how to choos a jet pump

[Mikaelhsm]

hey guys.
Does anybody here have detail information about jetpumps? I want to choose an appropriate one for the boat i m designing, but none of the jetpump factories has offered its information.
can you help me plz?
thank you

[marshmat]

Hi Mikaelhsm,

Which companies have you tried? The last time I checked with the guys at Hamilton Jet, one of their engineers got back to me within a few days with their suggestions and recommended selection criteria. Ultra Dynamics seems to be similarly prompt, and I've heard (but can't confirm firsthand) that the guys who build Aggressor speedboat pumps are also pretty good about giving out the necessary data to prospective customers. If you're calling a shop that's selling off stockpiled Berkeley or Dominator parts, or used PWC pumps, a null response wouldn't be surprising.

Once you've made the decision to go with a jet, generic information isn't much help anymore. You need data specific to the particular model you're considering. It's worth noting that the manufacturers are much more likely to respond quickly and favourably if they can see you're serious about the project. Show them some of your drawings and ask "Given this list of key parameters and expected performance for the boat, which of your pumps would be a good match, and is the hull shape appropriate for your pumps?". This approach is likely to yield much more information than "Can I have some information about your products please?".

[baeckmo]

Fully concur with Matt here; present the main particulars; LOA, LWL, chine beam, LCG, total weight loaded, superstructure frontal area, required top and cruising speed to the manufacturers. Also state type of operation and eventual building rules. The serious suppliers will then tell you what power and which unit that will suit your demands.

One word of warning though; some manufacturers only show non-cavitating performance in their thrust/speed diagrams. At low speed and high load, the thrust may be restricted due to impeller cavitation if the rpm selection is not done correctly!

[Ad Hoc]

Originally Posted by Mikaelhsm

I want to choose an appropriate one for the boat i m designing, but none of the jetpump factories has offered its information.

In addition to that above,...it would be helpful if you could state 'kind of information' you are looking for. As noted, you'll need a fair amount of data to select your jet. You can't just say...i'll have XXX because i was told these are good!

In otherwords, you'll need to have some basic particulars of your design already done. The main one being, the weight estimate!

[Mikaelhsm]

Thanks for your replies buddies
I already tried Americanturbine, Solas and Berkeley, I also asked them to give me specific information, but no answere was reccieved. The companies you menstioned Matt, I suppose they do waterjet business rather than jetpump, while I need a jet-pump.  In fact, I ended-up with jet-pump because of its smaller size. However I checked them again, and I couldn t find any jetpump in Hamilton and Aggressor websites and one thing about Ultra Dynamic is that it seems its website is corrupted. I ‘ll appreciate your help if anyone can help me with a useful link. I realy get confused about why they are limitted in publiuishing their product ‘s information, In this case I agree with Matt. And finally, the exact spesifications which I need are something simslar to those which exists in waterjets data, I mean thrust curve, torque diagrams, … to help me to make my decision according to resistance curve.
Regarding this issue ,any suggestion would be welcomed warmly.
Thank you all

[baeckmo]

Mikael, I believe you make a linguistic saltomortale here. The general term used for the propulsion machinery is "waterjet", not "jet-pump"! You seem to make a distinction of some sort between various types. There is no such distinction, only a variation in design philosophy, resulting in a diversity in the physical configuration.

However, if you make a Google search on "waterjet", you will also get a number of hits related to texts on "waterjet cutting procedure". Since you are in Suomi, you have the Alamarin Jet in Härmä, who produce a range of jets locally. Just beware of their designation system; their size number refers to the impeller maximum diameter. This may lead to sizing mistakes, since the critical dimensioning factor is the impeller INLET diameter, which is what most of the suppliers use for reference. Apart from that, they should be a useful source of info for you, but remember, if you talk marine propulsion, you talk "waterjet", nothing else!

[Mikaelhsm]

Your information was very precious baeckmo, but one thing: what are those driver which are used in jet-skies and usually known as jet-pumps? don t they have any difference with water-jets?

[baeckmo]

To make it short: no!

[Ad Hoc]

Originally Posted by Mikaelhsm

And finally, the exact spesifications which I need are something simslar to those which exists in waterjets data, I mean thrust curve,....

Without this data, you are just guessing.

Guessing is ok if you have plenty of previous design data to support your guess, but it is still a guess. The jet suppiler can help you guess. But you still need to provide data in some form or other.

Perhaps if you provide us with the data of your boat, we can assist in your selection.

[marshmat]

Mikhaelsm,

Re. PWC pumps: These are usually compact axial-flow designs. They tend to be relatively inefficient compared to normal propellers. They are used mainly because of safety (no prop to cut your leg) and ease of manufacturing (a few simple castings and forgings, and a bit of lathe/mill work, much of which can be easily automated). There's another class of pumps that includes Aggressor, American Turbine, Dominator, Berkeley, etc. which are common in light speedboats, but don't fare so well at lower speeds. For more 'serious' applications requiring high speed, high efficiency and excellent low-speed control, commercial-grade pumps from suppliers like Hamilton, Ultradynamics, and (when the budget and the boat are both huge) Rolls-Royce and KaMeWa are more common.

For your reference, here's a minimum list of what you probably ought to have in hand when you call or email the manufacturers:
- Hull lines drawing with LOA, LWL, chine beam, deadrise at transom and at midships, and other key dimensions marked.
- Reasonably accurate weight estimates (total weight and CG) for light-ship, normal cruise and fully loaded conditions.
- Resistance curve if you have one (the jet suppliers can estimate the curve for common planing hull shapes if you don't).
- Desired cruise and top speeds in various load conditions.
- Powerplant intentions (high speed gas, high speed diesel, continuous-duty high torque diesel, etc.); if you have specific engines in mind, tell them which ones.

This is not quite enough data to actually specify and buy the pump, but it will (a) tell the supplier's engineer that you're serious and know what you're doing, and (b) give the supplier's engineer enough data that she can check your proposed design against her own calculations and database of successful vessels, thus ensuring that she can give you a realistic estimate and relevant data.

[Mikaelhsm]

Thanks a lot
Your information was pretty helpful guys. The point is that I have some limitation in giving all of these data you just enumerated. I m highly restricted by my superior to release body plan and hull lines drawing, but I m sure can give them the part that will be carry the engine near to aft. One thing else s that for your information I m currently not in way of building. Given the body lines I have to supply the boat with the target speed of 55 knots. It s just matter of satisfying but in a documentary basis. I also have resistance curve, an estimation of final displacement, dimensions and cruised and maximum speed. Maybe this much would be profitable at this level. yea?