Folding Flying Wing and Deployable Glider development project from 2010-2011

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georgegassaway

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This is a story of a contest glider project that began in 2010, to try to develop a very competitive design to fly at the 2012 World SpaceModeling Championships (WSMC). As such, I did not publicize the project at the time, not wanting other countries to perhaps copy the design for 2012. Recently I was going thru old computer files, and realized I ought to finally document it, And, to create a video.

In some ways this will be like a "build thread" that is about 10 years after the fact.

The project began as this......


And led to THIS:


I’ll briefly mention that there have been gliders that fold up to fit inside of model rockets for a long time. There are Flex-wing (Rogallo) type gliders, but I’m focusing on solid winged gliders. In the May 1976 issue of the NAR’s Model Rocketeer newsletter, there was a plan for the “Beaver”, a swing-wing canard glider that fit inside of a BT-60 body tube. It was designed by Steve Behrends for E & F power Boost Glide, as in those days there were very few successful E & F gliders of any design. There were some folding gliders before his but that one stuck out as a sort of practical model, for that power range.

Folding flying wings have been experimented with for number of years. I recall at least one article in the Apogee newsletter about them. But more in the sense of either theoretical, or tested out but didn’t perform well. I mean, I'm sure some have done them, but do not recall much about successful ones (which should have shown up at contests if they worked well enough).

I tried a flying wing for 1/4A Boost Glide many years ago, in a 30mm body tube, but it had terrible yaw stability problems, so I gave up on it. (I’ll cover it later).

At the 2010 WSMC in Slovakia, US Junior Team member Caleb Boe flew a flying wing in the S4A (Boost Glide) event. It fit inside of a 40mm FAI body tube. It had mixed success, but showed some promise. So that got me to thinking,

After getting home, I decided to try to work up a flying wing that would be bigger and try to solve some other issues. The minimum diameter for FAI events like Parachute (S3A), Streamer (S6A), and Helicopter (S9A) duration events is 40mm. But I quickly decided that the resulting glider would be too small, at least in wing chord, so I ended up going for a 50mm diameter. Well, in the chicken or the egg sense, I decided on a 1-5/8” wing chord, and allowing for the total thickness of the wings and “stuff” sandwiched in between, that 50mm was about right.

Well, not exactly 50mm. I had some paper tubes 2” in diameter that I could use as mandrels for doing a one-wrap Kapton tube over, so that is what defined the final diameter. Also, I did not want to turn a balsa mandrel for the nose, and found that the Estes “Space Ship One” kit’s 2” diameter nose cone would be a nice shape as a master to vac-form very lightweight nose cones from. The bodies used .02" Kapton for the cylindrical section (one wrap plus 1/4" overlap), and a paper tailcone. For WSMC boosters, I'd likely have come up with a mandrel to make fiberglass tailcones. But paper was OKJ for testing, for a few flights. Below, a booster prepped for flight with a Flying Wing inside.



I got to thinking more on how to go about solving the Flying Wing yaw problem, and how to get a bigger more efficient glider out of the available tube volume. I’d had a lot of success with FAI helicopter models that used flop-wing type folding blades, which doubled their spans once deployed. So, I planned on doing it as a flop-wing flying wing. As with the copter models, the hinges for the outer flop panels were simply small strips of “Skyloft” covering to act as hinges, CA’ed along the bottom of the wings (ends of the balsa rubbed with candle wax to keep CA from gluing the balsa. Krevin Kuczek came up with the Skyloft hinges and wax trick). Those are a great way to do simple thin light rugged-enough hinges to fold 180 degrees.

But the center section was different. It needed to fold "UP", on the top fo the airfoil. So, the model needed a mechanical hinge that could fold 180 degrees. There were no practical model plane hinges for my needs. So, I designed my own “door hinge” type of hinge master, made out of styrene sheet and short pieces of styrene tubing. Used that to make a 2-piece RTV mold, and cast copies. This worked out great and was the key to the mechanical success. Also, when folded “up” like that, the bottom area of the hinge was spread apart, stretching rubber bands for good leverage, to be able to easily deploy the center section. Below is an image of the RTV mold, with one cast hinge half still in one of the mold halves. And to the right, a second cast hinge half, before the "flashing" was trimmed away and before removing the 1/16" rod (which had mold release applied) that cast the holes.



