Holverson Swinger RG – resurrection of a nostalgic classic

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Rktman

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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.
Sounds like that would work great with the upscale I hope to build. No complicated fiddly bits to mess with, just a nice easy to construct solution. I like it!
 

Alan15578

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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on designs that have been kitted, but the best contest designs are only available through plans, and many are totally unpublished.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'm finally continuing with the Groundhog evolution. I re-read Jon Robbins Groundhog 16 article. It seems that he was most concerned with boost drag, and minimizing frontal area, while the real advantage of swing wings is that they have very low load during boost. Of course ideally you always want to boost high and establish a high enough sink rate that you keep thermals from stealing you model, while still winning. In practical terms you want to optimize over all three flight phases, boost, transition, and glide to maximize duration and then work with or around thermals. The Groundhog 16 was flown with a A5-2S, and has a very generous wing area. The large wing area is good because it is generally timed until the timers loose sight of it, and you prefer that timers lose sight of competitors models sooner. Sizing is one of the most important aspects of scaling the Groundhog to different motor classes. Through experience, I have found 1.5 " chord to be best for B motors, 1" for A (A3-2t) and 1/2A motors, 3/4" did not work well for 1/4A Motors, 2" for C motors, and 2.5" for D motors. I have not had occasion to fly E or higher R/G, but The swing wing should be best suited to higher boost speeds.

The first evolution is to get rid of that heavy wire and piston, and use a simple burn string release. At the same time I moved the elastic out from the pivot to pull forward, much like on the Hot Turkey. If you do not constrain the wing tips, the wings will flutter on boost and often shred. I push a straight pin into the bottom of the fuselage, just ahead of the tail surfaces. Pull the pin out and cut it to a shorter length. Push it back in the pin hole and and use pliers to drive it in until just enough is remaining to catch the burn strings. I use a thin nylon cord of the type commonly used for parachute shroud lines. Cut a long piece of string and fix a a small Avery adhesive pad (the same material commonly used to secure shroud lines to parachutes) to one end of the string. Hook it around the pin and stick it tightly to the underside of the folded back wing at the trailing edge. run the string straight up the bottom of the fuselage, over a shallow notch cut in the front if the fuselage, loop it through the motor pod vent ports twice, forming an X in front of the motor, run it back over the notch and down the fuselage and around the pin in the pin from the opposite side the the other folded wing. Pull the string tight, there will be some elasticity in the nylon chord, and tape it to the other wing just like the first one, and trim off the excess. This has proven to be enough to keep the wings from fluttering on boost, and I have never had deployment failure, aside from catos and human error (forgetting to attach the elastic).

The second evolution is using an undercambered airfoil. This will give about 15% more duration performance in glide with no boost penalty, due to the swung back wings. The undercambered wing will have more pitch down moment that will require more more trim down force from the stabilizer, or moving the CG aft. At this point it may be helpful to look at some AMA towline gliders. You can find designs with undercambereed lifting stabilizers, and far aft CGs. We could calculate the neutral point and establish aft CG stability limit, or find the condition that minimized trim drag. However, the R/G still has to contend with transition, so I recommend moving the CG just a little aft, but not as far as possible. You can pick an airfoil used by a successful towline glider flying a similar Reynolds Number, or you can pick one out of a catalog, or even design one. I'm not very particular about airfoils, I just use what seems about right.

The third evolution is just materials. For the wings, I use thicker C grain contest balsa, but I sand most of that material away, but save your lightest wood for other projects. I cover the inner portion of the wing with tissue, and on large models I'll add an second layer of tissue on the inner most portion of the wing. The Spruce Fuselage on the B and smaller sized Groundhogs is fine, but is too heavy when scaled up. For a 2.5" chord model, I used hard balsa laminated with carbon fiber reinforcement. It will not have the impact strength of Spruce, but it will be stiffer and lighter. Covering the stab with tissue is also a good idea.

The fourth evolution is simply a hodgepodge of improvements such as adding a pop up stab DT, more attention to streamlining the pivots, and making the wings/ pivots repairable by using replacing the pivot axles with nylon screws and bushings, and bit of plywood reinforcement.
 

