Graupner Bow thruster

[Massey]

Now that I am building my Tito Neri I have some questions about the bow thruster.

What is the best way to power this? Would it work good as an on/off device or should I have proportional control of it. If porportional control is the way to go where can I buy an ESC for it that has equal forward and reverse? Also what voltage should I power this with? 6V, 12V? I was thinking since I need so much weight in this ship for ballast I could use a nice large gel battery (I know it will prolly never get drained but I need weight, and there is alot of room inside this boat)

Thank you in advance

Massey

[keith S]

Massey, Follow the instructions for the bow thruster. If they do not give enough info, I would use a Speed 400 size motor for the thruster. On/Off works, but if you use a speed controller on it, you will be able to controll the amount of force you are trying to exert for the side wats motion. Works like the trottle on the main power. 12volt would be your best bet as it will give you the battery life and weight you are going to need for this prodject. FOLLOW the requirements for the Graupner Z-Drives. DO NOT OVER POWER them as they have a tendency to explode from the tourqe if rpms are too high.

[LtDoc]

Massey,
How to control a bowthruster sort of depends on how many different things you can do at one time. A couple of motor throttles, the rudder, and then a variable speed bowthruster are too many things for me but certainly may not be for you! A simple on/off type control is the simplest way of doing it. Couple of ways of doing even that, though. Putting a switch activated by max rudder throw instead of your finger is one of those ways. Using an ESC is certainly not that complicated or difficult either. The results of what you pick just pepends on how much you practice, really (and if you can walk and chew gum at the same time... my problem).
Powering a bowthruster (or any other 'thing') with a seperate battery is certainly one option. I tend toward using the same power source for all motors if possible. Not particularly 'better', just makes wiring simple and then I only have one battery to charge (lazy, impatient).
- 'Doc

(and if you haven't already thought of all that, it'll suprise me.)

[Ghost 2501]

i use 2 graupner bow thrusters in my Sydney Star, (Celestia), power for the two thrusters is from a single 6v 10ah lead gel, which also provides power to the radio and the motor. like the motor the bow thrusters are given 15a esc's.

To give equal power to left and right, that will take some fine tuning from the transmitter, though at 30% EPA F/R i have found that the thrust is pretty much the same in both directions.

LtDoc for me, one battery was the only practical way to go, as i needed the nicads for Gemini,

[Massey]

OK I found a suitable ESC for the bow thruster so I am going to go with proportional control. I am going to use a Mtriniks Viper Marine 15 for the bowthruster and I think I am going to go with the Mtroniks Viper Marine 40 for the speed 900s powering my Z drives. This should give me good control and they will also be waterproof :)

Massey

[Roger in France]

Hi Massey,

I am looking forward to following your progress in building "Tito Neri" as she is going to be my major build for winter 2007 (already overcommitted for winter 2006 !).

Have you given any thought to steering servos, as yet? Because of the power of the drives and, therefore,the effort required to turn them Graupner seem to recommend very expensive, high torque servos. My thoughts are:

1. Why two servos, one for each Schottel Drive? I cannot see why you would want to differentially move the two drives. I cannot imagine what manouvere is assisted by having the dives oriented differently. Surely this means the use of 2 channels? Two ESC's yes, I can see the need for differential speed.

2. What servos are best for this application?

3. If using one servo for both drives what torque is needed?

4. If running two high torque servos I have been advised that it is unwise to use a Y lead because of "...the current draw..." ?

Roger in France.

[steveciambrone]

Does the viper 15 have full forward and reverse capability?

Thanks
Steve

OK I found a suitable ESC for the bow thruster so I am going to go with proportional control. I am going to use a Mtriniks Viper Marine 15 for the bowthruster and I think I am going to go with the Mtroniks Viper Marine 40 for the speed 900s powering my Z drives. This should give me good control and they will also be waterproof :)

Massey

[harrin]

I use Robbe Rokraft 50 ESC and 6V SLA battery for Graupner bow thruster and they work very well together.

