Thorp Air Command - T18.net

This is is a picture of the rear spar - left Outer panel Folding (S-18) wing. Left outer wing panel. Both outer wings are constructed similarly. It appears the rear spar is two peices with a gusset and splce and NOT a single continious peice.



This rear spar is damage towards the left side (of the photo). With this splice plate, it appears I will have to replace only that section which is bent and unusable.

Is this two peice rear spar OK? If not I will replace both of the rear spars entirely to have a single continious peice.

Please advise!

Thanks,

Tom D

The reason this spar is made in two pieces is to have the bend across the gran and not linear with grain. The plans calls for it to be made either way. I prefer the cross grain. This way you can make the spar using 4 foot wide material and not a 8 foot piece.

OK, more of my ignorance showing. But I want to be sure I undertand correctly.

Explain what you mean by cross grain versus along the grain.

I assume you mean how the aluminum in the sheet as it is manufactured is oriented. Assuming a 4x8 sheet of aluminum. That by making the spar from the 4 feet in width, the grain is across the 4 foot wide sheet versus the manufactured grain being parallel with the length of the 8 foot long sheet.

Grain runs length wise , when bending aluminum you want to take advantage of the grain when making bends. Its stronger and less apt to break. If you look at a sheet of 2024 you can see the grain and generally runs parallel to the writing on the sheet.

Yep, mine is built the very same way, it has the splice also.....Dan

A splice is permitted on the rear spar . I believe it is in the plans ? Mine has the splice also . It came that way from Ken Knowles or Phil Tucker ?

RB

OK, the only reason I posted this was because on one of my other previous post I mentioned that the rear spar I had was spliced. And I think someone responded saying they were not sure that was correct. So I wanted to post out a picture. Sure I could have looked through the stack of drawings to find the right one. Or I could post a picture and get back 10 responses in the same amount of time it would take me to sort through 1/4 of the plan drawings.