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Old 08-30-2006, 08:14 AM
  #41
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Default Re: step hull

Hi Dean;

At the Toronto show we had Evinrudes on it because they paid a promotional fee to do it. The boat was rigged with Merc 250xs motors. That boat has run 90.1 mph and thats on 87 pump gas. Now we are all excited to get the first I/O version in the water.
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Old 08-30-2006, 10:38 AM
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Default Re: step hull

TUFFBOAT:

We're looking forward to seeing the I/O version. If you are interested in competing with the best single engine boats in offshore racing , give me a call.
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Old 08-30-2006, 01:22 PM
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Default Re: step hull

Just curious why don't you see people with hydrofoils?

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Old 08-30-2006, 01:40 PM
  #44
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Default Re: step hull

Quote:
Originally Posted by Excalibur Dude
Just curious why don't you see people with hydrofoils?

People feel more stable on waterskis.

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Old 08-30-2006, 10:08 PM
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Default Re: step hull

That is something to be proud of Mark. When I looked at the hull and how you did the bottom the first thing I said to Cindy was I bet that boat will fly!!
I think I will do the things you showed me on my new hull. I was really wondering though when I came on this site if I did the bottom just like yours and added the steps in , it may be great. I am pretty much scard of the step hull thought. When I first started out with my first boat I was under the impression that a smooth botton boat was the way. NowI have had people tell me getting air under them in much faster!
Thats why I was realy happy to find this site. Talking to people that think they know and have never done it ,is not near as good as the people on this site that lives it. I have learned don't talk to the guy just going into the bush ask the guy coming out the other end.
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Old 08-30-2006, 10:32 PM
  #46
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Default Re: step hull

what is it that you are doing? are you building a boat from scratch? if so got any renderings? Would love to see it.
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Old 08-30-2006, 11:08 PM
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Yes I build my boats from the ground up. I start out with a buch of lumber on my shop floor and go from there. The last one was a plan for a six meter race boat and I made it in to a 22ft bass boat. Now I am going to add another foot and go from a 18 degree to a 24 degree bottom. My wife and I have had a push pull thing happening on the length.(All in fun)I was going to go 24ft and she loves our 22ft so I have decided to go 50 50 with her.The beem is only 7ft and the length will be 23ft.
All of these bass boat compains build boats for mill ponds. (not like our ponds we fish on) Ihave seen guys in the hospitl peeing blood for a week after a ternament on Eire. That is how all the bass boats ride to. I have drove almost every comanys boat and after having a boat like a offshore hull I will never go back. My 22ft will still go in 12inch of water the same as there boats but does and not kill you getting there.
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Old 08-30-2006, 11:20 PM
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Default Re: step hull

Quote:
Originally Posted by Excalibur Dude
Just curious why don't you see people with hydrofoils?
Soon......
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Old 08-31-2006, 08:31 AM
  #49
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Default Re: step hull

Dean;

Because of the way the water moves ( displaces ), I think you will find that there is quite a bit of air under a straight bottom boat. By the way, my straight bottom boat has aeration tubes in it, just trying to get both worlds. If you re-read the thread listed near the top, all this stuff was covered by T2x alreadly.
There is not just one good idea, lots of different things work with completely different approaches.
With your boats you have the ability to try, and then change your mind, and try again.
Like the Boss said to the hit man when asked how to kill the target..."go with your hart".

Mark
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Old 08-31-2006, 02:58 PM
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Default Re: step hull

I expected someone to answer your question by now, but no, just joking around. That's OK, but here is the actual answer:

The bottom of a planing boat is like the bottom of a wing. It works by creating lift. It creates lift by having a positive angle of attack. It works well if there is a lot of lift for a given amount of drag: a good L/D (lift to drag) ratio.

Lots and lots of tank tests and full size tests over the last 150 years have shown that the best lift-to-drag is achieved at 4 to 5 degrees angle of attack -- the keel line sloping upwards from transom towards the bow at 4 to 5 degrees.

Without a step, this means the boat needs to balance on the transom. This means all the weight needs to be as far aft as possible. This can be done, especially with an outboard on a small boat.

With a step, you can have "two wings" -- one forward and one aft, both at 5 degrees angle of attack, allowing the center of gravity to be much further forward. This is much more practical for inboard powered boats, or boats that carry lots of gear and/or people forward of the transom.

Over the last 80 years, many tank tests and full size tests have also shown that the best hull shape is a monohedron -- constant deadrise across the planing surface. Its OK to let the deadrise increase a lot forward, because its out of the water at speed, so no penalty in drag, but you get a benefit by having less severe pitch accelerations in a sea way. Any movement that is not forward is a waste of energy, therefore a faster boat in waves has more deadrise forward.

It took about 75 years of step boat experience until tests could show that the optimum number of steps is one. By the 1930s, the well tested designs in fact all had one step. You'll never see a seaplane with more than one step, for example. However, having more that one step, such as the two close together used by Fountain on its bigger boats, does help as it allows the two "forward wings" (planing surfaces) to have a higher aspect ratio (shorter length .vs. span) and lift-to-drag improves with aspect ratio.

Why not have a zillion steps, like Outerlimits, Nortech, and so on? Why are the boats with lots of steps always slower (unless they are lighter and stiffer, as the new Skater boats)?

Because, as was observed during the 1910's and 1920's and finally understood by 1930, having lots of steps causes the lift to be very unstable longitudinally -- the boat porpoises unless things are done to add lots of drag (drop tabs, or do like Nortech and add way too much rocker forward).

Having lots of steps (as on Outerlimits), or even having the front two steps widely spaced (as on the early Extreme 39 hulls, and on Cigarette hulls) leads to control problems that crop up suddenly. This was well known 80 years ago, and is again being demonstrated by these poorly designed hulls today.
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