Aluminium hull thoughts

[Mr Googler]

Thinking about a project boat. 1970’s aluminium hull and superstructure. Very unloved. Renault diesel engines (new one to me that)

Aluminium at that age feels scary but how bad is it? Anyone got experience of older Ali boats? Galvanic corrosion the obvious factor and difficulties of repair. Not sure many surveyors will be up to speed?

thoughts welcome

 

[Bajansailor]

Can you supply some more info please about this ally project boat?
Do you have any photos?
The cat in my avatar photo is a mere youngster at 24 years old now, but she is still going strong, and I would hope that with sensible maintenance she will also see her 50th birthday (assuming the operators don't do something silly in the meantime).

They did have one interesting problem recently - she takes passengers on snorkelling expeditions along the coast here.
The plastic hatches in the deck (for access in to the hulls) were original, and leaking slightly, and the wet snorkellers would drip sea water on deck, some of which would leak past the hatch seals, and drip on the (marine grade) aluminium hull bottom plate.
The water droplets would then evaporate, leaving a salt residue, and over time this residue would get wider.
And this local concentration of salt resulted in pitting corrosion occurring under the salt - the hull bottom plating is 6 mm thick, and there was one pit that went all the way through (resulting in a leak, which alerted the owners to the fact that they had a problem).
There were a few other pits that were about 3 mm deep, and some others that were about 1 - 2 mm deep.
The worse pits were cropped out, and new plate was welded in fairly easily - by the same welders at Structural Systems who built the boat in 2000. .

The original owners never had this problem (although they also had leaky hatches), as they did clean out the bilges fairly regularly, but when the boat was sold to new operators they did not carry on with this tradition.
So this was a unique lesson learned, albeit the hard way.

There are also various stories doing the rounds of copper coins that have been inadvertently dropped in the bilges of aluminium boats eating their way through the bottom shell plating - when I saw the neat hole that was created just by local salt deposits on the aluminium, I am sure that this can happen.

 

[Greg2]

We have an aluminium hulled cat at work that is reaching the end of its working life with us as we have a new build GRP boat about to be delivered. The aluminium boat is well built but also very well maintained and I have no doubt it will go on for many years to come.

My concern would be similar to s steel boat i.e. what is going on in areas you simply can’t access or see. Not a show stopper but important to do as much due diligence as you can and the word ‘unloved’ does serve to emphasis the importance of this.

You are probably right about surveyors who deal mainly with recreational boats not being too familiar with aluminium but there are plenty who deal with commercial workboats who will know a lot more so it might be worth finding one who will do a survey for you.
.

 

[Mr Googler]

Thanks both

same (but not actual) boat. Striker 44 For Sale, 12.78m, 1974

Having a look over the weekend. If the bilges are dry I’d be amazed. I’ve been researching and even a few strands of copper wire in the bilge can get the corrosion going. She’s been stood for many years, rarely lifted out and one engine is in bits currently. I am wondering if her value at this point is in scrap only.

 

[jfm]

I'd be very happy with an aluminium boat in principle. My brother just bought an aluminium boat. 2014 build and 8mm hull plating, in class. You can quickly see the inside of the hull with your own eyes and if the original paint (ideally white) looks perfect then you have some initial confidence. If not, welded repairs can be done perfectly, but of course costs can rise quickly.

There are surveyors with strong focus on metal. I tend to ask Derek Levy (UK and SofF based, but he covers Italy) because he really knows his onions with aluminium as well as GRP and I like him.

 

[PaulRainbow]

Thanks both

same (but not actual) boat. Striker 44 For Sale, 12.78m, 1974

Having a look over the weekend. If the bilges are dry I’d be amazed. I’ve been researching and even a few strands of copper wire in the bilge can get the corrosion going. She’s been stood for many years, rarely lifted out and one engine is in bits currently. I am wondering if her value at this point is in scrap only.

I'd be more concerned about the engine than the ally.

 

[Mr Googler]

I'd be more concerned about the engine than the ally.

Agreed…..1970’s Renault truck engines with ”marine” bolt on’s……mmmmm

 

[PaulRainbow]

Agreed…..1970’s Renault truck engines with ”marine” bolt on’s……mmmmm

Just guessing here, i'm sure you'll do your own research, but the marine bits might be hard to find.

Renault engines might make it a hard sell ?

