So, what can go wrong with aluminum?

[Stumble]

Originally Posted by Wckoek

Fastener, bilge, stray current, inability to use copper based antifouling, difficult to paint and paint doesn't last. Unlike steel which retain 90% of its strength on its welding joint, aluminum only has slightly more than half its strength.

With all these drawbacks and despite steel rusts, would you guys say that steel is easier to maintain than aluminum alloy?

I understand that aluminum boats retain value better than its steel counterparts, how about in terms of insurance cost?

There are more super yacht build in steel, or some with aluminum structure and steel hull, would this be a good compromise even for the smaller boats?

Superyachts are not really comparable, they have full time crew who's job it is to bust rust non-stop. on a 150' steel yacht it isn't uncommon to have someones full time job to be rust remediation.

For a pleasure boat I would never own steel. Yes it has some advantages, but it has a very real and regular maintenance requirement around sanding and painting. Worse you really have to get full access to the entire hull, every stringer, every support, everywhere, or you will have issues down the road.

Aluminium for all its technically possible issues seems to generally avoid them in practice. Yes you need to be cognizant of good practice when doing wiring work, and housekeeping, but in reality it is far more maintenance free than steel.

If you really want a metal boat I would always choose aluminum.

[David M]

Hundreds of thousands of workboats are made of aluminum. If it were a bad material to use the builders of these boats would still be using fiberglass. Remember, commercial boats have to be reliable and durable above anything else.

I have been operating an aluminum research boat for almost 30 years now. I am not one who is discussing aluminum without any personal experience with aluminum.

https://www.google.com/search?q=alum...=1623&bih=1399

[SecondBase]

Originally Posted by Stumble

Jim,

I may be wrong, but I am pretty sure that most aluminium boats use a mix of aluminium alloys. 5086 (corrosion resistance) for the underwater hull, 6061 (strength) for non-submerged structural elements, 5052 for the hull and deck. of course not all boats may go into this detail, but if you are trying to maximize the benefits it's not a bad idea.

How can I test an aluminum build to confirm which alloy(s) were used? Do I need to test that-or test finding that would be concerning?

Application is saltwater and brackish to almost fresh water, twin hulls, bridge deck etc.

[David M]

Originally Posted by SecondBase

How can I test an aluminum build to confirm which alloy(s) were used? Do I need to test that-or test finding that would be concerning?

Application is saltwater and brackish to almost fresh water, twin hulls, bridge deck etc.

In all likelihood, the plate that the hull was constructed of will have the manufacturers labels, on the inside of the hull. The grade of aluminum will be part of that labeling. It is unlikely that the manufacturer will have spent the time to remove the labeling before welding. If the labeling is gone, then be suspicious. I would not touch that hull unless you want to scrape off some aluminum filings and have access to a mass spectrometer...just kidding about going through the hassle of doing that.

Look at the quality of the welds as well. That is huge. If the welds look amateurish, then run away.

Look at the scantlings as well. Really only true professionals who have plenty of experience designing aluminum hulls should be designing aluminum boats....unless stress cracks don't bother you.

If you don't know what to look for in welds then hire a marine surveyor who specializes in aluminum boats or hire a USCG certified aluminum welder to come look.

Never ever buy an aluminum boat from a backyard builder. There is just too much that could be wrong and you would never see it.

It took many years of trial and error to get aluminum hulls to the point where they are very reliable.

Much of the bad reputation that aluminum hulls have comes from backyard builders who did not know what the hell they were doing.

Electrolysis is not an issue if you know what you are doing, know what to do and know what not to do. I have not had any electrolysis in almost 30 years.

[Wckoek]

Originally Posted by Stumble

Superyachts are not really comparable, they have full time crew who's job it is to bust rust non-stop. on a 150' steel yacht it isn't uncommon to have someones full time job to be rust remediation.

For a pleasure boat I would never own steel. Yes it has some advantages, but it has a very real and regular maintenance requirement around sanding and painting. Worse you really have to get full access to the entire hull, every stringer, every support, everywhere, or you will have issues down the road.

Aluminium for all its technically possible issues seems to generally avoid them in practice. Yes you need to be cognizant of good practice when doing wiring work, and housekeeping, but in reality it is far more maintenance free than steel.

If you really want a metal boat I would always choose aluminum.

I see, another thing is trawlers, even for pleasure ones are almost universally build in steel, but rarely I see an aluminum trawler, was it that aluminum alloy doesn't work well with specific boat type?

[softdown]

These folks make some pretty nice yachts out of aluminium (https://en.wikipedia.org/wiki/Aluminium). I believe this is a word variant for aluminum.

http://perininavi.it/en

Steel yachts are going to get pretty hot in the tropics. We all know about the possible corrosion issues.

[Wckoek]

There are also boats with steel hull and alumnimium superstructure, apart of weight saving, was there any extra benefits and drawbacks to this type of building method?

[roverhi]

Titanium is and has been available from other sources than the Soviet Union. They became one of the leading suppliers of it for their aircraft and ship building before they turned into just Russia. With the collapse of the Soviet Union in the late '80s and the downsizing of their military, there was a flood of titanium and skilled fabricators to build stuff with it. Titanium bicycles at relatively cheap prices flooded the market for awhile as one of the beneficiaries. That supply has long since dried up, unfortunately.

