Good point, John. You and others have gotten Mach rash... will Tony be the first with re-entry rash? Time for some ablative paint, one that is actually meant to anyway. This thread will get a lot of people thinking, very nice.

Yes....I am ready for lesson #2

For what it's worth, my Kestrel had only minor mach rash. It reached M1.9 and ~27K. Lost about 1" of paint on the nose tip and about 1/8 to 1/4 on the fin leading edges. I was using very pedestrian paint- Rustoleum with Kilz underneath.

Sort of "fashionably burnt."

Lesson #2 ..ramblings

There's really no secrets to flying high. I'll start with the motor. Use the smallest diameter and fullest newtons for the class. If you have your choice go with the longest burning motor. The problem with short burn motors is, you loose altitude the faster you go.
Now that you know the diameter of the rocket..how long does it have to be? Make it as short as you can. Does it really need to be dual deployment or can your bring it down fast on a small chute from apogee? Does your launch site allow the space for this? Longer rockets have more resistance which means less altitude. Going back to diameter of the rocket. How thin can I really make this body tube. When I say thin..I'm talking OD of the tube. How much less resistance is there between a hand rolled body tube of 3 layers of 5.7 oz carbon fiber compared to an off the shelf fiberglass body tube?
Fins...use the thinnest you can. Carbon fiber are going to be the thinnest for strength. How thin is thin? It depends on the fin shape and how the fins are going to be attached. When I do tip to tip. I count on this for strengthening my fins. I have a buddy who use .063 G-10 for his fins on a 54mm min dia rocket. I used .125 G-10 on a 5" min dia rocket that flew on a 5" P motor. As for fin attachment I feel that fin slots add a lot to the whole fin attachment and strength set up. I fly with guys that have been using carbon fiber tissue for fin attachment. This is really pushing things..and sometimes pushing things does not work so well. I've seen "JB weld" fin filets only work very well too. This all goes to what are the thinnest fins or construction methods that are strong enough to do the job. I feel that on almost any rocket that is tip to tip with 1/3 - 2/2 - full using 5.7 carbon fiber is way over kill. They will never come off.. even when they lake stake at 165 mph. I know this for a fact!
Use a boat tail. sims don't show that much benefit from suing them but they do gain altitude. All the above things add up. Run Optimal mass sims for your rocket as you build it. Keep track of how much you rocket is weighing. I'd rather use a stronger building technique then to have to add dead weight to a rocket to reach my optimal mass. Each motor with have a different optimal mass for a rocket.

End of Ramblings...

Tony

more personal ramblings...

my history of min dia rockets.. My first min dia rocket was back in about 2000. It was your basic cardboard tube with a couple of layers of glass on it. I built it long enough to take a K250..it even had an acme fin can on it. It's the yellow rocket in the below photo..it looks like I got 15,348 out of it. at the time that was pretty good.

Shorty there after my son AJ (14 years old at the time) came up with the idea to use the motor case as the couple. In 2003 I built a rocket that used this idea and made it as short as possible. It took the AT 54/2560 and flew to 19,936 mach 1.98 43" long..still cardboard and glass construction.

In 2006 I switched to carbon fiber and was heavy into Ex motors The below rocket flew to 29,040 at mach 2

The same building techniques in a 75 mm rocket with an AT M650 flew to 35,250

Lately I've been doing away with as much as the body tube as I can. Just sliding a fin can on to the motors and some upper rocket to hold the electronics and chute. Below is a 5" min dia with a 5" P motor. It flew great but was "misplaced"

I did a 98mm version that flew great but made a hole in the ground some place out at Black Rock. I flew a 3" version at Balls last year and got it back. This year I'm going to play around with welding fins to the motors. I hear it won't work but I'm slow and need to prove things to myself.

Tony

I'd be careful about welding to most motor cases unless you have the capability to re-heat treat the case after the welding. The ideal, from what I know, would be to make a case specifically for the purpose. Machine the exterior of the case, weld on your fins, then machine the inside of the case, then finally heat treat. A proper TIG weld of the fins will require substantial material deposited as fillets and will likely liquify the case material all the way through in the vicinity of the welds. This will require re-machining the interior of the case.

I have a bird designed for a motor case booster with a slide-on fin can. Sitting on the bench for a couple years now - never have gotten around to finishing it. I like the idea though.

Tony - What did you use to track those rockets? 30,000+ is impressive as heck.

Warren, Like I said in that post..I'm kind of slow and need to learn things myself. I like it when people say you can't do this or that because of something or other. Years ago I was told you could not use BP at high altitudes...I thought about it for awhile and came up with the latex tube idea. Seems you can use BP at altitude.
Batman, I sort of like hunting for my rockets. I only like it for about an hour and then it really starts to suck. I have walston and Bee Line Tx that I use. It's sort of still hunting with those..right? I do have a Bee line GPS..that I don't use..to me that's not much fun just driving up to your rocket. Believe it or not ..below is a link..this was one best rocketry adventures. I ran into John Wilke at the begining of the "Fun". It might make for some interesting reading on a cold Colorado night.

http://www.rocketryforumarchive.com/showthread.php?t=40353

Tony

That link in the previous post is way very cool. It is amazing that terrain like that is so close to the playa.

Indeed, the day Tony misplaced that rocket I was hopping around the desert in a cast (broken foot) and about 8-9 miles from the launch pad I bumped into Tony. Small world.

I still can't get over how the terrain changes out there. You think the world is totally flat, and the next thing you know you are winching a dirt bike up a cliff...

Tony, I don't know if I ever told you - my GPS shot craps that day. I had taken some pretty serious visual notes before leaving the car - and I'm glad I did. You could easily die out there.

I understand entirely Tony - I'm much the same way. I also blatantly steal good ideas where I find them and after reading your posts on this thread, I find that a bunch of idea I thought I stole from JW he apparently stole from you. 😀

I've built a couple birds with the motor case coupler concept as a for-instance.

I'm the first to admit stealing / borrowing from those who came before me.... I have indeed borrowed a thing or two from Tony!

There's no shame in sharing - why re-invent the wheel for every new bird?
Good ideas blossom and grow. Bad ones usually don't stick around long enough to catch on but I'd go ahead and do that if I were you.

And, just because no one else has been able to something doesn't mean YOU (the you being anyone) can't. That's the heart of invention. Drag is the enemy and Tony has shown ways around it. Textbook. This is a really a great thread! Without sharing no one moves forward. Thanks to all for the info.

To steal ideas from one person is plagiarism. To steal from many is research.

Hee, hee... among rocketry brothers, there is no theft, just mutual advancement. 😉