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Author Topic: Reducing control forces using spades  (Read 20865 times)

Offline Mark wood

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Reducing control forces using spades
« on: November 14, 2021, 10:46:21 PM »
I flew the first flight tests of of the SV11 with spades today. Then there was another event

Sorry about being long winded.



« Last Edit: November 15, 2021, 02:05:31 PM by Mark wood »
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Offline Mark wood

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Re: Reducing control forces using spades
« Reply #1 on: November 15, 2021, 08:34:47 PM »
These are something I have brought up from time to time when in conversation regarding the reduction of control forces on the aircraft particularly as result of adding flaps. It isn't often I try something which turns out as good as I hope or better. Unfortunately, I don't have an alternate pilot to fly the airplane in an A-B test to confirm my assessment. We have had a fairly large discussion on another thread which this discussion departed the intent of that thread. Because of that, I thought it would be good to separate this into a new topic.

It is and remains my opinion that an offset hinge is a superior method of reducing the hinge moment at the surface. The down side to this is that it is very difficult to make changes to the configuration. In the 4/4 arena the aerobatic airplanes use this offset hinge and often we see a small spade in use to supplement the surface. My opposition to using spades is more practical than technical. They stick out and can be easily damaged. On my test plane I put them on the top of the wing and they aren't purdy either. I spose a master artist could do something about that. That's not me.

There is really no super science aerodynamic calculations I performed to get to the solution I used. I did rely a lot on previous work on 4/4 airplanes. Here's the concept of a spade. The spade is a thin plate surface mounted ahead of the hinge line and has some vertical separation which in necessary to allow the spade to pivot with the surface it is attached to. The shape of the plate is somewhat important in that it's desired characteristic is that is produce a linear change in lift and drag with angle of attack. This is a characteristic of delta planform wings which produce their lift primarily from the vortex rolling up over the top or bottom of the wing. Other low aspect ratio plates can work as well but the delta configuration has been implemented with great success. So start any effort with that as a baseline.

To design the support struts I did some layouts of the wing and flap. This is a necessary as you need to prevent collision of the spade with the wing. What I found when I was doing my layout is that is would be very difficult to make this work correctly with a flap having 45 degrees deflection. In that case the arm would have to be very long which isn't necessarily bad but out of my experience zone. The moment generated by the spade is a combination of lift and drag from the spade times the combined arm.

Think of a spade as a small canard in front of the flap or other surface. Some 4/4 aerobatic planes have them on the rudder too. That canard provides a counter moment to the surface moment because it is on the opposite side of the hinge. I made three calculations in preparation of designing the spade and it's attachment to the flap. First is the mean aerodynamic chord MAC of the surface. I actually just did a layout on this as it is simple to do with CAD but a pencil and paper work okay too. The surface can be treated just like a wing and we can assume the center of pressure works through the 25% point measured from the leading edge of that chord, we say 25% LEMAC.

The reasoning behind finding the MAC is that is where I planned to place the spade. There are other places they can go on a surface for other reasons such as mass balance for flutter prevention. The other is that I know that in balance, 25% of the area will be in front of the 25% LEMAC location and if I size my spade less than 25% of the total area of the spade - flap combination I run a good chance of not having bad things happen. The caveat / assumption is the force generated by the spade being linear. So my other two calculations I made were the area of the flap and the sizes necessary to create the spade which I made less than 10% of the flap area. Easy peasy. No big rocket science involved.

The structure configuration was a bit tough to get and make right with the amount of area necessary and keep fairly compact. So I designed my spade in a manor that has worked well for me in the past. I have to say we did see one airplane where it didn't work as good as on mine. The front is truncated with 60 degree sweep angles. The sharp corner edge generates a strong vortex that stays in place quite well. There is a span / aspect ratio where this doesn't work but below 2:1 it seems to be consistent. The TE of the spade is located directly over the hinge line. It is there because of the geometry but with long struts it could go farther forward.

The strategy of spade testing is to start off small and make them bigger testing the flight envelope at each iteration. On my Laser as on the SV I did the first tests with only the strut, on the laser this was because some critical mass was collocated there. The first spade I made turned out a bit larger than I wanted because I printed out a drawing from autocad to pdf and a scale error occurred which I didn't catch until after I had cut the 1/16" plywood and drilled the holes. The day was getting late and I wanted to fly so I cut the spade down a bit and it turned out  to be between the 5% and 10% sizes I was planning to iterate. It's Kansas. Today was a Unicorn day where the winds were forecast to be less than 5 mph. I rarely fly into my own wake but this evening I did and I was making really good wakes.

My test flights today were a full length flight with just the struts in place. The holding plate for the spade is about 0.8" x 1" which surprisingly made a detectable difference. I flew the airplane through the pattern to check it's behavior and all was fine. The next flight I attached the spades and cut the timer down to 1 minute as I didn't want to fight a bucking bronko for a long time. I wasn't worried, just cautious. During the take off a line connector straightened out and startled me pulling out an inch or two off the ground from about 14". I did some gradually increasing aggressive pitch up, pitch down and duplets to check for any bad behaviors. There weren't any. And better, the control gradients were discernably lower.

I will often refer to stick force gradient which is the term used in flight test for the slope of the moment at the stick for the pilot. It is the measure of how much resistance the stick produces and we generally want to see a positively increasing force from neutral to full stick deflection.  Doesn't have to be a lot, it just shouldn't reverse it's direction and get lighter with deflection. The reduction in this was flight was obvious and I detected no gradient reversals.

After the first flight I increased the flight time to 4:30. I began with just some basic wing overs and then reverse and loops. And squares. Yeah I suck at pinning the trajectory of the squares and the lighter stick forces made the corner much easier and the exit just as sucky. With low control moments, control with lower line tension is much better. This is a place where this configuration definitely works. I did some interesting test maneuvers such as square vertical eights and hex loops and hex eights, I didn't try square overhead eights but they would work. Of course those would be turning in the zone where line tension usually isn't an issue.

After that flight I went back and flew the pattern. I still suck at all the parts I always suck at. But it was easier to suck at those parts.

Bottom line, I'm calling this one a successful first flight and don't see a roadblock to more development. I'll probably make another larger spade but I'm thinking if larger is necessary then adding another one further out would be a better approach than a large single spade. The rational for that is that the higher aspect ratio spade will at some point start behaving like a normal wing and stall around 20 degrees causing a nonlinear force curve. I'll also be putting the tail and fuse cams on to see if any badness happens.

