Wooden Boat magazine for this month (June/July? 1998) has an article on canoe builders which covers their method for filling the weave on cotton duck, and gives some formula for their base coat. Their approach seemed to be similar to that proposed by George Putz in his book on canvas covered craft. Both use an oil based paint that is significantly modified with filler materials and added driers. Putz uses ground chalk and the WBM article mentions silica (finely ground sand) for fillers.

Of the two processes, I think the method described in WBM is stiffer. It might be great for canoes, which have a lot of wood behind the fabric, but I think it would crack on a kayak, which tends to have more flexible fabric.

My copy of ClarkCraft's parts catalog lists canvas for covering boats, and by that listing is a note to call them about the availability of canvas fillers. That is what they call their base coats. They used to have a contact, rather than a supplier and would give out the name and address. Might be worth a phone call. Their phone number is on their website: www.clarkcraft.com

Personally, I've been playing with coating the fabric with an elastomeric roofing compound. (Various brands are called SnowCote, or SnowWhite, or SnowRoof, or soemthing like that) It builds up thick, so I should not need to add any filler, and it stays very flexible. I've held off finishing this because I got sidetracked looking into neoprene and hypalon coverings instead, so I can't tell you how it works.

However, someone who used this material for a hull for a folder described their results a week or two ago. Mark may not have tried this, but I'll bet he can find he link. Best of luck with this. Please keep us informed of your progress, and any suppliers you find. Paul Jacobson