Metal Hull vs Fiberglass

[Rick]

FRP boats constructed using vinylester resin do not blister. Iso resin properly wetted and layed up will not blister. Ortho resin is prone to blister yet, as has already been mentioned, not all ortho layups have done so, especially the very old ones. I do not recall the reason for that except it had something to do with the process used which was more costly than later processes almost all of which blistered (or were prone to do so).

Again, here is a case of general condemnation of a material for the wrong reasons.

Rick, I do not think anyone was condemning GRP, just pointing out that, like any other material,it is prone to certain problems. Not every wood boat has rot, and not every steel boat has rust, but it is safe to say if considering the weak points in various hull materials, these things must be considered. No matter what design, or material you come up with, I can probably find one that failed prematurely, and one that far exceded expectations. Law of averages.
In the same consideration, on the average, most fiberglass boats that have major blister problems were built around the late 70's-early 80's. Most steel boats that have issues are due to rust or electrolysis, and it is usually from the inside out.

[Wynand]

It all boils down to personal preferences.
That said, one has to considder the type of sailing intended.

If you want a social type of sailboat for weekends, or for sailing around the cans on race day, fibreglass is the way to go.
OTOH, if you want to do some blue water cruising, and knows for sure that whales wont surface underneath you at night, or you will never ground or strike reefs or simply run into semi-submerged floating debris, fibreglass is OK again.

But if any of the above are a real possibility, I would recommend a steel or aluminium hull for safety's sake..
With modern building techniques and epoxy paint systems, weight and rust is not an issue with steel anymore.

But then again, from this designers point of view, the best building material for sailing hulls is cold moulded ply. It is light, strong, cheap and wood worm resistant.

My personal choice of material for an offshore blue water cruiser - steel, period

[Jeff H]

"My personal choice of material for an offshore blue water cruiser - steel, period"

Spoken like a boiler maker.... but one thing that I agree with you about, from this designer's standpoint "the best building material for sailing hulls is cold moulded ply. It is light, strong, cheap and wood worm resistant."

Jeff

First let me say, Jeff, I agree with you completely, however, as opinions go, it is my experience that designers, and builders often look at boats as a work of art, and many have never gone offshore, some have not even owned a boat. For a real perspective, the best source is the low budget off shore cruiser. Someone who can not just write a check when things go wrong. Someone who has sailed, short handed, offshore and to remote destinations. THese are the people who will tell you the true shortcomings of the vessels they have owned.
THere is a certain cruiser/magazine owner that is currently very popular. I have read his stuff, and have known him for about 20 years, well before he started sailing. I have followed his exploits, and observed his budget. I suppose if I had a crew of 6 or 7 and could afford to drop $60000 every time I wanted to take off for a blue water cruise, I would have a very different perspective about what boat is best. However, I consider $1000 per month to be comfortable, so I find myself doing allot of the work myself. In fact, everything but machining, and that is due to the fact that I have not found room on my boat for a mill. Which brings me to another point. Plywood, and fiberglass does not take up much room. A few saws, and a cordless drill are also easy to store. I have a set of Oxy/Acetylen torches on board, but the tanks are very small, and welding with them is very limited. A TIG, or even basic arc welder is beyond the power requirements of any boat I have ever owned.

[witchcraft]

We all have our preferences. Any hull material has its pro's and con's, differences in maintenance requirements and building specs. Most of us have seen bad hulls in all materials.
We have a GRP ( circa 1968 british) she has never had a blister, ( she is up for sale), we liveaboard a steel hull, circi 1982 she has no rust, surveyor verified. They both require different maintenance. We love em both. The steel hull is meant for open water, that is a result of her sailplan, not her hull material.
thanks for letting me put my two cents worth into the fray
Fair Winds
Witchcraft

"The steel hull is meant for open water, that is a result of her sailplan, not her hull material"

Point well made!

