Hi,
I think there is another load of chat on this topic elsewhere on Mayhem, however, spray rails, chine rails or strips and so on were experimented with by The British Powerboat Company, Vosper and Thorneycroft as they developed fast patrol, rescue and torpedo boats used in WW2. They were tried on the side, underneath and all different shapes as well. Most of the MTBs settled on a chine rail that was basically square in section but perched on the side and following the chine up to nearly the higher angle at the bows. The sloping sides of the craft gave the bottom of these a slight downwards tilt.
In the late 1950's and early 60's the British Powerboat Company had merged into the Fairey Marine company and they were now competing in racing challenges around Britain and Europe. Their Chine rail experiments were now angling down a bit more and the upper part of this rail was sloping down giving it an almost sloping triangular cross section, but still planted along the join between the side and the bottom of the craft. They also added additional strips which were used to deflect water down, lifting the boat and deflecting the bulk of waves hitting the bow at speed. These were called spray rails and are used a lot today in GRP hulls.
Further thinner rails were also fitted underneath the hull which stopped the boat sliding or drifting sideways at speed. Have a good look at any of the Fairey Boats of the early to middle 1960's. The Huntsman and the Swordfish designs show from 3 to 4 of these spray rails fitted and the boats tracking at speed was massively enhanced .
Most high speed racing craft, model and full size that are made in GRP have the rails moulded in and the transition to the flat part of the hull is faired in to make them smooth sided, not raised or planted on the surface so much. They are mainly of triangle section and the Chine ones are angled down quite a lot in some cases.
Early speed boats as we called them like the Riva's, Chriscraft and so on were built before rails were common and they are rarely seen in a true scale version. These boats can lift quite well but are still regarded as 'Wet Boats' as the water splashes onto the decks in many cases.
If you are not bothered about accuracy, fit rails on the side, it will transform their performance.
Cheers..........Ron.
