[Paddlewise] seat fabrication

I'll bet that almost anyone who's built a boat or two can do this for you. 
You can actually do it yourself if you have an hour or two. Different folks 
like different things to sit on. For me, the wedges and the foam pillows 
(such as "Happy Bottom") don't work at all well; they cause that 
circulation cutoff you're experiencing.  Many people feel perfectly 
comfortable using only a 1/2 inch simple foam pad on the bottom of their 
boat. But it's really easy to make a custom-molded seat which fits your own 
rear end, starting with a block of good quality closed-cell foam. I like to 
glue up a block about 16 inches by 16 inches, 4 inches thick, sit on it, 
mark out where my "sit down bones" were, and start carving.

However - I know that many excellent seats have been made starting with a 
12 X 12 inch piece of 3 inch thick foam, and that's much less trouble to do.

These seats are carved in a sort of ellipitc bowl configuration, leaving a 
**slight** ridge in the center. Especially for men, be very careful not to 
leave more than a very slight ridge; otherwise you run the risk of the 
"bicycle seat phenomenon" which can cause some permanent health problems. 
The sides of the bowl never get vertical, but maintain an outward-sloping 
angle from the center, so your hip bones are gripped securely but not 
painfully tight. The depth of the bowl is such that only about 1/4 to 1/2 
inch of the foam remains on the thinnest parts of the bottom when you're 
finished. If you go all the way through the foam, no worries - just glue a 
1/4 or 1/2 inch thickness of foam on the bottom and feather the edges of 
that on the underside of the seat.

The reason for starting out with a 16 X 16 inch piece of foam is that it 
gives you the opportunity to maintain a 1 or 1 1/2 inch lip of foam around 
the edges of the completed seat, and to extend the seat forward a slight 
bit if you want to - but be careful not to leave a lip of foam at the front 
edge of the seat, which could push up into your thighs, of course.

Do this carving outside. You'll be amazed at the volume of tiny bits of 
foam "sandings" you generate, and you'll be very frustrated at how 
difficult it is to clean them all up if you do it inside. The foam sandings 
mixed with Cabosil or Microlite or silica microballoons make a good light 
thickener for end-pours and so forth.

The block should be secured to something else, like a piece of scrap wood 
which you can kneel on, because if it's unsecured it will tend to fly or 
spin all over the place as you carve. Use several small bits of hotmelt 
glue to secure the foam block, then just cut off or melt the little blobs 
of hotmelt when you're done. Carving can be done with several different 
things; the easiest, I think, is a heavy gauge disc of wire brush, attached 
to a variable speed rotary drill or a small handheld grinder, used very 
lightly and very carefully. A broken-off piece of Sureform plane works. The 
serrated edge of a diving knife works. And so on. "sharkskin" or a 40 grit 
emery paper is nice when you're all finished carving, to give a relatively 
smooth edge.

If you like esthetics more than usefulness you can cover your seat in 
stretchy black cloth like the cloth which is sold for loudspeaker covers - 
but I prefer to leave the seat just "as is".

The finished seat can be secured in your boat with Velcro (try to get the 
marine version), or contact cement. I like to use Velcro until I'm certain 
just where I want the seat to be.

Bill Hansen
Ithaca NY


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