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Old 26-10-2008, 03:00   #1
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Type of wood for sacrificial keel

Hi,

I have just bought an second hand catamaran, and I have a few jobs to do.

The boat is foam sandwich, and has never had any sacrificial keels fitted. I mean little keels, maybe 8 feet long, 4 inches wide, 4 inches deep, for supporting the boat when it is beached. (it is a 30' boat )

What type of wood would you recommend I use?

I am thinking of making laminates of 1 cm strips, and epoxying these to each hull. I need lightness, durability, toughness ( for when I accidentally park on rocks). Someone recommended spruce, but that seems a bit soft to me.

Thanks,

John
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Old 29-10-2008, 13:50   #2
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Oak it is then.
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Old 29-10-2008, 16:55   #3
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Why not douglas fir?
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Old 29-10-2008, 20:41   #4
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Stainless Hardwood

I'd go with clear (no knots) water resistant hardwood. See what your local timber merchant has in stock.

And on the bottom I'd screw some stainless steel flat bar (say 3mm x 30+mm), to take any wear and tear.
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Old 30-10-2008, 00:43   #5
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I happen to have an excess of oak from a previous job. I like the idea of adding the stainless.

Why Douglas Fir? Any advantage?
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Old 30-10-2008, 02:19   #6
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Something about bolting an 8ft 4x4 to the bottom of a 30ft cat hull just sounds wrong, but then I know little about multis.

However if that’s the plan and If you have oak already, I’d think it would be a good choice of wood, especially laminated as you mentioned.
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Old 30-10-2008, 03:17   #7
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I didn't mention bolts! I was thinking up expoxying the wood to the hull, but I have been advised that gluing it on with SikaFlex works just fine - some catamaran manufacturer ddoes that as standard. The thing is sacrificial! I would rather lose it than have bolts through the hull.

I have also been advised that 4" wide, and 2" thick would be better - there'd be less leverage to pull it off than with 4x4.
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Old 30-10-2008, 08:39   #8
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Buy yourself some star board and you can beach it on a iceberg and still slide off, air boats in the Florida everglades use it on the bottoms and they hit things hard. We used a piece on the front of a F-27 that we molded and laid up with underwater adhesive such as 5200 then faired it for performance, worked perfect. Just heat the star board and shape it while it cools.
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Old 30-10-2008, 14:18   #9
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Aloha John,
I only suggested douglas fir because it is light, strong and cheap. If you already have the oak then use it. I don't know what star board is so maybe that's a good alternative.
JohnL
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Old 30-10-2008, 14:36   #10
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Star board is a non-pourous hard plastic that is slick, we use for all kinds of applications in race boats, anti chafe pads for sheets and lines as well as block deck pads and it can even be used as compaion way slides and hatches for the entryway it's easy to use with a saw, router and even a table saw, as good as wood and will never rot or retain water, best part no varnishing. it's in the west marine catalogue.
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Old 30-10-2008, 14:48   #11
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I don't know about adding the stainless. The builder of my boat put stainless shoes on the bottom of the keels. They were eaten to death, and I was advised by the yard it was because of bottom paint? Any one know any different?

The previous owner also put ironwood pads on the sterns. He left the boat once for 3 months, and came back to the sterns worn from rubbing the quay.
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Old 30-10-2008, 15:12   #12
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I wouldn't add stainless either, but you can heat bend star board to conform to the hull and 5200 them up with some adjustable short yard stands for a powerboat to get a good adhesion then all you have to do carefully grind the edges smooth, this way they wont tear off when beaching or catch on any lobster, crab, nets or mooring lines, I have done this and it works, will last longer than the hull when put on correctly.
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