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Offline Avaiojet

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Re: Reducing control forces using spades
« Reply #2 on: November 16, 2021, 09:38:13 AM »
What ever happened to balance/counter-balancing the control surface?

You EAA guys always, always thinking. A good thing actually.

CB
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Offline Howard Rush

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Re: Reducing control forces using spades
« Reply #3 on: November 16, 2021, 12:22:50 PM »
To clarify, are your spades only on the top?
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Online Trostle

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Re: Reducing control forces using spades
« Reply #4 on: November 16, 2021, 01:31:31 PM »
To clarify, are your spades only on the top?

And if only on the top, Why?

Keith

Offline Howard Rush

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Re: Reducing control forces using spades
« Reply #5 on: November 16, 2021, 02:30:08 PM »
What ever happened to balance/counter-balancing the control surface?

PJ, Keith, and I used balance tabs.  I think they were more effective near neutral than at higher flap deflections.  I switched to Igor's nonlinear flap mechanism, which increases leverage over hinge moment in addition to its other virtue. 
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Offline Mark wood

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Re: Reducing control forces using spades
« Reply #6 on: November 17, 2021, 05:22:55 PM »
And if only on the top, Why?

Keith

Yes, only on the top. Think of the spade as a canard of sorts. If the flap were in the wind all by itself trailing behind the hinge, it would take a moment equal to the lift force acting at the Center of pressure times the distance to the center of pressure from the hinge line to displace it. Now if we put a small surface out front of the hinge line, it would create a countering moment similarly. The unfortunate situation is that we can't exactly place the spade straight out in front of the hinge because the wing airfoil gets in the way so we displace the spade vertically in order to prevent collision with the airfoil contour. It's no different than the stabilizer vertical separation on the fuselage or a T tail. It would not necessarily be necessary to have them on the bottom as well although it could be if the drag component of the moment created asymmetry in either the positive or negative directions.  I did not notice that when flying so, if it is there is wasn't much. The only magic to the decision to place them on the top of the wing as opposed to the bottom is entirely due to how I transport the airplane in my POSburban which is full of junk which creates a damage risk.


I made a video.



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Offline Mark wood

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Re: Reducing control forces using spades
« Reply #7 on: November 18, 2021, 06:25:25 PM »
I made another video of a flight I did today. I had troubles getting all of the cameras working but this wing cam perspective is pretty interesting. I pretty much was just hacking at maneuvers as the sun was really bright and right where it was getting in to my eyes. Watch for several directly overhead square corners.
I have a  tail cam also I'll post soon.



Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
“Physics is like sex: sure, it may give some practical results, but that’s not why we do it.” – Richard P. Feynman

Online Brett Buck

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Re: Reducing control forces using spades
« Reply #8 on: November 18, 2021, 09:29:09 PM »
I made another video of a flight I did today. I had troubles getting all of the cameras working but this wing cam perspective is pretty interesting. I pretty much was just hacking at maneuvers as the sun was really bright and right where it was getting in to my eyes. Watch for several directly overhead square corners.
I have a  tail cam also I'll post soon.

   That's very interesting. Do you notice any asymmetry in the effect? Looks like it gets very close to the wing on "down" and is far away on "up".

   The other interesting thing is that you are using a lot more control deflection than I have usually seen trying to capture still pictures.

      Brett

p.s. an observation - if you put them near the tips of the flap, you could get a ballpark estimate of the torque they are applying by noting how much the flap twisted. I would not want them there for normal applications, obviously

Offline Mark wood

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Re: Reducing control forces using spades
« Reply #9 on: November 18, 2021, 11:15:27 PM »
   That's very interesting. Do you notice any asymmetry in the effect? Looks like it gets very close to the wing on "down" and is far away on "up".

   The other interesting thing is that you are using a lot more control deflection than I have usually seen trying to capture still pictures.

      Brett

p.s. an observation - if you put them near the tips of the flap, you could get a ballpark estimate of the torque they are applying by noting how much the flap twisted. I would not want them there for normal applications, obviously

 No asymmetry that I have noticed. If they were out towards the end of the flap result is opposite of what you think. When you drive the flap from the middle there is a twisting of the flap due to the lift over the span. With a balance tab like this the twisting is reduced. Simple physics. The control forces are much lower with the spades installed which gives the airplane t he ability to maneuver aggressively overhead. Obviously technology not invented from within isn't worthy of being used. Why are you like Brett?
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
“Physics is like sex: sure, it may give some practical results, but that’s not why we do it.” – Richard P. Feynman

Offline Howard Rush

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Re: Reducing control forces using spades
« Reply #10 on: November 18, 2021, 11:30:48 PM »
That’s why I have stiff flaps. I don’t have to keep track of signs.
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Offline Mark wood

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Re: Reducing control forces using spades
« Reply #11 on: November 18, 2021, 11:44:13 PM »
That’s why I have stiff flaps. I don’t have to keep track of signs.

LOL I seriously doubt your flaps are stiff. Heavy in flight maybe. Tail cam video is posted.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
“Physics is like sex: sure, it may give some practical results, but that’s not why we do it.” – Richard P. Feynman

Offline Mark wood

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Re: Reducing control forces using spades
« Reply #12 on: November 18, 2021, 11:45:47 PM »
Here is a video from the tail cam. My Gopro SD card died mid flight so there isn't any video from inside. My new DJI gimble camera arrived and it has much better zoom and tracking so we'll see if we get another flying day.


Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
“Physics is like sex: sure, it may give some practical results, but that’s not why we do it.” – Richard P. Feynman

Online Brett Buck

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Re: Reducing control forces using spades
« Reply #13 on: November 19, 2021, 01:20:08 AM »
No asymmetry that I have noticed. If they were out towards the end of the flap result is opposite of what you think. When you drive the flap from the middle there is a twisting of the flap due to the lift over the span. With a balance tab like this the twisting is reduced. Simple physics. The control forces are much lower with the spades installed which gives the airplane t he ability to maneuver aggressively overhead. Obviously technology not invented from within isn't worthy of being used. Why are you like Brett?


??? 