I added elevons to the tips as with typical flying wings. But it had two problems in glide. For one, still the yaw problem, very bad. Also it seemed like maybe pitch stability too, on the rare times it wasn’t yawing too much to tell. So, it seemed like I needed to add folding rudders to the wingtips. Then it occurred to me….no they did not need to fold. They could be half-round, just smaller than the inside radius of the body tube, and glued to the wingtips. I tried that, and that solved the yaw problem.

The pitch problem persisted though. I did not want to mess around with fancy (or even not-fancy) reflexed airfoils (and the up-elevons near the tips provided some of that effect anyway). At one point, I temporarily glued a fixed canard up front to see if that solved it. If so, I’d work out the fold method later. But that did not solve it. So it was flaky for awhile. But eventually I ran across a tweak the helped. I accidentally had the flop-panel hinges a bit “off”, where the outer panels were not flat compared to the main inboard panels. They extended up a bit with a bit more dihedral. But it was not the dihedral itself. It was the fact that the hingelines were at 90 degrees to the wings, which for the swept-back wing it meant that the outer dihedral caused the whole outer panels to be at a bit lower angle of attack to the airflow than the inner main wing. So, when coming close to a stall, the forward inner panels would stall first, like a canard does. And that made things better.

The trim was still a bit flaky, but acceptable to fly with.

Here is a composite image showing the completed Flying Wing, deployed, being folded, and folded for boost.

A close-up set of folded views. Note the rounded rudders, main hinge, and rubber bands to deploy the main wing.


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georgegassaway

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The first test boosts were at a launch in October 2010. I used 1/2A3-2T power, without a piston, to keep the altitudes low and reduce the chances of losing the glider.


The boosts and ejections went well. A common issue was losing about 30 feet of altitude at times before transitioning into a glide. First flight stalled a lot, I got in some better trim for other flights.



Did more testing at a November launch. And again it worked pretty well. Though the glide was always a bit flaky, it would be fine then start stalling a bit. Or “hunting” a bit.


So, I had something that worked, but was not satisfied with the glide trim and handling issues.

I tried a couple of quick "fixed" modification to see if adding a canard might help. Nope, not really. Adding a tail to the back showed some promise. But the swept wings made the tail less effective, the wings needed to be straight. And this was about to get a lot trickier....


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georgegassaway

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Using the Flying Wing's proven fold methods, I wanted to make a more conventional glider, with straight (not swept) wings, a fuselage, with a stabilizer and rudder in the tail. For better glide trim, and it should glide better than a flying wing.

In 2002, I had made an attempt at a folding glider, which just turned out terribly. I’ll document it later. But I learned from that dead-end design, a lot of things to avoid.

First, I made a non-folding prototype, 36" wingspan, to check out the glide characteristics. And to see if a .06" graphite boom was stiff enough. It glided pretty nicely. I had already started figuring out how to get it to fold.


The key to that was figuring out how the heck to do a folding fuselage, that could also fold up the tail. Anything I thought of that involved the “obvious” idea for the fuselage to fold vertically, either down or up, ran into problems being incorporated with folding up the wings. The best place to store the stabilizer and tail, plus fuselage, was sandwiched inside of the folded main wings. Which ended up like this eventually:



But how to get there?

The solution to the fuselage fold was to fold it sideways, not vertically. That way, the hinges for the fuselage could be on top of the deployed wing, therefore inside of the wings when folded. A new main wing hinge mold was created that allowed extra space between the folded wings, to store them.

One of the hinges needed for the fuselage was a mid-aft hinge. I made a prototype out of 3/32" brass "U" channel and 1/8" brass square tubing cut into a U. I had done hinges like that for a sort of flop-wing flex-wing in 1987, which worked welll. But were a PITA to make, using a moto-tool cut-off wheel to "sculpt" the parts.

After making one for this project, I weighed it. It was heavier than I wanted.


