A belated report on completing a first skin-on-frame, a slightly modified Yost Sea Rider (after help from this forum: http://kayakforum.com/cgi-bin/Building/index.cgi/md/read/id/218307/sbj/seeking-advice-on-choosing-a-kayak-design/). I launched the boat in August 2013. The building experience was a challenge for me as I had to learn everything at every step but building a sof, like carving a paddle, is very forgiving. Despite the "esthetically-challenged" look of the boat and of the finish overall, which betray my inexperience, I am extremely satisfied with the result.

The aim was a boat with the maneuverability and speed of my Current Design Slipstream but narrower, with more secondary stability for paddling in waves, and which would still accomodate my rather stiff 5'8" frame. My earlier woodworking experience was limited to carving greenland paddles.

Materials are WRC and 12 mm (1/2") marine-grade plywood, West System epoxy, artificial sinew, tung oil; 1/4" oak floor with aluminum angles; 8 on. polyester skin from G. Dyson and two-part polyurethane from Spirit Line. A few notes:
- I did not epoxy the plywood sections; instead I applied tung oil to the whole frame (4 coats).
- I did epoxy the connections between the stringers and sections, and then I lashed them using artificial sinew. I am still perplexed about the sinew, as it tended to break easily when pulling it tight: I don't doubt its strength when wrapped 6 or 8 times, but I would hesitate to use it without gluing first as I doubt I could get it tight enough.

I modified the Sea Rider design in two minor ways. First I increased the space for my knees by making section 4 higher by 1/2", and by making it thinner (3/4" instead of 1"); I compensated by doubling section 4 and "tripling" the upper portion of it (towards the back to clear my kneecaps), which made it into a masik of sorts:

I also made section 3 higher by 1/2" to keep proportion (I should have made the deck stringers longer, obviously!). The result is comfortable for me; surprisingly I could have gotten away with a slightly lower section 4 but my size-9 feet need all the extra space they get.
I also made section 5 thinner to make the hole larger for carrying supplies, and doubled it for strength.

The second modification was to make the ends higher, which was suggested to me by an experienced builder, to avoid the boat plunging into waves. For this I simply glued sections of WRC on top of the gunwales. These were 37" long in the front, 32" in the back, adding 3/4" height at the tips:

In order to define the shape of the bow and stern I looked at the proportions of various boats in photos on the web as well as in Heath and Artima's Eastern Arctic Kayaks. My boat is 17'3" and the slope starts at about 23" from the front and 20" from the back.

I paddled the boat extensively during two weeks late August 2013 at Le Bic national park on the lower St.Lawrence. These are sea conditions (salt water, 3-4 meter tides, 5-10 degree celsius water) and the estuary is 40 km wide at this point. On a couple of days waves were at least one meter (they easily hid the horizon from my sight); waves in this area tend to be choppy.

On calmer water the boat handles much like the Slipstream: even though it is barely 20" (vs. 22" for the Slipstream) its primary stability is similar, it is maneuverable and reacts well to leaning (but turns more easily without leaning because of its rocker); its speed seem to be much the same although with more effort it seemed to be faster. It does have a tendency to broach but I did not miss the skeg too much. The big difference though is in waves: the modified Sea Rider feels incredibly stable and secure in hind quarter waves whereas the Slipstream feels quite shaky. This is probably due to the higher volume in the ends:

This is discussed in technical terms on the One Ocean Kayak site: http://www.oneoceankayaks.com/kayakpick.htm. On the other hand with side waves the Sea Rider will sometimes shift from one side to the other, probably because of the hard chines, but this is subtle and not a problem.

This winter I will finish the outfitting (back band, deck lines) and a custom tuilik.

I wish to thank all who responded to my earlier post and of course Tom Yost, Jeff Horton and many others for sharing all those fantastic resources on the Web (I also found Jeff Horton's More Fuselage Frame Boats quite useful). You have made this possible.