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Old Aug 27, 2009, 07:37 PM
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Quote:
Originally Posted by flyonline
I recently mass balanced the wings on my 80" Orca pitcheron and it is now rock solid at speed in the dive ...
What is mass balancing?

Frank
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Old Aug 27, 2009, 07:46 PM
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Quote:
Originally Posted by Frank Jarratt
What is mass balancing?

Frank
It's balancing the CG of each wing panel so that it's slightly in front of the center of pressure of the wing (which is nominally where the wingrod is). It's just like setting the CG of an entire plane - you're making each wing slightly positively stable under aerodynamic load.
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Old Aug 27, 2009, 10:52 PM
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Originally Posted by Greygoosegregg
Okay, but if I don't glue the control rod into the wing, Not the main wing rod, but the control rod, then what is to keep the wing from sliding off? The main wing rod slides in and out of the wing, and once the collars are on the control rods, it will be the same thing as the main wing rod. The wing will be able to slide freely on and off.

I wish I could maiden her this Sunday. I will be bagging the second wing tomorrow, and it wont be cured until Sat. I'm waiting for my HS-5645mg to show up in the mail, it might show up tomorrow. Then I have to glue in the servo mounts. Install the wingeron control hardware. And I still have to wait for the robart to get here so I can set the incident. While I'm waiting for that, I'll paint the fuse, and some sort of pattern on the wings. Not to cover the carbon fiber, just to make flying it visually easier. All black wings are tough to see directionally, you know what I mean? Maybe next week some time.

Well, I'm off to the slope. Gonna maiden a Dago Red converted for slope today. Thanks again for your help.

Gregg
Are you talking about the incidence pins? Those are the music wire that go into the wing root, to which you attach the wheel collars? Yes, you do want to glue those in. I'd use epoxy. Sand them a bit to get some purchase.
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Old Aug 27, 2009, 11:10 PM
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Quote:
Originally Posted by c.walker
It's balancing the CG of each wing panel so that it's slightly in front of the center of pressure of the wing (which is nominally where the wingrod is). It's just like setting the CG of an entire plane - you're making each wing slightly positively stable under aerodynamic load.
How do you use the center of pressure as the mass balance point? The location of the center of pressure moves with speed change..... unless it's a symmetrical airfoil.

Adam
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Old Aug 28, 2009, 09:39 AM
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Quote:
Originally Posted by c.walker
It's balancing the CG of each wing panel so that it's slightly in front of the center of pressure of the wing (which is nominally where the wingrod is). It's just like setting the CG of an entire plane - you're making each wing slightly positively stable under aerodynamic load.
I do not want to let this go just yet, since what you did seems to have made a material difference in your setup.

What did you adjust: (1) the CG along the (horizontal) cord of the wing; (2) the vertical CG; or (3) the relative weight/mass distribution of the right and left wings?

Frank
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Old Aug 28, 2009, 10:40 AM
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He's talking about #1 (front to rear balance). Control surfaces, whether they be ailerons, elevators, or in that case, entire wings - have their own center of gravity. The closer that CG is to the pivot point or hinge line, the less likely that surface will be to flutter. For wingerons or pitcherons, this generally means making sure the CG of each wing panel is at or ahead of where the wing rod is located.
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Old Aug 28, 2009, 11:38 AM
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Quote:
Originally Posted by Frank Jarratt
I do not want to let this go just yet, since what you did seems to have made a material difference in your setup.

What did you adjust: (1) the CG along the (horizontal) cord of the wing; (2) the vertical CG; or (3) the relative weight/mass distribution of the right and left wings?

Frank
In my opinion, mass balancing is only an issue if you are encountering flutter or unpredictable pitching.

Adam
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Old Aug 28, 2009, 11:45 AM
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Originally Posted by wyowindworks
In my opinion, mass balancing is only an issue if you are encountering flutter or unpredictable pitching.

