Aerotech "Cooling Mesh" -Opinions ?

I picked up a couple of old Aerotech kits (Mirage and Astrobee D) a while back and just getting around to building them.

They use this "cooling" mesh concept. I have to say I'm a little mixed on it.

Anyone have experience with this ? Install it or junk pile ?

I used it on both my Cheetah & Tomahawk. Works fine. No need for dog barf or any chute protection. Just need to make sure the red cap from ejection charge is removed after each flight so it doesn't plug it up.

Junk pile. A far as I know they don't use it anymore and that should tell you something. It came with one of my kits and I didn't install it. Some people say it works OK, but you need to clean it after a few uses as it gets clogged up with soot and other ejection charge by products. With dog barf and Nomex sheets readily available I say why bother.

It works fine. It's basically a stainless steel chore boy scrubber. In addition to cooling the gas, it prevent burning powder particles from burning holes in your parachutes. An ejection baffle performs the same function.

Wadding, Nomex blankets and ironing board fabric physically keep the hot BP particles from impinging on your parachute and burning holes in it.

It doesn't matter which one you use, but you need to use something.

Another satisfied user with double digit flights of my Barracuda. Not junk, just different.

It always worked fine for me, but if you build your motor mount stock you will be limited in casing length.

Casing length was one consideration. Hadn't thought about the ejection charge plug -that could be an issue.....

Used it on one of my two Arreauxs but not the other, which was designed as DD. I used it on my Mustang may she rest in pieces, and my brother used it in his G-Force. It works as advertised but it will limit the motors you can use. In the Arreaux and Mustang this is not a limit, unless you want to push it, because the MMT is pretty long and if you like to recover your rockets and fly them again then you will likely stick to motors that fit. When I eventually build the Astrobee D I will likely forgo it as I would like to use some larger motors so I will probably just use dog barf.

Bottom line is it's a preference to use it and think about the flying you want to do when deciding, but it does work and works quite well...and yes Zeus-cat is correct you would be wise to tap out the crap as well as get some of the long flexible grabbers and you can pull out the mesh and clean it a lot easier.

I have one of these in my launch box, which I picked up from Home Depot for a lot less than this. https://www.amazon.com/dp/B01HR43GXY/?tag=skimlinks_replacement-20

I like stainless mesh and use it the baffles on my scratch builds. Only caveat is it can get plugged by motor ejection charge caps. Not an issue the way I build my baffles....

Can't see the BP residue plugging it up.

bobkrech said:

It works fine. It's basically a stainless steel chore boy scrubber. In addition to cooling the gas, it prevent burning powder particles from burning holes in your parachutes. An ejection baffle performs the same function.

Wadding, Nomex blankets and ironing board fabric physically keep the hot BP particles from impinging on your parachute and burning holes in it.

It doesn't matter which one you use, but you need to use something.

Click to expand...

Bob, I've been meaning to ask you a question on this topic. I've recently been using SS scrubbing pads on a few more of my rockets up to 3" min dia stuff. I find it easier and more compact then dog barf or nomex. Now the question: Does the SS cooling reduce the amount of gass produced? I ran some test using a single scrubbing pad placed over a 1 g BP charge. it did not melt rip stop laid directly over it, nor did it ignite a tissue layed over it.

You can get a 3 pac at the Dollar store and may need to be replaced after 10 (?) flights. I'm just tying them to my shock cords and placing the charges under them.

Tony

Junk it.

First of all, you can't fly it on a longer motor.
Second, over time it will get crudded up and make weaker and weaker ejections, until you don't get the chute out and, well, ungood things happen.

Tony - it does reduce gas volume because it reduces the temperatures of the ejection charge gasses. When myself and Mr Bobby Rosenfield were doing the development on the AT Sumo kit we discovered that the mesh reduced ejection charge force significantly. Always test to make sure it will pop, but of course you know that amigo.

tfish said:

Bob, I've been meaning to ask you a question on this topic. I've recently been using SS scrubbing pads on a few more of my rockets up to 3" min dia stuff. I find it easier and more compact then dog barf or nomex. Now the question: Does the SS cooling reduce the amount of gass produced? I ran some test using a single scrubbing pad placed over a 1 g BP charge. it did not melt rip stop laid directly over it, nor did it ignite a tissue layed over it.

You can get a 3 pac at the Dollar store and may need to be replaced after 10 (?) flights. I'm just tying them to my shock cords and placing the charges under them.

Tony

Click to expand...

I've used dollar store scrubbers in rockets where I use spacers in longer than necessary motor casings. Just shove the scrubber in the spacer and you have a build-in removable baffle. For example, a 54 mm 3G casing with a 1G or 2 G reload. It's really simple and it works well.

Since the gas is forced through the mesh, some heat is transferred to the mesh and the gas cools, so the volume is reduced, but I haven't noticed any significant difference provided you have enough powder to pressurize the volume. It's not that much different than dog barf. The gas is cooled passing thru the dog barf as well. Certainly if there is nay dog barf left after the flight , it will be quite warm when you take it out.

