Use pressurized water as manuevering thruster?

[ldrumond]

Searching draws a blank.
Seem to remember that a number of years ago, Vetus listed in their catalogue, a thruster system for manuevering small pleasure craft that was based on a stream of pressurized water optained from a high capacity water pump. Water stream plumbed to thru hulls at "4 corners" somehow controlled by valves?
Probably a simple reason why I can't find any info on it.
Memory fails me, didn't / doesn't work -- right?

[SeaSpark]

Remember the system and a test report i once read.

It had one big disadvantage, efficiency was around 60% compared to a normal bow thruster. Advantages were, less drag from water in/outlets and more freedom in choosing a place for the pump. I wonder why Vetus does not sell the system anymore.

[FAST FRED]

www.omnithruster.com

These are for commercial work boats , not cheap, for 75 to 2200hp.

Better efficency , although a std prop is usually figured at 50% , in comparison these may be better.

FAST FRED

[SeaSpark]

http://www.ybw.com/forums/showflat.p...iew/collapsed/

Contacted a friend of mine with experience in this field, he remembered the Vetus sytem and knew it was discontinued becouse the pump had to be exactly matched with the hoses and nozzle. Changing lenght of hose or adding a bent in it affected the (poor from start) efficiency dramaticly. In practical applications this lead to systems with very poor performance.

[SeaJay]

These look pretty interesting to me...wondering if you couldn't modify a small jetski pump???

http://www.willdo.nl/

[kach22i]

Originally Posted by SeaJay

These look pretty interesting to me...wondering if you couldn't modify a small jetski pump???

http://www.willdo.nl/

Great link, I've bookmarked it. I have a (air) bow thruster for a "on-paper" hovercraft design. The same problem of the bow thruster having to be almost as powerful as the main stern thruster/prop exist for hovercraft as well. Mass and momentum are a pain to shove around with effect.

[Frosty]

When I had a steel yacht I was toying with making a bow thruster from a small outboard motor gearbox. An appropriately sized tube with a flat on the top section to bolt the gearbox up to . It would then be a simple matter to attach a reversable electric motor to the shaft on the inside.

[rwatson]

This is an idea I have been interested in for a long time.
I remember seeing a film about a 30ft catamaran that used what looked like a garden hose outlet in the bow, to push the bow around, as it was very long and thin, and had a big turning circle.
My ideal would be a control stick like the ones on the new Volvos, that simply opened up the appropriate nozzle(s), and you went in that direction.
Might only need small nozzels for directional control, and one big propulsion one for the stern.
I thought if using the foot off a yamaha ject drive outboard motor for the pump. Very compact.
More ideas very welcome

[Sternwheel Rat]

I too am interested in this type of bow thruster. I am designing a sternwheel riverboat that will need bow and stern thrusters for close quarter manuvering. I thought about the waterjet because of the reasons stated above,{lack of drag, ease of placement, availability of water pumps, etc..} But a little research concluded this is not a viable choice, except on fairly small craft. I've decided to go with the standard thruster,{prop in tunnel, electric motor on top, mounted thru hull fore and aft}. I do plan to build my own, with an old foot off small outboard. Glad I'm not the only one who dreams up this kind of stuff.

[rwatson]

S Rat - did you look at the http://www.willdo.nl/ site ?
They have this sort of system up to 80 ft ?

[Sternwheel Rat]

rwatson, thanks for the link. First off, the largest they offer is up to 20m, {66ft.} and my plans are for 120ft. by 30ft. Then, it's powered by hydraulics, not the way to go, as far as I'm concerned. I've studied the options and decided on diesel over electric, so electric thrusters is what I'm looking at. I will need very powerful thrusters to overcome the wind effect on my "sailboat without a keel". The other problem I see is the pickup, straight down. This is a brown water boat, not a blue water boat, and I spend a lot of time in very shallow water. Picking up rocks and mud off the bottom sounds like a lot of costly repairs in the very near future. The through-side tunnel set up looks better, because not only do you get thrust on one side, but suction on the other!

[FAST FRED]

An electric start outboard that could be lifted clear of the water , between the hulls, would be the cheapest and simplest to install

.Push right is FWD , push left REV? (Reverse for the PC crowd.)

In some sizes the OB can be had with a deeper reduction gear case , and spin a larger propeller.

Hardly elegant but the thrust is substantial , and 20 to 100 hp system or larger would surely be less expensive than an in hull version.

FF

[Sternwheel Rat]

I have a home made bow thruster on my boat now. A Minn-Kota, 101 ft. lbs. of thrust at 36v. It works very good on 43 tons of sternwheeler. The problem is, I have to pull it out of the water manually, not very convienient from the pilothouse. And it takes up deck space. That's why I was thinking water jet, remote location, permanant placement, etc...
I'm leaning toward conventional now, prop inside tunnel driven electrically, mounted below water level, permanant.
If you've got the room, and don't mind dropping it in when you need it, an electric trolling motor makes a fine bow thruster, multi-directional as well!

[SeaJay]

Getting back to the idea of water jet nozzles...The WillDo Jet Thruster ( http://www.willdo.nl/ ) sure seems like slick solution but I can't help but think that this could be expanded upon and built using off-the-shelf components. Why not one honkin' central pump for multiple uses...bow thrusters, wash down, damage control etc? What sort of pump would be best? How do you calculate thrust generated by a water pump? Clearly there are losses in piping, fittings, etc...and what to use for nozzles? control valves? Any ideas?

[Sternwheel Rat]

I hadn't thought of using the Fire/Washdown pump for the thruster! That's a great idea SeaJay!
Now, I'm with you, how to valve it out?