Fat Boy w/ 24mm MMT Build

Discussion in 'Low Power Rocketry (LPR)' started by bmhiii, Nov 9, 2002.

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  1. Nov 9, 2002 #1

    bmhiii

    bmhiii

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    I have always built all my rockets "stock" by the instructions until I started reading this forum. This has lead me to build an Estes Fat Boy with a 24 mm MMT. I know this isn't radical to most everybody in the forum, but it is for me.

    To start, I bought a Fat Boy kit and a D/E motor mount kit. Since the MMT kit came with "E" capabilities, I decide to build the Fat Boy to fly on "E" engines. I can use an adaptor to fly "D" and even 18 mm engines.

    I've been working on this model off and on for a month or so and have documented it with pics.

    I also used some strengthening techniques that I thought of after reading this forum. I haven't read anyone doing exactly what I did, so maybe I've come up with a bad idea. But what the heck.... More on this later.

    Here's a pic of the kit:
     
  2. Nov 9, 2002 #2

    bmhiii

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    I knew I wanted to build the Fat Boy with extra strength to fly bigger engines even though I might not need to. This build is became an experiment to me.

    The strengthening technique I thought of was "glassing" certain parts with nylon panty hose and CyA.

    For the centering rings, I stetched a peice of the nylon over one side then put on a coat of thin CyA. After that dried, I put on another coat. Repeated for all sides of the centering rings.

    Here's a pic:
     
  3. Nov 9, 2002 #3

    PGerringer

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    Dude, it is about as radical as they come... Taking an Estes D-E (which is a low E indeed) and making it capable of Aerotech Fs... Man that is cool. You may need to ditch the balsa wood and replace it with craft plywood or something stronger than balsa. I would definitely glass the whole thing. Good luck, can't wait to see her in action.. :D
     
  4. Nov 9, 2002 #4

    bmhiii

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    I just realized that I forgot to attach the Fat Boy kit picture to my first post.

    Let's try this again.
     
  5. Nov 9, 2002 #5

    bmhiii

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    Next came the motor mount. Nothing special except the "glassed" centering rings and good fillets.

    I also made my first mistake here. Since the Fat Boy has throught the wall fins, I should have built the MMT without attaching the rear centering ring. This would have allowed me attach the MMT, apply internal fillets to the fins and then I could have attached the rear centering ring. But I forgot, so no internal fillets.

    Here's the pic:
     
  6. Nov 9, 2002 #6

    Mike

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    Looks good Bmhiii,

    Out of interest, what are the centering rings made of?

    I'm unfamiliar with MMT kits (they don't exist in the UK)
     
  7. Nov 9, 2002 #7

    bmhiii

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    I have been experimenting a little with balsa wood scraps on how to stengthen fins. I really need stronger fins on the Fat Boy cause who knows what it's going to fly like and what kind of stuff Murphy will thow at me. Also, the balsa in this kit seemed extremely soft.

    So, I went to the "glassing" technique described earlier. I sanded the fins smooth but did not sand the edges. Maybe I should have, I don't know. I probably will the next time I use this technique. I layed a fin down on an overturned little box, cut a piece of the nylon, stretched it over the fin and taped it down. Next was a coat of thin CyA. I let it dry, then did another coat. After that, I trimmed the edges with a Xacto knife. Then repeated for the other side and the other fins.

    When experiementing with this "glass" thing, I did a one inch square of balsa. When done, I had a piece of balsa that was super stong. My wife could not break it even with the grain.

    The only problem is that I don't know how much weight I've added by doing this. And the technique is a little labor intensive. But what the heck, I'm just playing and came out w/ super strong fins.

    Here's a pic:
     
  8. Nov 9, 2002 #8

    bmhiii

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    Mike,

    The MMT (motor mount kit) is something I bought from Estes. Every rocket comes with one in it's kit. It's the motor mount tube, the engine block and hook, and centering rings of some sort so you can glue it in the rocket. I bought the kit cause I wanted to use a 24mm mount instead of the 18mm mount that came with the kit. If you've built a rocket, you've built a MMT.

    To answer your question, the centering rings are standard Estes white cardbord.

    bmhiii
     
  9. Nov 9, 2002 #9

    bmhiii

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    After I had finished "glassing" the fins, I sanded them down and beveled the edges (except the root edge). I then taped off the through the wall tabs and an 8th of an inch of the fins where my fillets would be. Then I applied a coat of Elmers Fill n Finish, let it dry, sanded it down, apllied another coat, let it dry, and sanded again.

    Here's a pic of the finished fins before tape is taken off:
     
  10. Nov 9, 2002 #10

    bmhiii

    bmhiii

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    Here's another pic of the fins after the tape has been removed.
     
