This is Brutus and it will be the next fully new design coming off the production line and it is planned to be the Autumn project.

At the moment its a concept of a 4ft model speedboat based on the seaaxe design of hull.

Paul

Brutus has a knife bow and as Dave says it is designed to slice through the water rather than skim over them.

Ashley

Ah I see……But would you build it?

Hi Amy

At the moment its just an idea that is kicking around in my mind and it only exists as a few sketches but I have to admit that I am looking forward to building it.

Paul

Thanks Colin I will have a look

Bob I hadn't thought about Hobbies and will have a look, unfortunately it looks as though I will need the flex coupling as I am fighting for space in this one.

Paul

For those interested in why I need such an odd drive.

In designing the Brutus I have given myself a problem……I don't have sufficient space within the hull to get the twin 600s where I want to position them.

I do not like steeply angled propshafts so it is important that the shaft angle doesn't exceed 3deg

From a weight distribution point of view the first image shows the ideal location however the hull is simply to narrow at this point to accommodate the motors.

On a conventional hull the simple solution would be move the motors toward the stern to a location between F3 and F4 where the hull is wide enough to accommodate the motors.

The problem with the Brutus design is its bow shaped keel which, if the motors were moved backward they are also forced upward and so increases the shaft angle beyond 3deg.

A solution might be to turn the motors around so that the drive is pointing forward and position them over their respective shafts. The second image shows how this might be achieved, with the motors in this position the batteries would be placed in the adjacent bay.(F3/F4)

Paul

Hi Dave

Its just me I don't like steep shafts

The steep shafts change the propellers angle of attack which equals less efficiency with the resulting increase in prop size to compensate. To me its a compromise that doesn't need to be made especially when, with a little thought, the shaft angle can be kept shallow.

Paul

Dave

Whilst I agree that the Fairey boats represented a excellent benchmark in hydrodynamic design I do feel that the position of the engines and choice of power train were a compromise arrived at to suit the technology of the period.

If current technology were applied to the designs then I suspect that the layouts would be different, for example on the Huntress the motors might be in the stern and power transmitted via Z legs or jet drive. In this particular craft repositioning the engines to the stern and using a Z drive would not only correct the propellers angle of attack but move the centre of gravity toward the stern thus reducing or negating the need for trim tabs

We can argue the merits and failings of the Fairey designs backwards and forwards all day and I am quite looking forward to my learned friends rebuttal.

On a serious note you might have a valid point on power loss when employing belt drives and I will try to find some relevant data on the subject

Paul

Edited By Paul T on 03/12/2013 14:13:23

Andy

Yes, and when you think about it in terms of Newtons third law it becomes blindingly obvious, as the propshaft angle increases then more energy is required not only to propel the boat forward [because the effective area of the blades is reduced] but also to overcome the push of the propeller trying to lift the stern of the boat Ipso Facto for an efficient propulsion system the propeller has to be positioned as close to the horizontal as possible.

In short any propeller shaft that isn't truly horizontal is always the result of compromises having to be made between form and function.

Bob

A cross section?

Paul

Edited By Paul T on 03/12/2013 14:47:17