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Show Me Your Baffles

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Gus

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I've read lots of posts about different types of baffles for low and medium power rockets, but I haven't had much experience in building them.

I'm interested in seeing a good comprehensive thread on which types work best, which type to use where, durability of different types, cleanability, relative ease of construction, etc.

So let's go, all you baffle-maniacs!

SHOW ME YOUR BAFFLES.

And a word or two on the relative pros and cons of your design would be helpful too.

Thanks,

Gus
 

prowlerguy

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The only baffle I have built thus far was one on my otherwise stock Fat Boy. I used 1/8 balsa to fashion two half circles, used cardstock to create a coupler-type assembly around 1.25" long, and attached the baffles offset on each end. I used Elmers glue for construction, and I attached my Kevlar leader to the bottom baffle half.

Why did I choose this design? Because I am cheap! I had scrap balsa big enough for half discs, but not large enough for the full circles needed for the offset vent hole type.

How has it worked? I have only flown twice, but both times I used just one sheet of Estes TP, and there was not so much as a dark spot on chute or shock cord. I'll take a picture tonight and post it.
 

rbeckey

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I have built a couple different kinds of baffles, and they have all worked well. The easiest one so far is to split a coupler into four parts, and get three basswood or lite ply bulkheads. Cut 1/3 off one side of each bulkhead and cement a coupler section into place in the BT using thinned wood glue, epoxy or polyurethane. (Don't want the glue grabbing while sliding the parts down the tube.) Alternate sections of coupler and bulkheads, placing the cut sections of the bulkheads on opposing sides. Try to keep the bulkheads about 1/2 to 3/4 inches apart. Leave 6-8 inches of BT open for recovery and NC shoulder at the top of the baffle assembly. I have used this on rockets as small as BT 55.
Remeber that you need 6-8 inches ON TOP of the baffle, which may be a couple of inches long.
 

Micromeister

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Ok gus:
I'll show you guys one NOT TO BE built. I got this "design" from a North Coast Rocketry catalog which instructed the construction of this BT-55 or BT-60 baffle using Aluminum Screen wire discs stacked inside a standard stuffer tube coupler..
It does work very well in protecting the chute but clogs up in a very few flights with NO good method of cleaning. I went a step further in using Stainless steel screen fabric which didn't help me when trying to drill it out after casuing a couple crashes of my 3X Orbital Transport. I've seen plans for this type Baffle in other forums. Please do not use this type in models where the baffle is beyond the reach of a standard length drill bit or poke out rod, they fill with clay and ash very quickly.

I really like the 4 half disc coated ply baffles built into a BT-55 to BT-80 couplers. Have had much better results and multi flight with them. I have a sketch of one at home somewhere, I'll have to do a computer drawing at some point. It is very simple for smaller models I use 3/32" ply half discs. with an extra 1/8" x 1/8" piece epoxy applied forward particle stop lip on each. Epoxy attached to the inside of a standard 1-1/2" coulping alternating half actually more like 5/8 discs, 1/2" apart inside the coupling and to the aft and forward ends. They are simple and quick to make and EASY to shake out the junk after each flight. Use all 1/8" ply on the larger models. The smallest one of these types I've actually built is for BT-50 but I can see it might be possible for even smaller couplings.
I seem to remember someone on this forum even had a pattens page for a very similar design. but that's been a good while ago.
 

