Hi all
Interested to know how a bow thruster as shown in the photo below might effect sailing performance If at all
Any thoughts would be appreciated
Regards Don
They shouldn't be allowed in races, if the skipper under shot a mark a little nudge from one would solve the problem.
Hi Trek
That a thought 
I was actually thinking more about the drag of the thruster tunnel that runs through the hull might have in light conditions
Regards Don
I do not believe they make any noticeable effect to the boat. I had a through the bow, bow thruster on my Catalina 445. The only problem you have with this type of thruster is they will cavitate if they are installed too close to the surface or if there is chop on the water. My current boat has drop down thrusters on the bow and stern. These are far more effective, have no under water drag and as they are always in the dark, there is no growth which is also a problem on the through hull type. In my option I think bow thrusters are worth their weight in gold.
As for fudging round a mark, I can tel you that would not work for a couple of reasons. 1 They only push the bow round, no different the pushing the rudder over and 2 A bow thruster has no effect if the boat if doing much more than 1 knot.
As a long time racer many times I under shot the mark. Usually on light air days when the boats are drifting. At the mark if the bow is pointing under the mark and no breeze at all throwing the rudder over will have no use because the boat has no way. However if a bow thruster could be used to point the boat up so that when the next puff came it pushed the boat up over the mark, bingo. Many tines I used cigarette smoke to painfully like a snail preposition my boat using the extremely slight breeze that no one paid attention to in anticipation of the next puff while my competitors were whinging and doing nothing. And when the puff came was aiming the right way when they weren't. . Gold cups in the cupboard to prove it. I would imagine a boat with bow thruster running just right would help a boat point better too by being able to turn more upwind without sacrificing boat speed caused by rudder drag. Not sure though. But the whirring noise would alert your competition 
I think there would be a bit of a performance decrement, particularly if the hole was just straight through, that's why many have bumps on the leading edge or scallops on the trailing edge, to minimise profile drag as the hull tapers towards the bow.
I think the physics would get very complicated looking at the pressure differential effects and compressibility in the tunnel itself to get an exact figure.
overall I'd say there is an effect, and if you are that worried, then don't have one.
+1 FreeRadical.
If laminar flow along the hull is the desired effect for boat speed and pointing that hole on the boat in the pic would have to spoil it a bit. I guess it wouldnt matter unless you were match racing.
It needs covers like those that close over the Dunlops under an aircraft.
Select to expand quoteFreeRadical said..
I think there would be a bit of a performance decrement, particularly if the hole was just straight through, that's why many have bumps on the leading edge or scallops on the trailing edge, to minimise profile drag as the hull tapers towards the bow.
I think the physics would get very complicated looking at the pressure differential effects and compressibility in the tunnel itself to get an exact figure.
overall I'd say there is an effect, and if you are that worried, then don't have one.
Hi FreeRadical
From what i understand when the boat was ordered the thruster was a extra cost option and the box was not ticked but by the time the boat was manufactured the thruster was a standard fit and it is being supplied with one at no additional cost
Regards Don
a correct installation from drag perspective calls for a hollow at the trailing edge and a flair at the front the boffins say this gives a negligible drag profile but the straight through hole seen often on production installs is incorrect
