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  1. #1
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    Dog Barf. ...How much?

    Two Dog Barf questions...


    how much to use? Does the depth of dog barf vary by body tube diameter Or is the answer something like 1.5 inches depth?

    second..

    can you compress the Dog Barf to take up less space? For example if its 1.5 inches “ loose” and then gets packed to .5 inches?


  2. #2
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    2x the diameter of the body tube is my rule.

    And yes it can be compressed but you run the risk of it being too tight. For LPR and most MPR (smaller diameter mpr's), I use a single sheet of Estes wadding ( or a homemade equivalent) and form a cup for the dog barf before inserting it in the rocket.

    Last edited by rharshberger; 15th November 2017 at 01:12 AM.
    Rich

    NAR# 99154

    L3-4x upscale Estes Cherokee-D- AT M1297W 5/28/2016 http://www.rocketryforum.com/showthr...r-rharshberger

    TriCities Rocketeers NAR section# 736 http://www.tricitiesrocketeers.org/

  3. #3
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    For me, it depend on if I have a chute protector or not. If I do, an inch or two just to keep the direct flame of the chute protector. If there is no protector, I usually go for 1.5 to 2 x BT diameter. In either case, I don't worry if it compresses or not although I don't compress it purposely.
    Handeman

    TRA #09903 L3 3/29/2015

    "If you don't use your head, you have to use your feet!" my Dad

    Tripoli Central Virginia #25 - BattlePark.org

  4. #4
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    Quote Originally Posted by Handeman View Post
    For me, it depend on if I have a chute protector or not. If I do, an inch or two just to keep the direct flame of the chute protector. If there is no protector, I usually go for 1.5 to 2 x BT diameter. In either case, I don't worry if it compresses or not although I don't compress it purposely.
    I am pretty much aligned with the earlier responses. 2x the BT unless I use a separate protector. For up to about 2.5", my favorite method has been to take 1 to 4 sheets of the Quest wadding (about 4" x 4" squares), overlap them, and fold them over a wad of dog barf. I make the ball tight, but one that is able to slide up and down. I have also used the Estes wadding but the Quest slides easier and holds up better to the folding and insertion. You'd be surprised how often I've found the ball near the rocket. At least the ones that used Quest wadding. Usually there is a hole in the bottom but it can generally be reused as is. I stumbled on this more or less by accident.
    Dick Stafford
    The member formerly known as the Pointy-Haired Moderator.
    The Original Rocket Dungeon
    Volunteer compiler of product news for ROCKETS Magazine

  5. #5
    Join Date
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    http://home.earthlink.net/~mebowitz/...A_Launches.pdf



    Quote Originally Posted by spence View Post
    Two Dog Barf questions...


    how much to use? Does the depth of dog barf vary by body tube diameter Or is the answer something like 1.5 inches depth?

    second..

    can you compress the Dog Barf to take up less space? For example if its 1.5 inches “ loose” and then gets packed to .5 inches?

  6. #6
    Join Date
    11th February 2017
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    south Florida
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    "Insert fluffy cellulose to fill 2 to 3 body tube diameters in length"

    Wow, so with a 4" diameter rocket we need 8 to 12 inches of barf? I had no idea so much is needed. Don't think this leaves enough room for chute and shock cord in some of my rockets.

    L1 3/25/17 H135
    L2 8/12/17 J180

  7. #7
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    Quote Originally Posted by billdz View Post
    "Insert fluffy cellulose to fill 2 to 3 body tube diameters in length"

    Wow, so with a 4" diameter rocket we need 8 to 12 inches of barf? I had no idea so much is needed. Don't think this leaves enough room for chute and shock cord in some of my rockets.
    Picture the 4" dia rocket with a thinner amount of cellulose wadding. Now picture the ejection charge going off. It will blow directly through the center of a thin cellulose layer. For large rockets you can use a Nomex sheet or a thicker Estes wadding layer under the cellulose to prevent blowing a hole through it and that will allow use of a thinner cellulose layer.

  8. #8
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    13th June 2014
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    Quote Originally Posted by billdz View Post
    "Insert fluffy cellulose to fill 2 to 3 body tube diameters in length"

    Wow, so with a 4" diameter rocket we need 8 to 12 inches of barf? I had no idea so much is needed. Don't think this leaves enough room for chute and shock cord in some of my rockets.
    That’s why I use Kevlar cord & nomex chute protectors.
    Tim
    L3 NAR 98225

  9. #9
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    I use 1- 2x body diameter, loosely packed, with several sheets of estes wadding laid flat towards the flame. For MP and HP, I always use kevlar line and a nomex burrito for the chute, and the barf keeps the flame off of everything pretty good.

