Originally Posted by Andy Moore
Are Scorpion RIBs good in the rough stuff?
They're exceedingly good. It's an unbelievable experience, and as well as being good, they're very forgiving. I've been in many other RIBs over the last few years and I'm always pleased to get back on board Blue Ice. There's good reason for all of this... if you read up on how hull shapes affect performance, and experience a badly designed hull in action, all becomes a lot clearer. The great following sea performance isn't due to bow buoyancy, in fact the reverse is true. The shallow forefoot is one of the characteristics which helps, although this is also a small weakness in the design in other respects, as this gives the hull a tendency to drop the nose if you're nervous with the throttle, and will porpoise slightly in a slight to moderate sea. This can be overcome very easily with more throttle! And because the hull is a warped V... actually it's a very
warped V.... the bow can be plunged into large waves at high speed with very little drama - the sharp and shallow forefoot just carves into them. Warped V hulls aren't the be-all-and-end-all of RIB hull design though.... the 6.5 Scorpion (not made any more) isn't anything like as good as the 7.5 as it just doesn't have the pitch stability, and the hull comes into its own at 35+kts. Almost impossible to keep up that sort of speed in a 6.5m RIB in a rough sea. So the hulls shape doesn't really suit smaller RIBs. And in a bigger RIB, if you had a Yanmar 300 diesel with the appalling turbo lag, you might find it difficult to use the throttle to have perfect pitch control in a heavy sea, so you'd really have to make sure not to drop the bow. Even worse, if you had an iffy Bravo 3 leg and the boat's owner was nervous of making fast progress in rough seas, you wouldn't be able to exploit the superb performance from the RIB.
But I digress! Other features which make the Scorpion hull perform well are the fact that the tubes don't drag in the water - this can produce a horrible yawing sensation that many people mistake for chine walking, but in some cases is actually the RIB bouncing from one tube to another. And the tube attachment has a rebate so that the water doesn't work into the glue which fixes them to the hull. There is a vertical rise above the reverse chine which is essential for hull strength (without this vertical section, the hull would be like an ironing board and have poor lateral strength) and the reverse chine itself is very important... water displaced by the V of the hull is forced against this to give lift, and the hooked profile of the chine maximises this, and keeps the occupants of the boat dry. One particularly pleasing piece of design is the fact that the reverse chine tapers out to the bow where it's not required.
It's no coincidence that all the major UK endurance records (Round Britain under 30' , Round British Isles and London-MonteCarlo) are held by Scorpion RIBs.
"Slim" tubes (tapered ones) are an option - we have standard tubes which are just as fat as on most other makes. I doubt that they make any difference to the handling at speed though - only the performance once you're full of water!