Size of radial drive wheel for tiller to wheel conversion

Jul 22, 2013
16
Islander 28 South Shore Yacht Club
I'm Assembling the parts for a tiller to wheel conversion on my islander 28. I've found everything except the radial drive wheel (per Edson the islander 28 uses a radial drive when rather than a quadrant). Per Edson the recommended drive wheel is their model 777-8 which is a 16" diameter wheel. Edson says this is for boats to 35'. I've found a good deal on a 777-6.5 which is a 13.5" wheel. Edson says its for boats to 30'. Can anyone tell me the effect of using a smaller diameter drive wheel? (The diameter for the rudder post is the same for both by the way)

Thanks

Bob
 
Oct 26, 2008
6,041
Catalina 320 Barnegat, NJ
Re: Size of radial drive wheel for tiller to wheel conversio

I want a larger diameter when I sit on the high side of the cockpit and reach back for the wheel. The larger diameter would be a more comfortable reach, and I think the feel would be lighter as well. As the diameter of the wheel increases, the force required to turn the wheel decreases, because of the longer lever arm.

I'm not sure that there would be a significant difference, but I would not go smaller. The diameter of my wheel is 26" and it seems small to me. I would prefer going up as high as 36" diameter. You are talking diameter, not radius? 13.5" diameter sounds about like the steering wheel of a car.

I'm thinking steering :doh:

Still, smaller wheel, less leverage... probably not good.
 

Ted

.
Jan 26, 2005
1,254
C&C 110 Bay Shore, Long Island, NY
Scott T-Bird - Lawyer Bob is not talking about the diameter of the steering wheel but the diameter of steering post radial drive or quadrant. I would generally go by the recommendations of Edson however if the larger radial drive or quadrant doesn't physically fit under the cockpit sole, a larger diameter steering wheel should be able to compensate for the power ratio difference. This is something you might want to discuss with the tech guys at Edson. They are very helpful.
 

Alec

.
Sep 23, 2005
79
Catalina 28mkII Bohemia River, MD
Re: Size of radial drive wheel for tiller to wheel conversio

Bob,

It's simply a matter of leverage. A smaller diameter drive wheel takes more effort to turn. This extra effort can be offset by a larger diameter steering wheel. Whatever size steering wheel you are considering might be upsized slightly to make up the difference in effort.

Clearance requirements for both the drive & steering wheels should also be a consideration.
 
Jul 22, 2013
16
Islander 28 South Shore Yacht Club
Thanks all! Appreciate the input. I was thinking it was a leverage thing. Thanks for confirming.
 
Nov 6, 2006
9,884
Hunter 34 Mandeville Louisiana
Re: Size of radial drive wheel for tiller to wheel conversio

Bob, the slightly smaller radial drive wheel will make the steering slightly "quicker" and require a little more effort for a given size helm wheel. guessing at a binnacle gear of 4", the smaller wheel would move about 15% faster, probably not an issue.. The only thing I could think of where it might make a difference would be in tuning the autopilot..
 
Sep 15, 2009
6,243
S2 9.2a Fairhope Al
Bob, the slightly smaller radial drive wheel will make the steering slightly "quicker" and require a little more effort for a given size helm wheel. guessing at a binnacle gear of 4", the smaller wheel would move about 15% faster, probably not an issue.. The only thing I could think of where it might make a difference would be in tuning the autopilot..
that just made me think ...if you are having trouble with auto pilot not being strong enough then maybe you could go to a larger quadrant and give the AP a little boost does that make sense?
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Re: Size of radial drive wheel for tiller to wheel conversio

The 6.5 is still a bit bigger than your 28 needs, so why worry?