DD burning my chutes

I've noticed since I've started using dual deploy on my rockets I have more burn marks on my chutes. Actually I don't think I ever had a problem with motor ejection. I feel like I'm pretty good about wrapping the chute in the nomex burrito (12x12 for a 45" chute in a 3" rocket). And I feel like I'm using a reasonable amount of BP. Tests show good separation but nothing excessive.

Anything I'm missing? Do most of you use bags for your chutes with dual deploy?

Steveo said:

I've noticed since I've started using dual deploy on my rockets I have more burn marks on my chutes. Actually I don't think I ever had a problem with motor ejection. I feel like I'm pretty good about wrapping the chute in the nomex burrito (12x12 for a 45" chute in a 3" rocket). And I feel like I'm using a reasonable amount of BP. Tests show good separation but nothing excessive.

Anything I'm missing? Do most of you use bags for your chutes with dual deploy?

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2F, 3F or 4F BP, it makes a difference, and occasional burn holes happen. The larger 2 and 3F grains can burn through nomexs and chutes (large grain burns longer) 4F is whats in motor ejection charges.

Also if your using a set up that requires higher pressure to initiate deployment sometimes that can cause burns. I learned this the hard way. Now I keep burned chutes around for stand ins for deployment testing and good chutes in reserve for flights.

I am using 3F as I couldn’t find 4F anywhere. Hadn’t thought about grain size being a factor.

And I’m keeping the chutes for testing and play around with my setup.

Consider deployment bags too. They do a great job of helping get the laundry out predictably, and also protect the chutes.

Throw some dog barf in the payload as well. I know some people who don’t even use the nomex.

That is strange. I've never burnt a chute in dual-deployment, and I have never used a deployment bag either. The black powder grain sizes and burn rates could be the issue as mentioned by Rich above. I always use 4F black powder and fill the charge wells (above the black powder load) to the top edge of the well with dog barf (cellulose insulation) before taping with blue painter's tape. Does that help keep my nomex from being burned? Maybe, but I don't know as I'm not inside the rocket during the charges' ignition Like timbucktoo said, dog barf between the charges and your burrito wrap will work too.....

Here is a ground test showing the moment that the deployment charge fires. Big fireball in there.

Yet to burn a chute using nomex and dog barf....

+1 for dog barf. Wayne and I fly alot of DD and throw in alot of dog barf between the charges and the nomex. Rarely get a burn mark on the nomex much less the parachute.

shonc182 said:

Yet to burn a chute using nomex and dog barf....

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Same. Copious amounts of dog barf will set you free. 1 bale is a lifetime's supply for the whole rocket club. Use plenty. Use more. You'll have enough in 1 bale that if you leave it in your will for your kids, they'll be able to leave it to their kids in their will.

I was only using the dog barf to pack the top of my ejection charge and counting on nomex alone to protect chute. Time to stock up on dog barf.

Thanks for the tip.