Topic: I need a new bow thruster (Read 12233 times)

portside II · « **on:** August 30, 2009, 06:24:56 pm »

My tug Brakengarth is in need of some repairs to the bow thruster , at the moment is a Marx Luder 30mm type with a seperate motor running off 12v . But the pinion gears are slipping and after several attempts to repair i feel i will have to replace it .
The big question is how and iwith what ? ? .
The easiest way is just to buy another unit from Cornwall M B , which will set me back £41.95 + p+p .
The other way would be to rip out the tube and install a new unit all together , but which one ?
There are several ones on the market mostly with paddles which i find very noisy , or i could ask a member on here to make me one .
Any sugestions based on the idea that it has to push the bow of my tug around which is not the lightest and has a large wind area and will have to work off 12v as thats what i use .
daz

Robert Davies · « **Reply #1 on:** August 30, 2009, 06:44:23 pm »

In my experience I've found the Robbe and Graupner thrusters to be "Dear God!" noisy, I was pleasantly surprised when I heard a Raboesch thruster in operation - pretty quiet, and in it's specific case pretty powerful for it's size too.

May be worth a look?

-Rob

Brian Roberts · « **Reply #2 on:** August 30, 2009, 06:46:10 pm »

Hi Daz
I fitted a Raboesch bow thruster to my 1/16th Severn and I can thoroughly recommend it. It's quiet and powerful and cost about £27, but I don't remember the size.
Reades now sell Raboesch gear.
Hope this helps.
Brian

Brian Roberts · « **Reply #3 on:** August 30, 2009, 06:48:28 pm »

Great minds think alike!! I think Rob and I are talking about the same item!
Brian

Robert Davies · « **Reply #4 on:** August 30, 2009, 06:57:34 pm »

If it's fitted to a 1/16th scale Severn LifeBoat, I think we just may be!

Joking aside, it's pretty much Ronseal* as far as bow thrusters go....

-Rob

*To be 'Ronseal': To do exactly as it says on the tin... (/tub/box/packet....)

6705russell · « **Reply #5 on:** August 30, 2009, 07:03:22 pm »

I beleive all the big tug boys make there own with waste pipe, looking at some at the Birchwood show they are pretty good and more powerful than the ready available ones....

I priced a Raboesch today with Malcolm from Reade models for my Speedline Tamar, they are good bits of kit

Russ

ministeve · « **Reply #6 on:** August 30, 2009, 07:24:08 pm »

if you only have a narrow bow then the ones from reads are very good but if you have 6 to 10 inches you would be able to fit one like we fit for tug towing they are basic and reliable with bags of power they consist of a cut down prop shaft to 2.5"to 3" fitted on on the least angle your hull will allow with the coupling and motor in place the motor is normally a 12v 555 4000rpm to 6000rpm any more and you will just get cavitation and no thrust i will try and find some pics and post them

Steve

CGAux26 · « **Reply #7 on:** August 30, 2009, 09:23:13 pm »

I put a Raboesch Bow Thruster (BT) (size 108-03) in my Loyal Tender. This boat is 40" long, and displaces about 24 lbm. I first ran it on 12 volts, even though the motor is rated for only 7.2 V. After a total of about 5 minutes' operation, the red plastic paddle spun (slipped) on its shaft, and would not push water. I replaced the plastic paddle with a home made one of brass tubing and plate, soldered together. I made it a a push fit to the shaft, then poured a bit of 5 minute epoxy in the end of the tube.

I then turned the speed controller on my Spektrum DX6 down to 40% (150% is full speed). It ran fine, pushed the bow around satisfactorily, and has not slipped. But the boat was too fast on 12 V, so I changed to 6 V SLA's and now the BT is happier at 150% speed setting and the boat runs at scale speed. The BT seems fairly quiet even at full speed.

The Raboesch was purchased from Loyalhanna Dockyard in the US for $51.50. When the paddle failed I contacted Don at Loyalhanna, who arranged for a free replacement paddle and accessories kit to be mailed to me. So now I have a spare, should my home made paddle fail.

Malcolm Reade · « **Reply #8 on:** August 30, 2009, 10:53:07 pm »

That damage looks to have been caused by a VERY hot motor shaft? I guess that the !2v supply (against the rated 7.2v) would have caused the motor to over-speed causing excessive torque? I think the literature supplied recommends that the Bow Thruster shouldn't be run in bursts of longer than 30 seconds - running it for five minutes was always going to push it to the extreme? Once the motor shaft started slipping on the paddle, the heat would have got a lot worse.

