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Old 16 July 2008, 15:25   #1
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Alternative to an inflatable keel?

Is there any for SIB's?
I tried to pump keel in my boat up to an 8pci. It still flex. I am thinking to stick metal pipe (removable) filled with a cement mix between keel and bottom or keel and all. floor ... Not sure if it worth to try however.
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Old 17 July 2008, 00:28   #2
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You should not be pumping your keel up beyond 3.5 - 4 psi. It doesn't matter if the keel flexes. The purpose of an inflatable keel is not to provide rigidity to the boat. A SIB's rigidity comes from the main sponsons and the floorboards. The purpose of an inflatable keel is to help with tracking and and to soften the ride in choppy conditions.
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Old 17 July 2008, 09:12   #3
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Well ... according to specs I have to pump it to a 5.8psi. But it handles 7psi no problem. I once forgot to top it to a specs and it was very unpleasant ride. Soft keel cannot produce enough tension for a bottom material and water and air buildup in the end of the boat (underneath) causing weird boat behavior while on the plane. Hard keel chops through waves better than a soft one according my observation.

Sadly but my aluminum floor does not provide rigidity I would like to see :| That is why I would like to place solid bar underneath it.
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Old 17 July 2008, 09:46   #4
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Some of the older Bombards have a wooden keel. I suppose you could replace the inflatable tube with a custom fitted piece of lumber, but I'd worry about the strength of the floor fabric.

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Old 17 July 2008, 10:31   #5
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Quote:
Originally Posted by jyasaki View Post
Some of the older Bombards have a wooden keel.
Do you remember model name? I'll try to search for assembling instructions. I suppose it would be difficult to assemble floorboards after fitting wooden keel in place ...
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Old 17 July 2008, 15:52   #6
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Do you remember model name? I'll try to search for assembling instructions. I suppose it would be difficult to assemble floorboards after fitting wooden keel in place ...
I want to say a "C5"? About a 16' big black monstrosity. Probably from the mid-80's. Maybe.

I am going from memory here, as the owner of the particular boat replaced the wooden floor with some huge slabs of diamond-plate aluminum (not cut the same as the originals.) But, the keel itself, I think, was in two pieces. The rear-most and front most floor panels attached to the two keel pieces (bolted in, I believe.) Insert the front into the bow, the rear either up against or under the transom (sorry; don't remember now), then lever the keel joint down into place, stretching the boat. I think a couple of metal plates bolted over the joint to make it rigid. Then the rest of the floor was inserted, and the last pieces levered in in the same manner as the keel. Side-rail stiffeners were inserted to lock the floor pieces together, and the boat was inflated.

jky

Apparently, I lied. The keel was in 3 sections (no idea how it went together.) Some kind of no-tooling joinery. You can see the brochure for Bombard 2008 here:
http://pdf.nauticexpo.com/pdf/bombar...0348-6231.html
You want to look at page 15.
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Old 17 July 2008, 23:28   #7
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Quote:
Originally Posted by dim. View Post
Well ... according to specs I have to pump it to a 5.8psi. But it handles 7psi no problem. I once forgot to top it to a specs and it was very unpleasant ride. Soft keel cannot produce enough tension for a bottom material and water and air buildup in the end of the boat (underneath) causing weird boat behavior while on the plane. Hard keel chops through waves better than a soft one according my observation.

Sadly but my aluminum floor does not provide rigidity I would like to see :| That is why I would like to place solid bar underneath it.
I was thinking pressure for hypalon, but yea, if it's PVC the maximum pressure would be higher. Is the aluminum floor flexing primarily at the joints between the sections or throught the whole boards?
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Old 18 July 2008, 04:37   #8
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Quote:
Originally Posted by dim. View Post
Is there any for SIB's?
I tried to pump keel in my boat up to an 8pci. It still flex. I am thinking to stick metal pipe (removable) filled with a cement mix between keel and bottom or keel and all. floor ... Not sure if it worth to try however.
You may like to look at ways to strengthen the floor rather than the keel, perhaps side bars that overlap every board?
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Old 18 July 2008, 11:16   #9
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No. Not joins. I have side bars. It is like whole floor bends for a moment and flattens back again.
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Old 18 July 2008, 11:20   #10
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jky, thanks for the link. At least it is possible
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