Thank you -- looks like E20 or a pair of D20s will allow me to drop down to 2oz in nose.
X-15 (3D printed parts + BT-80 body tubes + plywood fins)
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Thank you -- looks like E20 or a pair of D20s will allow me to drop down to 2oz in nose.
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Looks really nice. I don't know if anyone has asked this before but how does the weight of the printed parts compare to the same being constructed out of paper / paper tubes?
If you go by OpenRocket material densities:
Cardboard is .68g/cm3
Paper is .82g/cm3
ABS 3D Print is 1.05g/cm3
PLA 3D Print is 1.24g/cm3
Usually I print ABS/PLA w/ 3 layers (1.2mm) thick or 2 layers (.8mm). Cardboard body tubes for Rockets are around .5mm thick. So weight ratios for surface area printed in various materials and in different thicknesses:
I printed the side pods in .8mm thick ABS so these are around 2.5x the weight of a comparable part made from .5mm cardboard. However, these ABS parts are not much more than a comparable injection molded nose cone.
Cardboard is .68g/cm3
Paper is .82g/cm3
ABS 3D Print is 1.05g/cm3
PLA 3D Print is 1.24g/cm3
Usually I print ABS/PLA w/ 3 layers (1.2mm) thick or 2 layers (.8mm). Cardboard body tubes for Rockets are around .5mm thick. So weight ratios for surface area printed in various materials and in different thicknesses:
I printed the side pods in .8mm thick ABS so these are around 2.5x the weight of a comparable part made from .5mm cardboard. However, these ABS parts are not much more than a comparable injection molded nose cone.
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Thanks for the info. I was wondering considering your weight concerns and whether or not for a build like this it wouldn't be better to go old school and construct using cardboard/paper (for those parts that you can) rather than plastic. Based upon those numbers for the same surface area of cardboard your pods added what - 40 or 50g of weight? Don't get me wrong - the 3D parts are cool and easier than a cardboard/paper build for sure. I'm not a Luddite.
Wherever I can build with a body tube I do but the side pods are not cylindrical so would be difficult to build with half a standard body tubes. You could make with a frame covered with posterboard but that would take much longer to build (and different skills than I have). You could also use a body tube + posterboard which might look ok but would be heavier than a standard body tube so some benefit would be lost.
The 3D printed side pods do weigh around 52g so not an insignificant amount of weight. Another issue with weight that I build with plywood instead of balsa but I really prefer the finish and strength of plywood.
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user 35280
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Could your X-15 be built with a modular motor can to allow the use of different motor configurations?
Ah, this was the other one of your creations that I most wanted to see kitted up! 
Yes, it actually is setup that way. However, the boat tail limits the options a little since it has a smaller aperture than the full BT-80 tube. When I finally get time to test launch this I will try with E12-4 and 2x D12-5 engines.
I did not make these but it looks like it would also fit 4x 18mm engines or 6x 13mm engines + 18mm center engine. Looks like 4x C5-3's would fly well but heavier than 2x D12's so would need more nose weight. The 6xA10 + 1xC5-3 is interesting -- 19.4m/s off the rod but only 25m in altitude (can call that one all bark and no bite).
Yes hoping to do that if it flies well!Ah, this was the other one of your creations that I most wanted to see kitted up!
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Very impressive creation and build. Will they be available for sale? Or the design?
Brad
Brad
I’d be up for a Coleopter kit at a reasonable price…
Launched my X-15 BT-80 rocket earlier today on a cluster of 2x D12 engines. Model flew great but see if you notice what went wrong...
Here is the result... I was just thinking earlier today that I have never had a rocket zipper. I guess there is always a first time. Zippered through upper tube (stopped at 3D printed coupler) and also cut one of the plywood rear fins right in half cleanly about 5mm away from 3D printed side pod.
So lets zoom out a bit to see what the problem might have been...
Here is the result... I was just thinking earlier today that I have never had a rocket zipper. I guess there is always a first time. Zippered through upper tube (stopped at 3D printed coupler) and also cut one of the plywood rear fins right in half cleanly about 5mm away from 3D printed side pod.
So lets zoom out a bit to see what the problem might have been...
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Do I get a cookie for saying there is absolutely zero reason that happened?
Haha...
Morale of the story is don't test fit random motors that are on hand and then forget and assume you have already loaded the correct motors for launching.
