: I'm beginning construction of a skin on frame kayak following George Putz's
: book and I've got a few questions to those who might be able to answer.

: My back porch is layed out in such a way that getting an 18.5' kayak off it
: is going to be a *real* close call. 17' would be no problem. The volume of
: the 18.5 ft boat he gives is considerably greater than the 17. This is
: going to be used for a single paddler (myself), and possibly up to 50# of
: gear strategically stowed. I'm 6'6", 275 lbs. I'd like to build the
: 18.5' boat, even though the lines seem a little tubby, but space seems to
: be dictating 17'.

: Question is: will the 17' boat be adequate for my needs, capacity wise? I
: could shorten the 18.5' model, but that would result in an even tubbier
: kayak. Any suggestions? What about scaling up the 17' by 10% and
: shortening that to 17.5' or so?

: Comments? Suggestions? Advice?

: Thanks,
: Alex Wolfe

First, check out my previous post from a long time ago.

http://www.guillemot-kayaks.com/KBbbsOld/18318.shtml

It contains links to a couple of pages of graphing points that you can use to make the forms for the 2 Walrus designs shown in Putz's book. Putz has you draw yor forms with arcs and circles. I drew them on a computer and got the necessary data for simply graphing them.

The advantages of using these graphing points are many. The main one I was interested in was making forms that were shorter and did not use up so much plywood. Instead of using a sheet and a half of plywood for the building forms, with careful layout you can get them all from 1/2 sheet. That will save you about $20.

Putz enlarged the 17 foot boat to make the 18.5 foot model. It looks like he just multiplied the length, width and height by the same factor -- I think he used 10 percent. With the graphing numbers I have you can do the same rather easily, and choose any factor you wish. for a shorter boat try 5 percent. If you don't want to do the math in your head, get out a pocket calculator and and copy down a new set of graphing points. Or, on the same sheet of paper or plywood just graph the two forms for the 17 and the 18.5 foot boats and split the difference between the corresponding points. Then change the spacing between the frames so you get a boat that is 17'9".

Other possible adaptations of this design are possible. And simple. With your weight you will cause the boat to sink a bit lower than a lighter person. The design calls for the boat's waterline to be about 4 inches above the bottom of the hull with a load of about 175 pounds. with you the water line will be at a point about an inch higher. So, if you want to maintain the smae amount of freeboard ( the amount of your boat that is above the waves) you can keep the same basic specs for the 17 foot boat, but make the hull an inch taller than Putz specifies. I don't have the book in front of me, but I think his dimension "F" on his plans calls for a sidewall height of about 6 inches. Make it 7. Your boat will displace a bit more water, and you will sit at a slightly lower point, but that will actually increase your stability quite a lot, give you a bit more room for your feet and gear.

In case you haven't been following some of the discussions on this design, let me add some more. Putz covers his boat with cotton canvas and paint. The current "conventional wisdom" is to use a heavy weight dacron polyester fabrc which is sealed with polyurethane. The fabric is available from George Dyson in Bellingham Washington for about $2 a running foot, and the polyurethane is at most paint and hardware stores. You can get clear or opaque colors. The dacron won't support mold growth and is much more impact and scrape resistant than heavy cotton canvas or cotton duck. I've been suggesting painting the frame with epoxy resin to seal it, rather than coating it with spar varnish. I haven't tried using polyurethane on the frame, but that might work better than spar varnish, too. (Hmmm, a new experiment )

Check the archives for postings by Mike Hanks about his Plywood Walrus. Instead of cutting and installing all the little pieces of "trestling" that Putz uses to stiffen the frame, you can use panels of 3mm or 1/8th inch plywood (or even 1/4 inch if you wish) which are simply screwed to the long strips that make up the frame, and trimmed. The strips provide a surface that holds the screws used. Then just seal the seams with a strip of glass cloth and some epoxy or polyester resin, sand down the edges to make them smooth, and paint or varnish. If you want to wrap the boat in a piece of glass cloth and epoxy resin, you can, but it is not necessary. Mike has built several walruses and for this one he also wanted to raise the lines of the bow. He followed the numbers given in the article by Skeene that Putz includes at the end of his book.

The advantages to using plywood are the availability of materials and the ease of sealing the seams, as well as the increased structural strength. You also skip the part of installing all those little crossbrace pieces. Either way, you should be able to complete a boat like this for under $180, and in very few days. Perhaps you might wish to simply work outside for the time involved?

Hope this helps

Good luck with your building

PGJ