# High Speed Flight

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#### GrossApproximator

##### Well-Known Member
I've found quite a few threads on this forum about small, mid power supersonic rockets. What materials do you guys use? Do you use fiberglass tubes, or are the paper tubes lighter? Do you use balsa wood or some other material for fins? I'm just curious.

##### Well-Known Member
That is a good point, me and The EGE have started quite a few threads about machbusters, but we never mention what meterials we use. For my 18mm machbuster#1 I used a swept double delta fin shape with 1/8 balsa that was laminated with paper skins and was soaked thoughly in CyA I used a estes body tube with a standard apogee parabolic nose cone, my second machbuster which I am putting more money into, will use thin G10 fins (I changed my mind again) and is useing a fiberglass tube from USR (they have a shaky reputation but they do have a 18mm fiberglass tube) Should USR maintain it's reputation**cough I will use the standard estes tubing, the fin shape this time is a cliped double delta with a reducing stake at the end.

Ok here is the short version: Balsa and Basswood are ideal for 18mm machbusters and 24mm machbusters because the largest engines of those class the D21 and the F32 can bearly go past Mach, regular estes tubing is good for Mach flights, with 29mm machbusters there are more options the largest SU motor being the G80, but the largest AT motor being the I200, Bluetube is ideal for these flights, you can use G10 here, but it is overkill, nose cone meterial for all machbusters should be hard balsa or a hollow fiberglass/plastic.

#### The EGE

##### Well-Known Member
You will notice, SD, that I've started exactly one thread about Machbusters, a build thread in which I explain exactly what I used to build mine.

What materials you need depends on what size motor you'll be using, your skill level, and the weight of the final rocket. However, there is no mid-power motor out there that requires advanced materials to build a Machbuster.

I'm going to ignore 18mm Machbusters here, because they're not worth the effort. Extreme weight requirements (< 20g), no payload ability, difficulty in tracking, yadda yadda yadda. Not worth your time.

For 24mm Machbusters, you have two options. You can go for the Aerotech F32T, which is a single-use motor. It'll allow you to use paper tubing and 1/8" balsa fins; or 3/32" basswood, so long as you make good fillets with wood glue. Or, you can choose to take the risk of losing an expensive casing, and use CTI Pro24 or Aerotech 24/120 casings. The longer casings will give you mid-to large G motors - eventually even a baby H from CTI - but they're expensive and require better building. If you want to use 24mm reloads, you could use ordinary paper tubing, but adding a layer of half-ounce fiberglass might be a good idea. Or get the the Blackhawk 24 which is not cheap and is carbon fiber, but will survive any 24mm motor. Any.

You've also got two options for 29mm Machbusters. LOC tubing and 1/8" plywood fins will easily take up to a G80, and probably an H if you build it well. If you want to fly Is or you're on a hard desert, then fiberglassing or the Blackhawk 29 might be a better idea.

Also, consider this. Machbusters tend to go extremely high. A 29mm rocket on an G can easily hit 1 miles (5000+ feet), and a 24mm rocket on a G might go to 7000 feet or more. You will not be able to see the rocket at those altitudes, not even prolly with binoculars. You will need to put a lot of tracking powder in... baby powder, flour, and especially chaulk dust all work. You will see a little puff at ejection; launch on a windless day so that puff will be roughly above where it lands. Use a streamer that gives a descent rate of 20 to 25 fps.

For 29mm, consider dual deploy. It's a lot harder and requires a LEUP for the blackpowder, but it can easily increase the odd of ever seeing your rocket again by two or three times...

#### cjl

##### Well-Known Member
Paper and balsa/basswood is fine for 18-24mm. You just need to pay attention to fin shape and thickness.

I think I did leave out 18mm machbusters are one shot wonders, with the 29mm machbusteres you must put some investment in before you start saving money, 18mm machbuster can cost $15 per flight (new rocket and motor each flight) clipped deltas are ideal for machbusting FYI #### MarkII ##### Well-Known Member Building supersonic rockets is popular in HPR. It's not a waste of time in MPR; exceeding the speed of sound is just more difficult to do successfully and in a verifiable manner with small motors. The weight of the rocket needs to be kept to a minimum, but the use of epoxy is highly recommended. Composite construction is not necessary and it will usually cause the rocket to be overweight. Tracking the rocket at 2,000 ft. when it is traveling at > 770 mph will be quite a challenge, and so will be finding it afterward. In HPR, larger motors mean that larger supersonic rockets can be flown, and most of the other issues can be addressed much more easily as a result. Mark K. #### The EGE ##### Well-Known Member I think I did leave out 18mm machbusters are one shot wonders, with the 29mm machbusteres you must put some investment in before you start saving money, 18mm machbuster can cost$15 per flight (new rocket and motor each flight) clipped deltas are ideal for machbusting FYI
If you go into a flight knowing that you will not see the rocket again, and you fly that rocket in a way that will not permit you to recover that rocket, then you are doing it wrong. Recovery is every bit as important as flight.

