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Rudders .....
- Thread starter Olf Art
- Start date
Rudders are a big subject.
In my mind the BIG single rudder is best.
Dual dudders bring on the very problems you lilsted above.
Tow out in front means they come together slightly in the back is better cause it does two things for ya.
1. it focuses the air collum better
2. It keeps the rudder steering mechanism slightly loaded (mounting bearings and couplingas and cross bar) so they dont flutter when you are at neutral steering going strait ahead.
2 works pretty good, 3,4 n more works in some applications but each rudder ya add doubles the alignment headaches.
Olef Art, remember the old Ercoupes with the twin rudders? They would flutter themselves to death and fall off if they werent kept tensioned all the time. Same thing can happen with airboats.
I'm thinking that they sould be as far apart as they are tall but I dont have anything but visual imaging in my mind to back that up with. It may not be a good thing to have one shadow the other as you turn them to one side or the other.
This is just an opening line in THIS story. There may be nightmares hid in here too. Shivver n shudder ............. Here There Be Monsters !
Scotty
In my mind the BIG single rudder is best.
Dual dudders bring on the very problems you lilsted above.
Tow out in front means they come together slightly in the back is better cause it does two things for ya.
1. it focuses the air collum better
2. It keeps the rudder steering mechanism slightly loaded (mounting bearings and couplingas and cross bar) so they dont flutter when you are at neutral steering going strait ahead.
2 works pretty good, 3,4 n more works in some applications but each rudder ya add doubles the alignment headaches.
Olef Art, remember the old Ercoupes with the twin rudders? They would flutter themselves to death and fall off if they werent kept tensioned all the time. Same thing can happen with airboats.
I'm thinking that they sould be as far apart as they are tall but I dont have anything but visual imaging in my mind to back that up with. It may not be a good thing to have one shadow the other as you turn them to one side or the other.
This is just an opening line in THIS story. There may be nightmares hid in here too. Shivver n shudder ............. Here There Be Monsters !
Scotty
would look like you would be better off a little tight at the rear. seems slight pressure on the inside would be easyer to stabilize than on the
outside. But a slight toein, or toeout would be better than straight
ahead, you would get that flutter. kinda like tire alignment.
I guess with two rudders you can get the same airfoil surface
without hanging so far off the back of the boat.
With a single rudder would you have less of your airstream
turning the boat and more pushing straight back? like turning
with 2/3 of your air or with 1/2.
outside. But a slight toein, or toeout would be better than straight
ahead, you would get that flutter. kinda like tire alignment.
I guess with two rudders you can get the same airfoil surface
without hanging so far off the back of the boat.
With a single rudder would you have less of your airstream
turning the boat and more pushing straight back? like turning
with 2/3 of your air or with 1/2.
It seems it has to be narrow in the rear. If they are narrower in front then your eliminating air entry between them.
Those big ole single dudders arent thin and skinny like most doubles and triples are. They are fat and long grab a lot of air. If ya can find a picture of Cowboy's boat look at his rudder, its way longer front to back than any dual rudder setup.
The Taylor PB hull I had for my kid years ago would turn way inside my dual rudder boat. His boat looked exactly kike Cowboy's boat but the kids was shorter and had a 90 GPU on it. It had the same rudder.
I never owned a single rudder boat for myself but I have driven some and they dont feel much different than dual ruders to me.
I drove some big seismic drill boats with 4 rudders on them and those things are dogs. 3 engines and 4 rudders and something just doesnt come close to decent steering. Ya gotta really use differential thrust as well as rudder to turn them quickly. They call them work boats for a reason. Its pure work to run them.
Im thinking that the dual rudders should be at least as far apart as they are long front to back. That should eliminate any shadowing.
I have used 4' tall rudders almost exclusively so I cant say much about 5' and up. I have run 1 or 2 three foot flat rudder boats and they are well just sloppy. I dont know anybody that would like them.
Scotty
Those big ole single dudders arent thin and skinny like most doubles and triples are. They are fat and long grab a lot of air. If ya can find a picture of Cowboy's boat look at his rudder, its way longer front to back than any dual rudder setup.
The Taylor PB hull I had for my kid years ago would turn way inside my dual rudder boat. His boat looked exactly kike Cowboy's boat but the kids was shorter and had a 90 GPU on it. It had the same rudder.
I never owned a single rudder boat for myself but I have driven some and they dont feel much different than dual ruders to me.
