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Old 05-06-2019, 12:17 PM   #1
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North Pacific Trawler 39 getting rolling chocks

This vessel is on the hard beside my vessel. It is owned by a former commercial fisherman is getting rolling chocks.

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Iíve watched this FRP guy install these before on commercial vessels. He will lay down a skin of FRP, then glue down pieces of foam, then complete layers of FRP over the foam.

Jim
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Old 05-06-2019, 12:39 PM   #2
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It looks like special care may be necessary when using a travel lift.
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Old 05-06-2019, 12:51 PM   #3
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It looks like special care may be necessary when using a travel lift.
it looks like they could hit pilings also
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Old 05-06-2019, 12:54 PM   #4
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I donít think the form reflects the final shape and size.
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Old 05-06-2019, 01:27 PM   #5
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I saw similar chocks installed on a North Pacific (forget the length) a few years back; the owner felt that they did improve stability. They had been installed by Roy Brown of Independent Shiprights in Coombs.
Judging from how they looked (the boat was in the water) I would think that they would have significant forces acting on them while in slings.
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Old 05-06-2019, 02:09 PM   #6
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There are many gillnetters in this marina that have similarly installed chocks. The yard is quite experienced in raising boats with chocks.
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Old 05-06-2019, 03:34 PM   #7
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Rebel on his NP43 "Rogue" had them installed a couple years ago. If I recall, he reported no issues with the travel lift.
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Old 05-06-2019, 03:54 PM   #8
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Quote:
Originally Posted by JDCAVE View Post
This vessel is on the hard beside my vessel. It is owned by a former commercial fisherman is getting rolling chocks.

Attachment 88256

Attachment 88257

Iíve watched this FRP guy install these before on commercial vessels. He will lay down a skin of FRP, then glue down pieces of foam, then complete layers of FRP over the foam.

Jim
Could you take some measurements of the chocks when they get to the final shape? I have been thinking about them on my boat but no one around here has any experience doing them. A 39í is close to my size at 41í so the correct size may be close. Also can you ask what layup they are doing and document that?
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Old 05-06-2019, 03:56 PM   #9
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Jim: I know you donít want to hear this but hopefully youíll be there long enough so you can post pictures.
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Old 05-06-2019, 06:45 PM   #10
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Jim: I know you donít want to hear this but hopefully youíll be there long enough so you can post pictures.

Now then! Youíre just trying to make this poor little office boy feel inadequate!

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Old 05-06-2019, 07:42 PM   #11
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If I saw somebody install these things on a boat I’d suspect there’s something wrong w the boat design or the owner is afraid of common boat movement.
At the least I’d be observing that production boats don’t have these fins.
Or perhaps I’d take the person out on my boat that really does roll and maybe he’d think there was nothing wrong w his after experiencing mine.
And maybe a person feeling the need for rolling chocks should try out a wider boat and consider selling theirs and buying a more stable boat.
Lastly the chocks may not be very appealing to the eventual next buyer.
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Old 05-06-2019, 08:07 PM   #12
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Hi Eric,

Not many boats have an appealingly curvaceous bottom and pert arse end like your boat.

I figure rolling chocks go onto sharp chined boats to stop the abrupt stop and start to each 'snap' roll.

Lots of boats have rolling chocks here.
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Old 05-06-2019, 08:55 PM   #13
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MurrayM,
Interesting .. must be a Canadian thing. Don’t remember any from Alaska. There probably have been some but I don’t recall them. Seen some bulbous bows though. I always wondered if the’d capsize on a big beam sea tripping on the chocks. Never heard of it happening though.

They could conceivably produce a boat that gets blown downwind in the bow as the chocked chine may be resistant to yawing. And many boats have that tendency anyway so adding to an already imbalanced and undesirable trait .......
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Old 05-07-2019, 12:12 AM   #14
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Maybe when fitted they will be more vertical than horizontal.
A boat I inspected here, a Clipper40/PT41, had them fitted midships,and later a second set well aft was added. This one has them extending midships to transom. At that point, would they impede turning the boat? I get the anti roll idea placed midships, less sure about having them way aft. This is the second aft set, there could be good reason. What is it?
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Old 05-07-2019, 02:34 AM   #15
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"... I’d be observing that production boats don’t have these fins..."
Production boat just often propose ....Naiad, Wesmar etc fins :-)


"...theirs and buying a more stable boat..."
When you wrote "stable" is it for stability ?


Because sorry but you could have a boat with great stability how roll hard and one we poor stability you feel more comfortable...
For example if you compare the stability of a ferry slow motion not great stab and for example a "minťralier" feed with steel "minerai" great stab but hard motion (some was even damaged !)
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Old 05-07-2019, 05:48 AM   #16
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Folks with a unique bottom simply need to mark the hull,or deck, Sling Here.
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Old 05-07-2019, 10:16 AM   #17
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It would really helpful if some owners took measurements before and after to quantitatively measure how effective they are. There are all sorts of apps for smart phones that could be used.
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Old 05-07-2019, 11:52 AM   #18
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We doing that

Quote:
Originally Posted by makobuilders View Post
It would really helpful if some owners took measurements before and after to quantitatively measure how effective they are. There are all sorts of apps for smart phones that could be used.

On our long-cours.62, not to increase the stability but to make a quicker damping (sorry I don't know if it is the right word )
The length was around 4m (little more) and the high 280 mm, after fitted her we don't note a significant change in the speed/consumption. it was our principal question because the position and drag of this type of appendices could not be good at each speed (the "wave" generated by a hull change for each speed and the flux of the water on the hull also is not similar at 5 kts or at 10kts).
After that the feeling underway with wave on the beam seem better , but in the same time, we fit the ...mast. And we don't know the proportion on the change done :

-by the increase of inertia made by the mast; how many percent
-by the volume of the water "pushed" by the lateral extent; how many %
and also the reduction of the stability done by the weight of mast, boom, rigging.
From the beginning 2002 our rolling period change from around 2 sec to around 3sec.(2017) and it is more comfortable. note the lateral extent don't change the rolling period but by volume of water they must "push" when the boat want roll : delay the start and the damp quicker.


to get an idea of the counter force made by this thing ,look how much they will move for (for example) 5į, check the volume of water "pushed" at say to m from the axe you get one idea at zero speed, after you also have a change at speed....I am not really clear

It is an empiric way to get an idea ...
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Old 05-07-2019, 01:50 PM   #19
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I believe the sling lift operators add blocking to avoid pressure on bilge keels. I'm assuming that would be the case with these as well.
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Old 05-07-2019, 09:44 PM   #20
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I have observed that the greatest amount of negativity regarding 'rolling chocks' their appearance, practicality, and effectiveness appears to sprout forth from those that have little to no practical experience of the before and after results.
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