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Old 03-30-2011, 03:49 AM   #21
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Rolling chocks ve Stabilizers

"It begins to feel one's at sea rather than in a hotel or motel room under these conditions:"

Looks like a GREAT! day , for the fly bridge only folks!

Victory at Sea music required.

*

One thing to note is bilge keels work to reduce roll,even when stopped or anchored.


-- Edited by FF on Wednesday 30th of March 2011 03:50:58 AM
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Old 03-30-2011, 09:51 AM   #22
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RE: Rolling chocks ve Stabilizers

These are what I am calling rolling chocks.** They are low profile.* You would keep the away from the stern and away from where the lifting straps would go.
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Old 03-30-2011, 03:33 PM   #23
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RE: Rolling chocks ve Stabilizers

Quote:
shrimp wrote:I am not*familar with some of the terms that are being discussed here ...*
Bilge keels and "rolling chocks" are the same thing and do the same job. The use of the term depends on where and who is using it.

*
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Old 03-30-2011, 03:56 PM   #24
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RE: Rolling chocks ve Stabilizers

I was under the impression that a bilge keel ran the full length of the hull at the turn of the bilge. and only 6 to 8 inches and a rolling chock was smaller/ shorter and of greater dimension perhaps as much as 10 to 12 inches laterally such as an active stabilizer fin.

But hey I have been wrong before*

I probably read it on the internet.

SD
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Old 03-30-2011, 11:12 PM   #25
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RE: Rolling chocks ve Stabilizers

<table style="width:100%;"><tbody><tr><td align="left" width="50%">Great, inexpensive, highly useful*stabilizer
Dad was never able*bring*it to production/marketing in the boating world.* As a mathematical engineer he*simply did not know how.*He designed it*for trawlers and sail boats.* I know... I spent years building prototypes, fastening them*onto keels and*running sea trials with dad during his years of development process. Potentials galore!* I could make one in my sleep.* BTW - Dad's in-depth joint*designs were used on*Apollo Lunar Module's*landing gear.* 1<sup>st</sup> to land on moon, 1969.*
Link: http://patft.uspto.gov/netacgi/nph-P...tis+AND+samuel)

United States Patent
</td><td align="right" width="50%">
*

*

*

*

*

*

*

3,753,415
</td></tr><tr><td align="left" width="50%">Burtis </td><td align="right" width="50%">August 21, 1973 </td></tr></tbody></table>
HYDROFOIL-SHAPED STABILIZING OR ATTITUDE-AFFECTING MEANS FOR BOATS


<center>Abstract</center>
A hydrofoil-shaped stabilizer or attitude-changing means for boats, having an elongated frame assembly adapted to be connected to a submerged portion of the hull of a boat with its longitudinal axis parallel to the fore-to-aft axis of the boat. A flexible curtain assembly extends about the frame assembly and is fixed thereto but free to move laterally and to a more limited extent longitudinally relative to the frame assembly. The interior of the curtain assembly communicates with the surrounding water and is deflected to one side or the other relative to the frame assembly by its displacement relative to the water caused by a change in the attitude of the boat so as to form a hydrofoil having a camber for generating forces to oppose the change in attitude to one side or the other when the boat is underway.
<table style="width:100%;"><tbody><tr><td align="left" valign="top" width="10%">Inventors:</td><td align="left" width="90%">Burtis; Samuel G. (Camden, ME)</td></tr><tr><td align="left" valign="top" nowrap="nowrap" width="10%">Appl. No.:</td><td align="left" width="90%">05/203,341</td></tr><tr><td align="left" valign="top" width="10%">Filed:</td><td align="left" width="90%">November 30, 1971</td></tr></tbody></table>
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Old 03-31-2011, 12:17 PM   #26
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RE: Rolling chocks ve Stabilizers

Hydrofoil stabalizers....I think there is a thread somewhere on boatdesign about that. Interesting concept as are kite-sails for propulsion. A look at boats in the year 2100 perhaps.

SD, I kind of thought the reverse: bilge keels keep her from tipping over on the hard and chocks are smaller.
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Old 04-01-2011, 08:36 AM   #27
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Rolling chocks ve Stabilizers

*This is a bilge keel.
<h3 class="r">Bilge Keel</h3>Rolling chocks are shorter and wider. As pictured by Akdadio second from the top.
IMHO.
Am I wrong?
SD




-- Edited by skipperdude on Friday 1st of April 2011 08:42:21 AM


-- Edited by skipperdude on Friday 1st of April 2011 09:11:19 AM
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Old 07-26-2013, 03:35 PM   #28
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Originally Posted by Phil Fill View Post
*
I am still going to add twin bilge keels as we are planning a heading north to Alaska where grids are popular so the boat will stand up right with out*concern of rolling over.* They will also reduce the roll a big.* *
So did you ever add those bilge keels? How did it work out?

