How to use dog barf?

[ihavemanyquestions]

Hi everyone!

I love the advice I've read on here, but I have a question about something I haven't seen directly addressed. How do use dog barf? My design that I like flying right now is a 4in non-minimum diameter rocket with motor deploy. In the past, I've just used the included ejection charge with DMS motors to open the chute up, but last time I had the charge melt right through the nylon shock cord. So, time for dog barf. My question is, do I just stuff some right on top of the motor? Maybe just through in a handful between the parachute and the top of the motor? Not quite sure how 'packed' it needs to be.

 

[teepot]

Depending on the size of the body tube I just throw a handful or two down the tube and then follow with some wading then the chute in a nomex blanket. I also use a shock cord protector.

 

[les]

For larger diameter bodies, like your 4" tube, you want to either use some Estes style wadding or a nomex blanket. The ejection charge will go through the barf.
I like to put a piece of wadding, barf, and then maybe another piece of wadding.

Try to have at least a body tube diameter of the barf (so for your 4" tube, have 4" of barf.

 

[ihavemanyquestions]

Thank you for the responses! In the past, I've wrapped the parachute in a nomex blanket, but the shock cord was largely unprotected. With the wrapping and dog barf, would the wadding be necessary?

 

[g.pitts]

Thank you for the responses! In the past, I've wrapped the parachute in a nomex blanket, but the shock cord was largely unprotected. With the wrapping and dog barf, would the wadding be necessary?

How about wrapping the portion of your shock cord with Nomex from the ejection charges up to your parachute's nomex wrap? This should provide the protection you are looking for. On my L1 and L2 flights I did this, and was surprised at how scorched the Nomex was as I was performing the post-flight recovery assessment.

 

[Nytrunner]

First off, you may have the greatest username on the forums.

I like to put a strip of ductape on the nylon shock cord for the first couple feet near the charge. It's cheap and easily replaceable. Any remaining shock cord I can generally loop and place in the nomex with the chute.

 

[ihavemanyquestions]

Thank you for the advice! Shock cord protection + dog barf hopefully means that I won't see a burnt shock cord ever again.

 

[DaHabes]

I find that on 3" plus birds I prefer a baffle if I have the airframe length. You anchor your recovery harness to the baffle assembly. No burnt chock cords, no shock cord protectors, no wadding, no nomex blankets. What you add in baffle weight you save on the other extraneous parts. The only downside is they can limit longer motors, but that is just a design parameter.