R/C conversion of the 2.6" Estes V2 into a semi scale manned A4b

Discussion in 'Rocket Boosted Gliders' started by tab28682, Dec 17, 2014.

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  1. Jan 15, 2016 #61

    tab28682

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    I just realized I keep forgetting to link a little bit of video from the first flight of the A4b last summer.



    This is a 10 minute compilation of lots of model aircraft flying at SMALL Steps 2015 in Little Rock last June. There are some rocket scenes at the following points in the video:

    1:39 Launch of my InteR/Ceptor on an E6
    3:16 Launch of the A4b on an Estes E12, The video guy only got about half the glide.
    4:37 Launch of a normal rocket...my NCR Eliminator on an AT G40. Not a bad spot landing on that flight......
    8:24 Piggyback air drop and air start of my buddies Klingberg Rocket Wing. I am flying the wing. Mothership is an Eflite Apprentice. The video guy lost it when the rapid boost and climb started.

    I am flying at least 12 of the other airplanes in the video......:)
     
    Last edited: Jan 15, 2016
  2. Jan 31, 2016 #62

    ewg1967

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    I for one would love to see this!
     
  3. Jan 31, 2016 #63

    tab28682

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    Like I said, I would not hold my breath.....:) Color me insanely busy with work and family and stuff and I want to spend my limited free time building my stuff.

    In any case, the detailed dimensions in post number 60 in this thread should make it quite easy for any modeler to recreate this project on their own, with a minimal amount of effort.
     
  4. Feb 29, 2016 #64

    aerostadt

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    I'm studying Tom's posts and taking my time on this. I bought a T50-34 tube from Balsa Machining Service, which is really the same as an Estes BT-50, and a T52-34 tube from BMS. These tubes slide together and will make the pop-pod arrangement. I got several HXT500 servo's from Hobby King (they are pretty cheap), which looks very similar to the HS-55 (Hi-Tec) servo's that Frank uses. I was lucky to have a short heavy cardboard tube in my inventory that slides into the Estes 2.6" dia. tube. This made it easy to cut out the wing slots and the hatches in the 2.6" dia. tube. I took Tom's advice and have attached a small piece of (CA reinforced balsa) to the center tube to strengthen the 2.6" dia. tube. This small piece of balsa will go between the 2 hatches.

    IMG_3574.jpg IMG_3576.jpg IMG_3578.jpg
     
  5. Feb 29, 2016 #65

    TheTellurian

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    Good work! Thanks for posting and please continue. You have shown things I was unaware of and would have had to McGiver on my own.


    Richard
     
  6. Mar 1, 2016 #66

    aerostadt

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    I'm at the point where it is about time to glue in the wings and the mid-section pieces. I thought about not doing this, so I could see how the servo and push rod go together, but I think that things are too loose. I slightly increased the size of the rear bulkhead holes where the push rod goes before sealing things up.

    IMG_3580.jpg

    Also, I added about 1/16" balsa strips to each wing TTW tab with super glue gel to better increase the contact with the inner tube. I sanded the this strip a little bit after attaching trying to get a good fit with the inner tube and the outer 2.6" dia. tube.

    IMG_3579.jpg

    I cut several strips of 1/64" ply and attached them to the inside of the hatches to help hold the hatch lids in place.

    IMG_3581.jpg IMG_3582.jpg IMG_3583.jpg

    I made a note about where Tom drilled a hole in the plastic boat tail for the push rod to exit towards the elevon, but decided not to drill now. It's time to glue up the mid-section.
     
  7. Mar 8, 2016 #67

    aerostadt

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    I got a balsa cockpit from The Sandman at Roachwerks. It looks very good!

    The wings have been attached and I glued in a small block of wood on the motor mount tube. I still need to put in the one remaining cardboard centering ring that comes with the kit, but that won't weigh too much. The current weight without electronics is 6.45 oz, which is close to what Tom reported. Tom reported 6.75 oz for a glide weight (I don't know if that included electronics).

