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What's the downside to aluminium?


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1 minute ago, max campbell said:

Apart from the price! Is there a technical reason Sea Otter only built small boats? Do they corrode at all?

 

They made some quite large boats too, 50 odd footers I think.

 

There is no technical reason why aluminium cannot be used for big boats, its just a question of metal gauge and proper welding.

 

Originally Sea Otter made trailable boats, hence they were smaller and lighter using water as ballast. Later they made boats far too big to be trailered.

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4 minutes ago, max campbell said:

Apart from the price! Is there a technical reason Sea Otter only built small boats? Do they corrode at all?

 

They didnt, there are long ones too.

The shorter ones were more popular as they were trailable.

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Wasn't one of the Warships lost in the Falklands War made of aluminum????

 

A problem is that its soft so dents easily, whenever we pass close to one the owners run out and deploy fenders ?

 

............Dave

 

 

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7 minutes ago, dmr said:

Wasn't one of the Warships lost in the Falklands War made of aluminum????

 

A problem is that its soft so dents easily, whenever we pass close to one the owners run out and deploy fenders ?

 

............Dave

 

 

 

HMS Sheffield.

 

Edit - except checking my recollection with Google says this is not correct.

Edited by The Happy Nomad
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10 minutes ago, The Happy Nomad said:

 

HMS Sheffield.

 

Edit - except checking my recollection with Google says this is not correct.


You wouldn’t name a ship made of aluminium after a city famous for it’s steel.

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2 minutes ago, Captain Pegg said:


You wouldn’t name a ship made of aluminium after a city famous for it’s steel.

 

I can rember the day it was hit. Its one of those situations that you can remember exactly where you were when you see or hear news.

 

I also recall the speculation afterwards about why the fire was so severe and lethal ie she was predominantly constructed from alluminium. Unsurprisingly the media were wrong.............again.

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High speed ferries are made from Aluminium. The largest example being the Stena HSS ferries which were over 400ft long!  

The downsides are it is expensive and it is not as easy to weld as steel.  

Edited by booke23
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13 minutes ago, The Happy Nomad said:

 

I can rember the day it was hit. Its one of those situations that you can remember exactly where you were when you see or hear news.

 

I also recall the speculation afterwards about why the fire was so severe and lethal ie she was predominantly constructed from alluminium. Unsurprisingly the media were wrong.............again.

 

However research and tests following 9/11 suggests that the fires in the Twin Towers were incredibly intense because the airliners (predominantly constructed of aluminium) involved burnt like magnesium, with burning molten aluminium dribbling from one floor down to the next.

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40 minutes ago, dmr said:

Wasn't one of the Warships lost in the Falklands War made of aluminum????

 

A problem is that its soft so dents easily, whenever we pass close to one the owners run out and deploy fenders ?

 

............Dave

 

 

I have heard folk saying that Sea Otters dent easily but we haven't found that in the 20 odd years we have owned gamebird. 

 

haggis

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1 minute ago, Murflynn said:

 

However research and tests following 9/11 suggests that the fires in the Twin Towers were incredibly intense because the airliners (predominantly constructed of aluminium) involved burnt like magnesium, with burning molten aluminium dribbling from one floor down to the next.

It was, the presence of water from the roof tanks also added to the burning of the alloy, it added oxygen to the mix and hydrogen as the water broke down.

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4 minutes ago, Murflynn said:

 

However research and tests following 9/11 suggests that the fires in the Twin Towers were incredibly intense because the airliners (predominantly constructed of aluminium) involved burnt like magnesium, with burning molten aluminium dribbling from one floor down to the next.

 

They were wrong because HMS Sheffield wasnt predominately made of alluminium she was predominately of steel.

 

Not because alluminium doesnt burn easier or more intensely than steel.

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The Type 21s lost,  HM Ships Antelope and Ardent,  were,  like the rest of the class constructed with an aluminium superstructure explosively bonded to steel hulls. The superstructures burned  after being hit by bombs, but the hulls did not.

 

N

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I had a go with a sledgehammer on a piece of their 'aluminium' at a Sea Otter trade stand, couldn't even mark it, very tough, aluminium conjures up images of soft pliable metal, couldn't be further from the truth, it's marine alloy. 

They offered to build me a 60' nb shell by constructing it diagonally across their workshop (too expensive - £30k in 2003) reckoned they could just squeeze it in, so maybe that's why they didn't build them any longer?

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Having been involved in competitive archery years ago arrows were aluminium, but a very hard stiff brittle aluminium, I do not know what alloy was used, probably a carefully guarded secret. If you missed the target and hit a brick wall the arrow did not bend but shattered with crystalline fracture faces. Taught me that not all aluminium alloys behave like aluminium.

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2 hours ago, haggis said:

I have heard folk saying that Sea Otters dent easily but we haven't found that in the 20 odd years we have owned gamebird. 

