Stern Thruster Suggestions?

[coyote454]

I'd like to add a stern thruster to my 34' CHB.* I've read that the electric models would be adequate, but can only run for a few seconds at a time.* Hydraulic units can run non-stop, but are costly.* This isn't a large vessel, and I believe an electric model would work well, but I'd like a few opinions from those of you who have experience, good or bad, with specific models.

Mike Wiley/1982 34' CHB/ChristyLee/Brookings, Oregon*

 

[RT Firefly]

I could be WAY out in left field but have you considered an electric tolling motor? I think thay have some pretty big units now and they can be run for periods of time.

 

[coyote454]

RTF,

Being WAY out in left field is another way of saying you're thinking 'outside the box', and that's never a bad thing. Got me thinking, so I checked out BassPro to see what the specs were for their large trolling motors. I think that those motors would not have sufficient thrust to move even a 17K pound boat sideways against a current, although the theory is sound. The other obsticle would be in the installation, where it could be operated by one person from the helm. But I like your thinking!

Mike

 

[North Pacific Guy]

Mike,

My North Pacific 42 has an electric stern thruster by Vetus, not sure of horsepower. It will not overheat until it has run for about three minutes, nonstop. Even though I have a single engine, with the bow and stern thruster combination, I can turn the boat on it's axis. Despite what some may say about how "real men" do it, I am all about keeping the Admiral happy. She loves the thrusters.

Donnie Young
Cloud IX
NP42

 

[Marin]

A bolt-on stern thruster made specifically for trawlers with their transoms that don't go very deep into the water is the Cap Sante, made by that company in Anacortes, Washington. You might check with them to see how long their thruster can be run continuously.

-- Edited by Marin at 16:57, 2007-12-18

 

[coyote454]

Donnie and C. Marin,

Thanks for your input. It sounds like you both are satisfied with your respective units, and I've put inquiries out for both. And Donnie, as far as "keeping the Admiral happy"....I know what THAT'S about!

As somebody once said, "If Momma's not happy......NOBODY'S happy"! And as I know my Admiral would like me to have as much control over the little Chubbie as possible, buying a stern thruster is really for HER! (think she'll buy this?)

(Little Chubbie===did I really say that?)

Thanks,

Mike/CHB/ChristyLee/Brookings, OR

 

[Marin]

Mike--- Just to clarify, we do not have a thruster, bow or stern, on our boat. We have a twin and so far have not found ourselves strongly wishing we had a thruster. A bow thruster would come in handy on occasion but I don't think a stern thruster would give us much capability that we don't already have with the two props and the rudders.

I have seen a lot of ads for the Cap Sante stern thruster and have read some comments on various forums from people who have them and said they are very happy with them.

 

[Keith]

You already have a stern thruster.... your prop! It's just a matter of technique and practice. Check out the Krogen FAQ page at: http://www.his.com/~vann/KrgStuff/Krognidx.htm
Scroll down about 2/3 of the way and there are several articles in section 9 about handling single screw vessels. Once you get the concept of "goosing" the throttles and using the rudder, you won't need an additional stern thruster.

A bow thruster though... that's a very nice thing to have!

 

[RT Firefly]

Mike,
From your bio, you say you have recently pruchsed your boat. The boss and I (well really the boss) have made it a rule to NOT make any major changes for at least a year (or season) until we get to know the boat. Keith makes a very good point about learning how to drive and manouver. I know of a guy who bought a 42' Marine trader with a single engine and spent $7K installing a bow thruster-this was a while back. He used it quite a bit the first year, less the second and almost never the third and folowing years. He told me one time it was handy once or twice a season if he got bent out of shape docking but he admitted he really didn't have much use for it.
I agree, you have to keep the boss happy but maybe you could steer her into maybe a make over of the head or some new deck furniture and hold off on the thruster until you both are more comfortable with the boat.