    IMG_3598.jpg IMG_3599.jpg IMG_3600.jpg

    IMG_3608.jpg IMG_3612.jpg
     
  8. Mar 8, 2016 #68

    tab28682

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    Yep, the 6.75 oz glide weight did include the electronics.
     
  9. Mar 12, 2016 #69

    aerostadt

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    It looks like I'm going to come in a little bit heavy. I will report the weight when the electronics are in. Probably, I used a little too much epoxy and too many finishing coats on the wings and fins.

    I am using the Du-Bro 20" or 30" push rod kit, which has a 0.032" wire, and cutting to the length needed. I found a pair of pliers in my tool box that does a good job of cutting after I tired a pair of wire cutters that were not strong enough. I eye-balled about where I thought Tom drilled his hole for the push rod in the aft boat tail. I found that after drilling the hole perpendicular to the model axis that I need to use a an Xacto knife to carve out the hole a little bit so that the push rod could slide nearly parallel to the model's axis. The carving was followed by drilling at an angle nearly parallel to the body axis. I then found that I could poke the rod through the aft end and after a short trial-and-error was able to thread the push rod through the aft cardboard bulkhead. I could then pull the push rod out the hatch to cut to length and eventually thread through the servo arm.

    IMG_3613.jpg

    I then pulled the push rod out and used a Z-bend pliers to put a bend in the other end of the push rod so that it was in the same direction as the bend in the aft end. I'm showing the Z-bend pliers and the push rod in the attached photo, but the close-up focus on my camera is not good.

    IMG_3616.jpg IMG_3618.jpg
     
    Last edited: Mar 12, 2016
  10. Mar 15, 2016 #70

    aerostadt

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    I bought a 260 mah 2s battery (7.4v) from Hobby King along with a receiver that is the same kind that I am using with Frank Burke's gliders. I found that I can use this receiver along with the same transmitter that I'm using for Frank's gliders. The programmable transmitter can take up to 10 different models. I was going to try to make a mounting feature for the servo's, but there is so little internal room, I finally attached the servo's with 5 minute epoxy. I then hooked up the servo's, bec, battery, and receiver and everything appears to be working fine. I even copied over the settings from one of Frank's model to the A-4b and with a few adjustments, it works.

    IMG_3625.jpg IMG_3626.jpg IMG_3628.jpg
     
  11. Mar 16, 2016 #71

    TheTellurian

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    That's coming along nicely.


    Richard
     
  12. Mar 24, 2016 #72

    aerostadt

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    I found a 1.25" diameter cardboard bulkhead and glued it to the top of the motor mount tube. At that location I have used velcro to attach the battery. The glide weight came in at 8.52 oz., which is heavy compared to Tom's construction. I took some measurements for the glide c.g. The wing chord length at the fuselage is about 6.75" and the c.g. is about 3.125" from the front, which is further back than the 1/3 rule. I could add clay to the nose for the glide configuration, but I am not sure that I want to at the moment. I have started work on the pop-pod tube. I've measured out 1.5 oz and can easily get it towards the front of the pop-pod. I am wondering if I should go to 2 or 3 oz. in the pop-pod.

    IMG_3667.jpg
     
  13. Mar 24, 2016 #73

    burkefj

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    Bob, to reduce weight you can switch to a single cell, dump the bec and go with a smaller amount of lead shot right in the nose, something to consider, might save a bit overall.

    Since your wing has sweep the 1/3 rule at the root wont apply, need to find 25% of mac or stick with what tom used or do glide tests.
     
  14. Mar 24, 2016 #74

    TheTellurian

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  15. Mar 27, 2016 #75

    aerostadt

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    Thanks, Richard, I will look into this. I did notice looking through my notes that George Gassaway also recommended this site to me.

