: There are quite a few Klepper kayaks for sale on the UK forums,
: some of which go back to the 70's. If my project doesn't work
: out I may well end up owning one myself.

If not that, then look for an Ally foldable canoe. The picture below is from their web page www.allycanoes.com/canoemodels.htm.
They make an aluminum-framed collapsible canoe. Thought you might want to browse their site for some ideas to incorporate in your construction.From this top-view you can easily see the placement of the middle and end thwarts, and how the seats are used as intermediate thwarts. You can also see how the bottom is composed of 5 stringers or chines, with the center one being the keel, or keelson, since it is inside the boat and not outside like a true keel. Forgive me if I use the terms interchangeably. It appears to be the same diameter as the rest of the floor stringers, which are bent to give the bottom its form and width.

There are some people who favor using stringers which are NOT bent like this, but which run parallel to the keel. Closest to the center of the boat you have floor stringers which are long, while near the middle of the boat you have shorter stringers. These shorter stringers start and end at ribs. I' not sure which design I like better, but most Ive seen are like on the Ally.

When you go to their webpage you can get a good look at the side view of their boats. You can plainly see that there is just one center chine in the sidewalls, between the floor chines and the gunwales. They list the sidewall height as 14 inches, so this means they have about 7 inches of fabric on either side of this support. The 5 chines in the floor divide it into 4 areas which are about 8" wide at the center, and taper to smaller widths towards the ends. That seems to be a pretty safe span of fabric support.

According to the catalog blurb, these boats have sliding seats, but I can't determine from these pictures how they mount them. It appears from the photos that the back tube of the seats is aligned over ribs #2 and #5. Counting from left to right you can (just barely) see the 7 ribs. The center rib is directly under the center thwart.

: That's no problem, I would love to own a traditionally made wooden
: canoe but they just aren't practical for me. I've just bought 4
: HDPE chopping boards earlier today so my ribs (or at least most
: of them) will be made from varnished wood.

Score one for forest products :)

: Belive me, I will be happy if it survives the first outing. One of
: the benefits when building your own gear is that you know how to
: repair it. Other than capsizing & sinking, I don't see how I
: could catastrophically damage it beyond repair.

If you want some ideas in this regard, wait for a few "war stories" from some of the others on this board. I think your biggest concern with a home designed boat is making the parts too small to support the weight you cram into it. There is a tendency to build the first boat too heavy for fear of this. Or, to build it too light because the idea was to have a very lightweight pack. Like Goldilocks who (in the home of the three bears) tried first one that was too big, then one which was too small, and finally found one that was just right--you may have to build three boats to get what you want. Welcome to the addiction of boatbuilding.

: Well I've been told I will be getting it at the price the supplier
: has paid for it. I don't know how long that will last so I'll be
: stocking up :p

See, now you are starting to talk like a boat-building addict. "Stocking up" is code for "I've got another boat project in mind"

: Thank you, I'll try and get a copy and look forward to reading it.
: I discovered this video (http://nfb.ca/film/Cesars_Bark_Canoe/)
: a short while ago (I have no idea how, It has just taken me the
: best part of an hour to find it again :s) It has no cometary
: other than some short captions that pop up every few minutes.
: I'm sure you'll enjoy it as much as I did. "César
: Newashish, a 67-year-old Attikamek of the Manawan Reserve north
: of Montreal, uses only birchbark, cedar splints, spruce roots
: and gum to build a canoe solely from the materials that the
: forest provides."

The North House Folk School in Minnesota www.northhouse.org has an annual class in birchbark canoe building. The first week is devoted to finding and preparing materials. The second week is spent building a boat, which is either sold or raffled off to one of the class members. If you want to spend a 2 week vacation in the US next year c'mon over. Check out their "earn and learn" program, where you get a credit of one day's tuition ($65 value) for each day you volunteer to help in a course. For example, you might work 5 days helping others build kayaks and then take a class on canoe construction. It would cut your vacation costs and allow you to spend more time in Minnesota. see the next post for a picture from their website.

: Thank you for the suggestions. I will take this on board when I try
: to incorporate the extra chines into the designs. I have also
: bee told I may want a layer of foam between the runners and the
: PVC skin to cushion any blow and help against abrasion. Have you
: found this to help or should I just add an extra layer of
: material to the area in contact with the keel and chines?

I have no personal experience with this. Nor have I seen it done in any skin-on-frame boat I've looked at. I would advise against a loose second skin rubbing against the primary skin on one side and the ribs and chines on the other. You would get grit between the layers and it would act like sandpaper. I would be in favor of building up glued-on patches of extra material in areas where wear is shown after a dozen outings, or sooner. Ally mentions that their floors are lined with a foam pad. If you go with foam, glue it in place, anticipate the extra weight, and take a look at the huge pack that Ally has for their boat!

http://webzoom.freewebs.com/allycanoes/Man%20&%20ally%20canoe%20backpack.jpg

If that doesn't scare ya. . .

PGJ