capnsensible
Well-known member
You haven't convinced me that aluminium is not the major material in use in passenger airframes.
I'll try and get a picture of the rivets on the two planes I'll be a passenger on tomorrow.
Are aluminium boats a liability?
- Thread starter geem
- Start date
I'll try and get a picture of the rivets on the two planes I'll be a passenger on tomorrow.
westernman
Well-known member
capnsensible
Well-known member
Carbon fibre reinforced plastic. A very expensive, light and strong material used in the production of some parts of passenger jets.
Glass reinforced plastic. A cheap ish, strong material used in constructing many leisure and commercial small craft. Not jets.
That's it in black and white.
And I got absolutely no idea why I'm having an argument about two completely different materials to the op observations on aluminium....
Glass reinforced plastic. A cheap ish, strong material used in constructing many leisure and commercial small craft. Not jets.
That's it in black and white.
And I got absolutely no idea why I'm having an argument about two completely different materials to the op observations on aluminium....
ean_p
Well-known member
The problem with that drop test is that we don't know how 'captive' the weight was at the bottom of its drop nor how far the deflection of the material was arrested and limited. See the brick shaped object below the test panels. I would suggest that the grp would have flexed enough to contact that brick and hence been subjected to a crush at that point rather than a penetration whereas the aluminium wouldn't flex that much and would then pierce through as it did. The reverse of the GRP certainly looks 'crushed'. This may also be assisted by the weight not been able to fall right through the bottom but having a 'stop' roughly at the same level as the brick upper surface. I may go on to think that fully unrestrained then that weight may have passed right through the grp, but only the testers would know the reality of that.
Supertramp
Well-known member
I don't think this is about the strength of the material - metal hulls behave differently to plastic in impacts.
This is more about quality of build and quality of subsequent modifications and maintenance. Especially where different metals meet. If its "fizzing" then something went wrong. And the same would apply to a GRP boat's anodes and metalwork.
Separately, and its not directly relevant, I bought one of the first aluminium cycle frames in the UK 40 years ago and rode over 30000 miles on it. It is now retired and hangs on my shed, a few dings and flaky paint but sound. For the last decade I have ridden an all carbon fibre frame. I somehow think the carbon fibre frame will not last as well (though it is lighter).
This is more about quality of build and quality of subsequent modifications and maintenance. Especially where different metals meet. If its "fizzing" then something went wrong. And the same would apply to a GRP boat's anodes and metalwork.
Separately, and its not directly relevant, I bought one of the first aluminium cycle frames in the UK 40 years ago and rode over 30000 miles on it. It is now retired and hangs on my shed, a few dings and flaky paint but sound. For the last decade I have ridden an all carbon fibre frame. I somehow think the carbon fibre frame will not last as well (though it is lighter).
boomerangben
Well-known member
If I remember tomorrow, I’ll get some photos of the GRP section of an S92 helicopter which has fake rivets moulded into to make it look like the rest of the aircraft. I am not joking
capnsensible
Well-known member
Neat.The S-92 is multi-purpose helicopter powered by twin GE CT7-8A turboshaft engines and has an aluminum airframe and some composite components
William_H
Well-known member
Just as a matter of interest carbon fibre aircarft components are made from what is called "prepreg" Here carbon fibre woven cloth is impregnated with epoxy resin (with hardener in a tightly controlled roller arrangement. The roll of impregnated CF is immediately cooled down so it won't harden. It is shipped in refrigerated containers. After being cut out and placed in mold it is covered with an absorbent sacrificial cloth then cooked under pressure in an autoclave. The result is a highly repeatable and correct ratio of resin to CF giving best strength to weight.
As for aluminium boats. We have a ship building industry Austal austal shipyard - Yahoo Search Results specialising in aluminium power boats often catamaran in the 200+ft size. Used both for ferries and military use including selling to US navy. Apparently ali is good. Although I think for us humble yachties GRP is just the very best. ol'will
As for aluminium boats. We have a ship building industry Austal austal shipyard - Yahoo Search Results specialising in aluminium power boats often catamaran in the 200+ft size. Used both for ferries and military use including selling to US navy. Apparently ali is good. Although I think for us humble yachties GRP is just the very best. ol'will
westernman
Well-known member
May be aluminium wins for one off designs?