Alan15578

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I'm finally continuing with the Groundhog evolution. I re-read Jon Robbins Groundhog 16 article. It seems that he was most concerned with boost drag, and minimizing frontal area, while the real advantage of swing wings is that they have very low load during boost. Of course ideally you always want to boost high and establish a high enough sink rate that you keep thermals from stealing you model, while still winning. In practical terms you want to optimize over all three flight phases, boost, transition, and glide to maximize duration and then work with or around thermals. The Groundhog 16 was flown with a A5-2S, and has a very generous wing area. The large wing area is good because it is generally timed until the timers loose sight of it, and you prefer that timers lose sight of competitors models sooner. Sizing is one of the most important aspects of scaling the Groundhog to different motor classes. Through experience, I have found 1.5 " chord to be best for B motors, 1" for A (A3-2t) and 1/2A motors, 3/4" did not work well for 1/4A Motors, 2" for C motors, and 2.5" for D motors. I have not had occasion to fly E or higher R/G, but The swing wing should be best suited to higher boost speeds.

The first evolution is to get rid of that heavy wire and piston, and use a simple burn string release. At the same time I moved the elastic out from the pivot to pull forward, much like on the Hot Turkey. If you do not constrain the wing tips, the wings will flutter on boost and often shred. I push a straight pin into the bottom of the fuselage, just ahead of the tail surfaces. Pull the pin out and cut it to a shorter length. Push it back in the pin hole and and use pliers to drive it in until just enough is remaining to catch the burn strings. I use a thin nylon cord of the type commonly used for parachute shroud lines. Cut a long piece of string and fix a a small Avery adhesive pad (the same material commonly used to secure shroud lines to parachutes) to one end of the string. Hook it around the pin and stick it tightly to the underside of the folded back wing at the trailing edge. run the string straight up the bottom of the fuselage, over a shallow notch cut in the front if the fuselage, loop it through the motor pod vent ports twice, forming an X in front of the motor, run it back over the notch and down the fuselage and around the pin in the pin from the opposite side the the other folded wing. Pull the string tight, there will be some elasticity in the nylon chord, and tape it to the other wing just like the first one, and trim off the excess. This has proven to be enough to keep the wings from fluttering on boost, and I have never had deployment failure, aside from catos and human error (forgetting to attach the elastic).

The second evolution is using an undercambered airfoil. This will give about 15% more duration performance in glide with no boost penalty, due to the swung back wings. The undercambered wing will have more pitch down moment that will require more more trim down force from the stabilizer, or moving the CG aft. At this point it may be helpful to look at some AMA towline gliders. You can find designs with undercambereed lifting stabilizers, and far aft CGs. We could calculate the neutral point and establish aft CG stability limit, or find the condition that minimized trim drag. However, the R/G still has to contend with transition, so I recommend moving the CG just a little aft, but not as far as possible. You can pick an airfoil used by a successful towline glider flying a similar Reynolds Number, or you can pick one out of a catalog, or even design one. I'm not very particular about airfoils, I just use what seems about right.

The third evolution is just materials. For the wings, I use thicker C grain contest balsa, but I sand most of that material away, but save your lightest wood for other projects. I cover the inner portion of the wing with tissue, and on large models I'll add an second layer of tissue on the inner most portion of the wing. The Spruce Fuselage on the B and smaller sized Groundhogs is fine, but is too heavy when scaled up. For a 2.5" chord model, I used hard balsa laminated with carbon fiber reinforcement. It will not have the impact strength of Spruce, but it will be stiffer and lighter. Covering the stab with tissue is also a good idea.

The fourth evolution is simply a hodgepodge of improvements such as adding a pop up stab DT, more attention to streamlining the pivots, and making the wings/ pivots repairable by using replacing the pivot axles with nylon screws and bushings, and bit of plywood reinforcement.
I neglected the tow hook in the Fourth evolution. I added this to assist trimming.

There are several issues with the Groundhog. The wing aspect ratio of 24 is extremely high for duration glider. The fuselage length is very long, making the short period mode highly damped, and the phugoid mode lightly damped.. The wings actually flex quite a bit during the phugoid oscilations. If you shortened things up it would have better dynamics, and move closer to the XP-2. Induced drag can be minimized with an elliptic lift distribution, but at an aspect ratio of 24 it is already very low. One could change to an elliptical planform, or twist the wings (washout) which will also eliminate tip stall. I generally try to select wood with a suitable twist or try to build in twist when I cover the wings with tissue. I'd also like to try a tapered wing, say 1.75 at the root and 1.25 at the tip, with the wing thickness tapered as well. Although, this would increase the pivot size and drag, and we might not be able to call it a Groundhog. So, there is still scope for further evolution even in a classic well used design.
 

