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Discussion in 'Low Power Rocketry (LPR)' started by JumpJet, Jan 10, 2019.
Another great flight out of mine. Again on a D16-6
That’s an awesome shot! So far, other than my single nozzle blowout, I’m really liking QJets under heavier rockets.
I launched mine three times on Friday using C 6-3's for each flight and it flew fine. Today I flew it at the club launch on a Qjet C 12-4 and it went unstable, belly flopped and spit out the laundry. I'm not quite sure why it went unstable, although several others did the same thing on the same motor, and several did not. Odd.
Coming back to this thread only to report we had four of these models at the club launch today and put up a total of 11 flights on the four, nine of which were on Estes C6-3s. Eight of these 9 flights were by two youngsters (for at least one of whom this was his first rocket). All flights were either nearly straight or perfectly straight. No one had any issues getting motors seated and the fins on correctly. All 'chutes deployed as they should and no fins were broken.
The only mishap was when a Q-Jet C12-4's enthusiastic ejection charge blew the upper section of my model apart for the second time at the joint between the base of the LM shroud and the top of the third stage.
Image is a video frame grab of the third flight on both of the youth's S-Vs when they decided they wanted to have a Saturn-V drag race.
You should check all of them that went unstable for the deformation of the foreword tube/well/centering ring. Once deformed misalignment is likely on future flights.
Yesterday, July 20, 2019 was a grand day out (for W&G) here in Massachusetts! My big brother (he's a geezer compared to me ) flew an RTF Saturn V, literally taken out of the box at the launch! I think it flew VERY well on the C6-3. There was one attempt by a fellow club member on a C12 and it didn't fly so well... at least one other person used one and it flew better... I'm sensing some variability in the QJets which is making me a bit leery. FWIW, IMHO (how many acronyms can I use here...) I think the C6-3 gives a sufficient flight for my purposes when flying scale... after all with scale I don't think the point is to send it to the moon (pun intended although it's not a very good one). My preference is a nice straight flight and a nice gentle recovery...
I had heard of many issues with sluggish liftoff, if wind speed is low, then C6-3 not really a problem just that the thrust to weight ratio is a bit too low. I converted mine to 24mm and flew it with a C11-3, Flight was flawless except that those clear fin units are very flimsy and landing on hard dirt was detrimental to it's reuse, need to fix it. It landed a foot from soft grass...DOH! On the other hand, this model would be great for the gimbal system (https://bps.space/signal) With the new AeroTech G8 Motor!I had heard of many issues with sluggish liftoff, if wind speed is low, then C6-3 not really a problem just that the thrust to weight ratio is a bit low. I converted mine to 24mm and flew it with a C11-3, Flight was flawless except that those clear fin units are very flimsy and landing on hard dirt was detrimental to it's reuse, need to fix it. It landed a foot from soft grass...DOH! On the other hand, this model would be great for the gimbaled system (https://bps.space/signal) With the new AeroTech G8 Motor!
BUT! I stuck the landing! The escape tower did not break. We did a 20 Rocket Saturn V Drag Race. I was amazed at how many recovery failures... Note the one on the left...
Estes has the fin unit available separately which could come in handy. I’ve been thinking that an Estes bp C11-3 would be the perfect motor for this rocket.
Saw some launches over the weekend. D16-4 seems like its the best option, the D10s generate a lot of heat and some people saw melting in the retainer area. C6 remains marginal but doable in low wind.
The motors to which you refer 18mm w/plastic cases instead of cardboard?
Yes, both plastic or resin or something. The D10 is Aerotech branded and is a full D, the D16 is QJet branded and is barely a D. The D10 has a much longer burn and can get very hot. Definitely risky to use it with any kind of plastic 18mm retainer.
Yep, then I have seen this be a problem before with plastics form Estes and yet another facet of the bad design. A typical cardboard motor tube design would have avoided this problem entirely.
I can confirm that the single-use Aerotech D10-5 gets too hot and can melt the motor mount. The threads on the mount got a bit deformed on mine. I think I can still get the retainer to screw on, but I won’t be trying that again. The flight was nice, but I would stick to QJets.
I really don't think Estes can be held accountable if somebody acquires a pretty obscure, powerful, core burning motor and it gets too hot for a RTF model.
Yes, it’s definitely Estes’s fault if you use a motor not recommended by the company and your rocket gets damaged.
