By Jack Brennan
Shanachie, 1974 Bristol 30
Bristols have a reputation as tough, seaworthy sailboats with thick, well-built fiberglass hulls.
So imagine the surprise of many Bristol owners when they learned, decades after Bristol stopped manufacturing sailboats, that many of the hulls were manufactured in two pieces and bonded together instead of being made as a single unit.
The revelation came about after a poster on cruisersforum.com tried to criticize Bristol 32s and suggested they were not seaworthy because the hulls were formed in two pieces and then bonded together with polyester resin and fiberglass.
A number of other posters jumped to the 32’s defense, pointing out that the sailboat has made impressive voyages, including a well-known Atlantic Circle and an ongoing circumnavigation, since it started production in 1966.
But it turned out that the original poster was correct about the manufacturing process, even though he was wrong about the 32.
During an online discussion on the Bristol email list on Yahoo, Eric Berger, owner of the Bristol 32 Delta-T, volunteered to contact Clinton Pearson. Pearson founded Bristol Yachts after leaving the sailboat firm that bore his name.
Pearson’s reply surprised many Bristol owners on the list. Building sailboat hulls in two pieces allowed for a better hull-deck joint, he said, without compromising the strength of the hulls.
My explanation of the hull/deck connection was to explain why we made the improvement for a better sheer joint. All Bristol Yachts from the 27 to the 45.5 were molded in two half molds lying horizontal on the shop floor. After all the hull sides glass laminate was gelled, we rolled the halfs up together and glassed the center line together, similar to the view that you sent to me.
“Additionally, after the lead keel was placed in the bottom, a strong layer was glassed over the lead to a 12-inch lap on both sides of the hull. Then a plywood sub floor was fitted in place and glassed to the hull, then the forward peak bulkhead and the aft lazzarette bulkheads were glassed in. The main interior bulkheads provided additional binders.
“Many of our boats have sailed in the oceans of the world. Our crews have delivered boats to Europe. I have never heard a report of structural problems. During Hurricane Bob, many boats were lost in our area. When our staff and I walked the beaches of Massachusetts, RI, and Block Island looking for damaged boats to repair, we never saw one with the center line split. We repaired over 20 boats with damage from rocks and beaches, but not from any building problems.
“Our larger boats, the 51, 54 and 72, were not built in halfs because of building space limitations with not enough width to open them horizontally. The hulls were split along the cove stripe to continue to provide our thoughts on a strong fair sheer.
If this is not clear, please let me know of any questions.
The concern is that boats back then were mostly built with polyester resin. Having all of the polyester resin cure at the same time creates a chemical bond, which is regarded as the strongest method of creating fiberglass.
If a hull is made in two halves, they would be joined by .applying wide layers of mat and roving soaked in polyester resin, which would create a mechanical bond.
Depending on how far along the resin was toward fully curing, there might be some chemical bonding to supplement the mechanical bond, which can be very strong, but not as strong as a chemical bond.
But it turns out that many highly regarded sailboats, including Ericsons, Pearsons, Shannons, Contessas and others, were built this way. John Kretschmer, the well-known sailing writer and adventurer, addressed this in a review of the Ericson 35 II for Sailing magazine.
“:Although many boats were built this way, especially overseas, it comes as a surprise to some sailors who instinctively think a one-piece hull is stronger. The 35 II’s hulls were joined with 11 laminates of mat and roving, and I have never heard of a problem with a centerline hull joint.”
The key was the professionalism and skill of the builder, and Pearson’s vast experience in manufacturing fiberglass sailboats ensured it was done correctly with Bristols.
Some Bristol owners, however, already knew about the manufacturing process. Mike Orsatti, owner of the Bristol 38.8 Spirit, took photos when his old Bristol 29.9 was being built.
“Click on the following link to see a video of pictures taken at the Bristol factory back in 1981, when my then-Bristol 29.9 was built. You will see that the boat was put together as 2 halves …You will see the seam down the middle both on the outside and inside. …. I personally saw the halves in the mold before they combined them.”
See the video here.