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Old Aug 25, 2011, 02:55 AM
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Originally Posted by eflightray View Post
What about the Hump ?, the plan is still available - http://www.myhobbystore.co.uk/product/15966/sf423--hump
I'm keen to try something new eflightray
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Old Aug 25, 2011, 02:56 AM
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Originally Posted by DT56 View Post

too much of a plank / deltoid lifeform for my liking!
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Old Aug 25, 2011, 02:57 AM
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anyway, no progress today...I've been out playing

flying wing aerobatics (2 min 0 sec)
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Old Aug 25, 2011, 04:54 AM
An itch?. Scratch build.
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Having looked through some of my old data on the Hump, perhaps not, unless you like cutting balsa, and cutting and cutting........

To think, I once cut out all those ribs..........not any more, getting too old and lazy.
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Old Aug 25, 2011, 09:36 PM
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Been CADing again ..

Had a thought about wing flutter stiffening.

Wondered if this is new or another Day Late Dollar and Short ideas.

Holes in ribs threaded with kevlar or CF instead of a whole layer of cloth.
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Old Aug 25, 2011, 09:57 PM
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sawman's Avatar
Louisiana
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Quote:
Originally Posted by eflightray View Post
Having looked through some of my old data on the Hump, perhaps not, unless you like cutting balsa, and cutting and cutting........

To think, I once cut out all those ribs..........not any more, getting too old and lazy.
Hmmm...how bout a foam version.
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Old Aug 25, 2011, 10:38 PM
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Quote:
Originally Posted by birdofplay View Post
Wondered if this is new or another Day Late Dollar and Short ideas.

Holes in ribs threaded with kevlar or CF instead of a whole layer of cloth.
Since stiffness increases with the cube of the distance between the fibers those fibers are best used on the skin. A D-tube composed of 45x45% cloth starting at a good strong web at the hing line, wrapping around the leading edge and back to the web would be a good start.

--Norm
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Old Aug 25, 2011, 10:42 PM
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CNC cutting and or Laser cutting is the answer to TODAYS rib issues !

Those Bias Weave rib holes I mentioned in my last post will be CNC cut !

Edwinzea: Would you like to run the numbers on that airfoil ?

I can provide a DXF or similar format
and if Profili is acting nice I think I might be able to do a dat.

Norm: I think I knew that instinctively, but, practically,
the clearance issue under any spars or LE stiffeners was where I started.

Surely the MID rib area could be taken out to almost the rib edges.

With ~ 40# strength PER THREAD depending on the chosen thread
My method seemed like a great way to get stiffness and save weight
and simplify construction and satisfy a creative whim.
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Last edited by birdofplay; Aug 25, 2011 at 10:48 PM.
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Old Aug 25, 2011, 11:11 PM
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I have also been considering stiffness issues. While building the Micro-Elli, I used 3x1 flat carbon strips, what if these were used vertically as sub-spars towards the trailing edge to stiffen it.
@eflightray: if you can get the ribs converted to electronic format, even a scan and cad trace, laser cutting will keep you building with wood for a long time
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Old Aug 25, 2011, 11:26 PM
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I have CAD and I have CNC so I am a busy boy :-)

When I twist a plastic covered wing by hand I note "Oil Caning" or wrinkling.

I assume that guys who "glass" ( CF Kevlar whatever) cover do so "on the bias"
to make the wing as resistant as possible to the wrinkling.

The "Kevlar THREADing" idea was simply a way to achieve the Bias strength
without having to do a heavy "glass" layup.

I like kevlar as it has very very low stretch ( if any).
And after placing a length it can easily be FIXED with a drop of CA.

Plus I have ~ 1000yd spool of the stuff ! courtesy of thethreadexchange.com
http://www.thethreadexchange.com/miv...=kevlar-thread

I use it for lots of model stuff.
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Old Aug 26, 2011, 05:41 AM
An itch?. Scratch build.
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To stiffen a built up wing, use the old method of diagonal ribs. Usually the rib from L.E. to spar is straight, but the ribs from spar to T.E. are set diagonal, or there are additional diagonal ribs.

The triangle is one of the strongest shapes.
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Old Aug 26, 2011, 10:37 AM
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Agreed, and I recall that you guys built some big bombers that way. :-)

But Developing and then cutting ribs is one of the largest parts of a build.
Diagonal ribs are more than just realignment of the originals.
I only have Profili and I havent seen the diagonal ribs option.
For me to do it right , I'd have to use CAD and lots of sectioning.

So my "outside the box" notion is just an attempt to simplify things.

This winters building season will see an attempt if only for my own satisfaction.
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Old Aug 26, 2011, 02:46 PM
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Quote:
Originally Posted by eflightray View Post
The triangle is one of the strongest shapes.
Triangles are the only rigid shapes. Think about polygons with a single pin at each corner. Any shape with more than three sides will collapse when a load is applied because the bars can rotate around the pins without actually failing whereas the triangles are locked up and will hold there shape until a bar fails under compression or a pin shears. When you glue the corners of a polygon with more than 3 sides you're relying on the shear strength of the glue to hold the shape of the polygon and the bending strength of the bars. By putting a diagonal brace between two ribs you are transforming the space from a rectangle into two triangles. You can also break up that rectangle into four triangles by running wires diagonally across from corner to corner. Many wooden full size planes have two steel cables running from root to tip in a zigzag pattern forming an X in each rib bay. They're called the "drag, anti-drag wires" but they actually help a lot with torsion too.
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Old Aug 26, 2011, 05:29 PM
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Some examples of the drag / anti-drag wires in a Pitts wing.
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Old Aug 26, 2011, 06:03 PM
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I am WITH YOU 100%, DT56 & Norm !

But these Flying wings seem to NEED lots of TWIST compensation in their builds.
Mostly because they have a variable Washout from root to tip.
Get em going lickity split ( over speed) and the tips fight with the root.
Then you have wing flutter that ends in wing failure and RE-KIT !

So the Bracing has to be at/near the rib surfaces and/or top to bottom rib runs as well.
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