How far up to put a baffle?

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solid_fuel

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I am planning to install a baffle in my build for the Red Nova. I will need to cut the body tube and use the baffle as a coupler. Is there any guideline as to where I should plan to have the baffle? I'm thinking as far forward as possible and still have room for recovery.
 
I am planning to install a baffle in my build for the Red Nova. I will need to cut the body tube and use the baffle as a coupler. Is there any guideline as to where I should plan to have the baffle? I'm thinking as far forward as possible and still have room for recovery.
Thats how I like my baffles and chute shelfs, far enough up and still have a little extra room once the laundry is loaded.
 
it will depend on the size of the body tube and the size of the chute, for most tubes under 3" dia. (and chutes under 30") about 8" from the forward end of the airframe will leave enough space for chute and shock cord.
Rex
 
I like to integrate kevlar or similar shock cord leader into the baffle and install down near the engine tube - giving plenty of room for the recovery bits.
For a 2 tube design I always use it as the coupler - so half way down.
 
+1 on as far forward as possible while still leaving some room for recovery gear and a little extra space. Too far back and it might change the CG point, affecting the stability of the rocket.
 
Any Rocket that I am looking to add a baffle to I get into Open Rocket and throw a coupler with 3 bulkheads in it in to see the impact of placement on overall stability :)
 
+1 on as far forward as possible while still leaving some room for recovery gear and a little extra space. Too far back and it might change the CG point, affecting the stability of the rocket.

Putting the baffle anywhere other than at the current CG will affect the CG. This is usually my primary consideration - not withstanding leaving room for the chute. Further forward isn’t necessarily best if it means you’re over stable with smaller motors. If the baffle is of “negligible” weight - then CG considerations aren’t as big a deal. Open Rocket is your friend here.




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I put my baffles in my box of spare parts, so they can never stick in a body tube...
 
Hey solid,
Here's a link to the Apogee Peak of Flight newsletter. One of the FAQs is exactly your question. Author is Tim Van Milligan. He has a degree in Aeronautical Engineering and worked for 3 years as an Estes designer:

https://www.apogeerockets.com/education/downloads/Newsletter369.pdf

Quote"...for stability reasons, it should be placed as far forward as possible" Unquote.

I rest my case.
 
Hey solid,
Here's a link to the Apogee Peak of Flight newsletter. One of the FAQs is exactly your question. Author is Tim Van Milligan. He has a degree in Aeronautical Engineering and worked for 3 years as an Estes designer:

https://www.apogeerockets.com/education/downloads/Newsletter369.pdf

Quote"...for stability reasons, it should be placed as far forward as possible" Unquote.

I rest my case.

Thanks. That quote is basically the last line of my OP
 
I do love the 'ol forum. You always get all the answers and sometimes two or more agree.

FWIW my feelings on baffles align with cbraricks. While I appreciate the utility I wouldn't go so far as to perform surgery to add one to a kit. My answer to the op's question would be at some point at the forward end of the airframe to act as a 'chute shelf leaving enough room for the recovery bits.

[edit] The entire article that kurinin linked to in post #15 is a good read. Tim also uses words like "should" and "idealy" and phrases like "But on the flip side...", "we have a trade-off situation here...", " In this situation...", and "But sometimes...". Oh, and this sentence, "The location of the baffle is fairly optional in your rocket." This suggests to me that there is some leeway in baffle positioning in a given design.
 
The baffle system doesn’t weigh all that much. And putting one drastically behind the CG seems relatively difficult. My plan is to put it somewhat near the mid line of the body probably moving the CG minimally toward the front. Compared to the weight of the motor and all the junk in the trunk the under an ounce or so of weight added by the baffle will not affect much at all.
 
I’m not sure what this means? I want it to stick in the body tube. That’s why I am going to glue it in.

He is saying he doesn't use them. I am not a fan of baffles either. I have only used two that I can recall and one of them blew out. The other is still in a rocket, but I put it a little too far forward and the laundry is a tight fit.
 
In scratch builds, I usually follow qquake's lead and put half moon baffles in the end of an extended motor tube.
I an working on one right now that it will probably become a tube coupling. I'll add a bulk head in the payload tube to minimize the volume to be pressurized.
 
Hey solid,
Here's something worth considering. Instead of permanently gluing the baffle in, I use snap swivels and Kevlar to make it portable from rocket to rocket. That way I only have to have one baffle for each tube size, rather than each rocket. I started attaching a snap swivel to each end of my Kevlar and elastic shock cord, instead of tying the ends together, so I could easily swap out nomex blankets. Cheapskate that I am, decided that it would be a good way to swap out baffles as well. These would more appropriately be called baffle/pistons. Beauty of it is, the baffle works whether it is fully ejected or not, unlike a piston ejection system, due to the bypass holes. All you have to do is add a length of Kevlar to each side of the baffle, with a snap swivel attached.
Concerns: The interior of the tube must be clear of obstructions, like glue boogers. Soot residue needs to be periodically cleaned off. And I still use a little wadding, especially for plastic and mylar recovery devices. If your baffle wears out or needs repair, it is easily accessible, unlike a permanent baffle.

baffles1.jpgbaffles2.jpg

Has anybody else done this, or am I the only cheapskate around here?
 
I love baffles in larger rockets--about BT-60 and up. I do a variation of the old design (one side with central holes, the other with perimeter holes). I like to install the baffle far enough forward to keep the parachute's weight near the nose, for stability. Once installed, I can insert the parachute, shock cord and nosecone, with an added 1-2 inches to spare. With a baffle, I generally go with the traditional Estes paper shock cord mount. Maybe it's me, but they don't fail me. Now, I throw out the shock cord and use one that is 3-5X the kit length, and I often use a heavier elastic than the provided one. Hard to beat a baffle on the field: fold chute and re-insert to fly again.
 
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