Rolling chocks ve Stabilizers

[Nomad Willy]

Murray,
Where are you going to put rolling chocks on a low deadrise SD w nearly vertical topsides? Have you seen chocks on a hard chine boat like yours?

The only way I see to do it is sticking straight out at about a 45 degree angle. That would raise hell w your fenders and be somewhat vulnerable structurally.

And then the forces on either chocks or stab fins will be quite high. I dono Murray I’d be inclined to fasten down my helmchair real well and get a seat belt or harness. I thought of having a strut braced helmchair pedestal too. My wife just sits sideways and closes drawers w her feet.

 

[Lou_tribal]

The only thing that would worry me is the way these are attached to the hull and the potential damaged in case of contact with something or when hauling out or due to applied forces. I mean when made at build time the support is "planned" but when retrofitted not the same game. Or like often I am totally wrong lol

L

 

[MurrayM]

Hi Eric,

Check out the photos here: Trawler Forum - View Single Post - Rolling Chocks make them on the cheap

Too many drawers for my wife to keep up with (Great image by the way!)

 

[MurrayM]

The only thing that would worry me is the way these are attached to the hull and the potential damaged in case of contact with something or when hauling out or due to applied forces. I mean when made at build time the support is "planned" but when retrofitted not the same game. Or like often I am totally wrong lol

L

Well, there are negatives to everything. These seem to be the least expensive way to reduce snap rolls and can slip through kelp.

Open to other suggestions *Gyro systems not an option*

 

[Lou_tribal]

Well, there are negatives to everything. These seem to be the least expensive way to reduce snap rolls and can slip through kelp.

Open to other suggestions *Gyro systems not an option*

No I am not negative and I find this very interesting and I clearly see the benefit of this on my baby, do not misunderstand me. Just wondering how this should be correctly fitted for it to be strong enough but not so strong that it would break the hull instead of being ripped off or broken without major damaged. Sorry if do not explain things well

L

 

[Sailor of Fortune]

Rolling chocks and bilge keels were always the same thing in my mind at least. I have never seen those west coast style with "vents" and wonder how they work.
There was a thread a while back about how these wouldn't be in the way of travel lift straps. Since that thread, the St Augustine Marine travellift has a standoff piece for hauling boats with these appendages. probably not coincidence that they were launching Expedition Trawlers for a few years that were built on site at the time

 

[AusCan]

Even with rolling chocks, I experience significant rolling in a heavy beam sea (up to 45 degrees). The earlier versions of this boat didn't have rolling chocks. I'd hate to be in rough water on them. My steading sails will reduce the rolling to a very comfortable level as long as there is 10+ knots of wind.


On the odd day after a big blow and the wind dies but the water is still rough, I wedge myself in the helm chair with my feet against the bulkhead to keep me in the seat. A seat belt would be handy.
My wife doesn't normally come out on the overly rough water, so I have to use latches on the drawers.


Lou - Hauling out isn't a problem with rolling chocks. They generally are only about half the W/L length and located mid-ship, so there is plenty of room for slings at either end.
I'm not sure how they affect the snap roll of a hard chined boat. Rolling chocks tend to be found on round bilge, soft chined boats. There may be a good reason for that.

 

[MurrayM]

No I am not negative and I find this very interesting and I clearly see the benefit of this on my baby, do not misunderstand me. Just wondering how this should be correctly fitted for it to be strong enough but not so strong that it would break the hull instead of being ripped off or broken without major damaged. Sorry if do not explain things well

L

We're good

 

[Sailor of Fortune]

rolling chocks are never going to deliver the same degree of dampening as flopper stoppers.
Auscan....Hauling out for a 30 Cuddles with rolling chocks may not be a problem, but a larger boat that requires 4 or 6 strap travel lift? Those boats (expedition type boats,or fishing vsls) are more likely to have issues.. Those are the type of craft that tend to have rolling chocks more than yours.