    Brett

Online Brett Buck

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Re: Reducing control forces using spades
« Reply #14 on: November 19, 2021, 01:24:40 AM »
That’s why I have stiff flaps. I don’t have to keep track of signs.

    I didn't  say which way.

     Brett

Offline Jim Svitko

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Re: Reducing control forces using spades
« Reply #15 on: November 19, 2021, 06:53:05 AM »
Regarding the tail cam video:

When the flap is deflected down, tufts on the flap and on the wing trailing edge move inboard.  Is this happening along the entire length of the surface or only in the region where the spade might have an influence and cause it?  Is this detrimental to performance?

I could not see very well if the tufts were moving sideways with the flap moving in the opposite direction.

Offline Mark wood

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Re: Reducing control forces using spades
« Reply #16 on: November 19, 2021, 07:15:01 AM »
Regarding the tail cam video:

When the flap is deflected down, tufts on the flap and on the wing trailing edge move inboard.  Is this happening along the entire length of the surface or only in the region where the spade might have an influence and cause it?  Is this detrimental to performance?

I could not see very well if the tufts were moving sideways with the flap moving in the opposite direction.

I have another thread showing just the plain wing and the inward flow along the TE is in both configurations with and without spades installed, A-B tests. It is very interesting and if you look at the reverse maneuvers you can detect the opposite happening and the flow is moving outboard. This is the result of the pressure field and vortex flow on the wing. A vortex is rolling up at the tip and at the wing root which you can see if you look carefully at tufts located in their proximity. This only occurs to this degree at high angles of attack and not elsewhere in the flight realm. It is very curious and at greater angles of attack the flow reverses showing the inflow of high pressure air to fill the turbulent bubble created from the unset of stall.

I was surprised by how little influence the spade actually seems to have with the airflow on the wing. The surface flow on the wing doesn't appear to be disturbed until the nose of the spade gets very close and you can see one of the tufts begin to pull inward behind the spade. During testing of full sized aircraft I have noticed, as have others, that when this condition occurs sometimes the spade wants to "dig in" and we call that snatching because the stick wants to pull out of your hand or stick in place. In that testing this phenomenon has not been global with some planes doing and others not with the same spade configuration or closely the same.
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Re: Reducing control forces using spades
« Reply #17 on: November 19, 2021, 08:43:25 AM »
LOL I seriously doubt your flaps are stiff. Heavy in flight maybe. Tail cam video is posted.

Interesting comment by someone who probably has not seen Howard's airplanes.  He has an almost unique method for flap construction with carbon tubes.  His flaps are probably the "stiffest" you will find on a control line stunt model.  (I would not doubt that Paul uses the same method.)

Keith

Offline Mark wood

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Re: Reducing control forces using spades
« Reply #18 on: November 19, 2021, 09:40:28 AM »
Interesting comment by someone who probably has not seen Howard's airplanes.  He has an almost unique method for flap construction with carbon tubes.  His flaps are probably the "stiffest" you will find on a control line stunt model.  (I would not doubt that Paul uses the same method.)

Keith

My interpretation was different referring to the the hinges. Torsionally stiff is a good thing but the flaps on the SV don't appear to twist much as seen in the videos.  The design I am working on will more than likely use D tube LE on the flaps similar to a modern FF stabilizer. It's fairly easy since I am already in possession of the necessary forms and materials.
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Offline Mark wood

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Re: Reducing control forces using spades
« Reply #19 on: November 19, 2021, 09:44:35 AM »
Here's an analogy of the impact of adding spades. Without spades the steering is like driving a truck. With spades the steering like driving a Camero. The capability to make the steering like an F1 is there. That is in the realm of hinge line offset.
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Offline Howard Rush

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Re: Reducing control forces using spades
« Reply #20 on: November 19, 2021, 03:18:27 PM »
Cool video.  It was interesting to see the flow separation at the wing root.  Maybe we should festoon that area with VGs.
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Online Ken Culbertson

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Re: Reducing control forces using spades
« Reply #21 on: November 19, 2021, 03:38:59 PM »
Here's an analogy of the impact of adding spades. Without spades the steering is like driving a truck. With spades the steering like driving a Camero. The capability to make the steering like an F1 is there. That is in the realm of hinge line offset.
Did you have trouble locking out of corners?  I measure, at least I think I measure the backpressure on the controls to nail my exits.  Sort of like letting the steering wheel slide as you come out of a turn.  Have to ask my subconscious about it.  Do you loose the feel?  I am assuming you don't loose tension.

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Offline Mark wood

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Re: Reducing control forces using spades
« Reply #22 on: November 19, 2021, 03:58:00 PM »
Cool video.  It was interesting to see the flow separation at the wing root.  Maybe we should festoon that area with VGs.

I'm considering making some and adding them to my tests, which I actually think translates to planning on but wasn't going to mention the intent until after I had some data in hand. I think it would be interesting and worth the effort. The intersection vortex is what fillets are used to counter but it's worth trying VGs just to see if they can make an impact. The trouble is, I feel, the vortex starts at the LE juncture and VGs would simply add energy to it. One way to find out.

I need to find a better small yarn. The 280 Denier thread didn't hold up to the abuse but early on you could see them swirl in the vortex on the spade which made me really happy to see. In the past I only had anecdotal confirmation of the flow pattern by the dust impingement witness marks on the 4/4 spades.

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Offline Mark wood

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Re: Reducing control forces using spades
« Reply #23 on: November 19, 2021, 04:23:21 PM »
Did you have trouble locking out of corners?  I measure, at least I think I measure the backpressure on the controls to nail my exits.  Sort of like letting the steering wheel slide as you come out of a turn.  Have to ask my subconscious about it.  Do you loose the feel?  I am assuming you don't loose tension.

Ken

I'm not sure what locking out the corners means. The control moments are lower which means it has power steering of sorts. Locking out sounds like what we generally call snatching as in sticking at the extreme or pulling. During testing I have or one of the folks I have worked with has experienced these effects. In the SV current configuration the control forces seem to be linear but about 1/3 - 1/2 the baseline. I plane on going larger spades for testing.

