TRF Summer Build Off: The Ellipse

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Did you shake it with verve? :wink:
Verve and vigor both. I believe this can is done for. The question now is, how do you safely dispose of a full rattle can? When they're empty of paint you can just let all the pressure out, but this thing is all sealed up. Actually, I have a plan:

  1. Position a small nail in the nipple.
  2. Fasten a piece of cardboard over the head of the nail.
  3. Wrap the can in a plastic bag, sealed but not sealed well.
  4. Place another piece of cardboard over the nail head, on the outside of the bag.
  5. Drive the nail into the can.
  6. Paint and propellant will vent, which is why the bag mustn't be too well sealed. (No bursting balloons.)
Am I overthinking this? A little? D'ya think? :wink:
 
Verve and vigor both. I believe this can is done for. The question now is, how do you safely dispose of a full rattle can? When they're empty of paint you can just let all the pressure out, but this thing is all sealed up. Actually, I have a plan:

  1. Position a small nail in the nipple.
  2. Fasten a piece of cardboard over the head of the nail.
  3. Wrap the can in a plastic bag, sealed but not sealed well.
  4. Place another piece of cardboard over the nail head, on the outside of the bag.
  5. Drive the nail into the can.
  6. Paint and propellant will vent, which is why the bag mustn't be too well sealed. (No bursting balloons.)
Am I overthinking this? A little? D'ya think? :wink:

You should probably do an internet search, but I've pondered this myself a few times.

I was thinking of using one of those old can punches (the one with the triangular sharp head) and trying to slooowly pierce near the top (having the tool grip under the rim) a tiny hole to let the propellant vent out. In this case you wouldn't shake and would actually let the can sit for a bit so the paint can settle at the bottom, hoping that only the propellant would vent (maybe even refrigerate the can...sounds like a lot of work though).
0047174.jpg


Of note is that the nail in where the nozzle goes sounds like it can be very unpleasant and messy. :wink:
 
When I was 14, I got a facefull of paint including in my eyes doing this very thing. Whatever you try, use safety glasses just in case.
 
Yeah, good point that, if I pierce it at all, I should do so anywhere except through the nipple. And I could just take it to the dump, but I don't like the idea of tossing a pressurized, potentially hazardous can to unsuspecting workers. I'll figure something out.
 
I researched a bit on YouTube about clearing a clogged can and while two people mentioned using pressurized air (compressor or bike pump along with an old tire valve), there were some who said they got a face full of paint, so I wouldn't reco it without a face shield. :wink:

Regardless, here's a very informative video on spray cans and also how best to prevent a clog (note that my suggestion for clearing doesn't work if the paint is made to spray in multiple directions):
[video=youtube;f2tJBeKTikw]https://www.youtube.com/watch?v=f2tJBeKTikw[/video]
 
Thanks a lot for that. I had already given up, and this is well above and beyond. (And yes, it is a "spray any direction" can.)
 
We have a disposal container for buzz bombs at work that is very simple to use that punctures and drains the cans but it is made from some pretty heavy duty stuff to protect the user from a ruptured can. If you like, I'll post a picture of it next week.
 
Thanks, but I think we've beaten this distracting tangent to death and beyond.

Here's a brief update: I've been painting, sanding, filling, painting, sanding, etc. for some days now. Yesterday I had the rocket on a stand in the car port and it blew over, breaking two fins loose. They're reattached, but those two fins' fillets are a bit messed up. Yarg!

And I now have a goal. Gary intends to have his magic dart flying at the ROSCO launch near Camden, SC in four weeks, so I've decided to have this puppy ready and meet him there. Even with this set back, four week is plenty of time.
 
More layers of paint have been applied. I mentioned earlier that I couldn't make enough further progress on filling the tube's flaws to be worth it, so the time had come to let it go. Well, as we all know, that first coat of primer highlights flaws, and in this case it highlighted several places where a little more work could yield big improvements, so I've filled those and sanded and sprayed and sanded and filled just a little bit more, really this time, just a little, and sanded and sprayed, and I swear no more filling after this last little bit, and sanded and sprayed...

OK, now I really am done filling, and after one more primer coat I'll be ready for color, just as soon as I decide what color(s) to use. I'd post pictures, but they'd all be basically the same and really boring.

