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Old 02-13-2019, 12:02 AM   #1
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Bilge Keels

Has anyone fitted bilge keels to a trawler(let`s skip the semantics) or an SD power boat hull, with twins or single.

If so, what form did they take, where were they placed,how was it done and attached,why did you do it, and what was the result.
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Old 02-13-2019, 01:04 AM   #2
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I would be interested in that also. I have been toying with the idea of putting them on my boat.
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Old 02-13-2019, 01:29 AM   #3
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Bilge keel are also known as rolling chocks in some parts. Here is a fairly long thread on them that might be worth perusing.
Rolling chocks ve Stabilizers
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Old 02-13-2019, 07:13 AM   #4
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Quick cut...


In previous threads I believe "batwings" were recommended as successful on hard chine boats where tough to fit bilge keels.


Soft chines are successful with bilge keels.


Someone reported success with some sort of chine "lip" on a hard chine trawler.


All create wetted surface and drag...so sizing is important to get the best compromise of rolling and speed reduction.
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Old 02-13-2019, 08:12 AM   #5
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I have read most of the articles on these in the past, and couldn’t draw any hard conclusions as to whether they made much of a difference.
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Old 02-13-2019, 09:33 AM   #6
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From what I've gathered, rolling chocks (the ones that typically protrude less than a foot from the hull and run about 3/4's the length of a semi-displacement hull at the chine) reduce roll only about 30%. I think the most important change rolling chocks would offer is in going from 'snap rolls' typical with a semi-displacement hull, to a softer change of direction.

They're probably the cheapest and easiest to maintain, as well as offering the least amount of worry; always deployed, never get fouled in debris or kelp, and won't get knocked off by deadheads.

Had a chat with a retired commercial fisherman based off the north end of Vancouver Island who had rolling chocks put on his semi-displacement hull. He said he put them on more for fuel savings, insisting they provided a bit of lift at cruising speed. Not sure about that one...
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Old 02-13-2019, 09:40 AM   #7
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Murray at what angle? Straight down, 45 degrees, 30 degrees ....
If not straight down it would seem they could be damaged from floats or pilings.
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Old 02-13-2019, 09:48 AM   #8
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Murray at what angle? Straight down, 45 degrees, 30 degrees ....
If not straight down it would seem they could be damaged from floats or pilings.
45 degrees from looking at them. They're attached at the turn of the hull on a displacement hull or the chines on a semi-displacement hull, so they shouldn't extend out further than the rub rail or gunwale.
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Old 02-13-2019, 10:01 AM   #9
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Hi Eric,

Looking at the photos in the following post I can see how docks might be a concern, but then again, that's what fenders are for

Trawler Forum - View Single Post - Rolling Chocks make them on the cheap
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Old 02-13-2019, 10:21 AM   #10
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When I was considering a Schucker and was a member of their Yahoo group, one of the members had installed them on his boat. The Schucker is basically a fat round sailboat hull with a modest keel. The owner was quite pleased with the roll reduction and speed of roll.

My guess is the more round your hull is with less keel, the bigger the difference they will make. My boat has hard chines, is quite flat in the stern, and has a large keel in the stern third. These attributes I believe, make the roll very reasonable compared to many other boats. While it would be nice to reduce it further, it's likely only active stabizers would significantly improve it.

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Old 02-13-2019, 12:01 PM   #11
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I was once a partner in a steel 78' stern trawler and the other partners insisted we needed roll chocks. After having them designed by a naval architect and having them fabricated and welded to the hull they made very little difference in the vessels roll. They may have dampened it marginally but the difference from not having them was hardly worth the twenty thousand plus they cost. After we sold the boat the new owners put paravanes on it which by reports made a satisfactory difference. I had another smaller trawler that I put a steadying sail on and was quite happy with the result, especially for the minimal investment. My current boat will be getting a sail.
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Old 02-13-2019, 12:19 PM   #12
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Hi Eric,

Looking at the photos in the following post I can see how docks might be a concern, but then again, that's what fenders are for

Trawler Forum - View Single Post - Rolling Chocks make them on the cheap
I would never order or build chocks like those in the link.
I canít belive they pulled that boat w the travel lift. Seeing that they are that strong I wouldnít pay the weight penalty either. Something that shouldnít exist IMO. But Iíve seen round bilge boats with similar but I donít think they usually stick out beyond the hull.
And the chocks in the link may cause that boat to trip and capsize rather than remain upright and just broach.
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Old 02-13-2019, 02:06 PM   #13
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I didn't add mine so it is tough to say how much roll reduction they provide. The boat still has significant roll in a beam sea, but with the sails up I get a 90% reduction in roll.
With any stabilising system, they are far more effective on a soft chine round bilge vessel in comparison to a hard chined SD vessel.

Here's a thread on retro-fitting a set of rolling chocks:
Rolling Chocks make them on the cheap

I have no concerns in the travel lift. My rolling chocks/bilge keels are about 2" thick and protrude about 8-10" from the hull, but are not far off vertical.
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Old 02-13-2019, 03:44 PM   #14
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AusCan,
Looks good to me but not much style but out of sight.

I see your keel and it looks much like mine. Like the flat sided tear drop rudder and it looks like a very stout shoe too. May even up-stage the Willards there mate.
And I agree sails are the best anti rolling device.

Are you on a marine railway?
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Old 02-13-2019, 03:44 PM   #15
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I believe Fast Fred has them on his converted Navy UTB "Lucy". The previous owner installed them I think..
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Old 02-13-2019, 05:48 PM   #16
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One advantage of passive "bilge fins", as the Millkraft Yard here calls them in an Invoice,is that although they are likely not as effective as active fins, they don`t need power,hydraulic and/or electrical, and running a genset. I saw a stabilized late GB42 advertised with 1250 hours on the mains, and a rebuilt genset with 1000 hours. I suspect a connection.
According to an owner of a 40ft SD boat, if I understood correctly,the fins reduce roll after the first roll occurs.
Pretty sure bogranjac1/Brett made and fitted his own, as well as flopper stoppers.
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Old 02-13-2019, 05:57 PM   #17
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Not a lot on the interwebs about proven performance but I did find this article about roll dampening vs stability interesting: https://seagrant.uaf.edu/bookstore/b...ilge-keels.pdf
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Old 02-13-2019, 05:59 PM   #18
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Fish53 has spent his life running boats and gave you his opinion. My impression is similar from I have read when I was researching Stab Systems about 2 years ago. But, others also say they help, so I suppose its up to you to determine if they are worth it and how much bang for the buck they could provide.
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Old 02-13-2019, 07:02 PM   #19
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Quote:
Originally Posted by Nomad Willy View Post
AusCan,
Looks good to me but not much style but out of sight.

I see your keel and it looks much like mine. Like the flat sided tear drop rudder and it looks like a very stout shoe too. May even up-stage the Willards there mate.
And I agree sails are the best anti rolling device.

Are you on a marine railway?
Oh mate, Not much upstages a Willard, but thanks for the compliment.
The shoe is stainless. I treated it with prop speed as regular antifouling doesn't last long on it, and any buildup of growth disturbs the flow to the prop.

Yes , our little marina has a rail mounted slipping setup. It works well. There's no worries of a boat getting dropped.
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Old 02-13-2019, 07:25 PM   #20
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Here's another good article on roll attenuation.

Roll Attenuation and Bilge Keels
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