Bow Thrusters - general question

[wizard]

Does having the two holes in the bow of a yacht (with or without eyebrows) make any significant difference to the actual performance of said yacht in terms of boat speed?

Would be very grateful for comments from those who have the before and after results on the same boat.

 

[Fendant]

People who have done it say that there was no noticeable difference.
Experts claim that it will cost .1 - .3 kts.
Bow thruster builders sell retractable thrusters at a steep price and people go for it.
Main question is how exactly can you measure before/after ????

 

[TonyBuckley]

Does having the two holes in the bow of a yacht (with or without eyebrows) make any significant difference to the actual performance of said yacht in terms of boat speed?

Would be very grateful for comments from those who have the before and after results on the same boat.

Even an external bow thruster such as the exturn is reported to offer bugger all sailing degradation - they have published extensive figures and charts which are complex enough to put me off looking any deeper but that's what they say.

 

[homer]

I have not noticed any difference although I did fair in the holes to a reasonable degree, as suggested in the installation instructions.

 

[Danny]

Even an external bow thruster such as the exturn is reported to offer bugger all sailing degradation - they have published extensive figures and charts which are complex enough to put me off looking any deeper but that's what they say.

Fitted an Exturn this season. No noticeable difference in performance that I've noticed.

 

[djc]

Had my bow thruster fitted about 15 years ago , at the time I did wonder if I would lose some hull speed or notice any difference but I haven't , not that I ve noticed any way .
I can still achieve my max hull speed with ease and have HP / speed to spare.

 

[Rivers & creeks]

Eyebrows reportedly reduce additional drag to as good as zero. Without them there is supposed to be a significant impact.

 

[djc]

Forgot to mention in earlier post mine has eye brows , ie slight flare outs on the leading edges BT of tunnel .

 

[wizard]

Thanks all for the info. My mind is at rest will go ahead and have it done.

Could not believe the Exturn it looks like a pilot fish under a big predator. Surely that makes it vunerable to any junk that you might run into?

 

[Danny]

Thanks all for the info. My mind is at rest will go ahead and have it done.

Could not believe the Exturn it looks like a pilot fish under a big predator. Surely that makes it vunerable to any junk that you might run into?

Guess on a mobo it could be damaged by a hard grounding but on a raggy that's unlikely. In the event you did hit a semi submerged object hard enough to damage the Exturn then it would probably have severely damaged the hull if the thruster hadn't been there!

 

[Fendant]

Danny, you are spot on with your comment. The advantage of the Exturn is, that it is well below the water line.
Any floating hostile objects will scratch the hull but not rip off the "pilot fish".
Ok, if you hit with 10kts a floating container, you will have a hole in the hull bigger than the Exturn shaft

 

[garvellachs]

Had my bow thruster fitted about 15 years ago , at the time I did wonder if I would lose some hull speed or notice any difference but I haven't , not that I ve noticed any way .
I can still achieve my max hull speed with ease and have HP / speed to spare.

I suppose you're saying the extra drag can be overcome by extra power - available from an adequate engine or a strong breeze. But I find it hard to believe that the extra drag would not be noticeable when trying to race in light airs? Or when sailing in gentle winds generally?

 

[Tranona]

I suppose you're saying the extra drag can be overcome by extra power - available from an adequate engine or a strong breeze. But I find it hard to believe that the extra drag would not be noticeable when trying to race in light airs? Or when sailing in gentle winds generally?

May well be the case. However the effect is likely to be small - and offset by having a folding propeller, for example. Guess light airs "racing" performance is not higher on the list of priorities of the owner than the benefits available if a bow thruster is fitted.

 

[djc]

I suppose you're saying the extra drag can be overcome by extra power - available from an adequate engine or a strong breeze. But I find it hard to believe that the extra drag would not be noticeable when trying to race in light airs? Or when sailing in gentle winds generally?

I see what you are saying , but I haven't notice any difference in light airs under sail either , May be on a racing yacht thoughts may be different but as a cruising yacht I have found the drag / turbulence factor no problem at all . And the extra manoeuvrability it gives in port when short handed brilliant.