I've also installed nose weight; that was a little interesting, so I'll post a picture and say more later, but it's almost dinner time. Swing test and the first color coat(s) should be done this weekend.
 
OK, here's the late promised update.

I don't really know where the CP is on this thing. I made two RockSim models, one viewing the skinny side of the body tube nose cone, and the other the fat side, the fins the same. Of course, the fat view has the lower CP; the cardboard cutout in one's head make that much obvious, but I did them both all the same. So, what I've done is use that figure as the assumed CP for the actual build. Based on that, and also using the fat diameter as one caliber, I need at least two ounces of nose weight. Ouch. Obviously, I should have made those fins a bit bigger, but my sims at that point were not well enough developed (and I thought they were) and it's also two inches shorter than the original design.

To make matters a bit more complicated, I can't readily get to the inside of the nose cone, as I don't want to cut the bottom of the shoulder. I went to a lot of trouble designing in a clever shock chord attachment, and I don't want to lose it. So, I put the "nose weight" in the body tube, sitting on the topmost rib, around the parachute tube opening.
Nose Weight.jpg
As you can see, I used the "mix shot with epoxy" method. But you may also see that the "shot" is of very poor quality - shoddy, one might say. That's because all I have for lead is large fishing weights. I took a two ounce weight, suspended it from a clothes hanger above a can of water, and melted it from the bottom up with a torch, giving the shoddy shot you see. Fine quality shot is, of course, unimportant; it all weighs the same. That part worked quite well.

What didn't work so well was placing the lead-epoxy mixture in the tube. It kept falling into the parachute tube. I grabbed an inch long bit of BT-50 scrap (this is why we never throw anything away,) slit it down the side, and stuck it in the top of the parachute tube to keep the lead out. You can see the extra tube in the picture. The extra tube sticks up just high enough to interfere with the nose cone shoulder, but that's OK; assuming it swing tests OK I can rip the extension out. If I need more weight though, I'll have to cut the bottom off the shoulder after all, which would be really ironic.

I've got it painted. Not a great job, but with the difficulty in filling and smoothing the surface that was to be expected. It's also not terrifically creative, as paint schemes have always been my weak area. In the picture, you can see the nose cone is not fully seated, because of the parachute tube extension.
Paint.jpg

Left to do:
  • Swing test.
  • (Hopefully) remove the parachute tube extension.
  • (Hopefully not) cut off the bottom of the nose cone and add more weight.
  • Sand or file the shoulder down a bit more, as it is still too tight a fit.
  • Attach the nose cone and parachute.
  • Test launch on C-11 motors, video optional.
  • Launch and take video on the 13th or 14th at the ROSCO launch. I'm looking forward to meeting Gary and seeing his marvelous Magic Dart.
 
Looking good. With two C11s, it's going to take off quick. What's the final weight?
 
178 grams, without motors, and if I don't need any more nose weight. As Isaid above, the C11's will be a test flight, RS pridicts only about 200 m. I''ll move up do D12's and then E9's if all goes well. 425 m and 657 m preicted respectively. That's based on the wide side view model with the Cd override and a somewhat educated guestimaate of the Cd.
 
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So truly it is said: we learn from our mistakes. Well, I'm learning a lot.

I set up to cut the bottom off of the nose cone so I could add more weight. I even made a little jig to hold it straight and well positioned as I ran it across my table saw. And this is what I got.
Old Cone.jpg
That just doesn't look like enough shoulder. So, I went and got the other one (remember I said I got two of everything in case of screw ups?) and this time I took the bottom off much more slowly but in a mostly fool proof manner. This time I filed a bevel into the corner, and kept filing until the bottom fell out. Actually, when I was almost through I switched to using the corner of the file like a saw, and when that was half done it broke out the rest of the way around. More filing to deburr, and I've got this (with the new shoulder masked for painting and for photo contrast.)
New Cone.jpg
So, there's a setback, but I still have enough time to be ready for the 13th-14th.
 
