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Old Mar 02, 2009, 11:24 AM
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Have you considered the increased possibility of flutter during launch/zoom?

The reason for my concern is not RDS itself. Just that you intend to drive the aileron from the inboard end, where the existing linkage is approx 1/3 span.
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Old Mar 02, 2009, 01:10 PM
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I think that is something to consider, but I think that Tuan considered this on the Xplorer, and it tested fine in practice....
The "fix" would have been to add a strip of bias cloth to the face of the aileron, which I think would only add a gram or two if the epoxy was applied properly.

VR,
Target
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Old Mar 02, 2009, 01:41 PM
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The Ail on the Aspire is not flexible It is very stiff. The Xplorer was more flexible, but even so, I could not get the ail to deflect any while launching it on a powerful FLS winch and on a F3B winch, full zoom etc. It's solid.

I guess I'll build this Aspire stock and if I can get a clean wing will do RDS on that one then.

I havent taken any pictures of the install yet, yesterday carried bags and bags of rock and manure (potting soil) for the planter box...
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Old Mar 03, 2009, 01:37 PM
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Man, I can't get myself to build this Aspire stock. I keep wanting to move the servos inward.

This may be a little off topic, but I didn;t want to start a new thread just on ... or maybe I should.

I went on to the http://www.charlesriverrc.org site to see if I can get some info as to how much improvements to flying by bringing weight inward didn't find such info.

I noticed the 2m Aegea that Dr. Drela builds... has anyone taken a close look at the wing servo locations? Looks very similar to the Espada's. The servos are at the cooresponding roots of the control surfaces.

More hmmm...
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Old Mar 03, 2009, 02:17 PM
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Remember that Dr. Drela has his servos inboard on a plane that weighs around 50 ounces - your plane is going to weigh 60% more than that. In theory it will make your tips lighter. Will you be able to tell the difference in flight? I doubt it.

That being said, this RDS thing has consumed you to the point you'll never be happy if you don't do it, so go ahead and do the RDS so we don't have to worry about you losing sleep over it Heck, lets do mine RDS too. I'm feeling you, Tuan!!

Look forward to flying them together.

Clay
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Old Mar 03, 2009, 03:01 PM
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Tuan,

By moving the servo inboard, I presume you're after reducing the roll inertia, to improve handling. If so...

Basic moment of inertia is governed by the equation I = M * R^2, where M is the mass, and R is the distance from the center of the wing. I computed an estimated moment of inertia for an entire wing before/after moving the servo, and compared the values. Feel free to correct me, if needed.
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Old Mar 03, 2009, 03:10 PM
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Quote:
Originally Posted by ClayH
Remember that Dr. Drela has his servos inboard on a plane that weighs around 50 ounces - your plane is going to weigh 60% more than that. In theory it will make your tips lighter. Will you be able to tell the difference in flight? I doubt it.

That being said, this RDS thing has consumed you to the point you'll never be happy if you don't do it, so go ahead and do the RDS so we don't have to worry about you losing sleep over it Heck, lets do mine RDS too. I'm feeling you, Tuan!!

Look forward to flying them together.

Clay
LOL Clay... I had to put the Aspire away last night cause the self debate was getting to me. I took out the Orange X and started hacking away.

Really off topic but just so no one thinks I am neglecting the family :
I get to work on these between 10pm-1am. I still get to spend lots of time with wife and kids. I've rarely watch any tv... maybe... some sports here and there. My wife does make me watch 24 with her, but we watch that online well after the episode is aired. It only takes about 45 minutes to watch an episode. BTW, I never see Jack eat or ....
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Old Mar 03, 2009, 03:14 PM
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Quote:
Originally Posted by nuevo
Tuan,

By moving the servo inboard, I presume you're after reducing the roll inertia, to improve handling. If so...

Basic moment of inertia is governed by the equation I = M * R^2, where M is the mass, and R is the distance from the center of the wing. I computed an estimated moment of inertia for an entire wing before/after moving the servo, and compared the values. Feel free to correct me, if needed.
WOW Nuevo, thanks for this! Correct you?!!? I wouldn't know what is even wrong .

Could you do one for ail at 28g. Of course that is on each side. With wiring, and frames etc. I find it is about an ounce. Thank you!
Tuan
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Old Mar 03, 2009, 03:25 PM
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Nuevo,
I got so excited that you calculated this I went and took the box down and measured it to get a better idea.

Stock from center panel to center of Ail servo would be 44.5" (113cm)

If move ail servo inboard it would be from center of wing to center of ail aervo 27" (68.6cm), a change of 17.5" (44.5cm)

Thank you!
Tuan

Nevermind, I just saw how you did the calc, let me try it.
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Old Mar 03, 2009, 03:26 PM
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Nuevo, good start, but this parrallel axis approximation is neglecting the moments of inertia of the parts themselves. The moments of inertia of the wing center panel, and tip panels will play a significant roll in the moment of inertia about the roll axis. This will most likely reduce the the 3% to 2.5%. Basically making a small number a little smaller. I only carred to point it out because you asked.

Again, I doubt you could tell the difference in flight. I am Pro RDS, but I would leave the servos in their stock location in the wing tip rather than cutting another hole in the center panel. But then again, I am one of those F3B boys who tries to blow the plane up on every launch.

Go Tuan, do it exactly how you want, or you will be wondering what if for the rest of the model's life.
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Old Mar 03, 2009, 03:42 PM
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I redid the calc using closer numbers and got:

Is this even considered enough to make a change? 5.4%
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Old Mar 03, 2009, 03:44 PM
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my numbers are very rough, as I'm taking wild guesses at the center of mass of the various wing sections. Note how the tip has 10 times the inertia of the aileron servo in the standard installation. Thanks djklein21 in pointing out just how simplistic my assumptions are. I'm not a mechanical guy, but I figure these #'s are a good approximation.

Tuan, I come up with approx a 5% change after using your new numbers. Changed #'s in red. ~5% change in roll authority on such a big bird. I might go for it, but I'm getting lazy the past few years.

I've attached my spreadsheet, if anyone wants to improve on it. The web stuff made me put it in a .zip file to upload.
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Old Mar 03, 2009, 03:50 PM
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Ha, I just caught my mistake too.

Thank you! thank you! thank you!

Dave, if yo are referring to the the mass center of the panels, Nuevo already took that into consideration, if not then I have no clue what you are talking about
Tuan
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Old Mar 03, 2009, 06:03 PM
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Interesting stuff guys, keep it up. I am really looking forward to flying my first RDS in the Ceres Lt. I will admit, that this is one of those things that I would want to fly to confirm what the spreadsheets are showing. It is like measuring CG, day one is close to someone's measurement and then from there on it is what "Feels" right. I know on my Zenith, not only would you be able to move some mass around, but also, you could ditch those huge covers over the pushrod exits. If I did not make the flying mistakes I usually make, all this might make a difference, will keep watching how it plays out.

You all keep talking about this, the makers may just go from here and start them in TD/FAI stuff too.

Marc
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Old Mar 04, 2009, 12:27 PM
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So guys, where are you all getting the Aspire from? Before I ordered my Orca from Skip Miller Models I tried to order an Aspire and was told that they were not going to be built anymore. Now I see that several of you have already received them or will real soon. I am sure I will love my Orca when it gets here but the plane I really wanted was the Aspire. Inquiring minds want to know.

See Ya,

Pat
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