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Supersonic on a G?

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BlueNinja

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I've been thinking (maybe a little too hard) about making a mach buster. I'm not old enough to do L1, don't know anyone that would fly an H for me, but I'm on a budget high enough to buy Gs. Would it be possible to go supersonic on a G or would I have to find someone with an H to fly?
 

Ryan S.

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I think it is. G80 and G104 would be great for that, though I would use a G80 so as not to risk the casing

I once read a story of a bunch of guys that raced their mach busters on G80s. When they found them, the balsa nosecones had been torn apart because of the speed the wind was flowiing over them. They weren't pushed into the BT but it was like they had been picked apart. Very cool
 

jflis

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You can break mach with a G. I've seen it done with an F/E 2-stage. **proving** it is another thing all together :D
 

teflonrocketry1

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The Rocket Vision Mach Buster rocket has an ABS plastic nose cone with a phenolic body tube and G-10 fiber-glass fins. This design is very rugged. I can say this from experience since I shovel recovered mine a few times with flights on much smaller motors. The design flies great on C6-5 motors.

The 2.5 ounce, 13 inch long rocket easily does Mach 1.5 on a G55 motor and Mach 1.1 on an F72 motor. The problem is finding it afterwards, the G55 flight sims to over 1 mile AGL! It was once reported that there was only about a 30% chance of recovering the model from these supersonic flights.

Bruce S. Levison, NAR #69055, Rocket Vision's #1 Ask An Expert
 

BlueNinja

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Alright, this will probably be my first scratchbuild, need to get the flying tube off my mind. I would probably need fiberglass, after hearing the balsa nose story. Minimum diameter, small fins to reduce drag, what else?


Definitley SU motor. My budget's high enough for a couple of Gs but not for a couple of cases.
 

RocketboyG80

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I recently submitted a review of a mach buster I built to EMRR. If you read it, you will see I made a cheap one and a more expensive one. The expenisve one uses a PML 29mm tube and PML 29mm nosecone with 1/32" G10 fins. The cheap one uses a LOC 29mm tube and an Estes BT-55 nosecone (I cut it down to the correct size and attatched an Econojet spacer for a shoulder) with 1/32" G10 fins. They both fly great; especially on G's. EMRR
 

BlueNinja

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Cool! May I request permission to build that design?
 

Neil

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OK. I gotta chime in. The Hawk Mountain Raptor can do mach one on an H125, but you said you couldent do that... I hear a G125 could do it. And heres a review for my Mach Buster 1. I encourage you to build one of those. Also look at the Performance Rocketry page and see about buying a 29MM fincan. Those are cool. I havent got one yet, but I will soon. I need another 29MM mach buster. MB1

That ones cool. It can do mach 1.75 on a J570W! It can also fly on as little as an F20-4W!
 

BlueNinja

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I just may be able to find someone, our club president is (i believe) L2, but I don't want to use somebody else's motors for this. I'll try your design.


$80? Ouch. A little too expensive, but I will try to find ways to make it cheaper.
 

Neil

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If you made your own nosecone and used different shockcord stuff it would be much cheaper.
 

RocketboyG80

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If you decide to go the cheap route you can certainly build my design. I wouldn't try to stop anyone even if I didn't give permission because I like to see my designs used by others.
 

rstaff3

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In my book, posting a design on EMRR is tacit approval to clone it in part or entirety :)

I have built several G machbusters and near-machbusters including the RV kit (the casual observer can't tell the difference off the pad and you don't see them thereafter). The only one I got back was a Pratt Tomahawk on a G35 which only got to ~0.9 mach. Of course they were all flown on smaller motors so they could have more than one flight.

One tip is to not scrimp on the Kevlar shock leader. The ejection charge of a G is pretty energetic for a short minimum diameter tube. Also, most will optimally require a longer delay than the -10 that is available on a G80.
 

HiflyinPRguy

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I've also been thinking about building a Mach buster and I've seen some really good ideas here. I particularly like Neil's use of the fin can because I had designed a similar project (Code name: Screaming Beagle). But I get distracted too easily and that fell to the wayside.

Now, I got bored a few nights ago and started looking around my workshop to see what all I had in surplus parts. I found a leftover NCR motor tube. It's 17" long and has a non-standard diameter of 28.5 mm BUT you can delicately sand the tube and put an AT G-80 in it with ULTRA-TIGHT fit.

What if: I add thrust ring, attach some of those Aerospace composite fins from Giant Leap along with a 1/8" tubular kevlar shock cord and mylar streamer, persuade a bt-55 nose cone to fit (or turn my own hardwood version), attach 1/4" lugs, glass the whole thing, pray, and send it off.

What if...Hm......:D
 

Neil

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Is that a play on the Screaming Eagles or something?


Go to Performance Rocketry . Take a look at thier fincans. If you got a 29MM fin can, you could put it on your NCR motor tube, and you would get a VERY cool mach buster. You should fiberglass the tube for that, though. That will also build it up to the correct size for the fincan. Use a PML solid-urethane nosecone. Those work great, and the paint sticks to them VERY well, for some reason.

I dont reccomend you put a thrust ring on the inside the tube. Just wrap some tape around the nozzel end of the motor, and that will make a good external thrust ring. Then you can use longer motors (say H125, H124, H70 or H55.....) to get to greater speeds. You should also consider getting a motor retainer so you can use reloads. You can use reloads without it if you are very good at friction fitting, but I prefer motor retainers, especially Slimelines. Those are great retainers.




BTW, welcome to the Forum!
 