    I find that compressing it, the charge often blows around the edges, not through the center, and it can sometimes form a plug that hampers deployment.

    Loose packed is best.
    ATCS(AW) Tom Keith, USN, ret. _____NAR 99781 L1_____MDRA 212
    SEVRA, NAR 621http://www.sevra.org/ Tripoli East North Carolina (Bayboro), TRA #65, http://ncrockets.org/, MDRA http://www.mdrocketry.org/
    LVL 1 24 October 2015, Leviathan, CTI H133, 2469 ft, Bayboro
    LVL 2 Soon, Super DX3, AT J420 Redline, est 3500 ft, Bayboro or MDRA

  10. #10
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    I find that with a miniature poodle I have to give him two good squeezes, three if it has been a while since he's eaten.

    Edward

  11. #11
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    What about a Standard Poodle?

    Quote Originally Posted by AlphaHybrids View Post
    I find that with a miniature poodle I have to give him two good squeezes, three if it has been a while since he's eaten.

    Edward

  12. #12
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    Poodles make poor wadding.

    Sent from my SAMSUNG-SGH-I337 using Rocketry Forum mobile app
    Dick Stafford
    The member formerly known as the Pointy-Haired Moderator.
    The Original Rocket Dungeon
    Volunteer compiler of product news for ROCKETS Magazine

  13. #13
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    Even Leonard?

    Quote Originally Posted by rstaff3 View Post
    Poodles make poor wadding.

    Sent from my SAMSUNG-SGH-I337 using Rocketry Forum mobile app

  14. #14
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    I made three pumpkin pies for Thanksgiving in 1976, left them on the stove to cool, and then my girlfriend and I drove to invite an old bachelor to eat Thanksgiving dinner with us. Her roommate’s Irish Setter ate one entire pie, crust and all, licked 100% of the filling out of the second, and started on the third before he got sick, all over the house. Projectile vomiting by a loping setter makes a helluva mess. There was easily enough for a Level 3 project, drogue and main both.


    Steve Shannon
    Steve Shannon
    L3CC, TAP, Director, Tripoli Rocketry Association

  15. #15
    Join Date
    5th October 2017
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    101
    Quote Originally Posted by Steve Shannon View Post
    I made three pumpkin pies for Thanksgiving in 1976, left them on the stove to cool, and then my girlfriend and I drove to invite an old bachelor to eat Thanksgiving dinner with us. Her roommate’s Irish Setter ate one entire pie, crust and all, licked 100% of the filling out of the second, and started on the third before he got sick, all over the house. Projectile vomiting by a loping setter makes a helluva mess. There was easily enough for a Level 3 project, drogue and main both.


    Steve Shannon

    ugh....

    ......damn


    lol

  16. #16
    Join Date
    1st October 2014
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    58
    You know you have put too much dog barf in when you see/hear the ejection charge go off and the nose cone stays put on your four inch diameter rocket. As you are pulling the rocket out of the dirt the cone comes off and it looks like you were trying to insulate the entire field as dog barf blows everywhere.

  17. #17
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    Quote Originally Posted by shreadvector View Post
    Picture the 4" dia rocket with a thinner amount of cellulose wadding. Now picture the ejection charge going off. It will blow directly through the center of a thin cellulose layer. For large rockets you can use a Nomex sheet or a thicker Estes wadding layer under the cellulose to prevent blowing a hole through it and that will allow use of a thinner cellulose layer.
    Exactly why I quit using the stuff. Too unreliable with larger tubes - I found also that I had to break up the chunks that had formed otherwise the flame blows past them. Needs to be fluffy to start, and then slightly compressed to form a good seal. I started using Estes wadding to create a better seal and that's when I realized it really isn't a very good solution, at least in my experience.

    By the time you have ruined a couple of good chutes the stuff doesn't seem like such a bargain.


    Tony
    why do people put so much stuff in their sigs?

  18. #18
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    Orange and Black rolls of streamer were on sale last night at the local Vons (Safeway) supermarket. 20 cents a roll.

    I bought all 15 rolls.

    Flame resistant.

    Quote Originally Posted by manixFan View Post
    Exactly why I quit using the stuff. Too unreliable with larger tubes - I found also that I had to break up the chunks that had formed otherwise the flame blows past them. Needs to be fluffy to start, and then slightly compressed to form a good seal. I started using Estes wadding to create a better seal and that's when I realized it really isn't a very good solution, at least in my experience.