I can't seem to find very much discussion of these items on this entire forum....somewhat surprised?
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Old 07-26-2013, 05:12 PM   #29
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Originally Posted by brian eiland View Post
So did you ever add those bilge keels? How did it work out?

I can't seem to find very much discussion of these items on this entire forum....somewhat surprised?
Not yet. I plan on installing them June 2014 when we pull for bottom paint. They will basically be my design but will have professianl glassed to the hull. About 12 ft long, 2 ft high, 1 foot wide and more vertial to support rather than prevent rolling. There was a sail boat on the hard that had twin keels and sat without supports, that I showed the glass person. The Eagle's hull is sort of flat and wide below the engine room.

They are more popular in the Norther desolated areas which have 15+ tide swings, grids are used sand boats go a ground. Many commercial trawler have rolling chocks which are long and narrow to reduce roll, not to support up right.
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Old 07-26-2013, 11:18 PM   #30
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Our Manatee HEY JUDE has bilge keels, ~ 8' long by 10" wide. We don't know how effective compared to a stock KK36, hopefully some day we can compare. She also has a ~ 25% larger rudder. The PO did not know who or when either mode were installed.
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Old 07-26-2013, 11:55 PM   #31
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Hey Jude, those appear to be as nice a job as one could wish for. From a lot of reading this afternoon, it appears the general consensus is that the bilge keels can help the rolling problem to a small degree, but not as much as one would think.

This site probably comes close to one of the best explaination:
Bilge Keels
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Old 07-27-2013, 07:02 AM   #32
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Quote:
Originally Posted by brian eiland View Post
Hey Jude, those appear to be as nice a job as one could wish for. From a lot of reading this afternoon, it appears the general consensus is that the bilge keels can help the rolling problem to a small degree, but not as much as one would think.

This site probably comes close to one of the best explaination:
Bilge Keels
The link discusses twin keels more so than bilge keels....

The designer also discusses "turbulence" generated by flat plate protrusions. After extensive reading, actual observation and a pretty good background in aerodynamics....I'm not sure discussing turbulence of thin plates at 8 knots or less is even worthy of discussion. Sure wetted surface and drag induced by marine growth on them can start to get significant..but plain old drag on a plate that is aligned with flow...I don't think so. Otherwise there would be a huge push to "airfoil" everything in sight in the marine world and I just don't see it. So his "design" guestimations are already suspect in my mind although I know some of his designs that seem to be very nice and well "designed".

Bilge keels seem to work best on very round bottoms....much less so on hard chines. But Most evey round bilge commercial vessel I've seen lately has them...how well they work is very much up to the individual boat and it's stability to begin with.
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Old 08-11-2013, 07:37 AM   #33
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Roll Damping on Two New England Trawlers: An Experimental Study

....from another forum

Quote:
Originally Posted by watto99
Hi
I know that this is a long dormant string, but it's a subject that is very much alive

In my own search for this information I tracked down a report and bought it on line for $40 from the US naval archiect association.
It's well worth the money and answers the questions about benefits and optimum design of bilge keels etc

Here's the title/ authors
Roll Damping on Two New England Trawlers: An Experimental Study
Clifford A. Goudey 1 and Madan Venugopal 2
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Old 11-23-2014, 04:33 PM   #34
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Hi there Tidahapah,

I have a 62ft wooden motor yacht in Vancouver, which rolls somewhat.... you mentioned someone in Canada who designs flume tank systems.... can you recall who that might be? I'd be grateful for a link. Eamonn.
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Old 11-23-2014, 05:41 PM   #35
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... you mentioned someone in Canada who designs flume tank systems.... can you recall who that might be? I'd be grateful for a link. Eamonn.
That would probably be Professor Don Bass of St. John's, Newfoundland.
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Old 11-24-2014, 07:06 AM   #36
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One problem with bilge keels is to not cause too much extra drag , they must be aligned with the water flow at cruise speed.

Otherwise they will act as speed brakes, 100% of the time the boat is moving.

Anyone have a unused test tank, and an accurate scale model?

They do work at damping roll while stopped ,so might help at anchor.

I am not willing to cut mine off as they protect the external keel cooler , but I do have the parts to make a retracting mast , and the regular gear to install flopper stoppers -paravanes for occasional blue water trips.

On the to do list,,,,
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Old 11-24-2014, 01:46 PM   #37
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My rolling chocks protrude about 10" from the hull and run about half the length of the hull, but I don't really think they do a huge amount to limit rolling. The boat still rolls like a pumpkin in a beam sea even though I also have about a ton of ballast.

Luckily the sails stabilize the rolling incredibly well, as long as there 10+ knots of breeze.
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