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.

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...

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

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

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.

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

Edward

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.

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

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.

I have used both pistons and baffles in low-mid power rockets. Baffles are a partial solution, but do what they are intended to do- trap hot particles and cool the gases. I still use kevlar blanket or wadding with a baffle, but I see much less scorching and need less cleaning with a baffle.

I have a Swift upscale where the ejection charge is 1" from the chute, but I have a skinny baffle in between with copper mesh inside. With only minimal wadding (there isn't room for a nomex blanket) the chute is OK. Copper or brass mesh is essential for cooling the gasses. Don't use steel wool as it will catch fire.

I find the sinuous baffles less effective and am afraid they would blow apart with too strong of an ejection charge.

I've used mesh filled baffles up to 2.5" airframes, but think I would steer away from a baffle on larger diameters as the volume of air moving through is higher and the pressure lower with larger airframes.

Pistons are a more elegant solution, but I've been nervous about using them in paper tubes commonly found in low and mid power. I haven't had any of my two piston rockets get a stuck piston, but I can easily see it happening. As others have posted, they would seem to be more reliable with smooth sided tubes.

What I like most about baffles is that they can be easily integrated into a coupler used with a mid-ejection design (to prevent zippering). Here is an example:
http://www.vatsaas.org/rtv/construction/antizip/anti-zipper.aspx

Don't use steel wool as it will catch fire.

Steel wool, with the proper oxidizer, can be used as a fuel in amateur rocketry—not to be confused with what we do. Good thing you pointed this out, Chad. You probably saved someone some grief.

Thanks for all the replies. New rocket is almost done. Very happy with build so far, still needs color. Excited to see new design this weekend.

3,2,1, Launch!!!!!!!!!!!!!!!!

David