My boat was built in 1974 right in the middle of the Fiberglass boat boom when the "chopper gun" was invented and hulls could be laid up in a day. Older boats laid up by hand with a bucket of resin and rollers took weeks to a month to build. They all used the same polyester resin that was available cheap
from WWII stocks. New resins did not make their entrances in the mass manufacturing of sailboats until about the 1990's. It was strictly a matter of cost - the old resin was cheap
and turning out the most boats at the lowest prices the objective. "One-off" and high end (price) boats were done with much better quality control and resins. Epoxy
would be the best but is 10 times more expensive than polyester resin.
- - The number one problem with FRG (fiberglass) boats built during this time period was incorrect mixture of the resin as it passed through the chopper gun. This resulted in about 10 years later the massive appearance of "osmotic blisters". It takes 5 to 10 years for water to work its way into the hull and form blisters
. There are two types of them - Gelcoat
blisters (that still occur in new technology boats) and laminate blisters. Gelcoat
blisters are a cosmetic nuisance and not a structural problem. They are relatively easily fixed by sanding
off the gelcoat and applying an epoxy
barrier coat then new bottom paint
- - However, laminate blisters are a structural problem as the blister actually separates the layers of fiberglass cloth and can lead to structural failure of the hull. These are primarily caused by poor mixing of the resin during layup
of the hull. They must be ground out (removed) and new fiberglass cloth and matching resin added to restore the hull. FRG boats are "ultimately repairable" - or you can tear away, knock off, and whatever to the FRG hull then with correct procedures lay up new or patch the old hull and restore it to original integrity. I know because I was in that business for 19 years.
- - If the history
of the boat includes removing and proper repairing any and all blisters plus the addition of a good barrier coating, then you can be satisfied that you will not have to deal with that problem. If the boat was laid up by hand and a chopper gun never was used, it is highly likely that you will never have a "blister" problem with the boat. If the boat is newer than 1990 and came with a "5-year" hull warranty it will most likely develop blisters. If the newer boat came with a "10-year" hull warranty then the hull is unlikely to develop a blister problem.
- - Costs of blister repair range from a couple hundred dollars for gelcoat blisters that you repair yourself on up to $10k or more for professional repair of laminate blisters. You should factor that into your purchasing
equations as it can be a significant cost.
- - Any evidence of collision
damage will demand an interior
inspection for cracked or broken tabbing between the hull and interior
bulkheads. Manufactured boats rarely have a tabbing problem unless they were in a collision
. Poorly built "home-made" boats could have all kinds of problems depending upon the skill of the person who built it regardless of hull material (FRG, steel
- - Many of the mainline FRG manufactured boat have "drop-in" interiors. There is no tabbing as the whole interior of the boat is built separate from the hull - bulkheads, floors, plumbing
, etc. and then lowered into the finished exterior hull and glued together. This is a very efficient and economical way to mass-produce boats. This technique appeared in the 1980's and is still in use.
- - If you have more specific questions on FRG construction and what to look for, PM me as the discussion can get quite long and involved.
Fair Winds, Jim on sv/OSIRIS