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  1. #31
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    Time to rob an old model for radio gear...

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    So far, I has pretty much followed the J&H Aerospace instructions. But I am about to make a hard turn.

    The instructions call for an ultra micro receiver board, such as those for Spektrum radios. But I use Futaba and Tactic radios, and I haven't found a micro receiver board for them.

    So, what is a "ultra micro receiver board"? A roughly 1 inch square circuit board, that has a receiver and servos (and sometimes an ESC) built into it. I will be using micro components, but not quite as small.

    And I have to order another micro servo.

    "Lock S-foils in attack position....."

  2. #32
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    SPECIAL NOTE: The instructions advise that you do NOT paint your model.

    I felt it was more important, for me, to add a light coat of paint to be able to see the model.

    I may regret this. We shall see.

    "Lock S-foils in attack position....."

  3. #33
    Join Date
    22nd September 2014
    Location
    Sacramento, CA
    Posts
    36
    [QUOTE=Crawf56;1785280]Over the years, I have learned that a single color model is difficult to see in the sky. So, I painted the bottom orange.
    And the top is white.

    May I ask what paint you used? And did you determine how much weight was added? I have one of these kits in the queue to start after LDRS.
    Thanks for your build thread.
    William Walby
    AeroPac BOD
    TRA 2904, AeroPac 102
    NAR 60661, ARLISS-801
    Level 3

  4. #34
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    [QUOTE=WFWalby;1785419]
    Quote Originally Posted by Crawf56 View Post
    Over the years, I have learned that a single color model is difficult to see in the sky. So, I painted the bottom orange.
    And the top is white.

    May I ask what paint you used? And did you determine how much weight was added? I have one of these kits in the queue to start after LDRS.
    Thanks for your build thread.
    PAINTS: Used Rust-o-leum "Safety Orange" and Testors "Flat White". I used light coats; just enough to see.

    Edit - I used these paints simply because I already had them.

    WEIGHT: I did not do a 'before & after' weight measure on the painted parts/body. I cannot find an "Overall Weight" of the model listed in the instructions.

    CENTER OF GRAVITY [CG]: I also cannot find where the CG is listed. Although there is a detailed section on testing the model for glide performance.

    I broke my scale a couple of months ago; guess I need to get a new one. In this thread, I will supply my findings on Overall Weight and CG location.
    "Lock S-foils in attack position....."

  5. #35
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    I am using a Tactic radio system, which I do not recommend. It is a good radio system, but Tactic is part of Hobbico, which was recently purchased by Horizon Hobby. Horizon Hobby is the main dealer for Spektrum radio systems, and will likely discontinue Tactic radios. Such is life.

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    Note that the servo is a "micro" TSX1.9; it weighs 1.9 grams. By the way, these are now on backorder.
    "Lock S-foils in attack position....."

  6. #36
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    Let's work on the mount for the servos. Lightly sand the surface.

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    And glued in place with medium CA.

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    "Lock S-foils in attack position....."

  7. #37
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    Attaching the servos, using medium CA.

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    "Lock S-foils in attack position....."

  8. #38
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    Connecting the servo to the micro receiver. I have ordered some servo chord extensions.

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    "Lock S-foils in attack position....."

  9. #39
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    Starting on the control rods, that connect the servos to the rudder and elevator. Man, they are little! Graphite rod with wire z-bends. J&H gives detailed instructions on installing them.

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    Clothes pin with a balsa strip to help hold the rudder in position while I install the pushrods.

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    "Lock S-foils in attack position....."

  10. #40
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    The control rods installed.

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    "Lock S-foils in attack position....."

  11. #41
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    Checking balance. Not horrible, but will probably need nose weight.

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    "Lock S-foils in attack position....."

  12. #42
    Join Date
    28th May 2015
    Posts
    42
    Welp, time for the designer to chime in...

    First off, nice job on your build. It looks great!

    Switchblade XP was my first commercial R/C design and at the time I put it into production, I was quite pleased with it since it was pretty much the only R/C rocket glider kit available that could fly on 13mm engines.

    Unfortunately the XP is really, really marginal on takeoff weight. I can get 40-45 seconds off a piston on an A10-3T, and 30-35 seconds without a piston, but only in calm weather (these do weathercock badly if you don't use a piston). This is the reason I elected to discontinue the kit. Never got any complaints...perhaps my customers were just understanding of how extreme of a design it is, but I just wasn't satisfied with it after two years of flying the design on a regular basis.

    Anyway, I said all that to say this: anything that adds weight over the design specs makes this airplane very difficult to launch successfully. I'm concerned that with your electronics package weighing at least double what mine does (~3g for the pkz brick vs 5.5-6 for multiple rotary servos+external rx) plus the accompanying drag of the additional parts (not trivial at all, much to my chagrin on several occasions). That said, there is a possible solution to all this. Since you need nose weight anyway, contact me through the J&H website and I'll send you an 18mm pod and nosecone that will fit (you said you needed noseweight anyway ).

    Anyone else who runs into weight issues with our kits is also encouraged to do same.

