Original Posted By: Michael Perez
For those of you who missed this excellent post (and calculation---thank you Bill!) from Bill Church on July 4thit might be of possible interest for those using the Riblett airfoil.Mike C.There was a discussion about wing incidence about three years ago, and at that time I created a couple of drawings to illustrate the relationship between the cabane strut lengths, and also between the chord line vs the bottom of the spars. They are attached again to this posting.For the "to the plans" Pietenpol, the 1" difference in cabane struts creates a 2 degree angle. Added to this is a 1 1/2 degree angle formed between the chord line and the bottoms of the spars (since that's where the cabanes attach). So the effective angle of incidence between the airfoil chord and the top longeron is 3.5 degrees.For the Riblett 612 airfoil, there is a 2.1 degree angle between the chord line and the bottoms of the spars. So, if a Riblett 612 airfoil is mounted on "stock" cabanes (front 1" longer than rear), the effective AofI would be 4.1 degrees.If the front and rear cabanes are made equal lengths, with the Riblett, the effective angle would be reduced to only 2.1 degrees - almost 1 1/2 degrees less than the "to the plans" Piet.In order to produce the same 3.5 degree angle, but using the Riblett 612, there should be a difference of approximately 11/16" difference in cabane lengths (front vs back).Food for thought.Bill C.http://forums.matronics.com//files/piet ... ______Date: Wed, 23 Jul 2014 09:45:03 -0700
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