One off in GRP for Carbon Fibre reinforced plastic is more difficult to build and probably more expensive in both labour and material cost.
Buck Turgidson
Well-known member
You are jumping the gun a bit.
Aluminium is still used more than CFRP for fuselages. Aluminium lithium alloy is most common. But yes, the 2 models you quoted do use CRFP for most of the fuselage.
Tranona
Well-known member
Not just one offs but low volume semi custom and even series production like the Ovnis. Very few one offs are built using GRP or similar composites although epoxy/wood is probably more common. as already noted aluminium is widely used for fast ferries, some built in UK but probably more in Australia and China.
westernman
Well-known member
Only for older generation airplanes - or revamps of old airplanes such as the 737 Max (very old in that case). Even the 777X uses a lot of CFRP in its wings now.
Even the A220 uses a lot of composites.
Buck Turgidson
Well-known member
A220 fuselage is Al-Li. I've been all over them in the factory and was in the sim earlier today ;-)
westernman
Well-known member
The wings are plastic.
Neeves
Well-known member
Returning to sailing
Pacha seems to prove that it is quite possible to build long lasting, beautiful and performance yachts.....
from aluminium
The hull its metal, not plastic
Pacha Sailing
Jonathan
PS, her anodes are the size of generous dinner plates.
Pacha seems to prove that it is quite possible to build long lasting, beautiful and performance yachts.....
from aluminium
The hull its metal, not plastic
Pacha Sailing
Jonathan
PS, her anodes are the size of generous dinner plates.
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Boater Sam
Well-known member
Practically all Sea Otter aluminium Canal boats will never see salt water for prolonged periods if at all.
Kelpie
Well-known member
At the fish farm where I used to work, we had a small aluminium workboat that was still going strong after 30yrs. And those boats are not in any way pampered! But it was very simple, with just an outboard, nav lights, and a VHF. So I don't think aluminium is inherently unsuitable for seawater use. Trouble presumably arises from stray electrical currents and dissimilar metals corrosion which must get harder and harder to avoid add the boat gets bigger and more complex.
geem
Well-known member
That's my thought but modern boats are getting a lot more complicated. Electric toilets, winches, window blinds, underwater lights, aircon, washing machines, dryers, multiple fridges, inverters, are increasingly options or standard equipment on lots of new boats. The amount of wiring being installed and the potential for an earth fault is there. If superyachts can't control the problem with their unlimited budgets how can budget orientated aluminium production boats hope to succeed. Add in a bit of owner diy wiring and you are on the way to a fizzing boat
Tranona
Well-known member
If superyachts can't control the problem with their unlimited budgets how can budget orientated aluminium production boats hope to succeed. Add in a bit of owner diy wiring and you are on the way to a fizzing boat
But there are few series production aluminium sailing yachts except the Ovni and Alubat as the properties of the material do not make it suitable for volume production and the downsides identified here make buyers wary of them except in very limited markets.
Superyachts, whatever the hull construction material require constant maintenance of the systems - even when they don't go anywhere so looking after the aluminium is just another job - doubt it takes any more time and effort than keeping the teak looking pristine!
mullet
Active member
I crewed on a >150’ aluminium super yacht. Only 4 years afloat at that stage but no problems. That said, we were very careful indeed about isolating any dissimilar metals, and a diver was down and checking anodes pretty much fortnightly.
Have to admit being more concerned about the likely effects of a lightning strike when sailing through an electrical storm though.
OTOH We we’re once berthed alongside a big steel Feadship that almost sank at its berth. The engineer poked a soft patch of the hull in the engine room with his finger and it went straight through. Much older boat though. Swings, roundabouts etc.
Have to admit being more concerned about the likely effects of a lightning strike when sailing through an electrical storm though.
OTOH We we’re once berthed alongside a big steel Feadship that almost sank at its berth. The engineer poked a soft patch of the hull in the engine room with his finger and it went straight through. Much older boat though. Swings, roundabouts etc.