 

haggis

I agree. In the 1980's  was involved in the salvage of a small passenger vessel constructed totally from aluminium,  which was taken to Djibouti after running aground on extensive reefs on the Horn of Africa.. After temporary repairs to the bottom, which was extensively damaged I towed her from Djibouti to Singapore via Columbo - around 3000 miles - which she survived with no issues,  and she was eventually repaired. She certainly "dented" but that was no real problem and she was built like the proverbial "brick pagoda". Rather the difficulty in repairing her was in the shipyard in Djibouti being able to weld aluminium which is not as straightforward as steel.

 

Many ships over the years have been fitted with aluminium superstructures including the very large passenger vessel "United States" built in the 1950's in the US, which held the Blue Riband for many years as the fastest passenger liner on the Atlantic. I am sure the lightweight of the Aluminium superstructure contributed to her high speed.  She is still afloat although has not been in service for many years. 

 

However, I think one of the main arguments against a wider use of Aluminium for larger vessels is the greater cost of materials, coupled with the increased difficulty in repairing and modifying the structure. which can be quite prohibitive.

 

Howard

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4 hours ago, dmr said:

Wasn't one of the Warships lost in the Falklands War made of aluminum????

 

A problem is that its soft so dents easily, whenever we pass close to one the owners run out and deploy fenders ?

 

............Dave

 

 

 

I'm not sure why they'd need to do that? All the Sea Otters I've seen have a continuous large D section rubber fender fitted all the way around.

 

As I understand it though, the fenders were primarily to prevent wear rather than denting.

 

The other thing to be aware of if you own am aluminum boat fitted with AC mains, is that it's imperative you have some form of galvanic isolation on the mains earth path of you intend to plug into shore power. 

 

That's not a downside as long as the hull is isolated.

Edited by blackrose
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6 hours ago, blackrose said:

 

The other thing to be aware of if you own am aluminum boat fitted with AC mains, is that it's imperative you have some form of galvanic isolation on the mains earth path of you intend to plug into shore power. 

 

That's not a downside as long as the hull is isolated.

 

its a major plus if you own a steel boat with no galvanic isolation and moored next door to an aluminium boat - its on giant anode ?

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7 hours ago, howardang said:

I agree. In the 1980's  was involved in the salvage of a small passenger vessel constructed totally from aluminium,  which was taken to Djibouti after running aground on extensive reefs on the Horn of Africa.. After temporary repairs to the bottom, which was extensively damaged I towed her from Djibouti to Singapore via Columbo - around 3000 miles - which she survived with no issues,  and she was eventually repaired. She certainly "dented" but that was no real problem and she was built like the proverbial "brick pagoda". Rather the difficulty in repairing her was in the shipyard in Djibouti being able to weld aluminium which is not as straightforward as steel.

 

Many ships over the years have been fitted with aluminium superstructures including the very large passenger vessel "United States" built in the 1950's in the US, which held the Blue Riband for many years as the fastest passenger liner on the Atlantic. I am sure the lightweight of the Aluminium superstructure contributed to her high speed.  She is still afloat although has not been in service for many years. 

 

However, I think one of the main arguments against a wider use of Aluminium for larger vessels is the greater cost of materials, coupled with the increased difficulty in repairing and modifying the structure. which can be quite prohibitive.

 

Howard

I believe QE2 had an aluminium superstructure? 

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53 minutes ago, Tony Brooks said:

 

its a major plus if you own a steel boat with no galvanic isolation and moored next door to an aluminium boat - its on giant anode ?

 

It may be interesting to potential Alumininium boat owners that Aluminium is actually used as an anode for 'brackish' waters (typically in estuaries or tidal rivers where fresh and salt water mix).

 

Aluminium alloy is even further down the Galvanic scale than pure Aluminium, so if there is a problem with Galvanic corrosion the hull will be 'eaten' away before your steel shaft or bronze / brass prop are affected.

 

As has been said, maximum protection is of the absolute importance to an Aluminium / Aluminium alloy boat.

 

 

If you have an outboard or outdrive with an Aluminium prop, make sure you never moor up and share an electrical supply with a steel boat, or a boat with a bronze prop.

 

 

 

Galvanic Order of Metals A - C 2.jpg

 

 

 

 

Galvanic Corrosion.gif

Edited by Alan de Enfield
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12 hours ago, Tracy D'arth said:

I have not seen any with any appreciable corrosion. They do burn or at least melt down to the water line when set on fire though unfortunately.

Yes they do and this is what happened to one at BraunstonP1060218.jpg.af75b2f5d215ed864ed30b2697902879.jpg

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1 hour ago, nb Innisfree said:

I believe QE2 had an aluminium superstructure? 

That's right - a large proportion of her superstructure was Aluminium, mainly for weight saving reasons.

 

Howard

Edited by howardang
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