Monday, July 9, 2012

Building the Main Beams for my Gypsy catamaran

A catamaran has two identical hulls which are built separately. When the hulls are completed they have to be joined together. To do this two main beams have to be built. The plan calls for using "best quality hardwood" 2 inch by 3 inch to be used. For this special hardwood I was recommended a tropical hardwood BALAU HITAM . This species was recommended to me by a hasher friend and he had been kind enough to select a  matured  tree to saw the timber for me.

The wood is then planned so that the boding with epoxy is better. This is tough work with a hand planner.

The 2 by 3 are laminated with 9 mm ply on the outside and 6 mm ply on the inside.The width of the marine ply is 220 mm. There must be sufficient clamps to get the job done and in boat building there is never sufficient clamps!
Since I do not have sufficient clamps I build the beam in sections of 8 ft. The plywood are joined with a 200 mm ply.
I was hoping that I could save some time by building both the beams together.The first beam on the left came out as predicted with no surprises.

The plan calls for 4 inch screws to be screwed in place at 100 mm apart. I did not like the idea and I propose to use a stainless steel bolt to be bolted through the 2 by 3 s at lesser intervals. This was accepted by the designer Richard Woods.
Now, there is a "little" problem with the second beam on the right. Because of some warping in the timber it became almost impossible to place the other 2 by 3 timber on top.without tearing the plywood. Now, rebuilding the second beam will be another interesting story.

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