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That being said, sorry that happened. It always sucks to have to go back and fix things like that.....
Thanks, not too bad to fix -- the top section of tube was separate anyway so just need to cut zippered part off the coupler. The rear fin will be a bit more of a pain to cut out since it is glued to body tube as well as 3D printed pod. Still should be able to get it out with a little digging and easy enough to get it replaced once removed.
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The beginning of the flight looked great!
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Salvage operations mostly complete...
It is when we disassemble our rockets that we see how good our assembly techniques are...
It is when we disassemble our rockets that we see how good our assembly techniques are...
Thanks! Yes, definitely stable which was great to see... Just needed these to be D12-5 or D12-3 to see how high it would have flown...
Thanks -- I use BSI products quite a bit (need to use low odor CA glue to avoid irritating my sinuses).
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It took me a few episodes to finally figure out I have a severe allergy to CA. I never really used it much in builds anyway. I’m fine if I use the BSI Super-Gold.
user 35280
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D12-0 booster motors, I’m thinking you’re lucky it even ejected the nose cone, pressure was enough I guess. What size chute did it have, looks like it hit hard?
I guess that a pair of engines feeding into a BT-50 stuffer tube leads to good ejection results (also I confirmed that all the 3D printed parts are still in good shape after flight including the splitter / conjoiner that channels the two engines into one buffer).
It had a smooth landing actually. These 3D printed models with plywood fins are extremely durable (notwithstanding a zippering incident like I had here). It was a 30" Estes nylon chute.
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I printed a new nosecone for this model (got tired of seeing everything else in white ABS and the nosecone in gray). I also added some canopy and nosecone details while I was updating it.
Gonna get this one back in the rounds for testing. Pair of D12-3 engines, maybe an E12-4 or maybe some composites (pair of D22's or an E26 possibly).
Gonna get this one back in the rounds for testing. Pair of D12-3 engines, maybe an E12-4 or maybe some composites (pair of D22's or an E26 possibly).
Launched this guy today as well and had a great flight and recovery.
I got leery after a couple of zippering incidents but today everything went great on a cluster w/ 2x D12-3 engines. Original zippering was due to D12-0s being loaded but it also zippered on a pair of D12-5's (I guess long delay may have combined with windcocking due to windy day when I last launched).
Anyway, I guess D12-3 was just right.
Next goal is to redesign the motor mounts so that I can use a larger variety of motors.
I got leery after a couple of zippering incidents but today everything went great on a cluster w/ 2x D12-3 engines. Original zippering was due to D12-0s being loaded but it also zippered on a pair of D12-5's (I guess long delay may have combined with windcocking due to windy day when I last launched).
Anyway, I guess D12-3 was just right.
Next goal is to redesign the motor mounts so that I can use a larger variety of motors.
Almost done with final redesigns of this model -- smoothed out parts, added canopy details, modified engine mount to allow motor tube, etc...
Had a great flight today on a pair of D12-3 engines w/ 30" parachute recovery (I did not like the look with the longer tube so cut it down to be closer to scale -- and so had to test again).
Here is the flight:
Also my videographer posed with the rocket prior to the launch:
And my recovery specialist was joined by the videographer who did double duty today... Low winds made for easy recovery.
Had a great flight today on a pair of D12-3 engines w/ 30" parachute recovery (I did not like the look with the longer tube so cut it down to be closer to scale -- and so had to test again).
Here is the flight:
Also my videographer posed with the rocket prior to the launch:
And my recovery specialist was joined by the videographer who did double duty today... Low winds made for easy recovery.
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Looks great
Here’s a nifty antizipper trick
https://www.rocketryforum.com/threads/blaines-kevlar-anti-zipper-using-foam-ear-plug.154996/
Here’s a nifty antizipper trick
https://www.rocketryforum.com/threads/blaines-kevlar-anti-zipper-using-foam-ear-plug.154996/
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Since you video many of your rocket launches, one thing that may help you on mismatching motors is, prior to count down, name the rocket and the motors.
Had you said, “This is the X-15 on a cluster of two D12-0s, 3,2,…… wait a minute, that can’t be right”
There is probably a reason they do this at sanctioned NAR and I presume TRIPOLI launches, at least all the vids I have seen.
Also nice info for those who watch your videos.
