After making a big 137x43 cedar strip board with lots of rocker last fall, I decided to make a smaller flatter one with channels for when conditions are stronger. Why channels? Why not?
Seriously, the challenge of shaping and glassing channels was interesting, plus I wanted a different feel.
So I started this board in March hoping to finish it for an April Hatteras trip.
There were some bumps along the way. Mistakes were made ...
It had a bad batch of epoxy
on the deck and so after Hatteras I came home and had at it with heat gun, alcohol (careful
) and scrapers, sanders, etc.
Then the rocker wouldn't come right, and it was too bendy.
Finally after reworking, shaping, extra laminations, etc., it's done. (?)
Unfortunately the extra work did not allow for as good a finish as I hoped, but i left it clear anyway.
Western Red Cedar blank 1/2" strips glued up with epoxy.
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The center section between the channels was glued up first and the V-hull form shaped into the tips by hand with saw, plane and sanding blocks. Then the outer strips were added to the blank and the outline was cut with a router and epoxy rail poured.
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The core was freed from the blank and the deck contour was shaped by routering ramps into the tips to create a taper roughly following the channel/hull shape beneath. The deck shape was smoothed out with RO sander, scrapers, plane etc. until somewhat fair and symmetrical.
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Inserts and filled epoxy fin blocking were cut in with the router and filled.
The core was cleaned up and sanded, then glassed, which was where the problems occured.
Eventually it ended up like this though:
Deck stringers (added after to adjust rocker and flex):
6 oz e + 4 oz e glass x 3" wide strip capping uni carbon
6.7 oz,1.75" wide unidirectional carbon fiber
6.7 oz 1" wide uni carbon fiber
6oz e glass patch beween straps
6 oz e glass
7/16" (11mm) cedar core
6oz e glass
4oz e glass
4 oz e glass patch between straps
That sounds like a lot of glass, but I don't think the board will be too stiff, keeping in mind a significant part of the glass is "remedial," laid over the first layer, which was sanded and so loses some of its stiffness.
I had hoped the weight would be about 2.7-2.8kg, but it's about 3kg instead. Not bad considering the extra laminations I guess.
For what it's worth, I tried vac bagging and spray glue for glassing the channels.
Spray glue works at least as well.
I used carbon because the board was too wiggly and I didn't want to add another layer of glass over the whole deck. I'll see how it does, feels ok on land...
22mm rocker (I wanted it to be 25 to 30
Channels 3mm at tips to zero 30cm in from tips.
Concave 3mm center, zero at tips.
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Were the channels worth it?
Will the flex be good?
Will it ride ok with only 22mm rocker?
Is it good to change lots of variables in your design at once? (
I'll let you know....