Vosper MTB propulsion

Hello Adrian, I thought that maybe one of the technical body's may have answered you by now but here goes -most of the early Vosper boats especially those numbered in the 30+ series (inc 35) were constructed with the very heavy Hall scott 'Defender' supercharged Engines giving a max speed of around 29-30knts these being replaced by the Packard Units late in '42-43 giving an increase to 39-40 knts - but to answer you question - viewed from the Gearbox end the engines were right-handed ie 'clockwise' - the outer engines drove direct through theThrust Box's - so with both wing engines turning 'clockwise' this would be the rotation of the outer  Props. The center engine drove through a 'V' drive which would turn counter clockwise on the output shaft - so the center Prop would be anti-clockwise - with modelling how ever I found that this made my model difficult to maneovre (as was indeed the full size craft)- hope this helps

Regards

Hello again Adrian,

According to several articles that I have read- in full size craft, including Destroyers and the like, a more efficent use of Props and to keep reasonable steering capabilities etc would be to have the Wing props turning 'outwards' ie when viewed from the Stern - Port side turning 'anticlockwise' while Stbd turning 'clockwise'. I found that when modelling the Gay class with 3 props - the above arrangement made the model behave quite reasonable - in my model the centre prop could be 'wired up' for either a left hand or right hand - depending what propeller was available - I did try the model with the correct - full size arrangement- of all props turning anticlockwise - but I was a danger on the lake

Please keep us informed of your model

Regards

Hi Adrian and Teds

When I set up my Fairmile A I wanted to make it more manouverable so I fitted a mixer which controls the speed controllers according to rudder input, i.e. it slows down the inner motor in turns and with no throttle it reverses the inner motor on rudder input alone. I'd set the props as per most real boats, LH prop on port and RH prop on stbd. It proved impossible to get the mixer to accept this so I had to switch the props over and reverse polarity to the motors. So if you're using a mixer, use Ted's set-up with inboard turning props as outboard turning seems to confuse the electronics. I later noticed that the Robbe props are marked RH on the LH prop and vice-versa indicating that this is the norm in model boats, it does seem to give better turning ability without much affect to performance of the boat.

Rgds, Christian

p.s. see the pictures of Dave Abbott's MTB 74, even the proffessionals contra-rotate the outer props for the sake of manouverability over scale precision.