parachute problems

Discussion in 'Low Power Rocketry (LPR)' started by havoc821, Feb 4, 2003.

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  1. Feb 4, 2003 #1

    havoc821

    havoc821

    havoc821

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    I recently built a rocket from the Estes Designer's Special kit that was 20.5" BT-60 bodytube long and had a ~35" nylon parachute in it. The rocket has two C motors parallel to each other. Because there are no centering rings for the motors aligned like this, I had to make my own. After I glued in the motor mount, I noticed there was still room where the ejection gases could escape, so I cut out a piece of 1/16th" balsa wood that would fit at the bottom of the rocket to prevent the gases from leaking out at ejection. Well, other day when I launched the rocket, the ejection charge fired, but I noticed that the parachute didn't deploy!!:( The rocket fell from about 600 ft. and hit the ground pretty hard. Luckly, the only damage was a slightly dented body tube (pics later). :p I also noticed that the balsa wood at the back didn't do its job with preventing the gases from escaping. The gases made their own way out.....through the back. I don't know if the parachute was too big for the rocket or if the gases escaping didn't deploy the parachute. If anyone has suggestions, please let me know. The RockSim file for this rocket should be included at the bottom.
     
  2. Feb 4, 2003 #2

    jflis

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    a 35" chute in a BT60 may be a bit much...

    I would have to see it, see how it is stitched and what sort of cord it used *and* how you folded it. It *can* be done, but that *is* a possible problem.

    As for the "balsa not doing its job", whenever you do a cluster, you have to be certain of TWO things.

    one, that ALL voids (holes) in the cluster motor tube area are plugged. Balsa could work, if it were thick enough, but even then, after several launches it would tend to burn (and could even cause a burn/fire hazard). I recommend that you either use rings that completely fill the voids and/or you fill all voids with a mixture of glue and tissue paper, plugging the holes tightly.

    TWO (and very important)... Be sure that you plug the ejection (top) end of EACH motor with flame proof recovery wadding. "School of hard knocks" graduate speaking here....

    In the event that only ONE motor in your cluster ignites, the ejection charge of that motor has MORE than enough hot burning particles to ignite the remaining motor(s) BACKWARD.

    this is not good... :)

    hope that helps!

    OH! and welcome to The Rocketry Forum!

    jim
     
  3. Feb 4, 2003 #3

    eugenefl

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    Wow, I've never heard that angle before. <scratches head> Thanks for the tip. I'd hate to burn up a model while under chute!
     
  4. Feb 4, 2003 #4

    Micromeister

    Micromeister

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    the word PLUG is a bit much, all that is needed is a single layer of wadding, I usually "gently" fold the wadding onto the clay cap and hold it in place with a couple tiny pieces of masking tape, just enough to keep it in place while installing in the model.

    Anytime you need to plug possible ejection gas "holes" in the motor mount or centereing ring area at the rear of a model. there are two proven methods,
    1: soak small pieces of wadding in elmor's glue and stuff it into the openings filling the gaps completely.
    2: Same tirck useing 30 minute epoxy to fill the gaps, then apply a "glazing" coat to the bottom to smoothout the business end. See photo note the yellow epoxy fill.

    Guys: I have notice tons of the questions ask in this forum are contained in G Harry Stines book Handbook of model Rocketry. As a reference guide this book will be invaluable to anyone in this great hobby. Mr. Stine is no longer with us but the last edition of his book is still available through NARTS and other places, e-bay constantly has older versions for sale, ANY version will give information needed to be plying this great hobby. I strongly urge everyone to obtain a copy of this reference. Don't be confused by cheap imitations by our buddies at apogee, they are simply not of the same caliber.
     
  5. Feb 4, 2003 #5

    havoc821

    havoc821

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    Thank you very much for your replies. I know the parachute was a bit much, but the rocket only went to ~660 ft. It just looked cool so I thought I would put the chute in the rocket. This was my first cluster rocket, so I guess it was a "live and learn" experience. I might try a thicker piece of wood coated with epoxy to see if that helps. Are the centering rings made for clusters?? Anyways, I'm waiting for my mom to develop my pictures, so I don't know when I can get the pics up because I still have to scan them after they get developed. Thanks.
     
