Bilge Keel - Rolling Chock installation

[socalrider]

Interesting thoughts on combining methods. Those gyros go up quickly in price, weight, and power consumption with size, so I wonder if you might be able to spec a size down with the bilge keels. That seems like a nice combination.

 

[Kit_L]

Agree, @socalrider: we used the same thinking when we downsized the paravanes on Annika-J. We downsized the area by 30% and the tip weight by the same, making them much easier and safer to handle in a sea. We wanted roll reduction, not cancellation, and this was achieved.

 

[Insequent]

Interesting thoughts on combining methods. Those gyros go up quickly in price, weight, and power consumption with size, so I wonder if you might be able to spec a size down with the bilge keels. That seems like a nice combination.

Anyone contemplating "going a size down" should take note of a friend's comment below. He had a boat similar to mine with Naiads and was accustomed to stabilisers doing their job properly.

Back on the gyro: it does a great job at anchor and in mild sea conditions but its effectiveness falls off rapidly in seas that the NAIADs would make easy work. I have now looked up the specs for the particular model I have and it is clearly below the recommended size on both vessel length and weight. Super annoying, as there are two models above it, both with identical footprints in all 3 dimensions, that have respectively 30% and 50% more torque. I called up the MD of the Australian distributor and after a bit, he told me they had recommended against this model and advised the 1st owner to get the next model up (32% more torque, same footprint) but he didn’t take their advice.

At this point I think he'll live with it as he does not intend long passages on the new to him (planing) boat. It might be OK to go with the smallest recommended size gyro, but unwise to go a size down from the reccommendation.

 

[dannc]

Interesting thoughts on combining methods. Those gyros go up quickly in price, weight, and power consumption with size, so I wonder if you might be able to spec a size down with the bilge keels. That seems like a nice combination.

I suppose one could but I would be want to have the right size gyro and use the bilge keels as extra. The other advantage with bilge keels, along with paravanes, is that they work at anchor and don't require power. So, a gyro and bilge keels could be an interesting solution.

Later,
Dan

 

[dannc]

Anyone contemplating "going a size down" should take note of a friend's comment below. He had a boat similar to mine with Naiads and was accustomed to stabilisers doing their job properly.

Back on the gyro: it does a great job at anchor and in mild sea conditions but its effectiveness falls off rapidly in seas that the NAIADs would make easy work. I have now looked up the specs for the particular model I have and it is clearly below the recommended size on both vessel length and weight. Super annoying, as there are two models above it, both with identical footprints in all 3 dimensions, that have respectively 30% and 50% more torque. I called up the MD of the Australian distributor and after a bit, he told me they had recommended against this model and advised the 1st owner to get the next model up (32% more torque, same footprint) but he didn’t take their advice.

...

I wonder if one can have too much stabilization, ignoring size, weight and power requirements.


Later,
Dan

 

[Simi 60]

Anyone contemplating "going a size down" should take note of a friend's comment below. He had a boat similar to mine with Naiads and was accustomed to stabilisers doing their job properly.

Back on the gyro: it does a great job at anchor and in mild sea conditions but its effectiveness falls off rapidly in seas that the NAIADs would make easy work. I have now looked up the specs for the particular model I have and it is clearly below the recommended size on both vessel length and weight. Super annoying, as there are two models above it, both with identical footprints in all 3 dimensions, that have respectively 30% and 50% more torque. I called up the MD of the Australian distributor and after a bit, he told me they had recommended against this model and advised the 1st owner to get the next model up (32% more torque, same footprint) but he didn’t take their advice.

At this point I think he'll live with it as he does not intend long passages on the new to him (planing) boat. It might be OK to go with the smallest recommended size gyro, but unwise to go a size down from the reccommendation.

On a hydraulic device with a "brain" I could well imagine it trying to compensate and overworking itself until the smoke comes out.

On a dumb device such as paravanes, it is far less dramatic.
It simply has less load and doesn't work quite as well as it could.

 

[Jeff F]

My understanding is that gyros are additive - a Seakeeper 5 can be swapped for two units - say a 3 and a 2 - with the same net effect.

I like this idea. There isn't a big difference in total cost, and it allows lower power draw when less stabilization is required. It also allows deliberate or inadvertent undersizing with the intent to add a second unit if required.

 

[Mambo42]

Anyone contemplating "going a size down" should take note of a friend's comment below. He had a boat similar to mine with Naiads and was accustomed to stabilisers doing their job properly.

