fitting bowthruster

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rlw

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Hi

I have just purchased a sunseeker Martinique 38 and am considering installing a bow thruster as our marine has only a boatlenth between moorings.

Id be interested to hear any pro / cons. I am considering a 50 kg thrust unit (4 hp)
Will a truster tunnel impact my top speed. How far below the waterline does it have to be to function and still be above when planing to reduce drag.

Any feedback welcome

Rob

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There are no cons to installing a bow thruster other than the cost. You need to make sure its powerful enough (and 4hp sounds about right) otherwise its not worth having and that its installed correctly. It needs to be as far below the waterline as possible but also as far forward as possible which are 2 contradictory requirements. The other consideration is, in order to minimize installation costs, to site the tunnel in such a position so as not to require modifications to bulkheads or furniture in the forward cabin
No, it wont significantly affect your speed providing the tunnel is faired into the hull properly although sometimes you may get a bit more spray thrown up
Worth speaking to Osmotech at Hamble Point marina who are distributors for Sleipner and have done a couple of successful installations for me over the years

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I had a 4hp bowthruster on my Sealine S37, and it was just about OK. I'd personally recommend the next size up (6/7hp), it will only cost another £300/400 or so. Take a look at the new(ish) Lewmar range, which have 5 bladed props instead of 3, which means quieter operation, less cavitation, and full thrust in both directions (some give 100% one way and 75% in the other). They are about the same cost as a Vetus unit. I'm having a 7hp fitted to my boat in march, so I hope it lives up to it's claims!! They are really worth having by the way.

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Wont effect boat much except I did here of one badly fitted one that tried to sink. Have you thought of getting a boat that does not need bow thrusters, or even driving leasons??? .../forums/images/icons/smile.gif

<hr width=100% size=1> <font color=blue>Specializing in marine sanitation since 1997.<font color=red> I'm a volunteer!!.<font color=blue>

Haydn
 
Have managed without one one my previous boat. However once or twice each season you get into a situation were they can make the difference between a scractch or not. The background is that I am considering having the colored section of the hul painted in a different color (seen the result of a local painter on another boat and it looks fresh out of the mould) and if would want to keep it scratch free.

That said moving up from a 31 ft Portofino to a 38 footer could prove interesting the first few hours.

Rob

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From what you have said a bow thruster on it's own might not help alot. There only usefull if you can use them in conjunction with all the other controls. I presume you have two engines. Sounds like, on outdrives. Shafts are much better. But even with outdrives, controling the boat is not imposible. Folk try to use bow thrusters, just to do the things they were already doing wrong, easier. For a start get two big round fenders and put them on yer bows. Mine go about where my second porthole is I think. Find the right place for yours. Now always go out of a mooring backwards. But first using the engines. Push your arse end out, by pushing against the fender. OUter engine forwards, iner back. You keep the boat still of course till yer arse is in the position you want. You can get to nearly 90deg if you have some one holding the fender. Using a bow thruster would just stuff yer arse end into pontoon. Yes a bow thruster can be usefull. Cant think when I'd want one though. But then I have shafts!! /forums/images/icons/smile.gif

<hr width=100% size=1> <font color=blue>Specializing in marine sanitation since 1997.<font color=red> I'm a volunteer!!.<font color=blue>

Haydn
 
I need to moor stern to between two poles (Holland)
I can use the poles as leverage to spin the boat but find the rubber in the rubbing strake does not like this. Might give it a try this season and see how it goes.
Considering the upholstery needs redoing in and out the thruster migt need to wait anyway.



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Ah well might need a sausage shaped fender, or I sometimes make a string of sausages in that position. Dont get poles much here. But harbour walls with big heavy timbers down the side. Used to use fenders and a plank for that. But little used these days so sent plank home. I'ts now for decorating!!..../forums/images/icons/laugh.gif

<hr width=100% size=1> <font color=blue>Specializing in marine sanitation since 1997.<font color=red> I'm a volunteer!!.<font color=blue>

