Rolling chocks and stabilizer wings, very interesting designs.

ben2go · Aug 8, 2019

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/

MurrayM · Aug 8, 2019

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.

Ken E. · Aug 8, 2019

MurrayM said:
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.

Comodave · Aug 8, 2019

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

dhays · Aug 8, 2019

Ken E. said:
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.

Comodave said:
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.

MurrayM · Aug 8, 2019

dhays said:
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.

ben2go · Aug 8, 2019

dhays said:
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.

Simi 60 · Aug 8, 2019

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

ben2go · Aug 8, 2019

Simi 60 said:
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.

FF · Aug 9, 2019

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.

jleonard · Aug 9, 2019

FF said:
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.

MurrayM · Aug 9, 2019

FF said:
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 didn’t work on trawler speed vessels of our size.

ben2go · Aug 9, 2019

MurrayM said:
These guys make them: https://humphree.com/interceptors/

I contacted them a few years back, but the system at that time didn’t 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.

MurrayM · Aug 9, 2019

ben2go said:
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

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/

Mako · Aug 9, 2019

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.

bogranjac1 · Aug 9, 2019

makobuilders said:
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.

ben2go · Aug 10, 2019

MurrayM said:
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.

Flybull · Aug 10, 2019

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?

dirtdoc1 · Aug 11, 2019

"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

ben2go · Aug 11, 2019

dirtdoc1 said:
"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.

Wayne · Aug 16, 2019

'Lo all,
I see real knuckle busters

when trying to scrape barnacles off them...

rgano · Aug 17, 2019

What Wayne said! :banghead:

Simi 60 · Aug 17, 2019

They make these wonderful devices called gloves.
Perhaps you've heard of them?

BruceK · Aug 17, 2019

dirtdoc1 said:
"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

Interesting pic. I looked at a 40ft SD trawler, a Clipper 40, which had a section of bilge keels fitted midship first,and later added another separate section, as your pic shows,right aft. The boat had a single, I figured the aft section might impede swinging the stern. What happens in practice?

rgano · Aug 17, 2019

Simi 60 said:
They make these wonderful devices called gloves.
Perhaps you've heard of them?

Use gloves in line handling lose hands. Not on my watch!

Rolling chocks and stabilizer wings, very interesting designs.

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