 

[Russell Clifton]

Just saw a 42 Grand Banks yesterday with rolling chocks that were installed at the place in Nanimo BC. He was in and out in three days. He said it usually only took two days but the bottom paint he uses needed 12 hours to dry. He said the travel lift sling will not be a problem. He had the 12" ones installed and they were about 2/3 the length of the boat.

 

[MurrayM]

Just saw a 42 Grand Banks yesterday with rolling chocks that were installed at the place in Nanimo BC. He was in and out in three days. He said it usually only took two days but the bottom paint he uses needed 12 hours to dry. He said the travel lift sling will not be a problem. He had the 12" ones installed and they were about 2/3 the length of the boat.

Did he mention what he thought of them?

 

[Nomad Willy]

Aus Can wrote;
“I'm not sure how they affect the snap roll of a hard chined boat. Rolling chocks tend to be found on round bilge, soft chined boats. There may be a good reason for that.”

Aus Can,
The reason is that when a beam wave comes apron a boat it lifts the side of the boat exposed to the wave. As the wave moves on it lifts the OTHER side of the boat. We’re talking about lots of lift due to the shape of the hull. And then when the wave moves on that side of the boat suddenly drops. And at the same time the other side of the boat is poped up with a lot of force.

Now think of a half-round shaped hull. Along comes a wave from the side and practically nothing happens. Outboard where the chine is on a hard chine boat there’s very little hull to lift one side of the boat. It may roll a small amount. But since there’s little hull to lift there is very little lifting force. And the weight of rounded hulls help dampen the roll movement.

So w a roundish hull form it takes very little force to right it. With a hard chine boat (especially a wide one) it takes huge force to reduce the movement (roll) and there’s only a little of the movement reduced. And the poles and rigging need to be very heavy.

Bottom line is that flopper stoppers on roundish bottomed boats are very effective and hard chined boats .. not so much.
A few hard chined boats have flopper stoppers and fewer skippers say they are effective. Flopper stoppers on a GB? I don’t think I’d even attempt it. But they probably work fairly well if the “fish” are big and the beam is narrow and the rigging and spars are stout.

Here are two pictures of Dixie II.
She has the rounded hull that is easily stabilized.
Notice the list created from extending one pole. If the same pole was extended on a GB you couldn't see the list. It's the lack of stability that makes this possible. The hard chine hull has too much lift at the hull sides (outbd). So the boats that are easily stabilized are the boats w less stability.

 

[klee wyck]

Klee Wyck and Libra both have appendages but I have not idea if they are bilge keels or rolling chocks. Actually, on Libra they hold the keel coolers so I suppose they are keel cooler keels....

Libra is a fair bit more stable to roll but I expect that is the cement poured around the tankage in the bottom of her hull leading to twice the weight for only 5 feet of extra length over Klee Wyck rather than the geometry of the appendage.

One photo of the small structures on Klee Wyck and a couple of the more vertical box keels on Libra.
Neither myself nor the yards I have used have been too concerned about how the straps affect these appendages. Perhaps a case of ignorance is bliss.....

 

[AusCan]

Aus Can wrote;
“I'm not sure how they affect the snap roll of a hard chined boat. Rolling chocks tend to be found on round bilge, soft chined boats. There may be a good reason for that.”

Aus Can,
The reason is that when a beam wave comes apron a boat it lifts the side of the boat exposed to the wave. As the wave moves on it lifts the OTHER side of the boat. We’re talking about lots of lift due to the shape of the hull. And then when the wave moves on that side of the boat suddenly drops. And at the same time the other side of the boat is poped up with a lot of force.

Now think of a half-round shaped hull. Along comes a wave from the side and practically nothing happens. Outboard where the chine is on a hard chine boat there’s very little hull to lift one side of the boat. It may roll a small amount. But since there’s little hull to lift there is very little lifting force. And the weight of rounded hulls help dampen the roll movement.

So w a roundish hull form it takes very little force to right it. With a hard chine boat (especially a wide one) it takes huge force to reduce the movement (roll) and there’s only a little of the movement reduced. And the poles and rigging need to be very heavy.

