Hull steps good, bad, dangerous ?

[CUDA]

STEPS in the hull , good or bad , seems to have detrimental effects on V bottoms turning ability, tunnels don't seem as effected? Thanks jj

[afr]

yes they effect handling in the corners on v bottoms but increase speed by attimizing the water touching the hull its more in how you use them and why that makes them good or bad
im pretty sure we were the first ones to ever use a step on a v hull

why do you ask jj??

[Mark Poole ModVP]

Velocity experimented with steps on the 22' in the 80's but they did not work probably because they were not designed to allow air in. Where you introduce air on the bottom is critical. After all, water pressure works with the shape of the hull for lift. Put air bubbles where they should not be and you increase drag.

[CUDA]

The actual advantage of steps is the use of the high pressure lift characteristics of a planing surface. The highest pressure is developed at the front of the water contact, while the rest of the surface creates more drag; by shortening the length of the wet surface area by using multiple steps, the overall drag is reduce while the lifting characteristics are enhanced. The most drag-free planing surface is short and wide, and steps allow the designer to create multiple short surfaces, with less drag, at least that is the way I understand it? Any one else.

The reason I started this thread was my concern of steps on V bottom boats and all the stories I have heard about them losing control while turning, and I had one such occasion my self , but I was turning VERY sharp.

[afr]

you mean like this but in reality it was a trim tab problem that casued thishttp://img.photobucket.com/albums/v625/phragle/brCaZJ.gif

[CUDA]

That is one well built boat, to withstand that much pressure and not fracture.

[afr]

did you see this yet
http://www.youtube.com/watch?v=HA1q5vGP5wo&feature=player_embedded

http://www.screamandfly.com/showthread.php?219506-How-to-drive-your-boat-upside-down....and-recover!

[Mark75H]

I think there is another advantage that its easier to balance most things on 2 points rather than one. Steps were first popular in the 1930's and fell from favor for decades before being revived.

You don't see many steps on real tunnels and tunnels support much of their weight by air rather than water contact; all of their water contact is less critical after they are in air support/aerodynamic mode.

Anything can be designed wrong or operated wrong and become dangerous.

[afr]

aha well i was not born in the 30,s lol so there ya go neither i nore Mr stepp were the first to use a stepped hull

thanks sam
i said it before there is nothing that has not been done before to any boat long before you ever even thought of it

[JUPITER PULSARE]

It's not the steps that are dangerous, it's where they are placed and how they airate the hull. Most of the dangers of step hulls come from driver error. You cannot tuck the drives in and turn the boat sharply without the stern spinning out...many inexperienced drivers found out the hard (and wet) way by entering a corner too fast with the drives tucked in, 180 the boat, as the boat slows it's spin it slowly rolls over and throws everyone overboard!! When you enter the turn with the drives tucked in you are pushing the stern upwards to the point that the stepped portion of the hull loses it's edge allowing the boat to spin...

[Sam Baker]

Throughout my racing experience including helping my Dad when he raced, etc. we always filled in steps. One thing people complain about on the Mirage Quartermaster (as an example) is that when they land after launching they sort of "stick" to the water. We added a board on the center pad that effectively filled in the step and that eliminated that problem. We've always filled in steps. It can create a "suction" from not being vented. Certainly for drag racing, in order to get the boat up on the pad immediately, the boat will respond better to hydraulic pressure (since you're not going fast enough for aerodynamic pressure to hold the boat up). So, the more pressure you can build quickly to get the boat up on the pad, the better. Steps inherently RELIEVE hydraulic pressure and create aeration.

On a large boat that doesn't have the ability to get loose and truly up on the pad, it will make it faster, but on boats like we run, they seem to run better without steps.

[CUDA]

Sam I believe the problem with the Quartermasters step is it was just a cut out , with the front and rear area on the same plane, not a true step, maybe a through hull fitting with a hose attached might have helped.
To be honest I've been waiting for the SHADOW to add his knowledge to this thread, since (I believe ) he was one of the first boat builders to bring back the Idea into mainstream boat design. The SHADOW knows