LarryH

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Remember also that baffles arent the only way to protect your chute, PML uses a piston system, and while I havent seen it personally I can speculate on what it would probably look like, the piston would be comprised of a BT section that is just big enough in diameter to fit over your stuffer tube(or possibly inside of the stuffer tube, to leave room for the MMTs centering rings?), the piston would be plugged at the forward end, and has a centering ring that fits into your main BT at the forward end of the piston. About 1" from the forward end of the stuffer tube would be vented to release the excess gas when the piston is at the end of it's travel, there would also be vents along the OD of the pistons centering ring to give the gas some place to escape, there would probably be a narrow plywood ring glued into the end of the MBT to act on the pistons centering ring in order to limit the pistons travel and prevent it from ejecting with the chute. Again this is all purely speculation as I have never personally seen PMLs piston system, but I dont really see any reasons as to why it couldn't work, anyone care to enlighten me on how PMLs piston system actually does work?
 

cls

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on many of their rockets (all?) Aerotech puts a wire mesh baffle at the end of the MMT. take a look at the Initiator plans to see how that is built. seems to work OK, no soot on the parachute after quite a few flights.

also take a look at Bob Kaplow's system used in the Crayon rockets. just drill some vent holes in the top of the MMT, cap off the MMT with a bulkhead, and put some vent holes in the bulkhead. dead simple to build but seems to let some soot through. our crayon rocket is black and stinky on the inside after a dozen flights. I could try to clean it I guess!

http://www.nira.chicago.il.us/LeadingEdge/Skywriter-100.pdf


Some people like the PML system and have good results.

I don't have any direct experience with PML piston system but I don't want to try it for a couple reasons. first is the "thermal coefficient of expansion" of the poop pipe (Quantum Tube), versus that of the piston. seems like regardless of whether it is hot or mild or cold outside, the piston always fits just a little too tight... I worry if you take material off the piston to make it slip, then it will be too loose will get jammed diagonally in the airframe.

second, I don't like combining soot particles and moving parts, it's just a recipe for jamming. and I've seen PMLs jam a few times.


that said, I have reservations about the piston system in our Aerotech Sumo kit. On Sumos, I've seen a couple lawndarts and a couple tangles, and perhaps that many successful deployments.

we haven't built it yet, so still have a chance to change plans. anyone have comments on the Sumo's piston system?
 

Zippy

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I've used the PML piston several times now. It's just a short length of coupler with a bulkplate at the top end to wich a fat shock cord attaches from the motor end and a thinner cord from the piston to the NC or cargo section. The whole thing pops out of the rocket on ejection. It works well if fitted right. The tube has to be cleaned after flight though. Mostly I prefer to use Giant Leap's kevlar shock cord and chute pad on mid/high power rockets, less work and probably more reliable to.
 

Mike

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OK so is there a type of baffle that doesn't clog? If not is there a design that can be removed so it can cleaned or replaced?
 

Micromeister

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Mike:
The second part of my earlier post describes a 4 piece half disk/coupler baffle that works very well. actually the discs are 5/8 of the full disc but you see where were going:) After the flight you simply shake out any of the big chunks of trash that are stopped inside the layers by the disc forward 1/8" lip(s). Works very well which I had a drawing of the little bugger it's very simple really.
 

rbeckey

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In this thread I describe the build of a late lamented 4 inch Crayon that used a baffle system inside a BT 80 stuffer. The baffles were made of three pieces of 1/8 inch ply bulkhead. They were stacked and four holes were drilled through all three at once. They were seperated by coupler sections and the disks were rotated so that the holes did not align in the stack. If you go through the photos, you will see the bottom of the baffle. Worked fine with AT G64 and G80 motors.

http://www.rocketryforum.com/showthread.php?s=&threadid=2043&highlight=crayon
 

prowlerguy

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Here is the photo of my Fat Boy baffle. Simplicity and it works. Cheap, too.
 

rkt2k1

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I'm working on my first baffle as part of my Fat Boy mod project. I've incorporated ideas that I've learned here as well as other sites.

Here is a link to the thread:

http://www.rocketryforum.com/showthread.php?s=&threadid=6040

Pictures and Rocksim files are included in thread. I have corrected and posted an updated Rocksim file. The ejection charge needs to make two 90 degree turns before exiting baffle. Parachute is protected in nosecone sleeve. Let me know what you think.

Thanks,
 

Gus

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Thanks for all the input. I'm going to give it a try.
 
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