Semroc Scissor Wing Transport Kit Build Thread

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Success! Here’s the new fin/stuffer tube/motor tube assembly with the fins mounted 1/8” further forward. Now the trailing edge of the elevator flap just clears the dowel support. Having the fins that tiny bit forward shouldn’t make a difference during launch, but I’ll weight the front of the stuffer tube if necessary to keep the CG where instructions say it should be. What bothers me most is not being able to figure out a logical reason for this latest “gotcha”. Guess this one will have to remain a riddle, wrapped in a mystery, inside an enigma.

Fingers crossed that Murphy takes a permanent vacation from here on out.

flap fitz.JPG
 
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Ez2cDave

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So B6-2 and hope for the best? This glider will have to earn its paint and decals. It’ll either lawndart or glide away.

A word of caution . . .

I am pretty sure what I saw on the second toss . . . After watching it another dozen times, I don't believe that it "stalled", per se.

HOWEVER, it does appear to climb, while at higher velocity and then, as speed "bleeds off" due to aerodynamic drag, it noses over into a dive. I believe that this dive may steepen. As the airspeed increases, it SHOULD pull out of the dive. HOWEVER, once the airspeed drops again, the "cycle" will repeat.

SOLUTION : A reduction in nose weight, until the glide is level at LOW velocity.

Dave F.
 

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I look forward to seeing the first ever successful SWT flight on Youtube. Ever since mine shredded itself on the way up in 1982, I have always wondered what a nominal flight would look like.
 
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Just summarizing some potential problem areas to be aware of and some suggested fixes (refer to this thread's build steps for pics and more details):

1) DON’T ATTACH THE DOWEL AND MOUNT TO THE MOTOR TUBE UNTIL AFTER YOU’VE ATTACHED THE UPPER NACELLE AND ITS SUPPORT AND THE GUIDE TUBE THAT RUNS THROUGH IT.

That way you can assure it’ll be properly aligned with the guide tube and notch in the wingtip. If it's not, at least you'll have the opportunity to shim or sand the dowel support unit to adjust its height.

2) Also, roll your dowel across a flat surface beforehand to make sure it’s not warped. Mine was and it was a headache I could easily have avoided just by doing this.

3) The marking guide for both the motor tube and main body tube is off. It’s short by about 1/8” and won’t wrap completely around the tubes, so the positions of components will be off. That's because the templates are based on the original Estes 18mm and 24mm body tubes, which are thinner and smaller in diameter than the thicker supplied Semroc tubes.

You can either use the tube marking templates I redrew in post #28, or make your own by going here: https://www.apogeerockets.com/Advanced_Construction_Videos/Rocketry_Video_75 for an Apogee Rockets video on how to use Inkscape, Illustrator, or a similar vector program to create it.

The problem may have been corrected by now, but as of last week, the instruction sheet I downloaded that has both marking guides in it was still not correct.

4) Make sure that those little kidney bean inserts that get glued into the Wing Pivot Top don't stick up too high. You may have to sand them down, since they ride in slots in the Wing Pivot Plate and if they're too tall, they'll bind and the wing won't be able to rotate. (See the 2nd and 3rd pics in post #30 to see what I'm referring too).

5) Though not mentioned in the instructions, the wing pivot post is too tall and will need to be sanded down (1st pic, post #45). It's made of aluminum so it sands easily — just be careful not to shorten it too much, which can happen really quickly because of the soft metal.

6) Speaking of the wing pivot post, make sure it's glued in ABSOLUTELY VERTICAL into the Wing Pivot Top. How you assure this is up to your own ingenuity, but if it's even a tiny bit off, you'll be in for a world of problems because it'll tilt your wing, giving it either positive or negative incidence (bad) or result in one side of the wing being lower and one higher.

7) When deployed, the wings will be rotated 6° off perpendicular toward the left side. It seems the holes for the Pivot Stops (the kidney bean-shaped inserts) weren't lasered out directly opposite each other as they should have been (see post #63). I honestly don't know if having obliquely-oriented wings would affect the SWT performance at all, but I don't think it was intentionally designed in, as the original Estes version had wings that were at a right angle to the body. Anyway, see the same post for a solution to the problem.