 

[Bajansailor]

Striker aluminium boats have a good reputation generally - there are two Striker sportsfishermen here, both built in the 70's, and impeccably maintained.
They both have GM diesels though, rather than Renault.
That seems strange, re how both Mr Googler's project boat and the boat in the advert he linked to have Renault diesels.

@Mr Googler please do update us with your findings after you have a look at your project boat this weekend.

 

[Mr Googler]

Just guessing here, i'm sure you'll do your own research, but the marine bits might be hard to find.

Renault engines might make it a hard sell ?

Agreed

 

[Mr Googler]

Striker aluminium boats have a good reputation generally - there are two Striker sportsfishermen here, both built in the 70's, and impeccably maintained.
They both have GM diesels though, rather than Renault.
That seems strange, re how both Mr Googler's project boat and the boat in the advert he linked to have Renault diesels.

@Mr Googler please do update us with your findings after you have a look at your project boat this weekend.

Will do! I’ll take photos

 

[SC35]

Given all the problems with boats in general, I personally prefer a hull that isn't slowly dissolving in water.
But that is purely a personal preference.

 

[Bajansailor]

Given all the problems with boats in general, I personally prefer a hull that isn't slowly dissolving in water.

It will only do so if you allow it to - such as not replacing the anodes when they are consumed, or parking it in close proximity to something big, strong and cathodic.
Fibreglass boats can get osmosis, steel boats can rust from the inside out, wooden boats can rot...... there is no 'perfect' hull material, but I reckon that aluminium comes pretty close, and especially so for a one off custom design.

 

[PEJ]

I'd be very happy with an aluminium boat in principle. My brother just bought an aluminium boat. 2014 build and 8mm hull plating, in class. You can quickly see the inside of the hull with your own eyes and if the original paint (ideally white) looks perfect then you have some initial confidence. If not, welded repairs can be done perfectly, but of course costs can rise quickly.

There are surveyors with strong focus on metal. I tend to ask Derek Levy (UK and SofF based, but he covers Italy) because he really knows his onions with aluminium as well as GRP and I like him.

I, too, have an aluminium hulled boat. 72ft long 1996 vintage. You need to be very diligent about what gets in the bilges and inspect often. I had a thorough ultrasound survey done before I bought it to check the thickness all over. As JFM says I can see white paint intact everywhere. No need to polish gel coat every year and easy to keep looking good provided you keep washing it regularly.

 

[Seastoke]

Thinking about a project boat. 1970’s aluminium hull and superstructure. Very unloved. Renault diesel engines (new one to me that)

Aluminium at that age feels scary but how bad is it? Anyone got experience of older Ali boats? Galvanic corrosion the obvious factor and difficulties of repair. Not sure many surveyors will be up to speed?

thoughts welcome

Won’t it look like destroyer after you have wrapped it in Grey.

 

[stelican]

I, too, have an aluminium hulled boat. 72ft long 1996 vintage. You need to be very diligent about what gets in the bilges and inspect often. I had a thorough ultrasound survey done before I bought it to check the thickness all over. As JFM says I can see white paint intact everywhere. No need to polish gel coat every year and easy to keep looking good provided you keep washing it regularly.

Just looking at your Avatar, Is it a Dutch boat you have now.
Looks interesting.

 

[Mr Googler]

Just looking at your Avatar is it a Dutch boat you have now.
Looks interesting.

2nd that! More info please….looks stunning!

 

[Assassin]

First iissue is that they are NOT Renault engines and they are Saviem engines which are generally decent engines if maintained and their add on pieces will ne generic units adapted to fit and an adaptor may be needed to fot the oil cooler such as a step down adaptor from the engine to the cooler as the engine threads are metric and the cooler BSP threads.

No problem is unsurmountable but the availability may be an issue so tread carefully as latterly Renault changed from holding a small stake in Saviem to buying a controlling interest.

 

[Mr Googler]

First iissue is that they are NOT Renault engines and they are Saviem engines which are generally decent engines if maintained and their add on pieces will ne generic units adapted to fit and an adaptor may be needed to fot the oil cooler such as a step down adaptor from the engine to the cooler as the engine threads are metric and the cooler BSP threads.

No problem is unsurmountable but the availability may be an issue so tread carefully as latterly Renault changed from holding a small stake in Saviem to buying a controlling interest.

Interesting. I figured they would be Renault couch from a bit of googling. Decided not for me, didn’t even look. The more questions I asked, the worse it got . Thank you to everyone who commented and was interesting to research and learn more as ever