    Thanks, Frank. I will look into this, too. Eliminating the BEC can also make the wiring a little bit simpler. I did find some single cell 100mah batteries in my inventory. I wonder if this would work or is the capacity too small?

    It looks like I can get a RocSim model for the A4b. It's not exact, but may help.
     
  16. Mar 27, 2016 #76

    burkefj

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    You just need to be sure your battery voltage wont droop below 3.7 under load, for one or two flights a 100 may be ok, I'd test it, exercise the servos and see how much capacity is used.
     
  17. Mar 27, 2016 #77

    aerostadt

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    Thanks, Frank.

    I've got some of the RocSim9 models. I downloaded the basic model from Rocket Reviews, which looks like an Estes 2.6" converted to a 29 mm motor. I modified it with some trial and error, so the nose cone, aft end, and aft fins are not perfect, but I think that they will be useful. The weight for a glide model without electronics is in the file label with "1". The weight for a glide model with electronics is in the file label with "2". The glide models weights are close to what I measured with a scale, so I left them. Also, the glide c.g. is close to the location that I measured experimentally.

    A4b with electronics.jpg
     

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    Last edited: Mar 28, 2016
  18. Apr 1, 2016 #78

    aerostadt

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    I ran the Aircraft CG Calculator with rough numbers for the aft fins, which are considered to be the tail in the code. I am attaching the screen save for the results. It shows the glide c.g. to be about have down the root chord or about 3.35". I re-did my experimental glide c.g. and got about 3.5", which is little bit different from the value that I gave in Post #72. All things considered I decided to leave the glide configuration "as is" with the 2-cell battery and bec in-place.

    With the glide configuration established I went back and made a 3rd RockSim9 model (BTW I got an email today from Apogee today, saying that Rocksim9 owners need to re-load Rocksim9 using some special instructions) using a pop-pod weighted on the forward end. I found that it helps to move the Estes E12-4 motor as far forward as conveniently possible. To get a stability margin of one or slightly greater I needed 3 oz. of weight.

    German A4b Glide CG.jpg German A4b Glide Loading.jpg

    German A4b with pop-pod ready for launch.jpg
     

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    Last edited: Apr 1, 2016
  19. Apr 2, 2016 #79

    TheTellurian

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    For general info, the Aircraft CG Calculator is good for ballpark only as it does not account for fuselage effects. The one calibre rule is also flaky with short fat rockets and the V2 is border line there. My experience is as long as the CG for glide is good and for boost, is ahead of that, your golden. If they are the same then you would be simply flying an aircraft vertically on boost. If its behind then it will do what the original did, which was because they didn't put the equivalent weight of the warhead in the nose.

    Keep up the posting I appreciate your efforts.


    Richard
     
  20. Apr 2, 2016 #80

    tab28682

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    All of the above always works well for me for all my rocket gliders and worked particularly well on my A4b model.
     
  21. Apr 6, 2016 #81

    aerostadt

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    Richard, I thought some more about what you said and decided to add more weight to the pop-pod to bring the launch c.g. further ahead of the estimated glide c.g. Naturally, the 3 different methods of stability in Rocksim all improved. The total lead weight on the pop-pod is now 4.55 oz. My feeling is that this is conservative. I've added some pictures to show the pop-pod under construction. This is hodge-podge of tubes to install the lead weight and a space for the parachute. I still need to add an aft section for the motor but the lead weight is shown. The heavy brown tube (I think it is a LOC cardboard launch lug.) in the center photo is used to coil and wrap the lead.

    IMG_3677.jpg IMG_3678.jpg IMG_3683.jpg
     
    Last edited: Apr 6, 2016
  22. Apr 6, 2016 #82

    TheTellurian

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    In this case having more than enough is better than wishing you did. If the maiden boost is solid then some lead can be removed or a larger motor can be used till it gets squirrelly then add some lead back.

    I have the nose and tail cone but have been preoccupied with other [re]builds and appreciate your efforts.


