Pivot point of bow thurster
- Thread starter stinson
- Start date
- Joined
- Aug 19, 2014
- Messages
- 547
- Fluid Motion Model
- C-24 C
- Non-Fluid Motion Model
- Cal 2-25
- Vessel Name
- S/V Saylee
- MMSI Number
- 338124769
Hi Jim,
I know this is going to sound a little vague, but it will rotate around the vertical axis at the center of mass if it is stationary. Essentially it will rotate around the point where the overall weight of the boat balances. That will be a bit different for each boat due to everyone carrying a slightly different loadout with personal equipment, fuel, water, etc. If you want to get an idea what that point is on your boat, just maneuver to an open area where you can do a few complete 360s, bring the boat to a halt, push the bow thrusters in one direction, and the stern thrusters in the other to get the boat to rotate. You will then be able to see approximately where the point is around which the boat wants to rotate.
Now, to answer a bit more specifically for the bow thrusters, if you are moving either forward or aft, that balance point mentioned earlier will appear to move, as the hull moving through the water adds some stabilizing force. It won't be much though. For example, sometimes in tight spaces I will use the bow thrusters when moving the boat in reverse. The bow thruster will act like a rudder at the bow and will move the bow left or right, with the pivot point a bit closer to the stern than normal. It's really something you need to try and see how it works for you with your loadout though. Hope this helps.
Cheers,
Ralf
I know this is going to sound a little vague, but it will rotate around the vertical axis at the center of mass if it is stationary. Essentially it will rotate around the point where the overall weight of the boat balances. That will be a bit different for each boat due to everyone carrying a slightly different loadout with personal equipment, fuel, water, etc. If you want to get an idea what that point is on your boat, just maneuver to an open area where you can do a few complete 360s, bring the boat to a halt, push the bow thrusters in one direction, and the stern thrusters in the other to get the boat to rotate. You will then be able to see approximately where the point is around which the boat wants to rotate.
Now, to answer a bit more specifically for the bow thrusters, if you are moving either forward or aft, that balance point mentioned earlier will appear to move, as the hull moving through the water adds some stabilizing force. It won't be much though. For example, sometimes in tight spaces I will use the bow thrusters when moving the boat in reverse. The bow thruster will act like a rudder at the bow and will move the bow left or right, with the pivot point a bit closer to the stern than normal. It's really something you need to try and see how it works for you with your loadout though. Hope this helps.
Cheers,
Ralf
Brian98133
Well-known member
- Joined
- Dec 23, 2019
- Messages
- 213
- Fluid Motion Model
- C-242 C
- Vessel Name
- TUGether
As Ralph says, it's definitely something you will want to practice. I have found that in addition to loadout, the things I have to take into consideration are wind and current.
Since our 23's don't have stern-thrusters (unless it's an option I didn't know about), finding the pivot point is a bit more difficult in that it takes quite a bit of usage to make the boat do a complete 360 which may unnecessarily tax the thruster and drain its battery.
Since wind and current, in my case, cause the pivot point to be far astern of the actual hull, I found it best to just learn and acknowledge its limitations. For instance, with a 10 knot breeze hitting abeam starboard, using the thruster to get the bow to move to starboard (into the wind) is almost fruitless. At best, it will help correct an otherwise perfect approach angle if not for the wind. For this reason, in this case I would not approach a dock parallel and expect that the thruster will keep the bow parallel to the dock. I have found that it's just not 'that' powerful.
This is my first boat with a thruster, so it took a lot of practice to figure out how it works best for me. I literally spent an hour in a marina (off-season made it easy to find a spot in which I was not a spectacle! :lol: ) going in and out of a slip until I had a more comfortable grasp of how I will use the thruster. I've never tried to determine the pivot point, because it shifts drastically in different situations.
In perfect conditions (no wind, no current), I would guesstimate the pivot point to be roughly the center of the cockpit. But I rarely have perfect conditions in the PNW :mrgreen:
Since our 23's don't have stern-thrusters (unless it's an option I didn't know about), finding the pivot point is a bit more difficult in that it takes quite a bit of usage to make the boat do a complete 360 which may unnecessarily tax the thruster and drain its battery.
Since wind and current, in my case, cause the pivot point to be far astern of the actual hull, I found it best to just learn and acknowledge its limitations. For instance, with a 10 knot breeze hitting abeam starboard, using the thruster to get the bow to move to starboard (into the wind) is almost fruitless. At best, it will help correct an otherwise perfect approach angle if not for the wind. For this reason, in this case I would not approach a dock parallel and expect that the thruster will keep the bow parallel to the dock. I have found that it's just not 'that' powerful.
This is my first boat with a thruster, so it took a lot of practice to figure out how it works best for me. I literally spent an hour in a marina (off-season made it easy to find a spot in which I was not a spectacle! :lol: ) going in and out of a slip until I had a more comfortable grasp of how I will use the thruster. I've never tried to determine the pivot point, because it shifts drastically in different situations.
In perfect conditions (no wind, no current), I would guesstimate the pivot point to be roughly the center of the cockpit. But I rarely have perfect conditions in the PNW :mrgreen: