D/E Class Scissor-Flop RG

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TheAviator

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So, being my usual dumb self, I haven't built a single glider for NARAM yet. In a field of very challenging events, D-RG Free-Flight, might take the cake as far as complexity. So, naturally, I've whipped up a design in the past week and will be laser cutting it next week. (Smoke it if you've got it, right?)

This design is a massive scissor-flop glider. I decided to go that route because it puts lower stress on the wing during boost, thereby allowing me to have a larger wing made lighter. The specifications are as follows:

Wingspan: 42"
Wing Area: 336 sq. in.
Overall Length: ~44"
Engine Selection: Estes D12-3, E9-4; Aerotech D7, E7, and E6 w/ altimeter or R/C deploy, maybe AT E11-3 and F12-3.
Estimated Glide Weight: <150g (I hope)

I've attached two screencaps of the solid model, the first in boost configuration with a 4' long 1010 rail for size comparison. (Coincidentally, that is what I am using for a launch guide.) The second one shows the glider in glide mode.

Glide Config.jpg


Launch Config.jpg
 

TheAviator

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The wing is mostly done. Need to do some trailing edge work on the tips and attach and shape the leading edge. 42" of pure balsa, baby!

20160707_110805.jpg
 

burkefj

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Brian, interested to see your hinge/swivel mechanism...

Frank
 

TheAviator

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Pivot Mechanism.jpg

This is a simplified view of the pivot mechanism. The bearing tubes and shaft are made from nesting pieces of K&S aluminum tubing. The bearing tubes are glued into their respective parts and the rotation shaft is nested in the middle and allowed to float. The rotation shaft is then captured between the blind nut and the head of the nylon screw. The shaft is deliberately cut about 1/32" long to allow some room for the wing and fuselage to float relatively to each other. This means that the screw head puts no pressure on the wing while it is rotating and therefore the pivot is very low friction. I actually need to reinforce the anti-rotation pin because it is hitting the stop so hard!

The hinges are very simple: the wing tips are tape hinged to the center panel. I would really like to come up with a better way, but this works quite well.
 

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TangoJuliet

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Could you use Klett-style pinned hinges? Dubro and Great Planes both make them.
 

TheAviator

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The big bird flew this past Sunday at the MTMA launch in Aurora, OH. First two flights, the right wing panel didn't open, so I retrofitted some music wire band hooks further out on the wing, and it worked perfectly. The glider was far from perfectly trimmed, but I got well over a minute of glide on a C11-3.

DSC_4057 reduced.jpg


DSC_4061 reduced.jpg


DSC_4062 reduced.jpg


DSC_4102 reduced.jpg


DSC_4104 reduced.jpg
 

TangoJuliet

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Congratulations :clap:! Looks like the wing was beginning to swivel during boost as it cleared the launch rod. You might need to address that. It could be inhibiting a higher boost. And I think I would consider a little less dihedral... But that's just me.
 

burkefj

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I was wondering the same thing about the early wing rotation.
 

TheAviator

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Congratulations :clap:! Looks like the wing was beginning to swivel during boost as it cleared the launch rod. You might need to address that. It could be inhibiting a higher boost. And I think I would consider a little less dihedral... But that's just me.
I was wondering the same thing about the early wing rotation.
The "early" wing rotation was a function of the retrofit band hooks. I just pressed some music wire hooks into the top of the wing spar, but those hit the fuselage and prevented me from rotating the wing to vertical. It didn't really seem to affect the altitude that much on boost, which was just as straight. In any case, it was locked firmly in place, just not straight down the fuselage. The picture on the pad is the first flight, before I retrofit the hooks.

Regarding the dihedral, it was designed that way. Such a high angle ensures that the glider never even approaches a spiral dive, which is very important because the glider doesn't boost that high and it doesn't really have the altitude to slowly turn level. This is a trick I learned from Bob Parks on his Hummingbird glider.
 
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astronwolf

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The glider was far from perfectly trimmed, but I got well over a minute of glide on a C11-3.
I happened to be downrange looking for my S9A model and was distracted from my search by this glider. It had the sort of goofy dipping flight of a glider with a bit of stall, but it was not coming down quickly. I watched this glider approach me from up-wind and land in a tree. My thoughts were that Brian and Sean would have lost this glider if it was perfectly trimmed; very impressive performance from such a large glider that doesn't boost very high. Watch out for these guys! :clap:
 

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