Originally Posted by dubrus
very interesting and thanks for uploading.
may i ask what is point of the tubes if they are not ever in water?
or what are the pros and cons in your view of having the tubes in the water?
Thanks for the question. It is one I have been asked many times, particularly in the early years of designing and building my designs. Before specialising in ribs I was a more 'traditional' designer/builder working with anything from sailing craft to work and fishing boats. Moving into ribs in the 80s it always struck me as odd that considering an inflatable was then being given a solid (usually grp) hull to enhance performance it seemed to me strange that others were at the same time taking away a couple of big advantages a solid hull offered, further reserves of bouyancy and stability. Some even flooded their hulls to gain stability when at rest by resting on the tubes.
Previous to ribs well designed boats had adequate stability and bouyancy by way of their hulls only and I reasoned this should remain the case with ribs. Hence my designs have always had hulls that were in themselves stable and bouyant without relying on any tubes at all if it came to it, say through mishap or damage to a tube. We proved this by launching an early Carson 6 metre and drove it around Liverpool docks BEFORE the tubes were fitted. This feature can be especially seen in my larger ribs as posted here.
I was often criticised for this approach in the early days and attempts were even made to bar Carsons from racing and some other events. Needless to say these attempts failed and nowadays it is a very common design feature.
Other advantages of keeping the tubes clear of the water are that they are saved from the worst effects of wave flotsam impact and weed groath accumulated when kept afloat. This is particularly important with ribs that like all Carsons over 5.5 metres can achieve speeds of at least 50 knots. I'm sure you'll appreciate the forces are considerable and even the strongest fabrics will eventually fail.
Soft cushioning fendering is another reason for having tubes and a big plus for boats that are used for boarding other craft. When inflatable conventional tubes are used they also save weight and with larger ribs may be deflated when towing on the road, particularly useful with bigger boats when their inflated beams exceed legal limits. Even our 750, 850, 900 and 950 models can all be legally towed when deflated. They also fit into containers for shipping and for the military be put inside transport aircraft.
The main down sides of tubes are 1 their cost and 2 their relative vulnerability compared to other types of craft's sides (grp, alloy, steel and wood, etc).