• The Biplane Forum is a large global active community of biplane builders, owners and pilots. From Pitts to Skybolts, to older barnstormers, all types are welcome. In addition to our active community, our content boasts exhaustive technical information which is often sought after for projects and maintenance. This information has accumulated over the 12+ years the forum has been in existence.

    The Biplane Forum is a private community. Subscriptions are only $49.99/year or $6.99/month to gain access to this great community and unmatched source of information not found anywhere else on the web. We are also a great resource for non biplane users, since many GA aircraft are built the same way (fabric and tube construction).

Doug Fir VS Spruce

Jerry

Radial Skybolt Builder: 220.45% completed
*
Joined
Aug 22, 2006
Messages
4,489
Reaction score
532
Location
South Jersey
Here's a short article with good, basicinformation on the differences between the two as far as us biplane builders are concerned.


Summary:
1 - Bending Strength: Fir is 23% stronger than Spruce
2 - Elasticity: Fir is stiffer than Spruce (no % mentioned)
3 - Compression Strength:
a. Parallel to grain Fir is 39% stronger
b. Perpendicular to grain Fir is 55% stronger
c. Not only is a Fir spar stronger, but the bearing strengths of bolts in Fir
are higher by the same percentage
4 - Fir is 23% stronger than Spruce but weighs about 26% more


When choosing Fir look for VERTICAL grain that is from 8 to 14 grains/inch in 15"


uploads/20070918_060821_DougFirVsSpruce.pdf
 

Latest posts

Top