Dog Barf. ...How much?

[spence]

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?

 

[rharshberger]

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.

 

[Handeman]

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.

 

[rstaff3]

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.

 

[shreadvector]

https://home.earthlink.net/~mebowitz/Wadding_At_SCRA_Launches.pdf

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?

 

[billdz]

"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.

 

[shreadvector]

"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.

 

[tim cubbedge]

"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.

 

[Banzai88]

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.

 

[AlphaHybrids]

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

 

[shreadvector]

What about a Standard Poodle?

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

 

[rstaff3]

Poodles make poor wadding.

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

 

[shreadvector]

Even Leonard?

Poodles make poor wadding.

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

 

[Steve Shannon]

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

 

[Normzilla]

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

 

[Nantucketdink]

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.

 

[manixFan]

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

 

[shreadvector]

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.

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

 

[Bat-mite]

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 .... :wink:

 

[AlphaHybrids]

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

 

[Steve Shannon]

Somebody always has to go and ruin a perfectly good thread .... :wink:

Didn’t do a lot for the carpet either.


Steve Shannon

 

[Nantucketdink]

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.

 

[Handeman]

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.

 

[DavidMcCann]

this looks about right....

 

[Screaminhelo]

^^^^^:rofl::rofl::rofl::rofl::rofl:uke: