Rudder design

[Vance]

I would be gratefull for help in understanding the relationship of size of the rudder to the size of the vertical stabilizer. I am also wondering about the size of the balance compared to the size of the rudder. I know that normaly weight is used on the balance to reduce the chance of flutter. I was wondering if a hydraulic damper would do the same thing and if it wouldn't then why not?

[Gordon Gibson]

Vance

I reckon a hydraulic damper would probably do a good job of reducing chance of flutter. Trouble is it might also hinder necessary quick control inputs and it would be cumbersome. A bit of lead is a cheaper, more easily installed option that does not have such control considerations.

I always thought that the weight distribution of a rudder had to be the same forward of the hinge line as behind it but then there are more knowledgable guys in this forum will be able to define things better for you.

Thanks, Gordon Gibson, NZ.

[Vance]

Thank you Gordon, I keep hearing that weight is the enemy of flight and a pound and a half of lead seems a lot heavier than a 6 once dampener. Autogiros operate over a fairly narrow speed range but the flutter challange is still there. I was taught to not make sudden movements of the control sufaces and it is not hard to adjust the amount of dampening with a small hydarlic cylinder.

I have heard what I called the balance called the servo. I would be gratefull in understanding the size relationship, servo to rudder area. Thank you, vance

[mceagle]

Vance,
This is a very hard question to answer because there are so many different aerodynamic effects on gyros (even on the same make and model) that a straight answer is impossible. As far as rudder volume is concerned, one thing that we have in our favour is that we can go too large with extra weight being the only ill effect.
With a conventional fin and rudder the ratio between the size of the fin and the rudder should also be individualised for each different ship. This is not always possible with commercially available tail feather units. There should be only just enough fin volume so that the fin and the attached trailing rudder will keep the gyro facing into the relative airflow in the event of a rudder cable failure. Too much fin volume and may run out of rudder when doing a cross wind landing.
In most cases this is left up to the designer or manufacturer, and we all know that even they can stuff up big time. Failing that it is an intelligent and calculated guesstimate followed by fine tuning by trial and error.

I have found that counter balance, both aerodynamic and weight, are unnessary at the speeds that we operate.

Sorry to confuse the issue for you.

[Brian Jackson]

Originally Posted by mceagle

Vance,
This is a very hard question to answer because there are so many different aerodynamic effects on gyros (even on the same make and model) that a straight answer is impossible. As far as rudder volume is concerned, one thing that we have in our favour is that we can go too large with extra weight being the only ill effect.
With a conventional fin and rudder the ratio between the size of the fin and the rudder should also be individualised for each different ship. This is not always possible with commercially available tail feather units. There should be only just enough fin volume so that the fin and the attached trailing rudder will keep the gyro facing into the relative airflow in the event of a rudder cable failure. Too much fin volume and may run out of rudder when doing a cross wind landing.
In most cases this is left up to the designer or manufacturer, and we all know that even they can stuff up big time. Failing that it is an intelligent and calculated guesstimate followed by fine tuning by trial and error.

I have found that counter balance, both aerodynamic and weight, are unnessary at the speeds that we operate.

Sorry to confuse the issue for you.

Great post, Tim!
This is a subject near and dear to me, if anyone's been following the QB thread.

Vance,
I am clearly NOT an expert by any stretch of the imagination. But I can "safely speculate" (is that ambiguous or what!) that the V-fin/Rudder relationship is also partially governed by the tail configuration itself for structural integrity. For example, the Watson's tail for a GyroBee has different structural requirements than that of the StarBee tail.

In fact, I ran some numbers for you: The Watson's tail has a rudder area of 3.66 sq. ft. and a V-fin area of 1.78. That's a ratio of nearly 2:1. However the Watson's HS is mounted low on the V-fin at it's widest point, so the fin doesn't need to be any larger structurally.

Tall tails and all-flying tails, like those that appear on Dominators and Air Commands that have no V-fin, are generally balanced such that a portion of their area exists well forward of their axis of rotation to help balance the aerodynamic load and control pressures needed from the pedals... at least that's my understanding.

