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?

[whitepointer23]

hello trevor. can we have an update on your project.

[SeaSki designer]

Everything is very slow, Whitepointer! We have been trying to find $120,000 for 10% equity to build the first production 7 metre model (plans are ready) which would put us on a proper commercial footing, but everything promising turns to jelly. Our local "angels" are anything but when it comes to being a little adventurous with their funds. Not to mention all the other venture capitalists and would-be investors. I guess they like banks, shares, and consumables more than boats? I have made an application to an Australian Defence capability program which is highly competitive, but unlikely to hear anything until August and then the second round commences which knocks out a whole lot more before the remnants are known in about May. I also suspect they like missiles, ships & subs more than little boats! Sorry I have nothing positive to report!

[tunnels]

Its just a tunnel boat !!!
All things work exactly the same cushion of air !!!
In surface effect and
It goes like stink !!.
Tunnels work better the faster they go BUT the faster they go the more fuel they use the more fuel the higher the cost
Ooops now we are into snow balls
Square and boxy looking is cool !!!
Matchs all the other terrible looking plumb and rackbacks bows that are springing up these days .
As for transporting people ,how about shipping containers on skis with a huge merc outboard or two strapped to an end ?? could gas axe a hole at the front for air conditioning and the steerer to see where hes going !!
Lazy boy chairs and a plasma tv on the wall for the long trips !!
Would be a way of recycling some of those old containers you see laying around . $275,000 how many old containers could you buy with that much money ????

Ok whats next on the list !!!!

[SeaSki designer]

Sorry, Tunnel, but you are on the wrong tack entirely! Tunnel boats (whether you are referring to the small racing variety or sea-going catamarans) are displacement hulls and only use about a third or less of their "underhull" area to generate air compression, or air support. The Sea Ski uses it's entire "underhull" surface to generate air compression and, thus, takes friction off the planning surfaces. The skis only engage at speeds that are nearly equivalent to top speeds for many mono hulls. This is why this design should be appropriate for vessels of at least 10 tonnes doing speeds in advance of 65 knots (120 km/h). If you are talking about small racing tunnel hulls, they are much faster, but if they hit a ripple they are cactus. Sea Ski vessels operate in serious sea conditions at very fast speeds as do catamarans at very much slower speeds as the seas increase . The "square boxy" look is because it is a prototype and the very cheapest way for a penniless retiree to test a theory. If that's your basis for "big noting" yourself, poor fool you. Also, the $270,00 figure was a bad mistake by the media. The actual buy price is cheaper then traditional hulls on a space basis.

[tunnels]

sorry tunnels are not cats and cats are not tunnels . tunnels ride on a cushion of compressed air passing under and between the two hulls ,the shape of the tunnel and the shape of the 3 surfaces within the tunnel is what makes or breaks a tunnel boat .
Small race boats ,yes been there done that !! , 16 foot tunnel family boats ride and perform like no other boat on the water !!
The 22 foot tunnels are the most fantastic boat you ever ridden in and will go round corners like they are on rails !!. The 30 feet with a pair of 200 yamaha's can be a beast but also absolute heaven and the ultimate fast cruising boat .
Do i know tunnels ? yes!! I spent 2 years working for a company and thats all we produced were tunnel boats !!i rubbed sholders with the designer and picked his brains during the set up and development of offshore race boats ,formular 1 circut race boats or just get up and fly fun ski machines !!
The company had a range of everyday family boats !!,all were breed from race boat designs.
Cats are in a field all of there own and what ive seen they dont interest me in the slightest . THEY ARE NOT TUNNELS !!

[SeaSki designer]

OK, Tunnels, at least I know what you are talking about now. Many people describe catamarans as "tunnels". I agree with what you are saying as to ride and "riding on rails", but they are still a displacement hull and as such are good on good surfaces. Have you done a sustained straight line run into the worst approaches of a 1.2 metre sea (4ft) at speeds above 70 km/h (say 45mph)?
I personally do not know of "tunnels" that can fly in the face of big sea chops and/or swells, but would welcome information (collaborated) to the contrary. It's night time Australia so will get back to you a.m., if you like, but please answer the above accurately.

[tunnels]

These are the 3 boats small had twin suszuki 55 s the 22 footer a pair of yamaha 140 vee 4s but should have been v6 175s , and the 30 footer with a pair of 200 yamahas . trimed out and going for it was 70 mph plus
not displacement hulls ! that cats not tunnels . dont know where you got you info from !tunnels are like a deepvee mono slit apart . like i said the shape of the tunnel is the whole secret to how it goes and how it performs in all and any sea conditions the bigger the sea the faster you go the better it goes !!
Been out in some rought and scared the pants of me first time but the guy behind the wheel was a race boat driver and he just pushed the throttles down in 1.2 meter choppy seas and it just jumped on top of the waves and went for it like it wasnt even there , no thumping or banging just a fast reasonably smooth ride. Never go to be in the 30 footer but it was even better because of its shear size and power . Cats dont even get close and a mono is history .
I had the use of the smaller boat quite often and at 6 mtrs would run rings round a 20 foot plus mono !
I live in china and have all my stuff in storage in New ZEaland theres more pictures and video of most of what i have written about .

The smaller boat it was possible to set a comfortable cruising speed and point in the direction you want to go and dont touch the wheel !! just sit there and enjoy the ride in any direction in any sea at a comfortable speed and thats just the small boat the bigger boat 22 foot was the same but would handle bigger seas and same just let the wheel go and enjoy the trip !! there was a fishing open version of the small boat with a single motor was the same point and go no need to fight with the wheel no need to constantly be correcting where its pointed !,up waves or down didnt mater !!.