[Boatfox]

Hi Massey,
1. Why two servos, one for each Schottel Drive? I cannot see why you would want to differentially move the two drives. I cannot imagine what manouvere is assisted by having the dives oriented differently. Surely this means the use of 2 channels? Two ESC's yes, I can see the need for differential speed.
Roger in France.With all the effort going into building a tug...why not have the manuvering capabilities. The more control the more fun. The learning curve to master the "difficult" controls is very short....and the fun of moving sideways goes on a long time. :D

[Massey]

Hi Massey,

I am looking forward to following your progress in building "Tito Neri" as she is going to be my major build for winter 2007 (already overcommitted for winter 2006 !).

Have you given any thought to steering servos, as yet? Because of the power of the drives and, therefore,the effort required to turn them Graupner seem to recommend very expensive, high torque servos. My thoughts are:

1. Why two servos, one for each Schottel Drive? I cannot see why you would want to differentially move the two drives. I cannot imagine what manouvere is assisted by having the dives oriented differently. Surely this means the use of 2 channels? Two ESC's yes, I can see the need for differential speed.

2. What servos are best for this application?

3. If using one servo for both drives what torque is needed?

4. If running two high torque servos I have been advised that it is unwise to use a Y lead because of "...the current draw..." ?

Roger in France.


Far as I can tell a standard "race" type servo will have enough torque to turn the drives. You need 2 servos for the drives the as they are both independant. There is no common gear assembly for the 2 drives so you need to have each on with its own servo. Being that the drives will be stressful on the servos I would not want to try to turn them with only one. I agree with you on the no Y harness and not just for the current draw but for the trims. I want ot be able to trim each drive independantly. As for my ESCs If I cant equally mix 2 of the channels on my radio together for throttle then I am going to use a Y harness on the ESCs.


Does the viper 15 have full forward and reverse capability?


They have one that has reverse and one that does not. I am planning on getting the one that does of course.

Massey

[Massey]

Construction goes well but not alot of visual progress has been made. There are alot of parts that need to be laminated together and I am in the process of getting that done now. After this I will be putting the framework inside the hull. IF anyone that has build this tug before knows the answer to this question I would appreciate hearing from you.

How much of the inner framework can I assemble before I put it inside the hull? I am mainly worried about the aft section that holds the motors and the little corner pieces. These would be alot easier to assemble outside but that may make getting the frame into the hull alot harder and more dangerous.

Massey

[Roger in France]

Massey/Boatfox,

Thanks for the replies, all helpful.

However, can someone explain the manouvre which is effected by having the Schottel drives thrusting in different directions, please?

Roger in France.

[Massey]

Massey/Boatfox,

Thanks for the replies, all helpful.

However, can someone explain the manouvre which is effected by having the Schottel drives thrusting in different directions, please?

Roger in France.


It will have the same effect as reversing 2 fixed drives if they are both facing fore and aft, HAving one forward and one reverse will cause the boat to turn really sharp if not in place. In a real Schottel drive boat there is no reverse on the motors so in order to go in reverse they simply turn the drive 180 degrees and power it accordingly. In R/C applications this drive only turns 180 degrees so you get 90 to the left and 90 to the right. In order to go in reverse you reverse the motor and head backwards.

Massey

[keith S]

Rodger, The manuver advanage is the ability to "crab" sideways, close manuvering in tight spots ( same as full size ), and infinate control when running. If you have never run a z-drive boat, it is tough top imagine. Go down a line and do circles.

[Boatfox]

Dug out one of my books and scanned an image. This is the way they are supposed to work at least. The manuver farthest to the right is supposed to act like an anchor when doing ship assist work. Hard to pull 2 ten foot columns of water through the sea. :D

[Roger in France]

Thanks chaps, great help. Even a dunce like me can now follow your explanations. Great diagram, Boatfox, thanks.

OK, I am converted....a servo for each drive it is! But that leads to other questions.

I intend to set up my Robbe F14 Navy Radio with the two throttles (ESC's) on the twin lefthand sticks. Therefore, the steering (via the two servos) will be on the righ hand stick with up/down for one servo and across for the other. So, I assume (for example) taking "up" as "north", a movement of the stick to "north-west" gives me both drives fully turned right etc.? Or, it could be the other way around, depending how I wire up.

Needs a diagram I guess!

This control is going to take a bit of practise I think.

Roger in France.

[Massey]

This control is going to take a bit of practise I think.

Roger in France.

I think you are right... I cant wait to start practising!!!

Massey