The spar caps are a critical structural item on my plane build and I wanted to learn about how to do this work before attempting it on the real thing.

My goal was to build a section of the CS spar cap and find out how thick my special UNI tapes will layup per ply and to develop a good technique.

First step was to find a piece of scrap divinycell. Then I marked out a 3″ trough, actually 3.1″ to match my 80mm tapes. Just for the practice I put in a two ply UNI shearweb. I hard shelled it just to see how much extra time this added to the job and to try using power tools for sanding.

It adds quite a bit of time and while I think this method is good for some areas, in the end I used a wet micro layup for the real job later. I think the foam cells are so small here I’d go for the primary bond for the extra strength and skip all that sanding.

The open cell wing foam is another story.

Cutting a test cap trough

Laying up the test shear web

Peel ply the web