Holverson Swinger RG – resurrection of a nostalgic classic

[Rktman]

Took off a tiny bit too much with the dremel. A little shimming with some 1/32” ply got things aligned right, although I do notice a little weirdness—the piston tends to “roll” in the motor tube, allowing the control wire to move a bit right or left so that both wings can move up to 1” left or right in the locked back position. Equalizing the tension on both sides of the rubber band seems to ameliorate the problem though, and I’m guessing air pressure and drag will help keep them pinned back.

Happily no adjustment was needed in the wing’s glide position, they both deploy at an exact 90°.


As extra insurance I hardened off the wing root and control rod clamp areas of the wings with CA. The forward wing root is an especially high-stress area that I wanted to ensure wouldn’t split when the wings slam up against the fuse when they deploy.

Just need one final coat of dope to protect things from all the balsa-warping humidity here and getting the CG where it needs to be, and I think I can wrap things up.

 

[Rktman]

Both wings turned out virtually identical in weight (16.2g & 16.3g), something which has never happened before (there’s usually a more pronounced weight difference). So I may either go the clay route or slightly warp the rudder to induce a turn. What I’m hoping is that the stacked wings might induce a turn naturally, so I won’t have to add any wingtip weight or mess with the rudder.

The CG should fall 9/16” ahead of the rear edge of the wing support disk. Fortunately all it needed to balance was a less than BB-sized lump of clay on the aft end, though I may still have to make small adjustments after some trimming glides.

 

[Rktman]

Done! Adding the small wire nut feels like adding the cherry on top. Happy to have this Blast from the Past replica. I feel like John Hammond, the billionaire guy in Jurassic Park that brought back extinct dinos—except in this case it’s a cool but extinct glider.


Quite happy with the way it turned out. It’s definitely unique looking and unlike any other glider kit currently out there. At about 23” in length and 89.37g (3.15oz) in weight with an expended engine casing in place, it may not be a contender for competition, but with a C6-3 it should put in a flight time of over a minute, which is plenty enough for a sport glider that I really don’t want to lose or have to hike a long way to retrieve.
Hopefully I can give it its inaugural flight in mid-February at our club launch, weather permitting.

 

[kuririn]

Nice job!

 

[Rktman]

Nice job!

Appreciate that! Always wanted one of these, glad I got to scratch that itch.

 

[K'Tesh]

Beautiful Job!!! I can't wait to get one for myself.

 

[Rktman]

Beautiful Job!!! I can't wait to get one for myself.

Thanks! It'll be a great addition to your fleet and different enough to be a real attention-getter at any launch. Would be great to see a pic of yours here in this thread when you're done.

 

[Crawf56]

Good hunting!

 

[Rktman]

Yup I think she's going to be a big field flier only.

 

[Massrokit]

Rktman have you flown your Swinger yet?

 

[Rktman]

Rktman have you flown your Swinger yet?

There's a club that uses a 38,000+ acre farm near the coast. Will launch with them once the crops are havested sometime in late August/early September. Hopefully I'll be able to snag some video.

 

[BABAR]

Hope you have better fortune than review here!

http://archive.rocketreviews.com/reviews/all/oop_fr_swinger.shtml


“Summary:
If someone buys you this kit, then build it as guided above but do not install the motor. Take the Swinger out to your flying field and them jump up and down on it. This way you'll still have a smashed Swinger, but you won't waste a motor.”

End of quote


Given yours is balsa rather than plastic, you may he better luck

Only worse review I have seen is the Cosmos Mariner

http://archive.rocketreviews.com/reviews/all/est_cosmo_mariner.shtml

 

[Rktman]

Hope you have better fortune than review here!

http://archive.rocketreviews.com/reviews/all/oop_fr_swinger.shtml


“Summary:
If someone buys you this kit, then build it as guided above but do not install the motor. Take the Swinger out to your flying field and them jump up and down on it. This way you'll still have a smashed Swinger, but you won't waste a motor.”

