There are times you want to shoot for specific numerical design goals. The first step in this process is determining what those numbers are. How do you do this? You probably try out a variety of boats, choose one you like the best and see what it's numbers are. How do you determine the performance numbers of a given design? If you have a collection of back-issues of Sea Kayaker you may be able to find some of the numbers you need. Or you can measure some critical dimensions on the design you like and replicate them. Look at the overall shape and try to reproduce it.

Software does not guarrantee you acheive the numbers you are looking for. All the software can do is tell you what the numbers are, then you need to decide if they match what you want. If they don't, it is up to you to decide how you are going to change the dimensions to make the desired "improvement" in the numbers. Again the software lets you check whether you got what you wanted.

This all assumes you really understand what the numbers mean with respect to how the boat feels in the water. You can do a lot of research into what the numbers mean, but it probably won't really sink in until you have a couple designs under your belt.

You can incorporate the standard design "rules" as easily on a full-sized real boat as with a virtual computer design and when you are done with the design you will have a boat you can go paddle and test to see if your ideas were really correct. You can design a boat with all the "right" numbers and after going through the effort of trying to reproduce that design in wood and canvas you may find it is no good.

Skin on frame construction is well suited to this design method, and to my mind this design method is part of the skin-on-frame experience (even though I have not yet done it myself). I think you would be missing out on part of the fun if you drew up some precise plans and tried to slavishly follow the plans. Wood has a mind of its own and without a rigid form it will follow it's own path, why fight the wood to reproduce a computer model when you can probably do just as well with a seat-of-the-pants design. You are not designing an Olympic racer.

I know some designers have created strip-built and stitch-and-glue designs using this method and the boats have turned out very well even if it took several iterations to tweak it into the boat they really wanted. There is a lot more invested in a S&G or S-B so if your first boat is a failure it is more of a problem. If your first S-on-F boat is not quite right, rip the skin off and rearrange the frame and you can make a lot of changes. A couple new ribs and a new thwart or two and you will have a completely different boat.

Don't get me wrong from all this, I am a big believer of using software as a design tool. For strip-built boats, the software will spit out perfectly spaced forms at the press of a button. I can draw up a design quickly and get it all fair digitally before cutting any wood. Since the shape of the boat is dependant on the forms, this works well. The shape of a S&G boat depends on the panel shape. Software can develop the panels so the designer can get the shape he/she wants without wasting much occume. The design analysis provided by the software is secondary (but worthwhile) advantage.

If you are looking to build a boat with a specific set of performance parameters, don't build a skin-on-frame. Strip-built is probably the most faithful to the intended design.

> hello nick (& the rest),

> I read your response here & I'm surprised !

> I respect your opinion. I believe you know about kayak building/ designing
> much more than I do, but something here isn't clear to me.

> just like you said, the construction method in discussion works very well
> with the design method you described, & that's probably the way the
> inuits & aleuts did it.

> but aren't we trying to create a kayak with certain behavior
> charachteristics ? a certain amout of initial/secondary stability ? a
> certain amount of bow/stern floation ? prismatic coefficient ? etc'.
> aren't we looking for a design method that will give us a better
> prediction of the behavior of the future kayak, than the prediction we get
> with the inuit/aleut method ?

> my theory says: make a kayak that will give you the behavior/responses
> you're looking for. not the look. worry about the look when you buy a car.

> what will he do if he puts his new kayak on the water for the first time,
> paddle it for 20 minutes & say: "this thing sucks ! my plastic is
> much better ! " or should I ask, how can he refrain from getting into
> such situation ?

> am I the only one ?

> is my theory wrong ? (no, I don't intend to change it)

> erez