Make the spades large enough and the control forces will go away and eventually reverse. The interesting element to the flapped CL airplane is the elevator provides some moment also so if the flaps get to a zero point there will remain some centering from the elevator. If you have followed some of the efforts I have going in terms of bellcranks and such you'll find I have centering cranks in my arsenal for this reason. As Howard found with the geared tabs these treatments tend to reduce the breakout forces around neutral, those are how we feel neutral.

Leo Laundeslager, he was the guys who mostly started this whole spade thing, worked really hard to make a spade that took the control moment away but preserved the centering breakout forces. He never fully succeeded at that. What he had was a trailing surface hinged to the rear of a delta spade and was allowed to float around neutral and it caught in around 10 degrees deflection and started helping.  Photo attached but it is difficult to understand it's function.

My current effort on the spades was simply a demonstration of their functionality. They are a bolt on option. Once this beast was let out though, some limitation should be determined. For science. Since I'm here might as well explore some.
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Offline Mark wood

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Re: Reducing control forces using spades
« Reply #24 on: November 19, 2021, 04:36:22 PM »
I am assuming you don't loose tension.

Ken

Line tension above is "normal" as in not a lot. Without the spades, I could not make the square corner at the very top of the circle. It didn't show in the video very well but the corners directly overhead are as tight as the ones 8 feet off the ground. It's not likely that more spades will improve the corner tightness only the ability to have more control with lighter tension which is what the overhead demonstration is showing. Think diamond eight. Enter a reverse triangle loop with a 60 degree pull, 120 degree pull to inverted level at 45 degree azimuth, push 120 degrees to complementary 60 angle to the apex of the sphere, push down 120 degrees to the 45, push to level pull to the 60 and then to level.
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Online Ken Culbertson

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Re: Reducing control forces using spades
« Reply #25 on: November 19, 2021, 05:40:01 PM »
Line tension above is "normal" as in not a lot. Without the spades, I could not make the square corner at the very top of the circle. It didn't show in the video very well but the corners directly overhead are as tight as the ones 8 feet off the ground. It's not likely that more spades will improve the corner tightness only the ability to have more control with lighter tension which is what the overhead demonstration is showing. Think diamond eight. Enter a reverse triangle loop with a 60 degree pull, 120 degree pull to inverted level at 45 degree azimuth, push 120 degrees to complementary 60 angle to the apex of the sphere, push down 120 degrees to the 45, push to level pull to the 60 and then to level.
Please do that away from the crowd! LL~

My "Why Not" is the overhead cloverleaf.  I just think it would be cool from the outside.  A square clover would be cool too.

Is there any loss of "feel"?  I "finger fly" and the control pressure through the corners tells me when it has finished turning.  Less is not necessarily bad, inconsistent would be.

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Re: Reducing control forces using spades
« Reply #26 on: November 19, 2021, 10:02:05 PM »
Please do that away from the crowd! LL~

My "Why Not" is the overhead cloverleaf.  I just think it would be cool from the outside.  A square clover would be cool too.

Is there any loss of "feel"?  I "finger fly" and the control pressure through the corners tells me when it has finished turning.  Less is not necessarily bad, inconsistent would be.

Ken

The answer to that one is the question of the wind. Slack lines are slack lines and there is a point where the control is gone. In a calm wind it probably isn't a problem. The real problem is keeping track of the geometry and not getting lost. Part of the tricks I've done with the SV on spades are square bottom loop round top and round bottom square tops. Not really that spectacular as my non flapped airplane will fly them as well, just not as sharply. An overhead clover isn't any different than a overhead eight with more sides.
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Re: Reducing control forces using spades
« Reply #27 on: November 20, 2021, 11:19:24 AM »
T An overhead clover isn't any different than a overhead eight with more sides.
Try one without moving!

As to the Feel, I was more concerned with the lower altitude squares.  As I am coming out of a corner it is the feel through the handle that tells me when the plane is completing the corner and it is time to lock the flat.  I wouldn't want to lose that.

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Re: Reducing control forces using spades
« Reply #28 on: November 20, 2021, 12:47:58 PM »
Try one without moving!

As to the Feel, I was more concerned with the lower altitude squares.  As I am coming out of a corner it is the feel through the handle that tells me when the plane is completing the corner and it is time to lock the flat.  I wouldn't want to lose that.

Ken

One of the pluses over using offset hinges is the ability to tune the forces. If you were to incorporate spades, they can be made larger or smaller to decrease or increase the feel as desired. Another trim capability in other words.
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Re: Reducing control forces using spades
« Reply #29 on: November 28, 2021, 06:13:13 PM »
I made a few flights today with VGs added to the wings at the 8%-10% position. The video shows some improvement in the flow. See what you think.



 
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Re: Reducing control forces using spades
« Reply #30 on: November 28, 2021, 06:33:59 PM »
Leave all your taped yarn in place.

Remove that thing.

Do whatever you have to do to counter balance the flaps and you might as well do the elevator while your at it.

See what this accomplishes.
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Re: Reducing control forces using spades
« Reply #31 on: November 28, 2021, 09:12:33 PM »
Leave all your taped yarn in place.

Remove that thing.

Do whatever you have to do to counter balance the flaps and you might as well do the elevator while your at it.

See what this accomplishes.

To what thing is it you refer? The spades won't leave. The positive impact is too good. They may and probably will change size. I made new struts with a more durable material specifically so they can stay. Ultimately the next airplane will use offset hinges and may need the use of spades as well. There is a level of too little hinge moment leaving the control forces less than that of a combat plane.


 The yarns are a test to see where the transition happens and separation on the flaps occur. That answer is also determined. For that the yarns are likely finished doing what I set out to learn and will likely leave.
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Re: Reducing control forces using spades
« Reply #32 on: November 29, 2021, 06:32:15 AM »
"Thing" being your "spades"

Then just balance your control surfaces. That alone should make an improvement.
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Re: Reducing control forces using spades
« Reply #33 on: November 29, 2021, 07:59:21 AM »
"Thing" being your "spades"

Then just balance your control surfaces. That alone should make an improvement.

    Why don't you explain why??
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Re: Reducing control forces using spades
« Reply #34 on: November 29, 2021, 11:22:33 AM »
"Thing" being your "spades"

Then just balance your control surfaces. That alone should make an improvement.

As in add weight in front of the hinge line? Care to elaborate how that might be possible on a plane hinge surface hinged at it's very forward edge?
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Re: Reducing control forces using spades
« Reply #35 on: November 29, 2021, 11:47:15 AM »
As in add weight in front of the hinge line? Care to elaborate how that might be possible on a plane hinge surface hinged at it's very forward edge?