The Ellipse build is complete. The revised final mass is 240 grams. While I stand by the coolness of this innovative design, I am not too happy with the build quality. Oh, well; it'll fly.
Finished!.jpg
I had planned to get in a test flight on its smallest possible engines (C11) yesterday, but weather and other circumstances conspired against me, so it's virgin flight will be at the ROSCO launch next week.
 
I'm in the same boat my friend! I had visions of a sleek, shiny missle slicing through the sky and I am going to end up with a lumpy, slightly skewed proof of concept that will, eventually lead to an improved version later down the road.

Given the concept that you had, I think that you ended up with a nice build in the time alloted. If your experience has been like mine, you had things that you wanted to do that life just didn't allow time for.

No matter, we tried things that we may have otherwise left floating around in MindSim.
 
...

No matter, we tried things that we may have otherwise left floating around in MindSim.

That's what I'm loving most about the summer build-off. It challenged us to think and brought out some creativity that we normally wouldn't have even attempted otherwise.

In fact, it was until this build in particular that I had not even thought about a non-circular airframe. I still can't wrap my mindsim around exactly how CP is affected in a case like this.
 
The approach mentioned earlier is how many PMC planes are done-evaluate the Cp/Cg in both directions. If both are good, light er up.
 
Yup, that's what I did. I used RockSim and made two files, one looking at the skinny side of the tube and one the wide side, and used the higher CP (which is, or course, the wide view.)
 
Well, the launch on Saturday was a disaster. I brought four rockets in addition to the Ellipse. Before we even introduced ourselves, as I put down my folding chair, the shoulder strap caught two of them and folded them over the rim of the milk crate I had them in. Both are probably repairable.

After the Ellipse flight I tried to launch both my Big Daddy and my Grand Daddy, a modified Big Daddy on which I did my L1 flight. Well, I had no engines for the Grand Daddy with sufficient delays. I prepped the Big Daddy with an E9, and it blew out the nozzle, never lifting an inch. I tried again, with the same result. I had another E9 that I am dead certain was from a different manufacturing lot, but the third time was not the charm as it too blew the nozzle out. That's when I gave up and went home.

So what about the main event, The Ellipse? Here it is on the launch stand, prepped with a D12.
Prepped.jpg
That's The Ellipse on the right, and Gary's Magic Dart on the left. Gary's flight was gorgeous. The Ellipse's assent was perfect. Straight and pretty quick despite the heavy nose weight. It reached nice altitude, arced over, and then the deployment... failed to happen. It came down as straight as it went up, and seemed like it was nearly as fast. From now on, when you look up "smithereens" in the dictionary, you'll see this:
Crash_1.jpgCrash_2.jpgCrash_3.jpg
My friend Scott got video of the takeoff, but very quickly lost sight of the rocket, so we've only got four seconds of video worth posting.
[video]https://youtu.be/3rUfVjLlbhM[/video]

I did figure out the cause. Because of the weight, I had to use a decent sized parachute, a 15 incher. The chute jammed in the stuffer tube that I had added to ensure that the chute wouldn't snag. All I could salvage was the fins and the lumps of lead and epoxy.

If I rebuild using skin over frame again, I will make a modification to the recovery system as follows: I will leave out the stuffer tube and use the fully open ribs all the way up. Before placing the skin over (outside) the ribs, I will place a skin inside the large open ribs to form the parachute compartment. This one doesn't have to be pretty, it only has to keep the chute from snagging. And it will give me a lot more space than a BT-50 to pack the chute.

So, I forget whether or not, by the posted contest rules, this is a DQ. If I'm still in then the take-off video is my official entry.
 
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That hurts!

With 3 weeks left until Labor Day, would it be considered a "repair" if you rebuilt it using the same fins? Either way, I look forward to seeing the rebuild.
 
Although not planned, it was indeed pretty cool that we managed to have both birds on the rack together. Again Joe, my sympathies for your recovery failure. It was a darn good flight though. I still think you could have used less nose weight too. Regardless of what OR or Roc-sim will dictate, my "old school" mind sim said you could afford to loose at least 2 oz and got more altitude. It was great to meet you man.
 
That's a shame. Glad the up part went as planned. Great pad shot.
 
Ouch. :(

At least you got some good shots of it, and one successful boost. And you proved the concept for sure. Look forward to seeing what you do with this in the future.
 
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