Aluminium or Fiberglass HULL good and bad of both??

sailme88

sailme88

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Jan 19, 2010
1,171
Catalina 34 Casco Bay
If you sail on the salt, stray electric energy will make an aluminum boat a battery. A CG 47' aluminum patrol boat was scrapped due to a totaled hull that was consumed by a galvanic corrosion.
 
V

videorov

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Feb 7, 2013
63
Transcat 48 Fla
sailme88 said:
If you sail on the salt, stray electric energy will make an aluminum boat a battery. A CG 47' aluminum patrol boat was scrapped due to a totaled hull that was consumed by a galvanic corrosion.
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I see plenty with them sailing the oceans. I've read articles about fiberglass how water slowly breaks it down and gets into it over time. Electrodes might be needed on metal boats to keep them in great shape.
 
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dlochner

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Jan 11, 2014
11,401
Sabre 362 113 Fair Haven, NY
The question isn't which is better, aluminum or fiberglass, the question is which is better for what purpose?

The other relevant question is what is your intended use of the boat?

The quality of the build and the maintenance it has received is far more important than the material it is made of. A well built fiberglass boat is a much better boat than a poorly built aluminum one and vice-versa.
 
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sailme88

sailme88

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Jan 19, 2010
1,171
Catalina 34 Casco Bay
The citing of the CG 47footer was not anecdotal, it was/is factual. There was a well built boat and presumably with outstanding maintenance. I offered it because even with a very good preventative maintenance program, stray current found it's way into the bonding plane and destroyed the boat. Sacrificial zincs won't stop that process, slow it down a tad yes, stop no. The question asked sought opinions to determine the better hull material. I was careful not to state which was better as I've never owned and aluminum boat. But I did have and shared relevant knowledge about potential aluminum failures.
 
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dlochner

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Jan 11, 2014
11,401
Sabre 362 113 Fair Haven, NY
sailme88 said:
The citing of the CG 47footer was not anecdotal, it was/is factual. There was a well built boat and presumably with outstanding maintenance. I offered it because even with a very good preventative maintenance program, stray current found it's way into the bonding plane and destroyed the boat. Sacrificial zincs won't stop that process, slow it down a tad yes, stop no. The question asked sought opinions to determine the better hull material. I was careful not to state which was better as I've never owned and aluminum boat. But I did have and shared relevant knowledge about potential aluminum failures.
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If you are referring to the Stratton, it was repaired and is in service. https://www.marinelog.com/index.php...ifies-causes-of-stratton-corrosion&Itemid=257

Aluminum is a perfectly fine boat building material if it is done correctly, if there well designed cathodic protection and if it is maintained well. It seems to be the building material of choice for sailors exploring high latitudes, like Skip Novak, Evans Starzinger and Beth Leonard, and John Harries among others.

While fiberglass hulls are not subject to corrosion, stray current and galvanic corrosion can sink a fiberglass boat just as quick as an aluminum boat, because the corrosion will attack the underwater metals like rudder posts, prop shafts, and through hulls.

The which is better question is really the which material is better for which purpose.
 
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chrischesley

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Feb 14, 2017
29
Mainecat 38 Anacortes
Wood rots, fiberglass delaminates or blisters, aluminum and steel corrode. Rigging fails, engines fail, sailors fail, keels fall off. There is a 'horror' story for every scenario. Which is better is not the correct question...
 
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Davidasailor26

Davidasailor26

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May 17, 2004
5,071
Beneteau Oceanis 37 Havre de Grace
sailme88 said:
The citing of the CG 47footer was not anecdotal, it was/is factual.
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It may be factual, but it is also just an anecdote, and anecdotes are not data. As chrischesley said there are many different boat designs and many different failure modes for each. Just because aluminum hulls are more subject to one failure mode doesn't make them the wrong choice for all boats in salt water. There is, I'm sure, plenty of data suggesting that aluminum hulls can be durable, and plenty of precautions that would need to be taken with them. Just as with any other design decision there will be pros and cons. Which is "best" will depend on what weight each of those pros and cons have in a given use case.
 
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D

dlochner

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Jan 11, 2014
11,401
Sabre 362 113 Fair Haven, NY
sailme88 said:
The citing of the CG 47footer was not anecdotal, it was/is factual.
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Davidasailor26 said:
It may be factual, but it is also just an anecdote, and anecdotes are not data
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An anecdote is a single data point, it is datum, not data. Single datum points can be instructive and useful information to have, however, one can not make any generalizations about a class (like the class of aluminum boats) from one datum.

