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Old 08-08-2019, 11:10 AM   #1
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Rolling chocks and stabilizer wings, very interesting designs.

Has anyone seen these before? I've seen rolling chocks but never this design. They are a very interesting designs. No affiliation of course.


https://rlmarine.com.au/fabrication/














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Old 08-08-2019, 12:58 PM   #2
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The first ones make sense, in that forward progress wouldn't be effected much, but while rolling there should be lots of turbulence which might make the 'rolling chocks' even more effective.

This may be counterintuitive, but a solid rolling chock might be more effective because of the turbulence created by its whole length, rather than having it staggered as shown?

The second ones are 'hinged fins' which seem to be a New Zealand idea that's gaining traction in the commercial fishing fleet.
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Old 08-08-2019, 04:07 PM   #3
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The first ones make sense, in that forward progress wouldn't be effected much, but while rolling there should be lots of turbulence which might make the 'rolling chocks' even more effective.

This may be counterintuitive, but a solid rolling chock might be more effective because of the turbulence created by its whole length, rather than having it staggered as shown?

The second ones are 'hinged fins' which seem to be a New Zealand idea that's gaining traction in the commercial fishing fleet.
Murray, are 'rolling chocks' and 'bilge keels' the same thing? Many salmon seiners have a solid version of the top photo.
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Old 08-08-2019, 04:11 PM   #4
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I wonder if the staggered version would create more drag when moving forward through the water than a solid one?
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Old 08-08-2019, 04:46 PM   #5
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Murray, are 'rolling chocks' and 'bilge keels' the same thing? Many salmon seiners have a solid version of the top photo.

This question comes up a lot. In my mind bilge keels seem to be placed more on the bottom of the hull and designed to be able to support the boat so it rests upright on the bottom when the tide goes out. Rolling chocks tend to be placed further outside and are designed solely to reduce the rate of roll.


I could be complete wrong however.


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I wonder if the staggered version would create more drag when moving forward through the water than a solid one?

That is my thought as well whenever I see that design vs the solid.
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Old 08-08-2019, 05:07 PM   #6
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This question comes up a lot. In my mind bilge keels seem to be placed more on the bottom of the hull and designed to be able to support the boat so it rests upright on the bottom when the tide goes out. Rolling chocks tend to be placed further outside and are designed solely to reduce the rate of roll.
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Old 08-08-2019, 05:36 PM   #7
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This question comes up a lot. In my mind bilge keels seem to be placed more on the bottom of the hull and designed to be able to support the boat so it rests upright on the bottom when the tide goes out. Rolling chocks tend to be placed further outside and are designed solely to reduce the rate of roll.


I could be complete wrong however.





That is my thought as well whenever I see that design vs the solid.

To add to this. Bilge keels can be large and hollow filled with ballast material. Some can be just plate steel. It's rare to see bilge keels on fiberglass or wood boats. It adds great cost and complexity to build from my understanding.


Rolling chocks are more out on the hull at the chines or close to where chines could be on a round bilge boat if it had them.




Bilge keels.
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Old 08-08-2019, 05:56 PM   #8
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I have shown those ones from Rogers and Lough a few times on here as well as the Moreton Bay Boat Works composite version of the same

Apparently, from those that have used them, they are much improved on the traditional type of rolling chock
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Old 08-08-2019, 06:08 PM   #9
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I have shown those ones from Rogers and Lough a few times on here as well as the Moreton Bay Boat Works composite version of the same

Apparently, from those that have used them, they are much improved on the traditional type of rolling chock



I have missed your posts somehow.
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Old 08-09-2019, 06:09 AM   #10
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I have often wondered if over sized trim tabs with a fast acting response would not come close enough to stabelizing the boat for most folks .

No drag or sinking danger as active fins , no air height hassles , orunderway pole and fish deployment .

Easy to retrofit.
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Old 08-09-2019, 06:48 AM   #11
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I have often wondered if over sized trim tabs with a fast acting response would not come close enough to stabelizing the boat for most folks .

No drag or sinking danger as active fins , no air height hassles , orunderway pole and fish deployment .

Easy to retrofit.
They help stabilize at anchor, not so much underway.
That's my experience on my old 34 Mainship and "standard" 12 x 42 Bennet tabs.
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Old 08-09-2019, 09:16 AM   #12
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I have often wondered if over sized trim tabs with a fast acting response would not come close enough to stabelizing the boat for most folks .

No drag or sinking danger as active fins , no air height hassles , orunderway pole and fish deployment .

Easy to retrofit.
These guys make them: https://humphree.com/interceptors/

I contacted them a few years back, but the system at that time didnít work on trawler speed vessels of our size.
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Old 08-09-2019, 09:40 AM   #13
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These guys make them: https://humphree.com/interceptors/

I contacted them a few years back, but the system at that time didnít work on trawler speed vessels of our size.
Those are trim tabs to keep the bow down on a planning boat. They don't add stability in bad weather.
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Old 08-09-2019, 02:06 PM   #14
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Those are trim tabs to keep the bow down on a planning boat. They don't add stability in bad weather.
Tut tut tut.

Should have read further.

It is considered proper Trawler Forum etiquette to forward one boat buck to the offended party when such an egregious error results in tarnishing the impeccable standing of said party

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Automatic roll and pitch stabilisation

While operating in open seas boats are constantly exposed to waves that will cause roll and pitch motions resulting in reduced comfort on board. With Humphree Active Ride Control system the Interceptors are instantly actuated to provide lift which counteracts these motions and at the same time optimises the running trim and list angle – all in one system.
https://humphree.com/functions/active/
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Old 08-09-2019, 03:32 PM   #15
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I could see how this style would generate more turbulence than a solid bilge chock (turbulence is good) and be more effective at roll reduction.



Does anyone have any calculations or performance specs on how effective they are?



However one downside is that the staggered plates could catch seaweed or such, perhaps some chunks of ice, or flotsom.
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Old 08-09-2019, 07:38 PM   #16
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I could see how this style would generate more turbulence than a solid bilge chock (turbulence is good) and be more effective at roll reduction.



Does anyone have any calculations or performance specs on how effective they are?



However one downside is that the staggered plates could catch seaweed or such, perhaps some chunks of ice, or flotsom.
Makobuilders,
Not intending to ridicule your post as all quite valid points however a smile did cross my face at the thought of a " chunk of ice" being anywhere near me other than in a tall glass with copious amounts of scotch.
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Old 08-10-2019, 11:08 AM   #17
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Tut tut tut.

Should have read further.

It is considered proper Trawler Forum etiquette to forward one boat buck to the offended party when such an egregious error results in tarnishing the impeccable standing of said party



https://humphree.com/functions/active/





I didn't quite get it on the first read through.


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Old 08-10-2019, 03:26 PM   #18
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With that open design, does it work due to the water below being forced upward as it passes, and the force of the water then hitting the upper surface from underneath "lift" it, thus "lifting" that side of the boat that was rolling, effectively lessening the roll...?

Any fluid dynamics experts here?
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Old 08-11-2019, 01:56 AM   #19
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"It's rare to see bilge keels on fiberglass or wood boats. It adds great cost and complexity to build from my understanding."

$6500 for both
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Old 08-11-2019, 07:55 AM   #20
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"It's rare to see bilge keels on fiberglass or wood boats. It adds great cost and complexity to build from my understanding."

$6500 for both



Those appear to be rolling chocks. Bilge keels are usually much shorter and run deeper in the water to allow the boat to sit up right when the tide runs out.


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