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Old 19 June 2005, 20:22   #11
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Quote:
Originally Posted by codprawn
Which is why aluminium is the preffered choice for a really heavy duty rib hull.

I presume you mean aluminium alloys since aluminium is particularly malleable and ductile.

Perhaps your preferred choice. Laminate up a cylinder. Roll up an aluminium cylinder the same diameter and wall thickness. Now hit them with a hammer. Come back and tell us your findings.

Cod, you do often appear to believe things to be true rather than know them to be true.
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Old 19 June 2005, 22:18   #12
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Quote:
Originally Posted by jwalker
I presume you mean aluminium alloys since aluminium is particularly malleable and ductile.

Perhaps your preferred choice. Laminate up a cylinder. Roll up an aluminium cylinder the same diameter and wall thickness. Now hit them with a hammer. Come back and tell us your findings.

Cod, you do often appear to believe things to be true rather than know them to be true.
So why do heavy duty workboats have steel or aluminium hulls????
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Old 20 June 2005, 03:50   #13
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Originally Posted by martini
The hull shape and tubes remind me very much of a ribtec. white hull and that blue on the tubes is very ribtec as well!
I totaly agree i think it is also a Ribtec with the bow curling up like that.
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Old 20 June 2005, 03:54   #14
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Quote:
Originally Posted by codprawn
Which is why aluminium is the preffered choice for a really heavy duty rib hull.
what a bit like Halmatics then ?

Its not a Ribtec although the tubes look similar so presumably it was tubed by Henshaws. Early Cobras had stringers laminated into the inside of the bow area that could be seen above the decks but this doesn't seem to have them. Hmm a mistery, perhaps someone should ask the vendor.

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Old 20 June 2005, 05:41   #15
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That Yammie v4 will be a thirsty beast (i know, i used to have one)
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Old 20 June 2005, 07:50   #16
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That Yammie v4 will be a thirsty beast (i know, i used to have one)
Yeh and didn't she go well with it strapped to the back .
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Old 20 June 2005, 11:41   #17
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Same boat but tells you the maker http://ribs.apolloduck.co.uk/display.phtml?aid=28049 wich is Picton Boats wich is cobra i think.

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Old 20 June 2005, 12:24   #18
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Quote:
Originally Posted by jwalker
Not once it's encapsulated in resin. It delaminates easily on impact. It has good stretch resistance and tensile strength which makes for rigidity.
But then thats the same for all PMCs. With regards to material properties, the matrix system (in this case epoxy or perhaps polyester resin) dominates the delamination properties, not the reinforcement (unless you have a system of through stitching). Aramid has high specific strength, low compressive strength (ie it buckles easily) but has high toughness, therefore a composite made up of aramid and epoxy is much better at resisting impacts than a carbon composite (carbon has high stiffness but low toughness).

Glass is just generally pants
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Old 20 June 2005, 14:03   #19
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Slimtim, I got the impression you were justifying it's use in boat construction by comparing it's energy absorption properties in such things as anti-flack jackets.

Quote:
Originally Posted by slimtim
...the matrix system (in this case epoxy or perhaps polyester resin) dominates the delamination properties, not the reinforcement (unless you have a system of through stitching).
Yeh, I suppose that is generally the case but if the reinforcement material is hairy in texture there will be considerable reinforcement across the resin boundary. My experience of kevlar is that it is a slippery material and distinctly non-hairy. Whilst it is superior to glass cloth it does puncture. If you have the opportunity, take a couple of patches of kevlar and laminate them together, part their ends slightly to get a grip and you'll find you can just pull them apart by hand without a great effort. Even with the lowley CSM you would not be able to do this. Not very scientific I know but it gives an indication of how easy it would be to produce an inferior laminate without appreciating the material for what it is. Saying a matrial has toughness and strength is not sufficient information in its choice for a particular application.
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Old 21 June 2005, 17:54   #20
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Seem to recall that the US Navy is using RIBs made with kevlar (rather than a polyester) as the base material for the polyurethane fabric. Don't recall where I heard that, though.

As to the Aluminum vs glas debate, see how many hammer blows it takes to hole that glas tube vs aluminum. Then, see how tough it'll be to repair.

Aluminum alloy has better holing resistance than glas, has less upkeep (no gelcoat to chip, peel, or whatever), and can easily be cut and re-welded. A hole or tear in an aluminum hull can be drilled and saber-sawed out, and a patch welded in.

[Hmm. Can you tell I bought Aluminum?]


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