Stepped mono hulls.

[Simon.O.]

Furthering my research into hull designs we now look at stepped mono hulls.
I note that Americans in general do not have a lot of them but they appear popular in Europe. I am in New Zealand so am not leaning either way. My boating is about me and fun so I do not get caught up in rules or class sizes etc.

I basically understand that a stepped mono running properly will be on the keel ride step and prop thus becoming a 2 point hull, I also understand that setting them up is harder than a conventional mono which can be an art in itself. I have seen photos of some very unusual step shapes and want to know a bit more about them.

I am looking for someone who has a proven stepped hull that I can then use to take measurements and angles from to draw and build my own. Gerwin, I hope you are reading this ??

Feel free to e-mail me any photos etc [email protected]

So let's go. Stepped mono designs, tips, tricks, advantages, drawbacks, observations.

NO Rule debates please.

[H&MWill]

My Triton was a stepped hull. Fast on the straights does not turn well.

[Meniscus]

Simon, hopefully Team Lindenau will post more pictures than what I've got:

http://forums.offshoreelectrics.com/...ead.php?t=7135

I can't wait to see the input response to your thread!

[Fluid]

Among the best racing stepped hulls are from Stephen Lindenau. I had great luck with the H&M Streamer, but it took awhile to get the right turn fin. Once I got the right size, shape and angle the boat turns as well as any racing mono but is quite fast on limited power.


The reason stepped hulls are not popular in the US is because there is only one racing class where they would even be competitive. Just not enough market for someone to develop a good US design. Even in europe the idea is usualy not just to get more top speed but to be able to use less powerful systems for long duration races.



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[Simon.O.]

Among the best racing stepped hulls are from Stephen Lindenau. I had great luck with the H&M Streamer, but it took awhile to get the right turn fin. Once I got the right size, shape and angle the boat turns as well as any racing mono but is quite fast on limited power.

The reason stepped hulls are not popular in the US is because there is only one racing class where they would even be competitive. Just not enough market for someone to develop a good US design. Even in europe the idea is usualy not just to get more top speed but to be able to use less powerful systems for long duration races.
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Jay. Thank you, that is the first explaination I have read yet as to why the stepped monos are popular in one place and not the other. It is interesting what you say about the performance ( I highlighted ).

I will give the steps a swerve for now and concentrate an a more conventional mono. I need a winter hull for when the pond chops up a bit. Riggers and chop is not my idea of fun. Cats and monos come out to play.

[Simon.O.]

Right, I am ready to cut the bottom off the mono and start again as a stepped hull.
I have read a bit and seen a few photos and have sent a few PM's for some advice.
I was happy to cut the bottom off my small cat to try step designs and I learnt a LOT from that experience.

The most critical point I need to know is whether I run it on the front ride area and the prop like a hydro ( option A )
or if I get the rear of the hull to sit on the water too.( option B )

I can see benefits and dramas in both variations but would like to know which is prefered and why.

Worst case is: I will cut this hull like I did with the Cat and make it so that I can stick bits on and cut them off until I get to a point where I am happy.

I have said it before, I have a lot of wood, adhesives and time.

Let's see how this pans out. It will be for my bigger 4S mono 29-30" long.

[G Doggett]

I would go with option B so that the hull rides on the steps and the transom.
My understanding is that when a stepped hull is planing as designed all the trailing edges of the steps are in contact with the water.
Hydros can support the rear of the hull on the prop because the c/g is well forward with very little weight on the prop.
DV, monos and cats have the c/g about 30% from the rear, as you know, so the last few inches of hull support the hull at speed.
IMO the prop should just be pushing forward, not trying to support the hull.
Also a prop riding DV would be a real handfull in a turn !
Just my 2 cents worth, but don't let me stifle your creativity mate.
Graham.

[lomdel]

One of the most beautifull stepped mono hulls IMO is the current Lucas Oil P1 Offshore racing boat. (It recently almost sank...) It truly is a beautiful sleek design with a lot of small steps in the hull bottom.

[Fluid]

I strongly suggest that anyone take the time to understand how steps work before trying to design a stepped hull. I'm not trying to be mean here, but the question about ride attitude would be answered with a cursory knowledge of step function. I learned the hard way years ago when I started designing stepped hulls. There is no reason for anyone else to make the same mistakes I did.

Here is a good description of step function and design:

TBPNews #88 - Oct 8, 2005 Feature - "Step by Step" - step design in powerboats.

http://www.aeromarineresearch.com/join.html

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[obrien]

Hull design B is definitly the one to use. One thing you can try when start playing with the steps, is the different angles of attack on the second running surface. That is one of the ways Reggie Fountain had made his boats so fast. Granted he is using a double stepped hull, but just trying different angles on the running surfaces makes a big difference. Also, the location of the step itself will make a big difference. Some stepped hulls will bring the 2nd running surface back down in line with the first running surface, only using the step as basically a slot to help aerate the hull for better speeds.

[lomdel]

...Here is a good description of step function and design:
TBPNews #88 - Oct 8, 2005 Feature - "Step by Step" - step design in powerboats.

http://www.aeromarineresearch.com/join.html

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Extremely interesting reading source Jay, thanks! A lot of usefull articles to learn a lot from...

[Gerwin Brommer]

There is such thing as a "golden rule" for a SINGLE stepped mono.
It should be at approx 40 % of total effective hull lenght.(measured from the back)
Option B is my choice aswell.
Major advantage stepped hull : you can use a solid driveline, just put the motor in front
of the step. In case of a 2S or 3S mono , leave about 3-4mm "air" under the hub of the prop.
Front of the prop should be at about 10% of total effective hull lenght.
Stepped hulls are propwalking easy. Therefore you could position the whole driveline offcentre. Or let the drive exit the back in the middle and position the motor a bit to the right.
Front of the rudderblade starts where the prop ends (if you look a the boat from above)

IMO one of the best stepped mono's : Hopf Gozilla. Sold mine. And bought it back, should arrive in a couple of days :

[sailr]

Stepped hulls are illegal in the US except in offshore. Very limited. It's too bad because the stepped hulls run great.

[rockwerks]

I have a 21" stepped mono hull (kevlar) that Im working o for N1 offshore SAWS. Have a LMT basic xl 3100 running with wire drive and a small 2s 25c lipo, (car) esc and specktrum micro receiver. micro alum hardware, everything light as possible.

[Gerwin Brommer]

Why only 3100 rpm/V ?
On 2S, what prop do you have in mind ?