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Hello there, I am building a 50" P1 semi scale mono. I would really like to run a twin rudder setup. The motor is a TP 5660 820 kv, swordfish 300 esc and 10s2p lipos, just for background. I am wondering how much drag/possible lift and other potential negative and hopefully some positive benefits of running this way. The rudders(6" offset)will be behind the end of prop dog by about an inchand spaced around 4" apart (really just a guess) I understand some of the forces of drag and lift this can present but don't have a real idea the levels of which it will affect handling and performance. I plan on eventually pushing the boat hard and seeing how fast the hull is and I realize small issues become issues at high speeds. I thought of swapping the aluminum water pickup rudders out for hardened stainless steel and moving water pickups to hull. I could run much thinner blades this way, perhaps with reduced width and depth running in water to offset. Shaping the bottoms of rudders to help as well. I really need things put in perspective, is this an issue that requires so much attention or would the increased loads be minimal? I would appreciate input to help me do this the best way possible. It's a big deep sided hull if it makes a difference. Thanks for any help you can give down to the small details. Time and effort required to make work is not important. What would be a good rudder depth below keel line to start with? I can imagine there will be countless hours tuning before pushing hard to get things right. I will enjoy all of it.Please ask for any additional info required. I really need to get a handle on this and welcome all criticism.
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My first thought is that WHEN you go for that speed run just pop one rudder off to decrease drag. One thing to look at is how the second rudder (high one in a corner) is going to act in the water. Is it in the water?
The other issue I see is, is one rudder pushing against the prop wash. You could 'cup' the prop to narrow the thrust cone and cut down on this. Prop wash can push the rudder back to straight.
Just tossing thoughts out there Jeff. -
Thanks for the input. I really wanted the steering to behave the same both right and left. I didn't like the compromise in steering on my other boats, twin rudders has its own compromises to I want to try and make it work very well. Should the rudder be behind the prop or in front of for better results?Comment
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There is something to the geometry of how far back from transom the rudders are but I haven't examined the subject yet. That Bling hull lifts and chops a bit in a corner and I am sure it is due to rudder. I know on a cat that the closer to the transom the sharper it turns.
I would think more beside the prop would keep things from reacting with each other.Comment
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I hadn't given much thought to where the outboard or raised side rudder would be in the turns, I have been dwelling on drag, Lift, spacing and depth below keel and minimizing these effects. Having found nothing to compare to makes it hard to prioritize. The fact that there isn't much out there with twin rudders and nothing going fast I have seen should be raising the alarm bells but I really want to do this. I may try a transom mockup and get a visual for how they will behave when when turning. It's a place to start, if the rudder would be exiting the water in a turn that will be a big issue. I am going to plod along with the idea and continue as if it will be successful. Hopefully more people get interested and will share there experience and knowledge behind why it isn't done more. Hopefully. fluid will be by to give me an earful though I may be on his ignore list:) some no nonsense viewpoints would be welcome
Thanks srilashComment
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