8) Elevator clearance problem (not enough space for the elevator flap to fit between the end of the stab and the dowel standoff. See post #70). While not everyone seems to have had this problem, I did and you may. I have no idea why or how it occurs despite repeatedly double-checking all the alignment measurements from the instruction sheet.

The slots in the fins function as a block to limit how far the stuffer/motor tube assembly slides up into the main body tube (and hence, how close the dowel standoff gets to the end of the elevator flap). Seems simple enough, but I discovered that the fin slots were 1/8" too long, and that left insufficient space for the elevator to fit. I'd suggest dry-fitting the fins first to check how much elevator clearance you have before committing to glue. If not enough space, the easiest fix is to mount the fins further forward the small amount needed for the elevator to clear. In my case, it was 1/8”.

Edit 👉 9) If you decide to sand an airfoil into the wing, even if only a modest one, it’s best done BEFORE installing the Wing Pivot Plate. Once the plate is installed, the wing won’t sit flat on a surface, making it difficult to sand a consistent airfoil into it.

To be continued...
 
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Ez2cDave

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@Roz Rocketz Ron I don't know if you've flown yours yet, but I came across the CG location stipulated for the original Estes SWT. It's between 8.75" - 9.0" from the rear of the main body tube.View attachment 514508

EXCELLENT find, Eric !

From what I have seen, his model is nose heavy. At higher airspeeds the elevator generates enough force to offset that and allow level flight ( even a climb ). BUT, as the glider slows, it goes into a dive. Theoretically, once it picks up sufficient airspeed in the dive, it should pull out. However, as it slows again, the cycle will repeat. Near the ground, the glider might make a "normal landing" or it might stick itself in the ground, like a "JART" ( Lawn Dart ), depending on where it happens to be during the "cycle".

SOLUTION : Remove nose weight, until the glider has a stable, level glide at SLOW airspeed.

Dave F.
 
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@Roz Rocketz Ron I don't know if you've flown yours yet, but I came across the CG location stipulated for the original Estes SWT. It's between 8.75" - 9.0" from the rear of the main body tube.View attachment 514508
No, I'm in Washington state visiting family. Was launching rockets with Bernard and Ken at 60 Acres park on Thursday. I thought about bringing the Scissor with me to take advantage of the large field but would have to carry it on the plane and likely to damage it along the way.

Thanks for the info. What's interesting about the picture above is that the new kit has a plugged NC so not able to insert the clay to the tip. I glued some clay to the plug. I haven't tried it again but will when I return.

1650179019920.png
 

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Super cool video and great flight. I'll have to say, though, that at the beginning of the video, seeing cars parked on the edge of the road and you quickly (due to daylight) setting up on the pad (shaky camera and all), I kept waiting to hear "Bad boys, bad boys, whacha gonna do" and then the COPS splash screen pop up. I'm probably the only person ever to see that, but now that I've said that and if rocketry was an illicit pursuit, does it at least fit when you watch it a second time? The angel at the end handing out flowers was obviously amazing, but what a great ride for the video. Quite the character arch and a great flight!!!

Sandy.
 
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Wow, great to see that it actually works! Not a competition glider, but who cares, it's all about its uniqueness and looks. Still amazed to see that it has enough roll stability not to get into a death spiral. That said, I'd only fly it on single-digit (or zero) wind days to be safe.
 
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That may induce a spiral . . . I think that, the smaller the turning radius, the higher the likelihood of a spiral developing.

Dave F.
Indeed. That has been a continuous debate. We've had gliders float away from the park, never to be seen again. I don't want it landing on the gym like my Orbital Transport. Friday should be low wind so planning to try it then. The Scissor Wing will need to earn its decals.
 
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Indeed. That has been a continuous debate. We've had gliders float away from the park, never to be seen again. I don't want it landing on the gym like my Orbital Transport. Friday should be low wind so planning to try it then. The Scissor Wing will need to earn its decals.
Were you able to get your SWT up in the air? 😛
 
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