  11. Nov 9, 2002 #11

    bmhiii

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    Next I glued in the MMT. I put a ring of glue (I used Elemer's Wood Glue for everthing except the "glassing", I love the stuff) in the body tube above the fin slots, inserted the first ring of the MMT, put a ring of glue inside the body tube right at the very bottom, then slid the last ring of the MMT in. I applied a fillet of glue on the bottom ring and also put some glue down the inside of the tube from the top to add a little more glue to the top centering ring. Since the Fat Boy's body is so short, I was able to do this.

    Another pic:
     
  12. Nov 9, 2002 #12

    bmhiii

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    Next came the attachment of the fins. This was my first kit with through the wall fins. I liked the TTW fins and it made me think I was working on a "big" rocket.

    Let me back up a little. Since I used a 24mm MMT, the fin tabs were too long. I measured and trimmed of an 8th inch or so of the tab before "glassing" the fins a few steps back.

    The fin slots in the body were a little narrow for my "glassed" fins so I used a little file (an emory board woud work) to open them up a bit. I did a lot of dry fitting before gluing in the fins. I put Elmer's glue on the root edge with a little drop of CyA and attached the first fin. After five minutes or so, I attached the other fins. I the let it sit overnight.

    Now was fillet time. I used Elmer's wood glue and applied about 5 or 6 coats for each fillet over the next day or so.

    Another pic:
     
  13. Nov 9, 2002 #13

    bmhiii

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    The rocket is done and ready for paint. I have a log jam in the paint booth so don't know when I'll get to painting the Fat Boy. I plan to paint it stock, I'm one of those who likes to make it look like the picture on the box.

    One other thing I did with this rocket was to use kevlar string for shock cord attachment. After I had built the MMT, I drilled a little whole in the upper centering ring with a Xacto knife. I then tied a piece of kevlar around the motor mount and fed it up throught the drilled whole. I will have enough kevlar to go to the top of the body tube and tie a loop in it. I will then attach a long piece of elastic (I use sewing elastic and one size bigger than the Estes supplied cord).

    So that's about the whole deal, it was a fun build. It was also neat in that I was documenting the build with pictures just so I could post this string. I've had a blast and thanks for bearing with me on this post.

    Comments and constructive criticism are most welcome!
     
  14. Nov 9, 2002 #14

    Milo

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    Looking good bmhiii.... showing some skill there.
     
  15. Nov 9, 2002 #15

    sandman

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    Actually, this thing looks plenty strong. You could use an AT E14-7 SU motor or maybe something even an F21 in 24mm (if you can find one).

    The fins are short and stubby so your strengthening look more than enough to me.

    Just check it for ballance before you fly.

    Looks great so far.

    sandman
     
  16. Nov 9, 2002 #16

    bmhiii

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    Wow, I might have built something that will use "other than Estes" engines some day!! Way cool!!

    I will for sure check the stability before flying. I'm sure I'll need NC weight.

    bmhiii
     
  17. Nov 9, 2002 #17

    KenParker

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    I agree with Milo and Sandman. I am tremendously impressed.

    I think you could even fly it on an F24 24mm RMS.

    Are you coming to The Rocketry Forum event at Whitakers next April? I'd luv to see that FB fly.

    But, like Sandman said.... check your balance. I'm pretty sure you'll need some nose weight if you want to fly the heavier 24mm engines.

    GREAT JOB !!!

    - Ken

    P.S. - I think you're more than ready to build your Level 1 rocket. Choose a kit and get to work !!!
     
  18. Nov 9, 2002 #18

    bmhiii

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    Thanks for the compliments!! Hey, I'm learning, developing skills and having fun all at the same time. Does it get better than that? And it doesn't cost too much... yet!

    I very defintitly will check stability. I'm sure I'll need nosecone weight. I've used clay in the past, any suggestions on added weight?

    Whitakers? Don't know yet. Where is it held?

    Level 1 cert.? It's in the back of my mind, I haven't even done the research yet. I am an NAR member and I did go to a local NAR club launch last month. Kinda making contacts with others in case I decide to certify. Decide... I mean when I certify!

    I have purchased my first mid-powered rocket already. It's an Aerotech Tomahawk. Chosen because it seems Aerotech makes good stuff and it was the lighter of most of it's models allowing me to fly it on smaller engines. I'll begin that build this winter, I imagine. Don't know if I can Level 1 cert. on it.

    I'm having a lot of fun building right now. I have a Big Daddy waiting. I also have a Super Big Bertha that I might try clustering with. (I didn't used to think about building "non stock" till I ran into TRF and all yall!!):D

    And I just today ordered a Duece's Wild! and a Cheetah! from Fliskits for my wife to give me at Christmas.

    So as yall can see, I got plenty of things in the hopper. I'm having a blast!!!