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Re: Reducing control forces using spades
« Reply #36 on: November 29, 2021, 12:04:37 PM »
Gold-leading-edge spades

Or depleated uranium maybe.
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Re: Reducing control forces using spades
« Reply #37 on: November 29, 2021, 12:46:16 PM »
As in add weight in front of the hinge line? Care to elaborate how that might be possible on a plane hinge surface hinged at it's very forward edge?

Yes, to balance a control surface, the proper weight must be added forward of the hinge line AND, to do this correctly the control surface should be removed and "jig" set up so there's little resistance with all the hinges.

An "arm" must be added with weight possibly at the tip but doesn't have to be. The farther the arm is from the hinge line, the less weight is needed for balance.

Google "balanced control surface on an aircraft."

Simple science and aerodynamics 101.



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Re: Reducing control forces using spades
« Reply #38 on: November 29, 2021, 01:47:06 PM »
Simple science and aerodynamics 101.

Not simple for me.  It’s aerodynamics 3-something. What will that get us?  Few control line models have a flutter problem. I have wondered whether balancing our control systems could help us fly more accurately. I suspect it’s not worth the weight, but I haven’t put any effort into finding out. I’d be interested in seeing some ciphering.

Edited to reduce assholicity.
« Last Edit: November 29, 2021, 03:06:50 PM by Howard Rush »
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Re: Reducing control forces using spades
« Reply #39 on: November 29, 2021, 02:59:10 PM »
Yes, to balance a control surface, the proper weight must be added forward of the hinge line AND, to do this correctly the control surface should be removed and "jig" set up so there's little resistance with all the hinges.

An "arm" must be added with weight possibly at the tip but doesn't have to be. The farther the arm is from the hinge line, the less weight is needed for balance.

Google "balanced control surface on an aircraft."

Simple science and aerodynamics 101.

As Howard says, there is more to it than simple mass balance. The spades actually do add mass in front of the hinge in fact on some of the 4/4 airplanes we also add lead to the retaining plate for the spade itself. On my laser there was 1 1/2 pounds of lead along with the spade 2 1/4 pounds total. That was there to counter a wing flutter issue the Lasers have and Dr Tolve sorted out.  Kermit Weeks recently posted a video of Tolve conducting a ground vibration test of the Gee Bee R1 of his in order to determine the flutter characteristics of he R1. He pretty much determined the cause of the original airplanes' demise. 

There is some hinge moment created by the mass of the surface that much is true but it is not that much with these very light surfaces. Flutter is like a spring mass system where the spring comes from the aerodynamic force generated by the displacement of the surface. Of course in the case of being around the hinge it becomes the rotational version and it's torque versus moment of inertia. When the center of mass is at the hinge, the opportunity for flutter is eliminated. This same spring force which is caused by the surface displacement is what the spades offset. End of the day, mass balancing will not create the same hinge moment reduction as do the spades.

If you wish, you could compare the spade with a horn balance which is most often located at the end of the wing.  Another way is to offset the hinge further back in to the surface which will be the approach of the new airplane. Some airplanes like the Cessna Citations use both a balance horn and offset hinge. If you are interested, I can provide tons of good literature on the subject. Bottom line is mass balancing is for flutter prevention while balance horns and spades are for moment reduction aka control stick force reduction.

I have not measured the force at the handle. Perhaps a creative EE would step in and help but I can provide a qualitative analysis. Unfortunately I have not been able to convince any of my local other pilots to fly the A-B test on my airplane despite my most insistent efforts. So my estimate is that the no spade installation is at something like 5 pounds differential up to down. I have no clue what it really is, maybe it's 2 but for discussion use I'll say 5 pounds. Adding just the strut with the retaining plate which has about 1 square inch surface area changes that a bit noticeably to about 4 - 4 1/4 pounds differential. Adding the spades brings that down to around 2 - 2.5 pounds differential. I am planning on taking the total area of the plates up to 20 (10 each) square inches and hope that they remain linear. If not the impact is that I go back to the initial or intermediate state. Here's one point of caution I have to remind myself of is that elevator is a contributor also and I will not shoot for the zero moment point and solely the plateau zone where the hinge moment of the flap nears zero.

I realize that your objection has nothing to do with the flying or handling qualities and everything to do with the aesthetics.  Personally, I don't care what it looks like as long as it works well.. I am a performance oriented individual and I'm not a lemming. I am both scientist and engineer, therefore I am always in a research and development mode. I make these inputs, even if they aren't received well as I think they are interesting. From the PMs I get, I won't stop. The airplane these are flying on will continue to have the spades installed for it's foreseeable future.  They are that good of a change and I'm going tell you I have tried dozens of the you gotta try this'... Most are "meh". There's  simple way to prove me wrong, put some on your airplane and try it. I'll even help you.
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Re: Reducing control forces using spades
« Reply #40 on: November 29, 2021, 03:05:38 PM »
Dave de-tailed elevators with counter balances in his de-tails article for stunt news. They don’t work as you think they would
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Re: Reducing control forces using spades
« Reply #41 on: November 29, 2021, 03:08:45 PM »
Not simple for me.  It’s aerodynamics 3-something. What will that get us?  Few control line models have a flutter problem. I have wondered whether balancing our control systems could help us fly more accurately. I suspect it’s not worth the weight, but I haven’t put any effort into finding out. I’d be interested in seeing some ciphering, but not some imposter waving his arms, balanced or not.

One of you guys, maybe even a few, claim you have single wired control surfaces which are removable. Unlikely, but it's been repeated many times.

So, how easy is this. Remove the control surfaces and balance the things. If the model flies without improvement continue to troll, bully and treat me like I don't know anything, you will anyway.  LL~

If this makes an improvement, no one will hear about it because it probably won't be shared.

Read about balanced control surfaces. I just looked, there's plenty of info on line.



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Re: Reducing control forces using spades
« Reply #42 on: November 29, 2021, 03:13:55 PM »
One of you guys, maybe even a few, claim you have single wired control surfaces which are removable. Unlikely, but it's been repeated many times.

