Rolling chocks ve Stabilizers

How effective are rolling chalks?*
*Or another term Bilge keels. In relation to stability.

SD

Well, that is a good question as I am plan on adding bilge keels to the Eagle to keep up right on a grid/hard/aground and to reduce the roll. Both are passive stabilation as they require not activations, do no move and are there all the time. I think they are basically the same except rolling chocks are longer and not as height as bilge keels. Where as bilge keels are short, higher and stronger meant to in addition too help support the boat.* I think both will reduce the roll but they will also reduce the speed and range. ************

I want to increase the stability/reduce the roll/and support the boat.* Much rather have passive than active stabilization.* At the same time may added a bulbous bow to weight down the bow and protect is as I have seen a lot of bow damage on boats from Alaska.*

I just had a new thick all aluminum mast installed which replace the old wood mast in required to added fish stabilizers in the future, but bilge keels are first and then see how the stability roll are.* *

Did you ever put the ballast back in you took out?


-- Edited by Phil Fill on Tuesday 1st of June 2010 10:40:52 AM

-- Edited by Phil Fill on Tuesday 1st of June 2010 10:41:14 AM

Negative. She seems to do fine without.
Although I do deploy the paravanes more often in heavy seas. As indicated in the thread on putting your boat to work. Pounded thru som 5 to 6 ft seas with gale force winds.
No fun but survivable.

Sd

If I had the area/room I would add ballast before the rolling chokes/bilge keels to reduce the roll.* Might want to put the ballast back in?

I have a few rib spaces that I plan on filling with concrete so they do not collect moisture/water maybe a couple hundred lbs.* However, that not really for stability/roll!* The area they dug out for the bow thruster should be filling in also as that is the biggest area for condensation.* I have 4 dri easy in the area*to dry up the*moisture, but if the shower sump does not work it fills the area with*yucky*soapy water.*

Skipper, that would probably be impossible to answer.* Delfin came with roll chocks that run about 3/4 of the hull under water.* I have no clue what her roll would be without these chocks (or the active fins I added), but since they had been building this style of hull for 100 years when they took the time to weld these on I presume they must have had a reason.* I don't know if adding them to your boat would make enough of a difference to be worth a retro fit, especially when compared to the known benefit of active fins or fish.

Phil Fill wrote:I just had a new thick all aluminum mast installed

Click to expand...

Did I just read somewhere that your new mast has fallen off? At the dock?

Yes, the stay backing plate pulled*out.** Lucky I noticed the boom tipping the mast leaning which fell slowly*and I managed let down gently on to the storage box and then some neighbors help to undue the stays and lay on the roof.* *They installed backing plates that were 2 x 4 that were mounted between two support studs the weakest place*and the after 32 years the ¾ ply rotted.* So the plant is make new SS backing plates 18 X 11 that will be bolted through.* I knew the backing plate were the next week point, but was going to wait until the fish stabilizers were install.* So now additional stays and supports will be added in preparation for fish stabilizers.*


*
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.* *

Our US Navy Utility (50ft) has had shallow bilge roll devices added,

They are about 35 ft long and 8 or so inches deep.

The heavy weight of a small cargo mast , and boom , and mid shelf transfer larger offshore, filled lobster pots was the concern.

AS a lobster re supply boat the Mainacs thought it would stabilize the boat when alongside , loading and unloading.



I have no idea how a similar un modified boat would respond , but the boat is very quick to stop rolling , say after a 2- 4ft wake broadside.

Another up side is the keel cooling is protected by the keels.

We have gone thru breaking water at inlets and she steers as if on rails.

Downside is there certainly is more wetted surface to drag thru the water at all speeds, but a sand bar or dry beach layover is at a much lower angle of heel.

These low aspect ratio keels can be easily added as an after thought.

Sailboat style BILGE KEELS ARE FAR DEEPER and would require a rebuild of the interior and localized hull structure to assume the far heavier loads .

I have a friend that has the 1000lb ball deally being installed in his boat right now....have no clue what it is called. It is that thing where the ball rolls back in forth apposite the roll of the boat. We'll see how it works. He usually cruises coastally anyway so it won't get any real ocean work so it should suit him fine if it even works moderately well.

skipperdude wrote:

How effective are rolling chalks?

Click to expand...

From everything I have read and from the few people I have had conversations with about this topic, bilge keels help but they are no comparison to the roll stability one gets with either active stabilizers or passive stabilizers (birds).

*

Bilge keels and rolling chokes are not quite the same thing.* They serve the same purpose of reducing the roll.* Rolling chokes are long and not very deep/high, where as bilge keels are shorter and deep/higher and level with the center keel, so the boat can sit on them. **


*
The preliminary design of the bilge keels to be installed are 12 to 18 high/tall and 10 to 12 ft long to fit between the two pick sling points. *There is no internal structural support required as the surface will be spread over a wide area and fiber glassed to the hull* I will have Michael Kasten in Port Townsend WA marine engineer design, the bilge keels installed *at the Port Townsend yard as it is more commercial than pleasure and where I saw bilge keels being added to a trawler the first time. I have talked to Kasten several times at boat shows and trawler fests as several of his designs have them


*
Anti rolling tank is interesting as its a tank with baffles 1/2 filled with water, that sloshes back and form.* The baffles time the water to be opposite the roll, so by the time the water sloshes to one side the tank the boat it is starting to roll to the opposite side.* I have not heard about a weight ball but probable the same principle, to counter the roll


*
The new SS chain/pressure plates are made and will be installed today.* *


*

Delfin has roll chocks, which were augmented with active fins from ABT.* Without the fins, she is fairly stable, although I turn the fins on whenever we enter we enter a lot of current, wave action, etc.* Delfin's sister ship, Torsk, does not have active fins and carries sails to help stabilize her offshore.* It's hard to quantify a negative (what Delfin would be like without roll chocks) but a subjective opinion is that they help a fair amount, but are no substitute for active fins (or paravanes) when the going gets sloppy.