Rktman

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I neglected the tow hook in the Fourth evolution. I added this to assist trimming.

There are several issues with the Groundhog. The wing aspect ratio of 24 is extremely high for duration glider. The fuselage length is very long, making the short period mode highly damped, and the phugoid mode lightly damped.. The wings actually flex quite a bit during the phugoid oscilations. If you shortened things up it would have better dynamics, and move closer to the XP-2. Induced drag can be minimized with an elliptic lift distribution, but at an aspect ratio of 24 it is already very low. One could change to an elliptical planform, or twist the wings (washout) which will also eliminate tip stall. I generally try to select wood with a suitable twist or try to build in twist when I cover the wings with tissue. I'd also like to try a tapered wing, say 1.75 at the root and 1.25 at the tip, with the wing thickness tapered as well. Although, this would increase the pivot size and drag, and we might not be able to call it a Groundhog. So, there is still scope for further evolution even in a classic well used design.
Much thanks. Lots of great info here applicable to glider design; invaluable when scratch-building original designs and making improvements to older proven ones.
Since I now have the opportunity to build all those gliders that I always wanted to as a kid but never got the chance to, I'm on a quest to do as many as I possibly can get to. Doesn't matter if they were superior fliers or just average, since I'm doing it just for sport and the fun of it, not for competition.
It's also been a good learning experience that has allowed me to dabble in some original designs along the way, which is why I find your input valuable.
 

Alan15578

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Thanks. There are probably dozens of things about the Groundhog that I have not said, or even totally forgotten. One on them is that the dihedral shown in the Groundhog 16 plans is much greater than needed. It is sad that I have acquired so much skill and experience, and there no one to pay it forward to, at least not locally. I have yet to build a 1/8A, or an E or larger Groundhog, there would be no point.

I've been waiting for John Bean to release his mark 4 altimeter. What I really want is a similarly sized follow on product, a DT release, or maybe an altimeter with DT function built in. This would make sport flying B/Gs and R/Gs practical.
 

Rktman

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[QUOTE="Alan15578, post: 1932230, member: It is sad that I have acquired so much skill and experience, and there no one to pay it forward to, at least not locally. I have yet to build a 1/8A, or an E or larger Groundhog, there would be no point.[/QUOTE]

I'd say you're certainly paying it forward here on the Forum by sharing your knowledge and expertise gained from years of experience. It's invaluable to BARs and those just getting into the sport. I'm a glider fanatic but don't have the benefit of an aeronautics, engineering, or even balsa glider flying/design/construction experience, so any knowledge I gain here or from other online or printed sources is always much valued.

For myself, the point of building a 1/8A or 24mm Groundhog or other swing wing would just be for the challenge and fun of it, to see if I could get it to work successfully and what I could learn in the process of designing, building, and flying it. (My one attempt at a swing wing, as a clueless newbie 3 years ago, was an eye opener...it unintentionally spun like a top on the way up and refused to fully deploy its wings. I sure learned a lot from that less than stellar attempt). Now that I'm a little bit wiser, I intend to give it another try this winter.
 

Rktman

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You, sir, are a fount of knowledge! Great info, and just what this forum category could use, especially since there seems to be more beginners here (than on YORF) and we can really benefit from a deep knowledge library like this. Really helps to build it right the first time, and not to have to make the same mistakes that someone else has already made and found the solutions to. Hopefully others will also leave tips and advice gleaned from hands-on experience or their background.
 

Ez2cDave

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You are very welcome . . . I hope that everyone benefits from it !

Dave F.
 

Rktman

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It is now Oct. Has it flown yet? Curious minds want to know.
Couldn't make this month's launch, looks like my next opportunity is the 16th of this month if the winds drop below double digit.
 