    Keep you stick on the ice...

    bmhiii
     
  19. Nov 9, 2002 #19

    sandman

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    OK I'm here to make trouble...hehehehe!

    The Big Daddy...THAT model just cries out to be converted to "E" power...mine is fantastic on an E9-6 check with flying siverad (he's a member here in the forum) I think he is selling "E" engine hooks. That's all ya need to convert it...an engine hook.

    My Little Brother is making a 2 stage "Double Big Daddy"!

    Don't buy any more motor mount kits...just get the parts...24mm body tubes, centering rings, make some engine blocks (I like engine blocks in all my models) just cut some old spent engines on a bandsaw...they also work as 18mm to 24mm centering rings. We can help ya find supliers.

    Clay works just fine for nose weight...just put a gob of epoxy on top to ho;d it in place...bb's work too.

    Whitikers is in North Carolina, We are meeting in the spring...April.

    Level 1 well, take your time ...no hurry.

    I love my Tomahawk...mine has about ten flights on it and looks like it might need a repaint soon. Don't think I'd use it for level 1...but ya could I guess.

    YES!!! SURE ya could!

    A 3 or four 24mm engine cluster in a Super Big Bertha...H**L YES!!! DO IT!!! We'll help!

    Remember...If the women don't find ya handsome, they can at least find ya handy.

    sandman
     
  20. Nov 10, 2002 #20

    bmhiii

    bmhiii

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    And he can even quote Red Green.:D

    bmhiii
     
  21. Nov 10, 2002 #21

    rstaff3

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    The Fat Boy looks nice bmhii! Interesting techniques too, thanks for sharing. Maybe if we both go to Whittakers you can drag race my G38-powered FB? :D

    sandman...the Big Daddy is Ok on an E9, but it begs for a F21!
     
  22. Nov 10, 2002 #22

    Milo

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    Where does Red Green hang out now-a-days? I have DirecTV and would love to to find what channel he is on.

    That is a great show! :)
     
  23. Nov 10, 2002 #23

    sandman

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    Milo,

    Since he is Canadian...eh! He can be found on the CBC (Canadian Broadcasting Co.)

    Occationally on U.S. PBS stations (his Christmas special holds the record for largest pledge contributions than any other PBS show!)

    I live across Lake Huron from Canada so I get Canadian television reception better than U.S. TV.

    Lucky me.

    sandman
     
  24. Nov 10, 2002 #24

    gerbs4me

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    Looks great:)
     
  25. Nov 10, 2002 #25

    Milo

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    I think I found him on my local PBS on Saturday night at 10:30PM. But it is not the "New" Red Green show. So I'm assuming they are repeats. But that is ok. Now I just have to convince the girlfriend we need to be home by 10:30 on Saturday night. :)
     
  26. Nov 16, 2002 #26

    powderburner

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    Sounds like you really did a super job of up-rating your FatBoy. I did something similar, only I stopped at D-power. I moved my motor mount forward about an inch (to try to help with vehicle c.g. while using a heavier motor) which seems to work fine (no noticeable 'Krushnik' effect). Also did some similar stuff reinforcing the centering rings but I did not do the deluxe job you showed with nylon/ca. Are you planning on penetrating any armored army vehicles?
    I usually just sheet my balsa fins with heavy paper ("cover" weight, or something like that?), creased to fit the leading edge tightly, applied with some thinned yellow glue smeared over the fin surface, sandwiched in some wax paper and an old phone book for a couple days. When dry, I trim the excess paper and sand lightly. I have never had problems with any paper bubbling up and the paper really helps a lot with fin strength and rapid surface finishing. They are very durable unless I target a concrete parking lot.
    The FatBoy sure is a great demo/fun design, and always seems to get the attention (and giggles) of all the kids who come out to watch the launches. I'll bet your M.O.B. is gonna really pop some eyeballs open when it roars off on E's and F's!
    I would sure like to hear some flight reports to know how stable your bird is with those monster engines. Good luck
     
  27. Nov 21, 2002 #27

    powderburner

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    if you have a Michael's MJD in your area, you might check the Sunday paper for coupons (no I'm not a stockholder or anything like that)

    in my town, MJD has been printing a 40% off coupon that is good on one item

    makes the price of a fat boy come out to $10 with tax! not bad!
     
  28. Nov 21, 2002 #28

    MarkABrown

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    With the 50% off coupon that I just used ( ;) ), it came out to $8.25!
     
  29. Nov 23, 2002 #29

    powderburner

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    I used my 50% off coupon to get a $12 Big Daddy!
     
  30. Nov 23, 2002 #30

    MarkABrown

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    Sweeeeet! Our Michaels had the Big Daddys marked up to $39.99 so even with the 50% off coupon, you were still paying normal retail. I'll wait till they come back to reality.
     

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