John and Chuck's Excellent EX Adventure
We had super weather on Sunday at METRA field in Middletown NY, clear=20 skies and little to no wind. I can not say enough about how great the=20 METRA field is to fly on. Go tofor info. =
I have been a member OF METRA since 2002. The field is a sod farm with a =
mowed golf course variety of perfect grass. The field is huge and is the =
biggest I have flown on east of the Mississippi and right next to it is=20 a second huge field. So you really have to work hard to lose your=20 rockets. They have a great launch system with wireless remote sector=20 boxes to main launch box at the LCO and a great PA system. So the pads=20 can be set up at different distances depending on the motor power level. =
They also have available a huge trailer based launcher (UniStrut rail=20 button system) for the real big ones with (L +) motors, that they set up =
at the away cell.
This Sunday was really a fun day for me. For those that don=92t know me=20 from the =93old days=94 of HPR or the ASTRE section in the early 90's. I = am=20 a bit of a High Power Freak, but I love all kinds of rockets from 1/8 A=20 up. I have been even known to fly a NAR contest model once in while.=20 Anyway I have wanted for some time now to expand my HPR horizons by=20 getting in EX (Experimental) motor making. I dabbled a little in some=20 small single use EX motors G and H size earlier. But finally had a=20 chance to take a formal EX course given by Jeff Taylor of Loki Research=20 (a high power certified motor manufacturer) last week. This is a great=20 course with a lot of practical hands on techniques making composite=20 motors safely. In this class each of us made enough propellant for 2 -=2038mm small J Motors reloads (approx 750 NS per load a J300~). The class=20 includes one of Loki's 38mm reloadable casings (real nice blue anodized=20 hardware with graphite nozzle, snap ring design) and Professor Terry=20 McCreary=92s book on composite motor making. If any of you ever get the=20 itch to learn how make your own composite motors, I can highly recommend Jeff Taylor's class. But you must first have your level 2 certification and be a Tripoli member to take the course and fly them=20 since the NAR does not currently allow or do EX.
So on Sunday, Chuck, my old rocket buddy and I drove down to the METRA Indy format launch. I first flew my LOC Graduator on a G motor. It =
was a ok flight, arched over a bit on takeoff but not much of walk to=20 get it back. While I was waiting for Jeff Taylor to show up at the=20 launch we witnessed a flyer=92s Honest John rocket doing his Level 3 cert= =20 flight from the away cell. I don't remember the name of flyer, but he=20 did a great job on the rocket's construction and a very nice paint job=20 and fine scale detailing. The flight went perfectly and I assume he got=20 his level 3 certification. I had left my newly cast propellant tube=20 with Jeff to cure from previous weekend after his course. Jeff showed up =
around 11:00 and I got to work cutting my propellant in its casting tube =
into bates grains slugs and then borrowed Jeff's handy custom machined=20 hand tool to core out (drill) each grain. This motor is a 6 slug Bates=20 grain design. I then prepped my old trusty AAA Mag. Penn. Crude 4 inch=20 rocket for the flight. This is one of my favorite old rockets that I=20 have flown a ton of times with up to a full J motor in it. I assembled=20 the motor first and then prepped my electronics bay which contains a=20 Adept ALT 2-50K 2 event altimeter. EX motors must be flown with=20 electronic recovery deployment. Delay trains can be used for tracking=20 smoke but are not allowed for ejection charges according to Tripoli's EX =
rules. This motor has a plugged forward closure but does have a cavity=20 for a smoke grain if you want one. My altimeter bay is setup for two=20 stage deployment, drogue at apogee and main parachute at 800 feet. Good=20 thing because I knew from the computer flight simulation that I could=20 expect over 3500 feet with this motor if it worked as designed. That=20 could be a long walk if you put the main chute out at apogee. This=20 flight was also to be a test of using nylon shear pins for holding the=20 nose cone instead of friction fitting. I used two 2-56 nylon screws for=20 this test with a 2 gram charge of 4 F black powder to make sure of a=20 good shear of the pins. I threaded both the body tube and the nose cone=20 shoulder with a tap for these screws. I did this so there would less=20 chance of binding when the main deployment charge was fired by the=20 altimeter.