Rktman

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Looks like I'm going to have to postpone the Swinger's maiden yet again. With sustained double digit wind speeds and 43mph gusts forecasted, it'll have to wait for next month's Tripoli East launch date. :(
 

BABAR

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Looks like I'm going to have to postpone the Swinger's maiden yet again. With sustained double digit wind speeds and 43mph gusts forecasted, it'll have to wait for next month's Tripoli East launch date. :(
Good choice!
 

Rktman

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Finally got the chance to launch the Swinger yesterday. It would've been a glorious flight...if it had not gotten hung up on the launch rod.
With the wings still folded, the top wing got charred pretty severely. Guess metallized mylar tape wasn't a good protective solution. The heat from the ejection charge also caused the piston to swell and jam in place. Well, at least the wings deployed perfectly--though that seemed more anti-climatic comic relief than dramatic.
I need to take a closer look but everything looks fairly easy to repair. Unjam the piston and use a strip of aluminum tape to protect top wing and she should be ready to fly at the next launch in 2 weeks.
IMG_3862.JPG
1st flight damage.JPG
 

Rktman

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Followup:
Was surprised when I maidened my Swinger yesterday; it stalled like crazy, doing several deep U-shaped dive-and-recover loops before doing a nose plant 15' above the ground. Trying to diagnose the problem. My CG (with wings extended and an expended motor casing in place) is EXACTLY where the plans indicate it should be but it's obviously tail-heavy, something I rarely experience with an RG. The glider deployed smoothly after a straight boost, and it glided beautifully during hand-trimming tosses both before and after, so this is a real head scratcher.
 
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Ez2cDave

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Followup:
Was surprised when I maidened my Swinger yesterday; it stalled like crazy, doing several deep U-shaped dive-and-recover loops before doing a nose plant 15' above the ground. Trying to diagnose the problem. My CG (with wings extended and an expended motor casing in place) is EXACTLY where the plans indicate it should be but it's obviously tail-heavy, something I rarely experience with an RG. The glider deployed smoothly after a straight boost, and it glided beautifully during hand-trimming tosses both before and after, so this is a real head scratcher.
Eric,

Hmm . . . Maybe a Wing Incidence or Stab Incidence ( Decalage ) issue ?

It might behave "normally" during hand-tossing, where velocities are low and the initial "glide angle" is controlled by you. However, when deployed at Apogee, it may be undergoing the "sequence" . . .
Dive . . . Acceleration . . . Pull-Out . . . Climbing Glide . . . Stall . . . ( Cycle repeats ).

Thoughts ?

Dave F.
 
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Rktman

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Eric,

Hmm . . . Maybe a Wing Incidence or Stab Incidence ( Decalage ) issue ?

It might behave "normally" during hand-tossing, where velocities are low and the initial "glide angle" is controlled by you. However, when deployed at Apogee, it may be undergoing the "sequence" . . .
Dive . . . Acceleration . . . Pull-Out . . . Climbing Glide . . . Stall . . . ( Cycle repeats ).

Thoughts ?

Dave F.
Sounds very plausible. Easiest fix would be a bit of clay on the nose. Could also affix small trim tabs to the tail. Both options somewhat of a PITA since how much clay or trim tab angle is pretty much a shot in the dark and the only way to determine how much is to launch and assess. Oh well, gotta do what I gotta do. Good learning experience and gives me an excuse to get out and do some test launches this winter.
 

Ez2cDave

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Sounds very plausible. Easiest fix would be a bit of clay on the nose. Could also affix small trim tabs to the tail. Both options somewhat of a PITA since how much clay or trim tab angle is pretty much a shot in the dark and the only way to determine how much is to launch and assess. Oh well, gotta do what I gotta do. Good learning experience and gives me an excuse to get out and do some test launches this winter.
Eric.

I sent you Doug Holverson's email address, via private email.

Dave F.
 

Alan15578

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[QUOTE="Alan15578, post: 1932230, member: It is sad that I have acquired so much skill and experience, and there no one to pay it forward to, at least not locally. I have yet to build a 1/8A, or an E or larger Groundhog, there would be no point.
I'd say you're certainly paying it forward here on the Forum by sharing your knowledge and expertise gained from years of experience. It's invaluable to BARs and those just getting into the sport. I'm a glider fanatic but don't have the benefit of an aeronautics, engineering, or even balsa glider flying/design/construction experience, so any knowledge I gain here or from other online or printed sources is always much valued.

