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Author Topic: Do we need the rudder deflected in stunt?  (Read 556 times)

Offline Matt Piatkowski

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Do we need the rudder deflected in stunt?
« on: July 21, 2021, 10:38:57 PM »
Hello,
I will be flight testing my LA-4e from Leonidov, Ukraine, soon.
It is called Big Yellow (attached).

The plane has a rudder installed at 0.0 deg. To deflect the rudder outside a surgery is needed.

The thrust is also at 0.0 deg.

Do I need to deflect the rudder and leave the trust at 0.0?
If yes: how much for the first flights?
Do I need to deflect the thrust direction?
Do I need both?

Big Yellow is powered by Cobra Kv550 and/or T-Motor Kv550 and 13.5 x 5.5 x 3 carbon composite Kravchenko F2B propeller or /and by Badass Kv710 and 12x6x4 custom made carbon composite propeller. I am using TP 6S 2800, Spin66 F2B ESC and Igor's active timer. The RTF weight is 1840 grams (64.9 oz.). Wings loading: 13 oz./ft.^2. Lines length (y-t-y): 67 '

Thank you,
M

Offline Paul Walker

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Re: Do we need the rudder deflected in stunt?
« Reply #1 on: July 21, 2021, 10:46:16 PM »
It depends upon who you ask.

I don't use rudder offset, Igor does.

You must find what works for you. Requires trial and error.

Good luck


Online Brett Buck

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Re: Do we need the rudder deflected in stunt?
« Reply #2 on: July 21, 2021, 11:15:35 PM »
The plane has a rudder installed at 0.0 deg. To deflect the rudder outside a surgery is needed.

The thrust is also at 0.0 deg.

Do I need to deflect the rudder and leave the trust at 0.0?

   No, fly it as is. Adjust if necessary.

    Brett

   p.s. Paul and I do not have a hotline to consult and gang up on you...

Offline Motorman

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Re: Do we need the rudder deflected in stunt?
« Reply #3 on: July 22, 2021, 08:51:26 AM »
Suggested color scheme in my avatar.

Motorman 8)
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Offline Ty Marcucci

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Re: Do we need the rudder deflected in stunt?
« Reply #4 on: July 22, 2021, 09:39:20 AM »
The irony of rudder off set is at high speed where it works, it's not needed. At low speed where it is needed, it does not work.  It can cause more trim problems than it solves. D>K
Ty Marcucci

Offline Mike Griffin

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Re: Do we need the rudder deflected in stunt?
« Reply #5 on: July 22, 2021, 09:49:46 AM »
Short answer "no".  I have on rare occasions used engine offset wedges when using glow power.  I have not used electric enough to speak intelligently about it. Brett and Paul gave good advice.


Mike

Offline Ken Culbertson

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Re: Do we need the rudder deflected in stunt?
« Reply #6 on: July 22, 2021, 11:12:34 AM »
I am of the opinion that it is not necessary in most cases.  Planes designed before the power revolution really needed it.  Now you don't need fixed rudder offset until all other trim fails.  However, "on demand" like Al and Keith's can be beneficial. I have grown to like having just a touch of rudder as I give the plane control, 1/16" on inside to 1/8" on outside. I prefer engine/motor offset if I have a yaw issue.  I can't figure out why yet but motor offset seems to work better with electric and as a result you can use a bit more.

Ken
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Offline FLOYD CARTER

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Re: Do we need the rudder deflected in stunt?
« Reply #7 on: July 22, 2021, 01:52:22 PM »
A few designs actually benefit from slight rudder offset.  I usually hinge my rudders, with a simple clevis to adjust offset, if needed.
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Offline Dave_Trible

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Re: Do we need the rudder deflected in stunt?
« Reply #8 on: July 22, 2021, 03:04:22 PM »
I usually have just a little- maybe one or two degrees.  This much makes sure a fuselage shape problem or something else (like longer inboard wing panel- more drag) doesn’t turn the airplane the wrong direction in towards you.  A little can help keep the lines tight up top and shouldn’t create any major trim issues.

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Offline john e. holliday

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Re: Do we need the rudder deflected in stunt?
« Reply #9 on: July 22, 2021, 03:56:53 PM »
I vaguely remember an article the late great Bob Palmer wrote that a rudder is only useful in the glide. D>K
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Offline Air Ministry .