Well to make a already long story a little longer ;). I got the rocket=20 all prepped after having my next to my car neighbor flyer asking me a=20 lot of questions about making electronics bays. Prepping electronics=20 based dual deploy rockets always takes me some time and I tend to be=20 very careful when prepping them since you have a lot to loose if they=20 don=92t work correctly. If you have folks asking question it even takes=20 longer but I like to share ideas so it was ok since I knew this would be =
my only other flight of the day. I had lots of time to prep and explain=20 what I was doing and why to my fellow flyer. Chuck and I then walked to=20 RSO table after getting my flight card filled out and had a safety check =
performed and were told to find a free pad. So I went about getting my=20 rocket set up on a nice sturdy pad. Then I fretted on getting it nice=20 and straight up. "Hey Chuck how does this look?" After several little=20 adjustments it was time to arm the altimeter and hook up the launch=20 leads. We returned to flight line with the other flyers. It had of=20 course started to get a little windy after being so perfectly calm in=20 morning. I asked the LCO if we could launch first off the rack since the =
altimeter was on and we again had a calm period with little to no winds. =
But of course they instead wanted to first fly a Estes Fatboy drag race. =
Well no problem I tried to stay calm and watched as just one rocket of=20 two Fatboys took off. The LCO had his 8~ year old daughter? reading the =
flight cards, very cute but the time it took was a great way to raise my =
blood pressure and heart rate as I waited to fly my first big EX motor.=20 Well after the drag race they went directly to my rocket and with a nice =
count down, 3, 2, 1, nothing, no smoke, no joy. I was about to say to=20 myself =93Oh ^^$@@@#=94 when it was realized they were trying to launch a= =20 rocket on pad 3 which was empty but still seemed have continuity, but my =
rocket was on pad 4. So after a "short" reread of the flight card, did I =
say my blood pressure and heart rate were up. Oh yeah right 3, 2, 1,=20 smoke and then the motor came to a instant on. My rocket left the pad in =
hurry with a slightly yellow flame, nice clean burn, no pop's or chuffs. =
So far so good, long coast to apogee at this point I lost sight of it in =
the sun, but trusty eagle eye Chuck hadn=92t and he watched it coast to=20 apogee. I then heard the pop of my first event charge as the altimeter=20 did its thing. Chuck do you see it ? Yup the drogue is out. It was=20 coming down nicely with the rocket horizontal as you want nice and=20 draggy. I always use a long tubular nylon recovery harness so two=20 sections don=92t bump on the way down. Ok now after several people around= =20 me try to point where it is in sky I finally see it again, hmm time to=20 get my eyes checked. Ok it is coming down nicely, and it's at around=201000 feet or so and then I see and hear second charge go off and the=20 main chute deploys perfectly =94Yea !=94 I shout. I guess the shear pins =
worked!! Gee you think after a lot of successful dual deploy flights the =
thrill would be lessened but not for me. Its feels as rewarding as the=20 first time I flew with electronics. So my rocket drifts a little the=20 wind is back up some, but its no big deal this a huge field and we see=20 it land on a nice green patch of mowed lawn. Well this field is one big=20 patch of green mowed lawn!!, so duh. We wait for rest of rack to fly and =
Chuck and I take a nice leisurely victory walk out to get my rocket. I=20 find it in perfect shape on the lawn beeping out its altitude. For folks =
that never flown electronics this is the final nice bonus you get after=20 a successful altimeter flight, your altitude being beeped out to you over and over again. We approach the rocket and listen. Darn why do they always make them beep out so fast, was that 8 beeps or 7 Chuck? we=20 listen again. Well after a few attempts we both agree 3834 feet, alright =
not bad at all. I return with my rocket a very happy camper and of=20 course the first thing you get when you return is other flyers asking=20 how high did it go and you can tell them. That is a good way to end a=20 great flight!!
Oh if you haven=92t already stopped reading and gone to sleep or the=20 beeping from your PC woke you up because your head was on the keyboard,=20 I am sorry for going on so long with this story. I later checked out the =
shear pins and found they sheared perfectly even with a paper body tube. =
I had reinforced the holes for the screws with thin cyano acrylic glue=20 and the screw heads were still in the body tube and threads were sheared =
right at the shoulder of nose cone as if you used a nice sharp knife to=20 cut them. I am going to start using nylon shear pins for all my bigger=20 rockets after doing a few more test flights. It seems as Martha Stewart=20 would say "It=92s a good thing=94!! Yea right, now I am quoting Martha.=20 Maybe making EX motors does have serious side effects. Hey Jeff, what=20 did you say that propellant was out gassing? ;)
Cheers John ..