Subject: Re: masts
From: Mike Crawford
Date: 11/7/2006, 5:25 PM
To: rob dalton

  I'm not yet sure whether or not my next boat will be a harryproa, but regardless of what I build, I'll probably ask Rob to do the masts.  That's one area where I'd rather not worry about whether or not my inexperience has resulted in a spar with some unfortunate voids.  I trust myself to do a lot of work, but not all of it.

  That bamboo sounds wonderful.  As you find out more, please let me know about different mat weights, strengths, weaves, and prices (as little or as much info as becomes available).  I'd still probably glass the bottom of the boat for the abrasion reasons you mention, but it's neat to see the work being done with natural materials. 

  Coincidentally, my wife and I are going to build a house next summer, and all the flooring will be bamboo.  It's cheap, strong, harder than oak or maple, renewable, and good looking.  What's not to like?  I never even thought about weaving the fibers into a mat.  That's brilliant.

  Thanks for the bamboo information.

       - Mike

rob dalton wrote:
I think your research was well appreciated by all who are serious about building. I worked out the weight of building a mast out of bamboo strands, the stuff used in bamboo flooring and it came to about 2-3 times the weight of a carbon mast. I am more than happy to have an engineered carbon design as it would not be that much more expensive and if I have the spare money would look at getting Harryproa to make them as they have the process well on the way to being sorted. The big difficulty for me in the design was trying to work out the amount of material to use for the off axis loads to prevent buckling.
 I have been talking to some suppliers of bamboo products and there is considerable research being done on using bamboo to replace fibreglass in reinforcing of polymers. This includes many car manufacturers for their plastic panels. It has greater strength to weight is stiffer and is easier on machining and cutting equipment.
 It could be very effective in decks and inside cabins but glass wins for abrasion resistance on the hulls. The techniques are to use urethane resins to bond to the cores and if done properly need no further finishing. The individual cellulose fibres are already in their own lignin matrix and what is bonded is continual strands woven into a mat. I don't know how competitive the prices are but less than S glass for a stronger material.  I have been promised some samples to play with.
I am still working whether these materials are  suitable materials for the beams. May be the best it is carbon with Kiri providing extra stiffening of the wall with possibly double bias bamboo on the inside.
 One of the problems with the use of the natural materials is getting consistent characteristics

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