As Tim mentioned in his reply, it's up to the manufacturer/builder, as I'm not aware of any "hard and fast" rules that govern tail designs for Gyros. There is room for study in this area, so I'm hoping more designers & builders chime in on this thread.

Respectfully,
Brian Jackson

[Vance]

Thank you Tim, I am now confused on a higher level. I always enjoy your thoughtfull responses.

Thank you Brian, the numbers are interesting.

This area of the gyroplane is paticularly interesting to me because as your foward speed drops the rudder efectiveness drops, but the vertical stabilizer is just at responsive to a side gust. It seems like the hand off from aircraft to ground vehical is always challenging and the rapid reduction in air speed with an autogiro both exhaserbates it and minimises the conquences of managing it badly.

Thank you, Vance

[mceagle]

Correct Vance. A good designer will consider and allow for appropriate rudder control under all possible flight conditions, including engine out.
A gyro with a correctly set up and trimmed rudder is almost boring when taking off and landing as well as when flying. All too often there are gyros seen that are a handfull until they get into the air, and unfortunately you have to go through this stage before you are flying. IMHO this is often the cause of the common "beginners rollover". There is no excuse this day and age for a gyro that is a handfull on the ground.

[Vance]

Thank you Tim, Vance

[kiwidesign79]

Originally Posted by mceagle

Vance,
This is a very hard question to answer because there are so many different aerodynamic effects on gyros (even on the same make and model) that a straight answer is impossible. As far as rudder volume is concerned, one thing that we have in our favour is that we can go too large with extra weight being the only ill effect.
With a conventional fin and rudder the ratio between the size of the fin and the rudder should also be individualised for each different ship. This is not always possible with commercially available tail feather units. There should be only just enough fin volume so that the fin and the attached trailing rudder will keep the gyro facing into the relative airflow in the event of a rudder cable failure. Too much fin volume and may run out of rudder when doing a cross wind landing.
In most cases this is left up to the designer or manufacturer, and we all know that even they can stuff up big time. Failing that it is an intelligent and calculated guesstimate followed by fine tuning by trial and error.

I have found that counter balance, both aerodynamic and weight, are unnessary at the speeds that we operate.

Sorry to confuse the issue for you.

I realise this is a old thread & I'm sorry for dredging up the past but I'd like to learn a bit more about this subject before I get to far in to building my tail.

Tim, there must be a certain amount of calulation to get a gestimate for the fin size

[Vance]

Hello Jeremy,

Tim has not been on the forum in over a year so he may not see your question. I miss his thoughtful responses.

We have not heard from Brian since 2007.

I am confused on a higher level now and have a lot more experience flying.

I will offer my opinions in the hope that you too can be confused on a higher level. I am not an aeronautical engineer and these are only my opinions based on my experience and observations.

I have not yet flown a gyroplane that I felt had too much vertical stabilizer or rudder.

I have flown some where the rudder seemed insufficient to me.

I have flown gyroplanes that seemed to be confused about the direction of travel.

In my opinion increasing the distance of the aerodynamic center of the empennage from the center of gravity of the gyroplane increases the effectiveness of the empennage by more than the square of the increase.

In my opinion t¬he parts of the empennage are often quantified by volume which for a gyroplane may be defined as the area of the surface times the distance of the surface’s aerodynamic center to the aircraft center of gravity.

I feel the empennage on a pusher gyroplane may see speeds that could cause the rudder to flutter.

Flying the gyroplane pictured below I use a little rudder to hurry her into and out of turns and very little pressure on the pedals occasionally to keep the drift string centered. For me the primary use of the rudder is to align her with the direction of travel just before touchdown. I feel the effectiveness of an aerodynamic device goes up or down by the square of the change in air speed. I feel at very low landing speed in gusting conditions a large rudder has value.

I have flown gyroplanes where each power change requires a change in rudder pedal pressure. The gyroplanes with this tendency have all had a relatively short vertical stabilizer.

The SparrowHawks I have flown with a tall full flying tail have tended to wag their tail.