[BILL_S]

Maybe some more specific questions will help make some headway on our boat material decision. More specifically, does anyone have any data on boat impact.. pounds per sq. inch. I saw some info on aluminum a while back which was impressive but have never seen anything on fiberglass? or steel. of course the hull thickness would have to be taken into consideration. I am most worried about floating debri, whales, logs and boats as my research has shown this is what sinks boats, in the middle of the night, in the middle of the pacific, not weather. I was ready to buy a tank (hans christian) but why carry around 30k displacement and 6 feet of draft if an aluminum boat will hold up just as well in the above mentioned situation, with half the displacement and draft.

Any info would be helpful...beginner here sorting through mountains of data and distortion.

[psneeld]

Anyone discussing blisters about fiberglass boats is already out of the discussion...not educated enough on fiberglass.

Even before blisters form (or not)...ALL composite hulls including those of epoxy and vinylester are absorbing water and slowly disintegrating (the act of hydrolysis). At what rate??? No one can tell unless you grind or core the hull. All GRP boats are undergoing hydrolysis...some with...some without blisters.

Anyone disagree? Well come on over with your grinder and help me grind off the bottom of mine...and I've spent a bunch of time investigating what happened to my boat and glass in general. If you decide to...don't just read up on boat glass problems...the marine industry has had its head up its butt for decades now...read the industry literature on composite tanks and piping. That will open your eyes and confirm the few truthful and knowledgeable folks in the marine world that discuss hydrolysis in GRP boats.

Does that mean GRP boats are bad or have limited lifespans? Not really...but without the proper knowledge going into an older GRP boat (or newer and plan to keep awhile)...you better do your homework well beyond boating forums...they are full of half truths.

[noelex 77]

I think you are going about the decision making process the right way. The first thing to decide is the best hull material.
For a long distance cruising boat is has IMHO that is aluminium. It has most of the advantages of all the other materials with few of the drawbacks. It is often advocated for strength and puncture resistance without the high weight of steel, but it also eliminates many of the problems associated with older fiberglass boats such as rot in the deck core, delamination, osmosis leaking fittings and problems with the hull and deck joint.
However it is particularly important with aluminium to get a good boat. It needs to be welded with great skill, be of the correct grade of aluminium. The design and construction need to isolate dissimilar metals and the electrical systems needs to be very well installed with dual pole circuit breakers etc.

Good luck making your decision.

[noelex 77]

Originally Posted by BILL_S

More specifically, does anyone have any data on boat impact.. pounds per sq. inch. I saw some info on aluminum a while back which was impressive but have never seen anything on fiberglass?

Fiberglass boats are not very puncture resistant no matter how overbuilt they are. A GRP Polyester resin structure can be "strong", if it is thick, but is a brittle material with little plastic range.

As a simple demonstration of this plastic range try crushing an aluminium can. It is not very strong because it is very thin aluminium with no framing, but even when deformed to nothing like its original shape the surface will usually stay intact and waterproof.

This image of a steel boat hit by a ship shows the amazing plastic range of metal. It sailed back to port.

[swagman]

I'm in the somewhat unique postion of having had several polyester, one epoxy, one aluminium yacht, and now a steel classic power boat.

From my experience what everyone else has told you about build quality is the right way to make the choice. Better quality work means less work for you longer term.

Personally, I would not worry about sailing away on any properly built boat............. but I was sitting on our last epoxy yacht in Gran Canaria when the steel yacht 'Gringo' actually tied up after being rammed overnight just between the islands.

For those who don't know, it was November 2007 when a small freighter T boned her midships that brought down the rig and left a huge dent in her stb side.......but did not sink her.

Of course it does not happen every often, but take my word for it - if they'd been on an aluminium, wood, ferro or GRP boat - they'd definately not have been sharing a beer with us that evening!

If it is of any help, overall we found we spent more time maintaining the aluminium boat than the current steel hull, and less work with both GRP materials (epoxy being definately the best) than the metals.