  6. Feb 5, 2003 #6

    sandman

    sandman

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    Buy youself a Fliskit Deuce's Wild and make a pattern from one of the centering ring. (the one with the holes closest together) That should work.

    I don't think Jim will mind if you copy one of his centering rings.
    As long as you buy a kit.:D

    Make it out of lite ply or card stock.

    In the past when I couldn't find thick enough card stock I just glued (laminated) a couple of thinner sheets of card.

    sandman
     
  7. Feb 5, 2003 #7

    jflis

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    oh no! not a problem!

    buy two...

    ...we'll make more...

    :D
     
  8. Feb 5, 2003 #8

    trogdor

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    Micro - I wholeheartedly agree that Stine's book is an absolute must-read for anyone with an interest in model rocketry beyond E2X models... however, I really liked Apogee's book and got some good ideas....but it should still be considered supplementary as Stine's is so good and complete.

    Also, I've NEVER NEVER been able to make a good centering ring without almost cutting a finger off so just pay someone with nicer tools to make them! Balsa machining, LOC, and many others I'm sure (Giant Leap??) can make nicer ones... you know, I really like the newer laser cut ones that came with The Launch Pad kits... always wondered if he'd sell them separately as they're not on the website... BTW anyone know what's up with Chuck Barndt of TLP?? Haven't ordered or anything but hte website seems to have been stale for a long time and I can't seem to find a Nike Hercules plan pak in stock anywhere for a long time....
     
  9. Feb 5, 2003 #9

    Rocketman248

    Rocketman248

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    I was told that he was in very poor health. He was hit by a car or something.
     
  10. Feb 5, 2003 #10

    powderburner

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    I have had good luck using foam-core for CR material. If you can find scraps from someone's project, it doesn't get any cheaper than that, and it only takes a small piece to make a set of rings. If you have to buy it you can get a small sheet at the craft store that will last you nearly forever. It is easy to cut to rough size, it is easy to sand, and it takes white glue very well. I reinforce my mounts with balsa webs between the motor mount and body tube so the CR is not taking the thrust loads.

    But I am perplexed at how anyone can get a 'backwards' ignition in a cluster---that's a new one on me. I never would have suspected that you could ignite the front end of a motor through the clay retaining cap. I can also see that it is just not worth taking the chance, especially since a late ignition like this would ruin everything. Sounds like a good idea to pack extra wadding in the front of each motor, thanks for the tip!
     
  11. Feb 5, 2003 #11

    rbeckey

    rbeckey

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    The foam board I have seen is a semi rigid, .25 inch thick foam covered with paper on both sides. Is this the stuff you guys are using? I can see where it would be easy to cut. Would it be strong enough for D-E engines, or just smaller stuff?
     
  12. Feb 5, 2003 #12

    Micromeister

    Micromeister

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    Towelie:
    If one wants to buy rings that is a choice each can make. I prefer to be as independent and self reliant a modeler as possible. I like being able to complete the project without waiting for parts to arrive, thats why I stock tubes and sheet stocks.
    Making accurate centering rings is not that diffiuclt with a few SIMPLE tools and very little extra time. First to answer one of the other questions, 1/4" foam core or even 14ply showcard stock is great for rings in models powered by single use or clusters into the G range, the 4.5" rings in my 5D cluster crayon are Foam core base and the back of a paper pad cardboard forward ring. I am having trouble understanding the notions we need plywood or these other heavy materials for use in model rockets, the Engineering simply doesn't warrent the need. Following this thinking the next step will be 1/4" fibreglass for D motor rings...this heavy weight stuff is simply rediculous and totally unnecessary in MODEL rocketry though G motor impulse. Let me remind you we are holding these materials together with GLUE, the Bond is what holds our models togather not the strength of the parts. I don't mean to preach but good grief guys come on! If your are having motor mount or ring failures, it isn't the rings its the BOND thats failing.
    On to personal cutting of single motor or cluster rings, all one needs is two or three simple tools. a bow or beam circle cutting compass and a pair of calipers or percision rule. All these items can be purchased from any art supply,craft store or on-line modeling tools supplier. Towelie, in northern virginia, Pearl discount supply in Alexandia is the ticket. Or better yet If you live in the Metor area, come on over, I'll be happy to show you how and let you use my tools and Equipment. If your not already connected to a group, Narhams would be happy to have you join, we hold building sessions at every meeting.
    If you have access to a scroll saw, and a roll of double faced masking tape you can make all the rings you can stack, in the time it takes to layout and cut one. mixing materials and
    thicknesses at the same time. a little sand paper to smooth the edges and your done. It's fairly quick and so easy a child can do it (my son & daughters alway cut their own rings from age 7)
    I guess this all goes back to what I was telling Ctulanko about car machanics; there are machanics that actually fix things and problems or there are the machanics of today that are simply parts changers. If you know how to make it, and choose to buy thats one thing, to never learn how. in my book anyway is just another symptom of our self reliant decline.
     
