Holverson Swinger RG – resurrection of a nostalgic classic

[Rktman]

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.

As far as I can tell everything is in proper alignment when the wings deploy. I did try some hand tosses immediately after it's initial flight and it glided nice and level, which is why I'm at a loss to figure out what's up with it when it's launched. After it lawn-darted on its second flight I'm going to have to rebuild the motor pod/piston and retry it with a few grams of nose weight to see what it does.

Serendipitously I was gifted with another Swinger kit by a fellow club member so I'm going to build that one completely stock and see how it flies. I'll be able to compare the two to see if I can spot any differences at all in the lifting surfaces or alignment of components. Hopefully I can discover the culprit, which would make for a very valuable learning experience.

 

[Rktman]

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.

The actual "1st" flight never left the pad—the glider got hung up on the launch rod but the wings did deploy fully, about the only thing successful about the aborted attempt lol. You're right that aerodynamic drag may be a factor here, so maybe I should try throwing it hard with the wings folded back in launch position to see what happens. There's already quite a bit of tension in the elastic but I could also try tightening them up a tad as well.

 

[Rktman]

Started work on replacing the motor pod and noticed that the wings deploy with so much force, they've left a dent in the fuselage. Hmmm...it's only between 1/32" and 1/16" deep but I'm wondering if it hyperextends the wings just barely enough to cause the stalling? Grasping at straws at this point, but the wing's root edges appear to still be perpendicular to the fuselage so I can't be sure. At any rate, the wings definitely are fully deploying. I'll need to either go with a slightly longer elastic or glue on a small square of 1/64" ply to protect any further deepening of the dent.

 

[Ez2cDave]

Started work on replacing the motor pod and noticed that the wings deploy with so much force, they've left a dent in the fuselage. Hmmm...it's only between 1/32" and 1/16" deep but I'm wondering if it hyperextends the wings just barely enough to cause the stalling? Grasping at straws at this point, but the wing's root edges appear to still be perpendicular to the fuselage so I can't be sure. At any rate, the wings definitely are fully deploying. I'll need to either go with a slightly longer elastic or glue on a small square of 1/64" ply to protect any further deepening of the dent.

Eric,

Great observation !

My theory is that the "over-deploying" wings are giving you a different CG location, relative to the Average Chord of the Wings. If that is happening, trimming would be very inconsistent. Reinforcing the area and re-establishing correct alignment should stop the problem.

Dave F.

 

[Rktman]

Eric,

Great observation !

My theory is that the "over-deploying" wings are giving you a different CG location, relative to the Average Chord of the Wings. If that is happening, trimming would be very inconsistent. Reinforcing the area and re-establishing correct alignment should stop the problem.

Dave F.

Didn't think of that, thanks! With the original motor now torn off, I'll have to remember not to repair the dents until after it's back together again so I can test that theory. Hope it was the cause of the stalling, would sure like to solve this mystery.

 

[Rktman]

Update

It’s been awhile (new builds tend to get priority over repairs, which tend to be “when I get around to it”). Per the suggestion from Ez2cDave in another thread, I replaced the balsa piston with an 18mm coupler from Mach 1 Rocketry. Steve Skinner from Mach 1 was kind enough to include a bunch of thick G10 ‘glass rounds that are punched out when creating ‘glass centering rings for his kits. I used it to seal the ejection end of the piston and used a standard ply block to close off the forward end where it slams up against the piston stop inside the motor tube. The piston assembly should now be far more heat proof and resistant to ejection damage than the balsa version.






I sanded down the burnt original balsa piston so it would fit inside the coupler. Probably didn’t need to but it helped center the holes I needed to drill for the control rod, and helps hold the rod snugly inside the ‘glass coupler so it won’t wander until I can install it in the motor pod and anchor it in place with a little thin CA. A little bit of JB Weld on the ejection end and it’s ready to go.




Motor pod’s ready to be installed on the glider pylon. Should be interesting to see where the CG falls with the marginally heavier piston. It may save me the need to add nose weight to stop the stalling. I’ll also be repairing the dent in the fuselage where the wing roots slap up against it and seeing if that was changing the wing position or shifting the CG just enough to cause the porpoising. Probably won’t get a chance to trim or test fly it anytime soon though.