Haydn
 
Ive just done this very thing on my Birchwood 35.
Went back in the water yesterday after being out since November and it's absolutely brilliant.
Certainly the best mod you can do on a motor vessel and one you wont lose any money on.
Used the Vetus 55kg/f unit. Cost with all the bits and pieces ie twin joysticks, control cables, fuses, battery cable, isolator etc £1275. Installation, £560...to have the tube laminated in and unit fixed. I did the electrics myself being that way inclined.
So for less than 2 grand I have an excellent tool.
From my experience I would definitely go for it.
The 55Kg unit is about the right one for your boat with, (Ithink), a tube dia of 150mm.
A special cutter and jig is needed to cut the holes in the hull and this is hired from Vetus or one of their main dealers I believe.
It needs to be fixed as far forward as possible to maximise the turning moment.
On my semi displacement boat the actual position is fairly unimportant as its never gonna get out of the water, but on a planing vessel fit it so that hopefully it is clear of the water when fully planing to avoid the cavitation effect of the tube and therefore drag and noise.
Installation on our boat was made a lot easier as we decided to strip out the forward cabin completely and rebuild it after the bowthruster was fitted, as we were two thirds through a refurb, it fitted in with our plans quite nicely. The easy interior access was obviously reflected in the labour charge for the laminator and mechanical installation.
If you want more info PM me and I'll send you photo's of the installation process.


Hope it helps

Steve.






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I took your advice and tried to leave my mooring backwards.
After I mounted the pontoon behind me and landed on a Squadron 64, I rolled over and sunk. What did I do wrong.
PhilF

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Excelent I think you got it just right.../forums/images/icons/laugh.gif

<hr width=100% size=1> <font color=blue>Specializing in marine sanitation since 1997.<font color=red> I'm a volunteer!!.<font color=blue>

Haydn
 
Now had a complete about turn, well i would if I had a thruster. Have instructed the boatyard to fit one immediately!

I have seen the light at last! /forums/images/icons/wink.gif

<hr width=100% size=1> <font color=blue>Specializing in marine sanitation since 1997.<font color=red> I'm a volunteer!!.<font color=blue>

Haydn
 
Please do try to find the noisiest thrusters you can in order to wake up the whole anchorage, these do seem to be the most popular.

<hr width=100% size=1>Julian

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It works both ways. Doesn't take a bowthruster to wake an entire anchorage. Was in the Bag at Salcombe last year when a raggie boat came in about 1 in morning. Skipper was shining 3million candle light at everything in sight, and bellowing (largely useless) instructions at crew.

Luckily I was still up with friends having drinks and chat (quietly). Several raggie boats had peoples heads pop up, while he tried and failed to get onto several pontoons and moorings.

Finally one lady got so fed up she stuck her head out , and bellowed rude words we can no longer post here, to effect that there were people trying to sleep, and could the skipper please try to find a mooring without use of megaphone. Worked too! He gave quiet commands as he should have done in first place, and funnily enough crew got the yacht onto next mooring.

Wouldn't have minded, but how they managed to screw up so many times when he was bellowing when no wind nor tide was amusing, when they got on first time when he quietened down!!

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Wow Bendan are you following me around the forum /forums/images/icons/smile.gif

The bowthruster thing is not aimed at MOBO's in particular, although more commonly fitted to them, many yachts over 40ft also seem to fit them as standard now too.

Haydn is right about using them to cover up the skippers mistakes. I used to skipper a 45 ft MFV for diving parties, after some practice I could move her sideways onto the wall and she had a single slow rpm 4ft screw. I am not saying I could step onto a fairline and get her onto a pontoon in one shot, but give me half a day and I reckon I could become quite proficient at it. Practice makes perfect as they say.

I saw a similar thing with a bav trying to get onto the pontoon at Aberystwith last year, strangely I knew they would have problems as soon as I saw them coming up the harbour, somehow you can can't you? The SWMBO really did take her title to heart as she screamed at her poor husband on the helm, the two friends on board and me who had walked along the pontoon to collect her lines.

After two aborted attempts she finally managed to throw the line to me, all 8 ft of it, I had managed to get a turn around the cleat when the helm put her in reverse, so I am now left either hang onto rope against boat or let go and watch him yet again fly out of berth. Well this loud mouthed woman on the bow decides to take out frustration on me now, "c'mon, throw back the end of the line (about 2ft), c'mon, throw it back, THROW IT BACK WILL YOU", so I took the turn out and threw it back, turned around and walked off.

<hr width=100% size=1>Julian

<A target="_blank" HREF=http://www.topcatsail.co.uk>Top Cat Homepage</A>
 
Not following you around, just that it's only us posting at this time of night, and you post stuff I want to respond to! <g>

I dislike loud skippers, there is no reason for it.


There are good reasons for bow thrusters,though Haydn is right in his pointed comments about learning to drive first.

Bow thrusters are useful on occassions on bigger boats, but often good skills would negate their use in 90% of occassions? Don't know to be honest, I've rarely had the opportunity to use them, and have learnt other skills

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