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  #841  
Old 05-22-2013
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Re: Full or fin keel?

OK. Thanks for the clarification.
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  #842  
Old 07-09-2013
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Re: Full or fin keel?

Still going,eh?

Seems to me that one of the design problems with modern beamy hulls equipped with high aspect ratio and deep fins, and the resulting high bending stresses at the foil to hullbottom join, could be alleviated by using two foils, in a "V" configuration, with the bottom ends joined at the ballast bulb below and the top end affixed to the hull near the chines or bilges. The foils then are in almost pure tension and compression, aside from the lift force, with almost no bending stress.

Has anyone tried this?

K E Froeschner
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  #843  
Old 07-09-2013
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Re: Full or fin keel?

Kefer:
Not a bad idea. In a heeled position one leg of the fin woud be near vertical and that's good. The problem with any configuration of "tandem" keel isthat you have two trailing edges and more drag. There are a number of way to join high aspect ratio fins to hulls. On the SLIVER project we spread the loads out with a series of steel floors that all fasten to the outboard longitudinals that form the front of the setee faces. Keel bolts are well outboard in a T flange and extend all the way up through the floors. I'll see if I can find a photo.

The problem we had with the SLIVER was that the strip planked cedar hull was not capable of taking the keel bolt compressive loads without crushing. So we have to take the loads off the skin entirely. The wood strip planking was removed in a big pan shape around the keel and replaced with solid laminate.

Ok, found one:
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Last edited by bobperry; 07-09-2013 at 07:57 PM.
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  #844  
Old 07-29-2013
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Re: Full or fin keel?

Bob:

Thanks for the reply and photo of Sliver's floors. Looked up "the Sliver Project" on the web ... OUTSTANDING.

Nice to read of your love of Wm. Garden. I checked his books out of the libary as a kid and pored over them for so long that they eventually fell apart -- maybe it was just books with his designs in them. And your love of 30 Square's as well. There was one moored in Mariner Lagoon for years that I drooled at. It was eventually hauled to Svendsen's in Alameda and rebuilt by Peter Schwab. He raced in the Singlehanded Transpac to Japan, but I can not recall the result. (Probably won.)

Sorry for the thread drift -- but, just had to thank you.

"Bob, You done good."

kef

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Re: Full or fin keel?

Kef:
I still have the Garden design catalog he gave me whan I was 15 years old and depsite being referred to and read countless times I am happy to say it is not falling apart. I know where it is right now. I always know where it is. Wish I had had the brains to have had him sign it.

The SLIVER Project boat was moved last week to the yard in Seattle where it will be finished. Here are some pics
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  #846  
Old 07-29-2013
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Re: Full or fin keel?

One of the things which is happening on the more extreme versions of the small root keels is that they are building 'cassette' style keel connections in which the end of the keel inserts into a tightly fitting box inside the hull. This allows a much bigger contact area to resist bending and torsion. Of course the box needs to be heavily constructed and needs a sophisticated transverse and longitudinal framing system to be able to distribute loads outward into the hull.

FWIW I like Garden's work aesthetically and from a historic point of view.

Jeff
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  #847  
Old 07-29-2013
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Re: Full or fin keel?

Quote:
Originally Posted by Jeff_H View Post
One of the things which is happening on the more extreme versions of the small root keels is that they are building 'cassette' style keel connections in which the end of the keel inserts into a tightly fitting box inside the hull. This allows a much bigger contact area to resist bending and torsion. Of course the box needs to be heavily constructed and needs a sophisticated transverse and longitudinal framing system to be able to distribute loads outward into the hull.

FWIW I like Garden's work aesthetically and from a historic point of view.

Jeff
That sounds like what Seaward does with its retractable keels; the high aspect keel slides up and down a box that looks (at least on their website's videos) to be rather robustly incorporated into the hull. Makes sense as a way to spread the load of a grounding even if the foil is nonmoving.
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