It all suggests that this particular Bow Thruster was doomed to failure from the start?

Nice to hear that Loyalhanna Dockyard (great reputation) was able to source free replacement spares from Raboesch though...

Malc

ministeve · « **Reply #9 on:** August 30, 2009, 11:43:02 pm »

this is one i made it not pretty but it sure works

Welsh_Druid · « **Reply #10 on:** August 31, 2009, 09:11:39 am »

Quote from: CGAux26 on August 30, 2009, 09:23:13 pm

I put a Raboesch Bow Thruster (BT) (size 108-03) in my Loyal Tender. This boat is 40" long, and displaces about 24 lbm. I first ran it on 12 volts, even though the motor is rated for only 7.2 V. After a total of about 5 minutes' operation, the red plastic paddle spun (slipped) on its shaft, and would not push water. I replaced the plastic paddle with a home made one of brass tubing and plate, soldered together. I made it a a push fit to the shaft, then poured a bit of 5 minute epoxy in the end of the tube.

I had exactly the same problem with the Raboesch bow thruster fitted to my cruise ship "Arkona". I too made a brass paddle but soldered it to the shaft.

This was fine until the motor fell to pieces ! To be exact the brushes fell out.

I think Malcolm is right that the problems were caused by overheating as I too was running it on 12 volts , but the push fit method of fixing the plastic paddle onto the shaft seems to me to be a little weak.

When it was working it was a very effective unit but I have not bothered replacing the motor as I have found that I have all the manouverability that I require using the P94 mixer unit from FLJ on the twin motors.

Don B.

boatmadman · « **Reply #11 on:** August 31, 2009, 09:19:17 am »

Ministeve,

Could you let us know some details of that thruster, such as, what size hull, size and type of prop, what motor and dia of tube?

I ask because I may have to make one myself for my current project.

Thanks

Ian

ministeve · « **Reply #12 on:** August 31, 2009, 10:59:51 am »

ok the shaft is 2.5 to 3 inch long with an oil tube soldered just after the bush the prop is a 45mm x type speed boat prop. which i put on a bar and place in a drill then on the aproximate angle of what the shaft will be in the tube i then offer it up to a disc sander with the drill spinning untill it just spins in the 40mm waste pipe tube i then glue the prop onto the thread of the shaft push it through a hole drilled into the middle of a 12" peace of 40mm waste pipe slide the prop tube over shaft and make fast the coupling spline. after making sure the prop will spin with just a little contact to the inside of the tube i then glue with P40 chopstrand from halfords i use this because it is cheep sets fast is very strong and water proof you dont want to be standing there slowly spinning the shaft while waiting an hour for epoxy to set.
once set place a piece of medium sand paper in the inside of the tube to sand the prop to a close fit and to stop vibrations making the prop contact the inside of the tube once happy it is just a case of cutting 2 holes in your hull making sure you leave the prop at least an inch from the exit of the tube once fitted to the hull.
i hope this helps i am not good with a keyboard better to show what i on about

boatmadman · « **Reply #13 on:** August 31, 2009, 11:08:13 am »

Just the job Steve, thanks.

Ian

ministeve · « **Reply #14 on:** August 31, 2009, 11:28:33 am »

the hull in the pics are of the afon alaw which is 12" beam at max i have made smaller thrusters in a nangee and a dutch harbour tug. finding 30mm to 35mm tube is surprisingly hard

Malcolm Reade · « **Reply #15 on:** August 31, 2009, 11:38:20 am »

Going back to the issues with failures of Raboesch bow thrusters;

I think you have to treat them properly, like any other piece of machinery? As an analogy, if you bought a Bentley, and then tried to run it flat out on nitromethane in the Le Mans 24 hour race, it would likely be damaged too?

It would be wrong and very unfair to blame the product when the operator has misused it?

I believe that Raboesch bow thrusters are a good quality product (I wouldn't sell them otherwise), but abusing them by running them for long periods on excessive voltages WILL damage them.

Malc

Martin (Admin) · « **Reply #16 on:** August 31, 2009, 11:43:30 am »

I've seen many different bow thrusters and and as Roburto says below, some sound like outboard motors!!!
MiniSteve's type is not only the most effective but also can be made the most silent.
Just an observation, is space is really tight, you could consider using a flexy shaft arrangement.

