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Old Apr 23, 2012, 06:46 PM
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hog2soar's Avatar
Central California
Joined Jan 2010
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Question
Shear Web wood grain going the wrong direction...horizontal

I just inherited a 100" unfinished wing from my nephew. I was going to build a fuselage and tail feathers for it,but I just noticed the grain of wood on the shear webs are horizontal not vertical

I'm afraid if I try and remove them I'll break something(ribs,spar) just trying to fix it. And end up making a bigger mess out of it.

He didn't know what the wing was for or who the manufacturer was. I haven't looked around yet to see if I can find a similar wing.

I have a spare motor sitting around. So I can add the motor and it won't have the stress of a winch or Hi-Start on the wing.

Should I try and remove them and put them in vertically,or just leave it alone?

The spars are 1/8"x 3/8" with no carbon or wrapping.

What would the stresses be with webs horizontal?

I don't want to go to all of the trouble of building something,just to have the wings foldd on the first flight.

Thanks for any info.

Eddie
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Old Apr 23, 2012, 07:00 PM
I HATE GLOW PLUGS!
SrTelemaster's Avatar
United States, NY, St Lawrence
Joined Feb 2012
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Hiow about laminating some carbon fiber on them?
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Old Apr 23, 2012, 07:10 PM
cq cq de kr4is
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USA, VA, virginia beach
Joined Jan 2011
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carbon laminate spar and then wrap them with kevlar tow,,ask any verizon fios guy for scaps of fiber optic line,,(,he will give it up less it goes to trash),,too harvest the kevlar tow from inside the line, you got your free wrap. cheap and winch "proof".
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Old Apr 23, 2012, 07:30 PM
Duane
Wazmo's Avatar
No. VA
Joined Nov 2004
1,467 Posts
Wood shear web grain orientation makes only a small difference. I'd leave it as is.
http://www.rcgroups.com/forums/showthread.php?t=1368226
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Old Apr 23, 2012, 07:38 PM
the flying is good
dephela's Avatar
USA, CT, Hamden
Joined Oct 2002
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+1, 1/8 x 3/8 spars aren't very hefty.

EDIT: So what I really meant was that there's no real reason to change the grain direction. I wouldn't do anything else to it either,, never had a problem with a spar like that unless it got really waterlogged.
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Last edited by dephela; Apr 24, 2012 at 11:30 AM.
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Old Apr 23, 2012, 07:46 PM
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United States, NY, Lewiston
Joined Apr 2011
323 Posts
Maybe add some vertical grain sheet webbing glued to the front and rear of the spar, at least in the center section area
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Old Apr 23, 2012, 09:26 PM
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USA, FL, Milton
Joined Jul 2008
119 Posts
I'd just scab some vertical grain shear webs right over the existing horizontal ones, as ghost tanker says. The shear stress should then be shared between the horizontal grain webbing and the vertical grain webbing.

In theory, the vertical grain webbing prevents the upper spar from slipping outward relative to the lower spar as the wing tip deflects upward under positive g or lift force. Probably really only a factor on launch.

lc
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Old Apr 24, 2012, 04:54 AM
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United States, MA, Waltham
Joined Dec 2001
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1/8 X 3/8 is strong enough if the grain is straight, it's decent wood, the wing is not super thin, and the construction is of good quality. The Bird of TIme, a classic old design, has a much larger span and uses spar caps of this size.

Does it have a wing joiner rod? If it's 7/32, you will probably bend quite a few of them without damaging the wing. Possibly even with 1/4 inch, same size as in the Bird of Time. I don't think there's any need to go larger than that on a 100 inch wood wing unless it's absurdly heavily built.

If you're really worried, you could always do some glass cloth and epoxy over the shear web in the inner part of the wing. There should be plywood shear webs or wrapping or something where the wing rod is, though.

If you can show us a picture of the wing, perhaps we can recognize it.

Years ago, using the same size winch motors we use now, we all learned to tap the pedal so as not to rip our gliders apart. Suggest you practice tapping without launching and with the winch turned off until you get the hang of it. Or, if you have drop foot, do carbon to the max. (i.e. if you can't pick up your foot) I've only ever broken a wood wing on launch on purpose, though I had a glider with a carbon spar and carbon cloth covered wing, which I had too much confidence in, and managed to break on launch.
page 20 here should be interesting:
http://www.scribd.com/doc/79832480/R...igest-Apr-2005
should also be findable here:
http://www.rcsoaringdigest.com/
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Old Apr 24, 2012, 05:53 AM
turn, turn, turn.
Athol, Massachusetts
Joined Oct 2005
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I was waiting for Lincoln to chime in....
And there you have it.
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Old Apr 24, 2012, 11:02 AM
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Fresno CA
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Eddie, just leave it alone!

Blue Skies..........................Tim
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Old Apr 24, 2012, 04:45 PM
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Central California
Joined Jan 2010
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Thanks Guys

Thanks for the info guys.

It's so great to be able to ask a question here and get very good answers,or solutions to your questions.

After reading Dr. Drela's article,I think I just leave it alone.After all I'm not going to be stomping on a winch anyway.

Thanks again,

Eddie
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Old Apr 25, 2012, 08:58 AM
≡LSF8067≡
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Bedford, TX
Joined Oct 2007
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Quote:
Originally Posted by theghosttanker View Post
Maybe add some vertical grain sheet webbing glued to the front and rear of the spar, at least in the center section area
+1 on this.

Hi Eddie, I wouldn't worry the least as long as you do the above. I built my O3 with H instead of V grain shear webs for a cleaner fit and had some hard launches with no issues and very little flex in the wings.
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Old Apr 25, 2012, 07:24 PM
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Central California
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Quote:
Originally Posted by dwells View Post
+1 on this.

Hi Eddie, I wouldn't worry the least as long as you do the above. I built my O3 with H instead of V grain shear webs for a cleaner fit and had some hard launches with no issues and very little flex in the wings.
Hey DW,how's it going?

Now I'm really concerned. Does the H grain webs make it attractive to power poles? Sorry I couldn't resist.

How's your re-build of your Oly III?

Eddie
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Old Apr 26, 2012, 12:17 PM
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Bedford, TX
Joined Oct 2007
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Now that you have the dagger inserted between my ribs, go ahead and twist it, it couldn't hurt much more .

Fuse is 100%, straight and true, all recovered and shining like a new penny, working on the tail feathers. I'm going to clear the Sophisticated Lady build from my glass wing table and start the O3 wings next week. Will take me a while but at least I know how they're layed up.
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