Speed Boat on skis

[SeaSki designer]

Thanks, Intrepid71, for the very good suggestions relating to spray deflection. These will be worth trialling on the prototype. I would emphasise that the spray only becomes problematic in the sort of seas that would deter most small boats from venturing out. We have allowed windscreen wipers in the production model, but the more spray can be reduced, definitely the better.

Your figures for fuel consumption comparisons are quite correct, but I should state that the figures on our website are deliberately very conservative. We believe the reality will be better yet. For example, using boat test figures from Suzuki's website, a Key West 268 of about 2t with 18.5" pitch prop in moderate conditions @ 4000 rpm returned 40 km/h @ 30 l/h with the DF 300 hp motor (gear 2.08:1). We are expecting to get 70 km/h using a 28" pitch propeller based on our experiences with the prototype. Typically, we lose less than 10% of theoretical pitch speed, so that equates to 5.5 mpg or 3.8:1 against the Chevy.

Having noted the above, we have never realistically expected the boat to compete with flat bitumen and bearings. Our car racing exercise is purely for the publicity. To our knowledge no small recreational vessel has ever managed such a task.

[Mr Efficiency]

That 28" pitch prop is a bit of a worry, there is a reasonably narrow range of cruise speed that a boat can be realistically propped for, that extreme pitch means the thing will have to go like the clappers all the time or labour the engine when conditions necessitate a slower speed.

[hoytedow]

Originally Posted by Mr Efficiency

That 28" pitch prop is a bit of a worry, there is a reasonably narrow range of cruise speed that a boat can be realistically propped for, that extreme pitch means the thing will have to go like the clappers all the time or labour the engine when conditions necessitate a slower speed.

I suspect some of the young folks may not know what you mean by clappers, but I agree with your assessment.

http://www.youtube.com/watch?v=cVkZZsS-66c

[Mr Efficiency]

Originally Posted by hoytedow

I suspect some of the young folks may not know what you mean by clappers, but I agree with your assessment.

How about "going faster than last week's pay" ? Many more will understand that.

[hoytedow]

Originally Posted by Mr Efficiency

How about "going faster than last week's pay" ? Many more will understand that.

Especially around here

[SeaSki designer]

Originally Posted by intrepid71

Anything supported by water at high speed is going to have far greater drag than something supported by tires on pavement, no matter how clever the design.

As already acknowledged, a boat has probably no hope, at this point in time, of beating a car in a speed/economy equation, however they can beat cars in terms of journey time in a great many of our congested cities (for those lucky enough to live and work near to the water).

Where I lived in Brisbane, Australia, (on the Brisbane River) my car journey of about 10 km from St Lucia to Kangaroo Point (also on the river opposite the cbd) took an average 25 minutes in rush hour, so an average 24 km/h. The river journey of 8 km at 70 km/h (permissible on the river) would have taken 7 mins and, allowing for a 4 min. walk (we could park at our office premises), the total journey time would be about 11 minutes.

Certainly other issues come into play, such as moorings at home and destination, but the central issue is that even with living so close to my work, my travel time could have been halved each way and the quality of the journey unsurpassed!

Fuel expenditure would have gone up, admittedly, but weigh this against running your nerves ragged trying to avoid dingles with bloody minded drivers and the cost of high blood pressure tablets and temper control counselling, and I think expenditure becomes a lesser consideration?