 

[coyote454]

Keith and RTF,

I checked out the Krogen site suggested and thought it was a fascinating read. Holding back on major purchases until one knows the boat well is also a good idea.

Having come from blow boats, I had just resigned myself to having very little control while backing a single screw boat. But the procedure given was very interesting, to say the least. Seems like that might work well with practice.

When the weather calms down, I think I'll start practicing the 'goose' method of turning in reverse and see how it goes. If I can pull that off where the Admiral's more confident without a thruster, that just means more money for other toys! There's always something!

Thanks all!

Mike/CHB/ChrityLee/Brookings, OR

 

[Marin]

Mike---

If you want to see how controllable a single engine boat can be in reverse, check this out

.* Single engine boat, using its inertia, rudder, and thrust to do this. As I understand it, this is an annual contest among the commercial fishermen and the object is to see who can back into the slot the fastest without touching the piles or the shore. The boat is being driven from the aft deck control station.* Threre are a few more clips showing other boats in the same contest once you open this one.

While we have a twin GB, I've learned the single-engine backing technique on 60' steel canal boats in the UK. These boats are shallow draft and totally flat-bottomed. so prop walk yaws the boat a lot and very fast. In fact, these boats pivot more or less in the middle, so not only does the stern swing to one side, but the bow swings the same amount to the other side and you end up diagonally across the canal. Coordinating the boat's inertia, the rudder, and alternating forward and aft thust, it's possible to move these boats backwards hundreds of yards down a canal if necessary between moored boats with only a few feet of clearance on either side.

A bow thruster makes things easier, but single engine boats can be maneuvered very well without them (I am not advising against bow thrusters here, just saying that a single engine boat is not the unwieldy lump some people believe them to be).


-- Edited by Marin at 13:32, 2007-12-19

 

[coyote454]

C. Marin,

Hey, that clip was downright cool. Those skippers weren't using the 'goose it back and forth' method, but had enough control that they knew how much prop walk to allow for. Talk about coming into a dock a little hot! Those guys were good!

I guess I'd better resign myself to doing a lot of practicing before deciding on more gear.

Thanks,

Mike/CHB/ChristyLee/Brookings, OR

 

[Marin]

Mike---

If you listen to the audio you will hear at least one quick shift and slight power shot to correct the stern as the boat is approaching the pilings, and you can see the stern shift over a bit at the same time. I suspect the boat has a single lever control so shifting and power application can be done pretty fast.

I first saw this clip on another forum some time ago, and a fellow who has been to this contest was in that forum and explained that they do "back and fill" at least once as they come in but they are moving so fast and the correction is done so quickly that the only way you can really tell is to either see the skipper manipulate the controls or hear it.

-- Edited by Marin at 17:49, 2007-12-19

 

[FF]

"Seems like that might work well with practice."

Works very well with a minimal amount of practice.

The bigger the wheel the better it works (why your blow boat sucked) .

Once was aboard a small (45ft) tug with 6-1 and BIG prop,

a BLAST in reverse brought the stern to a 45deg angle with the dock , in one shot!

FF

 

[Marin]

Mike---

If you ever get a chance to watch a truly professional skipper maneuver a single-engine boat in close quarters, it is well worth hanging around to watch.

Several years ago Carey of this forum and I (and our wives) had our boats in a marina on Saltspring Island in the Canadian Gulf Islands. We happened to be there the night the marina installed its new floating breakwater. It was towed over from Vancouver by a relatively small Fraser River tug (60 feet maybe) and arrived about ten pm. The tug then proceeded to push and prod the breakwater, which I'm guessing was perhaps 200 feet long, made up of multiple sections bolted together, into positon so the marina people could install the big pins to hold it in place.

It was really something to watch the skipper maneuver that tug in very tight quarters, in the dark, moving quickly from place to place to push on one side or the other, first at one end of the breakwater, then at the other. Sometimes he pushed hard, other times just a tiny nudge, sometimes he just held enough pressure to counter the current so the marina guys could install a pin.

