Speed Forecast

I would appreciate our speed forecast for the following craft:

LWL > 13.7 m
Bmld > 4.0 m
Displ. Full load > 20.6 t
Deadrise > 18.5 deg.
LCG > 5.1 m from transom

Power > 2 x 700 Bkw
Propulsion > twin waterjets

Thanks,

RANCHI Otto

 

more info

Hi Ranchi,

I think we need some more info to make a good estimate... I've assumed a draft of 1m, but need sail area (superstructure and topsides areas) to estimate wind resistance... Information on wetted surface area would also be good... I used the empirical estimate built into NavCAD...

I've attached the NavCAD report and if you'd like to fill in the blanks (post values for what is left blank [zero]) I'd be happy to rerun the estimate... I think it would be best for us to give you resistance estimates and you can then use them to size waterjets and propellers...

Cheers,

Dave

 

Dear Dave, thank you very much for your kindness.

The additional informations are as follows:

Lcp > 14.2 m (projected chine length)
Aw > 12 m2 (frontal surface)
T > 0.85 m (static draft)
Ca > 0
Wind speed > 5 knots
Waves height > 0.250 m
Tother > + 5% (waterjet sog, waterducts inlets, etc.)
S > 52 m2 (static wetted surface)

What I'm looking for is to check with an existing craft if the speed of 40 knots for this boat is realistic or not.

RANCHI Otto

 

We manufacture fast Rigid Inflatable Boats, both outboards and jets( see www.explorermarine.co.uk) and we find that the best source for jet performance data is going straight to the experts - Hamilton Jet in New Zealand. Try their site www.hamjet.co.nz and submit a full data query. Their calculations are pretty accurate.

Regards
Hugh Mattos
Explorer Marine Devon UK