Maybe, I and others fly AP motors in Estes rocket (some of them RTFs and ARTFs) all the time, but since they use a cardboard tube it is not a problem. Seems short sighted of Estes to presume flyers would NOT seek out and use more powerful motors in a rocket that is underpowered using the recommend motor.
Oh, come on, you didn't even know if the D10 casing was plastic or cardboard. These aren't something you're going to find on a store shelf. They're weird obscure little motors. They also cost twice what the QJets cost.
Sort of a catch 22 though in that the "recommended" motor according to Estes, based on Estes own documentation (see earlier in this thread), is not adequate, but an adequate motor melts the motor mount. Even use of the recommended C6-3 motor can deform the forward mount.
You've gone way past any kind of rationality on this subject.
No. The C6-3 is adequate, as has been demonstrated multiple times on FB posts and in this thread.
Not sure why you think not being on a "store shelf" makes them obscure. Motors like the AT D21 have been around for 30+ years. http://nar.org/SandT/pdf/Aerotech/D21.pdf
Then Estes need to "correct" their documentation. It has been demonstrated multiple time that it is not. Clearly you are ignoring those posts.
Sooooo, Grind out the forward plastic bulkhead and replace the whole motor mount assy with paper tube and centering rings... Or build the 24mm conversion... If you fly high power, surely you can figure out how to modify a plastic rocket...lol
You Betcha. I have the failure very well documented. Estes was kind enough to send a replacement so my plan is to produce a video illustrating how to avoid the motor insertion problem and mitigate the underpower issue (when using a C6-3) by using a longer rod. I'll probably use RockSim to demonstrate the benefit of using a longer rod. The video will include how to perform a 24mm conversion so you can use any motor that can lift it. I would have already done it but I'm in the middle of designing my L3 cert rocket. While it would have been nice to have something for the 20th of July, keep in mind we are only in the middle of the Apollo program's 50th anniversary ending in 2022. Besides Estes must have 1000s of these sitting on shelves. We saw several dozen just at the US Space and Rocket Center last week. The few we looked at had their original sealing tape cut so I'm guessing the supplemental instruction had been added to the kit just like the 2nd one we received from Estes.
We flew our 1/200 Saturn V on a Q-Jet D16-4 the afternoon of July 16.
I woke up on the 16th and decided that I would launch one of our Saturn Vs in a neighbor's field, but then I discovered an email from a local club, ROAR, saying that they were having a special Apollo 50th Anniversary launch that afternoon. So, we joined them.
Only a few people showed up, but it was a fun afternoon. The plastic Saturn V flew great on the D16 and was recovered without damage.
Since your post follows mine, I’m not sure if you are referring to me or not. But I definitely don’t hold Estes responsible for what happened to my rocket when I used a D10 in it. We agree it’s not their fault I used a different motor than what they recommend. In fact, I’m pretty sure when I said I was going to use a D10 a month or two ago, someone warned me it could get hot enough to melt the plastic. But I already bought the motors and wanted to try them. Sure enough, too hot. Oh, wells.
Another reason not to use the D10 is that it goes really high! I was flying at an HPR event with tons of recovery area, so there was no problem getting the rocket back. But on a smaller field, the altitude might have been a problem.
A rocketry friend of mine has used a D16, and that seemed like a good motor for this rocket. I’m just not a big fan of the “dirty” black smoke.
Sorry, should have put a quote in there since it was two up. I was replying to "Yep, then I have seen this be a problem before with plastics form Estes and yet another facet of the bad design. A typical cardboard motor tube design would have avoided this problem entirely."
I don't find anything in the NAR Model Rocket Safety Code referring to 'thrust-to-weight' ratios.
It it common sense... Several Estes rockets are too heavy for the recommended motors...I crashed my Ascender with the recommended motors. F15-0 to E16-8 It barely got into the air and staged horizontally...AND they did not even honor their warranty...
I flew my Estes 1/200th Saturn V (with a modified 24mm mount) with a C11-3 Flight was perfect.
Also from the Tripoli guides:
Safe launch practices:
G. Weight Limits
1. The maximum lift-off weight of a rocket shall not exceed one-third (1/3) of the average thrust on the motor(s) intended to be ignited at launch.
Go here for full documents... http://www.tripoli.org/SafetyCode
I have a complete 24mm 3D printable conversion kit...Uses a BT-50 for the motor tube to eliminate the melting issue. PM me if you want info.
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