Public Discussion Forum

Now for some interesting stuff. We are retired fishermen from the Pacific Northwest. Albacore, Salmon, Halibut, Spot Prawns and Dungeness Crab. So we are accustomed to robust and stable vessels. We took Calypso out for a shake down trip in February to get familiar with her. We found that we need more stability for slow speed and when not underway. The active fins will not be adequate for what we are looking for I feel. We have installed 2 sets of “Rolling Chocks” on our boats and I know of over 400 more sets mainly on commercial fish boats. But lately recreational boats have been trying them with great results. The great thing is they are passive. They don’t require any power and they work whether underway or stopped.

The most common way they are described after they are installed is that they are a “game changer”.

is

This is really quite fascinating! Can you expand a bit more on design and install time/cost?

thanks for sharing!

-Rick

The last set I put on was five years ago here on Vancouver Island. I didn’t do the work and all in was $15,000 for material and labor. They were on a 50 foot OA Mark 1.

So these ones will be a bit longer, but I’m gonna do the work myself with one fibreglasser helping me. So we’ll see how much they end up costing. I plan to do the work at Boatworks in Coomera. The design is very simple as you can see. It just creates a lot of surface area that that water has to pass over. This will be a good experiment as I will put these on and it looks like I’ll be travelling with another Selene 59 the Ariel and we’ll get a direct comparison.

Kimball,

This looks interesting. What are the pros and cons? Can you use a sling with rolling chocks like this?

Richard Nye

Untethered, 57-22

https://forecast.predictwind.com/tracking/display/MV_Untethered/

Agree, it does look interesting and I read about a couple of North Pacific boats that put these on with reported good results.

I am curious what Dylan/Howard think of this and impact on the designed performance of the boat.

I googled rolling chocks after the first post and did some reading. One scholarly article was very emphatic about terminology and stating this is NOT Stability. In fact, they encouraged consultation with Naval Architects to ensure whatever you are pasting to the hull does not impede stability.

Corey
Sent from my iPhone

Yes, I think I remember seeing that article a while back when I was putting that set on the Grey Pearl; my OA 50 Mk 1. I don’t get caught up in the terminology. I’ve just been on boats with and without them over the last 50 years. Ron Burchett designed my first set on a commercial offshore troller about 35 years ago.

I’ve got him working on these as well. I have nothing to lose. It’s just fiberglass. I think Howard and Dylan will be very interested.

The only difference this time is the existing active stabilizers. I don’t want to take them off. So we gotta figure out how to fit the rolling chocks on the hard corner above the stabilizer fin or create a gap at the fin.

There are some examples of large vessels and they refer to them as bilge keels. But they are smaller and down low. When I asked Ron Burchett about these being so high on pleasure boats cause the hull is so shallow, he says that’s why they work so well. They’re up high and off to the side that gives you the lever.

During the development stage, there was some of that. Not slapping, but air would be trapped, which would make a sound. That was corrected by moving them aft. But those were under very extreme conditions.

Having said that has anyone ever experienced filling the bow on the Selene 59?The scuppers seem a little small. As well as the walkway on the starboard side only has one I think, up forward. We are a wide body.

Our King Air 200 (airplane) had a yaw damper that was required for flight. They were prone to fail so somebody came up with aft strakes, which look like bilge keels for the back of an airplane. With them installed the yaw damper was no longer required. They worked perfectly and make the plane better in pretty much all regards.

For this install, I’m wondering about rubbing against the dock pilings since they sit outside of the existing rub rails.

Dan and Bethany Moore

Blue Phoenix - 2008 Selene 59-17

That sounds quite similar for sure. Most hulls curve in enough. When you hang a plumb bob off the side it’s quite surprising how far they come in. So I’ve never seen a set sticking outside.

I've long considered adding Bilge Keels / Rolling Chocks (not a term I've ever heard), as they seem an obvious addition to active stabilisers.