For myself, the point of building a 1/8A or 24mm Groundhog or other swing wing would just be for the challenge and fun of it, to see if I could get it to work successfully and what I could learn in the process of designing, building, and flying it. (My one attempt at a swing wing, as a clueless newbie 3 years ago, was an eye opener...it unintentionally spun like a top on the way up and refused to fully deploy its wings. I sure learned a lot from that less than stellar attempt). Now that I'm a little bit wiser, I intend to give it another try this winter.[/QUOTE]

A MM Groundhog might be interesting, but a Bumblebee like design with a trim tab would likely be better. E and F Groundhogs are too easy with the Estes E12 and F15 motors, and just use up more money and materials.
 

Alan15578

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Finally got the chance to launch the Swinger yesterday. It would've been a glorious flight...if it had not gotten hung up on the launch rod.
With the wings still folded, the top wing got charred pretty severely. Guess metallized mylar tape wasn't a good protective solution. The heat from the ejection charge also caused the piston to swell and jam in place. Well, at least the wings deployed perfectly--though that seemed more anti-climatic comic relief than dramatic.
I need to take a closer look but everything looks fairly easy to repair. Unjam the piston and use a strip of aluminum tape to protect top wing and she should be ready to fly at the next launch in 2 weeks.
View attachment 399885
View attachment 399888
With airflow from a normal launch, the aluminized mylar tape should be adequate. Actual Metal foil will hold up better to the type of failur that you experienced.
 

Ez2cDave

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I'd say you're certainly paying it forward here on the Forum by sharing your knowledge and expertise gained from years of experience. It's invaluable to BARs and those just getting into the sport. I'm a glider fanatic but don't have the benefit of an aeronautics, engineering, or even balsa glider flying/design/construction experience, so any knowledge I gain here or from other online or printed sources is always much valued.
Alan,

I think you will enjoy the glider material in this thread :

https://www.rocketryforum.com/threads/glider-design-trimming-library.155758


Dave F.
 

Alan15578

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Thank you kind sir!
I am guessing that you did not get anything helpful from Doug Holverson, or at least nothing to share. I'll take a WAG at this, but understand that the Swinger is an atypical design that I have not flown.

The design CG is one of the most important specifications. You should always balance to the prescribed CG, then adjust or trim surfaces. I think the Swinger has a rather aft CG location and the stabilizer actually produces lift in gliding flight. Your build might be be considerably better that the nominal Swinger. It is possible that the stab stalls before the wing, producing the pronounced pitch up that you observed. You always want the wing to stall first, or in the case of a canard configuration, you want the canard to stall first.
 

Rktman

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I am guessing that you did not get anything helpful from Doug Holverson, or at least nothing to share. I'll take a WAG at this, but understand that the Swinger is an atypical design that I have not flown.

The design CG is one of the most important specifications. You should always balance to the prescribed CG, then adjust or trim surfaces. I think the Swinger has a rather aft CG location and the stabilizer actually produces lift in gliding flight. Your build might be be considerably better that the nominal Swinger. It is possible that the stab stalls before the wing, producing the pronounced pitch up that you observed. You always want the wing to stall first, or in the case of a canard configuration, you want the canard to stall first.
That's what I couldn't understand, I had the CG spot on according to the plans but it was still stalling. I added a bit of clay to the nosecone, but made the mistake of bypassing the sticking piston by using a burn string. The string severed alright, but for some reason the wings didn't deploy and it came in ballistic. Oddly I never found the front half of the motor pod. Good thing Holverson designed it pretty stout, everything else survived intact.

Not sure what to look for with the stab to diagnose if it's the culprit. I built everything exactly as specified and had everything but the wings laser cut to ensure accuracy.
 

Alan15578

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[QUOTE="Alan15578, post: 1932230, member: It is sad that I have acquired so much skill and experience, and there no one to pay it forward to, at least not locally. I have yet to build a 1/8A, or an E or larger Groundhog, there would be no point.
I'd say you're certainly paying it forward here on the Forum by sharing your knowledge and expertise gained from years of experience. It's invaluable to BARs and those just getting into the sport. I'm a glider fanatic but don't have the benefit of an aeronautics, engineering, or even balsa glider flying/design/construction experience, so any knowledge I gain here or from other online or printed sources is always much valued.

