Adding spars:
More:
It's hard to see it, but I ran a stripe of TB II glue along each spar. I had planned to brad nail too, but it didnt seem necessary. Too many spars? I have no idea. I wanted to make sure I supported the curve, both inside and outside.
I used 1x2s for most spars on the curve. But for the bottom two I used 2x2s. I plan to add a piece of diamond plate once the outer skin is on, and this will give me the material to fasten to.
And that is the stock fender doing double duty to help hold that top spar in place while the glue dries.