- This topic has 73 replies, 22 voices, and was last updated 17 years, 5 months ago by
edward.
edward.-
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Adrian
The F32 is a good motor. If I had to choose between it and the F10, I’d choose the f32 because the F10 needs gargantuan fins to be stable, and it’s really hard to make them perfectly straight and get the whole non-motor mass around the optimum 40 grams. The mass-optimized F32 and F10 designs both have about the same acceleration off the pad, so they should both be about the same for weathercocking susceptibility. When I make realistic designs in Rocksim customized for each motor, both top out around 8800 feet.
But if you think the F32 always has lower drag losses, it’s because you forgot that V squared is just as important as D squared. And more so, because Cd goes way up when the F32-based rocket is transsonic.
Go to Rocksim and plot your rocket’s drag force (not Cd). In my 8800-foot F32 design, the drag tops peaks 12 N. The drag force of my F10 rocket never gets above 8 N, though it stays high longer. (7 seconds above 4N vs. 2 seconds above 4 N for the F32). The total integrated drag loss for the F32 is lower, but the gravity losses are higher because it’s so much heavier at its optimal mass, and it takes longer to get to apogee. So all in all, it will be a fair and interesting competition, and may the best rocket win.
And I’ll just pretend I didn’t hear you threatening Hartsel after all the discussion about that on the other thread. 🙄
Warren B. Musselman
Don’t feel bad Adrian – Wilke not only threatened me with it, he went and did it for the current G world record. I still have 3 or 4 of those G55 motors, again a 24mm, and if TC actually gets their waiver expansion, I’ll start thinking about going after his G record later this year. The birds are already built and pretty much ready to fly except for the altimeter.
One would have to see the design and flight profile intended to comment about the likelihood of going transonic and that bird has never even been seen by my good friend John except in the E version. My E, F and G altitude birds do not break Mach – they come close, but don’t break it. I won’t tell you what they sim to until after they fly. There are a few tricks employed in the design that I doubt anyone but Wilke or perhaps Inman have thought of. By the way, they have very small fins.
Given that these motors are out of cert and my focus this year is on much, much larger birds – I’m in no rush to fly them. Good luck on your attempts – even more luck to you on finding them after the flight. With the weight optimization, I had to leave out the tracking transmitter on all but the G version and after losing 2 earlier builds of them a couple years ago, I got kind of gun-shy about flying them again and losing yet another altimeter.
W
Anonymous
Warren, two areas of comment. First of all, the Hartsel site does *not* offer a 20% advantage. I have flown my G and H record rockets on the same motors at both venues. My Hartsel “G” shot was 9% better vs. PNG – but it was flown under utterly ideal conditions at Hartsel and utterly wretched conditions at the north site. Those who saw my boost at the north site will also remember the c-slot motor eroded the nozzle, and the north site boost corkscrewed badly. Since I knew I was moving and the motor cert was expiring, I flew at the N site under pretty substantial winds.
I also flew the H rocket at both sites, and the difference was 4%. The Hartsel boost was so razor straight, I looked at Elvis and said “if that don’t get it (the TRA record) then I don’t have it in me”. Bottom line, empirical evidence would suggest that while Hartsel offers an advantage, it is not anywhere near 20%. I have tested it with very real-world boosts. The sims also are much, much, much closer than 20%.
The other area I wanted to comment on was G55s – they, like the F32s in your arsenal, have lost their certification. As such, you can’t use those for a G altitude attempt, either…
Warren B. Musselman
I know John – I know. Like I said, I dilly-dallied myself out of the running since there are no current motors with the capability to beat those records. However, the NCR altitude contest most definitely allows out-of-cert motors, even if NAR or TRA don’t. If I can’t take the world record, I can certainly take the club record. If I beat you, good luck to anyone else trying it. If I don’t beat you, you can rest assured that the record will retire with you.
I’m curious what Tom Rouse will say when Adrian applies for a record considering rumors about Tom DQ’ing flights on electronics he’s not personally familiar with. Wasn’t it you that told me about that picture perfect N1100 shot at BALLS that Tom just blew off right out of hand because he had no experience with the altimeter in question? There are other stories I’ve heard eluded to.
W
Anonymous
Jim Wilkerson had a MONSTER boost on an N1100? at BALLS a few years ago. I was there and saw it firsthand. Jim has the current M record, and he is a very talented flyer. I later inquired as to why the N record had not been recognized BY TRA and I was told it was DQ’d because the electronics were not suitable for that altitude. My memory is fuzzy here, but IIRC it was because he had used an altimeter that was certified to 45K and had gone to 46K (ish) MSL.
I also understand that the unit he was using had been tested and calibrated in an FAA approved chamber to that altitude in anticipation of the altitude he achieved.
All of this is second-hand — other than the boost, which I saw with my own eyes. For the record, I think his record is legit.
slipstick
I’d like to introduce Slipstick IV, a rather slim bird for its size, that will fly at MHM. Its a two stage rocket, based on two Performance Rocketry G3’s (ordered with custom modifications), using K700W’s for the boost and for the sustainer. I’m hoping to bust 15840 ft to put me in the 3-mile high club. ❗ Details on request.
Warren B. Musselman
Sweet looking project Mike. I look forward to seeing it fly.
Warren
slipstick
I just need to try and cut out some of the length where I can.
Adrian
Looks great, Mike. What’s your design for the staging?
slipstick
Looks great, Mike. What’s your design for the staging?
OK , since you asked, but keep in mind it changes every moment I work on it. Here’s the basic concept. Its designed so that the wiring to the igniter is attached externally to two screws on the airframe which are soldered to copper foil traces going up to the timer just above the motor. This way that is the last thing to attach (for safety) once the rocket is vertical.
You will notice from the real picture of the rocket, that I have rounded off the fins, which is to reduce the area of the fin in the airstream that causes twisting moments at the fin span. Its supposed to hit Mach 1.2 and reach 17,000 feet.
Where new joints were added, the couplers are inserted 1-1/2 diameters into the airframe. This is in the middle where there is the most stress. I was stuck using 1 diameter where I was using existing rocket parts from my L2 bird Slipstick II, which is on the top and bottom of what is now Slipstick IV.
The separation and deployment of the booster is handled by a timer in the booster avbay which becomes the nose cone of the booster. I’d rather put a real altimeter in the boost section, and test for apogee deployment, rather than using a timer as shown. Want to donate one, for a beta test?
For a larger PDF of the above image, Click here:http://telerover.com/rockets/MS/G3_mods_two-stage_Rev7.pdf
Adrian
Warren B. Musselman
Anonymous
slipstick
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