Fibreglass hull life duration?

[RichH]

That's 20 years until they have measurably less strength than when built. 20 - 30 years ago, most fiberglass boats were built conservatively enough that they will still have enough strength for safe service. They may even be stronger than some new boats built today.

For the boats built after constant oilcanning became acceptable in the market, the strength degredation after 20 years could be a much more significant issue.

Realistically, modern box-beam construction and lighter weight advanced composite structure are vastly superior than the heavy 'single skin' fabrication of many years ago. Yes indeed, oil-canning was a problem that quickly moved the preference of hull construction to either very 'thick' single-skin or cored composite structure, ... had these discussions with the Pearson Brothers when my P30 (was campaigning the boat at the time) turned out to be a 'squishey flexing bowl of jelly'. Their reply at the time was 'sail it until it sinks' but they agreed that my adding longitudinal stringers would be a corrective (to adverse flex) measure but would add weight; weight adding nothing of benefit to the structure as their tested opinion was that such hulls could take many flexure cycles as the then 'rule of thumb' was that a hull built at 4X safety factor could survive a very long time versus fatigue .... and they were indeed correct.
Like most all structures subject to repetitive dynamic stress if they are built 4X as strong as 'typical', then fatigue doesnt seem to be a problem. Modern hulls are vastly superior to the so-called 'overbuilt' hulls of the past ... and for many many reasons: lighter weight, stronger, lower cost, etc. etc.

If my 26000 lb. 'crab crusher' was 13000 lb., it'd be ~10" less deep in the water and it'd be a rocket.

 

[Stu Jackson]

Just to add a little correction to your 'post'.
Please dont consider this to be 'politics' as this reply is **history* not opinion, and involves the US boating industry in the 1990s
The infamous BOAT TAX, ...

Rich thanks for the history.

Let's examine this a bit. Back in the 60s most boats were in the 25 foot range. So the Kennedy proposal would be $5 for the first 15 feet (the first 14 to 16 feet $5) plus $2 per foot over 15 feet is 10 X $2 = $20 + $5 = $25. Even if the boats were average 35 feet, the cost, doing the same math, would be $45 a year. Even back then, I don't think that would be considered burdensome, and would most likely have been negotiated down to maybe half that in Congress if it had ever passed. Of course, it may just have been more politicians trying to squeeze more $ out of us.

And that's for a reasonably defined goal, not just adding to the treasury to raise money, but doing something with the money for the "outdoors." In California, the successful Dept. of Boating & Waterways does great work because they get the boating gas tax funds and put it back for boaters. It's the only self-sustaining government dept. Of course, the politicos can't wait to get their hands on it and every six months or so try to get rid of it or to meld it into the Dept. of Recreation which is so thoroughly riddled with corruption and greed as to make it almost third-world!

I would be VERY interested in the same kind of documentation of your claim that Ted Kennedy fathered the infamous larger AND MUCH MORE BURDENSOME NEW BOAT boat tax, which was far more invasive than President Kennedy's tax, discussed above.

 

[RichH]

Rich thanks for the history.

I would be VERY interested in the same kind of documentation of your claim that Ted Kennedy fathered the infamous larger AND MUCH MORE BURDENSOME NEW BOAT boat tax, which was far more invasive than President Kennedy's tax, discussed above.

You can start here: http://www.freerepublic.com/focus/news/819936/posts and then go to the Sen. Geo Mitchell (co-sponsor) library website and do your research there ... to identify the correct Senate Bill number from that time (then lookup the total Bill that included this 'rider'.
You can also usually find this ("boat - luxury tax") in published technical economic papers as its always highlighted as government oversight/mal-influence on economics that usually does the exact opposite of its intention - a classic reference for economists.

 

[zeehag]

fiberglass hulls do not rot . they do not fall apart. they sink in their slips. is one reason why there is no place to day to place a boat when you buy it. fiberglass hulls last very very long time. fiberglass over wood and cold molding have shelf lives--but not fiberglass hulls unless made by clipper marine, and they are no good to begin with.
the reason they sink in their slips is because some body who owns thekm didnt change out a thru hull fitting or fix the toilet or even go to see his boat in many yrs----fiberglass doesnot rot nor break down nor "exfoliate"

 

[Franklin]

"Fiberglass" as we know of it today is actually a mix of fibers of glass and some kind of resin. The fibers give it tensil strength and the resin gives it compression strength and bond the layers together. The fibers do not degrade due to time or exposure to sun or anything except "Fatigue" where the fibers are bent enough through time to cause them to crack. The compression strength of the resin is supposed to stop the flexing, but newer models also rely on another material sandwiched by the fiberglass to give it a stronger compression strength at a lighter weight with the most common being Balsa wood...these are called cores. This reduces the tensil strength as there are nearly as many fibers but they've found that compression strength is more in demand so no real lose except unneeded weight.

Now the core can be degraded by water getting in but as long as it doesn't, that's good for like forever. So that leaves the resin. Resin is just a chemical reaction and most chemical reactions do have shelf-lives and I'm no resin expert and I even failed chemistry in high school, but I don't think even the weakest resin, polyester, would degrade on it's own in 30 years.

However, if "fiberglass" endures enough stress to cause it to flex and does so repeatedly, the resin will crack and the compression strength will fail causing the fibers to bend. Now I know from experience that it takes a ton of flexing of the fibers to crack so just because you hear that the new boats flex and develop stress cracks, don't be alarmed because it take a hugh amount of flexing for it to fail. Normally, fiberglass holds up until it runs into something more powerful than it can handle and then it breaks just like wood would.

Want to know how much flexing fiberglass can take, go to Home Depot and spend $10 on a small sheet of matt and a small amount of polyester resin. Mix the resin with the harder and brush on the resin until the fibers are clear but leave a good two inches un-coated so you can hang that little piece on the lift lines to let it dry/harden. Come back in a day (will be hard in an hour but will not be fully cured) or more and try to break it by flexing it. You will gain a new appreaciation for your boat and what it can take with that little test.

Yes, the boats stick around a lot more than they were meant to. You see tons of fiberglass boats that the hulls and decks are just as solid as the day it rolled off the floors but the rest of the boat is in shambles and the owner never sails it because it's not pleasing to be around. So they just float there in the slip waiting for the day one of the hoses will fail and she will sink.