John,I think you're talking about a Gyro. I read your post again John and it dosn't sound like a gyro anymore.


Everyone,
There's a down side to all bilge finns. When a boat is heaped up high on a breaking sea broadside to the wave finns tend to trip the boat and make it more vulnerable to capsize.
I slid sideways down the face of several waves in the 70s and the ability of the boat to do that saved my life I'm quite sure. I think a boat needs the ability to slide sideways at times and for that reason one of my favorite cross-sectional hull forms is the double hard chine "sampan". Older racing runabouts had such a chine to prevent them from capsizing in sharp turns.


Eric


-- Edited by nomadwilly on Wednesday 21st of July 2010 09:58:38 PM

It is a 1000lb ball that rolls opposite of roll of the boat. I would assume there are gyros involved to be able to compute the attitude of the boat. How it gets the ball rolling in the opposite direction, I have no clue. It will be interesting to see how it works. I know I would not be an "early adopter" of this sort of thing. Active fins would suit me just fine. I guess the advantage of the ball thingy is that there are no thru hulls or fins that may snag trash or get harmed in groundings. We have shallow water over here.

When a boat is heaped up high on a breaking sea broadside to the wave fins tend to trip the boat and make it more vulnerable to capsize.

Lying a hull, is a sail technique , used in conditions that most marine motorists will never encounter.

The sailboat can easily handle being tossed into a trough , or breaking waves from abeam,

conditions not contemplated in the design or construction of 99% of "trawlers".

Some times bilge keels like structures are used to protect the stabilizer fins.* A sister 58 Roughwater had fins stabilizers that went out so he fiber glassed them solid in the keel protection.* He claims the ride is just as good as when the fins were working.*** Now he has fixed bilge keels.


*
I had several stabilizer fin sales reps look the Eagle they all said for the 30 grand the fins performance would be poor because of the rounded hull and the slow speeds.* They recommend rolling chokes/bilge keels and/or fish stabilizers.* So that is why I am leaning toward bilge keels first.*


*
Eric, now you are getting into an area we seldom discuss? You make an interesting point about being able to slide? Sliding would seem to be for semi displacement/plaining boats so the boat slides down the wave rather than take the force of the wave?* It seems most stabilization prevent sliding to reduce the rolling, fins, fish, chokes, and keels?


*
Laying a hull, for those that do not know what it means is batten down the hatches and letting the boat drift at the mercy of the sea.* Rather than laying a hull I would lay a sea anchor to keep the bow into the waves. Rather than wallowing in the trough.* Having a rounded stern also helps so the wave passes around and under the boat.* We have a sea anchor but have not used and a rounded stern.


*
A another ratio/term is the maximum angle a boat is able to keel/roll with out turning over which is more of a sail boat and/or blue water power boats factor. The Eagle has a calculated 70 to 75 degree keeling angle, so if bilge keels and/or fish can prevent the Eagle from keeling/rolling more than 70 degrees to me that is a plus. One of the main reasons for stabilization is to help prevent the boat reaching the maximum keel/roll angle.


*
The new backing plates where installed and the new aluminum mast is back up. I dont think the mastsupport are *strong enough for fish so additional stays/support will have to be added.* Probable side chain plates and stays*to be added like sail boats to support the mast.*Anyway that will be several years.**




*

Interesting thread, wanted to revive it. Skipperdude and / or Phil Fill...did either of you install rolling chocks on your boat? Mine is a hard-chine 36' trawler and I am wondering if the chocks would help as much as they do on a rounded full displacement style hull. I started another thread on this today, then found this one after.

The other way to go is a flume tank.
There is a guy in Canada who designs them for various boats.
No the same as fitted to some large rig tenders where you have to have a high capacity pump to pump the water in and out.
These are designed to be partially filled and have a number of designed baffles to control the cross flow of water.
If I can find the connecting thread I will post it.

Benn

I am not*familar with some of the terms that are being discussed here, some pictures would be a great help for those of us who are all at sea when we leave the horizontal.

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



*

"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

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.

shrimp wrote:I am not*familar with some of the terms that are being discussed here ...*

Click to expand...

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.

*

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

<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^st to land on moon, 1969.*
Link: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.htm&r=7&p=1&f=G&l=50&d=PALL&S1=(burtis+AND+samuel)&OS=burtis+and+samuel&RS=(burtis+AND+samuel)

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

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*

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*

*

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%">http://patft.uspto.gov/netacgi/nph-...S=burtis+and+samuel&RS=(burtis+AND+samuel)#h1http://patft.uspto.gov/netacgi/nph-...S=burtis+and+samuel&RS=(burtis+AND+samuel)#h3Burtis; 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>

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.

*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

Phil Fill said:

*
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.* *

Click to expand...

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?

brian eiland said:

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?

Click to expand...

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.

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.