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Old May 25, 2012, 10:56 AM
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United States, CA, Thousand Oaks
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Radio Activ. What size CF did you use on the boom, elevator, and stablizer. Is the elevator and stablizer CF a rod or flat stock.
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Last edited by mshoe; May 25, 2012 at 11:12 AM.
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Old May 25, 2012, 11:33 AM
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Old May 25, 2012, 11:33 AM
Tossing planes into the snow
Canada, BC, Smithers
Joined Nov 2011
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Just an observation...on most planes, the rudder hinge line is more or less vertical (perpendicular to the thrust line). On the Radians, it angles up and back, and that means that rudder deflection will tend to push the tail down, acting like a little bit of up-elevator. I'm sure there must be a reason for that design, and I wonder what it is?
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Old May 25, 2012, 11:59 AM
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Old May 25, 2012, 12:31 PM
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Canada, ON, Pickering
Joined Nov 2006
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The angled back rudder is an old trick from before computer radios and mixes, mostly used on rudder and elevator planes. My old Marks models Windfree glider has quite an angle on it.
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Old May 25, 2012, 12:38 PM
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United States, WI, Appleton
Joined Jul 2010
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I'm struggling to see how having a swept back rudder hinge line would induce an 'up' force. Having more rudder at the bottom may move the center of force closer to the cg (reducing yaw/roll coupling), but that's about all. I checked through my design stuff, and the one big negative I came across for having a swept back rudder hinge line is lowering the spanwise efficiency of the vertical when the rudder is used.

My personal theory for the rudder design is, it looks cool. Mine looks considerably less cool than the original now though, as I cut off the rudder overhang at the top and glued it to the fin to get a more conventional rudder configuration.
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Old May 25, 2012, 12:44 PM
Tossing planes into the snow
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Quote:
Originally Posted by Jimmitude View Post
I'm struggling to see how having a swept back rudder hinge line would induce an 'up' force.
The deflected rudder would push down on the tail, and that would angle the nose up.
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Old May 25, 2012, 12:47 PM
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Canada, ON, Pickering
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it definitely has an effect of keeping the nose up. imagine a rudder at 45deg tilt, when you turn it along the inclined hinge axes and exaggerate the swing to 90 deg you can see that the surface acts like a ramp on an angle not only directing the air right or left but up also. It does work to a small degree. I am not sure if you can visualize what I said, but it works. Especially with long tail moments gliders have.


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Originally Posted by Jimmitude View Post
I'm struggling to see how having a swept back rudder hinge line would induce an 'up' force. Having more rudder at the bottom may move the center of force closer to the cg (reducing yaw/roll coupling), but that's about all. I checked through my design stuff, and the one big negative I came across for having a swept back rudder hinge line is lowering the spanwise efficiency of the vertical when the rudder is used.

My personal theory for the rudder design is, it looks cool. Mine looks considerably less cool than the original now though, as I cut off the rudder overhang at the top and glued it to the fin to get a more conventional rudder configuration.
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Old May 25, 2012, 01:34 PM
Tossing planes into the snow
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How can it get any better than this. Not only was my question answered, but something else that I have been wondering about was also explained. That was the business about the jog in the rudder, instead of having the hinge extend all the way to the top. Now I see that it helps to take the strain out of the system by providing a force in the opposite direction.

That design was also used in the Corsair, which is one of the coolest looking planes ever made. Looking cool was not the intent of the designers, but it just happened that way. They were being pounded by the Japanese in the pacific, and the Corsair helped to win that war. The design parameters were: Take the biggest engine in the world, put a huge prop on it, and stick it in the smallest possible airframe. They ended up with one of the fastest and most agile planes ever made. Not only that, but one of the design parameters was that it also had to be able to fly slow enough to land on an aircraft carrier. As you can see, it also has that offset rudder design just like the Radian Pro. Until today, I wondered why they made it like that.

I already have a CF tube epoxied into the underside of the fuselage, so pushing the small CF rods up from the bottom was not an option. I shoved them in from the top, and it should work fine.

Edit: I was just waiting for some glue to dry and realized...they did the same thing with the horizontal stabilizer, by having an offset built into it. If you were pulling hard elevator on the Corsair, the blue "tabs" on the outer ends would be relieving the system of some of the tension.
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Old May 25, 2012, 05:11 PM
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United States, WI, Appleton
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Re: angled rudder. Fair enough, I can visualize what you're saying. I've designed a bunch of airplanes and built many more and have honestly never come across that idea/theory, but then again, I think all of them have had control surfaces pretty much normal to the local flow, so I just haven't had to worry about it! Hey, I'm always open to learning.

Re: the contol overhang, especially on the Corsair and other older airplanes, you're exactly right, it was put there to reduce the control forces down to what a pilot could stand, especially at high speed. I cut mine off because one of the adverse things about it is that if you use full rudder throw (especially if done quickly) you can stall the overhang, which reduces the rudder force just when you probably need it. I never had that issue, but I figured since I had it apart anyway to re-hinge it, why not. The mod didn't really change it's response at all.
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Old May 25, 2012, 07:52 PM
What you looking' at fool!
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Australia, WA, Morley
Joined Mar 2011
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And another thing

Another reason for the "overhang" on the rudder is to reduce the chance of control surface flutter. You will also see it on some ailerons.
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Old May 25, 2012, 08:24 PM
Tossing planes into the snow
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Originally Posted by GlidingFool View Post
Another reason for the "overhang" on the rudder is to reduce the chance of control surface flutter. You will also see it on some ailerons.
Interesting...so what about that "spike" on the Corsair that is just ahead of the overhang on the rudder. Is that to provide some sort of buffer to reduce flutter at high speed?
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Old May 25, 2012, 10:38 PM
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Nope, that was to protect and stop flying debris from jamming into the crack, these were fighters, shooting at each other, there was lots of flying pieces ripped out with those machine guns, lots of armor plate around the pilot too.

Quote:
Originally Posted by Jovanx View Post
Interesting...so what about that "spike" on the Corsair that is just ahead of the overhang on the rudder. Is that to provide some sort of buffer to reduce flutter at high speed?
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Old May 26, 2012, 01:00 AM
Dixie Normious
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Can A da....Ehh!!
Joined May 2010
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Heres a little video of the other day, This was the biggest thermal ive hit. Kinda scary!
My friend was flying his RP as well, got a few shots of him in the frame!

Just got word that there are 3 more RP's on order by club members. Thats 6 in total...this is going to be fun!!
The sound was weird, not sure why the gopro was making it, first time I've experienced it. But i have toned it down
Thermal Hunting With Radain Pro (6 min 39 sec)
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Old May 26, 2012, 02:13 AM
Bring It On !!!!!
soundcheque's Avatar
Newmarket, England.
Joined Aug 2006
689 Posts
Here's pictures of the addition of servo horn fairings from another Parkzone aeroplane.

Also the new prop and spinner. Looks heavy but it's quite light . It's a 50mm spinner but as the stock item is 52mm it looks a tad small.

Prop is only a 9 x 7 currently as it was in my collection. A 10 x 8 is on delivery.


CG at 70mm with 3s 2200mah lipo.
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Last edited by soundcheque; May 26, 2012 at 02:19 AM.
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