G'day Pete

Wow, some impressive calc's, i only ever went to school to "eat my lunch", not math !

Any way here is what Wolfston marine had to say on the Series II Swashdrive Jet.

We recently took delivery of two Swashdrive jets which have now been fitted into our free running model. I would like to take this opportunity to say how impressed we are with the jet construction and performance. The efficiency of your jets is almost twice that of the next best offering from Graupner.

I thought you might like some information on your jet performance in our model:

Propulsion system - Twin jet drives driven by twin Zenoah 260PUM engines

Model displacement = 28.9kg

Model Length = 2.185m

Deadrise angle at transom = 12 degrees

Model beam = 0.450m

Maximum speed (both engines fully open) = 23.6 knots = 12.13m/sec

Resistance of model @ 23.6 knots = 128N

Effective power = 128 x 12.13 = 1552W

Delivered power per jet = 776W

Delivered engine power = 2.32kW

Assume transmission losses of 5%, delivered engine power = 2.32 x 0.95 = 2.20kW

Jet Efficiency = 776 / 2200 = 36%

The best efficiency we have achieved to date with other jets (4 different designs to date) is 21%, so this represents a really significant improvement – well done!

I hope you find this interesting, Best Regards, Dickon Buckland.

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Wolfson Unit MTIA

University of Southampton

SO17 1BJ

Link to their website

http://www.wumtia.soton.ac.uk/