So, how easy is this. Remove the control surfaces and balance the things. If the model flies without improvement continue to troll, bully and treat me like I don't know anything, you will anyway.  LL~

If this makes an improvement, no one will hear about it because it probably won't be shared.

Read about balanced control surfaces. I just looked, there's plenty of info on line.

Here is Dave’s article with a removable tail, balanced and done scientifically

https://stunthanger.com/smf/open-forum/copy-of-the-david-fitzgerald-article-'de-tails'-from-the-marapr-98-stunt-news/msg511851/#msg511851

I don’t have much to contribute to the discussion other than I think aerodynamic devices look cool on airplanes, kinda like the modern F1 cars, and have enough of a basic knowledge of aerodynamics to understand how the spades work and it seems like they are. The talks have been fascinating!
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Re: Reducing control forces using spades
« Reply #43 on: November 29, 2021, 03:27:25 PM »
One of you guys, maybe even a few, claim you have single wired control surfaces which are removable. Unlikely, but it's been repeated many times.

So, how easy is this. Remove the control surfaces and balance the things. If the model flies without improvement continue to troll, bully and treat me like I don't know anything, you will anyway.  LL~

If this makes an improvement, no one will hear about it because it probably won't be shared.

Read about balanced control surfaces. I just looked, there's plenty of info on line.

It's clear that you haven't understood what spades do. Nothing you read about mass balancing control surfaces tell you that mass balancing reduces the stick force gradient. Mass balancing is all about flutter reduction. On the models the surface is very light and the need for mass balance isn't there generally. There are two moments on the hinge of a surface. Mass and aerodynamic. One is what the mass balance is about. The other, aerodynamic hinge moment can interact with the mass balance and cause flutter. We are not talking about that. My hinges are pinned with a single pin and pulling that pin would allow the surface to be put on a balance fixture as are 99.5% of the model airplanes. The trouble is that the surface will hang vertically form the hinge as the hinge is at the furthest forward edge of the surface. There is physically no place in front of the hinge to add weight without making some sort of extension like the very "thing" you suggested removing. Look at the horizontal of the P38 Lightening. Those little bomb looking things on the struts projecting out like the "thing", those are weights. They are there to prevent flutter and were a afterthought much like why we use spades except with spade we are after the other hinge moment reduction, the aerodynamic one.


Photo added
« Last Edit: November 29, 2021, 04:40:17 PM by Mark wood »
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Re: Reducing control forces using spades
« Reply #44 on: November 29, 2021, 04:32:50 PM »
One of you guys, maybe even a few, claim you have single wired control surfaces which are removable. Unlikely, but it's been repeated many times.

So, how easy is this. Remove the control surfaces and balance the things. If the model flies without improvement continue to troll, bully and treat me like I don't know anything, you will anyway.  LL~

If this makes an improvement, no one will hear about it because it probably won't be shared.

Read about balanced control surfaces. I just looked, there's plenty of info on line.

Sorry, I just couldn't let it be. So I took one of my non single wire hinged surfaces and hung it by the single hinge pin wires to see how much lead it would take on the wing side of the hinge to balance it. And I compared it with the spade strut I took off of the SV in order to replace it with a more durable material strut for a permanent installation. The result is that it took  730 grains ( 47.3 gr) just in front of the hinge line to balance. I have no clue where this will go, maybe cut a big hole in the TE. I could save some weight and install some of those gaudy looking spade struts for 103 grains (6.7 gr)  and get the aero benefit too.


Note the spade comes fairly close to balancing the flap. Granted this one is a small flap, however....
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Re: Reducing control forces using spades
« Reply #45 on: November 29, 2021, 05:03:43 PM »
Just for the record, in case it comes to a debate, here is an aileron being mass balanced with a spade in 2013 for my 4/4 scale Laser 200. In this state the aileron is in the no surface flutter state. However, due to the torsional properties of the wing, the horn on the end has to have more mass added to stop the aileron from responding to a torsional bending mode the wing might have. That's what I am in the middle of doing in this photo, making the lead weight.
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Re: Reducing control forces using spades
« Reply #46 on: November 29, 2021, 06:28:07 PM »
One of you guys, maybe even a few, claim you have single wired control surfaces which are removable. Unlikely, but it's been repeated many times.

So, how easy is this. Remove the control surfaces and balance the things. If the model flies without improvement continue to troll, bully and treat me like I don't know anything, you will anyway.  LL~

If this makes an improvement, no one will hear about it because it probably won't be shared.

Read about balanced control surfaces. I just looked, there's plenty of info on line.

   I just have to ask, what makes you think that this hasn't been thought of, tried, and rejected by people who actually fly their models in competition? I think you should quit while you are behind, sit back, open up a can of STFU and follow along quietly. Don't ruin it for the rest of us, PLEASE??!!

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Re: Reducing control forces using spades
« Reply #47 on: November 29, 2021, 08:05:19 PM »
One of you guys, maybe even a few, claim you have single wired control surfaces which are removable. Unlikely, but it's been repeated many times.

   So now you are calling the rest of us liars? When anyone can easily look and check on it? Many people on this forum (you know, the ones that actually fly model airplanes with other people) have seen the system as implemented and seen flaps and/or elevators removed. It was on published plans for 30 years ago.

Quote
So, how easy is this. Remove the control surfaces and balance the things. If the model flies without improvement continue to troll, bully and treat me like I don't know anything, you will anyway.  LL~

   No one has ever trolled or bullied you, because, to be honest, the ideal situation is that you go away completely. Since you don't know the meaning, "trolling" means to post in such a way that people are goaded into responding. It is what *you* do incessantly. The rest of us would be very happy if you never posted again, which is about as far away from trolling as could be imagined.

  You *don't* know anything and you have never accomplished even the first steps in this event. The rankest beginner who just managed to fly their CG Wizard for a full tank is infinitely more accomplished than you are and more worthy of our time.

Quote
If this makes an improvement, no one will hear about it because it probably won't be shared.

   Many people, almost all of them in fact, have told everyone time and time again exactly why they did something, exactly how they think it works, and how you can do it yourself. This includes multiple national champions and world champions. There are no secrets.

       You, naturally, ignore it all because you can't admit your own astounding ignorance, and the fact that you are so busy gassing on about your own nonsense that you don't hear it.