Phil on Asante 5334 is spot-on. Bilge keels are fitted to almost all steel commercial ships comprising what's known a 'Bulb Bar' set at 45deg off the turn of the bilge so as not to extend below the flat bottom or outside the side plate so is protected by the hull in both planes.

I haven't read the article Corey mentions but I think that they are obviously very effective in dampening rolling, just as stabilisers or paravanes are when moving slowly or when anchored. Corey's mention that they may affect 'stability' may be referencing extreme rolling conditions when the boat is reaching the point of no return. I cannot imagine that they would be detrimental to dampening the rolling in 'normal' conditions.

A steel ship has ample strength in the turn of the bilge with welded knee braces supporting the bilge keel on every frame.

Though the Selene's are very strong with thick hull I would be very concerned about the stresses on the hull from the bilge keels. I hope someone can give guidance on adding bilge keels to an existing hull without internal modification or on the need to add 'doubler plates' on the outside to spread the load.

The fact that the bilge keel sticks out further than the vessel side would be a problem for fenders mooring on a wall but I wouldn't have any issue at the floating pontoons we use.

My big concern and one I hope will be addressed by Kimball is that on the photo it looks like the aft lifting strop is over the bile keel. It's obvious that the loading onto the lever of the keel would be extreme. The likelihood of breaking the keel is huge. If it should break the resultant edges would certainly be in danger of cutting the lifting strop.

I addition the strop has a minimum bending radius that looks to be massively exceeded as it passes through 90deg. It's a classic point of failure that a strop is over bent and parts at that point. It would never be allowed in 'normal' crane operations.

Please tell me the aft strop is not over the keel as it seems in the photo?

The solution is easy. Remove the bilge keel back to original hull for 2 x the width of the strop. This is very common on construction ships that operate winches over the side and I'm sure has minimal affect on the efficiency of the bilge keel.

Otherwise I congratulate Kimball on a project that I'm sure manufacturers have considered during design but might be able to learn from real life experience.

Best

Garry

(40 years experience Subsea Construction Heavy Lift Vessels, Diving and ROV)

4333

Maybe making a gap for the strop is actually a feature. It’s hard to screw up the lifting point if it physically can’t be anywhere except where the bilge keel break is.

Luckily I’m not an engineer so I can blissfully ignore all the strength questions and hope someone else has the wherewithal to figure that math out.

Dan and Bethany Moore

Blue Phoenix - 2008 Selene 59-17

All good points. I’m impressed. I’m lucky I’ve been around them for decades and seen them work in extreme conditions. We joked on the first set we installed, we were gonna write on them “time to go in”. Because we figured that would mean it was too rough. We would see them once in a while and laugh as we’re hanging over the side, long lining for halibut.

We have a commercial boat builder doing the tried and true method of just building them way stronger than you need. In addition, have the mathematician that backs him up.

For more research. Look at Roy Brown, Independent Shipwrights, , Coombs, BC, Rolling Chocks and Ron Burchett, Burchett Marine, Ladysmith BC. I hate to admit it but use AI.

I missed one point. Roy has put them on seine boats up to 200 tonnes And they’re being lifted with travel lifts.

The Rolling Chocks will add strength to the hull. The fibreglass layers extend about 12 inches or more (depending on the size vessel) above and below the chocks plus the “RC” itself which creates a huge stringer down the side of the hull. The hull is way stronger, not weaker,

Ahh, excellent picture. They do sit in much further than I thought. Thank you.

Dan and Bethany Moore

Blue Phoenix - 2008 Selene 59-17

Hello Richard,

I don’t know of any cons. You just make them really strong so they can handle the slings.

Roy Brown up here from Coombs has put on over 400 sets. All the way up to big Seine boats 200 tonnes.

In the deep sea industry these appendages are known as ‘Bilge Keels’, most large merchant ships today are fitted with some form bilge keel to minimize rolling. As a previous post these have previously been standard on North Pacific yachts as an alternative to active stabilizers. In relation to slings you can ensure sufficient strength, but alternatively they do not need to be continuous so in theory you could leave gaps to facilitate slings.

Phil Davies

Asante 5334