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Old 03-01-2016, 11:08 AM   #1
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What's wrong with Aluminium hull?

From what I read, Aluminium is cheaper, lighter, stronger and last much much longer than fiberglass, if these are true, why fiberglass is still the main stream hull material, not aluminium?

The cons of aluminium: Noisy, Colder, Galvanic corrosion etc, nothing seems to me too serious, am I missing sth obvious?
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Old 03-01-2016, 11:23 AM   #2
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From what I read, Aluminium is cheaper, lighter, stronger and last much much longer than fiberglass, if these are true, why fiberglass is still the main stream hull material, not aluminium?

The cons of aluminium: Noisy, Colder, Galvanic corrosion etc, nothing seems to me too serious, am I missing sth obvious?
An aluminium hull will cost 2-3 times as much as a GRP one. Once you've made a mould its easy to pop out dozens of hulls, but each alloy hull has to be individually welded.

The big expense after the high cost of marine grade alloy is the huge cost of welding. Welders must be coded and qualified for specific grades and thicknesses of plate; if the weld is even slightly overheated the alloy crumbles and degrades resulting in cracking or even structural failure of the joint.

Absolute cleanliness to hospital standards is needed to get good quality welds.

Commercial alloy fast planing boats are plagued with hairline cracks in the welds; often needing constant rewelding after a rough passage.

Every engineering descision comes with compromises!
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Old 03-01-2016, 11:51 AM   #3
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My friend here at the Marina has a 100 foot Broward aluminum hull a 1989 it is under contract and being surveyed as I type this. always the big concern with them is passing the survey wihout a bunch of expense on the hull
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Old 03-01-2016, 01:07 PM   #4
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The expense of maintaining the paint on an aluminum boat is much more than fiberglass. If you have a commercial boat that gets painted with a Home Depot roller that is fine, for a yacht it is 50% more for a paint job than on fiberglass and needs to be done in half the time span of fiberglass.
I have sold and will sell larger aluminum yachts and can tell a potential buyer that the expense of maintaining engines, air conditioning, and systems will be the same for fiberglass or aluminum, it is the yacht finish that will be expensive. However if the boat has had a recent paint job, touch ups can be done in a few years as patches will not show up as much of the rest of the paint looks good.
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Old 03-01-2016, 01:57 PM   #5
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I was involved in a 70 odd foot Al yacht that had some sort of electrical "incident" that ate up the zincs then proceded to eat hull plating. Once discovered and hauled, it was found to be a disaster. Basically replated the whole thing below the water line. I was not involved in figuring out what happened electrically.
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Old 03-01-2016, 01:59 PM   #6
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I have aluminum and I'll never have another fibreglass hull (except for the one I posted in "Interesting..."). Anodes are important, I have 20+. If you can't deal with the look of aluminum unpainted, buy fibreglass. You will hate painted aluminum. As soon as the coating is breached, the corrosion spreads underneath it and lifts the paint and it starts to look like crap. Look around the cleats of any painted Al boat. I like being able to dump bleach on it in the spring and hose it off. I like being able to bump things and wipe off the creosote[8^)] and I like being able to cut things off/open and reweld, leaving only an interesting patina.
I like being able to drill holes wherever I want to and never have to take off my shoes when boarding (unless there's something stuck to them).

I will never varnish something outside again.

I really like using a router with a carbide bit or a grinder to take off rough edges.

Its different.
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Old 03-01-2016, 02:13 PM   #7
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XS has it right.

So many tens of thousands of Al boats out there being properly cared for and built right. Plus they can be recycled. For a real good read go to setsail's web site and read as to why Dashew chose Al for his boats during the past 40 years or so. But, they do require a level of care and knowledge that doesn't sit well with all users. Ever been on a Coastal Craft?

All building materials have their negatives. Lots of Westport detractors out there given their below waterline hull construction. Yada Yada any thing not "mainstream". I've intimate knowledge of Browards and can state that for their price on the used market they are pretty interesting as well as being ready to eat themselves alive if not tended to properly.
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Old 03-01-2016, 03:32 PM   #8
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Down here (in Louisiana) we have many aluminum boat builders. Lighter, stronger and easily repaired. These guys build them from 12 ft on up. Lots of oil field related boats and commercial fishing/shrimping boats, as well as pleasure boats . They are more expensive than fg and most of the ones I seen over the years don't have that "yacht finish",but, I wouldn't hesitate to own one.
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Old 03-01-2016, 06:19 PM   #9
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Aluminum dominates in certain areas of the market. However, the advent of fiberglass boats changed the entire process of boat building to moulds. If you want to do a one-off then aluminum is cheaper, but want a production boat and it's fiberglass.

Been an interesting movement in yachts as well. At one time the over 100' market was dominated by aluminum. Just look in the US and you had Burger and Trinity. However, fiberglass boats are now very popular up to about 170'. However, the custom yacht builders do theirs in either steel or aluminum and even if the hull is steel the structure is often aluminum.

I ran across someone recently with a 60' or so Hatteras. He didn't realize his arch was aluminum. (Not saying all are, just some have been and his was).

I look at a builder like Coastal Craft in Canada. Beautifully designed boats. I think the only thing standing in their was is the market on the whole prevers fiberglass to their aluminum. I was told of one potential customer who went on one and he and his wife looked through the entire boat. Somehow then he was shocked when told it was aluminum and said he wouldn't dare buy an aluminum boat.

