RumbleBee-C Build

Discussion in 'Rocket Boosted Gliders' started by Rktman, Jun 19, 2018.

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  1. Aug 13, 2018 #31

    XolveJohn

    XolveJohn

    XolveJohn

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    Will look for that glue. With proper trimming, you should get way more than a minute with a B engine. Remember, you don't have the radio on it, so is lighter and has less drag. Just hope you don't catch a thermal.
     
  2. Aug 13, 2018 #32

    Maxout

    Maxout

    Maxout

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    Normal CA glue works just fine on pultruded CF. I use it all the time. The only time you see it popping loose is when it's used to reinforce a balsa tailboom. Even then, just check it regularly to make sure there aren't any loose spots. No big deal on a rocket, actually, but popped strands do change the trim on hand launched and catapult launched gliders just enough to hurt performance. If it's too big of an issue, a spiral wrap of kevlar tow secured with duco or ambroid is a lightweight option.
     
  3. Aug 13, 2018 #33

    Rktman

    Rktman

    Rktman

    Eric Noguchi

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    3M EC2216 Scotch-Weld epoxy seems to be the best adhesive though expensive ($20 for 43ml from R.S. Hughes or $36.39 for 5.6oz from Amazon). It has high shear strength, remains flexible, & is used for commercial aircraft. Maybe overkill...so of course I'm going try it lol. I like to build for longevity– one reason that, try as I might not to get attached, it still upsets me to lose my gliders, especially great performers like the RBC.
     
    Last edited: Aug 14, 2018
  4. Aug 13, 2018 #34

    Rktman

    Rktman

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    Eric Noguchi

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    Where do you source pultruded CF tubes and are they more expensive? Any downside to using square tubes, as I find them easier to mount flight surfaces on?
     
  5. Aug 13, 2018 #35

    Maxout

    Maxout

    Maxout

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    All of the tubes you're using are pultruded. It's a manufacturing method. They're the most affordable option because they're continuous cross section and hence can be mass produced. The other option are the various molded tubes, a process reserved for super light tubes and those of nonuniform cross section, such as tapered tailbooms. So a good quality 1/4" pultruded arrow shaft might be $5 (I've gotten as low as $2.50 for reasonable quality), whereas a tapered boom in that diameter range will start at $12 and go up from there (see goodwinds.com). This is one of the reason I have been very careful to only offer kits that work with pultruded carbon. The startup cost for anything molded is too high at this point (and I just spent $400 renewing my web hosting. :( ).
     
  6. Aug 13, 2018 #36

    XolveJohn

    XolveJohn

    XolveJohn

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    You should try 1&1 hosting, only about $140 a year. And the simple editing program is so easy even I can run it, a computer klutz. Brought up in the DOS days, no wonder I hate the damn things. Now if you have a fancy shopping cart and stuff it may cost more, I just use paypal buttons.

    A pal building RG's for the World Team is having the gluing problem.
    I have not verified this problem, but will pass all these tips along to him.

    It does seem like any glue does not penetrate into CF like it does in wood, but I see many people gluing to it, maybe he was using crummy glue, or too much accel, or something. Humidity or greasy fingers, who knows.

    NEW THOUGHT. He is using really skinny RODS I think, only for mini-A motors. I bet deformation
    or bending of the rod cracks the joint. If so, he should use a tube type rod. I sent him this thread ref. May get some feedback.
     
    Last edited: Aug 14, 2018
  7. Aug 14, 2018 #37

    Rktman

    Rktman

    Rktman

    Eric Noguchi

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    I've read that you also have to thoroughly clean carbon fiber rods of any oils, grease or manufacturing residue if you want a good adhesive bond. Alcohol seems to be a preferred cleaner for CF. I rough up the surface with sandpaper first to give it some "tooth" for the adhesive to grab onto (which by default removes any residues that may be on the rod).
     
  8. Aug 14, 2018 #38

    Rktman

    Rktman

    Rktman

    Eric Noguchi

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    IMG_1983.JPG
    Roughing out the airfoil. Getting good practice with the feel and technique of the David Combi razor plane. Very happy with the tissue-thin curls I can shave off, though the left wing proved to be a little more stubborn. Guess it depends on the grain and hardness of the balsa since I had to adjust for a hair deeper cut to make any headway.

    Now I know why I hated having to airfoil anything using only sandpaper; this cuts the time down by at least half. I’ll be using the sandpaper only to fine tune the curves. A good plane is such a worthwhile investment in terms of time saved. I’ll probably tissue the wings to add color and re-strengthen them after removing all that balsa.
     