Adam
I think that's right. Some DS guys balance control surfaces to avoid flutter. I've never bothered with my pitcherons/wingerons and have not experienced flutter, though I typically have not flown them in monster conditions (no brakes!!)
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Old Aug 28, 2009, 06:21 PM
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So, here is my first wing. It came out really good for my first time bagging a carbon fiber wing. The second wing is pumped down to 4 psi and curing right now. I've also included a couple of pictures of the control rod I'm talking about. It is larger then music wire. Its a 0.098" dia. rod. It slides in and out of the wing right now, but if I don't glue it in, the wing will be able to slide off in flight. Should I epoxy this one in???
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Old Aug 28, 2009, 06:29 PM
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Does the drive pin fit snug in the swing arm slot? If so, you want the pin in question into the wing. If it rattles around then you want a larger pin.

Adam
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Old Aug 28, 2009, 06:44 PM
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Quote:
Originally Posted by wyowindworks
In my opinion, mass balancing is only an issue if you are encountering flutter or unpredictable pitching.

Adam
Agreed here, I occasionally found that my Orca would tuck at high speeds hence my decision to balance.

Frank
after balancing the wings so that the CG of the WING is just ahead/on top of the pivot point you rebalance the entire PLANE so that it has the original CG before balancing the wings. Of course since adding weight you end up with a heavier plane - for me it went from ~17 to ~19 oz/sq'.

Quote:
The 225MG's are what I was going to use, but I'd rather be safe then sorry. Besides, the shrike is a pitcheron, right? So the servo load is half of a wingeron setup. Unless two servos are used as mentioned by Slopepilot.
Actually, because each wing is being driven by 1 servo the load is greater, for a wingeron with one servo the loads of each wing more or less balance each other out (at least as I understand it, I've never flown a wingeron as yet).

If you end up with a small gap between the fuse and the wing, you can either (or both) add a small sliver of balsa to the root and sand to shape or use a piece of felt glued to the root and cut to the shape of the airfoil to give a nice smooth surface against the fuse.

Yes, you do need to glue the drive pins in. I would suggest that you score the glued side of the pin with a file to give something for the glue to bite onto, the ones on my shrike occasionally pop loose on a hard landing which might help save something from braking but it is a little annoying at times.

Steve
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Old Aug 28, 2009, 06:47 PM
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Nice work. Can you increase the vacuum on your bagging system? Something like 12-15 inches might be better for carbon.

And yes, glue in the incidence pin. It's going to be the only thing holding the wing on other than the collar on the end of it...
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Old Aug 28, 2009, 06:51 PM
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Looking very nice! From your photo I suspect a thick piece of felt would work fine to cut the gap.
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Old Aug 28, 2009, 07:14 PM
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Nice!!! Thanks for the info. I'll score the pins a bit when I glue them in, in just the glued area that is... I can adjust the wing/fuse gap to what ever I want at this point. The felt sounds like the way to go, unless someone has a valid point why not to use felt.

I can pull as much as 27psi, but I really didn't know how much to pull without crushing the foam or distorting the wing since I don't have the wing beds. 12- 15psi is OK??? Like I said, this is my first time.
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Old Aug 28, 2009, 07:23 PM
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Quote:
Originally Posted by Greygoosegregg
Nice!!! Thanks for the info. I'll score the pins a bit when I glue them in, in just the glued area that is... I can adjust the wing/fuse gap to what ever I want at this point. The felt sounds like the way to go, unless someone has a valid point why not to use felt.

I can pull as much as 27psi, but I really didn't know how much to pull without crushing the foam or distorting the wing since I don't have the wing beds. 12- 15psi is OK??? Like I said, this is my first time.
The maximum psi that you can get with vacuum is 14.7 psi unless you have an autoclave. I assume you're talking about inches of mercury (Hg).

Many people find that they get less fabric telegraphing with 3k carbons by using lower vacuum levels. In my experience, higher vacuum create a higher degree of telegraphing with coarse bulky fabrics.

Adam
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