Bottom line is that flopper stoppers on roundish bottomed boats are very effective and hard chined boats .. not so much.
A few hard chined boats have flopper stoppers and fewer skippers say they are effective. Flopper stoppers on a GB? I don’t think I’d even attempt it. But they probably work fairly well if the “fish” are big and the beam is narrow and the rigging and spars are stout.

Here are two pictures of Dixie II.
She has the rounded hull that is easily stabilized.
Notice the list created from extending one pole. If the same pole was extended on a GB you couldn't see the list. It's the lack of stability that makes this possible. The hard chine hull has too much lift at the hull sides (outbd). So the boats that are easily stabilized are the boats w less stability.

Thanks for the great explanation, Eric.

Although I'm not considering paravanes, I am seriously considering flopper stoppers for when at anchor.
The amount of roll I get is not only related to the size and steepness of the swell, but also how the wave interval synchronizes with the boats natural roll time. When under power, just changing the angle of travel changes the wave contact interval, so it's easy to correct. At anchor its not so easy to fix.

 

[FF]

"I cannot imagine a fishing boat with a full hold and tanks being hauled by a travelift in anything short of an emergency,"

Sorta depends on the size of the fish boat,

https://marinetravelift.com/product/300c/

 

[Woodland Hills]

"I cannot imagine a fishing boat with a full hold and tanks being hauled by a travelift in anything short of an emergency,"

Sorta depends on the size of the fish boat,

https://marinetravelift.com/product/300c/

Big travelifts, I'll agree. What makes you think any of the commercial boats in the ad have full holds? Unless they kept the boat plugged into shore power and arranged some sort of water supply to the coolers wouldn't the catch thaw and rot?

 

[Rebel112r]

Ah, getting to be like, anchor thread. 7 times in straps being lifted and they have not fallen off yet. Most all weight by rear straps is on keel. Rogue currently anchored Galley Bay, Desolation Sound after 2, 45 I’m days with wind and 2-3 footer on stern, boat handler we’ll.

 

[dhays]

Ah, getting to be like, anchor thread. 7 times in straps being lifted and they have not fallen off yet. Most all weight by rear straps is on keel. Rogue currently anchored Galley Bay, Desolation Sound after 2, 45 I’m days with wind and 2-3 footer on stern, boat handler we’ll.

Thanks Dan. I was hoping you would chime back in given that you have the experience with the rolling chocks on Rogue. The photos of Rogue with the bilge keels has been very helpful to help us all visualize it.

BTW for the benefit of the rest of the crew, the North Pacific Yachts owner, Trevor Brice doesn’t discourage adding them to his boats. In fact, he has recommended it to some owners concerned about roll in certain conditions. Considering how careful he is with the reputation of his boats, I think that says a lot.

 

[MurrayM]

This is what I'm assuming our boat would look like with 12" wide rolling chocks, although this set looks pretty long. Think I would discuss with people doing the work to enlarge the chock to hull join area and thicken it as well...

 

[Woodland Hills]

It looks like it would protect the rub rail from contact with any pilings.

 

[Rebel112r]

Spell check, make me look like I can’t spell, probably correct. There were 2 Grand Banks having chocks installed this spring. Owner of one, I talked to in Bellingham a month ago. On North Pacific Boat’s, the 12 inchers do not interfere with docking, they 18 inch ones may, but fenders will negate the concern for these.

 

[MurrayM]

It looks like it would protect the rub rail from contact with any pilings.

...On North Pacific Boat’s, the 12 inchers do not interfere with docking, they 18 inch ones may, but fenders will negate the concern for these.

Here is a typical BC marina; low floating docks with bull rails...fenders make rubbing a non issue.

 

[Jaguar_Shark]

Revive this thread

Has anyone tried using long thin foils out each side for stability that can be deployed and retracted ?

I’m fixated on the idea that long thin “airplane wings” out each side of the beam can reduce the roll and absorb most of the energy in the flex of the foil

I see the old….4 years ago Volvo ocean race boats deploying 10’ long keel boards on the deep side and retracting the one on the high side

Thinking of trying this on my roly poly 50’ tayana trawler