Team Seacats

So the fin is roughly patterned.  I learned a bit making this and although the final versions will be made from a mold, I’m not convinced that I can achieve an high level shape to the foil using this method from which to make the mold.  It’s close, but it’s not perfect.

I started out by laying up and vacuum bagging a sheet of carbon on a waxed piece of Lexan.  Two layers of 5.7oz fabric were followed by two strips of 1″ uni-directional carbon tape, wetted out with epoxy, and allowed to cure overnight under suction.  I then trimmed the sheet, leaving the tape in roughly the middle of the cut sections (a little bit forward to accommodate the offset foil shape…that will make sense in a minute).   I then took the aluminum strut and drilled a series of 3/8″ holes and countersunk them significantly.  The holes are to allow the filler epoxy through so it can bond to both sides.  The bond of epoxy to aluminum can be good but it is sometimes suspect and this should help ensure a very good bond.  Besides, the aluminum adds practically no strength in this part of the layup.

I then masked off the carbon sheets as to not scratch them or get epoxy on them, mixed up some resin thickly with microballoons and black die, and slathered up the leading and trailing edges and the aluminum strut taking care to fill in the holes.  I then applied a bag of clothes pins to the trailing and leading edges one by one working my way down the foil to pinch the ends together.  I moved them around slightly during cure to try and avoid visible pinch points.  Once that was about 80% cured, I came back and filled the front and back hollows between the strut and edges with epoxy mixed with microballoons and chopped glass fibers and again added black die to the mixture.  Everything set nicely and the foil looks pretty good for a first attempt.  In hindsight, making a tape hinge and closing “the book” around the aluminum strut for the trailing edge would have resulted in a much more consistent trailing edge.  A good bit of the front will be shaved off as I shape it to a decent foil shape so it wouldn’t have mattered to have a few minor pinch marks there.  You can still see some irregularity from the clothes pins.

I still need to do considerable shaping to the leading edge and fair it to the bulb and the hull.