  13. Feb 5, 2003 #13

    jflis

    jflis

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    FlisKits will be offering laser cut rings in the next week or so (see our parts announcement on our website). Initially, we will be limited in our selection, but this will grow over time. Customer demand will dictate what we carry (well, that and what our kits use *S*)

    initially, we will have the following centering rings:

    5-20
    20-50
    20-55
    20-60
    50-60

    jim
     
  14. Feb 5, 2003 #14

    jflis

    jflis

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    Although that information was provided in my 3-C engine Estes Saturn V model, i either didn't read it or ignored it...

    first launch, 2 motors lit on the way up and one lit on the way down...

    gut a brandy new Saturn V once and learn a life lesson, i'll tell you that :D

    Now, that was in the days of the paper cap. But you can still have this happen with the clay cap. I see it at least once every year or so.

    cheap and easy prevention.
     
  15. Feb 6, 2003 #15

    trogdor

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    Micro - ummmm... I think you did get kinda preachy! BUT I can respect your point of view. I'm that way to varying degrees in other hobbies and endeavors... but I guess I should have clarified a bit and said the particular difficulty is with cluster rings and actually I'm a member of NOVAAR and MDRA but might check out your group and take you up on that offer! I'm always willing to learn a new technique. Really I like the Estes cardboard centering rings (dang wish they didn't discontinue the flat centering ring pack last year) and never have had a problem with repeated 50ns 24mm reload flights... I like nice epoxy filets though... and I don't really care about the weight at all... while I USED to try to optimize everything for absolute maximum performance, I guess I got burned out on that and now just make it look nice as I probably won't be able to tell much of a difference anyway in the flight performance. (Wellllll, I guess it depends on how lax you are but I'm not THAT lax!) and on that subject, I've found that the 10 hour perfect model seems to get lost, crash or suffer some other fate (trees) faster than the 3 hour model.... :( I'm meandering aren't I.... I don't even remember what this thread is about so I'll stop!
     
  16. Feb 6, 2003 #16

    Micromeister

    Micromeister

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    Towelie:
    really am sorry about the preachin..force of habbit, old scoutmaster, yourth church leader..A type:(
    I did mean it about dropping by anytime, my door is alway open to modelers, It's a tinky little place (Townhouse) but we can do/make just about anything ya need. Robert Edmonds can give you my number if your interested.
     
  17. Feb 7, 2003 #17

    trogdor

    trogdor

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    Micro - well I know what its like to not have space! I used to build my rockets on a table sharing my PC when I lived in a condo.. man I still find spray paint dust on old floppies I dig out! Then we moved to a mediumish townhouse and we collected so much crap that I have nowhere to build except on a little fold out table in the rec room in front of the TV where my wife complains (just a little really, but still) about the epoxy fumes and sanding dust! FINALLY in the last week I TOTALLY cleaned out the rather large laundry room, put a rug down and some bulletin boards, a dart board and some shelving along with my table and have a very nice rocket room! Got a super cheap shop light from the nearly defunct KMart down the road and now I'm set, organized all my parts boxes etc... I'm excited for this season, I can actually find all the stuff I've wondered where I left! ok, rambling again....
     

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