Rolling Chocks make them on the cheap

Rolling Chocks - I based my design on those very pics on google and read a lot of articles about how the lobstermen of the PNW employed them on their boats.

Thought I would make some and just see for myself if they worked, better than the opinions of others that never had them.

I went to Bunnings and bought a sheet of marine ply 25mm thick, then
off to the fiberglass supplier for some matt and resin. Cost around $ 200 including all sundry extras like acetone /sandpaper pads /rollers /etc.

1. I needed to make a template of the hull curve where I intended fitting the chocks. Just go to nearest white goods distributor and get a cardboard box from a fridge or whatever. Straighten it out and brace it with a rod and start cutting till it matches your hull curve.

2. Lay the finished template over the sheet of ply and get a circular saw and start cutting - it should follow the inside curve as long as the blade is not a giant.

3. Just trim any dags off with a hand held surform on the inside curve and round the outside edges nice and smooth. Get your hole saw and put a whole lotta holes along the outside edge - this is important - this is where you keep your bottles of beer LOL nah not really !!!
These holes are most important to release some pressure on the chocks - kindda like baffles and gives the boat a real nice easy ride. I put mine in after the initial seatrial and found they just finished off the ride perfectly.

4,5,6 There they are fitted. I just tacked them on with some rapid hardening glue first.
I was worried about what would happen to my hull if I happened to hit some submerged object so I just used ONLY 2 layers of fiberglass matt to attach them. I figured that making them sacrificial would be best in the event of some unintended contact.

I put them high up on the side of the hull, to act as hydrofoils and give a bit of lift also - maybe ?? They are parallel with the water line at the leading and following edge and at 90 degrees to hull.

In summary rolling chocks are a poor man's heaven when motoring and
along with employing flopper stoppers when anchored the combined effect is Bliss.

Very clever !! Thanks for sharing!

Very shapely.

Have you seen snotty conditions yet? Appreciable difference? If these work as you expect, will you install a more permanent set? What are you going to do with the $39,800.00 saved from not having a more technically complex stabilization system installed?

I think he’ll just keep what he has.

Perhaps sand and apply more FG for all purpose integrity.

I’m wondering about the holes. Is it an Oz thing? First anchors and now chocks. I thought of that on my rudder as sort-of an anti-stalling device. My rudder works so well I didn’t do it.

How well do you track your fuel useage ? Have you noticed a difference ?

Are the holes to reduce stress on the fin to hull joint ?

The increased fuel consumption will be due to the increased wetted surface. Also one dosn’t know exactly how (direction) the water flows along the hull. All those variations from reality will increase fuel burn too. But all of it won’t amount to much .. very very little in fact.

The only think I don’t like about rolling chocks is probably all in my head. That is that sideways on the face of a wave I see the possibility of the chocks resisting movement well below CG could cause the boat to “trip” on the outboard chock and capsize the boat.

Don’t panic bogranjak1 as I’ve not heard of it happening and there are a lot of (quite a few anyway) of boats w these bilge keels and never have I heard of a capsize. There is at least one Willard w bilge keels on the Willard group on yahoo. WBO

For anyone doing this on a non trailerable, make sure it doesn't interfere with travel lift straps.

Looks like all those holes would cause considerable turbulence, why not just make the fins narrower?
Also how did you manage to seal and glass all those exposed ply edges in the holes?

Simi 60 said:

For anyone doing this on a non trailerable, make sure it doesn't interfere with travel lift straps.

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There have been a number of North Pacific 42/43s with them installed. They are hauled out and them splashed with travel lifts.

Considering the weight of the boat and its speed I don’t think that neither the turbulence nor the drag will of these will make much difference. For sure this will increase drag, for sure this will increase fuel burn but on what figure? 0.1 gal/h? If result on rolling is effective this will make very little difference.

L

They would have much less drag than paravanes and possibly less than active fins.

Mine don't have the holes, but are much thicker, probably 50mm (2") thick. They are similar in length and position fore & aft, but maybe a little deeper and closer to the keel.

Eric: I don't think they would be much of a "trip" hazard when sliding down a wave. I'd be more concerned of a deep gunwale causing a trip & capsize with some boats. Its tough to say with so many variables.

dhays said:

There have been a number of North Pacific 42/43s with them installed. They are hauled out and them splashed with travel lifts.

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I never said they couldn't be lifted with a travel lift, what I said was make sure the rolling chock positioning doesn't interfere with the travel lift strap

Lou_tribal said:

Considering the weight of the boat and its speed I don’t think that neither the turbulence nor the drag will of these will make much difference. For sure this will increase drag, for sure this will increase fuel burn but on what figure? 0.1 gal/h? If result on rolling is effective this will make very little difference.

L

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Lou,
Nimiane weighs only 1500kg and only ever sniffed fuel @ an estimated 2 Lts/P.H. @ 2000 RPM.

After fitting the rolling chocks I did a very detailed analysis of fuel consumption over 250 hrs. I increased the RPM of all but a little of the motoring to 2250 RPM (66% of my max. H.P. rating of 20 H.P. @ 3400)
which brought the hull speed up to 6 knts for the testing.

results :-
I returned 1.93 Lts / P.H @ 6Knts

benthic2

The rolling chocks work better with holes in them. I tested the boat both before and after holes were cut.
For this conclusion I looked for a beam sea with the roughest conditions. We get 20knts S/W every afternoon so was easy to test.
The boat became more stable as I increased speed, as I approached hull speed around 7plus knts (3200 RPM) the boat felt like it was on rails. I don't like motoring at this RPM. I found 6knts was quiet - engine noise wise and stability was excellent.
My opinion is that my boat was stabilized by at least 50% over previously experienced conditions.
I think rolling chocks are only of use for boat owners with a full displacement hull and smooth clean transom.
Boats for example like Willard / Kadey / etc that have a nice clean stern.
A semi displacement boat towing around half the Indian ocean with it's big fat arsed transom will get negligible results.

