Which foam

Hi,
I am a beginner in boat building. I am trying to built a 6m (19ft) rowing boat. The construction method I will use is foam sandwich. Somewhere I read that the best foam is Airex C70. However it's quite expensive.

But on the other hand I found some foams that are used for construction. They are called STYRODUR. So my question is, are this foams good for boat (hull) building?

What are the cons of using styrdur instead of more expensive foams? Are there any technical properties in which the styrodur is not so good as other more expensive foams?

Thank you for the answer

Kind regards

 

If it did the same job, the cheaper alternative would displace the dearer one from the market. There are issues such as the likely incompatibility of your Styrodur with the cheaper resins, which would negate whatever savings you made there, as well as physical strength properties that are not as attractive.

 

The foam must resist shear & delamination. As an example consider Polystyrene foam that is sometimes used for house insulation. It's friable & crumbles into small particles so if you tried to encapsulate it with epoxy resin & glass cloth, the bond between the sandwich of resin & foam would fail. Why not build using marine ply?

Jacques Mertens has a very useful website. http://bateau2.com/faq.php?panel=2

 

Aside from the peel strength and potential delamination mentioned, the foam used has to have an appropriate density. You'll want a minimum of 5 pound foam for basic structural elements, with heavier foams in some areas. We've all dreamed of using a cheap foam, but once the physical properties thing is looked at, we have no choice but to get the suitable stuff.