Sealium....One for Jay Perotta and other plate alloy afficianado's

[trouty]

Seems them Frogs over at French Aluminium maker Pechini MArine have launched their latest Marine Alloy product Sealium, which has been devekloped as an offshoot of advances in the aerospace industry.

This new Marine Alloy is designated 5383 and has several advantages over the standard 5083 alloy according to Pechiney.

In a nutshell an all sealium built vessel will gain an full 16% strength gain over the standard existing marine alloys, which results in a 8% reduction in plate thickness and 26% scantlings difference over vessels constructed with the more common 5083 & 6082 alloys

Weight total savings over a common hull style are expected to be in the order of 3.8 - 10%.

New designed sealium extrusions for marine vessel manufacture will result in a further weight reduction in vessel coonstruction - havng much better torsional flexing resistance than standard extrusions and being beefed up in areas to accomodate welding requirements of the sealium alloy.

They have also developed a new filler wire for welding sealium and in addition to that a new welding technique called FSW Friction Stir welding, for alloys that were formerly considered unweldable.

One other interesting development is a 'new' stretchforming process for these alloy plates, where a "mould is stictched together from CNC produced stringers and frames for compound convex bow flare for example...

This mould is set inside a tank - the plate is precisely positioned and then affixed with special controlled explosive plates - the tank filled with water and a controlled detonation forms the plate to the desired curvature of the mould...

Plates then removed and welded into place on vessel...

It would seem that there IS an engineering solution to just about everything these days...and I remain pretty confident that eventually alloys of aluminium will replace firbeglass and kevlar etc as premium hull material choices as cheaper methods and additional strength weight and corrosion resistance advances are made in materials engineering...and manufacturing processes.

Fascinating things happening in big boat building in alloy, with benefits that will no doubt one day flow down to recreational vessel manufacturers like Pacific and Jays Blacklab marine business no doubt.

You could get all the details Jay in "Speed at Sea's" Oct 2003 Magazine - very interesting reading for fella's like us interested in alloy boats manufacture!!

Now blowin things up is something I'm emminently qualified for so finally there MAY be a decent opening for moir in the Marine alloy boat manufacturing industry!!!!

Fire in the hole!!!!

Cheers!

[blacklabmarine]

Hi Trouty,

I think that Sealium was a mid 90's creation by your friends over in France - another cool alloy is the 5059 Alustar from Germany - neither, to my knowledge, has found widespred acceptance in US ship building circles but then we're behind on aluminum alloy use in general as you and I have often discussed!

Explosive forming began back in the 40's and I believe that a few folks I know have looked onto it with regards to shipbuilding. Pretty expensive. Used a lot in aerospace - see nozzles for rockets, etc.

Water forming (pressure) and stretchforming both have interested me for a long, long time. Quintrex uses stretchforming on their sheet metal boats in Australia and Tracker uses some water forming on their thin-skinned freshwater boats.

I recently talked to a US company that does stretch forming of up to 5/8" material - didn't go very far during the call but in the future I believe that we'll be able to give folks a "Carolina" flare in a plate alloy boat.

Have you seen the new US Army support vessels? Built in the US bit with some sort of agreement with Incat from Tasmania - second such alloy vessel to be bought and put in service...

[skypoke]

Trouty and Jay,

And to further complicate matters, when I was purchasing the 5083 for my cat I found that Hogal/5518 was an updated version of the 5083 which offers a significantly greater as welded strength when used with 5183 wire, which we're using. My take on it though now that it's welded up is that the boat is ridiculously strong and rigid for a small craft. No comparison to the glass I'm used to.

Incat was looking for a southern US location to set up shop to build these fast craft and Corpus Christi was in the running for this as were sites in La and Alabama. Have you heard if they've decided on a location? An interesting aside was that these boats created a political stink because they require such a small crew to complete their mission compared to ships like the Inchon which they will replace!

Chuck

[skypoke]

Just pulled the mill certs on the mtl we're using, this from Corus:

5083/HOGAL5518 equivalent to properties of alloy 5383. Certified in addition to MJ-5383 by ABS.

Only achieves the higher strength when welded with 5183, not 5356.

Chuck