I drove some big seismic drill boats with 4 rudders on them and those things are dogs. 3 engines and 4 rudders and something just doesnt come close to decent steering. Ya gotta really use differential thrust as well as rudder to turn them quickly. They call them work boats for a reason. Its pure work to run them.
Im thinking that the dual rudders should be at least as far apart as they are long front to back. That should eliminate any shadowing.
I have used 4' tall rudders almost exclusively so I cant say much about 5' and up. I have run 1 or 2 three foot flat rudder boats and they are well just sloppy. I dont know anybody that would like them.
Scotty
In my opinion, the best rudders are 1) airfoil designed, 2) 60 inches tall on a big boat like mine---lets you turn on a dime, 3) 24 inches apart and a half inch less in the rear. One single rudder is great if you dont cross levees----otherwise it gets torn off when you go down the other side because it sticks out too far....been there, done that. And the ones that have a big cutout in the back dont turn nearly as well. So I vote for two rudders, made by Dave Powell in Miami Fl---they are the best i have ever used. The ones made by the large manufacturers don't hold a candle to Dave Powell. Charles
Cant argue with 5' rudders, seems they would be up higher into the slipstream and give better authority. At least it makes sense to me.
I generally make my own airfoils and fill em with foam. maybe I'll try some 5' ones next time.
You may also be right about the leves. We are in South Brevard and only have a few leves and they arent that steep. I never drug my dual rudders and the kid never drug his single so that may be just because of where we run not one is better for us.
I knew this would be a good thread soon as I saw Olef Art run it up.
Scotty :lol:
I generally make my own airfoils and fill em with foam. maybe I'll try some 5' ones next time.
You may also be right about the leves. We are in South Brevard and only have a few leves and they arent that steep. I never drug my dual rudders and the kid never drug his single so that may be just because of where we run not one is better for us.
I knew this would be a good thread soon as I saw Olef Art run it up.
Scotty :lol:
jdotson
Well-known member
I run triple airfoil design rudders spaced about 12" apart (maybe a little more but a real b#*ch when trying to put the plugs on the inside for a person my size) and I have no complaints on the handling aspects. I have had people used to running two rudders complain about the sensitivity of the triple rudder setup. My setup is not the norm but that's pretty much all I've ever run. The rudder width is somewhere between 12 to 18 inches and is very responsive. I've only seen a couple of boats with a rudder setup similar to mine.
fatboy0054
Well-known member
KEN I KNOW THEY CANT BE ON THE MONEY ! GOT TO OFF SET THEM !I RAN MY CABLE TO THE RITE RUDDER IT SEEMS .THAT THE ONE CATCHING ALL THE BLAST ! DONT KNOW THE EXACT SEIENCE OF IT BUT SEEM TO WORK BETTER !
papee
Well-known member
I ran some tests on this when I was setting up my first mini. I used a digital fish scale to pull on the steering lever to see how much force it took to pull the lever with each setup at the same rpm.
My (steering easier a low speeds) test was that there was more force on the rudder, harder to pull, at low rpms with the dual rudder than the single. This means better turning when going slow. All of this applied when I put it in the water. My wife about locked me up when I was running these tests. She would just come out and shake her head.
My (steering easier a low speeds) test was that there was more force on the rudder, harder to pull, at low rpms with the dual rudder than the single. This means better turning when going slow. All of this applied when I put it in the water. My wife about locked me up when I was running these tests. She would just come out and shake her head.
Geneva0550
Well-known member
jdotson, I had been wondering how that triple setup would work on a smaller boat. The tour boats at lone cabbage are running triples. Are they more, or less prone to damage from being blown? I have been putting my plugs in from the back and haven't had any problems.
Des Moines Boater
Well-known member
jdotson, I always put my boat plugs in the outside of the boat also. I've never had a problem. I also have a hook by my seat to hook the plugs onto, so, I see them hanging there when I'm ready to load the boat in the water. It helps me remeber to put them in. Not that I've ever forgotten...
Geneva0550
Well-known member
I've never forgotten them either. I just figured as long as I kept moving I wouldn't need em'. LOL
Papee
The steering or rudder pressure has more than one feature to it.
If the rudders are not balanced there will always be heavy pressure. Balanced is a design feature that establishes WHERE the hige rod is located. If it is at the exact front of the rudder/s there will be huge pressure all the time. It is desirable to set the hinge rod back from the front of the rudder. The exact location is a trick to figure. There are a lot of "rules of thumb" out there but to do it right there needs to be enough rudder in FRONT of the hunge rod to reduce steering pressure but not take over the steering in any position of the rudders. The FAA bagan mandating balanced rudder pressures way back in aviation history.
