Forward Flange Modification

Could someone please shed light on the step outlined below?



In Section 5.2 it talks about tapering the forward flange on all the ribs, but the picture of the rib shown on that page doesn't appear to have nearly the amount of material removed as this illustration suggests. It appears, at least on the topmost radius, that the flange would be cut away almost to the first rivet hole. The radius on the left would leave the flange to a very fine knife edge. Am I looking at this correctly?

Thanks in advance.

I vaguely remember that part.

However, I would not be worried about removing too much by following the drawing. Much of the strength of a flange comes from the bend itself, and at the ends, this is especially true. You could probably cut off the flange material at a 45? angle from the end and not affect the strength very much at all.

The reason for the trimming is to not adversely affect the smooth shape of the overlying skin. You aren't sacrificing very much strength to achieve that and the resulting smoothness is a good tradeoff for the minor loss of material.

Flange

I had this same question. I tried to modify as the plans suggest and ended up taking too much metal off. The edge distance was no longer acceptable to the rivet location, so I got to order my first replacement part. On the second go-around I simply smoothed out the radius on the scotch bright wheel and it fit fine.

This was my exact concern! Sorry to hear about the replacement part, I've already ordered another spar - due to stupidity. I'll go easy with the scotchbrite wheel on the flange, and maybe test fit the assembly while sneaking up on it.

dclaffey said:

I had this same question. I tried to modify as the plans suggest and ended up taking too much metal off. The edge distance was no longer acceptable to the rivet location, so I got to order my first replacement part. On the second go-around I simply smoothed out the radius on the scotch bright wheel and it fit fine.

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