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KBBS Archive 10,000
Re: Molded fiberglass kayak seat
Posted By: Hank In Response To: Re: Molded fiberglass kayak seat (Ross Leidy)
Date: Monday, 27 September 1999, at 12:48 p.m.
> Hank,
> Nice solution to the custom seat issue. When forming the seat from the
> mold, do you run the cloth down the 4 sides of the mold to create
> supports? I'm just trying to figure out how the seat fits in the boat and
> stays in the upright position.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.
The seat's rigidity comes from the radius on the armrests and the back in conjunction with the shape of the seat itself. The support is from the four reinforced corners and where the bottom of the seat comes in contact with the floor of the kayak. The strength is from the shape rather than the thickness of the fiberglass - an egg is next to impossible to break in direct compression - that is what I was copying with the curved fiberglass surfaces.
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.
> How did your homemade mold release work for you? Can you shave with it
> too?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.
> Hope we can see a photo of the finished seat sometime.
> Ross
I can post a picture of the finished seat. I don't think I am going to bother putting foam on the seat - I found it comfortable as is. I plan to spray the seat with automotive "rocker panel coating" to finish it (and hide my ugly patch-work fiberglassing).
My seat design is pretty basic and suits my paddling style. The mold could be easily modified to include thigh braces if desired.
Hope this helps.
Hank
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KBBS Archive 10,000 is maintained by Nick Schade - Guillemot Kayaks with WebBBS 5.12.
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