Foam Composites

[Pierre]

Hello,

I've been haunting this forum (and B&B's website) for several years and have finally decided to build a boat. I will have the time and resources to complete this project this winter/early spring. I spent last spring renovating a small daysailer, which turned out very well, and gives me some optimism in my abilities to undertake a larger, boatbuilding project.

My question to the forum is:

Does anyone have any experience using foam composites with the CS/Belhaven designs?

I specifically want to use "Corecell", which I can buy in Toronto. I will gladly build with ply (if advised against using composites), however, the weight savings with Corecell, according to what I've found, would nearly cut the weight of the hull in half***. This weight savings would allow me to keep the boat on a dolly which I could launch by myself, instead of at a dock slip, which costs about $900/season (vs $200/season for dry docking). The added cost of the materials would pay for itself within a couple of seasons, through lower moorage fees.

Also, will the lighter weight affect performance negatively, in any manner?

Any insight would be greatly appreciated.

Pierre

*** http://www.westsystem.com/ss/assets/Uploads/06-Flatpanels.pdf

[Ray Frechette Jr]

Graham worked out some scantlings for me to look into  building a   CS17 out of foam core.

Figures Graham came up with would have the foam core weigh more than Marine Ply construction.

You save weight on the 9 mm ply, but 6 mm is lighter than foam core equivalent strength.

Also the material cost for foam core is much more than Marine Ply.

[kmrmike]

I built a Spindrift 11 with 5lb foam core, and the finished weight according to graham is about 20lbs heaver than a standard Spindrift. Mind you now my glass layups were of my own chosing(I think overkill on glass).And the cost was at least 2 times the wood price..But i'm glad I did it this way just for the experience. Iv'e had it for a couple years and enjoy it very much...Mike

[Pierre]

Thank you for the insights...

That's about what i suspected. The figures on the West System website (which I've linked to above) are extremely deceiving, as far as weight is concerned. Other research I've conducted stresses that the weight savings increases as the thickness of the core increases - Meaning a bigger boat will see a greater weight advantage in using foam.

According to the scantlings that Graham drew up for you, what are the approximate weights of the 1/4 inch and 3/8 inch foam composite panels (4x8) versus 1088 ply (Okoume)? 

[Ray Frechette Jr]

According to the scantlings that Graham drew up for you, what are the approximate weights of the 1/4 inch and 3/8 inch foam composite panels (4x8) versus 1088 ply (Okoume)? 

I don't remember.

What I do remember is that it is very expensive to make a foam core panel withthe same strength as 6 mm marine yet lighter.

Your not going to do it with e glass, and likely will be looking at extensive carbon to get teh same strengthand thickness at a lighter weight.

Marine ply also has further advantages of much better resistance to cyclical loading.

You can exceed woods failure strength for microseconds repeatedly with no loss of strength or change in qualities.

FRP on the other hand does not much care for cyclical shock loadings.

That is the thumbnail sketch,, for the detailed engineering, ask Graham as he has the details while I grasp the big picture....

[Hirilonde]

Your not going to do it with e glass, and likely will be looking at extensive carbon to get the same strengthand thickness at a lighter weight.

Mini 6.5s, Volvo 60s and some other box rule racing machines are made of carbon fiber/foam sandwich.  Incredibly strong, incredibly light and matched only by the fact that they are incredibly expensive.  Unless money is no object I can't understand why anyone would want to use other than plywood.

Here is some info on the only US Mini to enter the Transat.

[tom151]

Here is some info on the only US Mini to enter the Transat.

Not quite (ref minitransat650.com)... "1979 - Norton Smith from California, USA. Norton sailed to a first place finish on a [Tom] Wylie-designed prototype not sponsored by American Express. His boat was the first to have water ballast."

Another USA-designed (another Tom Wylie design) and USA built boat was accepted for the 1995 MT race but the USA skipper had to abort his transatlantic trip tip the start of the race.

[Hirilonde]

Sorry, meant in the last Transat which was 2007, the 2009 is going on now.  I believe there have been 5 since the beginning.