The Stratton's failure demonstrates the importance of good maintenance and good build quality. According to the article cited earlier:

The Engineering Analysis Board concluded that the unusual pattern of corrosion observed on the Stratton was caused by damage to the hull coating, caused by below-the-waterline welding, coupled with a cathodic protection system that was operating in an "underprotect" configuration contributed to the corrosion on Stratton's hull. Additionally, stray current corrosion from the welding was also identified as a contributing factor.
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The failure was not the fault of the aluminum, it was ultimately human error.
 
B

Barnacle Bill

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Jun 9, 2008
1,771
- -- -Bayfield
Most Mega Yachts are made of aluminum. A few, like Christensen, are made of fiberglass. Chris Craft Roamers came in either steel or aluminum hulls. There are meters inside hulls like this showing the range of electrical current the boat produces and hence you can keep it under control with the use of anodes, etc.
 
sailme88

sailme88

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Jan 19, 2010
1,171
Catalina 34 Casco Bay
The boat in question was stationed at Group South Portland in Maine. The boat was in the possession of a scrap dealer who was repeatedly fending off request to but the remains. Finally, because the boat was condemned it was cut in half until it was crushed. FACT
 
D

dlochner

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Jan 11, 2014
11,401
Sabre 362 113 Fair Haven, NY
sailme88 said:
The boat in question was stationed at Group South Portland in Maine. The boat was in the possession of a scrap dealer who was repeatedly fending off request to but the remains. Finally, because the boat was condemned it was cut in half until it was crushed. FACT
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Then the boat you are referring to is not the Stratton. Can you provide a reference? I'd be interested in knowing more about the corrosion effects as I'm involved with a NFP that has acquired a metal boat with corrosion issues. Anything that I can learn and document would be helpful, especially information on what caused the corrosion and why it could not be repaired.

Thanks for your help.
 
sailme88

sailme88

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Jan 19, 2010
1,171
Catalina 34 Casco Bay
I can try to contact the metal recycler that had the boat. This was a well guarded story. Initial stories regarding the 47's were about paint" problems". I'll see what info is available.. Many years and several change of commands have gone by.
 
D

dlochner

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Jan 11, 2014
11,401
Sabre 362 113 Fair Haven, NY
sailme88 said:
I can try to contact the metal recycler that had the boat. This was a well guarded story. Initial stories regarding the 47's were about paint" problems". I'll see what info is available.. Many years and several change of commands have gone by.
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Thanks. So far I've learned that the care and feeding of a metal hull is quite different from a fiberglass hull. Paint issues could be as simple as using the wrong bottom paint, you can't use copper based paints on steel or aluminum hulls. And all aluminum alloys are not the same, some are more well suited to being a boat in salt water and others, not so much.

Then there is the whole issue of stray current corrosion and galvanic corrosion. On steel and fiberglass hulls anodes are used, however, aluminum hulls need cathode protection. Not even sure what that looks like.

Anyway, my point being, aluminum, steel, and fiberglass are all good boat building materials. However, they all need to be designed and maintained properly. The boat I am involved with had 3 main issues, the bottom was not prepped properly so the barrier coat peeled off causing corrosion, there was inadequate and inappropriate anode protection, and the electrical systems (both AC and DC) were wired wrong such that the hull became part of the circuit.
 
Charlie Jones s/v Tehani

Charlie Jones s/v Tehani

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Mar 1, 2012
2,182
1961 Rhodes Meridian 25 Texas coast
dlochner said:
, Evans Starzinger and Beth Leonard, and John Harries among others.
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Beth and Evans aluminum boat was built in Fernandina Florida by a friend of mine- Topper Hermanson who had a yard there in the 80's. I visited him while it was being built.
 
sailme88

sailme88

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Jan 19, 2010
1,171
Catalina 34 Casco Bay
Dave, you're in NY so you've seen salted winter roads. Ever see aluminum that has been attacked by salt? It starts to display a layered effect. Soon you can peel it like mica. My understanding is that this is what basically happened with the 47'er. Pinhole leaks developed and progressed .
 
Daveinet

Daveinet

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Sep 20, 2014
1,320
Rob Legg RL24 Chain O'Lakes
I believe that fiberglass is better for a sailing yacht, as it can be built lighter for the same amount of strength.
 
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