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[ukmike]

Is there a formula for calculating the shaft position on the blade to balance the force on the rudder that helps reduce the load on the servos ?
The rudder blades are 32mm deep x 45mm length. The application is for a planing hull.

Mike.

[canabus]

Hi ukmike
Use one third the length, so in your case 15mm from the leading edge.
I usually use 4.5KG servos, only a few dollars more!!!
Canabus

[inertia]

Mike
Copied a photo of a rudder from a well-known supplier's website and scaled it to find the missing dimension. In the case of his Large Rudder it's 13.5mm. You rudder is 3/4 of that size so the shaft should be set back around 10mm from the top front corner of the blade i.e. where the leading edge and top edge would intersect if they weren't radius-ed. His rudders work fine on my planing boats.


DM

[ukmike]

Canabus / Inertia.

Thanks for the replies, both of which are very helpful indeed.

I have a couple of Digital ballraced metal geard servos which I was intending to use on the rudders, (one on each ), they are 2.6kg types.
I would like to take as much load off them whilst planing so would the 15mm help a little more in that respect ?

Re. the well known suppliers site, possibly German and quite exclusiv.
I notice that they say not available now, not that I would have contemplated spending nearly £50 each for them anyway !!

Mike.

[inertia]

Nope. It's Model Boat Bits (Steve Tranter) in good old Telford, and very much still available.
DM

[TomHugill]

I use the 15kg tower pro servos. I have them in my riva and my moonraker. The thrust from the jet drives i would imagine is more than that coming off the props. I would try and get the rudders scale and then match the servos to suit.