I didn't put a layer of glass in the middle of the foam blank, but in stead routed a groove in the middle of the aft side of the blank and filled that with putty. Before starting shaping the blank I marked the centerline on the putty fill.
After gluing the blank I cut out the center spar, replaced the middle of it with a wood part as high density area and tried to figure out how thick the spar needed to be (taper). After the as always mediocre wrapping-exercise and the not-so-succesful attempt to keep the spar straight while curing the wrap, I tried to glue the spar back in position as accurate as I could. End of the story: it's harder than you might think to properly make and fit the spar.
After the fitting of the spar and after I had glued the HD-inserts in, I started shaping one side with a router..... I found shaping easier than on the rudder, because the centerboard is a bit bigger. I routed mainly in steps of 4 mm.
I didn't try to shape and laminate the centerboard in one go, as I did with the rudder. After shaping one side of the centerboard, I put the first layer of C on together with the carbon UD. While laminating this side I could keep the still flat side of the blank on a straight bench to make sure the blank would cure without twisting. With the sheating on the one side the blank is already quite stiff and strong. It's possible to shape the other side without too much flexing of the blank.
After laminating the second half + carbon, I did second (last) layer of C in one go, like this. I ran out of peel ply, so it's just plastic over the glass with some extra packaging tape to keep the glass in place round the pivot-hole.
Being afraid to make the board too thick, I made the recess for the carbon UD a bit deep, so I had to fill this area after laminating. I had good results using a piece of hard and stiff plastic to 'retrace' the profile (of course with two hands to make sure the spreader closely follows the profile and not with one hand as in the picture)
Recess filled. On the upper part of the centerboard I only filled the recess around the HD-inserts, as this will be the only areas that will bear against the case.
After curing of the first fill I put a layer on the whole profile of the centerboard (not on the upper part, as a smooth finish of that part is of no use). Now I only have to do some sanding, put on some primer and coat the board.
Pleasant surprise: it's possible and not even difficult to get a very nice coat rolling and tipping paint. I only put one coat on and the result was beyond my expectations. I use two part paint, thinned with a special thinner for brushing. The paint self-levels really well. Biggest problem was small rubbish getting trapped in the paint, although I cleaned my attic/workshop thoroughly. Next time I'll wet the floor to get rid of some more dust in the air.
Work on the main hull is starting once again. My brother helped me to trial-fit the centerboard.
Problem: the centerboard can't fold all the way because one edge touches the hull too fast in the area where the upper part of the board folds in (look at the picture below, you'll understand). Problem was solved by put a 45 degree bevel on that side. It seems like with more parts on this boat the design doesn't allow for a big margin for error.