Which...was sort of a good thing, actually. I decided to try casting the hinges instead. Which would not only be lighter, but easier than hand-sculpting little brass pieces.

I am not sure if I made master parts from brass that had some plastic filler pieces added, or if I made them up 100% from styrene strips. It’s been a long time, and I do not have the masters for anything but the main wing hinge. From those master parts, I made RTV rubber molds to cast the parts, sometimes 2-piece molds. For at least one part, after casting it I used a moto-tool grinding bit to remove some of it in a curved shape, to remove mass (more mass in back means more noseweight to counter it). Here's an example of some of the mold work and parts. The 1/16" music wire rods had mold release applied, to allow them to be twisted and pulled out after curing. That was the only way to cast properly aligned holes into the parts.


All the cast parts in the photo below, clockwise from top left: Band hook on graphite rod, Main wing hinge, Tail section hinge, mid-aft fuselage hinge, and "K" hinge (to mount at wing center) that pivots both the front and rear fuselage.


The fuselage was .06” graphite rod. It was just stiff enough to allow the tail to work properly. Assuming the hinges did not have any slop.

The image below, without the orthodontal bands, shows how the fuselage cast hinges moved laterally, none vertically


The tail needed a double fold, to be 90 degrees to the fuselage, and to be FLAT. The 90 degrees was solved by using a sideways hinge to allow the stabilizer to rotate 90 degrees.

That left the problem with the rudder. A “normal” glider has one rudder in the center. This was no normal glider. :) So I used the Flat Cat and B-25 twin rudder idea….but without a second rudder. So in other words, I moved the normal rudder location to one tip of the stabilizer. If this was an R/C model plane, that might have mattered some (or a lot if it was rocket boosted). For a free-flight glider meant to be intentionally trimmed to glide in a circle, no big deal. As long as it had enough rudder area, which it did. And made this crazy-complex glider look even more unusual.


Some more hinge pics. Rotating tail, and mid-aft fuselage hinges.


Mid-aft fuselage hinge with band attached.


Main wing hinge with "K" hinge added. Note hole in facing K hinge for forward fuselage rod to be glued into.



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georgegassaway

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So, by January 2011, I had a prototype ready to fly.



It worked pretty well, though the first flight one outer panel did not deploy. On the good flights, it fell farther before transitioning into a glide than the flying wing. But on full A power using a piston, it would be so high that the extra loss of initial altitude would not be too bad. I mostly tested it on 1/2A power though, to not lose it during glide.

So... the boosters. Pretty much a scaled-up 40mm FAI model, to 50mm, using a Kapton main body and paper tailcone. With vac-formed nose cones and hot wire-cut foam plugs for ejection piston/plugs and nose cone bases.

But, the FAI rules can "get ya" easily. Other than wadding or "recovery protectors" every part has to eihter have a deployed chute, or streamer, or glide. Tumble is a DQ. "featherweight" descent is a DQ. I did NOT want any shock cord anywhere in the glider compartment, because inevitably the cord would tangle with the glider or cause other problems. So, the ejection piston/plug had a shock cord in its base, only, (kevlar cord, anchored in the tailcone) and a piece of .020" music wire sticking upwards, with a streamer at the end of it. I had to do that because the plug itself would not get ejected out of the body, I learned that in the first Flying Wing tests. So, the photo below documents a good streamer deploy after a flight. Now, there was a chance that the folded streamer could snag on the glider's flop-wing rubber band hooks. So, I added a strip of paper between the glider and the streamer, with the paper folded under the glider, to keep the streamer from tangling. Never had a problem with the music wire deployed streamer & paper strip protector.


Now, the nose cone. A 4 gram 2" vacform nose cone tumbling at 5 mph....will get DQ'ed by FAI for not having a recovery device. So, it too needed a streamer. With the Flying Wing, I had stored a streamer above the glider. But on an early flight of the Deployable Glider, a streamer got tangled at ejection. So, I had to redesign. As with the "Spooler" pop-pods, I changed the nose cone base into a spooler too, two foam discs glued to a smaller diameter Kapton tube core, to allow a narrow Tyvek streamer to be rolled up inside. So at ejection, the streamer would unspool, but by then the glider was long past it. That system worked well. You can see it, and the music wire streamer extensions on the foam plugs, in the photo below of two boosters built to use at the 2011 US Team selection flyoffs.