In the late '60s the US military was the biggest user of titanium. The swing wing aircraft like the F14 used massive amounts of titanium in the swing wing mechanism. The Soviets, at that time, copied the designs but either didn't have a source or the ability to fabricate titanium. They used high strength steel where the US planes used titanium. Believe the back end of the F8 skin was Titanium and that plane dates from the '50s

[double u]

to come back to the subject of al-boats:
when we sold ours we'd had it for 10 years/2 rtws & it was 18 years old.
known al-related probs that would have needed fixing for "the-next-trip"
chainplates, particularly forestay-chainplates were "chewed-up" & would have needed fixing, would have entailed some surgery & welding
much more serious an unknown prob:
after abt a year the keel started corroding through from the inside out on the new owner (galvanic action between the supposedly isolated with casting-resin lead & the alloy because of unnoticed & unseen waterpenetration)
this would have entailed MAJOR surgery...
(imho a very good way to have a keel onan alloyboat is a hollow fin, inspectable from the top, & a leadbulb bolted on with 3-4 totally oversized horizontal bolts, electrically completely insulated from one another: bolts sleeved, wshers, sealant, the works. the part of the fin the bolts go though solid AL, let into & welded to the hollow fin)

everything else was minor & mainly cosmetic
still watch for coins: discovered one lying on a stringer that had eaten away some of the plating-thickness, so in the long run...
antifouling's a problem as is thermal insulation (quitecomplex to do well)
biggest prob for us: practically none on the secondhand market (if you don't want an Ovni or a very old one...)

[Wckoek]

Originally Posted by double u

to come back to the subject of al-boats:
when we sold ours we'd had it for 10 years/2 rtws & it was 18 years old.
known al-related probs that would have needed fixing for "the-next-trip"
chainplates, particularly forestay-chainplates were "chewed-up" & would have needed fixing, would have entailed some surgery & welding
much more serious an unknown prob:
after abt a year the keel started corroding through from the inside out on the new owner (galvanic action between the supposedly isolated with casting-resin lead & the alloy because of unnoticed & unseen waterpenetration)
this would have entailed MAJOR surgery...
(imho a very good way to have a keel onan alloyboat is a hollow fin, inspectable from the top, & a leadbulb bolted on with 3-4 totally oversized horizontal bolts, electrically completely insulated from one another: bolts sleeved, wshers, sealant, the works. the part of the fin the bolts go though solid AL, let into & welded to the hollow fin)

everything else was minor & mainly cosmetic
still watch for coins: discovered one lying on a stringer that had eaten away some of the plating-thickness, so in the long run...
antifouling's a problem as is thermal insulation (quitecomplex to do well)
biggest prob for us: practically none on the secondhand market (if you don't want an Ovni or a very old one...)

Keel corrosion, sounds like a very expensive and dangerous problem to fix.
If this is the yard's fault on a new construction, are they going to fix the problem out of their wallet?

[double u]

wasn't a yard-prob: the PO had a slight grounding - apparently enough to have some water get into the keel which was impossible to inspect as it was welded closed on top
very solid boat otherwise. very. lifting the floorboards & looking at all those floors & stringers was always confidence-instilling. a couple of times we drove her upwind under stormjib & triple reefed main so hard we thought our brains would drip out the ears, heeled at such an angle we hadn't though she could be sailed at...still think back fondly at her...Pouvreau 11.30, design Gilles Vaton, built 82...

[Wckoek]

Originally Posted by double u

wasn't a yard-prob: the PO had a slight grounding - apparently enough to have some water get into the keel which was impossible to inspect as it was welded closed on top
very solid boat otherwise. very. lifting the floorboards & looking at all those floors & stringers was always confidence-instilling. a couple of times we drove her upwind under stormjib & triple reefed main so hard we thought our brains would drip out the ears, heeled at such an angle we hadn't though she could be sailed at...still think back fondly at her...Pouvreau 11.30, design Gilles Vaton, built 82...

First time I heard of the designer Gilles Vaton, very innovative designer.

[double u]

not exactly a "new hand":
De la Whitbread à la Volvo / Whitbread 1981-82 - Charles Heidsieck III : une jupe qui a fait tourner les têtes !
http://www.vaton-design.com/vatondes...ton_design.htm
one of the very great designers

[Wckoek]

Originally Posted by double u

not exactly a "new hand":
De la Whitbread à la Volvo / Whitbread 1981-82 - Charles Heidsieck III : une jupe qui a fait tourner les têtes !
Architecture and naval engineering
one of the very great designers

Protégé of Mauric, one of my favourite designer.
There are many great designers in France, it's a pity that they aren't as well known and accessible to the English speaking world.

[DeepFrz]

Originally Posted by Wckoek

Keel corrosion, sounds like a very expensive and dangerous problem to fix.
If this is the yard's fault on a new construction, are they going to fix the problem out of their wallet?

That was discovered on a 20 yr. old boat. Know any 20 yr. old fiberglass boats that don't need significant repairs or have gone through a very arduous and expensive refit?