Also, don't go overboard on size and power, there's rarely need to rip out the the mooring bollards out of the harbour wall...

I must try and get comparative video clips of the various types of model bow thrusters.......

ministeve · « **Reply #17 on:** August 31, 2009, 12:55:35 pm »

will have a look and see if i have any footage of one of ours going flat out

portside II · « **Reply #18 on:** August 31, 2009, 02:40:14 pm »

Thanks guys , loads of info there .I have been thinking about a home made one like yours Steve , but i dont think the hull would allow me to fit one . As for the raboesch Malc , yes they look ok and are probably quieter than the other paddle type but unless i can change the motor easly to a 12v one then i may be overloading a 7.2v unit .
Like i say my tug has a high wind profile , and as the goole pond is open to the prevailing wind then the thruster would be used a lot for extended period's .
I have seen Steves thruster in opperation (on his tug

) and it is a powerfull piece of kit , i did make one once and it managed to push a 2" stream of water about 16" vertical so the idea does work extremly well .
daz

Brian Roberts · « **Reply #19 on:** August 31, 2009, 03:42:10 pm »

Hi Daz
The Raboesch BT on my 1/16th Severn has its own dedicated 7.2 battery and as well as a bit of extra ballast, it works very well.
Brian

poll · « **Reply #20 on:** August 31, 2009, 05:21:36 pm »

Quote from: Martin - Admin on August 31, 2009, 11:43:30 am

I've seen many different bow thrusters and and as Roburto says below, some sound like outboard motors!!!
MiniSteve's type is not only the most effective but also can be made the most silent.
Just an observation, is space is really tight, you could consider using a flexy shaft arrangement.

Also, don't go overboard on size and power, there's rarely need to rip out the the mooring bollards out of the harbour wall...

I must try and get comparative video clips of the various types of model bow thrusters.......

Good chance there Martin, Balne Moor m.b.c. tug towing 13th September. bring the camcorder.

John.

CGAux26 · « **Reply #21 on:** August 31, 2009, 07:51:45 pm »

To clarify my earlier post, I DID initially "abuse" the BT by running it on 12V. I know that RPM is proportional to voltage at the motor in DC motors. I DID NOT run it continuously for 5 minutes. I know better, and the boat would still be dizzy if I had. I meant I ran it a CUMULATIVE 5 minutes before the paddle failed. And the new brass paddle is made of brass sheet and brass tubing.

My last real boat (32 ft. sport fisherman) had a Vetus BT, which could only be run maybe 30-45 seconds before the humongus fuse would blow. And always at just the wrong time. Murphy's Law applies to BT's, too.

ianb · « **Reply #22 on:** September 01, 2009, 09:42:07 am »

I put a Graupner B/T in my Aziz but..... very noisy, not a great thrust and I couldn't stop it from leaking a little when running.

Bit the bullet, ripped it out and put in a Raboesch.

No leaks and much quieter together with plenty thrust.

But the thrust dropped off after a couple of months, and I like others discovered that the impeller was slipping on the motor shaft. It wasn't damaged so I glued it back onto the shaft and put everything back together. Haven't tried it out yet under real life conditions but it may be all right. Incidentally, it runs on about 6 Volts max through a speed controller. Slam bam control seems a little hard on it in my opinion. 12V, no way.

Ian

FullLeatherJacket · « **Reply #23 on:** September 01, 2009, 11:13:32 am »

Quote from: ianb on September 01, 2009, 09:42:07 am

I like others discovered that the impeller was slipping on the motor shaft.

I gather that this is a weakness which Raboesch are sorting with a re-design of the unit. Ian is right when he says that a speed controller is kinder on bow thrusters than a bang-bang switch.

FLJ

ministeve · « **Reply #24 on:** September 01, 2009, 06:12:38 pm »

from what i hear Raboesch are already redesigning a few of there bow thrusters and once they are done they will be very competent aids to steerage i don't know if they will be up for tug towing in a bit of a breeze though

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Author Topic: I need a new bow thruster (Read 12233 times)

Robert Davies

Brian Roberts

Brian Roberts

Robert Davies

Malcolm Reade

Malcolm Reade

Brian Roberts

FullLeatherJacket