Suitable Jet Drive

[donaldknyu]

Hi Guys,

I am looking for Pump Jets for shallow water cruise.
LOA: 40m
B: 10m
D: 3.3m
Draft: 0.6m
Hull: barge like hull
Speed: 7knot in still water

I need your pro advices. Which products are good for shallow water river.
Thanks in advance

[Marco1]

You have basically 4 pump manufacturers, Hamilton, Scott, Berkley and American turbine. Pick the one that has a rep in your area and ask them wich one would suit your application. You did not mention what engine do you intend to use and if your river is fresh or salt water if you want one or two jet, if your barge is monohull or twin pontoon etc.
The Hamilton HJ213 would probably suit and if fresh water, HJ212 yet depending on the engine you intend to use you may need a bigger pump.
Scott has the 852 that is probably the best pump around but they also make smaller ones. Berkley still makes pumps despite rumors to the contrary and they are perhaps the best priced even when not the most modern desing. As for American turbine I don' know much about them so can not comment.
Look for a local dealer and take it from there.

[anthony goodson]

Jet may not be your best solution.There is a lot of information on here about props in tunnels ,Hopefully CDK Baeckmo etc will chime in and help here.

[anthony goodson]

Well I appear to be alone here at the moment, so I will elaborate on my remarks of this morning. You do not state the displacement of your vessel but judging by the dimensions it is considerable. To move this bulk efficiently you need a large slow moving propellor or two. A jet unit is designed to move a comparatively light load quickly and despite what the manufacturers tell you,this is the only mode where it really works efficiently I have stressed the efficiency because you have said that you intend to use this for cruising which implies long distances .fuel consumption will therefore be important. If for example you intended to use the barge for short journeys ,work with people in the water,need 360 degree manouverability or the ability to dry out without damage then a jet may be for you ,but it will have to be a very big one. You should also bear in mind that a jet at low speed in shallow water can be very vulnerable to a sandy or stony bottom ,particularly in high thrust conditions. here again the jet excels only at speed. Weed can be a major problem in shallow rivers .I know nothing worth mentioning about propellers in tunnels but others on here do ,perhaps if you search the archives it might help.

[baeckmo]

Ok Anthony, can't resist the bait...... Anyway, I think you have pointed to the problematic issues already. For this application there is just one answer: NO WATERJET HERE!

Let's check dimensions; with Donalds round figures, we talk about a displacement of 130 - 160 tons, with no info on shape other than "barge", my guess on power from similar project boils down to something like 2 x 200 hp, minimum.

Reasonably sized jets would simply not provide thrust enough to have authority over external forces on the hull! Manoeuvering with high power in shallow water means that the inlet velocities are high, often more than 10-15 m/s. Anything loose within a meter or two from the inlet will be ingested. With full power at the low speed of advance, serious cavitation problems will cause rapid damage in addition to the erosive damage caused by debris.

You should go for twin or triple propellers in full tunnels; or better a swept-up bottom aft. It will be possible to use prop dias of ~0.6 m which still is on the low side for max efficiency, but they would work reasonably ok. With a correct design of tunnel entrance, the inlet velocities are far lower than for a corresponding jet.

[rasorinc]

Good answer. Baeckmo.

[anthony goodson]

Thankyou I feel a lot less lonely now.

[donaldknyu]

Thank a lot guys. I agreed with you and will have to decide to use inboard z-drives or fixed propulsion system with tunnel.
I feel that fixed pro system should be preferable because of efficiency.
But I feel that it will be difficult to install to meet the angle of main engine alignment.

Can you kindly share your experiences ?