    By the time you have ruined a couple of good chutes the stuff doesn't seem like such a bargain.


    Tony

  19. #19
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    Quote Originally Posted by Steve Shannon View Post
    I made three pumpkin pies for Thanksgiving in 1976, left them on the stove to cool, and then my girlfriend and I drove to invite an old bachelor to eat Thanksgiving dinner with us. Her roommate’s Irish Setter ate one entire pie, crust and all, licked 100% of the filling out of the second, and started on the third before he got sick, all over the house. Projectile vomiting by a loping setter makes a helluva mess. There was easily enough for a Level 3 project, drogue and main both.


    Steve Shannon
    Somebody always has to go and ruin a perfectly good thread ....

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067 ---- BARC #028
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  20. #20
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    Quote Originally Posted by Nantucketdink View Post
    You know you have put too much dog barf in when you see/hear the ejection charge go off and the nose cone stays put on your four inch diameter rocket. As you are pulling the rocket out of the dirt the cone comes off and it looks like you were trying to insulate the entire field as dog barf blows everywhere.
    Did you ground test with this amount of dog barf? When this happens either you don't have a good seal and the dog barf provided resistance and your ejection charge gasses went elsewhere, or your ejection charge was undersized to start.

    If you have zero dog barf and use X.XX grams BP with Y.YY volume and have a successful test, then when you add Z.ZZ volume of dog barf you are now pressurizing less volume (Y.YY - Z.ZZ) with the same amount of BP so there will be an increase in internal pressure (due to same amount of gas in less volume) and the nosecone should eject.

    Edward

  21. #21
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    Quote Originally Posted by Bat-mite View Post
    Somebody always has to go and ruin a perfectly good thread ....
    Didn’t do a lot for the carpet either.


    Steve Shannon
    Steve Shannon
    L3CC, TAP, Director, Tripoli Rocketry Association

  22. #22
    Join Date
    1st October 2014
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    58
    Quote Originally Posted by AlphaHybrids View Post
    Did you ground test with this amount of dog barf? When this happens either you don't have a good seal and the dog bairf provided resistance and your ejection charge gasses went elsewhere, or your ejection charge was undersized to start.

    If you have zero dog barf and use X.XX grams BP with Y.YY volume and have a successful test, then when you add Z.ZZ volume of dog barf you are now pressurizing less volume (Y.YY - Z.ZZ) with the same amount of BP so there will be an increase in internal pressure (due to same amount of gas in less volume) and the nosecone should eject.

    Edward
    I haven’t ground tested any motor or charge yet and am only using mid and low power motors. I actually like dog barf on skinnier rockets. Apparently I like it so much I have bits of it all over my house and truck. There is something enjoyable about grabbing handfuls of it out of the bale to put in smaller containers I can’t put into words.

  23. #23
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    Quote Originally Posted by AlphaHybrids View Post
    Did you ground test with this amount of dog barf? When this happens either you don't have a good seal and the dog barf provided resistance and your ejection charge gasses went elsewhere, or your ejection charge was undersized to start.

    If you have zero dog barf and use X.XX grams BP with Y.YY volume and have a successful test, then when you add Z.ZZ volume of dog barf you are now pressurizing less volume (Y.YY - Z.ZZ) with the same amount of BP so there will be an increase in internal pressure (due to same amount of gas in less volume) and the nosecone should eject.

    Edward
    What I've found is that the actual amount of space that the dog barf, chute and recovery harness takes up relative to the pressure created by the ejection charge is almost insignificant. The dog barf, chute and harness are mostly air when you get right down to it. The ejection charge has to increase the pressure of all that air to be able to apply pressure to the nose cone. If you ground test with no recovery gear in place, there will be almost no difference when recovery gear is used. The only thing that may have any significant effect is if the recovery gear works like a piston. Dog Barf is NOT capable of working like a piston, and neither is a folded chute. All dog barf can do is prevent burning particles from reaching what's on the other side of the dog barf. The Z.ZZ volume is so small you can pretty much ignore it.
    Handeman

    TRA #09903 L3 3/29/2015

    "If you don't use your head, you have to use your feet!" my Dad

    Tripoli Central Virginia #25 - BattlePark.org

  24. #24
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    this looks about right....

    David McCann
    Dave's Rockets | My Flights
    URRG |URRF 4| Level 2 | TRA# 14210

  25. #25
    Join Date
    31st January 2013
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    ^^^^^

    Bill

    I won't be wronged, I won't be insulted, and I won't be laid a hand on. I don't do these things to other people and I expect the same from them.
    John Wayne, The Shootist

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