End of quote


Given yours is balsa rather than plastic, you may he better luck

Only worse review I have seen is the Cosmos Mariner

http://archive.rocketreviews.com/reviews/all/est_cosmo_mariner.shtml

Haha yeah I've seen those reviews and the Swinger should never have been offered as a foam version. Too flimsy. At least the fuselage should have been balsa. The impact of those wings swinging forward is pretty extreme. And I've never heard good things about the Mariner. Probably too heavy to glide decently.

Actually the Centuri Mach 10 is even worse; it's glide is more a controlled (barely) fall, but only after it performs its always reliable head-removing loop. But I knew that going in and built it for fun knowing it has to be boosted high enough not to risk taking out someone's eye.

I'm going to upscale it and redesign it without the offset motor tube and the draggy air brake of a stab that causes the looping. Should make for a fast sink rate but otherwise fairly decent glider.

 

[cwbullet]

Nostalgic and sometimes dangerous in flight.

 

[Rktman]

Nostalgic and sometimes dangerous in flight.

Strange that they would kits something like that, especially since the simple build seems to have been been targeted at kids and beginner level fliers.

 

[burkefj]

Thats how i designed my rc kit versions of the mach 10, but you may still need some sort of pop up elevon for glide to get some angle of attack...and it may still want to pitch toward the tail without some offset thrustline.

Haha yeah I've seen those reviews and the Swinger should never have been offered as a foam version. Too flimsy. At least the fuselage should have been balsa. The impact of those wings swinging forward is pretty extreme. And I've never heard good things about the Mariner. Probably too heavy to glide decently.

Actually the Centuri Mach 10 is even worse; it's glide is more a controlled (barely) fall, but only after it performs its always reliable head-removing loop. But I knew that going in and built it for fun knowing it has to be boosted high enough not to risk taking out someone's eye.

I'm going to upscale it and redesign it without the offset motor tube and the draggy air brake of a stab that causes the looping. Should make for a fast sink rate but otherwise fairly decent glider.

 

[Rktman]

Thats how i designed my rc kit versions of the mach 10, but you may still need some sort of pop up elevon for glide to get some angle of attack...and it may still want to pitch toward the tail without some offset thrustline.

I was thinking of mounting the stab on top of the tail with zero decalage but with elastic-actuated flaps that would pop up at apogee. I saw a photo posted somewhere with that setup and the builder claimed that the air pressure kept tbe flaps pinned flat during boost and once the glider slowed at apogee, the elastic (though weak) was still strong enough to pull the flaps up. Do you think that's even possible? If not I'll have to think of another (non-RC) way to do it.

 

[burkefj]

yeah that's what I was thinking would work but you may want to just do some glide tests and see if it if you can get a glide without anything

 

[Massrokit]

It is now Oct. Has it flown yet? Curious minds want to know.

 

[Rktman]

It is now Oct. Has it flown yet? Curious minds want to know.

The launch is being held on the 26th. Trying to build a pad with a long 3/16" launch rod since the clubs rack rod's are far too short for my larger gliders. Hopefully I can finish in time but if I miss it, my next window will be November 16th.

 

[Ez2cDave]

View attachment 371917
Although the Hot Turkey was one of the first (if not THE first) swing wing glider that used a single pivot hinge for both wings, the Swinger was the first (circa 1999) to my knowledge that combined both a single hinge and an innovative piston and control rod mechanism to keep both wings locked back in a folded position during launch.

GROUNDHOG 16 . . . 1971

https://plans.rocketshoppe.com/narcomp/groundhog.pdf

HOT TURKEY . . . 1984

https://plans.rocketshoppe.com/pubs/Newsletters/SNOAR/SNOAR_News_8-84.pdf

There may have been other designs . . .

Dave F.

 

[Rktman]

GROUNDHOG 16 . . . 1971

https://plans.rocketshoppe.com/narcomp/groundhog.pdf

HOT TURKEY . . . 1984

https://plans.rocketshoppe.com/pubs/Newsletters/SNOAR/SNOAR_News_8-84.pdf

There may have been other designs . . .

