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Old Sep 11, 2013, 11:54 AM
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United States, CA, Tehachapi
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Yup. Mine are 12mm servos and the topdrive is buried nicely
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Old Sep 11, 2013, 12:55 PM
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Originally Posted by JimZinVT View Post
Ordering from CST, The price of CF fabric doesn't really improve until you get to the 5.7 oz weight. Too heavy for a tip patch? ACP seems to charge double what everyone else is asking and no one else even sells the lightweight fabrics we want. So CST looks like the only one-stop source here in the US?
Jim and/or any others who are working on bagging your first wing - I agree with Brandon that a glass doubler is likely to suffice. Having said that, I have plenty of lightweight (~2oz) carbon off-cuts and would be happy to send you enough to do a top and bottom surface tip doubler if you send me a stamped, self-addressed envelope. PM me for address info.

-John
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Old Sep 11, 2013, 05:19 PM
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Is the purpose of the tip patch to tie the blade to the spar system? To beef up the tip against bending or twisting forces from an imperfect launch? Both? Just trying to understand the mechanics.

Is the tip patch typically just on the blade side, or on both tips to try and keep the weight balanced?
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Old Sep 11, 2013, 07:24 PM
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What is usually meant by the term "pre-facing" of aileron cut outs?
Is it just some extra sking reo in the form of carbon tow or uni-carbon?
Or is the actuall drag spar face and control surface LE "faced" with something prior to bagging?
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Old Sep 11, 2013, 08:31 PM
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Rather than describe the pre-facing in detail, do a search on Google that starts out with "RC Groups ... and you will finds several really good descriptions of the process.

Basically, it entails joining the top and bottom skind of the wing and flaps with fg to stiffen the flaps and prevent delams of the hinge area.

Gary
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Old Sep 11, 2013, 08:51 PM
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Originally Posted by JimZinVT View Post
Is the purpose of the tip patch to tie the blade to the spar system? To beef up the tip against bending or twisting forces from an imperfect launch? Both? Just trying to understand the mechanics.

Is the tip patch typically just on the blade side, or on both tips to try and keep the weight balanced?
You nailed it. The purpose is to provide a load path from the blade to the spar, strengthen the tip against strong bending/twisting, and to increase durability. I like to make tip doublers on both sides for durability. Haven't built one without tip patches on the non-throwing side so I can't tell you how much of a difference it makes in balance.
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Old Sep 11, 2013, 10:31 PM
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Originally Posted by Jim.Thompson View Post
What is usually meant by the term "pre-facing" of aileron cut outs?
As I understand it, you're wrapping the trailing edge of the wing and the leading edge of the aileron with light fiberglass before bagging. 3M77ed on as you would a leading edge strip. Makes for a stiffer aileron and helps prevent flutter. But one of the benefits Bwill6 mentioned for this thicker HM51 airfoil is no need to face....the thickness makes a stiffer structure.
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Old Sep 11, 2013, 10:57 PM
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Pre-facing explained.

Quote:
Originally Posted by GaryO View Post
.........................., do a search on Google that starts out with "RC Groups ... and .................................................. ............
Gary
Found this excellent drawing and description of the process courtesy Dr. Mark Drela.
http://www.charlesriverrc.org/articl...DFs/hinges.pdf

Thanks.
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Old Sep 11, 2013, 11:02 PM
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Good that you found Mark's posts.

Also look for a series of posts by Gerald )GT) and Phil Barnes, maybe in the original Zone thread on an alternate way to do it. I find it much easier to do.

Gary
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Old Sep 11, 2013, 11:03 PM
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Originally Posted by JimZinVT View Post
.................. But one of the benefits Bwill6 mentioned for this thicker HM51 airfoil is no need to face....the thickness makes a stiffer structure.
I don't quite "get" this rationale.
I'll be pre-facing anyway I think. I tend to like to do anything and everything I can on the bench to avoid later possibility of progressive failure on the flying field etc.
Besides, after just finding another elegant build technique, I can't put off trying it out!

I'm starting to get excited about building a DLG. I'm packing the car now for a week long slopefest! Will be starting the build when I return.
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Old Sep 11, 2013, 11:05 PM
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Originally Posted by GaryO View Post
Good that you found Mark's posts.

Also look for a series of posts by Gerald )GT) and Phil Barnes, maybe in the original Zone thread on an alternate way to do it. I find it much easier to do.

Gary
I found the ones by Phil (I think) and have book marked them for reading them when I return.
Good stuff! Isn't the internet fantastic?
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Old Sep 11, 2013, 11:45 PM
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Another advantage of pre-facing, besides increased stiffness, is that the skins adhere much better at the hinge line and are less likely to peel or delaminate.
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Old Sep 11, 2013, 11:57 PM
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Another advantage of pre-facing, besides increased stiffness, is that the skins adhere much better at the hinge line and are less likely to peel or delaminate.
For sure. All the sloper wings that I've built are faced, both vac bagged and moulded. However, they were done with "Q" cells/epoxy splooge on the bagged ones, and glass socking over drinking straws for the moulded ones.
But that is drifting off topic a bit..............
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Old Sep 12, 2013, 12:15 AM
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Stiffness (both bending and torsional) is nonlinearly proportional to thickness of the wing. ie: as thickness goes up, stiffness goes way up. Flutter is caused by ailerons with poor torsional stiffness. Facing the ailerons closes the "torsional tube" that is the aileron, boosting stiffness by a ton. Thinner wings require it. This wing has thick enough ailerons that they are stiff enough to not flutter even without facing as long as you use a 40+ psi foam like Hiload 40 or 60. Like Wazmo said, another advantage of pre-facing is that it prevents delamination at the hinge line.
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Old Sep 12, 2013, 12:48 AM
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Originally Posted by bwill6 View Post
.............. another advantage of pre-facing is that it prevents delamination at the hinge line.
Its this advantage that is foremost in my mind and will motivate me to face mine.
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