If I made the US Team with it, my plan was to either add a dethermalizer or tiny electronic Walston-like tracker to the nose. For the normal glide tests, I just used clay noseweight, or a penny glued to a sliding tube (simulating a fixed mass of a DT device or tracker). But I did test out the method for dethermalizing, to make it come down quickly without damaging itself. The idea was for the DT timer to cause the forward fuselage’s deployment band to be released, allowing a weaker band with less leverage to rotate the front fuselage 90 degrees towards a wingtip. That would move the glide CG back, and also make the model unbalanced towards that side of the wing, to spiral down. So, I did on A test, no piston, with the forward fuselage taped to a the left main wing, to simulate the DT mode. And it spiraled into the ground. A bit faster than I expected, but not bad, and no damage. With further development, if I used a DT, maybe i'd have limited that DT deploy to 45 degrees or so rather than 90 (to get less of a spiral descent that was not as fast as the one test I did).

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georgegassaway

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I should note that along the way of the project, I was e-mailing with Bob Parks about the project. Part of the inspiration for this deployable glider, was Bob’s work with Aurora Flight Sciences Corporation, on the Mars Flyer, also known as ARES (before the short-lived Shuttle Derived ARES rockets). It would be an “airplane” sent to Mars, to fly in the Mars atmosphere for awhile, gathering data. To get there, it needed to fold up very small to fit inside of an aeroshell to survive the extreme entry into the Martian atmosphere. The photo below shows a half-size test version that was folded up and drop-tested from a balloon from above 100,000 feet to test for deployment and flight.



Anyway, Bob had this really neat idea. The folded cross-section of my glider was rectangular, not a square. So, it did not need a circular tube. It could fit into an oval-shaped tube, saving boosted mass and reducing drag. The prototype body (Thin Kapton and paper tailcone) was easy enough to force to be oval. But the nose cone would be a mess to try to hand-carve. So, Bob offered to use his CNC milling machine to mill an oval-shaped nose master out of wood. And also provided a couple of laser-cut plywood ovals I could use as masters for using a homemade hot-wire cutter to cut out oval foam plugs as both piston type ejection plugs and also as the base of vacuum formed nose cones.

Below, 40mm round nose at left, two red "43" mm oval noses, and CNC milled nose pattern at right. The white tube at the base is for a hole running all the way to the tip. A small hose was attached to it, after vac-forming, and a can of "air" for dusting keyboards & electronics was used to pressurize it and push the fragile vac-formed nose away.



Before Bob machined that, I determined that a tube with a “round” diameter of 43mm would be optimum (well, the mandrel I used for creating the Kapton tube was simply Estes BT-60. And the resulting Kapton tube's diameter would be close to 43mm). . Once squashed into an oval, the folded glider would fit with adequate room to spare. By going from 50mm to a “43” mm forced oval, that would reduce the Kapton main body mass by 14 percent. More importantly, that would reduce drag by 26%, at least for cross-sectional area. One compromise was to go with 4 fins, 2 smaller ones for the thin axis, and 2 bigger ones for the wide axis, a bit of a drag increase. But I was not going to mess around with how to do it with 3 fins, at least not for early testing (Perhaps 3 fins arranged 135/90/135 would have worked out, or something along those lines. But that was something to tweak for later on, the perfect fin configuration was not important at that point in the project).

First prototype oval body, with a printed paper main body to show up the contours of the oval body. Used a cast thin oval shaped bulkhead to shape the upper end of the tailcone.



Here is a composite photo showing two views of the oval 43 body with a Kapton main tube, with blue foam glider simulator inside.



So at a couple of launches, I got into doing tests of the “43mm” oval booster, and also the 50 mm (2”) booster. Most of those tests did not risk a glider in them, I used a block of thick blue foam about the same shape and thickness of the folded gliders, with a bit of weight added to equal their mass.

