Spar width vs mylar drawing

[epapa]

I have my forms all built , or at least thought I did. That was until I made a full size layout of the spar from the dimensions on drawing 5. It shows 7 5/8" to what appears to be the outside of the 0.100 radius. It that is the case, the master mylar and that dimension disagree. The mylar measures 7 11/16" at the spar line. Did I do wrong in making all my forms confirm to the inside of the mylar layout line?

[Enewton57]

Don't forget to account for the thickness of the aluminum when comparing the forms to the drawings. After you bend the ribs over the forms, the ali]uminum thickness will be additional.

[epapa]

Thanks Eric. I think I have my brain working now. I hate to do it but I must cut that thickness off the forms.

[DRLPatrol]

Eric, On my patrol plans, don't know if the LSA is the same, the mylar sheet is called "rib form block layout". I figure that means the flange and skin thickness has been accounted for. It is aprox .075 shorter at the main spar than the scaled drawings.
Am I right?
Doug

[Enewton57]

Yes - I think Bob accounts for the skin thickness when he draws the spar. At any rate, I built my form blocks right to the mylar drawing and then when I bent up the spar webs, I made them fit the ribs.

[DRLPatrol]

Thanks, That's what I was planning.
Doug

[epapa]

If you overlay the mylar master airfoil drawing overlaying aileron drawing number 10, you will see that the aileron is as much as 7/32" higher than the mylar. Does the aileron really raise that much higher than the adjacent airfoil? I took a picture but it would not load.

[epapa]

I finally was able to talk with Bob. The aileron really is 7/32" different in elevation from the adjacent tail ribs. Bob said it was done that way to make the ailerons more effective. Thanks for all the help.

[epapa]

I am bending the flanges on the center ribs using the technique Bob has in the book....waxing and a wood stick. The 30 degree flange is quite easy to do, but I have not been successful with the second part of that procedure in the manual....making the ribs flat by using the rear of the wood flanging tool and "pressing down". Please give some clues about how to do that and where exactly to press down. Thanks.

[Chewie]

Does this help?

[epapa]

Thanks. It works well.