rudder size

[MichaelKeech]

Hi all. I am sincerley hoping that I can get some help with a problem I have. I bought a small (490mm long) outrigger model, and even though Ive buggered up making the sponsons, I have a more immediate problem. Just how big does a rudder for that size hull need to be? How big would be too much? I had bought a strudder unit off everyone's favourite auction site that takes a 4mm drive shaft, but the rudder on it looks positively massive - I think it's 115mm long. Could it be that I need one that is smaller?

 

[TimothyJones]

This is close to the one I have on my 20 rigger.

There are some measurements you can compare to yours.

http://www.mcssl.com/store/8c2175fc512f47f0836658c90e2ddc/speedmaster-hardware/mini-rudder-assy-spdr-005-h

Tim

 

[Mark Bullard]

Rule of thumb that I use is to have the rudder depth the same or close to the turn fin depth. All you have to do if it is to long is cut it off.

 

[MichaelKeech]

hm, I won't be able to cut it down a huge amount, as that would get in the way of it's built in water pickup. I did read somewhere that loosely speaking, a rudder should be about 15%of the length of the hull. That would make it 75mm deep in this case.

 

[TimothyJones]

Thats what That mini rudder blade size is.

3" blade, 4" to top of bracket.

It is also the same rudder on my PT Sport 40.

Tim

hm, I won't be able to cut it down a huge amount, as that would get in the way of it's built in water pickup. I did read somewhere that loosely speaking, a rudder should be about 15%of the length of the hull. That would make it 75mm deep in this case.

 

[MichaelKeech]

it will have to wait - I have bog all money atm, and I suspect the postage wouldn't be cheap either. Along with that I'd need an appropriate strut - I want to go with a 4mm flex shaft for ease of getting hold of propellers for it.

 

[Tom Foley]

At least 1-1/2 below the prop seems to work well , tune till it spins , buy another and don't trim so much off !

 

[TimothyJones]

Hi Michael,

Maybe you miss interpreted my intentions.Though I'm a salesman

I just wanted to show you.

Speed-master Is probably the most compared hardware that is out there.

Not a cheap hobby and I'm with you on trying to use or modify to your needs on what you have,

that is what I do now and then.

Keep the post active and hopefully you will get some more ideas and thoughts.

Tim

it will have to wait - I have bog all money atm, and I suspect the postage wouldn't be cheap either. Along with that I'd need an appropriate strut - I want to go with a 4mm flex shaft for ease of getting hold of propellers for it.

 

[MichaelKeech]

https://www.hobbyking.com/hobbyking/store/__20988__Wooden_Sponson_Race_Boat_Kit_495mm_.html that's the kit I bought, cheap and cheerful, or so I thought until I bolloxed up the sponsons

Im waiting for a 4mm flex shaft to turn up in the post now, and then I can start installing all the kit (if pos.). I did have a strudder unit that was smaller and took a 3.17mm (3/16ths?) shaft, but Id sent that to my dad thinking I didn't need it. Oh dumb me, after Id sent that and bought the one I have now, I found a nice bronze octura prop that would have gone on the end of it. Now Im thinking of getting that back, and getting a 3.17 shaft.

 

[MichaelKeech]

oops my bad, not 3/16ths, 1/8th.

 

[Mike Hughes]

Suggested Equipment
Propeller Shaft: 3.17mm
Rudder: 75mm
Propeller: 1.4x27
Motor: Watercooled 28mm 3700kv
ESC: Watercooled 40A+
Servo: 9g x 1
Battery: 3S 2200mAh lipoly
Radio system: 2CH

Right from the link you posted. I would try and go with what is suggested. Or something close.

 

[MichaelKeech]

I know what the page said about shaft size, it's just getting hold of the stuff that fits in this country is not easy as I found out when I looked about.

Also on a completely different topic entierly, and please forgive me for posting this, I am going on a sponsered bike ride this saturday raising money for a cancer charity www.justgiving.com/cycleboots - just thought I'd get the message out here.

 

[Mark Bullard]

The 3.17mm shaft is the same thing as a 1/8" shaft.