ejection baffles

[greywolves]

Hi everyone,

I have a question about ejection baffles. Do they all have some sort of wadding?

I see the baffle kits they sale, and like the idea of it, but none of them mention anything about a wadding. The reason i say this, my Initiator by Aerotech, has a baffled exhaust, but the kit had me install some sort of wound flat spiral wire.

I saw another that was closed “baffle system” on both ends, so more like a piston, cause it slides out of the body tube, pushing the shoot and lanyard out, while protecting chute. Due to its a nice fit. Wish i could recall what was called. Just curious about this also, likes or dislikes.

Whats your favorite protection system? wadding, baffle, piston, etc. are there others

Thanks

David 6

[Bruce R. Schaefer]

Kevlar pad. There are different kinds of baffles. Personally, I don’t use them unless it comes with a kit. Warren Musselman is a piston expert, as is John Wilke. You’ll see them both at the cleaning party this weekend. The purpose of a baffle is to “baffle” the hot ejection gases, so you don’t need wadding. I do have the Aerotech Arreaux that has the kind of baffle you mentioned, and three Centuri Semroc repo’s that just divert the gases. I built five old Semroc Centuri kits this summer and just have them for display. IF I ever were to fly them, I’d still use wadding under the parachute on those with baffles… only because I’m paranoid and really careful with any size rocket. Nope, I’m just paranoid.

[John A. WilkeParticipant]

I’m a piston guy – if the nosecone shakes off and doesn’t pull the chute out, the main charge just blows by the laundry and the next thing you hear is a loud THUDDDDDDDDD. With a piston, you are pretty much assured the laundry will come out.

Pistons don’t add a lot of weight, don’t take much room if you tuck the leash in under the plate… but they are best used with glass or carbon airframes, where they glide easily and aren’t subject to jamming due to a dinged airframe. As I almost always fly glass or carbon, they are a good fit for me. I’ve never had one jam, and there is essentially no way to burn a chute when you use one correctly…

[Warren B. MusselmanModerator]

I’ve had a piston jam twice. Once in a filthy quantum tube airframe and another time by greatly overpowering the ejection charge in an all-composite bird. (about x5 bigger than it needed to be.). Otherwise, I’m with John – I love pistons, but only use them on quantum tube or composite (fiberglass, carbon) airframes. Also, keep in mind you’ll need a smaller ejection charge with a piston.

Warren

[Jeffrey Joe HintonModerator]

I favor dog barf and then a kevlar pad wrapped around the chute like a tortilla holding burrito filling.

[AdrianParticipant]

I especially like pistons in low-power birds. They take a lot less room than the amount of dog barf you need for the same amount of chute protection.

[edwardModerator]

I’m pistons all the way. Never had one jam or fail. Just make sure you ground test!

Edward

[Ed Dawson]

I vote pistons (for rockets less than 5” dia.) for all the reasons said so far. Plus, they don’t get scorch marks or burn trough Nomex, Kevlar or the chute. I have had to retire Nomex blankets but never retired a piston. I’ve also made pistons for small 18 and 24mm birds. They take up less space and there always with the rocket. As said before – don’t use too much BP. The excess pressure expands the piston body tube against the rocket body tube which will bind or even break Quantum tube.

[Doug GerrardParticipant]

I vote pistons (for rockets less than 5” dia.)

Hi Ed, why only less than 5″ diameter? I’ve used them on 6″ rockets for years and even on Odyssey with a 7 1/2″ body tube there was a piston. I was just curious if there was something you knew about problems with larger rockets.

Doug

[Ed Dawson]

Doug,

I’m not aware of any problems on larger rockets, it’s just my personal preference. I suppose I should have been clearer on my post that it’s just opinion – not based on science or bad experience.

I just think that in the larger rockets you have plenty of room for a good burrito wrap and a chute that’s not tightly stuffed in an airframe. I also wonder about the large surface area needed when you have a large piston – and worry about the possibility of it binding – particularly if it is a softer sonotube airframe and piston.

[Author]

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