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Spar Cap Layup Failure


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I layed up the top and bottom spar caps only to find there was a strip of bondo embeded around the corner of the shear web under each spar cap. This happend because I put a bunch of bondo along the boards used to create my dams. I didn't like what I saw at the time but I figured it would be easy enough to scrape out a little "fillet" of bondo.


I started with my grinder to get it out and it apears I will have a channel carved out between my spar cap and the shear web almost the entire length of the shear web about an 1/8" deep if I'm to get the bondo out. It's also impossible to crind out the bondo without damaging the underlying spar cap layup.


I think I'm going to scrap the part. Bummer after all the hours I've got into it but I just don't feel comfortable with it.


Any one have good success creating a dam that is both sturdy, doesn't create bondo between the spar cap and shear web?


Maybe the best bet is to use a board that goes all th way to the table and ensure the bondo used is put on there well below the rounded corner. Then the long fibers will fall down into the crack or rounded area and fill it up nice and strong.

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I used a strip of wood that was a couple inches wide and covered in box tape as a dam. I only bondoed at the bottom of the strip. It was sturdy enough, but not a perfect seal. So, I put a flox fillet in the corner formed by the dam and shear web when I did the spar cap to prevent epoxy runs. It mostly worked. Keeping the flox a little dry helped.


It sounds like you have a bondo fillet instead of a flox fillet there. If you can remove the bondo without damaging the spar cap tape, then you can replace the bondo with flox and your result will be no different than mine. It is OK to make a fillet there of flox. Spar cap tape does not have to fill the entire triangular corner area.


If you are concerned that you damaged one or two layers of spar cap tape by removing the bondo, then you could always add another ply or two on top of your current spar cap. That would add weight and thickness, but sometimes you just do what you need to do for peace of mind. But, you couldn't have damaged much of your spar cap if the depth of the groove is only 1/8" deep and most of the removed material was bondo.

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