Roachwerks Nike Hercules and the Estes E12s

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After 2 flights the motor tubes were considerably burned through but I thought it was still flyable. It did have 1 stuck motor spacer that I had trouble digging out. I then saw that the tubes would accept the long E12 motor and the burned tubes shouldn’t be a problem with the longer motors. Should I risk a rather nice historic Sandman original or just retire it?🤔
 
I’d had success with E12-4s and thinking maybe the motor problems have more to do with how they’re stored I thought a flight with 4 long burn E12-6s could be awesome!😳
 
View attachment 650931View attachment 650932Upon inspection of the motors there was burn through with considerable motor tube damage…what’s up with that? Is that a characteristic of the E12s?
It may be the effect of all the motors being so close combined with them being recessed (?) and maybe Krushnic effect causing the flame to form a hot spot there; however, I don't have much cluster experience, but have heard of similar with recessed motor builds.
 
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Ken I hadn’t thought about the burns happening from the outside…I think you’re right! Too coincidental to all burn from the inside at the same place along the motor hooks. Definitely some force or action from outside the motor tubes! Thank you!
 
View attachment 650931View attachment 650932Upon inspection of the motors there was burn through with considerable motor tube damage…what’s up with that? Is that a characteristic of the E12s?
This is the same burn pattern I get on a 24mm 3 motor cluster. The inner portions of the motor tubes that face each other are burned off, with a burn pattern on the motor cases. Like KenECoyote suggested, some external effect causing hot gases/material to concentrate/swirl in the center.
 
I wonder if a drop in, removable module could be designed.
Very cool flight.
 
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This is the same burn pattern I get on a 24mm 3 motor cluster. The inner portions of the motor tubes that face each other are burned off, with a burn pattern on the motor cases. Like KenECoyote suggested, some external effect causing hot gases/material to concentrate/swirl in the center.

my rockets with three motor tubes glued together like an Enerjet 2250/2650 as part of the lower airframe I have not seen this, even using 27mm black powder F100s back in the old days. The tiny part in the center of the three tubes is "generally" sealed off to keep ejection charge pressure from leaking.

So lets say you put 3 BT20s in a BT60, but you also put them in the BT-60 flush instead of extending them down like in a 2250? Perhaps that is where the issues happens?

I am not sure because lots of Egg Lofters in the 70s and 80s used BT-60 around 3 BT-20s and never heard or seen this. I think it is because they are pushed forward into the surrounding type as Ken says about the "K" Effect.

I've only flown 2250 style 3 engine clusters however, and Titan 2 engine clusters.
Typical 2250 design in 18mm engines into BT-60 that does not have this issue:

1718570305634.png


LOC made many 24mm rockets like this that did not do that, or their 29mm , 54mm versions of it.

1718570652816.png
 
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Too bad, nice looking rocket. A way to avoid that is to seal up the rear end. Fill in all the gaps between the motor tubes and motor mounts, between the motor tubes and the airframe. It would add a bit of weight but better than what happened. Even a coat of epoxy (JB weld) with a brush around all the tubes should prevent what happened.
 
You know I believe it’s still flyable…the burned out inner sections might allow an aluminum strip added to each motor casing down the hook line to keep from burning through the motor casing of each motor!🙄
 
This is such a love of the hobby kit in that each one has individually turned transitions, nose cones, etc. out of balsa.! I can’t imagine the amount of work Sandman put into each kit! And he did several scale sizes too. I may just retire it as a tribute to his work! Thank you Steve for the attention at NARAM 63 on behalf of Sandman!
 
My guess would be that hot gasses are being pulled up between the mounts, combined with the close proximity of 4 motors. If it were mine, I'd try making a 1/8" plywood "plate" that fits into the end and fills the spaces around the motor tubes and between them and the side walls. You could also, or instead, fill the gaps with a bit of fire retardant expanding foam. (There is a version of "great stuff" out there that is retardant) But I've never done this, so take that advice with a grain of salt.

It's a nice looking rocket, and I'd be tempted to put it on a shelf too, but on the other hand, rockets are meant to fly! Maybe just take it out for special occasions.
 
Capt. Eric, I was thinking the same thing…a thin plywood plate square where motor tubes could poke thru would work. My Estes Pro Series Patriot has a metal end ring for the 4 cluster D12s!🤔
 
Thanks Nola...yeah that's the burn pattern alright! The motor tube vinyl stickers are the same from Stickershock. The markings at the fin level are copied from the RoachWerks model and are actually cut from vinyl Trimcote and a hole punch. Not really to scale but from 10' away I thought they'd give a semblance to the real markings?
 
Capt. Eric, I was thinking the same thing…a thin plywood plate square where motor tubes could poke thru would work. My Estes Pro Series Patriot has a metal end ring for the 4 cluster D12s!🤔
I'd use an aluminum plate... Anything wooden will also burn.​
 
I'd use an aluminum plate... Anything wooden will also burn.​
But it's much easier for me to cut the plywood. Can paint it with high heat paint, which might help keep it together. Doesn't have to withstand the heat for more than a couple of seconds.
 
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