Simi,
As commented by dhays...There are lots of pics on T.F. with big boats getting lifted out with the straps over the rolling chocks. Given that these chocks are more triangular in shape so more robust I does not seem to worry the owners. Also the positioning of the chocks needs to be placed at the widest point in the hull usually amidships so the straps mostly will be either side.

Kapnd,
Rolling chocks were coated with several coats of resin before being fitted to seal them against water ingression. After I decided use the hole saw and put holes in them (for the placement of empty beer bottles ...joke !!) I just trailered the boat and cut the holes then used resin with a brush over a few days giving them a good seal.
The holes are intended to create a baffle effect - this smooths out the action of the rolling chocks when the boat gets hit by a beam wave. It really does work I assure you, I was so pleasantly surprised myself but had read many articles where this very subject of holes in the rolling chocks was discussed.

Nomad Willy
I did put Nimiane through a pretty comprehensive seatrial after fitting these chocks. As well as beam seas I did consider exactly what you are concerned about - A FOLLOWING SEA - I felt no skittering or tripping as I surfed down the face of following seas @ 9.5knts ( well over hull speed)
I fact the boat was equally stable in beam and following seas.

MurrayM
I'm not sure what to do with the $39800. I would like to go to Eric's part of the world and buy a Willard and go to Alaska. Do you think he would let me borrow his boat for a few months - maybe a carton of Aussie beer in payment

Keep the questions and comments coming guys, rolling chocks are purely a 'Poor Mans' means of stabilizing his boat at very little cost.
The combination of rolling chocks along with the employment of 'flopper stoppers' when anchored for the night one can obtain a state of total Bliss.

Thanks bogranjac1,
HaHa perhaps I should put them on Willy but I have many more projects to do first. And I’m still playing w anchors. Your feedback makes me feel more comfortable.

B: Sounds like the best $200 project on the forum. Well done!
Your results regarding the holes are really interesting.

One more question - Are both chocks parallel? I'm read that some are built slightly pigeon-toed.

AusCan,
I suspect it may vary from boat to boat re water flow along the hull. Or it could be like wheel alignment on a car.

I’ve thought holes behind the leading edge of rudders may make them more stable and perhaps more powerful.???

AusCan said:

B: Sounds like the best $200 project on the forum. Well done!...

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bogranjac1 said:

MurrayM
I'm not sure what to do with the $39800. I would like to go to Eric's part of the world and buy a Willard and go to Alaska. Do you think he would let me borrow his boat for a few months - maybe a carton of Aussie beer in payment.

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Good plan. If you do, ensure enough time to wander off the Inside Passage treadmill...there are some pretty special places off the beaten path. Oh, and there are some fine Canadian beers to enjoy on your journey

bogranjac1,
Willy could use some exercise but I’ve never loaned out a boat in my life. Don’t recal any opportunities either. Willy likes the compliment though.

Actually you must think I’m still in Alaska. Moved to Washington State 5 years ago so “Eric’s world” probably isn’t what you think.

Simi, Third out and in with chocks installed. Don’t worry about it any more. They keep the rear straps off the hull sides, don’t have to touch up a fresh polish job.

Wow.
I don't know for sure but I would have thought Australia, being the over regulated country it is, would have some sort of regs in place prohibiting that due to point loading the straps.

Here, I've never seen them intrude into strap space, always mid ship install like in this pic.
I assumed it was for lifting reasons because I believe, like parravanes, they would work better in the rear third of the hull.

I usually see blocks used with travel lift straps and rolling chocks (bilge keels). They take the stress off the chocks and keep the straps away from topsides. Carpet covered of course.

Rebel, on your NP42 did you have a naval architect design the bilge keels? What difference in handling do you see at rest and underway?

Sailor of Fortune said:

I usually see blocks used with travel lift straps and rolling chocks (bilge keels). They take the stress off the chocks and keep the straps away from topsides. Carpet covered of course.

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Are multiple divers holding blocks in place needed for the lift out?

Simi 60 said:

Are multiple divers holding blocks in place needed for the lift out?

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No, they are set on straps and positioned by single diver. They have lines to keep them attached to straps. Same way blocks are used to keep slings from "pinching" prominent rub rails. Blocks come up with slings after boats launched and backed away from travel lift. its usually only one set of slings thats an issue (if at all).

The fellow that installed them has put them on, he says thousands of boats. No naval architect involved with these. Independent Shipwrights, Coombs BC, Canada did the work. They work well, no downside, other than some slapping when beam on to larger waves. Cheap to install. Maybe 10 North Pacifics have them. I consider it money well spent.

Simi 60 said:

Wow.

Here, I've never seen them intrude into strap space, always mid ship install like in this pic.
I assumed it was for lifting reasons because I believe, like parravanes, they would work better in the rear third of the hull.

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The most effective placement for them on the hull shown (full displacement) is at the widest point of the hull.
Has little to do with lift straps

Very cool. Thanks for posting this.

I've read that people notice a marked difference in turning at slow speed after having rolling chocks installed, such as when making a 90 degree turn from the fairway and entering a slip bow first. They mention that their boats don't "skid sideways" as much during the turn anymore, but feel more like they are "on rails". This true?

I have noticed, nothing different in the slow speed handling of the boat. Other installations may be different.