Stepped hulls

[Roy Smith]

I am looking for a new rib and i have seen a few with stepperd hulls they are more exspence than normal but could some one tell me what you would gain by having a stepped hull.
80% of my ribing is done in or very near to the solent and we do a fair amount of wake boarding in langstone harbour
Roy

[peteb]

Roy, Don't know about RIB's but I have the Larson's Duo-Delta Conic hull that's designed to give quicker hole-shots with less bow rise, this together with the stainless duo props I have give fantastic results, including better speed, fuel economy (as it rides partly on a pocket of air) and great handling. I do believe that Mark Pascoe builds stepped hull boats, as I got my trailer from the person who supplies him, they require a slightly different set up with the stepped hull.

[qcamel]

I have a stepped hull on my RIB and my understanding is that the hull shape encourages the stern to sit higher in the water when running and also to get onto the plane quicker.

However I bought this boat as seen and so did not spec the hull, I wonder just how much differance it really makes. I do know that the turbulance confuses my depth gauge and so I lose its reading above about 15 knots.

Gets some attention when on the trailer, looks a little odd most people think.

[slimtim]

Roy,

The man you should speak to I think is Adam Younger on this Forum. His company is K4+ (www.K4plus.com) and they have recently developed a stepped hull RIB of 6.5m. It has tapered steps to aid cornering stability at high speeds (which is a problem with normal stepped hulls I believe) but still keeping the advantages of steps in a straight line. I think this is all right, someone may correct me!

Adam, If you read this how did you do in Cardiff then?! I would love to take you up on the offer of that ride in the RIB sometime

Cheers

Tim

[Seb]

My understanding of stepped hulls, although limited, is that they basically help reduce the wetted area of the hull, thus reducing drag which ultimately leads to greater performance.

Also, if you can imagine driving into a head sea with a stepped hull, each wave that passes along the keel will cause the boat to alter its angle in the water and will allow higher speeds to be maintained without the need to drive 'on the throttle' to such a degree.

i.e. As each individual step in the hull passes over the crest of a wave, the boats bow will drop by the depth of the step. If this is then repeated over numerous steps, the bow will gradually drop as the wave passes beneath meaning that easing off the throttle may not be required which in racing, is obviously beneficial.

My be wrong but it kinda makes sense if you can understand my explanation!!

[Roy Smith]

So if i am not racing it wont realy help me ?
Thanks to every body for replying.
Roy

[peteb]

Your right Roy, it's not the type of hull for the pipe, dressing gown and slipper man

[Richard B]

This might be of interest: http://www.ocke.se/motorboats/technology/index.html

[codprawn]

Read an article in a Rib mag where they said that an inexperienced driver could have big probs with a stepped hull - apparently they can suddenly skid out of turns or even hook and chuck people out.

[peteb]

I'm still alive (Lucky I bought those mini flares to keep in my jacket though )

Joking apart, my hull is very responsive and I have never been almost thrown out, a RIB may be a different matter.

[Carl]

just dont turn them to hard or in a split second you will be in the drink wondering what happened,but of course this is in race conditions