    Brett



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Re: Reducing control forces using spades
« Reply #48 on: November 29, 2021, 08:43:59 PM »
Well, this one went south...  8)
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Re: Reducing control forces using spades
« Reply #49 on: November 29, 2021, 09:17:47 PM »
Well, this one went south...  8)
Lasted longer than most.  It was getting somewhere too.

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Re: Reducing control forces using spades
« Reply #50 on: November 29, 2021, 09:28:50 PM »
Lasted longer than most.  It was getting somewhere too.

Ken

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Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
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Offline BillLee

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Re: Reducing control forces using spades
« Reply #51 on: November 30, 2021, 07:54:23 AM »
Maybe to get back on track a little .....

Mark, from my perspective, a "spade" as you are describing is an aerodynamic feature intended to balance the torque created by the flaps.

How does this differ from a balanced surface where the balance is achieved by having a portion of the surface in front of the hinge line? Note: not a mass balance, but an aerodynamic balance.

Example in attachment, taken from Wikipedia:
https://en.m.wikipedia.org/wiki/Balanced_rudder
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Offline Mark wood

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Re: Reducing control forces using spades
« Reply #52 on: November 30, 2021, 08:36:25 AM »
Maybe to get back on track a little .....

Mark, from my perspective, a "spade" as you are describing is an aerodynamic feature intended to balance the torque created by the flaps.

How does this differ from a balanced surface where the balance is achieved by having a portion of the surface in front of the hinge line? Note: not a mass balance, but an aerodynamic balance.

Example in attachment, taken from Wikipedia:
https://en.m.wikipedia.org/wiki/Balanced_rudder

Great move Bill, thanks. There is actually little difference in terms of the moment generation between a balance horn and a spade. I think there is a little in this discussion which actually says specifically that, a spade is more or less an aerodynamic balance tab or horn. There are a bunch of NACA technical briefs on the horns and are a lot of the source material we have used in the development of the spades during efforts I have been involved with. Basically a spade is a bit of an afterthought in sorts. The history can be traced to one guy, Leo Laudenslager who was an American legend and world champion the  full size aerobatics arena. He began adding spades in the late 70's or early 80's.

The Stephens Akro he was flying had long ailerons, see my photo earlier here, which have a lot of torque necessary to drive. They are driven by a steel tube which winds up quite a bit and limits the max deflection and therefore the roll rate of the airplane not to mention the stick force which is quite high without the spades. During my testing of the Laser, I dove to 240 MPH and did full deflection tests. On the ground my non "fixed" aileron would deflect 27 degrees and during the high speed test the twisting of the torque tube made it so the aileron was only deflected 12-15 degrees. That and the stick force was very high which I was barely able to physically push hard enough to get to the stick to the stop. The roll rate in this test was actually slower than the roll rate at 150 MPH.

The photo I posted of the Laser aileron is the "fix", actually I did two I inserted a heavy wall tube in the existing tube and I added the spade. The result when I went back to the dive test was an improvement in the deflection where I was getting more like 20 degrees deflection and I was physically able to push the stick to the stop. During normal aerobatics the laser flies between 60 and 180 MPH. It is desirable to have one handed capability of moving the stick which the spades achieved. Without not so much. This knowledge is what I bring in to this discussion and this is a bit of history where it comes from.

So Leo had the idea of mounting a strut and putting a flying surface on in front of the hinge line, in essence a balance horn. Why he did it this way rather than the end of the wing, I don't know. Suffice it to say it worked. The Pitts and other airplanes were doing this a little different at the time and they were using what is know as a Frise aileron which has its hinge offset and the nose is allowed to dip down in to the airstream. This is beneficial for an airplane that always flies upright but not so much for an airplane which is intended to operate inverted. The current methodology is is an offset of the hinge in to the aileron (flap) to about 25% of the chord. Some are more and some are less. This is also common on jets which has high control forces as well.

Honestly, I wasn't planning on messing with spades at all on the models as my direction is towards the more recent approach but I decided it was worth giving it a try. I'm glad I did as it really worked out well. Well enough that I abandoned a wing design I had  that was going to use a 22% flap hinged at the 20% flap chord line. Actually that design was a constant hinge offset with a tapered surface which will also be the case on the new wing design. I was actually preparing the laser templates to cut parts when I stopped. So the new design will use a 30% average chord flap and I haven't yet decided how I am going to do the hinge but no less than 20% flap chord. That decision makes an impact on the airfoil selection so I have spent some time doing some analysis on airfoils specific to this geometry. I'm not sure where that is headed.

Even with the offset hinges many of the full size airplanes use a small spade to adjust the control force feel. The size of the spade in these cases is actually very small and is mostly a trim device and helpful at reducing the weight required to balance the surface. So, the spade is kind of like the application of Gurney flaps. They work really well at making desired changes without having to resort to complete redesign.
 
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
“Physics is like sex: sure, it may give some practical results, but that’s not why we do it.” – Richard P. Feynman

Online Dan McEntee

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Re: Reducing control forces using spades
« Reply #53 on: November 30, 2021, 08:54:15 AM »
Maybe to get back on track a little .....

Mark, from my perspective, a "spade" as you are describing is an aerodynamic feature intended to balance the torque created by the flaps.

How does this differ from a balanced surface where the balance is achieved by having a portion of the surface in front of the hinge line? Note: not a mass balance, but an aerodynamic balance.

Example in attachment, taken from Wikipedia:
https://en.m.wikipedia.org/wiki/Balanced_rudder

   I have been trying to get around to asking this myself. There have been many designs over the years that have these types of "balanced " control surfaces, with the SIG Chipmunk being one of them. Back when I built one during my intermediate class days, it was suggested that they be eliminated and just go with a straight hinge line. I don't know if I have the "feel" that some of you have for subtle control differences. I think I would need several models all lined up in a row with different set ups and fly them ion sequence and hope I could tell the difference!!