Secondly the rudder/s need to be offset to one side to compensate for the clockwise/countercloskwise spin of the air at cruising RPM. Even in an airplane the rudders have more authority in one direction than the other when at slow speeds applying max throttle. My ole Cessna Skylane needed almost full left rudder at the begining of the take off roll but it rapidly centered the pressure as speed built up and you got airflow over the rudder that wasn't just all prop blast. If the hinge rod is set too far from the front of the rudder/s the prop blast will take over and slam them full turn in one direction or the other.
Rudders that run dead true at idle will require constant pressure in one direction or the other at cruise. I'm not a fan of centered rudder theory at idle. I prefur to set then so that the boat turns in a gradual circle and idles back to you should you be ejected from the boat for whatever or any weason. Just hang out and watch the boat make an idling circle and come back to you. Setting the center of the rudder system to one side or the other will help control this. It will also contribute to minimum pressure or no pressure when running at cruise.
Both the above are balancing acts, and they interact with eachother as well. In the old days when I set up rudders I just centered the set with the centerline of the boat and put the hinge rod i "think" maybe 4' back from the front of the rudder. They worked but needed the little trim tabs to trim pressures. Not the best, but thats all we knew to do back then.
Theres another feature thats concerned with rudder tilt but maybe we better leave that alone for a while.
Those that are pilots ever notice that the "V" tail Bonanza doesnt have both tailplanes at the same angle? Or that most airplanes dont have a prefectly vertical rudder?
This is why I knew this was going to be a good thread when Olf fired it up. There is a LOT here to understand and dig out. I sure don't understand it all but I do have a bit more than just a concept of whats going on.
Love it olf, thanks for the thread.
Scotty
The steering or rudder pressure has more than one feature to it.
If the rudders are not balanced there will always be heavy pressure. Balanced is a design feature that establishes WHERE the hige rod is located. If it is at the exact front of the rudder/s there will be huge pressure all the time. It is desirable to set the hinge rod back from the front of the rudder. The exact location is a trick to figure. There are a lot of "rules of thumb" out there but to do it right there needs to be enough rudder in FRONT of the hunge rod to reduce steering pressure but not take over the steering in any position of the rudders. The FAA bagan mandating balanced rudder pressures way back in aviation history.
Secondly the rudder/s need to be offset to one side to compensate for the clockwise/countercloskwise spin of the air at cruising RPM. Even in an airplane the rudders have more authority in one direction than the other when at slow speeds applying max throttle. My ole Cessna Skylane needed almost full left rudder at the begining of the take off roll but it rapidly centered the pressure as speed built up and you got airflow over the rudder that wasn't just all prop blast. If the hinge rod is set too far from the front of the rudder/s the prop blast will take over and slam them full turn in one direction or the other.
Rudders that run dead true at idle will require constant pressure in one direction or the other at cruise. I'm not a fan of centered rudder theory at idle. I prefur to set then so that the boat turns in a gradual circle and idles back to you should you be ejected from the boat for whatever or any weason. Just hang out and watch the boat make an idling circle and come back to you. Setting the center of the rudder system to one side or the other will help control this. It will also contribute to minimum pressure or no pressure when running at cruise.
Both the above are balancing acts, and they interact with eachother as well. In the old days when I set up rudders I just centered the set with the centerline of the boat and put the hinge rod i "think" maybe 4' back from the front of the rudder. They worked but needed the little trim tabs to trim pressures. Not the best, but thats all we knew to do back then.
Theres another feature thats concerned with rudder tilt but maybe we better leave that alone for a while.
Those that are pilots ever notice that the "V" tail Bonanza doesnt have both tailplanes at the same angle? Or that most airplanes dont have a prefectly vertical rudder?
This is why I knew this was going to be a good thread when Olf fired it up. There is a LOT here to understand and dig out. I sure don't understand it all but I do have a bit more than just a concept of whats going on.
Love it olf, thanks for the thread.
Scotty
papee
Well-known member
WOW, just wow, I am just in the middle of changing my rig over to dual rudders, I just came in from removing the old setup. I think I'll hang back an watch this thread before going any farther. I guess it's safe to make the mounts and then I'll wait. This place is amazing.