Speed Boat on skis

I read the article, congratulations on getting the exposure.

 

Sea Ski boat design

A few people took the time and trouble to offer advice and comment on our 'radical' boat design, the Sea Ski. Our website has now been revised and offers a preview of the production model and also some amateur video of the prototype trialling in 1m to 1.74m (3.3-5.7') seas a few weeks ago at Pt Danger, east coast Australia. Hope this helps people understand the scope of the design.

 

Big undertaking there Trevor, best of luck with it. One thing that occurred to me is that the vertical supports for those skis would present a lot of wetted area when cutting through waves, would it be better to have struts instead ?

 

I checked out your new website. I liked the CAD renderings of the production boat.

I do think the whole tagline about competing with highways is an odd way to market a boat. Even if the travel time is the same, a car with average gas mileage will burn about one eighth the fuel for the same journey. Its not really comparable. Boats (Sea Skis included) are not in a position to compete with cars as a useful form of transportation for the vast majority of people. Unless you work on the water, boats are a toy while a car is a necessity. I would think that you would want to consider what type of boat is the biggest competition and then layout the case for why the sea ski is better. Making a comparison to highways strikes me as pointless.

From what I can see in your videos, the boat is fast and smooth riding. The biggest problem I saw in your videos is that spray generation, particularly in waves, seems like it would be a constant nuisance. A normal boat hull throws spray away from the hull. The skis seem to shoot it forward and then back on the boat. I assume that is one reason why you have a full canopy. The downside is you lose the "wind in your hair" enjoyment of being in the outdoors, which may be downside for some small boat users.

I think your concept is innovative and exciting. I appears your design does offer some advantages over a conventional boat and there could be a niche market for it. The improved speed, rough water performance and fuel economy could be pretty attractive to fishermen. When drifting or trolling the skis probably damp the motions compared to a regular boat. Dive boats to the reefs might be another example of where you offer distinct advantages. You probably want to zero in on a market segment such as that and focus you design and marketing to go after it.

I hope you don't mind the unsolicited advice. Good luck with your boat.

 

I'd like to try shocks and springs w/skis, since skis have very

low un-sprung weight it might work good.

SeaPhantom has them, but I was thinking plain flat skis to get all the advantage of flat, non-Vee planning.

 

Some good points made there. I wonder what speed has to be achieved to get it up and running properly, so that flat belly is far enough off the waves. If it really has to be gunned to stay up, in rough conditions that would present problems. And I also noticed the spray, maybe modifying the entry could reduce that.

 

Mr. Efficiency: thanks for the encouragement. We did try struts initially, but filled them in to increase inducted airflow. That zone seldom presents a wetted area problem in waves so it seemed a lesser consideration.

Intrepid 71: Firstly, thanks for the marketing directions -- all "thinking" advice is welcome and very much appreciated. The "boat/car race" is there to stimulate media attention locally (Australia), being the best/fastest way of getting information 'out there'. We are fairly confident fuel consumption should be closer to 3:1 than 8:1 compared to big cars. Spray is a slight problem in rougher conditions, but better then having to reduce speed when conventional bows are plunging down into troughs and smacking into waves. However, it is easy enough to produce an open air, cut down model for the 'wild at heart'!

Squidly-Diddly: Yes that thought has occurred to us on occasions, but too expensive for small vessels (under 30ft). Perhaps, one day, on larger versions? Another Australian company (nauti-craft.com) does use springs and shock absorbers on their prototype, but I think shock absorbers will take a much heavier hammering in sea conditions than in the big rallies, i.e. Dakar!

 

OK, I get it, you want that skirt to channel air better. I notice you used a jacking plate, what difficulty have you had with engine height, and is propellor selection important ?

 

Mr Efficiency: We installed an hydraulic jacking plate to allow us to play around with various propellers while underway. The production model will not necessarily need a jacking plate as engine height is not much of an issue, unless you want the blades to break the surface, which does add to the speed. Propeller selection is more relevant in terms of pitch than other considerations, in as much as the design allows more pitch than would otherwise be the case. Hope this helps.

 

You may turn out to be the Bruce Harris of your time. Bruce of course was the originator of the Shark Cat, a little further north of you there.

 

Thanks for the accolade, Mr Efficiency, but got a long way to go to reach such illustrious heights! I sought out Bruce Harris nearly two years ago and showed him what I was doing and he very generously gave his encouragement and some pointers. His Shark Cat, of course, is now the Noosa Cat and I believe the latest models are earning high praise from the boating columnists. Sounds like you might have some designs under your belt?

 

Designed and built a couple of boats over the years, but only on an amateur basis. The boat game is pretty cut-throat as you would realise, and you really need something exceptional to stand out from the competition, otherwise the outlook is not encouraging. I hope you find all your work is rewarded.

 

I confess to being a complete amateur myself, but that does not necessarily preclude individuals from coming up with workable concepts, just implementing them to some degree! Would like to know your whereabouts in Oz. Would you care to contact me on seaski@internode.com.au?

 

Sending you a PM, e-mail wouldn't work for some reason.

 

Using the 1.41 km/l value on your website comes to 3.3 mpg. Even a Chevy Suburban, which is about the biggest SUV in the American market, gets 21 mpg on the highway. I assume things are similar down under. So you are looking at 6.3 to 1 there and a much higher ratio against a typical car. This isn't a slight against your boat. 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.

Regarding the spray, there may be a way to deflect the spray outwards instead of forward without compromising the fundamental design benefits of your air-trapping skis. For example, if in plan view you cut the ski at a 45 or 60 degree taper and put the pointy tip on the inboard side of the ski, you could keep the same cross section, but push the spray outboard instead of forward when you cut into a wave. You could also put a wedge on the inside wall of the forward tip of the ski to further induce an outboard spray pattern an hopefully reduce the sneezing effect, which shoots the spray forward. Just some ideas which you may have already considered. Good luck with the design.