Cold molded fibre glass

[elrika12]

I'm considering buying a 1967 sail boat which was constructed using a cold mold technique which apparently makes it a lot stronger than current methods. Can anyone advise me on any likely problems with this type of manufacture and also if the age of the fibre glass is going to be a problem

Peter

[sailingdog]

Last I checked, all fiberglass boats are cold-molded... Are you talking about a cold-molded wood/fiberglass laminate boat, similar to the West System used by the Gougeon brothers??

The cold-molded wood boats, similar to the Gougeon brothers boats, are not considered fiberglass boats, but cold-molded wood laminate boats, as the majority of the strength and construction comes from wood laminate. The epoxy used in their construction is primarily to protect the wood and act as an adhesive. In a standard fiberglass boat, the majority of the strength comes from either the fiberglass or the fiberglass and the core, depending on whether it is solid fiberglass or cored fiberglass laminate.

I doubt that a boat made in 1967 is really any different from most of the boats made in the sixties and seventies. The knowledge level of the technology used in making GRP laminate boats back then was still quite limited.

Sounds like the seller is blowing smoke IMHO. It would be helpful if you said what the make/model/build of the boat was, as different boats had different reputations for quality of construction and durability. Also, be aware that you are discussing a boat that is 40 years old, with 40 year old technology, and that recent advances in laminate technology make modern laminates far superior, in many ways, to what was available 40 years ago.

[Jeff_H]

The term 'Cold Molded' refers to a type of wooden boat construction in which thin planks are glued together to create a boat. It is not a fiberglass construction per se. Properly done, the veneers cross each other and are oriented along the primary stress lines. Essentially, once glued up these veneers form a single sheet of molded plywood in the shape of the boat. Typically, cold molding uses epoxy resins for the adhesive and has a fiberglass external sheathing. In its most durable form, the wood veneers are saturated with epoxy, which when built carefully, seals the wood, pretty much eliminating any of the negatives normally associated with wood.

In its best forms, cold molding produces a very strong boat for its weight, far stronger on a pound for pound basis than solid glass but not as strong as a cored fiberglass hull. A roughly ten year old study published by BoatBuilder magazine concluded that cold molded wooden boats are have the lowest life costs of all construction types. It also concluded in a different study that cold molding was the least expensive way to build a professionally built one-off boat (but that study may have only looked at boats without round chines).

The problem with cold molding is that for all of its theoretical advantages, it requires a lot of skill and care to build properly and often these boats will develop problems over time where short cuts were taken. The other concern with this boat is that it was built in the 1960's. Cold molding really was developed in the 1970's and became progressively more reliable in the early 1980's as vacuum bagging was introduced as a clamping technique.

In the 1960's 'hot molding' was far more common. Hot molding used resorcinol and other phrenelic glues, the wood was glued up and then cured in an autoclave under heat and pressure. This technique was developed prior to WWII and produced some of the best boats of that era BUT it did not offer the rot resistance and worm resistance of cold molding. Hot molded boats can be a real problem if they have not been well maintained.

Respectfully,
Jeff

[sailandoar]

Might just be a confusion about the terms. There is a glass contruction method C-flex that might be described that way.

http://www.seemanncomposites.com/cflex.html
http://www.seemanncomposites.com/CFLEX%20MANUAL-WEB.pdf

[sailingdog]

Sailandoar-

I don't believe the Seemann composite technique you're referring to was available in 1967, especially seeing as the company was founded in 1970. I also believe the technique referred to specifically was developed relatively recently. However, Bill Seemann, the founder was building fiberglass boats in the 1960s.

As Jeff H pointed out, cold molded wooden boats are a fairly recent innovation, and in the 1960s, boats were either solid GRP laminate or hot molded wood strip construction.

Saying that the boat was built as a cold-molded fiberglass boat doesn't make any sense. Technically, you could consider all fiberglass boats being cold-molded, as there is no heat source used when they are being formed. Only recently has the use of curing ovens become used in the boat building industry—mainly with the production use of epoxy resins.

I'd really like to hear what particular boat this is describing.

[elrika12]

Thanks for all your inputs. The boat is a fibre glass John Alden ketch built in 1967 at Boston. The fibre glass in the cockpit is broken in places and I was concerned that this might be due to age of the fibre glass or some problem with build process.

[sailingdog]

Can you clarify what you mean by "the fiberglass is broken in places". It could have been caused by accidental damage, like dropping things on the fiberglass, or it could be caused by poor adhesion during the original lamination process. Without photos, (and even with) it is impossible to say what might of happened.

[dohenyboy]

what about covering a wooden hull in fiberglass? any pros or cons?

[sailingdog]

It is done a lot. The problem is that if you don't cover the entire hull and deck, water tends to seep in behind the laminate at the top edge... and then the laminate separates away from the wood.

Many boats are built using fiberglass over wood... this is a pretty common construction technique for home-built boats, and the Gougeon brothers, of West Epoxy fame, have done a lot of the writing about this area. I have sailed on a few home-built trimarans that were built this way.

Wood, as a boat building material is fairly easy to work with and fairly light. The main problem with wooden boats is the massive amount of maintenance they require. By encasing the wood in fiberglass, the amount of maintenance is generally not much higher than that of a fiberglass boat. Repairs are handled slightly differently, but overall, the upkeep is minimized compared to a traditional all-wood boat.

[rskaug]

I'm wondering if one would have trouble getting repairs to a cold molded hull. Techniques presumable would be different from fiberglass. Are there people out there who know how to do the work?