Design Life

[issac82]

What is the design life of GRP boats.How can we estimate its design life?

[Fanie]

Hello Issac82,

GRP lives forever. Someone else may tell you otherwise but in my experience it will outlive you. The GRP should be protected from sun (UV) though or else the resin will disintigrate over time. If it is protected in my opinion there is no limit.

[amateur mariner]

Still how to predict the design life??

[CDK]

Like Fanie wrote, without UV protection by gelcoat or paint, the lifespan is short. I've seen repairs done 5 years ago where the glass is already above the surface. On the other hand there are well built boats from the 70's in good condition.
As a general rule, the parts that are installed/attached determine the lifespan of a boat. Stern drives in seawater: 15 years, in inland waterways 25 years. Stern drives without service: less than 5 years.

Another point is that long after the 1th owner has discarded his boat because it has lost its gloss, the 3rd or 4th owner may still be happy with it once the scratches have been repaired and the hull was painted over.

[bntii]

I am happily sailing about in one of the Bounty II series yawls- 53 years and going strong.

There is another exhaustive thread on this subject around here somewhere...
If I could summarize the thoughts in one sentence: If the material yields beyond a critical amount in each cycle, the design life will be limited to a finite number of cycles.

The engineers will no doubt weigh in ..

[joz]

What is the design life of GRP boats.How can we estimate its design life?

I read an article from Professional Boatbuilder to which they are starting to recycle old GRP boats that are 40 yrs old to which you place your old boat in this machine and it destroys the boat to which the fibreglass can be re used in the production of a new GRP boat (powder form), plus it seperates all items whilst it breaking the boat which is quite interesting.

[Willallison]

What is the design life of GRP boats.How can we estimate its design life?

Same simple answer as I gave in another thread... "Depends"

[ancient kayaker]

Way back in my motorbike days it was common knowledge that the fiberglass helmets we used back then softened with use and had to be changed every couple of years. I don't know why, body heat, moisture, poor material, whatever ... I wonder if it was the resin used and if some boats hade the same problem.

[amateur mariner]

Can somebody quote a reference about it?

[amateur mariner]

Somebody quote some reference of the statements already mentioned.If there is any mathematical formula published mention it over here.Waiting for answers

[Fanie]

There is no formula, only estimates.

To make an estimate valid you have to supply all the conditions.

[RHP]

I read an article from Professional Boatbuilder to which they are starting to recycle old GRP boats that are 40 yrs old to which you place your old boat in this machine and it destroys the boat to which the fibreglass can be re used in the production of a new GRP boat (powder form), plus it seperates all items whilst it breaking the boat which is quite interesting.

Joz do you have a link to that PB article I looked on their website and couldnt find it - I would be really interested to read it.

Thanks
Richard

[joz]

RHP

I'll try to find that edition for you give me a week or so.

[RHP]

Many thanks.

[Willallison]

Amateur Mariner, there is almost certainly a great deal of information about the duty cycles / design life of GRP, though much of it would be proprietory. The problem is that there are so many variables that impact on the results of such testing that they are all but worthless to the bulk of the designing / building community. Get five people to laminate a given part and you will get laminates with 5 different sets of properties. Hell - get one person to laminate the same part 5 times and the same will be true!
Different resins, fibres, core materials, laminating procedures, temperatures, curing times and conditions, humidity, mixing times... the list goes on and on...

[CDK]

The term design life is not appropriate here. It is used whenever someone designs a device and has to make decisions about materials, bearing sizes and permissible temperatures and other conditions. In that case there is also statistical data, like MTBF (mean time between failures) for the components used.

You do not design GRP to live a certain time, but you could design a boat to survive a certain impact, a maximum engine weight or a number of passengers. GRP like it is used now doesn't differ much from what was used 30 years ago with the exception of the bonding of glass strands when they discovered that certain materials were prone to osmosis. No sane person will use a material for a boat that is completely destroyed once seawater comes into contact with is. It happened in the past, but that was an expensive error.

[ancient kayaker]

Damage can be repaired, although some materials are easier than others. It is understood that an engineered material may be improved over a period of time but nothing lasts forever. If a material is subject to degradation over a period of time tht is an important issue and the information should be made available.

[Willallison]

Ok - seems our more complicated responses arent getting the message through, so I'll go back to my original (somewhat fascetious, I admit) answer.

It depends....

[FAST FRED]

GRP is almost always strong enough , the hassle is it is hard (either engineering or thickness/weight) to get stiff enough.

The early boats were really stiff , and seem to have unlimited lives.

Later thin wiggle wall boats are not worth considering long term.

Some not even short term.

FF

[ancient kayaker]

Ok - seems our more complicated responses arent getting the message through, so I'll go back to my original (somewhat fascetious, I admit) answer.

It depends....

Good point. My last post was too simple also.

As a former engineer, I could safely assume that a mechanical designer selected a material for a specific application knowing the capabilities of the material such as resistance to thermal, mechanical and other stress factors and susceptibility to fatigue failure. This is hardly news - all part of an engineer's life and responsibilities to client and society.

The stresses that can be applied to a boat are known from centuries of experience with wooden boats. The characteristics of the material are also reasonably well known, although it is impossible to be totally accurate with a grown product.

So where are we in the small plastic boat design field? Are the characteristics of resin/glass/carbon composite materials that have largely replaced wood sufficiently known? How long is a modern boat likely to be safe, if indeed it was safe to begin with?

Synthetic composite materials have been around for over a half-century. Surely by now values can be put on such important characteristics as fatigue life and loss of strength due to environmental conditions and simple passage of time? If not, then I have to agree with fast Fred; a plastic boat, like a car, is a sometime thing; better to toss it than fix it.

[amateur mariner]

can somebody tell me that does HSC rules tell us about the maximum stress encountered by the yacht depending on the type of boat

[joz]

Joz do you have a link to that PB article I looked on their website and couldnt find it - I would be really interested to read it.

Thanks
Richard

Richard and Others

The Article is in a magazine called Yachts International Jan 09 Edition (not Professional Boatbuilder my mistake) Page 158 to 160 and the title is called Fibreglass Boats: Here Today, Here Tomorrow. on recycling old GRP boats into new ones.

[joz]

Richard and Others

The Article is in a magazine called Yachts International Jan 09 Edition (not Professional Boatbuilder my mistake) Page 158 to 160 and the title is called Fibreglass Boats: Here Today, Here Tomorrow. on recycling old GRP boats into new ones.

Richard and others

An update please read this article from Eric Sponberg on Recycling Old Boats, its a 13 page PDF to which is at http://www.sponbergyachtdesign.com/RECYCLING%20DEAD%20BOATS.pdf


I hope this helps.