Hi Tom, thanks for the reply.

: I looked over your drawings and have but a few comments.

: 1. Gunwale length will be determined at time of building on a
: strongback. On a 17' X 21" kayak, the curvature of the
: gunwale will add only 3" or so to the length.
: You mention bent , I assume you mean taking the curve and not
: actually machine bending the gunwales, which is not required.

: 2. Load is normally a function of displacement, not so much a
: factor of strength, which is not normally going to be an issue.
: My Sonnet double
: appears very light in structure, and has a quite flexible frame ,
: but easily holds over 500+ lbs on the water. A fully loaded ,
: flexible , lightweight SOF
: sitting in the water is not like a fully loaded SOF sitting on 2
: sawhorses... a common misconception regarding strength and
: buoyancy.

My only real worry is overloading the canoe. Everything is repairable/replaceable so long as it's not sat at the bottom of a lake. My only idea of what load the canoe could carry so far is by comparing its dimensions to other canoes. If strength isn't an issue, is displacement or recommended capacity simply a case of: volume of the hull up to the optimum Freeboard (in meters cubed) x the weight of water (in meters cubed) - the weight of the boat?

: 3. Use more chines on a wider taller boat like yours for frame
: rigidity. As drawn, your gap between keel and chine is too wide.
: resulting in a sluggish performing boat. Sponsons will act as
: chines, but I don't see their location in your drawings.

I think I will add two more stringers to the floor, probably with a smaller diameter of aluminum. These had been overlooked mainly because the boat I've based the plans on, the Nautiraid 390 (http://www.kayak-attitude.fr/media/catalog/product/cache/49/image/9df78eab33525d08d6e5fb8d27136e95/b/e/beach390.gif ) doesn't have them.

I plan to run 2 sponsons along each side just like the majority of your folder designs. I looked at the Nautiraid and Pakboat Puffin Saco (http://www.rei.com/product/785550) and they uses a very similar design. Would you suggest using 2 chamber sponsons like the pakboat ? or a larger 1 chamber sponson used by the Nautiraid canoe?

I have sourced the twist valves, PVC tubing and the Electrical PVC union connectors but the dimensions aren't clear. You call them 1/2" adapters and 5/8" vinyl hose, but the UK based site says (of the 1/2" adapters) "To Suit 1/2" (21.2mm) o.d. Pipework" (and of the 5/8" hose) "16mm (5/8”) I.D. and 21mm (25/32”) O.D." Is this correct?

Also, there are no dimensions for the twist valves, only that they are "replacement NRS Float Bag Valves". If I knew the O.D. of these I could always buy the rest accordingly.

: 4. Telescoping stringers are problematic vs simply using inserts as
: the farther you insert one tube into another, the
: greater the chance for them to "freeze up" whenever a
: burr or scratch gets on the tube... and it will. The gap between
: tubes
: will be very tight, and that makes them very susceptible to
: sticking together when telescoping. Pay close attention to the
: wall
: thickness of your tubing as that will determine whether or not thay
: will fit together properly for telescope , or inserts use.
: Also, know what grade aluminum you are buying as all tubing is not
: created equal.

That's something I've never considered. Do you think Emery paper could be used to make "in the field" repairs to a seized up length of pole? The compactness and portability of the canoe is really important. It will be carried on camping/hiking trips, maybe even between 2 people with all our camping gear.

My only concern, was that the different sections of pole may not flex evenly along the length of the canoe, although the ribs would force the curve and since the canoe is symmetrical it would be the same on both sides and thus not a problem.

I've spoken to the aluminum supplier who is a friend of my dad and he assures me they will telescope.

: 5. Look at the "Pakboat" site frame pics for more frame
: ideas. They are sponson oriented ( 3 per side) hybrids, but use
: multi-stringer floors.
: I prefer multi-chines vs multi-stringer floors, but either will
: suffice.

: 6. Consider making an inexpensive wood frame rendition
: "non-folder" of your design for testing with a plastic
: wrap skin. You can lash it together so
: that the materials can be reused when making mods to the design.
: Wood folders, on the other hand, requires much more complex
: hinges and connector
: hardware vs simply using an insert between aluminum tubes and snap
: on technology. As a homebuilt non-folder, wood is fine.

: 7. Folders share a lot in common with non folding SOF's, but are
: considerably more complex to design and build. Keeping it as
: simple as possible is the key to
: success in homebuilt folder construction.

: Have fun, Tom

Thanks Tom, this is all really helpful. In fact, I would be sat here £2200 worse off and I would have missed out on all of this had I not discovered Yostwerks. I feel really immersed in this project now and I can't wait to get out on the river in something I've made myself (and for 1/10 of the cost too!!)

Thanks again, Ben.