How Much Dog Barf to Use and How to Measure It?

[brockrwood]

I recently flew my Custom Rocket Company “Sport” using dog barf (cellulose insulation) as the recovery wadding.

I did not know how much to use. I just kind of stuffed it in with my fingers until it “seemed right”. Launch was successful and the parachute was unscorched, so it looks like I guessed right.

Is there a rule of thumb about how much dog barf to use, how to pack it in, and how to measure it?

 

[tsmith1315]

I use an amount that would be about the size of a coupler, 2x diameter or so.

I bought my current bale in the prior millennium and hardly made a dent in it, so sometimes I use a whole bunch in an effort to see some progress.

 

[neil_w]

2x diameter is what I shoot for based on recommendations on this forum. I've had various recovery issues over the years but one problem I have *not* had is scorched chutes, at least when everything ejects properly. Try not to compress it when stuffing it in the tube.

The worst part of dog barf is getting it in the tube, especially for anything less than or equal to 1". But as wadding it works great.

 

[bjphoenix]

10 pound of dog for every inch or body tube diameter. When the dog barfs look at how much comes out and put in the same volume of the cellulose stuff.

I've used DB a little bit and not had good luck with it, I was using about one diameter and it would not eject. I don't have that problem with normal wadding.

 

[smstachwick]

Dog barf is extremely imprecise but also extremely forgiving. 2 balls about the diameter of the body tube, loosened up to original density and inserted, should be fine. A little extra to account for wind blowing it away during this step won’t hurt. You can even insert it through the rear if you put it in before the motor, which is helpful with cruddy tubes and uncooperative recovery systems.

Just be sure that that the dog barf doesn’t look likely to get stuck on anything (motor hooks, thrust rings, messily-installed tri-fold mounts like the ones I do) and don’t ram it in like you’re loading a cannon. The classic “blow on it really hard it from the rear like a blow dart gun and see if the nose can pop off” test is valid with this stuff too.

 

[brockrwood]

10 pound of dog for every inch or body tube diameter. When the dog barfs look at how much comes out and put in the same volume of the cellulose stuff.

Ha! Ha!

 

[bjphoenix]

Dog barf is extremely imprecise but also extremely forgiving. 2 balls about the diameter of the body tube, loosened up to original density and inserted, should be fine.

I think I erred by packing it in too tightly.

 

[atestani]

Here is a fun fact:
Loosely packed dog barf is about 1 gram/cu-in or 0.035 oz/cu-in.

Using this valuable information, you can determine that the dog barf in a 4" rocket with an amount 2x the diameter, weighs about 100 grams or 3.5 oz.

 

[goose_in_co]

About 2x the body tube diameter, loosely packed.
For extra protection I will wrap the parachute in 1 square of estes wadding.

Where did you launch from Brock?

 

[bjphoenix]

Using this valuable information, you can determine that the dog barf in a 4" rocket with an amount 2x the diameter, weighs about 100 grams or 3.5 oz.

That sounds like too much. I have a big bag of the stuff and I don't think it weighs anywhere close to 3.5 oz.

 

[cls]

10 pound of dog for every inch or body tube diameter. When the dog barfs look at how much comes out and put in the same volume of the cellulose stuff.

Oh gosh, I've been measuring wrong. I usually put 3 or 4 cats in the dryer, measure that instead.

 

[Pem Tech]

When using traditional units of measure like the pinch, smidgen, dash, dollop, splash, dump, butt, puncheon, tun, hogshead, tierce rundlet, kilderkin etc...
I use great handfuls of barf to a depth of twice the tube diameter. Not sure what that volume would be in cats...

 

[atestani]

That sounds like too much. I have a big bag of the stuff and I don't think it weighs anywhere close to 3.5 oz.

I checked everything again and it is correct. I also measured my 2 gallon plastic bag full of it and it weighs about 28oz.

 

[gldknght]

Oh gosh, I've been measuring wrong. I usually put 3 or 4 cats in the dryer, measure that instead.

Do you measure the cats before, or after, the drying process? I'm betting the cats, after drying, take up *significantly* more volume!

 

[bjphoenix]

I checked everything again and it is correct. I also measured my 2 gallon plastic bag full of it and it weighs about 28oz.

I found my 1 gallon bag and weighed it. My bag is 4" thick and weighs 10 oz. Before I weighed it I thought it would be at least enough for 2 flights of a 4" diameter rocket so that aligns pretty well with the numbers in post #8.

 

[Back_at_it]

I stopped using it for anything but mid and high power but when I did use it, I would put enough in so that it was about and inch thick inside the tube for everything up to BT80.

 

[Ronz Rocketz]

I've had mostly problems with dogbarf. Usually the Kevlar shock cord snaps. Happened several times until I stopped using dogbarf in LPR. With MPR 3in or more, I add about 2in and then some Walmart party streamer on top. Blows out the laundry without cutting the cord.