 

[Ez2cDave]

Eric,

Looking good . . . That ought to solve the piston issues !

Steve Skinner is a really nice guy and a "class act". I've spoken with him on the phone several times ( long conversations - LOL ! )

Dave F.

 

[Rktman]

Eric,

Looking good . . . That ought to solve the piston issues !

Steve Skinner is a really nice guy and a "class act". I've spoken with him on the phone several times ( long conversations - LOL ! )

Dave F.

Steve's a great guy, really enjoyed talking with him, that hour passed quickly. Interesting how he and his biz partner got into MPR/HPR and then subsequently started Mach 1. Couldn't resist buying my first 'glass kit (18mm Alien Interceptor).

 

[Rktman]

Update

I’ve been trying to analyze why my Swinger has such severe stalling problems for a long time even though everything is straight and aligned where it should be and the CG is exactly where it should be.

One day I was looking at the photo of its first launch, where it got hung up on the rod and charred its wing. I spend so much effort trying to protect my balsa from water and the intense humidity here, I don’t know why it never occurred to me that HEAT can also warp balsa.

On a hunch I removed the left wing that got charred and put a straightedge on the wing’s top side. Sure enough, the heat had caused the whole wing to curl subtly lengthwise, to the point where the trailing edge was bent a little downward and the wing’s normally flat bottom was now somewhat under-cambered (further increasing its pitching moment and, I think, making it more susceptible to stalling at lower speeds).

 

[Rktman]

I fabricated new wings and took it for a test flight yesterday. Too much rod angle and somewhat underpowered on a B6-2, it barely had time to transition to glide. Not a perfect flight, but a lot better than previous flights where it came in ballistic after just two stall loops. Well, at least I didn’t lose it to thermals.
And thanks to @BABAR's idea of sacrificial frangible parts, my glider's motor pod was spared from being crushed (like in its previous flight) by the BBQ stick taped to its NC. The stick took the brunt of the force when the glider's pod impacted the ground -- hard.

It was also on too tight a spiral. Apparently the clay on the right wing to compensate for the heavier left wing came off sometime during the launch. Easily addressed.

The tip of the left (topmost when folded) wing sustained a little bit of blistering from the heat but I don’t think it got warped, thankfully.




But I’d have to say that overall the flight is still somewhat inconclusive. A follow-up flight on a C6-3 should give me a better idea of whether I may have finally solved the mystery.

 

[Rktman]

I was able to do another test flight today and this time the wings didn’t deploy. It came in ballistic after a long arc up – and then down. Apparently, the piston got jammed so the wire control rod couldn’t move forward to release the wings.

Also unfortunate that my video footage got corrupted somehow, but here’s a still pic of the carnage:



Not visible is the further heat damage to the top wing to either side of the protective aluminum strip. At this point, I will be building out an original kit that I was lucky enough to acquire a while ago. About the only changes I’ll make are using the thicker-walled “tough tube” for the motor pod, and two coats of dope to protect the balsa surfaces from water and/or humidity. I want to keep this build as light as possible.

To be continued…

 

[Crawf56]

Hang in there.

 

[Rktman]

Video link for post #100 above got broken. Since I can't edit it, here's the link url:

 

[Rktman]

Thanks for fixing the video link in post #100 Chuck! Appreciate it.

 

[Rktman]

It's been awhile, but I started the rebuild of the Swinger's motor pod and wing-release mechanism that was destroyed last year.

 

[Rktman]

Pylon area cleaned and refurbished, and waiting for first glue layer to set.

 

[Rktman]

Refurbished Swinger ready for rebalancing and trimming pending some cooperative weather.



With winter approaching, not sure when I’ll be able to schedule a test flight, since everything now appears to be in order. I’ve tried to diagnose and adjust and tweak everything I can think of at this point, but if it still acts wonky, it’ll be the only glider ever that I haven’t been able to make right. I’ll have to give up on this one and relegate it to the shelf queen category, then try building the original kit I still have stashed in my build pile to see if that one works as it should.

To be continued...