i find it really hard to blend the rear kneefy rails edges into the rounder side rails and i was wondering how you guys do it?
for me : i try to blend as much as i can when i shape de foambut i keep the rear rounded so the fiberglass can mate the foam when laminating
then when doing the hotcoat, i finish the edges with reversed masking tape at the back(blocking the resing so the edge become sharp instead of letting the resin go down) during the hot coat
then i just try to blend as much as i can sanding of f the extra resin.
The results are far from best since this was my first board but i want to improve myself and i’d like to know other possible techniques
do i have the good technique only with bad experience?
Not exactly sure what the question is! Probably because of terminology? Knifey rails to me means thin rails like on a hull, where the bottom curves up and the dome of the deck curves down, and the rail itself is thin where they meet, with not much meat to round off.
Hard down rails in the tail are pretty common around here, and if you like a square edge for release, then you're best served by damming the resin during the hot or gloss coat, especially if you wrap your rails, since fiberglass cloth does not like to wrap around a 90 degree angle. I keep a small radius along the rails in back while shaping, then dam the resin later.
While shaping, I shape the top half of the rails from above, and the bottom half from below. I just remember to barely touch the rails in the tail when the board is bottom up, and gradually work the rails more as I near the half point and forward. If I'm going for a "beak" nose, then I back off again at the very tip. Finally, I put the board on edge and clean everything up at the last.
I dunno if this answers your question, or helps, but hey I tried!
Like Huckleberry said, break the hard edge of the foam a little so the fiberglass wraps around without air bubbles. When screening the rails I give one pass over the tail’s hard edge to soften it.
When taping off your resin dam in the tail for hotcoating, extend the dam a little farther than the shaped hard edge. That way you can fine tune the transition when hand sanding the rail