Dave F.

Thanks for the links Dave. While the Groundhog used a piston and wire arrangement to release the wings, it had separate hinges for each wing, unlike the Hot Turkey which utilized a single pivot for both wings (but a burn string instead of piston). I kinda lost my enthusiasm for the Groundhog after discovering that you have to slit the motor pod to attach the wire hold-backs to the balsa piston. I may have a go at the Hot Turkey, though I tried the elastic/release pin/burn string method on one of my scratch builds and it didn't quite work reliably or consistently (though I admit I may not have rigged it in the most efficient way).
No matter, I'm having a great time learning about the evolution of variable geometry gliders during all those years that I was away, and it's a kick trying out some of those early designs. So much clever ingenuity and inventiveness, something that seems to be missing in the few glider kits still available from the larger surviving manufacturers. (J&H Aerospace may be the sole exception, in that it's a single owner operation that still exhibits that innovative spark). I have a hard time believing that gliders can't evolve any further, and sad to consider that people may just have given up being creative and inventive where gliders are concerned. Most of that these days seems to be focused on HPR only.

 

[Alan15578]

Thanks for the links Dave. While the Groundhog used a piston and wire arrangement to release the wings, it had separate hinges for each wing, unlike the Hot Turkey which utilized a single pivot for both wings (but a burn string instead of piston). I kinda lost my enthusiasm for the Groundhog after discovering that you have to slit the motor pod to attach the wire hold-backs to the balsa piston. I may have a go at the Hot Turkey, though I tried the elastic/release pin/burn string method on one of my scratch builds and it didn't quite work reliably or consistently (though I admit I may not have rigged it in the most efficient way).
No matter, I'm having a great time learning about the evolution of variable geometry gliders during all those years that I was away, and it's a kick trying out some of those early designs. So much clever ingenuity and inventiveness, something that seems to be missing in the few glider kits still available from the larger surviving manufacturers. (J&H Aerospace may be the sole exception, in that it's a single owner operation that still exhibits that innovative spark). I have a hard time believing that gliders can't evolve any further, and sad to consider that people may just have given up being creative and inventive where gliders are concerned. Most of that these days seems to be focused on HPR only.

Wow, there are so many points that I can respond to. To start, the Swinger build above is awesome, and I have never built one. I did buy a an ARF foam Swinger decades ago on closeout, just because I'm a swing wing guy. I'll probably never fly it.

There are basically two ways to advance contest designs, evolution and revolution. On its face, rocket contests are just stupid, because rockets have such inherent high performance. It is to our credit (mostly to GHS) that we have figured out ways (events and rules) to constrain performance enough to make it an enjoyable sport. Rocket Glide was one such effort to reduce performance of Boost Glide competition. Now we could not drop the spent motor an any other part of the entry, but we knew that something had to change between boost and glide. There were many revolutionary design solutions, and I tried them all, except for Tom Hoelle's excellent flapper. Each revolutionary design evolves further with almost every model built. It turns out that contest rocketeers are so skilled, that almost every design can become a winner. While we love to credit our designs, most victories are due to a heroic recovery or freakish weather. Personal preference pays a major roll in a designs popularity. Most of these revolutionary designs require both boost and glide trimming, but I never had a convenient place for test flying and trimming. However, I found that every Groundhog I built always boosted straight with no boost trimming, even though the Groundhog took longer to build and was a little heavier than other designs. The swing wing is so good that I'm surprised that it was not outlawed or sequestered like flexies were in B/G.

