Autopilot to bow thruster interface needed?

Does anyone have any experience with an autopilot being interfaced to the bow thruster on a recreational boat? I understand the benefit of having the application on a larger vessel with a slow ROT but I'm wondering if it's practical or even needed on a smaller. more maneuverable boat.
While I've never owned a boat with a thruster, I've operated many that were equipped with them but never tested the ability to alter a heading while underway. On a smaller & faster boat, I would imagine that a bow thruster has a reduced effect, if any effect at all, while the boat is underway due to the lack of water in the tunnel.
I have a pretty long history regarding autopilots but I can honestly say I have never had the request (or need) to interface a pilot to a bow thruster since most of my work has been in the recreational sector 65' and under.
I'm posting the question because the owner of a Fleming 55 inquired about the feasibility of an interface and while my first response would be to say it wouldn't be necessary, I do want to try to make sure that I'm advising him correctly.

I'd suggest to the owner to try activating the bow thruster manually in the situations where he thinks it would be beneficial to the autopilot. Then determine if it has enough effect to be worth the cost / effort of integrating it.

I'd also be curious what the owner expects to gain from the integration.

rslifkin said:

I'd suggest to the owner to try activating the bow thruster manually in the situations where he thinks it would be beneficial to the autopilot. Then determine if it has enough effect to be worth the cost / effort of integrating it.

I'd also be curious what the owner expects to gain from the integration.

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I could see where an interface might enhance the steering response at a very slow speed but personally, I wouldn't want my thruster grinding left and right all day long.
I feel it's something the owner is just curious about because it's advertised in the pilot literature but I don't see a huge advantage to it in his case.

The suggestion seems to be using the AP in close quarters maneuvering, or using the thruster while cruising a waypoint.

Which neither is designed to do.

The higher the boat speed the less efficient the thruster becomes. Sorry absolutely no use to interface the two.

When I was figuring out how I wanted my boat equipped, I considered AP thruster control, but only in order to allow the AP to keep the bow pointed into the seas while stopped fishing offshore. Ultimately, I decided against it because it would have necessitated a hydraulic thruster and a more advanced (expensive) AP. I still regret that decision.

MYTraveler said:

When I was figuring out how I wanted my boat equipped, I considered AP thruster control, but only in order to allow the AP to keep the bow pointed into the seas while stopped fishing offshore. Ultimately, I decided against it because it would have necessitated a hydraulic thruster and a more advanced (expensive) AP. I still regret that decision.

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Agreed, a sophisticated thruster/propulsion system would be a definite asset to someone like yourself who needs it to maintain a static position while fishing but I'm pretty confident with the boat I'm referring to here, the owner only uses the pilot to travel between points A & B. I will make sure he isn't interested in that type of a "skyhook" system but that would be an expensive upgrade, no doubt!
I do appreciate your experienced input.

Well, maybe your customer also would like a fully automated cruising system: Plug in your destination and engage, then sit back an enjoy your cocktail while the radar looks out for traffic, the electronic charts gives the system information to avoid rocks and when you get to your destination it communicates with the marina, finds its assigned slip automatically, backs in and contacts the marina guys to tie you up and hook up power and water.

You just sit back with your drink in hand and watch the world go by.

The automated system will also contact the Coast Guard to come rescue you when it goes sour.

David

DavidM said:

Well, maybe your customer also would like a fully automated cruising system: Plug in your destination and engage, then sit back an enjoy your cocktail while the radar looks out for traffic, the electronic charts gives the system information to avoid rocks and when you get to your destination it communicates with the marina, finds its assigned slip automatically, backs in and contacts the marina guys to tie you up and hook up power and water.

You just sit back with your drink in hand and watch the world go by.

The automated system will also contact the Coast Guard to come rescue you when it goes sour.

David

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It’s already out there in widespread use. It’s called hiring a captain lol!!!

I had a 34-ft marine trader. And the ow thruster had virtually no effects at anything over idle speed. Not the conditions where you would engage on autopilot. I cannot speak for larger boats

I wonder what your contact sees as the "use case" for using a thruster while under way, regardless of whether it's interfaced with the auto pilot or not.



Personally, I can't imagine any benefit from this. I only see it as added complexity and cost...and another interface to fail when some device manufacturer decides to upgrade its software without testing all possible -- and unlikely -- scenarios.


To be of any benefit, he would have to be going dead slow, as already stated above and it would have to be very calm, otherwise the bow thruster risks sucking air between the wavelets. It also seems to me that this would be an unkind system design for the battery having to supply the power to the thruster. I think a premature death of this battery would likely be in the cards.

