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Old 11-08-2009, 22:51   #1
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What Problems Do You See with Old Fiberglass?

I have been window shopping through alot of boats. Alot of the boats I like that are also in my price range have been built in the 70s. I am curious what problems you can run into in an old fiberglass boat. Is there a point when the stress of wave after wave finally bring fiberglass to it's breaking point? If an old boat is well maintained (new wiring, good engine, good rigging, etc), is there a point where the fiberglass ends up deteriorating to the point that the boat is no longer seaworthy?
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Old 11-08-2009, 23:13   #2
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A friend of mine has a theory that during the gas crunch of the early/mid 70's boat builders used alternative resins to lay up fiberglass hulls and this is a big reason for blisters and osmosis in boats of this vintage.

I do not know if this theory is correct but I would be cautious of boats of this vintage.

OTOH - problems with a 70's boat should have appeared already and either been fixed or the boat is gone.

The issue is whether it had problems, was fixed and if the fix was done properly.

If fixed properly then I see no problem. In any case at all a good survey is a prerequisite.

As far as structural integrity of a fiberglass hull? Certainly a "light" boat that has seen years of heavy pounding may develop structural problems.
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Old 12-08-2009, 02:48   #3
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Tabbing and rudder...

Two of the the problems mentioned with older fibreglass boats on this Forum are tabbing failure and water intrusion/weld failure in the rudder.

Dave Gerr in his book "Boat Strength for Builder, Designers and Owners" discusses how good practice tabbing can be done. I would think that this would be much more important on older fibreglass boats.

Careful inspection of the tabbing between bulkheads and the hull on older boats by a competant person may be a good idea, with upgrading a serious consideration if it is deficient.

There have also been reports of rudder problems. These look to relate to water intrusion leading to corrosion of the stainless steel internal structure and separation of the fibreglass/foam component.

Again careful inspection of the rudder by a competant person may be a good idea.

Useful information also could be gained by discussing maintenance of similar boats with their owners.
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Old 12-08-2009, 05:29   #4
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Two of the the problems mentioned with older fibreglass boats on this Forum are tabbing failure and water intrusion/weld failure in the rudder...
PBB magazine had (June/July 09) an interesting article, by Bruce Pfund, on Tabbing:
Professional BoatBuilder - June/July 2009
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Old 13-08-2009, 07:50   #5
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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, aluminum, wood).
- - 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, electrical, 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
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Old 13-08-2009, 08:08   #6
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Failure of the hull/deck joint. Fortunately we were only a couple of miles offshore when it let go (we had to beach the boat). After that I've never owned a glass boat long enough to have personal experience with other failure modes.
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Old 13-08-2009, 08:28   #7
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S & S - was it a home-built FRG or a factory built mainline boat? Hull/deck joints are critically important but most mainline manufactures "over-kill" on this aspect of boat construction as the consequences are so serious, not only to the people on the boat but the liability insurance costs to the manufacturer. When looking at home-built or very low volume manufacturers this would be at the very top of the list of things to inspect.
- - A new development with high end brand new boats. The manufacturers are building hull thickness way below "classical" standards for FRG hull thickness. I saw a million dollar monohull up on the rocks in Martinique with rock ripped and torn hull. It was a 50 footer and the hull thickness was 1/4 inch below the waterline. The new resins and types of fiberglass are significantly stronger than ordinary fiberglass so theoretically stronger or as strong as classical FRG. So they can build thinner. But rocks do not worry about "engineering" they just punch holes. My 50footer has 1 inch thickness below the waterline and ABYC and other standards call for 3/4 inch thickness for classical glass of this size boat.
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Old 13-08-2009, 08:42   #8
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The answer to the original question is no. There have been no credible reports of fiberglass 'fatigue' that have rendered a boat less safe. Tabbing failures, especially at the hull to deck joint, can cause failure (as has been mentioned).

The Navy did some destructive testing of fiberglass barges many years ago and determined that the degradation of fiberglass over time was negligible.

