: hi mick;
: would it be possible for you to sketch a profile view of this and post it? i
: can't quite get a visual from your description and it sounds really
: interesting!
: regards;
: daren.....

hi daren

its somewhat of a cumbersome process to post pics for me.(2separate computer systems at work).

and i'm just about off anyway but here's a word picture. not worth a thousand words but maybe 100 or so.

lets go up to marks yak and cut it across in 2 with a circular saw right thru where the hatch is. throw away the stern and cockpit cause we dont like it and lets look up close from about 6 inches away from the right hand side cut thru the deck and hatch. for the worst case lets say its a s*g built out of 1/8in ply, so the deck and hatch are 1/8in thick, lets say he depressed the flange by about one extra ply thickness so from the top of the deck to the top of the wood flange is 1/4in.

To define words, looking forward and starting from the sheer our eye comes up the deck/top (to the edge of the hatch cutout) down the deck/lip across the flange(say 3/4 inch wide)down the flange/lip and going back into the yak towards the sheer again we follow the under/flange. ON the hatch now, from the ctr top our eye comes across the hatch/top, down the hatch/lip,and under back up across the hatch/seat(the part that would touch the flange)and say our eye travels 1/2in further across the seat/perimeter.

So a basic before the start. the gasket is best on the hatch.(for many reasons but mainly this)We have a thin hatch of 1/8 in. the deck/lip is 1/4in.when straps are loose or whater, If the gasket is glued to the flange, the hatch has only to lift up 1/8 in to slip off. (thats if the hatch perfectly formed to the yak cross section, but usually something is lifting so even worse) if the gasket is a compressible gasket, and say compresses 1/16 in to be a flush hatch, the hatch is kept in place by only 1/16" over lap. not so good.

if the gasket is on the hatch side, even if compressible the overlap is 1/4in or the full depth of the deck/lip dimension. a safer situation if that matters.

so to start, a ring of scrap cardboard 1/2in deep around the under/flange so the flange lip is now 1/4+1/2= 3/4in deep. this lip should be vertical not slanted to the centre of the yak. mask/release the deck, d/l, flange, f/l, and the card.

on the hatch, on the inside of the 1/2 wide seat perimeter, glue another ring of scrap card 3/4 in deep. on the hatch/top glue(lowtemp hot or cheapass waterbased)scrap strips of wood poking out 1in or so or less. say 8pcs 2in long of typical strips. turn yak upside down and mush a pile of silicone on the seat and up the hatch card all around. clamp hatch in place clean up and let set for 2-3 days.

take apart. the deck and flange are unchanged. Attached to the hatch is an L shaped flange, the cross pc of which touches the flange and the long side slides up and down the flange lip for maybe even 1/2in.

If the card on the under flange had been set back say 1/16in or if the card had sloped outward a bit the gasket would be a very slight grabber.

some other thoughts:
some spacer might be desired to keep the gap exact all around.
my understanding is that silicone is deadly on finishes, if used don't smear, mask everything, don't touch the yak until set.
i don't know how thick the perimeter should be (probably way less is fine-thats what i'd do and then add to it(silicone) or back it up w/ a backing later) to mitigate against the gasket tucking under.

-mick