Spar cap day! The room is preheated overnight to 26C and the epoxy is warm in its low tech cardboard box with a 30 watt globe inside.

Straightening the UNI is quite a task and gobbles up a lot of time during the layup. Some people use a comb. I don’t get that. We unroll the cloth on the job about half the longest length. Pull the key thread and then while holding down the cloth lightly, we pull the cross threads in one long piece on to where we have unrolled the UNI to. So now we have the long fibers unsecured or maybe with just a touch of epoxy holding them from below.

Once the cross threads come out the fibers go a little wiggly as they have been held in a slight wave formation due to the threads

Then with Michael securing one end we start at one edge and I’ll pull one bundle straight. Movement can be as much as .25″ Michael calls it good as my head is down looking at the fibers. Then I carefully grab the next bundle. I use dental tools to pick it up and help me separate from the other bundles. You can see in pic 1 that there are a few of them. My stick keeps the plys off the top as once they get epoxy in them chances are moving anything will disturb the ply below which we may have just straightened and wet out.

Back to the plays now we do #3 bundle, Michael calls good and I carefully put it down and pick up the next one. Sometimes I have to pull these quite hard to get movement. When they all look good and we are at the opposite side we carefully pat them down and the epoxy below will hold the run of fibers as we placed them.

Now we go to the other end of the straight run and in this case carefully roll out the uni in the trough until we get to the kink in the spar cap at FC1. We roll just past that and then again pick out the key thread and the cross fiber key really carefully. Raising the roll on sticks (see the first pic to see what I mean by a stick!) where I have to pull them straight is really important.

Working on straight fibers

Right wing top cap done

Weighted for the cure