Many of you will already know this stuff, but here is some of what you need to know for the neo's or newbies. This will pertain to low and mid-power rockets. High power will be something else. I had a rocket come apart as it was leaving the launch rod yesterday. It came apart at the coupler where it was to be a zipperless fin can. I think the coupler, which I made and was about 4" long was possibly too loose and so in the breeze or with the pop of the ignitor (It was suppose to fly with a CTI G54) the rocket came apart as it launched. So keep the couplers snug, not tight, but not loose. If you can hold the rocket by the nose cone and it all stays together, and yet if you can tap the fin can with a finger and the rocket comes apart at the coupling, I would say that is about right. The second thing I experienced was to make sure you put breather holes in your rocket in each section that cannot get outside air. I was trying to fly a rocket for the 1MMM contest. I had an 18" BT-60 tube, (my fin can) a coupler with a bulkhead and another 18" BT-60 on top of the fin can, with still another part on top that had an "Altimeter 1" in a payload bay. I made my couplers snug and on the coupler at the payload bay, I put clear scotch tape around the joint on the outside. I was again flying a G54. The launch was great. It flew high, and then it came apart. I got the fin can section back with a broken shock cord. I later on got the next piece of the rocket back (18" of BT-60) and that was all. The streamer was gone from the bottom of this section and the shock cord was gone also. Of course my payload bay with the altimeter and nose cone is gone ( and was never found at the time of this writing) I believe if I had drilled a vent hole into the first and second section of BT-60, this catastrophe could have been prevented. The pressure differential on the upper part was great enough that it pushed the 18" tube away from the coupling and payload bay, even though it had tape on the inside and the outside. but when you figure the volume fo air inside the closed cylinder pushing out or up against a decrease in air pressure fo about .825 lbs per 1000' of altitude increase, (for between 5000' and say 10,000'), then there was about a 40 lbs pressure differential and it made the rocket separate, so drill those .060" diameter holes to relieve air pressure as the rocket gains altitude. The payload bay would not have this issue because it had holes drilled in it for the altimeter. (If you find it, it has a dayglow orange nose cone and dayglow orange with gold chrome stripes on the BT-60 body tube and that tube is 8" long, so the unit is about 14" oal. If found I would apreciate getting it back.) I also learned that my laminated aluminum fins will hold up to a lot of stuff, but if bent, you will probably here the CA cracking as you try to bend them back. This could cause delamination. A fin that bends and does not break or shear is unique to me and presents it's own problems, but it looks like you can build a high performance aluminum fin that is only .030" thick and will hold together for at least one ignition. 😯
From the August launch I learned:
1. That my home made spring steel engine hook designed to hold a 29 6gXL works, so that is a good thing. I now have another way to secure a motor in a bird, without the screws and other hardware, or the use of tape.
2. That Dennis Billings found my 1MMM rocket launched at MHM about 200 yards to the west of the launch site, so that it came down behind where we were looking, which was to the south south-east.
The rocket looks like it came down fine but had water damage to the paper body tubes, hopefully from rain, for it may have been stepped on by a cow; that the sun faded all the paint/ coloring off of anything exposed to the sun; the nylon 18" chute that I purchased from Jon Skuba was deployed, but appears to have shriveled up like nylon stockings under a heat gun from the intense sunlight; that both deployment charges worked, so the Raven worked. I also learned once I got home and recharged the battery to the Raven that it appears to be working and it downloaded info showing the rocket made it to about 5100', at speeds up to 800 mph, that it survived 90 g's at liftoff, and the .030 thick aluminum fins worked and survived. (one was broken off, which could happen if a cow did step on it.) How about that, the Raven still works after being exposed (still in the payload bay, so partially protected, and the payload bay was intact.) to the elements for a little more than two months.
3. I also started flying an Aerotech Arreaux for the aphlabet clone contest and it worked very well for the 3 Fs and the 1 G that I flew on Saturday. The previous rockets had thin wall paper tubes and were working but they were not holding up to the stress of multiple launches.
4. Chad Moore flew a rocket powered with a large G for the 1MMM contest that is now continuing through the end of the year, (so there is still time for anyone else) He used an Altimeter 2 in his bird. He used thin wall paper, (maybe BT-60) and his rocket, unfortunately came apart. The Altimeter 2 showed on the display a velocity of about 1200 mph. Now we know more about the limits of thin wall paper tubes.
5. There were two young men who were attempting to receive their level 1 certifications. They both had the same kits, and they were both using the same size 38mm motors in their rockets. The motors were bigger than the designs called for and both rockets came apart under power a couple of hundred feet up. Another great example of pushing the limits and the limits winning. Good try though. Better luck next time gentlemen.
6. If you are using brass tubing for launch lugs, as in the rockets spoken of above, in no. 5, make sure you sand the gluing surface with course sandpaper so your adhesive works, since the launch lugs came off the airframe tubes.
7. I can clean a motor case very quickly and very cleanly with Hoppes No. 9, the same solution I use to clean my guns with. The motor case looked like new, with no scrubbing, just drop in, and then wipe off. I have used soap and water, WD-40, and other solutions and I have used vaseline and other lubricants, but I was amazed at how quicly the Hoppes worked.
That is all I can recall currently, but will annotate as I recall more. I hope this helps someone else and is useful.
Hoppe's #9... I never would have thought of it thought it makes total sense. The smell alone is nostalgia of going shooting with my dad too.
Talking of smell, tonight at a rock quarry west of Loveland, our men's group from church had a shoot-out. We had free food and drink and were shooting bows and arrows, pistols, shotguns, muzzle-loaders and rifles up to 50 cal. There must have been 300 hundred guys shooting and the smell of burnt powder wafting thru the air was quite refreshing. It sounded like WWIII. And a great time was had by all. Uh-rah! 8)
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