For myself, the point of building a 1/8A or 24mm Groundhog or other swing wing would just be for the challenge and fun of it, to see if I could get it to work successfully and what I could learn in the process of designing, building, and flying it. (My one attempt at a swing wing, as a clueless newbie 3 years ago, was an eye opener...it unintentionally spun like a top on the way up and refused to fully deploy its wings. I sure learned a lot from that less than stellar attempt). Now that I'm a little bit wiser, I intend to give it another try this winter.[/QUOTE]
 

Alan15578

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I'd say you're certainly paying it forward here on the Forum by sharing your knowledge and expertise gained from years of experience. It's invaluable to BARs and those just getting into the sport. I'm a glider fanatic but don't have the benefit of an aeronautics, engineering, or even balsa glider flying/design/construction experience, so any knowledge I gain here or from other online or printed sources is always much valued.
[/QUOTE]
You don't need the befit of an engineering degree. I did far more interesting B/G and R/G experiments and developments before I ever went to college, and one can learn from or share with just natural interest and talents.
 

Rktman

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You don't need the befit of an engineering degree. I did far more interesting B/G and R/G experiments and developments before I ever went to college, and one can learn from or share with just natural interest and talents.[/QUOTE]
Agreed!
 

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That's what I couldn't understand, I had the CG spot on according to the plans but it was still stalling. I added a bit of clay to the nosecone, but made the mistake of bypassing the sticking piston by using a burn string. The string severed alright, but for some reason the wings didn't deploy and it came in ballistic. Oddly I never found the front half of the motor pod. Good thing Holverson designed it pretty stout, everything else survived intact.

Not sure what to look for with the stab to diagnose if it's the culprit. I built everything exactly as specified and had everything but the wings laser cut to ensure accuracy.
Any chance that the position of the components is different after an apogee deployment than it is when you are doing test flights on the ground? In other words, the action of the aerial deployment may be positioning the wings or other components slightly different than when you are ground testing. One thing you could try and is that if it is flying well on ground test and you launch it and it doesn't fly well would be to take the immediately recovered rocket and try to do ground test tosses with it. Does it still glide well or does it porpoise like the flight? My suspicion is that there is something "slightly "different between the position of the components when deployed on an actual flight than when you are ground testing. Another possibility is that aerial deployment initial forward velocity is near zero (essentially like just releasing it in dead air at altitude rather than the forward momentum imparted with a ground level "toss") that's always a challenge for configuration transition type gliders (as opposed to @iter 's gliders that use remote control to transition their vertical velocity to horizontal velocity). Swing wing, pop pod, elevator release mechanisms have to assume the glider starts with zero velocity in dead air.
 

Ez2cDave

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Any chance that the position of the components is different after an apogee deployment than it is when you are doing test flights on the ground? In other words, the action of the aerial deployment may be positioning the wings or other components slightly different than when you are ground testing. One thing you could try and is that if it is flying well on ground test and you launch it and it doesn't fly well would be to take the immediately recovered rocket and try to do ground test tosses with it. Does it still glide well or does it porpoise like the flight? My suspicion is that there is something "slightly "different between the position of the components when deployed on an actual flight than when you are ground testing. Another possibility is that aerial deployment initial forward velocity is near zero (essentially like just releasing it in dead air at altitude rather than the forward momentum imparted with a ground level "toss") that's always a challenge for configuration transition type gliders (as opposed to @iter 's gliders that use remote control to transition their vertical velocity to horizontal velocity). Swing wing, pop pod, elevator release mechanisms have to assume the glider starts with zero velocity in dead air.
BABAR,

That is an interesting theory and bears further investigation . . .

Eric,

My hypothesis ( slightly different ), based on BABAR's theory, is that the wings may not be fully deploying at ejection. Since the glider has forward momentum and aerodynamic drag is always a factor, the wings may not be "snapping open" at deployment, unlike what they do on the ground.

Try this . . . When doing your glide tests, first allow the wing to "snap open" and test it. Second, restrain the wings during opening and only allow the elastic to gradually pull them into position ( DO NOT "push them forward", at all ) and the repeat the glide tests, to see the difference.

If this is the situation, it should be correctable by increasing tension on the deployment elastic or replacing it with a stronger elastic.

Thoughts ?

Dave F.
 
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