Jon Robbins published his Groundhog 16 plans in MRM in 1971. This was the 16th swing wing he built. It did not look very evolved. That piston and wire were dreadful, but I built my first one exactly to the plans. All of my subsequent Groundhogs used a burn string release. I don't recall who first accomplished or published that evolution, but it was hardly enough to justify publishing complete new plans. Indeed it would be tiresome to read a new evolved plan every month or so. To keep up, you had to do it yourself and actually attend contests. The Groundhog was actually optimized to use a 3x36 inch sheet of balsa with little waste. It is an open question how much you can evolve the design of a Groundhog (or any other design) and still call it a Groundhog. I met Jon when he came to our Mid America Regional 72, but we barely talked. He also flew a large Groundhog on an Enerjet F67, I was a bit downfield at the time, and it almost made it through the burn. Death of the unfit. It had a fiberglass fishing pole for the fuselage and a lot of lead up front. The last I heard or read, Jon was at Groundhog 123 or so, but I don't think he was responsible for as much design evolution as you might expect.

More later, but don't overlook the Groundhog in your journey through swing wing history.

 

[Alan15578]

You seem to be focused on designs that have been kitted, but the best contest designs are only available through plans, and many are totally unpublished. Furthermore, designs and features that came to light later are often inferior to older designs. There is just no reckoning for personal preference. I cringe at some of the features of J&H Aerospace products, but I'll probably buy one someday, just because I'm a swing wing guy. NAR competition is effectively dead and can't support the sort of cottage industry that it has in the past. If you want to make a buck, HPR is where the money is today, although scale and sport rockets are still getting by. One design that you should consider is Al Nienast's XP-2 swing wing, If the Groundhog is the thoroughbred of swing wings, XP-2 is the quarter horse, and the Swinger is the plow horse.

The Hot Turkey looks good on paper, but it is a bit complex with more fiddly bits. The Groundhog typically trails two long burn strings from each wing tip in glide, and I never liked that. I had often considered a release method similar to the Hot Turkey, but I preferred to avoid all those fittings and keep it simple. I have always wanted to try a single pivot design to further reduce boost drag, but then it is harder to build in dihedral. The Hot Turkey uses flip up tips, while I would have preferred simply (groan) warping the wings. The other issue is that a swing wing like the Groundhog can lose as much as half of its boost altitude if the wings deploy in a vertical ascent. It can pull 3/4 of a loop transitioning toward a stable glide. The Groundhog has enough dihedral effect (roll stability) on boost, that you can launch it at an angle into a parabolic trajectory and it will stay right side up, deploying the wings at a more favorable attitude. I don't know how well the Hot Turkey transitions and performs in practice. It may be worth a try, and it may just come down to personal preference on the complexity issue.

On the matter of cleverness, it is worth noting that many ideas have propagated between NAR competition and AMA/NFFS contest developments. Certainly B/G has borrowed a lot from HLGs, and swing wings can borrow a bit from tow line gliders. I hung out with Stan Stoy for a while and he had designed two record setting indoor HLGs. His low ceiling Coot design was inspired by the flap wing R/G. His high ceiling Folder was inspired by the flop wing design, although I was more impressed with its q-trigger used to deploy the wings. I do think cleverness and ingenuity has been and continues to be offered by both large and small manufacturers, just not at the rate of individuals.

Later I'll conclude with the Groundhog.

 

[Ez2cDave]

Actually the Centuri Mach 10 is even worse; it's glide is more a controlled (barely) fall, but only after it performs its always reliable head-removing loop. But I knew that going in and built it for fun knowing it has to be boosted high enough not to risk taking out someone's eye.

I'm going to upscale it and redesign it without the offset motor tube and the draggy air brake of a stab that causes the looping. Should make for a fast sink rate but otherwise fairly decent glider.

Re-design the Tail to "Pop-Up" for glide, after ejection . . .

Dave F.

 

[Rktman]

Re-design the Tail to "Pop-Up" for glide, after ejection . . .

Dave F.

Haven't quite figured out how to do that yet. Maybe a burn string? Any suggestions on a mechanism to keep it flat during boost would be much appreciated.