When I decided on the stabilizers I actually went one size up. Most stabilizers are calculated with 10 kts as a reference speed and since I am doing only 5 - 7 kts I am below that reference speed. The higher the speed the smaller the fins can be, so likewise, the slower your speed the larger the fins should be.
Officially I should have the stab 20 for my size boat, but decided for the stab 25 and must say am happy with it.
Currently lying on anchor in a bay near Yalikavak, Turkey, have the stabilizers on in flip plus night mode, which means they will prevent the boat from going over the anchor and at the same time use less energy. The total draw at this moment is about 5 Amps at 24 V, I can live with that and the boat is lying rock solid in the water, won't move at all. The stabilizers only work when necessary, unlike a gyro that needs to keep on spinning all the time and thus draws massive amounts of electricity.
There is no way you can run gyro's off your battteries, you will simply drain them and that means running a generator 24 hours per day. If you calculate the fuel usage that is about 1 ltr of fuel per hour, which means 24 ltrs per day which is about 6 gallons. Over a period of one month that is 180 gallons. I can also do 300 - 450 nm of sailing with that fuel and must say that I rather do that.
While we are underway the electricity is provided by the solar panels and by the alternators, but even then I don't go over 40 Amps at 24 V and that is when it is already quite rough out there.

The one negative item is that you cannot combine bilge keels with stabilizer fins. I had the keels, they did not work at all for me, but in order to get the fins on and have unrestricted water flow over them the keels had to be removed.

 

[Hippocampus]

When I decided on the stabilizers I actually went one size up. Most stabilizers are calculated with 10 kts as a reference speed and since I am doing only 5 - 7 kts I am below that reference speed. The higher the speed the smaller the fins can be, so likewise, the slower your speed the larger the fins should be.
Officially I should have the stab 20 for my size boat, but decided for the stab 25 and must say am happy with it.
Currently lying on anchor in a bay near Yalikavak, Turkey, have the stabilizers on in flip plus night mode, which means they will prevent the boat from going over the anchor and at the same time use less energy. The total draw at this moment is about 5 Amps at 24 V, I can live with that and the boat is lying rock solid in the water, won't move at all. The stabilizers only work when necessary, unlike a gyro that needs to keep on spinning all the time and thus draws massive amounts of electricity.
There is no way you can run gyro's off your battteries, you will simply drain them and that means running a generator 24 hours per day. If you calculate the fuel usage that is about 1 ltr of fuel per hour, which means 24 ltrs per day which is about 6 gallons. Over a period of one month that is 180 gallons. I can also do 300 - 450 nm of sailing with that fuel and must say that I rather do that.
While we are underway the electricity is provided by the solar panels and by the alternators, but even then I don't go over 40 Amps at 24 V and that is when it is already quite rough out there.

The one negative item is that you cannot combine bilge keels with stabilizer fins. I had the keels, they did not work at all for me, but in order to get the fins on and have unrestricted water flow over them the keels had to be removed.

Having now lived with a SeaKeeper over a couple of years actively cruising have found the following.
We’re on the US east coast so have the opportunity to pick either the side of the bay, river, coastline which has no or minimal fetch. So to date haven’t needed any form of stabilization at rest. Over 75-85% of the days while underway the SeaKeeper is off. Given it takes awhile to wine up we decide the night before whether to turn it on in the morning. We’ve seen nothing over 6’. Almost all wind waves or chop.
If I had my prior cruising program where we anchored frequently in open roadsteads with swell and wind waves then would need some form of stabilization at rest. Choice would probably be flopperstoppers not fish. My understanding is they’re easier to deal with and often just one is sufficient. If I had Magnus then flopperstoppers would be the logical choice as there’s limited effectiveness for Magnus at rest if held still.
View stabilization as three separate problems. Safety so Gz and AVS and comfort quotient. Comfort underway. Comfort at rest. Different problems which may require different approaches .
Snap roll is very unpleasant. It can even cause you to lose your balance. So I think the acceleration and rate of speed of returning to level (angular velocity ) is very important to comfort and even safety. So yes you can have too much stability. However think this is more a function of hull shape, weight distribution and degree of form stability than anything to do with add on stabilization devices.

 

[dannc]

My understanding is that gyros are additive - a Seakeeper 5 can be swapped for two units - say a 3 and a 2 - with the same net effect.

I like this idea. There isn't a big difference in total cost, and it allows lower power draw when less stabilization is required. It also allows deliberate or inadvertent undersizing with the intent to add a second unit if required.

That is a very interesting idea if one has the room on a boat for two gyros, and the money to buy them.

Two would be a bit extra maintenance, but for the brand I was researching, it is minimal.

Later
Dan

 

[GB32Patience]

@ksanders Well done! Thanks for providing great images of your solution as built and the "roll test" is hard to argue with. So far, looks like best bang for the buck by far. Great solution.

 

[GB32Patience]

@ksanders Again, all this info very much appreciated. One question left.... the forward section of the "chocks" seem substantially built up in thickness relative to the aft/trailing section; looking almost 4-5" "thick at the forward end. Is this where straps may fall or simply just strengthening the forward edge structurally? Thanks!