Cheers
JOHN

[justwaiting]

All the materials have their advantages and disadvantages but would agree with the posts that say Quality of materials and construction, maintenance by PO's. Making generalized statements about boats with a hull material is misleading at best. For example there are a number of different types of steel that have been used in yachts and this has a major impact on their perceived weakness - rust. But equally you need to consider that some of these boats have been built over many years in the open, well not the best start in life! I have owned a steel boat (along with a number of GRP boats) and would not hesitate to do so again given the right boat in the right circumstance. Those circumstances would be if i was to go fulltime cruising in risky waters that i did not know. I would not own a steel boat if it was going to sit in marinas for extended periods (maintenance and electrolysis issues). GRP boats i like because they are forgiving of poor maintenance, and i have a better skill set to maintain and repair them. Jeff H who i have a lot of respect for his knowledge of boats and his generosity in sharing with others believes that Ferro is a poor choice. If my understanding of him is correct sailing is every bit as important to him as destination. My interest in cruising and the sail aspect is only incidental to my focus. Therefore i need to take his wisdom and apply it to my own situation and interests. I have had the opportunity to sail on other peoples Ferros and there is a lot that i like about them. Wheels likes Ferros. He is another who i have the highest respect for. When i fist bought a sail boat i relied on his ( and Talbots) advice on setting up the boat for cruising. The only problems with the advice was when i didn't follow it. As for my next boat, well i am justwaiting

[Dockhead]

The fact that 99% of sailboats are made of GRP is not a coincidence -- GRP is a really outstandingly excellent material for this purpose. It's not perfect, but it has a great array of advantages.

If you need ultimate collision resistance, then go with a metal boat. In my opinion, this need arises if you are planning to sail in areas with sea ice, or perhaps in parts of the Pacific Northwest with a great deal of floating logs. Otherwise, I think most people will find it not worth it.

GRP boats are mostly pretty strong -- GRP is quite a strong material. Good GRP boats sometimes have an UHMW material in the bows. My boat, for example, is made of Kevlar from the keel forward. Hylas 54's are Twaron (the same thing, more or less, as Kevlar) altogether. I think Kevlar reinforced plastic is similar to steel in puncture resistance.

GRP has the enormous advantage of the great inertness of the material. GRP does not corrode, rust, or react to dissimilar metals. Gel coat over GRP is much longer lasting than paint on metal. GRP does not conduct electricity. Depending on the type of resin used, GRP might suffer from some very, very slow deterioration due to water absorption and/or osmosis. With modern resins, this is a trivial problem, and certainly nothing compared to the challenge of protecting steel or aluminum hulls from electrolysis. If all that were not enough -- GRP is cheap compared to metal.

So as I said -- it is no accident that 99%+ of sailboats are made of GRP. It's simply a great material.

One thing to consider, however, is the size of the boat. Metal will be heavier and heavier, compared to GRP, the smaller the boat, because there are plate thicknesses which cannot be reduced beyond a certain level. That means that these different construction methods do not all scale the same way. The bigger the boat, the more efficient metal becomes. Beyond a certain size, aluminum hulls might be lighter than uncored GRP without sacrificing strength. This can bring a significant performance advantage, but of course, at a cost.

Another thing to consider -- the safety of a hull is determined not only by the material, but by the design. Is there a watertight crash bulkhead in the bow? My present boat has one (my former boat did not). Some boats have an additional watertight bulkhead between the forecabin and other spaces of the boat.

Some boats -- like the wonderful Sundeers of Steven Dashew -- are compartmentalized altogether. There are no through-hulls in the main passenger compartment -- only in foreward and aft compartments isolated by crash bulkheads. Surely a design like this will be safer than almost any other boat, regardless of the material.

[David_Old_Jersey]

GRP is far more PO proof.

Steel is more Current Owner proof



(On average, exceptions apply - yadda, yadda, yadda )