Testing of the 43mm oval body showed a problem I had detected in workshop testing, when pressurizing the tube for simulated ejection. Pressure vessels like to be round, not oval. The Kapton tube was very flimsy, so pressure made it want to become round. Sometimes the oval piston plug jammed inside the Kapton tube after moving a few inches as the tube pressurized into an oval. The flight testing showed this to be a serious problem on two flights, both jammed and crashed (fortunately a glider was not onboard, the blue foam was).



I had worked out a “plan B” for that. Running some 14mm tubing from the bottom of the tailcone, up thru a cast oval bulkhead at the top of the tailcone. Then I made up a piston ejection assembly that was mostly 13mm tubing with an almost oval plywood top piece to push onto the folded glider. At ejection, the piston assembly would push the glider out, to get it moving, before the ejection gases escaped from the 14mm section to then try to make the tube round.

That had two or three problems. For one, it added more mass, more than the savings in going to 43mm. And being such a confined volume, a MUCH harder kick by the ejection charge to force everything out with many times more force. And that risked something bursting during ejection, or extreme acceleration damage to the glider. It just did not work out enough for me to ever feel comfortable with.

So, in the end, the 43mm oval body booster idea was abandoned. It was a really neat idea, though.

Bonus: Bob's CNC machine milling the oval nose cone pattern:

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georgegassaway

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Teaser from before, showing Flying Wing glide:

Now, resuming from where I left off...

Testing for the 50mm model, I used a piston launcher as it would for contest flying. I was testing that it held together on boost, and to find out how high it would go. I used a blue foma glider mass simulator and a Quest Altimeter, for the same liftoff mass as with the glider. IIRC it boosted about 250 feet. This was with A3 motors of about 2.1 N-sec. The 10mm Czech motors to be used at the WSMC would be right at about 2.5 N-sec, so the model was likely to fly close to 300 feet (even more if I used a lighter mass fiberglass tailcone).


I later did some indoor glide tests. At a very large stage in at an entertertainment center / small TV-movie stage studio that I had access to on occasion at work. I set up a vertical stand with PVC pipe, with black tape every foot up, and set up a video camera along the side to record straight-ahead hand-level throws. I determined the glide descent rate for the deployable glider to be about 1.42 feet per second. The flying wing did not glide quite as well, but respectable (I do not recall the value, and of at least 5 video files i had, I could only find the last one which did not have the Flying Wing on it). There's some clips of the indoor testing in the video I'll post.


So if the glider boosted to 300 feet, and lost 30 feet before transition (reaching 270 feet), in neutral air (no lift, no sink), with a glider descent rate of 1.42 feet per second, it would fly for 190 seconds. The MAX was 180 seconds! So, this is why I was so excited about the prospects of this model. The contests always depend a lot on picking air, for thermals, and avoiding bad air. But even at that, the better the model can fly, the better it can do. And sometimes there are drab overcast calm-ish days that do turn into nothing but a "Dead air" pure performance game.

Getting ready for NARAM-53 and the US Team selection flyoffs in 2011, I built two more deployable glider models. I gave the outer panels a lot more dihedral, to allow for trimming the glide in wide flat circles better. I also had gotten a gram scale accurate to 1/100 gram, rather than 1/10 gram as I had used before. I documented the masses of the parts a lot, sometimes by writing on them, and sometimes by photos of the parts on the scale. I ended up going down a rabbit hole of sanding the 3/32” balsa wings to be lighter (and a better airfoil), and made the 3rd model’s wings even lighter with more sanding. Below, models 3, 2, and 1 (prototype) from left to right.



I put in a lot of time trimming them and finding out the best way to get them to circle flat, without a risk of spiraling in.



At the US team flyoffs at NARAM in 2011, I used model #3. (Photos by Chris Taylor (Nerys on Youtube)


It boosted nicely, ejected fine….but an outer wing panel did not deploy.

I had not used enough orthodontal band force, should have used two bands. The model actually glided, but in a slow spiral. So it qualified but flew for less than a minute.