    Richard
     
  23. Apr 27, 2016 #83

    aerostadt

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    In keeping with the current trend, I have gone with the camouflage paint scheme. I noticed that masking the hinge tape does not work well, because in general the paint sticks to the masking tape better than the hinge tape. So, I have one hinge that still needs to be touched up. I used snap rivets to attach the nose cone to the body tube that appears to work well. The project is now pretty much ready to go. Overall, the project looks fairly simple, but I would say that it took longer than I thought it would.

    IMG_3695.jpg IMG_3697.jpg IMG_3698.jpg IMG_3701.jpg

    The pop-pod is completed. I made a few changes from the last post. The parachute is the same one that comes with the Estes kit. The small diameter pop-pod tube (I think it is BT-5) is weak, so I found a brass tube that fits internally just right. I noticed that the Estes 13 mm motor tubes fit in the small diameter tube just right, also, but I did not have any burnt-out 13 mm motors available.

    IMG_3702.jpg IMG_3704.jpg
     
    Last edited: Apr 27, 2016
  24. Apr 27, 2016 #84

    TheTellurian

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    I'm not sure what the 13mm motor tube is for?


    Richard
     
  25. Apr 27, 2016 #85

    aerostadt

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    I had a little bit of damage to the long thin tube (BT-5) that attaches to the 24 mm (inside diameter) tube holds the E12-4 motor. Wrapping the lead coil around the BT-5 tube caused some damage and I had to cut it out and put in some new BT-5. The lead is heavy and the small diameter BT-5 is not very strong. I think with a little bit of bending moment the BT-5 will buckle. Remember the ejection gas goes through the 24 mm tube into the BT-5 to the forward end to eject the pop-pod. I found a brass tube in my inventory that fit just right inside the BT-5. I was looking for an alternative to the brass tube and found that burnt-out 13 mm motors would probably work. I used the brass tube, which I found in a hobby shop several years ago, but others might want to consider something more available. Doing this is probably not completely necessary, but the 3 or 4 ounces of lead on the far end of the pop-pod is heavy.
     
    Last edited: Apr 27, 2016
  26. Apr 27, 2016 #86

    TheTellurian

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    Okay. Thanks. I now understand the use of it.


    Richard
     
  27. May 5, 2016 #87

    aerostadt

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    I've applied Iron Cross decals that I got from Mark at Sticker Shock. I am thinking that my camouflage colors are lighter than Tom's and others, so perhaps this German A4b is the Africa Corps version.

    IMG_3723.jpg IMG_3725.jpg IMG_3727.jpg
     
  28. May 22, 2017 #88

    aerostadt

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    I finally flew this model last Saturday on an E12-4. Winds were calm at the club launch site almost all day. (Must resist urge to fly on windy days. Must resist.) I changed the launch lugs last week to use a 1/4" rod. The model flew good with no damage, but I found out afterwards that the model did not work exactly as intended. I could not get the Spektrum receiver to fit in the A4b, so I used the orane set-up. The input wires go in perpendicular to the Spektrum receiver and this does not give enough room. The model boosted straight up and when the pop-pod was activated it went into a glide immediately. It seemed like it was having trouble gliding, so I gave the full trim for nose up. When we finally got to the model, we found that the pop-pod did not eject all the way and the motor was missing. Evidentally, the ejection charge partially ejected both the pop-pod and the E12-4 motor. The club president and I speculated that the forward weight of pop-pod was moved backward so that it was centered right over the wing right about where it is supposed to be. I will try to find a way to better retain the motor for the next flight. All the tubes are so tight fitting there is no room for an engine hook.


    IMG_4338.jpg IMG_4340.jpg IMG_4341.jpg
     
  29. May 22, 2017 #89

    Daddyisabar

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    Very Cool!
     
  30. May 23, 2017 #90

    Crawf56

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    VUNDERBAR!!! :wink:
     

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