Hello Rob & group,

 

There has been a lot of good discussion lately in the group on different construction methods Plywood , Al, Foam core ect.  I would strongly recomend if you can to get the book "One-Off Airex Fibreglass Sandwich Construction" by Thomas J. Johansson, Published in 1973.  The book is available thou Amazon.com but I think the only copies are used since the book is out of print now.  It talks a lot about design principals of using foam core and comparisons to other types of construction.  It highlights the benefits of foam sandwich construction and gives many useful details of foam sandwich construction.

 

Note that when the book was printed Airex only had one type of foam and it is more pliable and less brittle than most of the foams used today.  It is what Airex sells now as type R63, "Damage Tolerant foam".  This is the type foam that is what Derek Kelsall is using for what he calls "pressure shaping" or simply cold forming of the foam.

 

 
http://www.alcankapa.com/alcan/acsites.nsf/pages_accm3_en/index.htm!Open&lang=en&p=prod_foam_r63&m=4&f=index&type=.htm

 

 

Another link to a builder who used this foam :

Note how it is easily bent around a catamaran hull.

 

The book has convinced me that this is one of the best foams you could use as it can be bent easily and has great impact characteristics.

 

One problem I have come across is that it is harder to find a source for it.  It can be ordered but you have to purchase a pallet load of 20 sheets.  I am planing to build some replacement float hulls for my TT720 with it but I will have much more than I need.  Rob will I be able to use leftover 1/2"  for 40' Harryproa.?  What thickness do you expect will be needed ? 

 

Happy sailing,

George Kuck

Chestertown, MD

PS; I was able to get a free sample kit with many diferent typed of foam core from Alcan Corp.

 

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