Pneumatic bow thruster

[jfm]

air inction into water jets is not new !

When you come to think of the part the forum has played in the introduction and development of

underwater LEDs
stabilisers

Can Air Augmentation be far behind ?

Tee hee! Thanks for the link Sarabande

Problem with normal bowthrusters is that by the time you have craned the boat out, cut and glassed the tunnel etc, you have a £3000 bill to install what started out as a £700 bit of kit, kinda thing. I wonder whether something like this http://www.ebay.co.uk/itm/NEW-Yamah...-Fishing-/170797552623?_trksid=p2054897.l4276 can be quickly lashed on and off, and operated by a remote switch? MUCH cheaper. Of course the thrust may not be high, but if the name of the game is to get a bit of help in a tricky mooring spot rather than fight a F7 sideways, then maybe it would be ok. Or if you have a 4hp petrol o/board already, perhaps use that and just design a clever fold away bracket? Dunno really, just chucking the idea out.

As for whether to have a b/thruster at all, I'm with OP on this. Boating is a hobby and you should feel free to fit any accessories or toys you wish. It has nothing to do with need and everything to do with "Do you fancy one of those gizmos?". I've got loads of useless "You don't need that you wus!" gear on my boat; it's a central part of my boating policy

EDIT - oops, apols, I didn't read page 2 before posting and didn't realise others had suggested electric o/boards. Ah well, consider my post another vote in favour of the electric o/board idea

 

[Coaster]

I have not looked at this thread before.

...He should be able to tie-up a 27', single-handed, undrer sail and would do well to ponder how to set about the task.

The OP may be pondering for some time. I see he has a 27' semi-displacement motorboat (post #23).

I wonder how Mr Reed would set about the task in such a vessel?


PS I compliment the OP on excellent taste in his choice of boat.

 

[ianj99]

FFS!

That's got to win the 'over reaction of the week' award.

A new subscriber to the forum, having problems with a new boat he isn't used to, and he gets treated like that.

PC may not be your strong point Cliff, (something you're obviously proud of), but what about good manners?

+1

There are too many on this forum who's ego's probably far exceed their skill level when faced with an unfamiliar boat. I see no reason why technology cannot be used to make life easier.

 

[Barleycorn]

PS I compliment the OP on excellent taste in his choice of boat.

I thank you! Yes I am rather pleased with her!

 

[cowpat]

If he wants to make and fit a B/T on a 27ft then why not? Too meany negative people on here.
Its all about horse power delivered.
It would be difficult to store AIR in enough capacity of to make a powerfull enough sudden and large jet.(Air is 800 times less dense than water)
I experimented with a water jet and was supprised at how big a bore and flow required to get the power I needed.
I have made and fitted a impellor type in a tube on my boat.
Keep the ideas comming and life's always interesting. Chris.

 

[Modulation]

Harsh, but true!

I wondered how far in this would go before someone blew his top about bow thrusters in small boats.
I think this one's the fastest yet!!

 

[RAI]

I suppose, as a first order calculation, the force you would achieve would be the pressure at the nozzle times the area of the nozzle. So how much pressure and how big a nozzle are you thinking of?

 

[Daydream believer]

I suppose, as a first order calculation, the force you would achieve would be the pressure at the nozzle times the area of the nozzle. So how much pressure and how big a nozzle are you thinking of?

Air bow thrusters do not necessarily work in the way you may be thinking
An experiment with large ships involved pumping air all along the side. The air bubbles escaping up the side of the ship formed an area of low pressure ( as in -lower than the pressure of water). The ship, therefore, moved sideways TOWARDS the air bubbles. The energy required to pump out the air bubbles was less than that used for standard impeller thrusters.
So the idea of air is not to provide a massive blast but a "screen" of bubbles

 

[cowpat]

Air bow thrusters do not necessarily work in the way you may be thinking
An experiment with large ships involved pumping air all along the side. The air bubbles escaping up the side of the ship formed an area of low pressure ( as in -lower than the pressure of water). The ship, therefore, moved sideways TOWARDS the air bubbles. The energy required to pump out the air bubbles was less than that used for standard impeller thrusters.
So the idea of air is not to provide a massive blast but a "screen" of bubbles

Very interesting!. Thanks for posting that. Can you tell us a bit more? How successful was the experiment? Chris

 

[RAI]

So the idea of air is not to provide a massive blast but a "screen" of bubbles

OK, so lots of small holes. How much thrust can your system generate? Are any ships actually using this system?

 

[Mistroma]

Air bow thrusters do not necessarily work in the way you may be thinking
An experiment with large ships involved pumping air all along the side. The air bubbles escaping up the side of the ship formed an area of low pressure ( as in -lower than the pressure of water). The ship, therefore, moved sideways TOWARDS the air bubbles. The energy required to pump out the air bubbles was less than that used for standard impeller thrusters.
So the idea of air is not to provide a massive blast but a "screen" of bubbles

Interesting, I hadn't heard of that getting used commercially. I said in post #3 that air would generate suction when injected at bottom of an open tube. i.e. Hole on side of hull with tube leading to surface (opp. side of hull).

Still not as effective as the usual design as the amount of suction is limited. i.e. You can't turn up the prop. speed with this idea, only make the tube deeper or wider.

I guess that a commercial version could make it work by having a lot of outlets low down along the hull and could be energy efficient. I still think the normal design will turn out to be more easily installed, more flexible and more powerful at reasonable size.

 

[Daydream believer]

As far as i know it worked ok as i seem to recall a film of a ship moving sideways as a complete unit rather than swivelling one end
Might be worth googling for info
Are there any forumites from the shipping industry who can comment?