Most electric thrusters have a very limited operating time.

Even if it worked to steer the total on time might be far above what the unit is built for.

A hyd thruster might survive better.

Underway is one thing, at idle or rest is similar to dynamic positioning...

....but my guess is if that's the goal, design parameters have to be met for that purpose....modifying may be impractical.

Bow thruster is absolutely worthless at anything above slow marina speeds. Imagine standing next to a parked car and pushing yourself away. Now imagine the car is moving at 20 mph and you try to push-off. Energy goes all over, very little (if any) in the direction you want.

Peter

I think this member is confusing the integration of AP and Thrusters to Engines and Thrusters used for docking a boat ( like idock system or Easy Docking system)

Certain Simrad autopilots (AP25 and AP50 families and later I presume) have offered a Thruster Interface. It provides a control signal to a thruster by either on/off solenoid, continuous control (voltage or current), proportional directional control or Sauer Danfoss PVEM valve. The thruster output signal is calculated in the TI (Thruster Interface) based on mode and heading information received from the Control Unit and other system units on the network.

Its function is to supplement the rudder(s) in maintaining the vessel's AP selected heading at any speed below 6 kts. As speed falls off and rudder authority is lost, the thruster proportionally provides additional correction. The FU or NFU steering levers if present, can also be used to control the thruster directly with a button push.

It can be useful in when anchoring, station-keeping, docking or during low speed vessel operation, particularly when shorthanded.

I've used one in the past and found it was a 'nice to have' optional feature, but certainly not a necessity.

LarryM said:

It can be useful in when anchoring, station-keeping, docking...

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The last think I’d want is having the autopilot engaged whilst docking...especially with the AP having control of the thruster...

Jim

JDCAVE said:

The last think I’d want is having the autopilot engaged whilst docking...especially with the AP having control of the thruster...

Jim

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That's what I was thinking as well

JDCAVE said:

The last think I’d want is having the autopilot engaged whilst docking...especially with the AP having control of the thruster...

Jim

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Jim, agreed, the use when docking is probably very limited. I saw it used to hold a workboat parallel to finger pier in a crosswind while docking. The solo captain secured the stern line and the TI kept the high bow from being blown away from the pier while he secured a mid-ship brest and so on. The boat was otherwise stopped. He used it more like you might use a remote thruster control. The corrections from the thruster seemed measured and proportional.

MYTraveler said:

When I was figuring out how I wanted my boat equipped, I considered AP thruster control, but only in order to allow the AP to keep the bow pointed into the seas while stopped fishing offshore. Ultimately, I decided against it because it would have necessitated a hydraulic thruster and a more advanced (expensive) AP. I still regret that decision.

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This is the one scenario I wouldn't have considered. I certainly wouldn't want it with an electric thruster, but a hydraulic one driven off the engine(s).. for your fishing scenario it'd certainly be interesting. Couple it with a satellite compass and you'd kinda of have a poor man's version of the drift heading feature in modern pod setups. (as in, keep me pointed toward X degrees while drifting).

IF all that is desired is emergency steering at speed many boats can be steered by the use of one trim tab at a time.

You wont get into your slip, but if you are 100 miles out you should make it to anchor in front of a repair yard.

I wouldn't want my thrusters hooked to the AP for ANY reason... makes no sense.


Underway, the AP on most boats does a respectible job. If you get really slow it can be problematic. However, I've used the AP at very low speeds when changing helms or just minor station keeping, preparing lines for docking, etc. and works good enough.



I rarely use thruster unless docking. Might use them rafting up with another boat, but never with an AP engaged.

I don't know about current models, but earlier Simrad-Robertson had a BT interface option.

Thrusters above a couple of knots will have little to no effect on your heading. Even when when down to a knot or two a thruster has a delayed effect, the thruster does not instantly move the bow.

Think of a thruster and a rudder as two separate situation controls, a rudder turns the stern when the vessel is moving, a thruster moves the bow when the vessel is not moving. As the vessel starts to move thru the water the rudder becomes more effective and the thruster becomes less effective.

M

steering a boat with a bow thruster is ineffective, steering from the wrong end of the boat.
You might consider a Jog stick steering.
https://www.sbmar.com/articles/marine-jog-lever-steering/
Properly set up, it is possible to eliminate the helm wheel. The problem jog steering might be, too many of us learned to steer with a wheel. Historically and within the last 40-50 years one or two major car manufacturers tried using steering stick ..... didn't work out.... again, we are used to a wheel to steer the car and boat. I guess the learning curve will just have to wait for future generations.