Build Suggestions - Min. diameter 29mm (1.1") rocket with conical nose G80-13T

[RocketTree]

I have an AT G80-13T DMS motor sitting around here, and would like to make use of it.
Delay is not adjustable, so the rocket must be minimum diameter and lightweight.

Looking for recommendations and suggestions for rocket kits that would be suitable to replicate or scale to this size.

I already have some components:
- Conical Urethane Nose Cone 1.1" from Public Missiles. (6" length, 60 grams)
- 29mm (1.1" thickwall cardboard tube - up to 36")
- 29mm 1.1" piston for ejection system (if needed)
- G80-13T motor

A few possible ideas using this nose cone:
- PML Cirrus Dart
- Black Brant II
- Black Brant III

A cardboard tube 'cirrus dart' replica would touch Mach 1 if the fins are not too thick.



Ran into problems selecting fin material. What are my options that will hold together at this speed?

Needs to withstand one flight and land with streamer or small chute. If successfully recovered and able to fly again, that would be a bonus.

Must also be kept lightweight and low cost since it will possibly disappear into space.

 

[dhbarr]

UDDT ought to trim your delay just fine.

Ditch the piston ( unless you just really want the extra moving parts ) just use a baffle and barf.

Cirrus Dart would look great, I'd want to streamer it down faster than Brant fins would like. Something Smoke-like would let you land even harder.

Decent plywood fins ought to be okay, that 2oz nose ought to help keep you out of the worst of the mach trouble.

 

[David Schwantz]

Ply fins may be ok, but I would probably at the least glass the LE.

 

[RocketTree]

UDDT ought to trim your delay just fine.

I have the drilling tools, but I don't believe you can use it on standard disposable motors.

Maybe it can be done?



On a related subject, how does the Apogee Aspire hold itself together with balsa fins and a G80 motor..... are they papered?

 

[dhbarr]

My mistake, I thought we were talking about the g80nt-14a. Should still work the same, but I've no idea which of the several drilling tools would be right.

 

[Rocketjunkie]

In a minimum diameter rocket, the 13 sec delay will work fine. You CAN shorten the delay of a single use motor but it does require care and the tolerance will not improve over the longer delay (13 is 10.5 to 15.5 sec. Cutting it to 9 would be 6.5 to 11.5 sec). 1/16" to 1/8" thick plywood fins with even 5 minute epoxy will hold together. 5 min epoxy is stronger than the paper and wood rocket parts.

 

[jqavins]

Is delay drilling on these SU motors allowed under the safety code? I've read that removing the ejection charge is a manufacturer approved practice, and so does not count as disallowed modification, but drilling the delay is not manufacturer approved and is therefore not allowed. Am I wrong?

Modified engines can't be flown at sanctioned events. Of course, you can launch them on your own, if you're willing to kiss your NAR or TRA liability insurance goodbye (on that flight).

 

[Rocketjunkie]

Is delay drilling on these SU motors allowed under the safety code?

If the manufacturer allows it, it's OK with the safety code. Aerotech allows this.

 

[SDramstad]

What do you need a kit for? You have the design, just build it!

 

[cbrarick]

I think glassing fins is highly overrated. Just glue them on good

the bigger problem is that i wonder if the 13 second delay is long enough, should you fly a altimeter?
also do you have gps or a tracker? That thing is gonna be gone!

Any of your choices would be cool

 

[space.kerbal12]

Feather weight tracker or simple gps from apogee

 

[manixFan]

No need to glass fins for that speed. Getting the fins on as vertical as possible is important though when you go to Mach or beyond. You'll also want to make sure you have a very good bond to the body tube with decent fillets to help the fins survive landing. In my experience with MD rockets, far more fins break on landing than in flight.

I'm surprised your stability margin isn't higher based on how heavy I remember those nosecones being and how long your rocket is. If speed and altitude are your goal, shorten the rocket so you have just a 1.5-2x stability margin.

A long mylar streamer can help with visual tracking if you don't have an electronic tracker. I used to cut mine 4"-6" wide and 8' - 12' long from mylar wrapping paper and then tape the sections together. (A lot of rolls are 8' long so if you won't need to tape it if you get a long roll.) I then z-fold it to create fairly sharp creases (keeping the folded section under several books for a couple of days). I'd attach the streamer right near the nose cone and (if needed based on weight) a small chute near the body tube (about 1/2 the normal size). On a sunny day the mylar will flash in the sun as it whips around in the air making it possible to visually track the rocket. The z-fold creases seem to help slow it down better than a straight streamer. Not fool proof but inexpensive. Works best with motors that have decent tracking smoke so you can follow the rocket to apogee. Having a good spotter with binoculars also helps a lot. You would need to make sure you set up your piston (if used) to accommodate the length of the streamer when placed in the rocket.

Just a thought,


Tony