Alloy yachts

[d design]

Hmmm first thing that comes up with alloy boats is corosion.. Intresting

[Cheechako]

generalisms:
Aluminum must be engineered very well, it's far more "bendy" than steel.
Aluminum often likes to shed paint about every 3 years or so... unless you are lucky. As mentioned, a bad "electrical potential" can cause huge damage...very quickly.
Aluminum requires special attention to bottom paints etc.

[ccannan]

Originally Posted by d design

What are the pros and cons of an aluminiun alloy yacht?

I own an aluminum boat. The biggest con is trying to get paint to stick to it. Many people forgot topside paint for that reason, but it will still need bottom paint. Before you can apply bottom paint, you need to apply a primer/barrier coat, the application of which is complex, time consuming, and expensive.

Another concern is stray current corrosion from the boat's own electrical system. However, with proper wiring practices, and maintenance one should be able to avoid any problems.

[Panope]

Originally Posted by d design

Hmmm first thing that comes up with alloy boats is corosion.. Intresting

My choice in mentioning a "con" (corrosion) first has nothing to do with its importance relative to other factors.

I chose to mention a "Con" first because (as an aluminum boat owner) I did not want to come across a horn blowing, self-congratulating, look at how great I am, my boat is better than everybody else's, biased, jerk.

BTW, I do like my boat better than everyone else's but it has nothing to do with what it is made out of.

Steve

[d design]

Originally Posted by Panope

My choice in mentioning a "con" (corrosion) first has nothing to do with its importance relative to other factors.

I chose to mention a "Con" first because (as an aluminum boat owner) I did not want to come across a horn blowing, self-congratulating, look at how great I am, my boat is better than everybody else's, biased, jerk.

BTW, I do like my boat better than everyone else's but it has nothing to do with what it is made out of.

Steve

+1 on that

[Stu Jackson]

Originally Posted by carstenb

Stu - there's always something known as a "sunupper". Remember, the sun is always over the yardarm somewhere……………….

Is that like dinch or lunner?

[Andrew Troup]

Originally Posted by Cheechako

generalisms:
Aluminum must be engineered very well, it's far more "bendy" than steel.
...

No argument with your other points which I didn't quote, and I also agree aluminium must be well engineered, but I disagree slightly on the main reason.

An aluminium panel the same weight as a steel panel of the same length and breadth, will be so much thicker as to more than bring the stiffness back on a par with steel.

Even though the inherent stiffness of aluminium is only one-third that of steel, the overriding factor is that stiffness goes up with the third power of thickness, and aluminium is one-third the weight of steel:

However in practice aluminium boats are almost always built to be lighter, so here's a more realistic comparison:

An aluminium panel for a boat equivalent to one which would use 3mm steel will probably be 5mm thick, which will weigh 55% as much as the steel panel, but it will actually be over 1.5 times as stiff.

(for the latter figure: [5mm/3mm]^3 for the added stiffness due to thicker panel, multiplied by one third for the lower inherent stiffness of aluminium as a material)

My take is that the main engineering difficulty is because welds in marine aluminium never attain the strength of the parent metal, and even to approach that strength requires careful design to ensure good access with the welding gun, the lowest possible distortion, avoidance of triaxial stresses, and other somewhat tricky factors.

On top of this it's difficult to weld in comparison with steel; it's hard to get good fusion at the same time as minimal distortion and porosity. At least, it's hard to do that consistently.
Welds which look good can be crappy, whereas in steel that is not usually true.
Welding equipment is considerably more expensive than for steel. (Having just had to replace mine, it hurts)

Aluminium is certainly softer and less abrasion resistant than steel. However it's still a lot more abrasion resistant than fibreglass or wood.

It can burn in a fire, given sufficiently intense heat. Steel is (for all marine purposes) fireproof.

Against this it's a delight to cut and shape, in comparison to steel; it's more like wood in speed and ease of sawing and planing (except the shavings are much less friendly).

The scrap value is much higher than steel, which helps offset a bit of the added material cost. Actually I think it's one of the better value marine materials, all things considered, presuming the welding expenses can be spread over a number of builds.

The diminished corrosion difficulties of aluminium vs steel (to my way of thinking) tip the balance, particularly for unpainted hulls, to where the good points outweigh the bad. Neither metal will cope as well with neglect as a heavily built fibreglass boat, but aluminium will cope a lot better than wood.

[ozskipper]

Old Aluminium that hasnt been cared for by previous owners. Sad for Nike ( her name not her shoes)

UNTIE THE LINES #24 - A Bottomless Pit - YouTube

[Dulcesuenos]

Had an aluminum boat and never again. It was a 25' sea arc ram commander new cost 6 figures at 5 years old was a POS from welds falling apart and holes from current?Talked to owners of a newer aluminum 40' mono at a yard and it was wearing them out w zincs, paint and corrosion. Aluminum +salt water,, no way. People have a hard enough time protecting saildrives long term now you want an entire boat made out of it.....

Sent from my LG-LS980 using Cruisers Sailing Forum mobile app

[carstenb]

Originally Posted by Stu Jackson

Is that like dinch or lunner?

Something like that. I need soothing to brace myself before I take a sunrise sight with my sextant. Same for the noonsite and the sunset site. In between, I need a bracer to help with the math.

Life's really tough when you're cruiser

[goboatingnow]

Originally Posted by ozskipper

Old Aluminium that hasnt been cared for by previous owners. Sad for Nike ( her name not her shoes)

Jesus I'm depressed after that , what a sad video

Dave

[atoll]

another one for the wannabees thread, ...........

my advice, rip out all the dodgy electrical installation that caused the problem in the first place,cut out the bad bits and weld in new plates over the affected areas.

if she only paid $5000 dollars for the boat,i have no sympathy over $5000 worth of repairs......you pays your penny ,you takes your ride............

[goboatingnow]

Originally Posted by atoll

another one for the wannabees thread, ...........



my advice, rip out all the dodgy electrical installation that caused the problem in the first place,cut out the bad bits and weld in new plates over the affected areas.



if she only paid $5000 dollars for the boat,i have no sympathy over $5000 worth of repairs......you pays your penny ,you takes your ride............

Ah Jesus atoll , have a heart. The boats f€&ked, other then burning it , repairing its a waste of time.

Dave

[atoll]

Originally Posted by goboatingnow

Ah Jesus atoll , have a heart. The boats f€&ked, other then burning it , repairing its a waste of time.

Dave

i haven't watched all the vids but it is hardly f***ed,the beauty of metal is you can cut out the bad bits and replace them,i live on a 63 ft alloy boat so know a litte bit about it.

it might be a bit of a set back,but repairing is far cheaper than replacing.

[goboatingnow]

Originally Posted by atoll

i haven't watched all the vids but it is hardly f***ed,the beauty of metal is you can cut out the bad bits and replace them,i live on a 63 ft alloy boat so know a litte bit about it.



it might be a bit of a set back,but repairing is far cheaper than replacing.

Atoll the whole bottom of that boat is compromised. Potentially the diesel tanks are compromised. The materials and labour are more then the boats worth. The whole bottom needs replating .

She bought a POS.

Dave