Second flight, the wings deployed fine. But the model deployed nose-down, and the wings fluttered aerodynamically. It was due to two things. One, sanding those wings to make them lighter…. they were not as stiff as model #1 (the prototype). And, the dihedral angle mid-way out caused a lever arm that would make any tendency to flutter worse. If it had a pure “Vee” dihedral from the center (as the prototype had), and no dihedral for the outer panels, I do not think it would have fluttered that easily. My eventual fix for that would be to keep the outer wing dihedral, and still sand a good airfoil, but to be sure the inboard main wings were stiffer (such as Japanese tissue vacuum-bagged to the inboard panels, as I had done with Flop-Rotor FAI helicopter models).

The good thing is that after losing about 2/3 to 3/4 of its altitude, it finally pulled out and into a glide. it had a nice glide after that, but not very long.

Flight 3, I went with Model #1, the prototype. Launched, deployed, got into a thermal, and flew away, for a max time of 3 minutes. (there is great slo-mo video shot by Chris Taylor, that is in my video. But I only had a low-res version).


I missed making the US team by something like 23 seconds, 4th place. It was agonizing.

I showed those models to those who did make the team. I offered to let them borrow the two models I had left as examples, and provide them with the unique cast parts for the hinges and info on how to build them. One of them did take one home but decided to go with something else instead (and yes he did return the model).

And that was the last time that one of the Deployable glider flew. The FAI rules changed in 2013 to not allow ANYTHING form an S4 glider modle to come off. So, even though they still call it "Boost" Glide, it really is "Rocket Glide" now. So, the deployable gliders and Flying Wing models were not legal to fly in S4 after 2012.

But that's not the end of the story......

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georgegassaway

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2012 - The Flying Wings strike back!

There was an FAI World Cup event held in June 2012 . The Great Lakes Cup, near Chicago. Pat Butler was the CD.

I flew the Flying Wings in the S4A event. I built two new models, as I had only built one prototype Flying Wing before moving on to the straight winged Deployable glider. But the Flying Wings are actually not hard to build, two can be built in a day, if you have the main wing hinges.



Had 91 seconds and two maxes (thermalled away) to win the event easily.
(no video from there, and the images below are from 2010 testing).





So, some vindication for the project.

But even then, it was not over.

Alyssa Stenberg was on the US Junior Team for the 2012 WSMC. She was on the S4A team and she built two clones of one of my Flying Wing gliders, and clones of the 50mm booster. Here she is checking in her models, and getting ready to launch one of the flights (using a piston-tower combo). She used Estes A3-4T's rather than the 10mm more powerful Czech motors that were harder to ignite.


It was a very windy cold day. The glide trim was off, hard to trim in that wind. But they all glided.


She ended up 26th out of 48 Junior fliers. At least she had three qualfiied flights, her other two teammates DQ’ed all flights and had zero scores.

She placed higher than the US Senior team did in S4A, they flew a different day in good low-wind thermal weather (best US SR was 31st).

So that was the last time any of those gliders flew, no longer legal for FAI. THey certainly can be flown in NAR Boost Glide events. But the niche for them is A power. Too heavy to boost and transiton well for 1/2A or less. And at B power, a good performance R/C model is usually a better option. Although, at NARAM-60, I did take a Flying Wing for A Boost Glide, just in case there was a strategic reason to go with it. But due to light lift I went with a nice old foam-wing glider, that hit a thermal and got in a really nice score. So I ended up using an R/C A Rocket Glider to fly for a return flight of about a minute.

Maybe I'll try Flying Wings again sometime. And just possibly the Deployable Glider, but I no longer have the master parts & molds for the fuselage hinges. And was "spooked" by the 2011 flyoffs.

Why did I not document this as I was working on it in 2010 and 2011? Simple. If you are trying to develop a "world beater" design, you do not publicize it for the world to copy it and perhaps beat you with. Would have really sucked, if I had made the 2012 team, to show up there and find I was competing against my own design. And after that, I had sort of "moved on" with other things. It's still a very bittersweet thing. But having run across photos and movies of it recently, I decided I ought to post it before it was totally lost.