The Dominators I have flown with a full flying tall tail have not had a tendency to wag their tail.

Based on my experience I prefer a fixed vertical stabilizer with an articulated rudder.

In my opinion a cabin or pod with a lot of side area ahead of the center of gravity increases the desire for empennage volume. I feel there is value in having the gyroplane weathervane into the relative wind.

Thank you, Vance

[choppergabor]

Originally Posted by Vance

Hello Jeremy,

Tim has not been on the forum in over a year so he may not see your question. I miss his thoughtful responses.

We have not heard from Brian since 2007.

I am confused on a higher level now and have a lot more experience flying.

I will offer my opinions in the hope that you too can be confused on a higher level. I am not an aeronautical engineer and these are only my opinions based on my experience and observations.

I have not yet flown a gyroplane that I felt had too much vertical stabilizer or rudder.

I have flown some where the rudder seemed insufficient to me.

I have flown gyroplanes that seemed to be confused about the direction of travel.

In my opinion increasing the distance of the aerodynamic center of the empennage from the center of gravity of the gyroplane increases the effectiveness of the empennage by more than the square of the increase.

In my opinion t¬he parts of the empennage are often quantified by volume which for a gyroplane may be defined as the area of the surface times the distance of the surface’s aerodynamic center to the aircraft center of gravity.

I feel the empennage on a pusher gyroplane may see speeds that could cause the rudder to flutter.

Flying the gyroplane pictured below I use a little rudder to hurry her into and out of turns and very little pressure on the pedals occasionally to keep the drift string centered. For me the primary use of the rudder is to align her with the direction of travel just before touchdown. I feel the effectiveness of an aerodynamic device goes up or down by the square of the change in air speed. I feel at very low landing speed in gusting conditions a large rudder has value.

I have flown gyroplanes where each power change requires a change in rudder pedal pressure. The gyroplanes with this tendency have all had a relatively short vertical stabilizer.

The SparrowHawks I have flown with a tall full flying tail have tended to wag their tail.

The Dominators I have flown with a full flying tall tail have not had a tendency to wag their tail.

Based on my experience I prefer a fixed vertical stabilizer with an articulated rudder.

In my opinion a cabin or pod with a lot of side area ahead of the center of gravity increases the desire for empennage volume. I feel there is value in having the gyroplane weathervane into the relative wind.

Thank you, Vance

Excellent observations Vance.
Thank you for putting them into this post. I too am on the opinion that there is no such thing as "too much tail".
The effectiveness of the tail during slow flight or landing and even during take off phases could be reduced to such level that a smaller tail can be inadequate under certain circumstances.
Tail size and distance from the cg obviously has to be relative to the weight of the machine. It is rather a delicate process to figure out the right size and distance.
I wish there was a formula maybe an excel file you could enter the values and get your dimensions and distance from the cg just to make it easy for the designer to figure out all these very important information. All in all I don't think one can go wrong with sizing the tail as large as possible

[WHY]

"No such thing as to much rudder"-----that was the idea at Stinson for sure. I seem to remember reading somewhere that it was also the "Stinson sisters" that did most of the Stinson design work behind the scense

Tony

[RotoPlane]

CB's spreadsheet will give the needed tail volume….just add your gyro values into its cells.

I'm not sure how that volume is broken down into the vertical and horizontal areas.....

[Vance]

Hello Ed,

It appears to me that part of Mr. Beaty’s spread sheet is to determine the minimum size of the horizontal stabilizer as a percent of rotor volume rather than the vertical stabilizer and rudder.

The original query was about the size of the rudder compared to the size of the vertical stabilizer and did not involve the horizontal stabilizer.

The spread sheet seems somehow unrelated to the question.

I question the idea of using rotor volume to determine the size of the horizontal stabilizer.

I feel that a high thrust line gyroplane might well do better with a larger horizontal stabilizer that a gyroplane with nearer center line thrust.

Thank you, Vance

[WHY]

Hi Vance

I kind of think that formula was mainly for a tractor gyro application, not sure though

Tony