Estes Bomarc Clone CG Question

Discussion in 'Low Power Rocketry (LPR)' started by Huckbin, Jan 3, 2019.

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  1. Jan 3, 2019 #1

    Huckbin

    Huckbin

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    Hi everyone, I am relatively new to the forum but am amazed and impressed by the content and discussion being brought forward (and it has helped this BAR tremendously)!!!

    Quick question for folks with Estes Bomarc (0657) experience. I am attempting a Bomarc clone (below) and will attempt a CG/CP assessment prior to flying but am curious what quantity or amount of nose weight (in grams) has generally been recommended for this design (understanding that varied construction and parts can influence the ultimate CG/CP and nose weight required). I would really like to avoid a "lawn dart" if possible. Any information or recommendations are greatly appreciated!!! 48394401_571609213262352_2289405593846284288_n.jpg Thank you in advance, Huckbin (Furlong, PA).
     
  2. Jan 3, 2019 #2

    kuririn

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    Instructions say to use the CB-23 clay nose weight, but doesn't say how much it weighs. However, it does say that the model should balance at least 1/4" ahead of the front wing, without engine. I would verify stability with OR, Rocksim, or swing test. In case you don't already have it, instructions are here:
    http://www.spacemodeling.org/jimz/estes/est0657.pdf
     
  3. Jan 3, 2019 #3

    Huckbin

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    Super...many thanks Kuririn. I will start with the/your recommendation of 1/4" ahead of the front wing (w/o engine) and a swing test. I also would like to upgrade to a D/E power unit but am unsure if this will ultimately affect in flight stability as well (I expect another swing test will help)? I still have an original Bomarc I built back in 79-80 (when I was around 12 yrs) but never attempted to fly the beast - good thing as I am not sure it would have gone vertical :). Thank you again and appreciate your quick reply!!!! Cheers.
     
  4. Jan 3, 2019 #4

    kuririn

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  5. Jan 3, 2019 #5

    Huckbin

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    Hi Kuririn....you have a keen eye!!! Indeed, an upscale (BT-55 with a interceptor nose cone) version of the falcon commander with wing tip pods (still in the works but will keep folks posted). The wings 49504406_351328108995753_3802096305312890880_n.jpg (along with the bomarc) will be reinforced with Deluxe carbon fiber tissue anticipating additional stress due to the forward sweep and wing tip pods. Thanks for asking!! Best, Huckbin.
     
  6. Jan 3, 2019 #6

    Huckbin

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  7. Jan 3, 2019 #7

    kuririn

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    Don't mention it. You have some really nice looking builds going on. Where does one buy deluxe carbon fiber tissue, and what kind of adhesive is used to attach it? I've never used that before.

    Edit: In the "old days" (60's) we used to use gauze and white glue to strengthen fin joints, lock down engine hooks, etc.
     
    Last edited: Jan 3, 2019
  8. Jan 3, 2019 #8

    Huckbin

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  9. Jan 3, 2019 #9

    Huckbin

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    Thanks again Kuririn....I appreciate the kind words!!! I only recently returned to the hobby after about a 40 years hiatus. It's been fun trying out new techniques, upscaling, etc., and just being a little more analytical. Really nice to have forums like rocketryforum and folks like you (and other forum members) making the hobby all the more learning and fun!

    Regarding the carbon fiber tissue....yes, I suppose it's really just a form of "papering". I have also used silkspan for fins but not general papering per se like many folks use. The carbon fiber tissue is available via Tower Hobbies and other online vendors, as well as Ebay (https://www.towerhobbies.com/cgi-bin/wti0001p?&I=LXJLLZ&P=7). When applied with EZE dope, sanding sealer, epoxies, or other water or solvent based solvents it really produces a strong fin. I cannot comment on the relative strength compared to fiberglass, cardstock, copy paper, gauze or other techniques folks use (I can say relative fin strength appears to be higher than a silkspan and EZE dope process). I have found that 1-2 coats of EZE dope after applying the carbon fiber tissue (with EZE dope) following by sanding and then Kilz or related results in a nice grain free and strong surface. The overall weight addition also does not appear to be too substantial. I have also wanted to use the carbon fiber tissue similar to how you and others have used gauze in the past. In the end, it may be overkill (and cost is reasonably above that of other types of paper) for a low power rocket but it's been interesting using the material.

    Again, really appreciate your help and additional discussions. Looking forward to more with you and other forum members in the future!!! Cheers....Huckbin
     
  10. Jan 4, 2019 #10

    Huckbin

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    One last post on the bomarc....here's my 39 year old companion rocket (I cannot even remember making the kit back in the day) 49515839_318224128902525_2840929903468085248_n.jpg . I think some of these old birds will outlive many of us :). Best, H
     
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  11. Jan 6, 2019 #11

    dpower

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    For my clone, the CG is right at the top of the wing, no engine. I've flown it on C11 and D12 motors, for stable, straight up flights.
     
  12. Jan 6, 2019 #12

    Huckbin

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    Dear dpower.....thank you very much!!!

    Very glad to hear that you also have a Bomarc clone that flies on higher power and is stable.

    For some reason, I have never felt comfortable with the notion of B-C engines powering this relatively large model and based on general stability challenges I have read about others flying the Bomarc.

    Another variable I have on my clone are resin ramjet cones that I molded. Weight of the cones is slightly above that of original balsa inlets but I anticipate they could be improved somewhat in terms of aerodynamics.

    Between your information and Kuririn's, I feel much better informed!

    Thank you again and Happy New Year!

    Kevin
    Picture1.jpg
     
    Last edited: Jan 6, 2019
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