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Three inch CTI M2245 minimum diameter build
#31
Pitter, I checked out the Joe Woodworker plans before hand, but decided to go the quick and dirty route.  The press is definitely a better set up, I'm not arguing that.  I've got probably 100 hours on my pump so I've already got my money's worth... The harbor freight pumps are pretty in expensive.  I should buy a spare in case mine dies in the middle of a bagging session. Now I've probably jinxed it.

For motor retention, the forward airframe slides over the 3 centering rings, and short piece of coupler all of which get epoxied in the forward airframe and fit as shown below.  Add a couple of large fender washers on top the centering rings and tighten the nut down.  Put some loctite thread locker on the eyebolt so it doesn't back out.  That's pretty much it.


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#32
I put a finishing coat of epoxy on the fins and let it cure in the open air like in the first pic below, but even after 3 days it remained slightly tacky.  Not sure what the problem is since the epoxy in the mixing cup was fully cured.  I've had this problem with trying to put on a skim coat before with Aeropoxy laminating resin and also with the Cotronics Durapot I'm using now.   Amine blush is the best explanation I've heard.  I tried to sand the epoxy down which didn't go so well, so I just stripped it off with acetone.

I then liberally coated the fins again with epoxy and put it in the vacuum bag and came away with much better results, (second picture).  Near perfect finish except for the peel ply texture which I will lightly sand.


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#33
Amine blush can be removed with just water. Happens to me with Aeropoxy all the time, even in hot weather.
Dan Patell
TRA 10904 L3
Patell Manufacturing Facebook Page
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#34
I guess it is not amine blush then. Not fully cured epoxy where I can put my finger print in it is what I had. It was gumming up the sandpaper. Had to make several rub downs with acetone to take off the uncured epoxy.
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#35
I got someone to cut the excess forward end off the boattail. I epoxied it to retaining ring using Cotronics and a fillet of JB Weld.  Then I did some final length adjustment on the aft end  myself.


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#36
Ejection charge test.  2.0 grams for apogee got full extension, but not too energetic.  Will probably go with 2.25 and 2.75 backup.


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#37
It flew ... and I got it back.

I'll post data when I get back.



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#38
Congrats, looks like the antenna got a little charged. Looking forward to the data.
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#39
Here's all the data I have from the flight (BRB GPS, Xbee w ublox GPS, an Altus Metrum Easy Mini, and a Perfect flight Stratologger).
BRB max altitude was 38,300 ft AGL, Easy mini was 36,900, and Stratologger was 36,500. This was an M altititude Tripoli record attempt, so I was 'only' about 7-8 kft short. Smile

For the Xbee - Ublox combo, I did not have time to configure the mode to high dynamics and left it in pedestrian, so it took about 20 seconds longer than the BRB (which also has a Ublox 7 chip) to regain GPS lock after Apogee.  I was a little surprised I was receiving telemetry at apogee with 250mW Xbees using only a long rubber duck antenna on the ground, and wire whip on the unit in the nose.


The BRB file took some editing because it was intermixed with my previous flight in the middle of this flight, and still shows the descent at the beginning followed by time on the ground and then the ascent.  Not sure what happened with that. I got tired of editing.  Usually on start up it just overwrites the previous data starting at the beginning of the file.


The Easy Mini does not have an accelerometer so accel. based data is questionable.  Max gees should have been about 35.  My simulations  showed a speed estimate at mach 2.8 to 2.9 depending on weight I entered, so mach 3.3 may be high.  I meant to set the main parachute to deploy at 3000 ft, but had a mental lapse and forgot the easy mini is in meters, so the main came out at 3000 meters ~ 10,000 ft.



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.txt   BRB edit 75mm-mindia-M2245-8-1-15.txt (Size: 179.84 KB / Downloads: 3)
.txt   Ublox GPS telemetry file.txt (Size: 35.69 KB / Downloads: 3)
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#40
Perfect Flite Stratologger




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.xlsx   PF strato m2245 flt 8-1-15copy.xlsx (Size: 366.76 KB / Downloads: 3)
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