Hi there Rannsachair
Now we are on a subject on which I CAN claim to be an expert (I sat on the government committee that brought in the CBT legislation, on behalf of the motorcycle training industry).
You can forget all of the scare stories about helmets causing head injuries. These were circulated by the anti helmet lobby in the early 1970's and have since proven to be absolute rubbish!
However, motorcycle helmets are designed to protect people riding MOTORCYCLES and the patricular circumstances in which they are liable to find themselves. They were NOT designed for the circumstances encountered in a RIB. Motorcycle helmets cost up to £500.00, but much of the cost of one of these expensive ones is in the finish (ie. a race replica - Carl Foggarty etc.).
Motorcycle helmets are designed to withstand impact and abrasion on a hard surface such as a tarmac road for several hundred yards.
I don't know if anyone actualy manufactures a helmet DESIGNED for RIBS, rather than an adapted motorcycle helmet. I would think that a rib helmet could be much lighter than a motorcycle helmet.
A 'full face' type helmet may be a good idea in a rib as it would protect your mouth and teeth from injury resulting from hitting your face against the instrument panel. The helmet should be light so that the ribsters head is not subject to extra stress and strain due to the constant movement of the boat. This movement may be much more simmilar to the forces a motor-x rider is subject to, rather than those of a normal motorcyclist on the road. The helmets used by motor-x riders are in fact lighter than regular road use helmets. I do have some contacts in this field, perhaps it is worth persuing. Of course it would all depend on the size of the market.
If no one has developed a specific RIB helmet, then it is time that they did.
Keith (at last something I actualy know about) Hart