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Old 20 October 2004, 15:43   #1
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Aliminium vs steel in A-frame ?

Why is almost all european A-frames made of steel, and not aliminium ?
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Old 20 October 2004, 15:50   #2
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Steel is hard, alu is softer.
Its pretty hard strain when you jumping in waves etc and to get alu as durable/lasting as SS it has to be very thick and then it will be more expensive than SS

Specially in the Sweden were SS has high quality and not that expensive for what you get.
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Old 20 October 2004, 15:53   #3
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Funnily enough I think most ofd the Mil spec boats have Alu frames/ Avon seariders have an Ali option and I think pacific's are Alu
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Old 20 October 2004, 15:58   #4
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Quote:
Originally Posted by Petrov
Steel is hard, alu is softer.
Its pretty hard strain when you jumping in waves etc and to get alu as durable/lasting as SS it has to be very thick and then it will probably be more expensive than SS
I,have cracked my steel-frame several times, The local police Goldfish rib has a reinforced one off, several small cracks, another local charter rib has dismounted it because it has cracked several times.
Talked to a guy with a Hurricane with ali-frame, no cracks yet.

Want to build a one off for my eventually new boat, and i want it to last this time. Cost no big issue.
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Old 20 October 2004, 16:04   #5
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Quote:
I,have cracked my steel-frame several times, The local police Goldfish rib has a reinforced one off, several small cracks, another local charter rib has dismounted it because it has cracked several times.
I only heard of one frame that got a small crack on the boats i have bought and it started on a spot were it was made a welding so it was more of a bad work than the material.

If you have a well known company that is really good in welding and SS i dont think you will have the problem.
Just make sure that you dont under dimension the frame (have seen that a lot of manufacturers can do that some times)
I have no experience of alu frames.
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Old 20 October 2004, 16:09   #6
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Over the years Stainless becomes brittle.
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Old 20 October 2004, 16:18   #7
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Over the years Stainless becomes brittle.
And Alu?
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Old 20 October 2004, 16:18   #8
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Alloy is ideal BUT the tubes will need to be of greater diameter - also the strongest alloys aren't the most corrosion resistant hence the need for good coatings or anodising. Should the coating fail you will have probs.

Having said that there are plenty of examples where alloy is used - mountain bike frames - tent poles - ice axe shafts - airframes etc etc.
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Old 20 October 2004, 16:22   #9
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Quote:
Originally Posted by Petrov
And Alu?
Not so quickly and it has a little more resilience. I believe that Alu tanks are standard for raceboats (as opposed to stainless steel) because they have less tendancy to crack
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Old 20 October 2004, 16:53   #10
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The original ss fueltank in my present rib cracked where the "chamber walls" ( Dont know the word for skvalpe-skott in english ) was welded. The tank was 6 years old. Got a new one from a local blacksmith in ss. told him to make it very sturdy, no expence spared. Took it for a test drive to Skagen. Discovered gas in the bottom of the boat before we got half the way. Same prob again. I now have a tank in 3 mm ali made by proffessionals, and no leaks yet. Goldfish, known to make very fast ribs use ali-tanks.

I,m quite shure ali is the best material, wether its for tanks or A-frames. Just cant figure out why so few manufactures are using it.
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