One point, while epoxy is considered preferable by some to fiberglass resin, it has a significant flaw. While epoxy is better for a repair, (the bond is stronger of course) it is much more susceptible to UV degradation then regular old fiberglass resin. If our boats were laid up with fiberglass and epoxy, any breaks in the gelcoat / paint would cause the hull to break down under them over time.

Works out pretty well for all of us.
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Old 13-08-2009, 09:00   #9
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Originally Posted by osirissail View Post
S & S - was it a home-built FRG or a factory built mainline boat? Hull/deck joints are critically important but most mainline manufactures "over-kill" on this aspect of boat construction as the consequences are so serious, not only to the people on the boat but the liability insurance costs to the manufacturer. When looking at home-built or very low volume manufacturers this would be at the very top of the list of things to inspect.
It was a factory production boat, probably 10 years old at the time. It was blowing in the 20's gusts to 30, short chop (typical Lake Michigan day in late summer). My previous boat handled similar weather fine, so who knew?. The flatter underbody of the new boat took some slams and Zing!-she opened up like a tuna can on the port side. The hull and deck flanges were bolted with the tabs fitting into a groove on the rubrail which I guess is pretty standard.
That ended my foray into glass boats-all my others (pre and post) have been wood.
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Old 13-08-2009, 10:21   #10
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Wow. Thanks for taking the time to explain that osirissail.
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Old 13-08-2009, 10:31   #11
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Blisters can be very common in boats with no chopppergun in the hull layup. I agree with hull and deck joint, there have been published cases of this joint separating on older boats. Boats are flexible and fiberglass layup is brittle, especially the older it gets! You can bend a racing boat with the backstay adjuster a few inches! Visualize pulling the bow and stern up on a pea pod.... what happens at the center? (beam) That's right.... it get's wider... In my younger years I tried to rejuvenate a couple of old (free) fiberglass dingys that had been sitting in someones yard. That is when I learned that fiberglass layup deteriorates. You could literally tear one of those dingys apart with a hammer and gloves.... or your foot. The layup gets brittle, that combined with the high resin percentage used in the 70's would make me want to avoid all but the very best of those older boats.... If going offshore....
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Old 13-08-2009, 11:01   #12
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i own 2 boats built between 1975-1979--there is no failure in the fiberglass--the osmotic blisters --if dry , without holes in center(making them wet blisters) are over rated and no problem--they do not constitute failure of fiberglass. the only failure i have seen with fiberglass in a boat made in any time btw--blisters, as over rated as they are, are easily fixed....just need to be dried out for a long period of time frame was with a boat that had a bad hull to deck connection and the water got into the spaces between the gelcoat and the mat used as filler under the roving, or woven bits of fiberglass, in which case, the material was mushy and the boat was a choppergun built boat of ill repute LOL. look for a hand laid boat--there were many still being hand laid then--and go for it----
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Old 14-08-2009, 09:02   #13
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S & S - You are quite correct, back in the "olden days" there wasn't the super suing/liability problems we have today. So some "manufacturers were cranking out boats with major "cheating" on the design specs in order to save time and money. My boat is one of those. Incredibly cheap to buy, but incredibly poorly built hull. I had to totally build a new hull outside the old hull, after repairing the old hull. Whole process of getting the boat ready took 11 years in a boat yard. Since I had to totally remove everything inside the boat except structural bulkheads, I was able to carefully inspect every inch of the deck/hull joint which was the only good part of the hull I found on this boat.
- - As the boats get smaller in size, the problems of hull/deck joints can be a serious consideration as there is less room and thinner material used and more flexing is possible which would stress the joint.
- - All in all the older the boat, the less expensive the boat - the more attention is needed to carefully inspect for all these problems before purchase.
- - Water leaking down chainplates that are internally mounted and pass though the deck is a common situation where the chainplate get intragranular corrosion and can snap in half quite easily causing loss of the standing rigging. \
- - Considering that the older the boat and the more money needed to bring it back to ocean ready status (typically an amount of money equal to the purchase price in older boats) - It might just be worthwhile to simply put all that money into a much newer boat or new boat. It is a bigger money hit up front but the amount of time and sweat your save is worth taking out a loan to afford the newer boat and get out onto the water.
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