    Last edited: Aug 15, 2018
  9. Aug 14, 2018 #39

    XolveJohn

    XolveJohn

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    So you gave up on dying? Seemed cool, although messy and troublesome.

    Yes, cleaning CF and sanding sounds good.
     
  10. Aug 15, 2018 #40

    Rktman

    Rktman

    Rktman

    Eric Noguchi

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    I kinda had a hunch that getting a good airfoil might remove enough balsa that I might not be able to use a larger motor if I ever wanted to. Sure enough my airfoil turned out great but left the wings "floppy". The tissue won't really add any weight and the thinned out dope's weight penalty is negligible too but they really add a lot of strength. The color won't be as bright/deep but that's okay, I kinda like the look of wood under semitransparent color.

    Re: the basswood fuselage boom, I should have known that's what it was. I usually recognize it by the tighter/finer grain, and remember wondering how a balsa boom of those dimensions could be so strong. That should've been the tip off but I guess I was more focused on getting it built and up in the air.

    Kinda anxious to see how this version flies too, though this time I'll wait to maiden it at my club's much larger flying field instead of my usual thermal-laden park with its appetite for gliders.
     
  11. Aug 15, 2018 #41

    XolveJohn

    XolveJohn

    XolveJohn

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    Yes, the 3/32 thick balsa could be a challenge to airfoil. HLG wings are normally 1/4", gives you more to work with. Here is a somewhat mind numbing ref on Ancient HLG Secrets:

    http://www.modelresearchlabs.com/legacy.htm

    The plane shaver is new to me, wish I knew about it long ago. Have worn out many a sanding block and paper. Today, foam cores are all the rage, with vacuum bagging and CF skin. Not good for small gliders, and tricky to master. I have done some foam cutting with hot wire, for electric planes. Rocketeers should experiment with foam wings, some manufacturers actually embed CF tubes in them when molding. And HLG, many lessons can be learned about construction and trimming. In the old days, hand launch gliders were used for BG by just adding a rocket pod.

    A caution on the carbon booms, early RBG protos had problems with the 18mm engine ejections, were like a shot gun, and imparted enough force to the airframe to knock off the pod and sometimes the wing. Why I added 1/64" ply reinforce to the pylon. And the 1/4" hole in the pod to vent some gasses. It might be helpful to only use 1/2 the ejection charge, they really are too powerful. Mqke sure your joints are strong, perhaps reinforce with thin fiberglass.
     
  12. Aug 15, 2018 #42

    Rktman

    Rktman

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    Eric Noguchi

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    1st flight will definitely be with an A booster motor. If I feel comfortable enough with the size of our field I'll try going with a half ejection charge on a B or C, thanks for the reminder.

    Due to the lousy weather I haven't even had a chance to try out my Champ, but once I feel proficient enough I want to try some Dynasoar RC models. Vacuum bagging and skinning with CF is a bit too expensive, time consuming and messy to interest me since I'm not into competition flying. But who knows? Never imagined I'd someday get back into rocketry either.
     
  13. Aug 17, 2018 #43

    Rktman

    Rktman

    Rktman

    Eric Noguchi

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    Finishing up the last of the tissuing. Just a coat of dope and the flying surfaces are done. Pretty happy that the color is real close to the dye job on the previous model.

    IMG_1987.JPG
     
  14. Aug 18, 2018 #44

    BABAR

    BABAR

    BABAR

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    Eric

    Nice build

    I like the dye job, I am curious as to whether the soaked balsa grain swells up and when dries becomes a bit coarser (more coarse?). My first thought was you can’t sand it after you dye it, but maybe if dye penetrates deep enough, you can sand it smooth AFTER dying and still retain that bold even color. Obviously flew well. So point may be moot.

    A zero delay engine will eject just fine. May be an interesting deployment, as without the delay the rocket will be at full velocity when engine kicks (as opposed to slowing a bit during delay from standard engine.). My guess is it will probably do a loop, should be cool.
     
  15. Aug 18, 2018 #45

    Rktman

    Rktman

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    Eric Noguchi

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    It does seem to get slightly coarser, and I'm wondering if some 2000 grit sandpaper could be used to "polish" it smoother if one were competition flying and wanted every last bit of altitude? I just fly for sport so it doesn't really affect me. If I get lazy I'll use markers, but dying is the next step up in the looks dept (plus you can color everything at once), and while tissuing takes a bit more effort, it really makes for a nice finish and adds a ton of strength (in this case, required since I sanded away a good amount of balsa putting in a nice airfoil).