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Re: Do we need the rudder deflected in stunt?
« Reply #10 on: July 22, 2021, 11:15:19 PM »
If its a left hand propellor , clockwise rotation standling in front looking at the nose , no .  Otherwise ' thats a good question ' .

Tip Weight , engine ( thrust line ) offset , and rudder are interrelated .

No Offset & I would get generous with the tip weight initially , rather than stingy . Tip weight tends to hold em tight, even if it flings the tip a bit . Better than it coming at you .

After say a dozen flights - youll get it dialed in closer . So take cut / weighed / fittable spare weights . Play it safe being generous there for starters . Teeth are expensive if it hits them .  %^@

Id put a piece of cellotape along that forward part of the leadout guide too , to stop it catching the wind . to say 5 mm from the front leadout . Replace the tape occasionally .

Offline Mike Griffin

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Re: Do we need the rudder deflected in stunt?
« Reply #11 on: July 22, 2021, 11:31:20 PM »
I do sand an airfoil in the rudder if the material is thick enough on a good sized stunter.  I Usually do not bother with it on something like a Ringmaster.  I am sure everyone else does also.

Mike

Offline PJ Rowland

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Re: Do we need the rudder deflected in stunt?
« Reply #12 on: July 22, 2021, 11:43:54 PM »
Really?

Your BUYING a plane, and want to ask for advice?

How about spend 30 years, practice,  build, fly, trim.. then you might figure out the answers to some of this stuff.

Thats the REAL answer.

I mean I dont even understand the purpose of the question.

Your asking does a fin need offset ?

The answer is ..

Yes offset can help.
The answer is also NO offset can help.

This is my point.. BOTH answers are valid. There are many proponents of zero offset. There are many proponents of some offset.. some even suggest movable rudder for offset.

But if you buy to fly you will NEVER i repeat NEVER understand why one works vs another.


Better solution would be to buy the plane and just fly it. If your THAT skilled that you can detect minor trim issues with a handbuild composite stunt plane, then either modifiy it or build your own that match your pilot ability.







If you always put limit on everything you do, physical or anything else. It will spread into your work and into your life. There are no limits. There are only plateaus, and you must not stay there, you must go beyond them.” - Bruce Lee.

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 I Yearn for a world where chickens can cross the road without having their motives questioned.

Online Brett Buck

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Re: Do we need the rudder deflected in stunt?
« Reply #13 on: July 22, 2021, 11:50:37 PM »
I do sand an airfoil in the rudder if the material is thick enough on a good sized stunter.  I Usually do not bother with it on something like a Ringmaster.  I am sure everyone else does also.

  I never do that, no offset nor airfoil in the fin (which are the same thing). We have spent a lot of time cutting completed airplanes with Zona saws to remove it. Put the fin on *dead straight ahead*, make the rudder adjustable in very fine increments. Play leadouts position off against rudder offset to minimize yaw transients in corners. I recommend using the rudder as the independent variable, set it, then adjust the leadouts to minimize yaw transients. That does not mean "put in offset, move leadouts forward to drag the nose back tangent", quite the opposite, so *do not want* the adjustments fighting each other.

   Rudder offset is an extremely powerful adjustment, even a tiny offset will make a HUGE difference, particularly around zero.

     Brett

Offline Ken Culbertson

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Re: Do we need the rudder deflected in stunt?
« Reply #14 on: Yesterday at 07:27:12 AM »
Rudder offset is an extremely powerful adjustment, even a tiny offset will make a HUGE difference, particularly around zero.
     Brett
This statement is very true.  Anyone who has competed with sailplanes and done spot landings will know.  Please correct me if my reasoning is wrong.  I have been using Keith's CAM rudder now for my last three ships.  I think I set it up differently than Keith intended but it works for me very well.  My desire was to increase line tension in two places.  Entering corners and the overhead 8.  By increasing, I am really saying compensating for the loss.  I am 100% electric now so "thinking" about what the motor is doing has faded away and my concentration has shifted to shape and elevations where it belongs.  How much offset did it take to accomplish this?  1/16" on insides increasing to 1/8" on outsides.

I have flown 2 ships with Igor's timer and I think it accomplishes the same thing.

Ken
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