Sasquatch 14x30 ... Done , a 30 pound Ugley Canoe.

[JEM]

The core.... the wood... is the primary contributor to the strength and puncture resistance of the composite sandwich.

However, adding the fiberglass significantly increases the strength of the sandwich and also serves as a method to hold the panels together. Epoxy thickened with woodlfour alone is not enough.

 

[tx river rat]

Boy this is getting deep. We all learn a lot from these type conversations.
I have been staying up nights worrying about this :roll:
Dang here we go, first I have to say I think most everything said on this subject is right.
Chuck the wood is important , but can be built around any imperfections,Jack good wood is awesome to work with but not a necessary thing .
Every ply you add srengthens more than just the thickness of the ply
Here is my thoughts on the epoxy saturation, yes it helps much stronger,
Ok here is why to me , you have a plywood with three plyes in it which makes it stiffer, epoxy saturation adds another ply, to each side ,now you have a 5 ply piece, then you add another layer and then glass cloth now that is two more plyes to each side so you have a 9 layer ply or a composite, if you could slide the wood out of this composite it would still be strong. Fiberglass boats have no wood in the hull as we use it because they have a mold to hold the shape, they just shoot the resin and chopped glass in the mold let it dry pop it out a good serviceable tough boat
If I was building a boat and just painting it , nothing added to the structure for strength it sure wouldn't be 3mm ply it would be timber that was solid like Seedtic and Kieth use.
If I want a tough boat that is light I use ply and epoxie and glass cloth to build it (I really use polyester cloth and wood :lol: ) and it works. If I am using laun there is more care taken to make sure there are no voids ,with marine plywood I do the same inspection.Adding the soaking coat and the other layers you are not going to hear a cracking noise, unless you built the boat wrong and both woods will break.
My two cents
Ron
PS maybe I can sleep tonight now :wink:

 

[Paddlin'Gator]

Actually, to the extent that epoxy soaks in, it does increase the tensile strength in that part of the wood, although considerably less than the fiberglass/epoxy skins. In any composite structure the greatest stiffness is achieved by the plies farthest from the neutral axis having good tensile strength. That is why having an epoxy/fiberglass inner skin stiffens the hull so much, even though it isn't needed for abrasion resistance.

There is a very low viscosity epoxy available (Smith's Penetrating Epoxy) that penetrates quite well. Using something like that does add weight to the boat because of the amount that soaks in, so in most cases it really isn't necessary.

 

[Paddlin'Gator]

In this whole discussion there are two different "strength" issues. One is puncture resistance. The other is stiffness so the hull doesn't flex or "oil can" too much. The wood core and the epoxy/glass skins contribute to both. The greater the separation between the inner and outer skins, the greater the stiffness, even if the core is a material that adds little stiffness. Some very rigid composite structures are made using either honeycomb or structural foam cores in which the core material alone adds almost no stiffness. Great stiffness and light weight can be achieved this way with thick cores and thin skins. Unfortunately, puncture resistance is only as good as that of the skins, unlike in a wood epoxy/glass composite in which the wood contributes.

Since plywood or strips are our preferred core materials for the boats we are building, it comes down to a few trade-offs depending on what's important for the way the boat will be used. I guess it really comes down to what is "good enough".

 

[tx river rat]

Gator
You say it much better than me.
Ron

 

[oldsparkey]

I might be out of line on saying this but I'm pretty sure Paddlin'Gator would not so here I go.

He had a business (before retiring and selling it ) where he made stripper canoes for himself and some little sailboats for his customers.
You could and folks did , take one of his sail boats and go round the world on them , short boats only from 40 feet down , some might of been longer. :lol:

Chuck.

 

[Wannabe]

P Gator,
You are the only other person I've ever ran into that has heard of Smith's Penatrating Epoxy. Wonderful stuff.
Bob

 

[oldsparkey]

Matt....

I let this run for a while and then went back and cleaned it up , especially the battle between Jack and myself.... We are here for information not fighting , the battles can be out camping while sitting around a campfire , if he is not napping that much. :lol:

Besides everyone knows Jack is never right ( in the head , he is a plum bob off of diagonal most of the time , guess that is why we like him so much ) and sometimes I can almost be as good as Jack is on being wrong , I am trying to get as good at it as he is , if I can ever do that. :wink: :lol: :lol:

Final thought...
Our boats are made the way we/you want them , from the wood we/you want , kits or plans , epoxy or other items , it does not matter what we/you use to accomplish the process ...... it is the final step when we/you can paddle them and are really happy. To copy a hamburger advertisement which says it quite well .......
Have It Your Way .

Chuck.
PS... I have some of the Smith's Penetrating Epoxy here at the house for woodworking repairs on the place..... Thanks to Paddlin'Gator.

 

[Wannabe]

Smith's, the rot fixer upper.
Bob

 

[Paddlin'Gator]

I think I read in some of the Smith's literature that it was developed for architectural preservation projects to solidify rotted wood. I've never used it for that purpose, but it sure gets a good grip on almost any wood.

 

[Wannabe]

It's a top notch primer. Most any paint will stick to it.
Bob