Single vs dual rudders

is there a huge preformance difference in useing dual rudders? im new to this and in my mind a single rudder is half the weight and moving parts.

Thanks!

A single rudder isn't really half the weight. I single rudder has to be bigger than the size of the duals. I choose duals becasue I didn't want the rudder sticking out as far as it would with a single. Dual rudders really aren't that much heavier, about 1/2 time heavier. Dual rudders turn better because there is more surface area. This helps a lot when turning at slow rpms.

Got ya. So dual rudders it is.

With the duals I can turn around in the length of the boat at idle. I took this video for a discussion we were having about pivot points. I don't use a setback on the pivot point because minis don't see the thrust that big boats do. he was saying that there is a performance advantage and I argued that there was no performance advantage just a mechanical advantage.

https://www.youtube.com/watch?v=PZQZbKgMf0Y

That's a heck of a turning radius. Is there any point to an air foil design on a mini? (40hp or less) also how slow does your boat run at idle?

Ok I may be wrong on this but I would say its just preference on a mini. I can't see how it would make much difference with the thrust we see. The air foils certainly look nicer but they are also heavier. I can't see how an airfoil design would help a boat like mine. You just can't turn any tighter than that video and its not going to do anything as far as holding in a turn. It's all up to the hull design if its going to stick when you turn it.

With that said, I will say again that they look much nicer. There are some pilots on here that could explain the concept.

Edit:
I have the river current affecting my speed at all times. I've never checked the speed but I would say a face paced walk. I often idle along.

I'm building a Bowfishing mini not a hot rod. Of course I want it to be as awesome as possible but it will be a work horse.

I personally like dual rudders. Not really all too complicated to hook them up. A simple 1/4" bar and a few swivel ends hooks them together. As papee said a single rudder will have to be bigger in order to deflect the air. I think that if you look behind the boat when your rudder(s) are turned that you should almost block out the prop so that if deflects enough air.

In the case of a mini airboat, I can't tell you how much of a difference airfoil rudders will make but I can tell you that they are more efficient than flat plate rudders. This is primarily because of two forces, lift and drag. An airplane's wing produces lift due to air moving smoothly over the wing's curved surface. As the air moves over the wing it's speed increases and it's relative pressure decreases (bernoulli's principle) causing the wing to produce lift. The more the wing's angle is increased, the more lift is produced. As you tip the wing from horizontal to vertical the lift remains perpendicular to it so that when the wing is vertical (as is a rudder) the lift (or pull if you wish to think of it that way) is sideways which causes the boat to turn. Of course you are also deflecting air from the propeller which helps turn the boat (Newton's theory). With a flat plate rudder the airflow cannot make the change in direction as easily because it it not following a smooth curved airfoil surface but is forced to make an abrupt turn at the leading edge of the flat plate. As the angle of the rudder is increased, the airflow can no longer make the turn and will begin to circle (burble) behind the leading edge. This radically increases drag and will act as a force to slow the boat and will impede the boat's ability to turn if the rudder is deflected too far.

Sorry for the long explanation but this is why I decided to fabricate airfoil rudders ... as far as weight, mine are very light because I hot-wired foam cores instead of making aluminum ribs.

I was hoping you would come along and explain the theory. I just can't talk myself into them though. My boat turns fine and at speed if I yank on the stick quick it will spin out. I'm not sure if this theory is not as noticeable at the thrust numbers we see on a mini. My thinking is that it would be more noticeable with faster speeds and more air moving over each design. If it weren't such a pain I'd put a set on my boat and see if there was any noticeable difference other than the mechanical advantage the setback of the pivot point creates over the flat type pivoting at the leading edge. I may make some when I get caught up.

I have two airfoils on my gar rig now and they do fine, on one of my boats I had flat rudders similar to pappe ,it worked fine. With these low hp boats I dont think it makes much difference , now on a big 600 hp boat you need the set back to help you turn the rudders and airfoil to stiffen it as much as to make a smooth air flow.
Ron

So far all my crafts (Hover and Airboat) had side to side sticks, I find that dual airfoil rudders with setback pivot point works
best for me, as the setback works like power steering and the airfoil needs less travel. I found the best position for a shrouded propeller is just outside the middle of the blade and just inside the middle for a open propeller.