Outriggers and Enduro (7 cell)

By Ian Williams

In the last article I concentrated on the U.K. and European 12 cell class, this time it’s the turn of the 7 cell class. But before I go into details, I will do something I should perhaps have done in the last article, explain our European classes in a little more detail.

The NAVIGA classes for surface drive boats are split into 3 groups Mono/Hydro 1 (7 cells), Mono/Hydro 2 (12 cells) and Mono/Hydro 3 (20 cells). Any type of motor can be used, as can any hull, although these must have a semi-scale appearance!!! In the case of the Riggers this means simply using an aircraft style canopy, or sticking a driver somewhere on the hatch!!

Prior to the beginning of this season when we went over fully to the European classes, we in the U.K. used to run what amounted to cost restricted classes. This was an attempt to encourage people to race without having to spend a fortune. Basically what we did was to ban all ‘exotic’ motors such as Cobalts and Brushless. In the 12 cell classes this was easy, as all we did was make the Graupner 700 BB Turbo the only legal motor. The 7 cell class was not so easy. It was soon realised that direct drive 540 (05) motors were not suited to duration racing at any reasonable speed, so geared drives became the way to go. But it was accepted that for best performance we had to allow the use of full modified motors. So we ended up with a sort of restricted/open class in 7 cell.

Up until the start of this season all 7 cell monos and hydros ran geared drives. About 75% of which were Hughey, I’m pleased to say. This season however, we are starting to see some cobalts and brushless motors, but as you will see later in the article, the geared drives are more than competitive. (at least here in the U.K. they are, we will see just how good they are when we get to the World Championships).

As I think I explained in the last article, up until a couple of seasons ago, we ran shorter races, 3 minutes for the hydros and 4 minutes for the monos, as opposed to 4 and 5 now. Strangely enough, speed wise, the increase in run time had only a small effect on the 12 cell 700 powered boats. In fact, some boats were actually faster with a prop down size, allowing the motors to run more efficiently. The 7 cell boats were more effected and it has taken a couple of seasons of experimenting to get the boat speeds back up. The initial reaction of most people was to go for the run time, then work at getting the speed back. The first step seemed to be going for a milder motor, before prop and gearing considerations. I must admit that I have not run a 7 cell boat this year, preferring to concentrate on the 12 cell class. So I am going to detail some of the set ups used this season by the top U.K. hydro racer, Dave Harrold. This is the guy I usually end up chasing in 12 cell, but as he has been using my boats and Hughey hardware, who am I to complain?

When we ran 3 minute heats, we found that a 7 cell rigger could run a 12 double motor and drive a 1747 prop. Can’t remember the gear ratio used now though, but well over 2.0:1. The boats were pretty quick with this set up. When 4 minute heats came in, we ended up using P747 props and milder motors. At the end of last season and the beginning of this one, Dave was running a 15 double motor on 2.24:1 ratio and a P747 prop. The time was no problem, but speed was considerably down the previous season.. We decided that although big props are more efficient than small ones, the point of diminishing returns had been reached, so it had to be smaller props and more revs. The next step was the 15 double on 1.76:1 ratio with an X438. The speed was better, but still not up there. Next step, after considerable trial and error, was a 12 double motor on 2.16: ratio and the X438 prop. This was much better and Dave just got further away from the field. With other people now turning to Cobalts and Brushless, Dave obtained a Lehner Cobalt motor from me and found to his disgust that with an X430 direct drive, the boat only just made 4 minutes and was slightly slower than the gear drive. He went back to the geared boat, but still wanted more speed. The next step was something I didn’t think would work, an X435 on geared drive. The set up is 12 double on 1.62:1 and an X435. This is the fastest set up yet! We have two guys running German ‘Xcess‘ 7 cell riggers, these are very small and light and supposedly really fast in the hands of the Germans. One is running a Lehner Brushless, the other an Aveox. Both boats go well, but they still can’t catch Dave and his Hughey geared boat!

One last thing that Dave has tried is to make an extended front plate for the gearbox and to gear the Lehner motor. The set up is. 1.27:1 ratio. This means converting a 37 spur to use as a motor pinion, then running a 47 tooth spur on the output shaft. The prop is the X435. The speed is about the same as with the 12 double 05, but I suppose the cobalt motor is more robust so should last longer.

Well I hope you found something of interest in the article, and if it is alright with Donnie, next time I could talk about the design parameters of our hydros and the changes being made. Also perhaps, something of what happened at the worlds. There are 16 countries attending and over 400 boats, so it should be fun.

This Article was written by Ian Williams Exclusively for Rum Runner Racing. Use of this article is prohibited without written permission from Rum Runner Racing.


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