: I must have started these threads about lightweight boat construction. I now see it was a mistake. Consider the following history:

It was not a mistake. We all learn something from the discussion.

One question I don't think anyone can really answer which really should be answered before you make a design decision is:

How strong is strong enough?

I don't know what the maximum force you can expect a kayak to be subjected to. The answer to this question is again dependant on how the boat will be used. A boat used on flat water will see much lower forces than one that is used in surf. A boat used in big surf waves will see much different forces from one that is used in rock gardens. Before any engineering is done you really must determine what your damaging force will be.

I don't know the answer to this question and I don't really know how to figure it out other than building boats and doing what I want to do and see if the boat breaks. This is not too scientific, but until I figure out a better way it will have to do.

What I am interested in is skin (or panel) strength/stiffness. I feel if I can get the skin stiff enough, the whole hull will take care of itself (an unsupported supposition - just a gut feeling). As I have said else where I intend to test some strip-built panels. The tests I _want_ to do are impact tests. I do not have access to this sort of test equipment. All I can access at this point is a static 3-point bending test. It is not perfect but it will still provide useful data. It will provide some relative data for a certain type of load. From this you will be able to infer something about the impact strength, ie what is weaker in static will generally be weaker in impact and vis-versa. While this too is very unscientific, it is a step in the right direction. However, even the best test will still not answer the basic question of how strong the panel really NEEDS to be.

Short of destructive testing of finished boats any test or analysis method is going to be a compromise. If anyone has any suggestion on how I can improve my intended method to provide more realistic data, feel free to do so. Please remember, my budget is virtually zero.

If anyone has access to an impact test fixture please let me know.

• http://www.guillemot-kayaks.com/