Why has aluminum been so much more successful in smaller fishing boats than in runabouts? Just the market's view.
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Old 03-01-2016, 07:28 PM   #10
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Fiberglass may be the worst of all worlds...but it seems to be the most forgiving of the uneducated or uncaring owner...and also the cheapest to get into...thus its popularity.


I love aluminum...but like Ski posted...I have seen almost new hulls totaled in just a few weeks because of stray current.
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Old 03-01-2016, 07:52 PM   #11
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Aluminum boat owner here. I absolutely love my alloy boat, but as stated above; keep up on zincs, galvanic isolators, isolation transformers, and any stray current. Specialized bottom paint is less effective and more expensive. Also, keeping up on topside paint is expensive (I learned to paint myself). I'd opt for an exposed alum hull, but down here it can get BLISTERING hot on your bare feet. I love the art of welding and the fact that my boat is one congruent piece of metal instead of a bunch of pieces of wood and plastic glued together. The ride is very "tight" comparatively.
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Old 03-01-2016, 07:57 PM   #12
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Old 03-01-2016, 08:00 PM   #13
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I have aluminum and I'll never have another fibreglass hull (except for the one I posted in "Interesting..."). Anodes are important, I have 20+. If you can't deal with the look of aluminum unpainted, buy fibreglass. You will hate painted aluminum. As soon as the coating is breached, the corrosion spreads underneath it and lifts the paint and it starts to look like crap. Look around the cleats of any painted Al boat. I like being able to dump bleach on it in the spring and hose it off. I like being able to bump things and wipe off the creosote[8^)] and I like being able to cut things off/open and reweld, leaving only an interesting patina.
I like being able to drill holes wherever I want to and never have to take off my shoes when boarding (unless there's something stuck to them).
Here's an aluminum darling boat...

2000 Darling Yachts Trawler Power Boat For Sale - www.yachtworld.com

just don't look below decks
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Old 03-01-2016, 08:06 PM   #14
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Why has aluminum been so much more successful in smaller fishing boats than in runabouts? Just the market's view.
I think aluminum is a 'throw-away' boat for many people's mind. It's the one you see stacked up around Gander Mountain and Bass Pro Shops... Low cost to build and easy to repair (patch plate and pop rivets or weld). Also, small boats are less likely to be left in the water, and have a minimal electrical system to cause stray current corrosion.

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Old 03-01-2016, 08:50 PM   #15
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California legislatures approve aluminum.

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Old 03-02-2016, 07:24 AM   #16
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"Aluminium is cheaper, lighter, stronger and last much much longer than fiberglass,"
,But as noted requires more highly paid and skilled labor to produce.

For a cruiser the Euro model of bare , no paint seems best.

After the world cruise a simple buffing with a scotch brite type pad and all the dings from med mooring , docks, pilings and bum boats along side just vanish!

GRP lasts a long time ONLY if it is not asked to flex often .,A boat hull is NOT a fishing pole .

Gell coat cracking is the first sign of flexing too much.
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Old 03-02-2016, 08:28 AM   #17
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"Aluminium is cheaper, lighter, stronger and last much much longer than fiberglass,"
,But as noted requires more highly paid and skilled labor to produce.

For a cruiser the Euro model of bare , no paint seems best.
Aluminum is stronger by weight only.

It has major fatigue problems and needs to have stress areas built up. This is a design issue.

The reason why many aluminum boats are not painted is that it has to be properly treated for paint to stick well. A poorly painted aluminum boat will be back to raw aluminum in time.

You can't use copper based bottom paints.

It is one notch away from zinc in the galvanic scale (which is why stray current problems are a real problem).

It tends to pinhole around impurities in the metal or welds.

Since it is a good thermal conductor, insulation is important regardless of temperature.

Depending on the alloy, aluminum tends to tear and puncture rather than stretch like steel.

Brits and Aussies say it funny aluminium
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Old 03-02-2016, 09:03 AM   #18
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Aluminum is stronger by weight only.

It has major fatigue problems and needs to have stress areas built up. This is a design issue.

The reason why many aluminum boats are not painted is that it has to be properly treated for paint to stick well. A poorly painted aluminum boat will be back to raw aluminum in time.

You can't use copper based bottom paints.

It is one notch away from zinc in the galvanic scale (which is why stray current problems are a real problem).

It tends to pinhole around impurities in the metal or welds.

Since it is a good thermal conductor, insulation is important regardless of temperature.

Depending on the alloy, aluminum tends to tear and puncture rather than stretch like steel.

Brits and Aussies say it funny aluminium
What do you mean funny? Lol.

Maybe the best of both worlds is what the navy likes, steel hull and alloy superstructure. You can get a special bi-metal strip to weld steel to alloy; its flash jointed with an explosion in a special container so there is no electrical potential between the two different metals.

A even better idea would be to fabricate below the waterline in steel and make the topsides, decks and superstructure in alloy ; no maintenance other than antifoul, ever!
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Old 03-02-2016, 09:25 AM   #19
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it's called detacouple bi-metal strips. an interesting process. There is a video on youtube on how the prep the materials using explosives deep in a cave. They then cut it into strips and you weld steel to steel, and aluminum to aluminum with no problems.

I would think the idea (not including expense) would be a hull of cupronickel and aluminum house.
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Old 03-02-2016, 09:34 AM   #20
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