DIY bow thrusters design ...

[ianabc]

Many boats have scuba gear, some even an onboard compressor.

A small tube in the bow with controls, basically a stainless steel pipe with standard ss. shut of valves that from a pressure tested accumulator would perhaps provide controllable bow movement.


Anyone tried this?

 

[VicS]

would perhaps provide controllable bow movement.

not much I'd think. There is not enough mass in the air. You'll get lots of bubbles though!

 

[sarabande]

you might be able to entrain water using a form of venturi, but the total energy input from compressed air might be better employed driving an air motor attached to a propellor in a tunnel.

Hmm, the more I think about that, the more attractive a high-pressure airline round the boat is. Particularly for short term power uses. Loads of powerful motors available, so anchor and sheet winches, furling gear, water pumps, and none of this nasty business of depleting and charging batteries to worry about.

Just a great big air tank. And think what sort of foghorn you could play with !

 

[BGW]

Many boats have scuba gear, some even an onboard compressor.

A small tube in the bow with controls, basically a stainless steel pipe with standard ss. shut of valves that from a pressure tested accumulator would perhaps provide controllable bow movement.


Anyone tried this?

Mythbusters did (sort of).
They converted a speedboat to take two huge air cylinders and the performance was slow and very short lived.
They thought they may get better performance by dropping the outlets into the water to get a better push, but it was slower and travelled half the distance.

 

[pampas]

Deep sea. The most exspensive motive power is compressed air. just a thought!

 

[DannyB]

If you used two tanks with water in one and compressed air in the other, you could push out the water with the compressed air, greater mass gives greater reaction force. I used to have a model airplane that used jet propulsion, basically you half filled a plastic bottle with water then pumped air into it to pressurise it, the water was discharged through a jet and away it went. Using compressed air on it's own didn't work. A water air system would have a limited capacity but if all you used it for was getting into a tight berth then it could well work.

 

[cowpat]

air bow thruster

To ianabec. No.not air as explained above. I have experemented with water jet from a 1.1/2" pipe outlet from a 40' head centrifugal 8" impeller pump 60gls/min 1700rpm. The thrust was very disapointing. Although if it was in a light displacement boat with stern outlets as well would possibly be acceptable. I used,and fitted, a Marine Hardware belt drive unit and 2 Lucas LM1 24v starter moters of 9bhp each. One for each direction linked direct to the same shaft. Excellent thrust but need the generator on while in use. Any help? Chris.

 

[saltwater_gypsy]

There was an earlier thread on this
:http://www.ybw.com/forums/showthread.php?t=151095
Has most of the answers.

 

[Ubergeekian]

Mythbusters did (sort of).
They converted a speedboat to take two huge air cylinders and the performance was slow and very short lived.
They thought they may get better performance by dropping the outlets into the water to get a better push, but it was slower and travelled half the distance.

Have a look at the "Bang Versus Top Gear" video at http://www.bbc.co.uk/bang/