Originally Posted by Lou_tribal
Considering the weight of the boat and its speed I donít 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.
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.
I returned 1.93 Lts / P.H @ 6Knts
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.
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.
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.
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.
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.