If you cannot recover your rocket, then you don't have the skills to fly a small rocket to transsonic speeds. If you do not know enough to be able to recover a small rocket from 2500', then do NOT fly it, no matter how cheap it may be. There are ways to fly an 18mm rocket to that altitude and recover it better than 90% of the time. If you can't do it, don't do it.

Yes, my new 29mm Machbuster will cost more than a one-shot 18mm rocket. But I will be able to recover it on-field with high reliability, and fly it on a wide variety of motors so it's worth the cost to me.

Clipped delta fins are very good for high-speed rockets, and easy to make. There are designs that are a little better, but they're typically curver and harder to cut.

#### MarkII

##### Well-Known Member
Building, launching and recovering a small mach-buster is a significant challenge; nevertheless, one cannot demand that another rocketeer not attempt it because one deems the project as being unworthy of the effort. The other rocketeer may have different goals for the project than you might have, and may simply be pursuing it out of curiosity and a thirst for knowledge. Many people learn better if they have something physical to work with and get an opportunity to experience the process first-hand. That is basically what we all do in a hobby like this. A constructive response would be to advise the rocketeer of the issues that are involved and to point him to some helpful resources. Exploring the issues and finding ways to address them is how we all become more knowledgeable about rocketry. We also don't all follow the same schedule when we pursue our hobby. Nearly all of us go "out of sequence" at one point or another because a particular problem or challenge has grabbed our interest. It's a hobby, not an apprenticeship. Following an interest and trying something out are good ways to learn; if nothing else, the process may educate the person in what he doesn't know (I have reached that point SO many times) and may spur him to do further research. As the saying goes, we learn from our failures; successes don't teach us anything that we didn't already know. We all need to have the freedom to fail.

In the case of an 18mm mach-buster, the rocketeer may eventually come to the conclusion that making it conform to the Safety Code (building it to safely return to the ground using an appropriate recovery device and launching it so that it recovers within the launch field) involves solving some problems that are too formidable for him at the time, and so he may reach a dead end and never actually launch his rocket. But he will certainly know more at the end of the project than he knew at the start of it, and isn't that the goal?

I have recently been as guilty as anyone else of forgetting these points.

Mark K.

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#### cjl

##### Well-Known Member
Yes, my new 29mm Machbuster will cost more than a one-shot 18mm rocket. But I will be able to recover it on-field with high reliability, and fly it on a wide variety of motors so it's worth the cost to me.
High reliability?

It is quite a challenge, even with a 29mm. My largest loss (monetary) from a lost rocket is still a 29mm machbuster I built back in Nov. 2006. The tube and fins were hand made CF (the fins were ~0.035" thick, the tube was 2 wraps of 2oz carbon - the rocket was scarily light - the airframe, including fins, weighed just under half an ounce). It had a small altimeter on board, and was launched with a G80. I never saw it again.

Here's a picture:
http://i27.photobucket.com/albums/c183/chris_lapanse/DSCN5567.jpg

And launch:
http://i27.photobucket.com/albums/c183/chris_lapanse/30718303258.jpg

##### Well-Known Member
If you go into a flight knowing that you will not see the rocket again, and you fly that rocket in a way that will not permit you to recover that rocket, then you are doing it wrong. Recovery is every bit as important as flight.

Yes, my new 29mm Machbuster will cost more than a one-shot 18mm rocket. But I will be able to recover it on-field with high reliability, and fly it on a wide variety of motors so it's worth the cost to me.

Clipped delta fins are very good for high-speed rockets, and easy to make. There are designs that are a little better, but they're typically curver and harder to cut.
#1 recovery of any LPR rocket at 3000+ feet feet is a tedious challange, all you can do is help it all you can (powder, shiny stuff) and launch, you may or may not get it back, but that is the same with all rockets, you may believe that you will get it back but fate may have other plans for your rocket, most likely as a tribute to the rocket gods.

#2 As I stated before there are no certainties, and I was stating that it would be cheaper in the event that I were to lose the rocket

#3 Score 3 for JR.!!! :wave:

#### The EGE

##### Well-Known Member
MarkII: You're certainly right on all points. I've been guilty of this a lot lately.

It just... unnerves me that SD seems willing to have a one-shot rocket that it sounds like he might not even attempt to find, which I read to be a violation of the safety code.

I don't personally find 18mm machbusters to be worthy of my time; other might and that's fine, as long as they a) stay within safe and practical limits, like the need to be able to recover your rocket and b) post about their builds and flights, cause I like seeing cool stuff

cjl: 29mm minimum-diameter rockets are hard to recover, true; however I personally find them easier, primarily because their weight restrictions (for beign able to break mach) are not as tight, so one can include more tracking powder and perhaps dual-deploy electronics.

My Sudden Mach is to be built from LOC tubing, and DD is with a cheap timer. But between the parts, timer, and a 29mm motor case, I'll still have 60 bucks invested it in, so I'll only launch it to greater than 2000 feet at NERRF with a wide open field and lots of eyes. I'm pretty confident, though, because I recovered the Machnum Force from 4500 feet with less powder and no DD; lower flights will remain visible even at apogee and will be much easier to recover.

Time for the EGE to go to bed. Gnight, all.