: the beam widths are going to be dependent on how high of a sidewall you have.

I understand that. Basically, I would like to keep the draft the same or not add too much more, since I would like to be able to get into shallow areas. I should have mentioned this in my original post. Just a rought calculation, I got approx. 22" for the beam width on the W1 and 26" on the W2 (the half forms were approx. 2" wider on the W2 as shown in Putz's book, which actually means the overall width of the forms for W2 were 4" wider, therefore, I assumed that the beam also increased by 4").

: Changing the beam on the Walrus might be a bit dicey. Putz apparently had a
: naval architect redraw the Skeene version of the 17 foot walrus, tweeking
: it to make the thing stable. After that, the 18.5 foot version seems to be
: just a simple enlargement of all the measurements by a fixed percentage.
: It got longer, as well as wider and higher. If you are going to increase
: the beam you might want to work with the numbers for the 18.5 foot boat
: and jusut decrease the spacing between the forms to reach the length you
: chose.

That was my thinking, although I was going to increase the beam to 30". I just needed to see how the increase in form width corresponded to increase in beam width which is why I asked for the beam widths of both.

: As for the "numbers" for these two boats. Putz expresses them in
: his book in what I consideer to be a rather awkward fashion. I've
: recalculated the directions he gives and posted the results at:
: http://www.geocities.com/eureka/business/7882/walrus18.htm for the 18.5
: foot boat and at
: http://www.geocities.com/eureka/business/7882/walrus17.htm for the 17
: foot boat.

Already downloaded that info. thanks.

: What I have are simple coordinates for each form which you can easily plot
: directly onto the plywood you are cutting your frames from. the angles and
: shapes of the forms are identical with Putz's , but I eliminated about 20
: inches of unnecessary height from the base of each form, so that you can
: save a sheet of plywood, and thus reduce the cost.

I agree, good work. Couldn't costs be reduced further, though, instead of making forms, making the actual floor frames and using them as the forms? My thougt was to cut the forms, as Putz says, then further cut them down to what is needed for the floor frames and screw temporary forms to elevate the boat and provide the form for the gunwales prior to tresseling. Then the temporaries are removed and the floor frames are left and the additional floor frames are added. I haven't worked it all out, yet, such as ensuring the temporary forms are still in alignment with the floor frames, etc., but I am trying to reduce waste and steps.

: I'm lousy at doing calculus in my head to solve these questions, so I use a
: quick and dirty approximation which relies on high school geometry. Here
: is how I guestimate displacement: First, I assume that the boat in
: question is flat bottomed and shaped like a long diamond. The length of
: the boat is the length of the diamond, and the beam is the width of the
: diamond. Second I assume that the designed displacement is based on a 4
: inch waterline, that is, with the designed weight loaded in, 4 inches of
: the boat will be submerged. Note, this is not the maximum load. As you add
: more weight to the boat it will sink deeper into the water. If the boat
: has high sides it can carry more weight, as it can sink deeper without
: water coming in over the sides. Maximum safe weight is when you have very
: little freeboard. Maximum displacement is the quantity of water it takes
: to fill the boat. You don't want to load most boats that much, but some
: designs ARE made with very small displacements so that the paddler can
: sink under the water and use the aerodynamic shape (that should probably
: be hydrodynamic shape) of the boat while submerged. Finally, i assume that
: water weighs aobut 60 pounds per cubic foot. If you do the calculations in
: the metric system you can calculte the displaement in liters and assume
: that each liter weighs 1 kilogram. In reality there are differences
: between fresh and saltwater.

I find your rough approximation to be pretty good.

: If we assume that a REAL boat has properties like this, then we can simply
: average the displacement, from 0 inches to 4 inches and come closer to the
: actual displacement. In this case, we have 0 displacement at 0 inches of
: depth, and 360 pounds of displacement at 4 inches. The average would be
: 180 pounds. Of course the shape of a kayak or canoe is not like a
: triangle, but is curved out, adding to the displacement, so you could
: guess that such a kayak would have a displacement of anywhere from 180 to
: 360 pounds at a depth of 4 inches. Depending on how you view the lines of
: the boat ( slim or full, rounded bottome or flatter bottom) you can pick a
: number closer to one extreme or the other.

Is 4" of draft typical? My maximum draft goal is 6" and I find anything 4" - 6"
acceptable.

: Now that you see how I approximate things, I'll let you calculate any other
: boat design yourself.

No problem, thank you for your excellent approximation, IMHO.

: You may find that some designs which have sufficient freeboard for rough
: water will not need much modification for use by a
: heavier-than-designed-for paddler when paddled in calm waters. Remember
: that in those cases where the deck is well sealed to the hull you won't
: get water into the boat until the water comes up to the height of the
: cockpit coaming -- which can be several inches above the sidewall.

The majority of my paddling will be in flatwater areas of small lakes and rivers and I do not expect much water to get onto the deck under those situations. However, for the occasional paddle in a large river or lake where waves could possibly break over the deck, I do want that security. Now that you mention it, and I left my book at home, I believe Putz mentions that the Walrus should really only be used on flat water. Does that mean I need to raise the gunwales if I intend on using it otherwise? Seeing as you have built at least one, I am hoping you would be the best to answer. See, I was really hoping to build two kayaks, one similar to a Folbot/Klepper style (the reason I am looking at the BK 10 to upsize to 13' x 30") for flatwater use, especially on small creeks and rivers where I don't believe a larger boat would be able to handle very well, and a larger boat (I'm leaning toward the Walrus for this) that I would use for larger flat water and some bay paddling. Perhaps I should reverse this, if the Walrus is designed primarily for flatwater?

: I do not suggest that you build an undersized boat, though. Technically you
: would be overloaded, and that is very unsafe. But, on the other hand, the
: original paddlers of these boats obviously ignored such matters. They were
: able to bring back heavy game on their fishing and hunting trips. Even so,
: we don't have any data though on how many went out and did not return
: because of an overload. They may have done this as a matter of survival.
: If you just want a nice quiet paddling experience, build the boat big
: enough to support you safely.

And that is exactly what I am trying to avoid, I don't want to build an undersized boat, but then, I don't believe that, for a recreational single kayak, anything longer than 15' is really needed. For more serious kayaker's, there is no limit, but I can't see trying to cartop, carry, etc. a kayak longer than 15'.

: Good luck on your project. Hope this helps.

: PGJ

It helps a lot.

I have tried using the Hulls program that is freely available, to model a kayak so that I could play with the dimensions, but I can't really get an accurrate model. Part of the problem is that I don't know how to enter the data by hand and the website that offers a Wizard for creating hulls either has a bug in its current version, it is more for larger boats and not really kayak design friendly, or I am inputting the wrong parameters. I was able to model the Wackie Lassie childrens canoe pretty well the first time out using the Wizard, but a kayak I have not had any success in modelling it. That is why I have requested assistance here.

Thanks,
Paul