Hi Hank, I like it!

Thanks for the post and the photo. I've been trying to visualize how I will build my seat form, and your post helps a lot. I think I'll do the same thing, but make the sides taller to make built-in "cheekplates" to mount hip pads and hang the seat with.

Did you make your seat directly off the mold, or did you make a mold off that mold so that your hand-finished surface would be on the bottom of the finished seat?

Thanks, Shawn

> There have been a couple of posts to do with custom formed kayak seats so
> I thought I would share my experiences...

> I am just in the process of making my first fiberglass seat from a mold
> that constructed from some wood and some mortar. It took about 3 hours to
> make the mold (not considering setting times) and about 2 hours forming
> the seat.

> The mold is made from about 8 feet of wood (24" scraps of spruce 2x6
> & 2x8) 3/4 of a bag of premixed mortar and covered with scraps of 6 oz
> fiberglass - under $10.00 of materials.

> I made the frame from 3 pieces of 2x6 and 1 piece of 2x8 for the back. The
> width of the frame was set by width of the cockpit so the back rest and
> front of the seat were cut to size. The length of the seat was determined
> by sitting against the backrest and moving the front piece until I got the
> support I wanted under my legs. The front is angled back slightly and, in
> hind sight, I should of angled the other pieces as well. The sides are
> shaped to be narrower at the top. The "armrests", back and the
> four corners are radiused to blend together and make for easier glassing.
> A piece of masonite was added for a bottom.

> The inside shape is formed of mortar that was mixed to a VERY stiff
> consistency and packed around the inside of the frame. I covered the frame
> with a plastic bag and sat in the mortar to form the seat. It took a
> couple of adjustments to get all the bumps and hollows in the right places
> and to smooth the thing over a bit. If you try to work the mortar too much
> it will start to "float" the water to the surface and the mortar
> will sag. Once I was happy with the basic form I put the mold aside to
> partially cure. After about 3 hours the mortar had cured firm enough that
> I could use a stiff bristle brush to sculpt the seat. It only took a
> couple of minutes to remove the extra mortar to make room for padding and
> to blend the contours nicely.

> After the mold had set/dried for a week, I applied a layer of fiberglass
> and a coat of resin to give a smooth finish. A light sanding is required
> to remove the gloss from the resin to allow the mold release to adhere
> better. I mounted the mold on a "lazy susan" so that I can
> rotate it conveniently while glassing - it is quite heavy.

> I applied two coats of a mold release that I cooked up from a mixture of
> bar soap, water and vegetable oil. The mold release is applied like old
> fashioned shaving cream - a foam whipped up with a soft damp brush. When
> the foam had dried to a hard waxy surface I covered the mold with one
> layer of 6 oz cloth. The next morning I popped the casting off of the mold
> and did a rough fitting to the kayak. I then put the casting back on the
> mold and build up the high stress areas (corners, armrests and front of
> the seat) with some scraps of glass before adding 2 more layers of glass
> all over.

> The seat is very light in weight. The side panels are a bit thin but the
> main support is in the reinforced corners and the base - it is actually
> solid to sit in and does not flex at all.

> I had intended to add some pieces of rigid foam or strips of luan inside
> the seat as stiffeners but the whole thing seems strong enough as is. I
> will have to use the seat a couple of times to see if additional
> reinforcing is required.

> This is my first attempt at butt molded seats. I use my kayaks for fishing
> and flat water touring so I don't need the "press-fit" style of
> cockpit/seat the is required for playing in the ocean surf. I got to use
> the seat for a couple of hours on Sunday :-) and I am quite pleased with
> it - very comfortable, even without any foam covering.

> Hope this is of help. As always, comments and suggestions are welcome.

> Hank

> Here is a picture of the mold:

> http://ross.secant.com/kayak/bbsposts/hanksseat.jpg