DPatell

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http://hometown.aol.com/dppgoalie1/29Mach.html

Thats a link to the page about my 29mm Mach buster. Loc Tubing and a custom turned Pine nosecone. G-10 fins, can take up to a 29-240 casing:) If I remember right I fully fiberglassed it. I hope I did...

I was told of a very good way to mount the shock cord, and I used it on this rocket. First, you cut a piece of coupler for the size of tube you are using to about 1 or 2" long. Then halfway up the coupler, drill a 1/4" hole through both sides. The put a piece of 1/4-20 allthread through the holes and file it flush with the OD of the coupler. Then you tie your shockcord, hopefully Kevlar, to the all thread and epoxy the heck out of everything. Place about an 1" higher than any motor you plan to fly the rocket on and glue in. Should work great!
 

HiflyinPRguy

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Originally posted by Neil
Is that a play on the Screaming Eagles or something?
Thanks for the suggestions, guys. Neil, the name "Screaming Beagle" is an homage to my dogs (7 beagles) and the design was also reminiscent to the old Estes Screaming Eagle, a rocket I had when I was younger. The Screaming Beagle will become a reality ONE DAY with one of those fin cans you suggested (thanks again). Also, after looking at Performance's stuff, there may be a staged HPR Nike Apache in my future :D

I was designing this rocket (the NCR tube one) to be as light as possible, fly supersonic on a G, and I am trying to do it all as inexpensively as I can. I was going to use the thrust ring because it is easy to make and adds some structural stability, even if its negligable. I had considered a Slim Line but I did not want to add any more weight than necessary and it seemed like a little overkill for a rocket that I'm not sure I will ever see again. I did not plan to use reloads in this rocket for that same reason, didn't want to risk the casing.

DP - Have you flown a rocket using that method for shock cord attachment? It sounds good, I just want to know how it holds up.
 

Tallman

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It's doable. We did it with some LOC 24mm motor tube cut slightly longer than RV Machbuster body tube, eyeballed their fins and did 1/16 basswood versions, then expoxied those on. Used a BT-50 nose cone with just a little weight. The basswood was strengthened with thin CA and came out like glass. Streamer recovery. It went well over Mach on a F-101 and was recovered. Fell to a rock-hard playa undamaged. Weight's your enemy - avoid glassing, fiberglass, etc. if possible. Basswood, expoxy fillets, cheap plastic nose cone and LOC tube are just fine - and easier.
 

Neil

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You gotta be kiddn..... No glass on a mach buster????? Itl shred for sure, unless you use some kind of super-strong heat risistant tubing.... Huh. Do tell. Howd you do it? Is there a review on EMRR I can copy and use? Can I have plans? And where did you get that F101T?

I made a micro-mach buster.... ultra thin basswood fins, plastic nose cone, 18MM minimum diameter, epoxy fillets and thats just about it. Mach one on an AT D21. I havent flown it yet, but its gonna be cool! itl just go wicked fast, possibly shred, and come back with a small streamer or something. HEHEHEHEHHEHEHEHEHE! Single Use motor in a single use rocket! I wont see it again itl go straight up and out of sight, never to be seen on this planet again! Either that or I will just fly it on a B6-4 a few times. Some kid in Rocket Camp a few years ago made something similar, but WITHOUT FILLETS, only wood glue holding it together. We were picking up fins ETC for ages.... Best part is mine only cost about $5 to make.....
 

Tallman

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LOC motor tube is strong stuff - a bit sturdier than the stuff Red Arrow sells and BMS' "BT-50 HD". Basswood/thin plywood is likewise plenty strong (at least when soaked in CA) and the MB fin shape itself is small and very stiff. Try it! These things are hard to recover (less so out here in Calif. on dry lakes) and G-10 plus glassing isn't necessary and significantly lessens top speed due to weight.
 

Neil

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Coooooool! I wanna try that once I have the money....
 

DPatell

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No flights on my 29mm Mach Buster, but the 24mm Machbuster is doable. Mine had 1/8" balsa fins with 1 layer of 4 oz glass fin to fin, and 0.75oz on the body tube. Flew amazing on an F101, but CATO'd on an F72. I doubt it would even need the fiberglass.
 

rstaff3

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HiflyinPRguy,

I built a machbuster type rocket using a BT-55 cone, but it took some trimming. I used a small piece of a 29mm SU casing as a replacement shoulder. It worked fine. Mine was phenolic, but glassing shouldn't be necessary on a short rocket.

Is the Giant Leap composite stuff a good choice? I forget what thicknesses it comes in.

Finally, before sticking a reloadable casing in it, remember this has a high probability of getting lost :)
 

Rocketjunkie

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Originally posted by Neil
You gotta be kiddn..... No glass on a mach buster?????
A stock Estes Gnome will survive 1000 mph on a D40.
 

HiflyinPRguy

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rstaff3,

The nose cone is the only part of this project I have completed so far and I did it in the manner you suggested with a spent G80.

I haven't tried the composite board yet but I'll probably order some next week. I plan on either using the dowel/epoxy filling method or using wire and epoxy like my dad uses on his fishing lures. I might also order a Fireball for my 4" PE BullPuP:D

Glassing seems to be the lesser of two evils:

Glassing =More weight = Less Speed but more strength. I'll need the strength considering part of the tube will have to be ground away to fit the engine in.

No glassing = less weight but the rocket becomes a flying orgy of disintegration and destruction.

As an alternative to glass, I wonder what soaking the tube in thin CA would do?
 

BlueNinja

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That would be a cool project... "How Low Power a motor can you break mach on?
 

Neil

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D21-7T. 18MM minimum diameter. I have one that is mach capable on that motor. I need a tower launcher to fly it, though.
 
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