Starting a new thread...

Hmm... I hadn't really considered a 3-part wing until just now! I remember seeing that video of the prototype Arc a long time ago but I never considered the benefits or build implications - thanks for prodding us in this direction Karl!

Benefits (as I see them):
Shorter wing components = easier to transport / store / handle / assemble.
It also removes a potential weak spot that is the aluminium root-join fittings and moves them outboard where the loads are much less, and maintains an unbroken carbon rod spar at the highest load area across the root. I like that a lot!
Problems & build implications (as I see them):
Trickier main spar central section to fabricate - remember, it's bent in the middle! Will the carbon rods bend enough?
Two sets of (lower load) wing connectors, not easily accessed without breaking the skin covering with some sort of access panel = disrupted airflow (maybe.)
Two join lines that need to be perfectly aligned/faired to maintain smooth air flow (on the flaperons also.)
Two extra ribs - fore and aft of the main spar and flaperon (extra weight, but no big deal.)
Extra hardware required to connect the three wing parts and two parts of each flaperon.
Spoiler and deployment arm will need to be redesigned (could this be completely replaced by a controllable drogue??
Pilot would definitely need to be under the wing, which would definitely mean a new pilot pod and control rod design!
Not sure my workshop will be long enough to accommodate building/aligning both the centre section and one wing tip section bolted together - it's barely 25 feet long!
Hmm... drat, now I'm going to have to think again!!

I do like the idea of shorter wings when disassembled though - much easier one-man handling.

The big issue to overcome with a 3-part wing is how best to join them and the flaperon halves, and what to do at the flaperon root. I suppose we could use a variation on the original root connection fitting, with the metal fittings slotting into cut-outs in the root of the wing end rib... if you get me! You would also need a very solid method of preventing the ends/edges of the ribs at the joins from moving or flexing, which might cause the flaperon parts to bind - and similarly on the trailing edge of the flaperon at the joins.

So, where do we split the wing parts? Thinking about handling and trailer storage, let's pick some arbitrary positions... if we split the wing into 1 x 22 foot long centre section and 2 x 11 foot wing ends, the centre 22 foot section will be a handfull to manage on your own but can be packed up in the trailer relatively easily (just two wing thicknesses.)

If we go for easier one-man handling, we could split the wing into roughly equal thirds = 14.6 feet per section = much more manageable, but trickier trailer packing Let's ignore the trailer problem for now!

In my design (run your own figures through my spreadsheet) the 1g load on the spar cap at rib #5 is 606.19lbs, down from 1265.92lbs at the wing root! At 8g those loads increase to 4849.56lbs, down from 10127.33lbs at the wing root. So, the loads are roughly half those experienced at the original root fittings, and the new fittings can be made smaller and lighter. However, even reducing the strength and weight of the carbon load transfer bars and metal fittings appropriately we will almost certainly be adding a little extra weight. I'll work out theexact wing connection fitting design later, but it would be neat if we could use strong pip pins rather than AN bolts to do the job (I'm not holding my breath on that!)

Rib #5 is 85.5+8.25 inches = 93.75" = 7.8 feet out from the wing root, so the centre section of the wing would end up at 15.625 feet long and the outer wings would each be 14.19 feet long.

Arguments and ideas please!

Phil.

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From: This email address is being protected from spambots. You need JavaScript enabled to view it. [This email address is being protected from spambots. You need JavaScript enabled to view it.] On Behalf Of KarlS
Sent: 20 March 2012 09:21
To: This email address is being protected from spambots. You need JavaScript enabled to view it.
Subject: [Carbondragonbuildersandpilots] Re: CDII -fuselage



I know you gentlemen are thinking of the 2 part wing with a center box but I would once again like to mention a 3 part perhaps folding wing.

Once again a 3 part wing eliminates the heavy most likely to fail highest stress part of the airframe as per Dieter Reich. I bet Ruppert wishes they stayed with the 3 part wing like their prototype.

Here's a photo for thought.

groups.yahoo.com/group/Carbondragonbuild...inal&start=1&dir=asc

Here's the spin characterists for the Arc and also the highest stress area failing.



Now that we are in the early stages of design concept I am putting the 3 piece wing up again for discussion.

Rupperts original 3 piece wing.

vimeo.com/29536897

Regards,

Karl