FWIW. YMMV

Just flew my Arreaux kit for the 50th-60th time at NARAM-58 and had no issues with the cooling mesh.
My Mustang, Initiator, Sumo and G-Force also flew and recovered without issue at NARAM.

I use a version of the AeroTech baffle system in other company's kits and some of my scratch-built models.
It works just fine for me.

I did not use it in my G-Force. At that time, the kit also came with a motor hook, and maybe a motor block too. I did not use any of it because I wanted to use longer motors. I used an Estes retainer for motor retention and a nomex blanket for chute protection. It has worked great.

So....it's clear the system works (I had no doubt in that) but may have some longer term implications. In the end, I can easily leave it out and dog barf is cheap so.....

Suborbital Maniac said:

So....it's clear the system works (I had no doubt in that) but may have some longer term implications. In the end, I can easily leave it out and dog barf is cheap so.....

Click to expand...

You can pull it out with a hook if you change your mind, although you'll still have the baffle to contend with.

If you don't use it, the full heat of ejection goes on the plastic shock cord mount, so if you remove the mesh, I would not use that plastic mount either.

I liked the idea, and added it to a large Estes kit, but there I built so that the mesh could be pulled out. That let me periodically shake the crud out of it.

Two words about converting this stuff to DD. "Plastic Fins". Consider glassing them if going to be pushing the impulse. I had a flutter issue crack a fin on the AT HV Arcas going from an H128 to a H165. I had a 29mm Aeropac retainer lying around so used that. Kurt

I am a bit concerned with the plastic fins. I don't plan on pushing the limits of these but a 'glass wrap would certainly be a good idea if I decide to push the envelope.

ksaves2 said:

Two words about converting this stuff to DD. "Plastic Fins". Consider glassing them if going to be pushing the impulse. I had a flutter issue crack a fin on the AT HV Arcas going from an H128 to a H165. I had a 29mm Aeropac retainer lying around so used that. Kurt

Click to expand...

Personally I would not recommend fin reinforcement for these rockets with DD, unless you are trying to push the velocity and this is not the right vehicle for that. When I converted one of my Arreaux to DD, velocity was not the point, launching it above 1,500AGL and being able to recover it in a reasonable area, or at all, was the motivation.

Then just when you figure you have it all figured out, here comes the Jolly Logic CR.

Use them where they belong, in the kitchen sink. I like the LOC style that uses wire mesh to make their baffle. I have personally seen two AT rockets catch fire. One was a smoldering fire that burned the mesh up as well as the plastic. The second started a large range fire..... A near-by farmer got on his Cat grader/maintainer (it was huge), dropped the rippers and drove around the front of the fire , ripping the ground putting the fire out. Good thing, we were so far out that it took the BLM 40 minutes to get to an already out fire.

Ummm... Did they used to use finer mesh? That thick SS stuff shouldn't burn any easier than most materials we use. Fine wire mesh burns well, but that's the crazy thin stuff.

This is how I solved the problem of the clogged cooling mesh. Note this really only works on 4" models.
https://www.rocketryforum.com/showt...ffle-for-the-MEGA-Red-Max&p=699119#post699119

Jim

I did a retrofit where I took an Estes kit with a payload and cut a few big holes in the payload bulkhead, put the parachute in what was the payload, setup to deploy out the nose, and put mesh where the parachute had been. Then instead of gluing the payload on and making the mesh permanent, I added tape around the coupler till it was too snug to inadvertantly separate there, but I can still pull it apart by hand to clean the mesh out.

If the scrubber caught fire, it was not a stainless steel Chore Boy type scrubber that AT uses. I'll speculate that someone substituted a plain steel wool pad which will burn up every time... They're sometimes used as an igniter in hybrids that supply O2 to assist the ignition.....

bobkrech said:

If the scrubber caught fire, it was not a stainless steel Chore Boy type scrubber that AT uses. I'll speculate that someone substituted a plain steel wool pad which will burn up every time... They're sometimes used as an igniter in hybrids that supply O2 to assist the ignition.....

Click to expand...

Sorry Bob, nope. Stock builds. One belonged to my brother Jerry and I know he did nothing different with the build than AT intended. Both rockets had a high number of flights and both were Mustang's.

Was it the scrubber, or something caught in the scrubber, like the paper disks off the top of AT single use motors?

Put yourself inside a AT rocket, right in front of the motor. The ejection charge starts to burn the BP, pushing un-burnt and partially burnt powder in front of the "blast wave". Hot gas BP hit the cold stainless steel and condenses. Not much but flight after flight it builds up. I believe it's the powder coating that starts the burn. My brother's rocket caught on fire, the second rocket never caught fire, it was like an ember burning with no flame, just destruction

I can't tell you what gauge the pad mesh pad was but I have seen that there are different sizes of the stainless. Some was a smaller size than others with a more robust thickness to the shaved metal.