    As XolveJohn suggested, I have the option of removing 50% of the ejection charge if I opt to go with a larger motor. It's going to be interesting to see what happens with a booster engine. I'd be way more concerned if the glider were a swing wing, slide wing, scissor-flop etc. since it would be hard on the glider to deploy wings at full speed.
     
  16. Aug 19, 2018 #46

    BABAR

    BABAR

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    I would like to know if the dye goes deep enough that you can sand AFTER dying.

    I have flown versions of astron falcon boost glider and the ejection charge has broken the spar. Never tried scraping out part of ejection charge. I'd be afraid I would mess it up.

    When you tissue the balsa does it leave surface smooth or does it require finishing and sanding?
     
  17. Aug 19, 2018 #47

    Rktman

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    Eric Noguchi

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    Nope the dye doesn't penetrate deep enough to allow sanding the surface smoother without the lighter balsa color showing through.

    I don't sand the final layer of dope (I use Minwax brushing lacquer—the odor is less suffocating) but use 400 grit on the initial layers to smooth it out and give it some "tooth" for the next coat. The final coat will be somewhat glossy but it won't be mirror smooth. It'll look slick, like balsa that's been surfaced with something. The only way to get balsa absolutely smooth is to use sanding sealer—lots of it—and that means weight. I like the look of the wood grain showing through though, especially if it's tinted by the color of the tissue.
     
  18. Aug 23, 2018 #48

    Rktman

    Rktman

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    Eric Noguchi

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    Just a quick update; it's taking awhile because I had to trash both wings and make new ones.
    I underestimated just how much the humidity here can affect balsa. Was putting in the dihedral on the wings on the screened in porch out back and stepped away for just 15 minutes to vacuum up the balsa dust in the build room. When I came back the wings had turned into bright orange potato chips. The 87% humidity had apparently sneaked in through the unsealed wing roots and curled them badly...so badly that nothing I could do would permanently flatten them. :mad:

    Lesson learned, listen to that little voice called common sense next time (my fault, got lazy and didn't bring them indoors like I knew I should've). Oh well, I'm getting real good practice airfoiling thin balsa and after this build I've got my tissuing method down to a real science—no more wrinkles and no more having to shrink it to fit, so some good came out of this re-do. :)
     
  19. Aug 23, 2018 #49

    XolveJohn

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    You might want to put a dehumidifier in your build room!

    I have lost some balsa from not storing right. Wrap the stack with rubber bands, seems to help. Trying to flatten warped wood by putting weights on does not seem to help. Also,use Sig lite-coat clear dope.

    The HLG guys would yell at you for airfoiling such thin wood.
    They use at least 1/4" thick. But that won't fly on an A motor.
     
  20. Aug 24, 2018 #50

    Rktman

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    Eric Noguchi

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    I only ran into the problem because silly me, I went outside where the humidity was ridiculously high. I don't really have any problems indoors because it gets so hot here we have to keep the house air-conditioned so the air is dry enough that I don't have storage problems.

    I find it's hard to imagine that the original builder / designer of the Bumble Bee airfoiled 1/16" balsa. I'd think it'd make it too fragile for more than a flight or 2. The thinnest I've ever airfoiled was 3/32" on another scratch build, which was easier because it was a high aspect wing. Just curious to see what difference it makes on this build if any.

    I'll probably go back to using a B motor with part of the ejection charge scrapped out. Any recommendations for what I can use for that that's non-metal?
     
  21. Aug 24, 2018 #51

    XolveJohn

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    I have never had a problem using a 1/8" flat screwdriver. There is nothing to create sparks. Just dig in and dump it out, one half or a little more. The delay train top is hard and you can't hurt it.

    The BumbleBee was only 1/2A engine, so 1/16" wood was fine.
     
  22. Nov 8, 2018 #52

    milehigh

    milehigh

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    Very nice glider build.
    Just make sure you do have that good sized field to launch with a B engine. Especially if there's any kind of thermal action going on. Back in the day many folks used to experience fly-aways with the original well-trimmed Bumblebees on mere 1/2A motors!
     
  23. Nov 8, 2018 #53

    Rktman

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    Eric Noguchi

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    Thanks! Weather permitting I'll be headed for a 3,800 acre farm field next weekend. Forecast is for 30mph gusts so I may even go with an A engine to keep it within sight. Will post results.
     
  24. Nov 12, 2018 at 7:41 PM #54

    Rktman

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    Eric Noguchi

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    Just got through removing about half the ejection charge. Just as you said, very easily done, the delay charge is hard enough not to be affected by the scraping, I still have all my fingers and didn't burn down anything. Anxious to try out both the A8-0 and, winds permitting, the B with the half charge this weekend.
     

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