Waterjet for high speed craft.

[Vibtor]

I am working with projects for high speed commersial crafts with waterjet propulsion. The boats are typical V-hulls with deadrise of ca 23 degr. and lengths between 10 - 13 meters.
It seems to make problems getting speeds exceeding 45-48 knots.
Does any have experience about waterjets and 50+ knots for this boat sizes ?
Type of waterjets, hull design etc...

Vibtor

[cyclops]

Vague requirements. But look at the smaller high speed ferries in service from Australia. And USN assualt boats. Also 1 or 2 Florida off shore experimental boats. You have a lot of web searches to do.

[webcruiser8]

Waterjet is really the cool for custom cutting jobs.

It is easy to setup and quick to turn around. The cutting speed is fast and
cross section quality is very good. Most time no need to do post cut
heat treatment process because there is no heat affect zone (HAZ).

For more waterjet cutting machine information please go visit IWM's web site

[RANCHI OTTO]

I need more informations about the craft like:

/ lwl
/Bmld
/Power
/Weight at contractual speed
/ l.c.g.

[D'ARTOIS]

There is an end to the efficiency of a waterjet. On boats, that will cruise at high speeds faster than, say, 50 knots, you won't find them. Then the surface piercing propellor comes into the picture. Sofar I haven't seen any waterjet propulsion on high speed craft that goes over the 100 knots just as the off-shore racers and the like.

[RANCHI OTTO]

The Pershing boat reaches a speed of 61 knots with waterjets, many high speed craft are equipped with waterjets having speed around 50 knots.
The problem is perhaps the high deadrise angle of your design that doesn't correspond to the optimum for wj installation.

[D'ARTOIS]

I thought that Pershing uses Arneson Surface piercing props, secondly I am talking about high speed craft: 80 knots plus....

Webcruiser: we are talking about waterjets as a propulsion for boats, not for cutting materials.......

[RANCHI OTTO]

Pershing has a model equipped with waterjets too and having + 60 knots speed.
High speed craft for me are boats with speeds over 40/45 knots.
80 knots are far from commercial or private using.
They are very special boat and represent only a small part of market.
Anyway the question was around a craft having a speed of 50 knots with waterjet.......

You are a little be to polemical....

[D'ARTOIS]

OK Otto you 're right

[RANCHI OTTO]

The Pershing was built according to a private client's requirement and has the following main data:

L= 21 m Displ. = 27 t Power gas turb.= 4516 bhp Speed (trial) = 61 knots

We have 1 common love..... the horses.. (not horsepower)

[D'ARTOIS]

Hey Otto, how you come to know about my liking for horses?

I had a few racehorses in the past, used to race in France, Belgium and Holland.
My sister in France owns about 20 I believe. I have stopped racing but play polo from time to time. I had even a horse from Frederico Tesio.... long time ago....

[marshmat]

Azimut's got a few (take a look at the 86-S) that offer a direct comparison of waterjet vs. surface drive. Surface drives usually have a slight edge on top end and sometimes on fuel efficiency; waterjets tend to have better acceleration and handling. (My next boat will almost certainly be waterjet.)
As for high-speed applications: Take a look at The World is Not Enough, 139' LOA, 165 tonnes, 20,600hp and Lips waterjets. 70 knots top end. Ridiculous by any accounts, yes. But it shows jets can be practical for this kind of speed.

[tom kane]

Many water jet powered craft seem to go rather silly when trying to turn at high speed.Quite often a split asre turn happens,then out of control.It may look exciting but can be rather upsetting when you do not expect it.

[marshmat]

Ya... gotta get the right balance of keel fins and turning fins to keep the poor beasts tracking straight in a turn, with no leg sticking down there's not much to hold 'em to the surface.

[yipster]

same for a single surface drive as it need skeg / rudder or goes propwalking