 

[Rktman]

You seem to be focused on designs that have been kitted, but the best contest designs are only available through plans, and many are totally unpublished. Furthermore, designs and features that came to light later are often inferior to older designs. There is just no reckoning for personal preference. I cringe at some of the features of J&H Aerospace products, but I'll probably buy one someday, just because I'm a swing wing guy. NAR competition is effectively dead and can't support the sort of cottage industry that it has in the past. If you want to make a buck, HPR is where the money is today, although scale and sport rockets are still getting by. One design that you should consider is Al Nienast's XP-2 swing wing, If the Groundhog is the thoroughbred of swing wings, XP-2 is the quarter horse, and the Swinger is the plow horse.

The Hot Turkey looks good on paper, but it is a bit complex with more fiddly bits. The Groundhog typically trails two long burn strings from each wing tip in glide, and I never liked that. I had often considered a release method similar to the Hot Turkey, but I preferred to avoid all those fittings and keep it simple. I have always wanted to try a single pivot design to further reduce boost drag, but then it is harder to build in dihedral. The Hot Turkey uses flip up tips, while I would have preferred simply (groan) warping the wings. The other issue is that a swing wing like the Groundhog can lose as much as half of its boost altitude if the wings deploy in a vertical ascent. It can pull 3/4 of a loop transitioning toward a stable glide. The Groundhog has enough dihedral effect (roll stability) on boost, that you can launch it at an angle into a parabolic trajectory and it will stay right side up, deploying the wings at a more favorable attitude. I don't know how well the Hot Turkey transitions and performs in practice. It may be worth a try, and it may just come down to personal preference on the complexity issue.

On the matter of cleverness, it is worth noting that many ideas have propagated between NAR competition and AMA/NFFS contest developments. Certainly B/G has borrowed a lot from HLGs, and swing wings can borrow a bit from tow line gliders. I hung out with Stan Stoy for a while and he had designed two record setting indoor HLGs. His low ceiling Coot design was inspired by the flap wing R/G. His high ceiling Folder was inspired by the flop wing design, although I was more impressed with its q-trigger used to deploy the wings. I do think cleverness and ingenuity has been and continues to be offered by both large and small manufacturers, just not at the rate of individuals.

Later I'll conclude with the Groundhog.

I've been fascinated by variable geometry R/Gs since I was a kid. Never got the chance to build any, so since becoming a BAR I finally get the chance to satisfy that need by building some of those gliders that grabbed my attention and imagination all those years ago. Not necessarily models that were kitted, but things that catch my fancy as being cool or embody clever solutions to increase performance. Swing wings, scissor-flops, slide pods, slide wings, etc., I'm pretty much on a quest to build them all just for the fun of it and to satisfy my curiosity. It's also been a great learning experience. (I just finished an original scratch-built slide pod R/G that flies surprisingly well after gleaning all I could from online sources of glider design guidelines, several of Frank Zaic's publications, and exposure to several decade's worth of rocketry mags and old glider designs). While I've also designed/built other original "conventional" gliders for the learning experience, I still have a bucket list full of those nostalgic "shape changers" that I want to build, because I think they were innovative for their time and just...well...amazing to watch unfold themselves at apogee and soar.

 

[BABAR]

Haven’t done burn strings for a while, but when I did I replaced the string with elastic thread. It burned just as easily, and kept everything “tighter” then I could do with plain thread. It also tends to “autoretract” once burned, so less likely to hang up.

YMMV

 

[Ez2cDave]

Haven't quite figured out how to do that yet. Maybe a burn string? Any suggestions on a mechanism to keep it flat during boost would be much appreciated.

Put a hinge at the front. Activate it with elastic. Use Dental Floss as a burn string, attached at the rear, passed down through guides. At ejection, the burn string releases the elevator.

Dave F.

 

[Rktman]

Haven’t done burn strings for a while, but when I did I replaced the string with elastic thread. It burned just as easily, and kept everything “tighter” then I could do with plain thread. It also tends to “autoretract” once burned, so less likely to hang up.

YMMV

I tried elastic thread with a slide pod glider but even stretching it taut, there was still enough "give" that the motor pod would slide backward some. Tried several times but it kept on stretching till it snapped before it could hold the pod completely forward. I suppose a half inch short of its full forward position isn't all that critical though.