Before heading back to Vancouver he went to the fuel dock to take on some diesel, and Carey and I talked to him for a few minutes about his boat. It was an older tug, powered by a 12V-71, and had a conventional prop and rudder arrangement (as opposed to a Cort Nozzle, etc.). IIRC, it had a two-man crew. When we complimented him on his boat handling he said that when you run these things day in and day out you get a real good feel for how they handle in every situation and you can anticipate exactly what the boat's going to do.

An important element of being able to put a single engine boat right where you want it is power. I learned this with the canal boats in the UK. To do what this tug skipper did, you have to be willing to give the boat a healthy shot of power at the right moment, even if it's only for a second or two. A lot of boaters tend to be very timid of putting in power when they're maneuvering in close quarters, with the result that they sometimes get blown or moved by the current into the very things they''re trying to avoid.

It's a skill you want to learn carefully--- putting in a healthy shot of power at the wrong time can be pretty damaging. And you don't want to end up yanking the shifter back and forth frantically in an attempt to undo something you didn't realize would happen--- it's REAL hard on most transmissions for one thing.

I don't pretend to have a good handle on this skill other than with the canal boats (which are almost impossible to damage), but watching the pros at work if you have a chance is a great education in my opinion.

-- Edited by Marin at 21:11, 2007-12-20

 

[coyote454]

C. Marin,

Thanks for the input and sound advice. Until this post asking for advice on thrusters, I'd really never considered the capability of the CHB to be manuverable enough to be docked without some kind of help from a thruster. Especially when we're talking about tight quarters, tide, and so forth. But after hearing from you and the others, I'm getting jazzed on trying to learn the skills of manuvering the little CHB with just the single wheel. I mean, after all, if Fast Fred can do it......

Seriously though, this is really a skill that I should have anyway, even if I do add a thruster down the road. Having the capability to handle the boat in the method described previously would be invaluable, especially when you consider there could always be a thruster failure.

As FF noted, the small wheel was the problem with the blow boats I was used to, as they intentionally have small props for reduced drag. I could never get any consistent reverse direction, but as this Chubbie has a 24" wheel, giving it a little power shot should make quite a difference.

To avoid meeting other boaters and their insurance agents, I think I'll practice outside the breakwater first. I probably should have practiced this up in Tacoma before having the boat trucked down last summer. 20/20 hindsight!

Thanks again for your help.

Mike/34' CHB/ChristyLee/Brookings, OR

 

[Marin]

Couple of thing you can do regarding practicing (this is good for twin drivers, too,) is go to an area where you have plenty of room and toss a long, floating cushion on the water. Then use the cushion as your "dock".

Another handy practice device if you have them in your area is a so-called "linear mooring." The Washington Parks Dept. has fallen in love with these things despite the fact that boaters seem to hate them and refuse to use them. It consists of two tall, anchored buoys about 100 feet apart. A pair of heavy lines with composite mooring rings woven into them is strung between the buoys. The idea is you treat the rope on each side like a dock and tie up to the rings. Boaters won't use them, at least not up here, so there are rarely any boats moored to them. They make great practice "docks" since they are anchored in place at each end so will not shift with cross-currents or winds. So you can practice docking in a variety of conditions. And since they're basically just ropes, you can't damage your boat if you come alongside a bit too hard.

-- Edited by Marin at 01:23, 2007-12-21

 

[FF]

I mean, after all, if Fast Fred can do it......

Yes but FF has a boat with the old mechanical shifted Twin Disc .

The ones as used in WWII landing craft where the US Navy book sez


DO not shift from forward to reverse at full throttle," UNLESS its needed."

Big difference in what is severe abuse in a hyd shifted yachty tranny* and what is normal operation with military grade equippment.

With her 32x32 wheel and 3-1 box a quick nudge is easy to locate the stern.

