: Bryan, Please do this for all of us and "end the Madness!" Make
: some test panels, use two layers of woven smooth 3oz glass on 3mm ply. One
: layer on each side. Make another panel with 6oz glass on either side.
: Break them. Which one's lighter ? which one's stronger? ok, ok, ok, well
: then how about two layers of woven smooth 3oz on either side of the 3mm,
: which one's lighter? which one's stronger? hmmmmm

It's already been done. If you want a reference look at the table on page 6 of Kayakcraft. It's not exactly what you've asked for, since it compares 6 oz. vs. double 4 oz. standard weave glass, but the numbers are convincing. Look at the data for 1/4 in strips with 1 layer of 6 oz. glass vs. 3/16" strips with 2 layers of 4 oz. glass. The latter is 10% lighter AND 40% stronger. Notice also that it flexes 68% more before failing. What this means is that you CAN have lighter weight, increased strength and increased durability at the same time. Using 3.2 oz. satin glass in place of 4 oz. woven glass would reduce the weight even further, without substantially reducing the strength advantage, based on the numbers I've seen on glass supplier's web sites.

: Ok how about this, a kayak with "just enough resin to wetout and seal to
: .01" " on the interior. Put a gallon of water in it for a month.
: Now get a kayak built with an excess of resin (structurally speaking) and
: leave a gallon in it for a month. Which one is likely to have some water
: damage?

Neither one. If the wood is sealed, it's sealed. If you're concerned, putting extra resin OVER the glass will seal it better against abrasion and will not compromise the strength of the layup, though it does add weight. The problem is excess resin WITHIN the layup (between the wood and glass), which weakens the structure.

: This is one of the things that can happen with boats that are used
: and one of the reasons for going beyond theoreticals.

What "theoreticals"? We're talking about established principles and hard data. Just because you or I didn't know about it until now doesn't make it "theoretical".

: What I'm getting at is lighter is not stronger, they are two different
: things.

Different? Yes, but not mutually exclusive.

: But good building practices can make something stronger per unit
: of material,

True.

: and that is different from lighter and stronger.

Not necessarily. You have choices. You can increase strength for the same weight. You can reduce the weight somewhat and still realize a net strength gain. Going further, you could reduce the weight more for the same strength. It's a trade-off.

: Just to be
: cantankerous about the whole issue there's no way that a 30lb strip built
: kayak is going to be stronger than a 45 lb kayak built of the same
: materials, make the boat and test it.

Why not? The table I referred you to says otherwise. Perhaps those exact numbers are not achievable, but can you say with absolute certainty that it's not possible to build a 30 pound boat that's stronger than a 40 pound boat? The numbers are arbitrary, but the point is that stronger AND lighter boats are achievable using the same basic materials; wood, fiberglass and epoxy.

: All I can tell you in my experience
: is that when lightness is the goal then strength and durability are
: compromised. That's true whether the forces are between a well built Honda
: and a chevy suburban or kit kayak and a boutique ultralight. We all live
: in the same reality.

Then you're ignoring that "reality". For example, as a avid cyclist, I've seen the advances in materials and construction techniques that have made my equipment much lighter, stronger and more durable. Twenty years ago, my racing bikes weighed ~20 pounds. To get substantially lighter required using fragile components or drilling/milling so much material from them that their strength was compromised. Today, I'm riding a sub-16 pound bike that's more rugged than anything I had back then. The frame is stiffer and impervious to the elements. Every functional aspect is superior as well.

Materials science doesn't stand still. New materials, and new and better ways to utilize existing materials, are discovered all the time. The only downside is that often new materials and methods are more expensive. In the case of wood/glass boats, the difference in cost to produce lighter, stronger layups is relatively small, especially since we're not paying anyone for the increased labor involved.

Let me state for the record that I think the safety issue is a red herring. While it's certainly possible that safety could be compromised in some situations, it's obviously not a huge problem.

I see this debate as the difference between "adequate" and "optimum". Boats constructed to either standard will get the job done. Either one can be as just as gorgeous and paddle just as well as the other. The optimally constructed boat can be expected to be lighter, stronger and/or more durable in a ratio that can be adjusted by the builder's choice of materials and construction techniques. Personally, I would never say that the most commonly used construction methods are inadequate, merely that it's possible to do better and that there may be some real benefits from doing so.