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KBBS Archive 10,000
Re: Molded fiberglass kayak seat
Posted By: mike allen In Response To: Re: Molded fiberglass kayak seat (Hank)
Date: Monday, 27 September 1999, at 3:33 p.m.
> Hi Ross,
> The fiberglass is run down on all 4 sides of the mold to form a
> "skirt". The fiberglass in the middle of the side and back
> panels is only 2 or 3 layers thick (3 oz cloth) - not rigid in itself but
> then it is only there to make sure that the corners stay straight.> Getting the seat to sit solid in the 'yak can be a bit tricky because you
> can't see what you are doing with the seat in the cockpit. After the first
> layer of fiberglass had cured enough to handle, I removed it from the mold
> and rough trimmed it with a pair of scissors - easy to do now. I figure
> that I might as well find out if I screwed up now rather that after I had
> wasted more time and materials. I had to gauge how much material to trim
> from the "skirt" to fit the seat to the kayak. I drilled two
> small holes through the lowest part of the seat as far from the center
> line as I could so that I could use a piece of wire to probe through the
> seat to the bottom to find out what gap there was and how much material I
> had to trim from the "skirt" to get the seat to settle on to the
> bottom of the kayak. Worked pretty well.> The homemade mold release is a recipe that was passed to me by an European
> craftsman. Could you shave with it? Yeah, probably, but it would not do my
> electric shaver any good ;-). I have been using it for years to make
> detailed plaster castings from plaster molds. Plaster to plaster is not an
> easy thing to release - trust me, I know. The flat test sample I did with
> epoxy (3" x 12" surface) released with NO effort. On a more
> complex mold you have to break the "seal". I ran thin plastic
> ruler around the perimeter of the mold and worked it off with little
> trouble. The biggest problem is that the seat is hard to get a grip on.
> Being just a single layer of glass it is very flexible and you can be
> fairly rough with it. The couple of creases the I made were easily
> smoothed out using the mold as a pattern. In worst case, water can be
> always be used to dissolve the release and separate the mold. If you have
> to go to that extent to remove the part from the mold there may be a
> problem with the design of the mold (no relief angles, negative areas
> [hollows] in the mold etc.). One other thing that I like about this mold
> release is that, being made of soap, it cleans up very easily with warm
> water.> Hank
Hi Hank:
Thanks for sharing with us, Hank. With yours, and Ross's and the chicago swimsuit idea it sure goes a long way to showing ways of making seats.
For some time, I've been mulling over some other similar ideas to making seats and forms etc. and since you're familiar with plasters - you're the perfect guy to answer some questions. I was pondering two different methods:
The first was to put down several (3") layers of very open celled old crappy diseased foam say 2' x 2', and sit down on them to see if they compress to a semi ok seat shape. Assuming so, mix up a bunch of thin slurry plaster, and pour it into the ctr of each foamy and stack them up again (a layer of plastic sheet under the top foam) and then sit in it for a while? Would this work? Is plaster thin enough to get absorbed in foam? Quick? Would the foam actually hold its shape after setting? would the foam sort of act like a matrix? Would this end up lighter? Any thoughts?
Then throw away the bottom 2 layers of foam, get a thin 2'x2' pc by say 1" or so saturate it in plaster, throw some plastic sheet in the bottom of the yak, put in the 1" saturated foam, then the plastic separator sheet, put in the original top layer plaster foam form, and sit in it and let the bottom set up. Shape the sides and you get a form that follows your butt and also follows the bottom of your yak.
The second method is real simple and quick, but a little harder to explain. Put a couple layers of 2'x2' @ 3" foam in your yak. Drape a layer of plastic sheet across the cockpit opening and sit in the yak carefully in order to not rip the plastic. Hop in the yak. Between the plastic and the yak sides where cheekplates would go, push in some blocks of scrap foam so the plastic is pressed against you. Now, you or your winger cuts the plastic on the outside of the coaming and tapes it in place. Get out and lay in 2" wide scraps of cloth bedsheet all over the area - duct tape at the top of the coaming, and pour in the plaster. Lay another sheet of plastic over. Put on your wetsuit w/ a couple prs of pajamas on ( to account for the future glass layers) and sit in the plastic. Tape it firmly over the coaming as before. After setting, pull the top plastic, sand the wrinkles, put on a release and lay up some glass. I think this might make a very light simple form. Thougths?
A third simpler approach would be to just put the foam down anywhere, put on some plastic sheet, lay out the plaster w/ cloth, put another plastic sheet, sit down and gather up the ends of the first plastic sheet closely aroung you - maybe use duct tape and read a book for a while (15 mins?). Then you get a thin form that moulds around your body for as high as you wish. Sand out the wrinkles.
These seem a coupla two or three simple plaster approaches - whatya think Hank?
- mick
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