Additionally she has a "Backing Rudder" which is a megaphone like device in front of the prop geared with the rudder.

This helps accent the prop wash in reverse.

AS a launch it was needed so the boats could come along side , either side, or simply stop in a slip with out the stern slewing sideways.

Thanks , taxpayers!

FF



-- Edited by FF at 05:41, 2007-12-22

 

[Baker]

My Perkins M20 in one of my sailboats and it's tranny(don't remember the make) allowed for shifts forward to reverse at ANY RPM!!!...right in the book in black and white.

 

[trawlerguy]

I've thought one of these units mounted on a swivel under a swim platform or such would do a good job. 200Lbs of thrust... I.e. about 5hp


-- Edited by trawlerguy at 10:39, 2007-12-23

 

[FF]

Would you be swiveling them down into the water?

DC motors are reversable so there would not be a need to swivel , unless you are into vectored thrust.

MY usual rule of thumb is 20lbs of thrust per hp , 25 from the best prop in existiance,

200lbs from 5hp seems high , and 5hp figures to big amps at 80A - 12V per hp.

FF

 

[trawlerguy]

FF wrote:
Snip>>Would you be swiveling them down into the water?<<

My thought was to swivel out of water/dismount when not in use.

Snip>>MY usual rule of thumb is 20lbs of thrust per hp , 25 from the best prop in existiance, 200lbs from 5hp seems high <<

Just numbers and ideas... you can do more research. I've no interest in quibbling about specs. The concept seem viable to me. If it leads you to more possible ideas I'm glad.

 

[FF]

Most boats already carry an outboard or two for a dink.

Seems that if someone built an outboard bracket that could be used secondarily as a thruster it would only require some cables, for throttle and shift.

A 20 hp OB could make 200lbs of thrust (with the right prop) and still be aviliable for dink work.

FF

 

[Marin]

I dunno..... Sounds like a real pain the butt to me. To use an outboard motor as a thruster means you have to go aft, lower the motor into the water, start the motor, shut it off when you're done maneuvering, raise the motor out of the water and if you're conscientious about outboard maintenance, flush it out with fresh water. To say nothing of having to snake incredibly long throttle and shift cables through the boat's interior to the helm station.

If a boater feels the need for a stern thruster, it would seem that the hassle of trying to use the dinghy's outboard would soon outweigh the expense of installing a purpose-built stern thruster like the Cap Sante where if you need it you just push a button at the helm station.

The outboard motor idea would work but it seems to be a real Rube Goldberg method of solving a problem that's already been solved in a much more simple and hassle-free manner.

 

[FF]

"The outboard motor idea would work but it seems to be a real Rube Goldberg method of solving a problem that's already been solved in a much more simple and hassle-free manner."

Perhaps , but as I see the advantages , the OB could easily have remote start , an electric throttle and electric reversing.And is onboard and maintained any way.

A hand full of slim wires and 20-to 50? hp is on tap,

POWER+ THRUST as good as a big buck Hydraulic setup at 1/100 the cost,and complexity.

In electric each HP in 12V is about 80A so a 20hp thruster would need huge electric cables , to power the unit , for the minor time limits of most electric units.

Then the smoke comes out .

Caviat Emptor,

FF

 

[norseman]

Has anyone looked at or installed the thrusters made by sideshift?* The stern thruster application appears to be interesting.

http://www.sideshift.com/

Tom Jones

 

[Marin]

Their stern thruster idea is similar in basic concept to what Cap Sante has done. However, one difference is that the Cap Sante's propeller is enclosed in a tunnel and the unit can be mounted partially above the waterline and still develop maximum thrust due to the tunnel design. So it's ideal for boats with very shallow-draft transoms like GBs, CHBs, Nordic Tugs, etc.

We don't have any sort of thruster on our boat nor do we intend to get one, so I'm not saying the Cap Sante is better than any other stern thruster on the market. But from the couple I've seen on boats, it's a very clean installation.