sarabande
Well-Known Member
I used an electric launch last year on the Thames, with a 6hp motor. Silent. But use a bow thruster and everyone wakes up.
why are bow thrusters so noisy ?
- Thread starter sarabande
- Start date
Elessar
Well-Known Member
Appleyard
Well-Known Member
It's an audible warning. Like the bleepers on an HGV.
Poignard
Well-Known Member
sarabande
Well-Known Member
if it's cavitation then the blades are inefficient, so why aren't they designed properly ?
(Not stirring - sorry
- genuinely interested)
(Not stirring - sorry
- genuinely interested)
Fire99
Well-Known Member
Maybe they're designed with a 'look at me' factor into them.. Or maybe they're just not made very well. 
Appleyard
Well-Known Member
Whenever I hear one I always begin to worry if I have enough fenders out!
+1
Keen_Ed
Well-Known Member
Bow thrusters are small - to minimise the size of hole (the hole is draggy - smaller is better). So to get a useful effect you have to accelerate not very much water lots - means spinning the prop at high speeds. High speeds = lots of noise.
Electric motors (like steam engines) can provide lots of torque at low revs. More efficient (and quieter) to turn a big prop slowly.
Electric motors (like steam engines) can provide lots of torque at low revs. More efficient (and quieter) to turn a big prop slowly.
Elessar
Well-Known Member
Quite right. Factors when fitting a bow thruster.
further forward = more tuning moment = lower thrust to work.
further forward = narrow and shallow
shallow = cavitation, low water pressure
narrow = water pushed out can travel under the hull and back in = cavitation
small = noisy (concorde engines or old jets stand in evidence here)
big= quiet but increased drag when sailing
so live with the noise and get less drag and a smaller (cheaper) motor.
simples......
if it's cavitation then the blades are inefficient, so why aren't they designed properly ?
(Not stirring - sorry
hope the above answers your question!
trapezeartist
Well-Known Member
Or learn to enter and leave your berth without one. Please.
Jamesuk
Well-Known Member
Getting the bow thruster working is a pain. Generator on and when it is used there is a high pitch squeek off the generator crazy!
Sy-Revolution
Well-Known Member
Ours isn't noisy, it's quite smooth (Vetus 80kgf) but I know what you mean. Most I hear sound as though they're broken. Like an oversized coffee grinder. I've wondered that they might be hydraulic of something......
C.
C.
chriscoreline
Active Member
oars - your boat may be too small
no bow thruster - you have the correct sized boat
bow thruster - your boat may be too big
azimuth pods - your boat is awesome! Can i use your tennis court? I loved your last (album/hostile takeover/oilfield discovery/election campaign) - delete as appropriate.
Greenheart
Well-Known Member
When, some time in the next three decades, I finally finish my Frankenschooner, with its long keel and bowsprit, I'll have too much pride in its clean lines and my boat-handling, to cut a hole in the bow. Instead, I'm thinking I'll set up a grunty Minn Kota electric outboard on the bobstay, which can drop down and be steered remotely from the cockpit. Yes, I know it'll take some doing, but I like a challenge. I did say three decades, didn't I? Good.
No unnecessary holes in the hull, no unnecessary noise, no unnecessary £5,000 bill.
Considering how, for the most part, we used to cope without bow-thrusters, I can't see that it's possible to conclude how their application to relatively numerous, relatively small pleasure boats, has had anything but a derogatory effect on boat-handling generally. My girlfriend can't easily park her car; and she doesn't get any better if I offer to do it for her.
No unnecessary holes in the hull, no unnecessary noise, no unnecessary £5,000 bill.
Considering how, for the most part, we used to cope without bow-thrusters, I can't see that it's possible to conclude how their application to relatively numerous, relatively small pleasure boats, has had anything but a derogatory effect on boat-handling generally. My girlfriend can't easily park her car; and she doesn't get any better if I offer to do it for her.
pampas
Well-Known Member
IIf you think small thrusters are noisey then go into the thruster compartment of a deep sea vessel roar of the gears and the water flow is deafening so most of the noise will be the gears and the hull makes for a perfect sound box.
Fire99
Well-Known Member
To be fair, i'm certainly not going to complain about 'em. I'd rather someone have one and use it than not have one and bump into someone else's boat.
Poignard
Well-Known Member
At the last Beale Park boat show there were several boats powered by cordless electric drills. Some had a sort of homemade outboard motor powered by a cordless drill; very light and simple.
It wouldn't be difficult to make something like that could be temporarily clipped to the bow. It wouldn't need to run for very long and you could recharge it from the marina mains supply. But whether it would be powerful enough for your boat, I couldn't say
http://www.instructables.com/id/Super-Simple-outboard-motor-powered-by-a-cordless-/
Ripster
Well-Known Member
Good point, its when you can't hear them that you should have more fenders out.
Victoria Sponge
Well-Known Member
Ours isn't what I'd call noisy.
Stemar
Well-Known Member
In the past boat ownership wasn't something Joe Public could consider. Boat owners probably tended to be more skilled, but also there weren't the number of tight marinas; most boats lived on a swing where low-speed handlung was less of an issue.
[gross exaggeration/generalisation] Now everyone and his dog can afford a 35-footer and parks it squeezed into a tight marina, and expects driving a boat to be like driving a car, of course thay need bow thrusters. [/gross exaggeration/generalisation]
Mind you there've been a few times when I've only just got away with springing off in my 24 footer and a thruster would have been very useful!