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Re: not that much less
By:Rob Cochrane
Date: 10/21/1998, 7:48 am

> Considering just stiffness and strength in bending, the optimum is 50%
> cloth/epoxy and 50% wood by weight.

What wood? Green Heart/Lignum Vitae /Sitka spruce/ Ceder/ Kiaat!!

> The ratio of cloth outside/inside should be 4/3.


> Considering puncture resistance the exterior cloth/epoxy thickness should
> be .017" min.

To stop what? Is this Kevlar?

> Considering construction requirements .100" wood is about the min I
> can handle.

All the work I have done and that of some friends who build Formula One Cars for a living and achieve torsional stiffnesses of 10,000KG /meter/deg with less than 1mm skin thickness but 12 to 18mm core. (Nomex and Aluminium)

> This assumes that the cloth/epoxy ratio is near optimum (50/50 for plain
> glass or 60/40 for satin by weight).

Optimum glass/ Epoxy can not be achieved without bagging!!!!!!!! No one is able to bleed off the surplace.

If the weave is filled without a peel ply or a bleeder foil then the ratio will always be higher epoxy to glass

> As I recall:

> 9oz plain / .187" strips / 12oz plain is near 50% wood.

> 12oz cloth lays up about .020" thick.

> This is about the same weight as

> 6oz plain / .250" strips / 6oz plain

At the end of the day George we are building WOODen Kayaks out of wood and if we are to build composite kayaks then why not use Nomex or foam or Aluminium honeycomb as the core material.

Perhaps we should use end grain Balsa??

I like wooden boats and I build them for a living if I wanted a plastic boat I have the skills to build a boat that would come way under your "wood" boat weight. The only problem the tooling alone would cost $100,000 and the autoclave even more! So what the cost of the Kayak?

By the way it seems all boats must be the same weight irrespective of length, beam wetted surface etc.


Messages In This Thread

Re: not that much less
Rob Cochrane -- 10/21/1998, 7:48 am