   On some models, we experience a difference in how a model turns inside and outside and usually address this with line offset from center on the handle. Could the flaps be contributing to this effect?  I built two Jetco Shark 45 models about 10 years apart. Both were just copies of the Jetco kit. Both were as close to being an exact copy of each other as I could get. The second model was just a bit lighter and both models powered by the same engine, the ST. G-51. But both models, to me, flew almost exactly the same. The second model had it's maiden flights at Tucson at VSC in 2005. Bob McDonald was at the grass circles with me, and eyeballed up right and inverted flight for me for a few laps and gave me a thumbs up, so I went tight into the pattern with complete confidence and had no problems. I think I was even using the same lines and handle as the first model. The main issue I had with both airplanes was that they turned outside much easier than inside. I tried all the usual trimming options on both. Both models use Dave Brown tube type push rods and I have never had any problems with these flexing in use before. The Jetco Shark does seem to have quite a bit of spacing on the thrust line, wing centerline, and elevator centerline. I just eventually thought that this might be the factor on this flying trait, and the turn rate is the nature of the beast. Would a spade located on one side or the other of the flap have any effect on how a model turns? Could the flaps be loaded more or less in direction than the other? I couldn't think of any other way to ask the question.
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Offline Mark wood

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Re: Reducing control forces using spades
« Reply #54 on: November 30, 2021, 09:38:44 AM »
   I have been trying to get around to asking this myself. There have been many designs over the years that have these types of "balanced " control surfaces, with the SIG Chipmunk being one of them. Back when I built one during my intermediate class days, it was suggested that they be eliminated and just go with a straight hinge line. I don't know if I have the "feel" that some of you have for subtle control differences. I think I would need several models all lined up in a row with different set ups and fly them ion sequence and hope I could tell the difference!!

   On some models, we experience a difference in how a model turns inside and outside and usually address this with line offset from center on the handle. Could the flaps be contributing to this effect?  I built two Jetco Shark 45 models about 10 years apart. Both were just copies of the Jetco kit. Both were as close to being an exact copy of each other as I could get. The second model was just a bit lighter and both models powered by the same engine, the ST. G-51. But both models, to me, flew almost exactly the same. The second model had it's maiden flights at Tucson at VSC in 2005. Bob McDonald was at the grass circles with me, and eyeballed up right and inverted flight for me for a few laps and gave me a thumbs up, so I went tight into the pattern with complete confidence and had no problems. I think I was even using the same lines and handle as the first model. The main issue I had with both airplanes was that they turned outside much easier than inside. I tried all the usual trimming options on both. Both models use Dave Brown tube type push rods and I have never had any problems with these flexing in use before. The Jetco Shark does seem to have quite a bit of spacing on the thrust line, wing centerline, and elevator centerline. I just eventually thought that this might be the factor on this flying trait, and the turn rate is the nature of the beast. Would a spade located on one side or the other of the flap have any effect on how a model turns? Could the flaps be loaded more or less in direction than the other? I couldn't think of any other way to ask the question.
  Type at you later,
   Dan McEntee

There's a lot to digest in this question Dan. Here's some of the problem in your experience as I see it. Two different airplanes are exactly that two different airplanes totally independent of the design. When they are of one design they are still different. I built lots of F1C's in a from that made them super consistent but the resulting models did perform better or worse. They all would pretty much fly correctly and only took a few trim flights to make them ready for competition.

Removing the horn from the elevator on the Chipmunk I can't truly comment on specifically as I don't have experience with them. However, we're discussing the total hinge moment when we're talking about the CLPA. The flaps are two, three times the area of the elevator and much larger chord. This means they are the primary contributor to control moments. Removing a couple square inches from the elevator isn't likely going to make much difference in total control moments. This is why I specifically focused on the flaps. The current spades are about 7 square inches each. Not small by any means and definitely make a difference. The only question I have is how much is too much? Stay tuned for that one.

So, in terms of A-B testing removing all of the variables as much as can be done is desirable. This makes this spade approach I have a very good candidate for answering questions like this one. Fly with and without and see what happens. I do allot of that. Way more than I should prolly.

To address your specific question I don't have one. But lets review.

he Jetco Shark does seem to have quite a bit of spacing on the thrust line, wing centerline, and elevator centerline. I just eventually thought that this might be the factor on this flying trait, and the turn rate is the nature of the beast. Would a spade located on one side or the other of the flap have any effect on how a model turns?

Done correctly no, they shouldn't. This is a place to point out that they can negatively impact the trim if not properly aligned. This is why I made my first test flights with 60 second flight times. I was fortunate and got it right first effort. They can be shimmed to get the alignment better. When they don't align properly the result is to cause a static deflection until the forces are in balance. That's to say that if the spade isn't align it will cause the flap to want to fly at some non neutral position. This won't change the ultimate maximum deflection and won't change the turning radius. The only thing they do really do is change how much force it takes to get to max deflection.

Could the flaps be loaded more or less in direction than the other? I couldn't think of any other way to ask the question.

I think the above answer covers this.


As for why the airplane turns better one way than the other I think you already have a handle on this. It's a matter of understanding the moments around the CG. The high thrust line has to be compensated by down ward trim from the elevator. If the elevator has uniform deflection, it will have less power to drive the wing AOA in the positive direction and more power to drive in the negative direction. The vertical displacement of the thrust line is a "desirable" feature to counter the precession of the propeller.  A little is good. A lot, not so much. How much, I don't know, buy some Paul Walker Impact plans and copy what he did.

I don't know what my basic opinion is on this one and my experience is that I lean more on symmetry than on balance by asymmetry. The later is always different the former is always the same. The vertical offset, when done properly removes some of the trim force to fly upright and balances this when inverted. The trouble is that it is power and propeller inertia specific. Change one the balance is no longer balanced For me, I prefer x lbs upright stick force balanced with x lbs inverted. That is generally always the case 0 offset engine wise.

The horizontal offset is another issue and may impact the turning radius as well. This one is a necessary evil. The wing changes the departing airflow, wing wake, which changes the AOA of the tail plane. Without enough separation the wing wake will change the AOA of the tail continuously resulting in hunting. Some can help this. but the trade off is that in some maneuvers the wing impacts is greater than others so insides will suffer while outsides benefit form the wing wake. I think Igor did a lot of analysis on this and a good resource is Frank Zaics book, Circular Airflow. Frank did a good job of discussing the impact of the change in flight path on the surface AOA and included some of the wing wake calculations.

Bottom line is I don't think spades will "fix" these. If'n it were me and I thought it was cool airplane, I'd just fly it and be happy. But then again, I like riding scooters too.




Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
“Physics is like sex: sure, it may give some practical results, but that’s not why we do it.” – Richard P. Feynman


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