Long EZ wing design / construction

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SpruceForest

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From pg. 19-6 of the plans:

"...(the lower wing skin is) two plies of unidirectional UND, each joint is butted not overlapped."

Not overlapped due to the obvious re: layup callout.

From pg. 19-7 of the plans:

" STEP 8 - Top Skin. Follow the instructions in step six with the following exceptions: Before..."

"...(the upper skin) has a third unidirectional, installed before the top BID reinforcement. This third UND ply extends from..."

In general, UND has very little strength or contribution to stiffness in layups across the long axis of the fabric (<5% of along-axis). I don't recall figuring in any contribution from cross-axis fibers on UND prepreg, but that work was circa 1989, so I hope that someone with more recent/deeper wet layup design methodology use can weigh in.
 
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wsimpso1

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The Uni cloth on the skins and shear webs are butt joined. Uni cloth is either being laid up in pairs (one at +45 degrees, next at -45) or lengthwise (0 degrees). We don't count on those cross threads for any stiffness ot strength.

Billski
 
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cblink.007

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From pg. 19-6 of the plans:

"...(the lower wing skin is) two plies of unidirectional UND, each joint is butted not overlapped."

Not overlapped due to the obvious re: layup callout.

From pg. 19-7 of the plans:

" STEP 8 - Top Skin. Follow the instructions in step six with the following exceptions: Before..."

"...(the upper skin) has a third unidirectional, installed before the top BID reinforcement. This third UND ply extends from..."

In general, UND has very little strength or contribution to stiffness in layups across the long axis of the fabric (<5% of along-axis). I don't recall figuring in any contribution from cross-axis fibers on UND prepreg, but that work was circa 1989, so I hope that someone with more recent/deeper wet layup design methodology use can weigh in.
You beat me to it!
 

SpruceForest

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OT but I will put in a pitch for the free Open-EZ plans and builder's manual available in the "Open-ez" topic at www.canardzone.com
Should have mentioned that... not sure if anyone has bitten off making the plans searchable, but it's pretty easy to check TOC and enjoy the late '70's vibe while browsing for the layup info. Also note that the Moldless Composite Sandwich Aircraft Construction general text on stuff like BID versus UND use, etc. is also covered in Section 1, Chapter 3 of the LongEZ plans.
 
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Rob de Bie

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I'm pretty sure that Rutan used UND in the wing skins specifically to avoid overlaps, that one would have to make if using BID. That would ruin aerodynamics.

Rob
 

speedracer

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The top layers are the same as the bottom except for a third layer that goes on at zero degrees the length of the wing, but not over the aileron cut out area and the length of the wing. I think this was to make it easier to balance the ailerons. The plans call for a 3/8" dia. steel rod in the Friese nose of the ailerons for balance. Lots of builders (including me) use a 7/16" dia. one to make balancing easier.
 
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wsimpso1

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I'm pretty sure that Rutan used UND in the wing skins specifically to avoid overlaps, that one would have to make if using BID. That would ruin aerodynamics.

Rob
Well, the aero can be as good, but it will require a minimum of about 3 more pounds of filler And more skill to avoid having wings with facets.

The other thing about using UNI cloth is it is 7 oz/ square yard while BID is 8.8 oz/ yard. That comes out to over 10 pounds difference for no pay value.

Plans say use +/- 45 UNI with butt joins. Plenty strong, suitably light, easier to build.

Billski
 
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