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Bertram31.com General Bulletin Board
Re: B31
Posted By: Capt Patrick McCrary In Response To: B31 (Tony)
Date: Tuesday, 14 December 2004, at 6:33 a.m.
Tony,
All of the hulls are the same in general proportions, but do have some differences between model years.
The early to later '60s models have a distinctively different lift strake pattern as the strakes come up the bow. The first 3 strakes, (counting from closest to the chine), sweep up and merge with the chine at the bow. The 4th, (deepest), sweeps up, but merges with the bow about 14" below where the chine merges with the bow.
Somewhere around the early '70s the strake pattern was changed, run a bit straighter at the bow, and only the 1st & 2nd strake merge with the chine. The 3rd & 4th tapper out and end without merging with the bow.
Early '60s models have the heaviest glass content, especially in the hull. By the mid '60s the layup schedules began to be reduced and the hulls were slightly thinner. In '67, when Richard Bertram sold out to Whitaker, the bean counters began influencing the labor and material costs, further thinning down the thickness.
In '73 the big oil crisis struck and polyester resin, (being a petrochemical product), prices shot through the overhead. Every fiberglass boat builder was scrambling to make ends meet. Layup schedules were further reduced & even lesser quality resins may have been used or blended into the premium resins to stretch the buck.
The distinctive green color of the resins Bertram used are NOT an indicator of quality, but rather a dye used to aid the fiberglass crew in detecting air bubbles as the layup progresses. Air in a clear or very light colored resin is harder to see than in a darker resin. The dye was also very likely added to the catalyst, (MEKP), rather than the resin, to aid also in the mixing stage.
After the crisis was over and prices settled back down, only the premium resins were being used again & the layup schedules were increased, but not back to pre-crisis status. From this point forward the layup schedules remained pretty much constant.
In my opinion the most desirable hulls are '61 - '67, followed by '68 - '72, in a progressive manner. After that all of the hulls remained pretty much alike & the progression reverses to be '86 - '74, (newer being better is the only rationale here). '73 remains the single model year that has the least amount of glass and the potential for the most glass related problems, such as blisters and mild to moderate delaminations.
A note back to the green colored resin: As a by-product, the green resin allows a surveyor to quickly spot washed out surface fiberglass, (where the resin content has eroded away, leaving nearly dry fibers exposed), & to easily detect any structural repairs that have been made by other than Bertram...
Best regards,
Patrick
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