B1 & B1R WHAT'S THE DIFFERENCE?

On first glance both of these airscrew hydroplanes are very similar. They are both powered by 2.5cc engines, are both about the same weight, the engine mounting being the most obvious difference. One being a side mounted set up, the other being inverted. They are in fact quite different when it comes to construction, power, and most definitely cost.

Let us first take the boat at the bottom. This is the open class B1 hydro, built from quite high tech materials such as carbon fibre, Kevlar, alloys of one sort or another, with some lime and balsa. The whole thing is covered in epoxy. The power for this boat comes from a Russian made Cyclon TOP 2.5cc engine costing some £500. Competition fuel is 80%-20% methanol, castor oil mix. For the top boats in the class, speeds of 160-170 mph can be expected.

The top boat is quite a different kettle of fish. This is the B1R, the R standing for "RESTRICTED".

What are these restrictions?

The first thing to remember is that this class is mainly aimed at the beginner in the sport. Construction is kept simple by restricting the materials used to build the craft. 80% of all building material must be timber of one sort or another, also all parts must easily obtained commercially,  via local model shop etc. The engine has a maximum price of £70, which is reviewed annually and must not be modified. However the fuel used is allowed to contain up to 20% nitro methane. The current record for the class is a tad over 120 mph. So there you have it, two boats that on the surface look very much the same, but that are quite different.

Thanks to Jim Free for this description of the two airscrew classes

Commercial engine 'Novice'	15cc from castings 'B'	30cc from bar stock 'A'	Poppet valve flash steamer 'A/S'