    To those still mourning the fact that we won't restock the XP, we're about to release a replacement that's bigger, better, and actually does launch reliably on 18mm A engines, even without a piston. You're still stuck with Spektrum.

  13. #43
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    Thanks for looking in, Maxout.

    Did you have to add noseweight to your Switchblade-XP? What was the CG location?
    "Lock S-foils in attack position....."

  14. #44
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    OK, ever forward........ POWER.

    Here is my 3.7 volt 70 mAh battery (right) and charger (left). Charger uses a USB port.

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    "Lock S-foils in attack position....."

  15. #45
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    Sorting out the receiver, servo extensions, and servo wires. Using a little tape to help hold the wires. Trying to put stuff where it WON'T get crispy.

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    "Lock S-foils in attack position....."

  16. #46
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    And the battery goes on the other side of the boom/fuselage. Using Velcro to hold stuff.

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    And with the battery in place. I still have to sort out excess wire.

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    "Lock S-foils in attack position....."

  17. #47
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    Did some glide tests, and I was quite surprised by the results. The Center of Gravity [CG] was much further back (from the leading edge of the wing) than I expected.

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    The CG was roughly 1-3/4 inches from the leading edge of the wing, measured at roughly the hinge point on the inner part of the wings. (See the second picture, with the ruler.)

    The bad news is that I am nose heavy. Time to do some component rearranging.
    "Lock S-foils in attack position....."

  18. #48
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    At this point, the overall weight of my Switchblade-XP is 31 grams.

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    Adding my "simulated motor weight", the gliding weight of the model is 35 grams.

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    Next step is to get some motors.
    "Lock S-foils in attack position....."

  19. #49
    Join Date
    28th May 2015
    Posts
    42
    Gary,

    I got your email with contact info this weekend and will get an 18mm pod shipped to you in a couple days.

    You mentioned some things about CG and noseheaviness. As a free flight guy, I tend to design my models with very large tail volume coefficients which allow me to put the CG pretty far aft as you have observed. The numbers you indicate look good and I wouldn't move the CG further back from there. Try adding some up elevator trim and see if that sorts the glide out somewhat. You should be able to get a pretty nice flat glide from your Switchblade after a little bit of trimming work. Please bear in mind that I do not ascribe to the 0-0 wing/stab incidence convention that pervades the rocket gliding community. I prefer setting the CG in a known good location and leaving it there, adjusting glide trim using stab incidence changes. This has worked will for over 80 years in hand launched gliders and even with fixed incidence power free flight models which reach almost 100 mph on the way up (think the Sylph rocket glider, except 70-80" span, just as fast, and powered by a screaming gas engine instead of a rocket). I think the 0-0 myth has done more to damage participation in boost gliders and rocket gliders than any other issue.

    Bottom line, CG looks good, just add up elevator until happy with the glide.

    I wrapped up the testing for a new swing wing R/C model this weekend. 18mm A-C power, considerably larger than the Switchblade. It will eliminate the performance issues I ran into with the Switchblade XP.

  20. #50
    Join Date
    16th August 2016
    Location
    Paragould, Arkansas USA
    Posts
    444
    Very good info. Thanks for looking in.
    "Lock S-foils in attack position....."

  21. #51
    Join Date
    5th March 2017
    Location
    Pittsboro, NC
    Posts
    444
    Quote Originally Posted by Crawf56 View Post
    Be aware that there are some LITTLE parts, which can be a challenge:

    Attachment 344353

    I decided to keep them on a sheet of paper, so I can SEE them!

    Sometimes I'd misplace tiny components or it would pop out of my tweezers when grabbed, so I ended up assembling everything inside a largish plastic storage bin.
    NAR# 103899

    "As I hurtled through space, one thought kept crossing my mind—every part of this rocket was supplied by the lowest bidder".
    — John Glenn, Jr.

  22. #52
    Join Date
    28th May 2015
    Posts
    42
    Quote Originally Posted by Rktman View Post
    Sometimes I'd misplace tiny components or it would pop out of my tweezers when grabbed, so I ended up assembling everything inside a largish plastic storage bin.
    This is a very important point and we're trying to get away from teenie tiny parts on the newer designs. The smallest components on the Fliplock and Swingshot are the plastic wing bearings. Less stuff to install too!

  23. #53
    Join Date
    5th March 2017
    Location
    Pittsboro, NC
    Posts
    444
    Quote Originally Posted by Crawf56 View Post
    Ever forward! (and quickly, when you use CA glue)

    Got the engine pod on:

    Attachment 344431

    And here is the nose cone. That piece of wire is very special, and is secured with kevlar string.

    Attachment 344432

    I fly for sport and have the free flight (non-RC) version--I'm really happy with the glide performance. It hung up there for several minutes on only a 1/2A3-2T.

    Wanted to pass along a tip: the kevlar line that keeps the wings securely folded in launch position may loosen a bit over time. The solution is simply to (gently) bend the nose hook forward to tighten things up.

    NAR# 103899

    "As I hurtled through space, one thought kept crossing my mind—every part of this rocket was supplied by the lowest bidder".
    — John Glenn, Jr.

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