In a game of "What if" I had made the team for 2012, I would have done a lot more test flying later to work out the bugs that happened at the 2011 flyoffs, and no doubt would have found some other things crop up to tweak.

Same was true of the Flop-Rotor S9 helicopter design process. I'd made the team in 2001 with a model I'd not tested much, but got on the team. Then as I improved it and made more tests in 2002....things cropped up requiring a little fix here and there. Ending up with a total of 70 flights in a 6 weeks period (flown at a local site after sunrise when winds were very low). I had two maxes at the 2002 WSMC, one more would have meant gold, and the design wss maxing in dead air. Then on flight 3 the rotor section slid out at burnout & deployed (safely), reducing the altitude so it did not max and I got 4th. The US Team got 4th. Kevin Kuczek, who had made a similar design, and we cross-posted design tweak ideas and improvements back and forth, got the silver medal in 2002. And in 2008, using my 2002 S9 copter models, I got a bronze medal thanks to all that 2001-2002 work (and better luck). Below, one of the 2002 dawn test sessions



So this is why such deep-dive contest designs are sometimes done, they can pay off great if they perform as intended and are reliable enough (reliable being the key). This S4A glider project did not pay off as much as I'd hoped.

OK, so earlier I referred to a 2001 attempt at a folding glider. Here it is in all of its ugly:

I ended up making a longer booster to fit it into than shown below, the orange one is a normal length fiberglass 40mm body.

That tail... the horror...


Yes, it glided as bad as it looked. The folding chord wings had issues with trim inconsistency. The stab and rudder were like stubby flop-wings, they fit inside a 40mm tube, but did not provide as much horizontal stab area as it needed, and not much for the rudder either. The only good thing was the common shared pivot point which Steve Behrends' "Beaver" design had used so long ago. But even that required a kludge to get any dihedral for it, a "flop wing" type of hinge near the root of the right wing, though it only had to move upwards 15 degrees or so. The only fold for the fuselage was the front section, which had a 180 degree pivot just under the swing wing pivots. I knew it sucked. The trimming process sucked. The trim varied, in part from the folding chord wing not deploying exactly 100% the same after being folded. The too-small horizontal tail sucked. I did boost it once, if for no other reason than to say I did fly it (so, now I've said it). It did deploy everything, but dived into the ground. But it did serve a purpose, mostly nearly everything about it was a dead-end, something to not repeat with the 2010-2011 project.

Not wanting to end this on that ugly glider, now a couple of pretty flexwing photos. I've been doing those since 1974, maybe 1973 (I did not invent them of course, but learned quickly how to build and fly them well)



OK, well, this is what many of you have been waiting for. An 11 minute video. There is not as much video footage available as I hoped there was, but definitely some good stuff. And a few are lo-res. And some is filled in with photos and text of some of the things you've already read here.


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mbeels

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Oh wow, very cool. Amazing fabrication work, and interesting to see what worked for you (and what didn't!).
 

Amsterdam

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Seeing the fuselage fold up made my jaw drop. Absolutely wild! the time you spent thinking about this is obvious, very well thought out and executed.
 

georgegassaway

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Be SURE to check messages #6 and #7, which have been massively updated since the last time you saw them (were short placeholders).

Adding this copied from the bottom of my last post, as a "bump" for those who might miss it:

OK, well, this is what many of you have been waiting for. An 11 minute video. There is not as much video footage available as I hoped there was. And a few are lo-res. And some is filled in with photos and text of some of the things you've already read here.

 
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B_RadB

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Fascinating story and documentation of design and development process. Thanks for sharing George!
 

neil_w

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Thanks for taking the time to write this up, really interesting.
 

georgegassaway

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I finally found a pic of my first try at a folding Flying Wing type glider. May, 2003. For the 1/4A Boost Glide event at NARAM that year.



The intended booster was a 30mm body tube. But the glider had no yaw stability. Even though there are rudderless flying wings. If I had not tapered the tips, and had thought of the half-round tip rudders to fit inside the body, this might have ended a lot differently.

Instead, I used my version of a "Fish N' Chips" glider. Which IIRC took 2nd place at NARAM.
 
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