Difference between Speedmaster 20, 40, & 60 rudders.

[IRON-PAWW]

Hi all.

Feel like a nitwit - but can somebody explain the difference between the Speedmaster 20, 40 and 60 rudders?? I note it not to do with length of blade.... is it width maybe?? Or thickness??

Also - why would you choose a tapered edge over a straight edge? I note most hydro builds use a tapered blade while cats use the straight edge. What's the reason?

Hoping to increase my knowledge here... cheers!

[TRUCKPULL]

20 - 40 - and 60 are sizes that reefer to nitro boats

[rol243]

yes these sizes are different heights and widths.

[IRON-PAWW]

You mean heights and widths of the nitro boat hull itself? So a Speedmaster 60 rudder fits a nitro hull size 60? Meaning it is made stronger for a bigger hull? What makes a nitro hull fit a size category?

[rol243]

no a 20 is a 21 size glow motor and 40 is the 40 size and 60 is the 60 plus size . so lets say you have a 90 size glow engine and a suitable mono or hydro hull that suits this engine, you will use the 60 size rudder not the smaller 20 or 40 sizes. same as the 20 size rudder and hull combo, you wont use a 60 size rudder on a small hull.

[IRON-PAWW]

Ahhhh ok I've got you now. I never really touched glow motors so I guess that shows. So really - it's to do with power output and a strength grade of rudder that will deal with boats set up with larger motors. Chunkier rudders for bigger motors I guess I'm saying. Less chunky rudders for boats set up with smaller motor sizes...

[785boats]

Also - why would you choose a tapered edge over a straight edge? I note most hydro builds use a tapered blade while cats use the straight edge. What's the reason?

Well that's strange.
I always use straight rudders for hydros & riggers. For monos & cats I use mostly tapered blades. But some have straight ones. All depends on what is in the spares box at the time, sometimes.
I read somewhere years ago that a straight rudder creates less lift & bounce in the turns on a hydro.
I hope someone can answer the question with some degree of certainty. Maybe I've been doing it wrongly all this time.

[IRON-PAWW]

Heh. Well I'm the nitwit 785 remember :-). Really I'm just going by some build threads I read & my notably limited experience. Gsx380's folks seem to go the tapered speedmaster rudders. Then I admit I was looking at my Zelos 48 with its straight rudder. The taper creating lift I can understand. I suppose it depends what prop you use and what drive angles you run. It's part of the overall setup mix. But still wondered what made people go either way.