Where's The Rudder Go?

[PJ (on the road)]

Ok...I borrowed this question from the FE forum.

On a mono set up for heat racing, where do you locate the rudder fore and aft in relation to the prop?

How far from the transom?

How much offset from the shaft centerline?

 

[Hammerhead]

All my mono props are even with the rudder.

Does PJ mean Pajamas or Prop Jockey :

Hammer

 

[PJ (on the road)]

Hey Hammer -- Yes, it's Propjockey. My company thought I should spend this week in training. :

So, I'm borrowing 'puters from other "trainees", or using public access at the local library.

I'll be home tomorrow.

Anywho...when you say 'even with', you mean.......?

 

[Hammerhead]

I mean the back of the prop is on the same plane as the back of the rudder. I don't know if this is optimum or not, but I have always done it this way with no problems.

Hammer

 

[PJ (on the road)]

Anyone else want to chime in?

Are there pros/cons to having the rudder fore/aft of the prop?

 

[Ian Inverarity]

Okay, you asked for it!

It is my belief that there is no magical inter-relationship between the prop and rudder position, unless of course you get them close enough that they interfere with each other. That is, when viewed from behind, there should be a good seperation between the prop and rudder.

For monos a few years ago there was a belief that the leading edge of the rudder should be about level with the trailing edge of the prop. I think the distance from the transom (and turn fin) is more important than the relationship to the prop. Having the rudder further back from the transom increases it's leverage for turning. I have seen a mono that had the rudder mounted to the transom transformed when it was moved back. In recent years the props have moved further from the transom. In most cases that I have seen the rudder has stayed in about the same place. Some people have moved the rudder behind the prop in these cases but I dont know if they have seen any benefit.

I dont know if there are any disadvantages in performance in moving the rudder a long way behind the transom, but there is a structural problem (a very long and maybe flexible rudder bracket!).

Ian.

 

[Andrewg]

Generally I start with the prop and set it so I will get a 2-4 degree running attitude on the hull

the the leading edge of the rudder level with the leading edge of the rudder

I put the rudder mid way between chine and keel - to get it out of the way of the prop give me room and to make sure there is no prop rudder interaction I dont want

Andrew

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