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Old 28 July 2004, 09:33   #21
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Hi

Certainly we are trying to improve efficiency by introducing the steps, but also using them to get a good level ride at speed and good acceleration.

Traditionally stepped hulled boats have tended to have a few problems at lower planing speeds and often in turning, when the boat looses some of it's stability. I have designed a number of successful non-RIB race boats with steps and modified my approach for our production boat due to these reasons.

We are pretty much unique (as far as I know) with our steps in that they are tapered. The forward step actually tapers to zero at the chine and the aft step tapers to a lesser extent. So at speed the boat is working as a stepped hull - but as speed decreases - or in a turn - and waterline beam increases so the step effect decreases. I believe this has given the boat an excellent combination of speed and handling - but is of course only part of the hull design and much work has gone into other areas of the hull as well.

Adam
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Old 28 July 2004, 15:16   #22
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Quote:
Originally Posted by Adam Younger
Hi
We are pretty much unique (as far as I know) with our steps in that they are tapered. Adam
Adam, Will Smith of Phantom boats USA (nothing to do with Phantom UK) has a similar design, no step is visible on the chine, it all happens on the lower running surface.

they've just set a new 'A' class speed record at 101mph
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Old 28 July 2004, 20:40   #23
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Hi Jon

Actually just got my copy of Powerboat magazine (USA) - and been too busy to read it so far! Will be intersting to see the Phantom (USA) steps in more detail. Certainly different to their previous boats.

It (step arrangement) could also be done to initially give some negative pressure in the step area and thus draw some air through and ventilate the step more effectively - cannot really see enough from the photo's.

Adam
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Old 30 July 2004, 12:51   #24
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Another picture - showing tubes coming into play when turning
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Old 30 July 2004, 12:54   #25
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and one more shot!
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Old 30 July 2004, 12:59   #26
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what you think of the suzzi adam.... what one is it on the back and how fast??

thanks
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Old 30 July 2004, 18:33   #27
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I'm gonna have a wild guess here..... DF140?.....
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Old 09 August 2004, 05:52   #28
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Apolgies for the long delay in replying - been on my travels and just got back!

Very impressed with the Suzuki (yes it is the 140) - first extended spell of boating I have had with a four stroke - and all very enjoyable. Only problem has been the standard Suzuki prop which is really pretty poor for getting good speed / acceleration out of the boat. Although we are not exactly a standard hull so I would expect to be looking at something a little more specialist anyway.

We have modified the prop a bit and adding some cupping which has seen an improvement. We are now running 50mph with it. However I do have a stainless steel Powertech prop on order that will hopefully give a bit more speed and general grip - for not too much expense. Should be here any day now!

Will post some more details when that arrives and we do some more testing.

Adam
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Old 09 August 2004, 07:14   #29
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Adam great RIB. Said it before. Would love to have a test run on it.

However, can you explain a few more things about the stepped hull and its advantages/disadvantages over the conventional hulls?

The reason I ask is that a few weeks ago we were having a drink and we were talking about boats and in particular how fast stepped hulls are.
A naval architect and engineer specialising in the design and building of fast hulls (20+ years now) for two VERY well known - one Italian and one American - hi performave RIB and hard boat building companies explained to us that although the majority of stepped hulls are great and very fast than conventional hulls in the flat(ish), in the rough they do not perform as well as conventional hulls and are slower - he was talking about high performace RIBs and hard boats.
As I understood it has something to do with the air being trapped under the steps, various forces that work the wrong way with the waves presure and a few other parameters that I do not recall.

PS: If you don't mind can you advise what the angle of attack in the bow, mid ships and at the transom?
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Old 12 August 2004, 09:18   #30
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Hi Manos

Certainly agree that in many cases stepped hulls do not perform as well in the rough, especially so in heavier boats where you are not running race speeds and set-ups. Infact far too many people have really just been copying step arrangemnets from other boats / designers and do not really understand what is fully going on.

I have taken quite a different approach with this RIB (and some other boats that I have designed for other companies) and it's steps. The steps are notably tapered so that the low speed and handling characteristics are still very good - whilst still getting some of the benefits from the steps theirselves. This is probably quite different to what I would when designing an 'out & out' race boat, although we do learn a lot from our race boats. Indeed the approach I normally take with the raceboats is to create hulls that can keep up a high average speed with good handling rather than the ultimate calm weather sprint speed - and this works very well for us.

Certainly the demo boat is always available for tests - so if you are over give me a call.

With regards to 'angle of attack' - or deadrise - the forward sections are just over 45 degrees and in the stern we have a pad effect and shallow sections outboard of around 20 degrees. This is possible with the stepped hull as we a very level running boat due to the steps thus allowing the bow to work. The hull was also developed to be powered by medium range engines, anything from 90hp to 140hp.

Adam
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