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  1. #1
    Join Date
    Apr 2001
    Posts
    1

    Question

    I am planning the construction of a wood-epoxy catamaran (Wharram) and I am a little confused with marine plywood. What is the difference (other than the obvious price one) between different type of plywoods that are all suppose to be marine grade? What is the difference between BS6566 and BS1088? What does the Lloyds certification mean for the average builder (me!)? If anyway I am going to fully cover the plywood with epoxy on the inside and epoxy with glass on the outside, couldn't I just use a domestic fir plywood at much, much better price? I obviously want to build a good solid boat that will last a long, long time but as much as feasible, I don't want to waste money on something that is not required.

    Any other constructive comments will be greatly appreciated!

  2. #2
    Join Date
    Mar 2001
    Posts
    399
    BS1088 is marine grade, BS 6566 is exterior grade. There are no knotholes or patches in either; both have void free cores and waterproof glue. Main difference is the quality of the faces. The BS6566 will have a few more appearance flaws, and in some sizes the faces may be thinner. Lloyd?s register certifies that the manufacturer has met the specifications for the standard.
    Okoume is an African mahogany, light in weight and color, and clear finishes quite nicely. Meranti is a Mahogany species that grows in Indonesia and the Philippians. It is about 20% heavier and is usually but not always darker than Okoume. We generally recommend Okoume for Kayaks and boats where weight, good bending characteristics and a varnish finish are desirable. Meranti would be more for boats that are painted, and harder denser plywood is required.
    Exterior fir usually has voids in the core, and sometimes in one face, so it will have weak spots, and also areas for water to collect if there is a break in the epoxy coating. Fir also doesn?t have as many plies as the mahogany?s.
    Fir also has a tendency to check on decks and areas exposed to sun, if epoxy coated, but not glassed.


 

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