A cut and paste
Understanding design and performance of Stepped Hulls
So many readers have asked me about “Stepped Hulls” and with this in mind, I thought it might be a good idea to write a brief article about this concept and design feature on the hull bottom of a planing hull.
Stepped bottoms have been used for a very long time to improve performance. A very famous design was Maple Leaf, built in wood in 1912, and since then many successful racing hulls have had this type of bottom. One can say that it is a further refinement of the deep V-Hull.
What is a step?
Steps are breaks in the hull intended to reduce the amount of hull surface in contact with the water. Steps can run straight across the hull (although these are structurally weak and not often seen today), or they can be V-shaped, with the vertex facing forward or aft. They will have large apertures on the outboard side of the hull to allow air to be sucked down into and ventilate the step. In general, the speed increase of about 10 to 15 percent can be expected from a stepped hull over a non-stepped hull with the same power train.
The reason why the stepped hulls are more effective is that the weted area is divided into several smaller areas each with a large beam compared to the length;
Short, wide (high-aspect) surfaces are more efficient than long, narrow (low-aspect) ones in terms of frictional drag on water. Lift generation is just far more efficient with a large beam-to-length ratio surface. So, the idea behind a stepped bottom is to reduce wetted surface by allowing the hull to plane on two or three high-aspect planning surfaces rather than one large, low-aspect surface.
And the popular notion that any added speed from a stepped bottom is due to a layer of bubbles undoubtedly reduce frictional drag to some extent, but the real saving is in minimizing the hull area in contact with the water, specifically by presenting two or three wide and short surfaces to the water instead of one long, narrow one.
How its works!
As I have explained in a previous article on hull shapes, the lift production is more efficient for a surface, with a small length to beam ratio. (The planning bottom is different from a wing, where it usually does not help splitting the surface into several tandem wings.) The increased lift generation capability means that the total weted surface may be reduced, as well as the friction. My drawing shows that the region behind each step has to be ventilated. Air thus has to be sucked into this region in sufficient quantities. Normally this is not a problem since the pressure is very low, but it’s extremely important that the air supply is not cut. New air is continuously needed since the water entrains the air behind each step. This may be achieved most simply by extending the step sideways to the open air at the hull’s side.
When does it starts to work?
In general, data indicate that if a boat can’t cruise easily at close to 30 knots or more, it can’t go fast enough to ride up on hull steps, so steps would only add drag. More specifically, this means that a petrol-powered family cruiser with steps should be able to cruise fully loaded at 30 knots, not just reach this speed at full throttle. Otherwise, the extra cost of tooling and the added time and cost spent laying up a stepped hull is wasted, and the stepped bottom is just a marketing gimmick. Some runabout builders even carve out a little scoop at the chime amidships, which I suppose is meant to suggest that the bottom is stepped, when in fact the bottom is as straight as an arrow.
Downside to the step hull
This principle is somewhat dangerous.
since the openings may be closed temporarily (and momentarily) by waves. When the air supply is lost, a backflow occurs behind the step causing an excessive increase in resistance. The speed thus drops momentarily – a dangerous situation, which may even cause injuries to the crew. If the supply is cut only on one side the hull will turn abruptly, and possibly even capsize. To avoid this problem air is often sucked through openings well above the waterline,
or it may be supplied through tubes in from deck level. Another possibility is to discharge the exhaust gases through the step. In this way the gases will be sucked out, improving the efficiency of the engine.
Builders often provide large inlets to the areas behind the steps, and a few even provide air paths through ducts that lead to the trailing vertical edge of the steps.
Since the lift is now spread to several surfaces along the hull (see drawing) the longitudinal stability becomes very large. It is difficult to change the trim. This is no problem in smooth water, but in seaway the hull may tend to follow the contour of the waves. Larger hulls may acquire a tendency to bump into the next wave, making the ride very uncomfortable. Smaller boats, which tend to jump between waves, are not so affected by this problem. Another effect of spreading the lift to several efficient surfaces, one after the other, is that the transverse stability may be put into jeopardy. The hull rides high on a very narrow set of weted surfaces. At very high speed some designers have chosen to take advantage of the aerodynamics of the above-water part of the hull, using wing-like devices to keep the hull upright. Transom flaps may be fitted to the hull to control the trim. Temporary adjustments for correcting changes in the center of gravity may thus be made easily. The flaps may also be used to adjust the trim when the hull is running at off-design speeds, for instance in restricted waters or when the hull is under acceleration. This reduces the fuel consumption and, even more importantly, the generated waves, which may be excessive at these speeds. It is also possible to sue the flaps for adjusting the trim in a seaway to reduce the bumpiness.
My conclusion
Stepped hulls should be used by experienced drivers who know what the hull is likely to do in a seaway and in hard cornering, and who know how to react to the unexpected.

[Mark75H]

In short ... anything can be designed wrong or operated wrong and become dangerous.

[Rodney Nance]

I am not a hydrodynamics expert but what you guys are saying reminds me of something. When I got my 1/4 Master from Brad they were fast but when they broke over out of the hole the nose stuck and pushed water. I always thought it was the small frontal area causing it. Anyway I started tucking the motor way in on the launch with a fast trim and moved the weight around in the boat. Billy Eaves built us a prop and after that when Brickner or Bobby drove it the boat never knew what bottom it had under it until it got close to 1/2 track.:

[Sam Baker]

Yep Rodney. Mine did the same thing. It would come down and land with kind of a thud and stick. We added a 1"X8" board to the center pod (which essentially filled in the step) and then we added small strakes to the outside sponsons and that fixed everything. Made a big difference on how the boat took off and it also freed up the outside sponsons a little bit...oh...and it also fixed the "crabbing" of the boat that happens because of the wide, flat pad and no vertical surface on the outside sponsons.

[NPK2003]

I agree with Sam on the QuarterMaster. I bought Sam's boat and modified the hull bottom to an even greater degree over the years. The end result was that the boat is an animal out of the hole, even with a powerhead that is down on power, as mine often are. In my opinion, the trick with the QuarterMaster is to get the hull to carry the bow as it transitions to full on plane. After that, mine will run very similiar to an Allison with the outside of the rear sponsons out of the water. It takes a lot of effort to get it right, but it is worth it. You need to add a little lip to the pad end like an Allison to hold the nose down at speed. However, the more you do to get the hull to fly, the faster it comes out of the hole, but>>>>>as said above, the hull will not turn as well as stock. The rear kind of skips to the side in a turn at speed. But who uses a QuarterMaster for everyday boating anyway. Don't bother asking exactly what and how I did it, because I'll claim I don't remember.

[CUDA]

Nick what happen to my new steering????? 239 272 5613 jj