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Old Apr 30, 2005, 09:43 PM
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motorhead's Avatar
Kansas, USA
Joined Sep 1999
4,004 Posts
How do you make a rudder more effective?

I have quite a large rudder already but as much authority as I would have thought. The vertical stab is 3" at the bottom, 1" at the top and 5" tall. The rudder is 2.5" at the top, 4" at the bottom and 7.5" tall. The plane is 32" wingspan. I have about 40 deg of throw.
I can see in flight that the rudder is deflecting all the way so that is not the problem. I am just looking for ideas.
Mike
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Old Apr 30, 2005, 09:49 PM
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cham's Avatar
Garden Grove, California, United States
Joined Apr 2004
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More forward throw with the left thumb.
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Old Apr 30, 2005, 09:56 PM
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College Station, TX USA
Joined Dec 2003
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I would think about extending it higher, or adding on to it in the back, not too much though because if you go too much it will want to snap at full, only 40 degrees, if you can get more, do that, usually I try to get at least 60 degrees.
Keep'em Flying,
Nick
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Old Apr 30, 2005, 11:15 PM
Lance Armstrong- 7 times!
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Madison, Wisconsin
Joined Sep 2001
1,335 Posts
Add fuselage side area.

-Hans
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Old Apr 30, 2005, 11:37 PM
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College Station, TX USA
Joined Dec 2003
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Yes, you can do that, but it is a huge change compared to just playing with the size of the rudder. The true question, will if knife edge fine and just not have enough athority in a hover, or knife-loop, or something, if so then you need to enlarge the rudder, but if it struggles with knife and anything in knife flight then you need more side area.
Keep'em Flying,
Nick
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Old Apr 30, 2005, 11:43 PM
ProBro Spaz
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Buffalo, NY
Joined Aug 2004
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Quote:
Originally Posted by flybike
Add fuselage side area.

-Hans
Very true, fuse area to a rudder is like wing area to the elevator
Look at how small the tensor rudder is for example, the fuse and side force gens area is like a solid fulcrum for the rudder to lever against.. same as you canít do a tight loop with little or no wing
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Old May 01, 2005, 08:31 AM
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Joined Oct 2004
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Guys, I don't think he wants to build a new fuselage.

One option is to add SFGs.

Another option is to add an aerodynamic counterbalance.

noodle
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Old May 01, 2005, 10:02 AM
Registered User
Taipei Shek, Taiwan
Joined Aug 2004
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Quote:
Originally Posted by noodle
Guys, I don't think he wants to build a new fuselage.

One option is to add SFGs.

Another option is to add an aerodynamic counterbalance.

noodle
Another option is to trim out some vertical stab./rudder area.

No I'm not kidding. It's similar to adding fuselage area in that the yaw neutral point is moved forward.
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Old May 01, 2005, 10:18 AM
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Gilbert, AZ
Joined May 2003
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Could you get a picture of your design? Like YoyoML said, you can gain a lot of authority by removing vertical fin area, while keeping rudder area the same. Of course, more throw almost always helps

Dan
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Old May 01, 2005, 10:27 AM
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Tennessee/Mid-South US
Joined Mar 2002
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Quote:
Guys, I don't think he wants to build a new fuselage.

One option is to add SFGs.

Another option is to add an aerodynamic counterbalance.

noodle
Noodle, he may not want to modify his fuse, but Spastic is right. Adding more rudder will not always get you more authority. At a certain point, it actually becomes very counteractive to good performance. Getting the right amount of fuse area, with the proper amount in front of and behind the CG makes a much bigger difference.

Motorhead, if its a depron profile, you may just want to 'scab on' extra area on the fuse. I've done this before by slicing off the bottom and top of the fuse, and adding in an appropriately thick strip of depron to raise the top and lower the bottom half.
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Old May 01, 2005, 11:19 AM
kalteisen.com
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Omaha, NE
Joined Aug 2003
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Spaz and Match are dead-on.

On my Pitts, the rudder is small, by anybody's standards, but is wicked powerfull because of the fuse area I have.
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Old May 01, 2005, 02:28 PM
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motorhead's Avatar
Kansas, USA
Joined Sep 1999
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It is on my new full shaped fuse design. I have added to the rudder already, more than in the picture below. I do not want to change the fuse because it is the whole basis of the design. I know that the round shape will make knife edge need more AOA. The problem is I need more authority to get the AOA. I also want more control for hovering. I will add more throw first then try removing some of the vertical area. Thanks for the tips.
Mike
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Old May 01, 2005, 03:13 PM
My other car...
noodle's Avatar
Joined Oct 2004
727 Posts
Quote:
Originally Posted by matchlessaero
Noodle, he may not want to modify his fuse, but Spastic is right. Adding more rudder will not always get you more authority. At a certain point, it actually becomes very counteractive to good performance. Getting the right amount of fuse area, with the proper amount in front of and behind the CG makes a much bigger difference.
Yeah, I know, but it really depends on what he's having trouble with. And yes, too much rudder can be detrimental. But I was thinking if he was having a hard time with hovering etc. he could probably add rudder area with good results.

Now that I've seen the plane, and heard more about the problem, I say use SFGs.

noodle
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Old May 01, 2005, 03:50 PM
Team Futaba
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Rochester New York
Joined Oct 2004
954 Posts
On big 3D and other planes I have seen them add on a little corner piece on each side of the rudder to make it more effective I havent tried it on anything of mine but I believe it works and it might be worth a shot there is no drastic change of your airfrain only little pieces of plastic taped on. not really any work involved.
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Old May 01, 2005, 09:08 PM
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United States, CA, Walnut
Joined Oct 2004
335 Posts
From the picture, it looks like a larger prop would help.
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