I've always liked high performance 29mm minimum diameter rockets. They're cheap to build and fly, there are some kick-butt motors to use with them, and design-wise they are challenging to fit everything in efficiently. The last time I made a 29mm rocket, I tested different nosecone shapes and collected Cd vs Mach number data using a Raven altimeter. Later I it went to 14,818 feet on an H (https://www.tripoli.org/Records/Commercial-H-Records) once I made my own nosecone with a Von Karmon shape. That rocket got destroyed in a 2-stage attempt.
For this build, I just want a reliable, high-performance flight test vehicle for my altimeters and GPS trackers. I'm going to trade some performance for cost and ease of building, but I'm hoping it will still be useful for those interested in going fast on a budget. My goal is to get this done in time for a launch on Nov 17, and show how inexpensive a really high-performance rocket can be. Below is a screen shot with open rocket, some rough guesses, and a motor loaded for a 132G flight.
Design:
For this test vehicle I'm going to make it long enough to fit the longest 29mm motors I'm aware of, and to use the "chute cannon" concept I've used before. I like the chute cannon approach because it allows dual deployment with a single airframe break, it makes the best use of the nosecone volume, and it keeps the electronics well protected. Both of my official altitude records used this technique. I'll show more of that as I go along.
For electronics, of course I will be using a Featherweight GPS tracker and a new Raven4 that I'm testing. I haven't decided yet whether I will use a stand-along magnetic switch or a 29mm Featherweight av-bay bulkhead. More on that later.
My strategy is to use carbon in the back end, so the fins and body tube can be light and thin for stability and low drag, and use fiberglass in the front end, to provide useful density, while being RF transparent, easy to work with, and electrically non-conductive.
Materials:
For tonight, I'm ordering airframe materials. The main body tube should ideally be about 15 inches long in order to fit the longest 29mm motors on the market. I'm going to do an inexpensive and easy woven carbon sleeve over thin cardboard for the main tube. Unfortunately, Apogee only sells their thin 29mm cardboard tubes up to 13 inches long. I think I will tape 2 together before doing the carbon over-wrap, or I might change my mind later and just stick with 13", and let my largest motors overhang a couple inches.
Main tube:
A 6-pack of cardboard tubes is $9.60.
The carbon overwrap from Soller composites (1.25 in diameter, 3k weave) is $5.70 for 5 feet.
The 1.9" clear heat shrink tubing is $12 for 5 feet. Note that for $27 in materials not including epoxy, I can make 5 feet of carbon-reinforced tubing, which is only about $6 per rocket.
The epoxy is actually the expensive part. The epoxy at Soller composites seems promising, with arated temperature of 210F. I have used Aeropoxy with success, and its Tg is 193. Every little bit helps when you're planning for supersonic flights. A quart of 820 system sold at Soller is $50, and it will bump up the shipping, too. But I'm due for some fresh stuff. Also buying some microballoons to make a lightweight putty for fin fillets, $13 for a many-rocket supply.
Fins:
I already have some precut carbon fiber fin core stock from a previous project, so they're free for this build. But if I were to make them again, I would start with thin carbon sheet stock like this https://www.cstsales.com/a-carbon-f...M6-vSXawsEZI9BR_D2Qr2reM6MJwPhoBoCTDYQAvD_BwE, which is $12.65 for 5.75" x 5.75" , plenty for 4 fin cores on a rocket this size. Most of the fin strength comes from unidirectional tip-to-tip carbon which I will add. A 12" x 12" square of lighter uni is $1.49. Release fabric for compressing the tip-to-tip layup is $7.
Nosecone:
Since I have a nosecone mold, I'll use fiberglass sleeves to make the cone structure. Carbon fiber would also be o.k., except I want to maximize my GPS performance, so fiberglass it is. I'm buying biaxial braided sleeves in nominal diameters of 0.75, 1, and 1.5 inches. Smaller ones go toward the front, and so on. 1 foot minimum quantity for each one adds up to a whopping $2.52. Most people will just buy a cone, but so far nobody makes 29m Von karmon cones, so you would need to settle for conical ones.
Coupler/Chute Cannon
A strong fiberglass coupler is important for those > 100 G flights. One from Madcow looks promising. And it's only $6. The chute cannon itself will be a leftover 18mm Estes cardboard tube reinforced with more fiberglass. I should have plenty of biaxial sleeve left over from the nosecone. The av-bay will need some fiberglass sheet stock that I will reinforce with more fiberglass. Madcow sells 1/16" plate in 8.5" x 11" size for $11.
I'm going to ignore the shock cord and chutes for now, and add up the damage:
Apogee rockets: $9.60
Madcow Rocketry: $21.43 (not including a replacement 38mm cone I'm getting for another build)
Soller composites: $104.6, most of which is enough epoxy and release fabric for a lot of builds.
For this build, I just want a reliable, high-performance flight test vehicle for my altimeters and GPS trackers. I'm going to trade some performance for cost and ease of building, but I'm hoping it will still be useful for those interested in going fast on a budget. My goal is to get this done in time for a launch on Nov 17, and show how inexpensive a really high-performance rocket can be. Below is a screen shot with open rocket, some rough guesses, and a motor loaded for a 132G flight.
Design:
For this test vehicle I'm going to make it long enough to fit the longest 29mm motors I'm aware of, and to use the "chute cannon" concept I've used before. I like the chute cannon approach because it allows dual deployment with a single airframe break, it makes the best use of the nosecone volume, and it keeps the electronics well protected. Both of my official altitude records used this technique. I'll show more of that as I go along.
For electronics, of course I will be using a Featherweight GPS tracker and a new Raven4 that I'm testing. I haven't decided yet whether I will use a stand-along magnetic switch or a 29mm Featherweight av-bay bulkhead. More on that later.
My strategy is to use carbon in the back end, so the fins and body tube can be light and thin for stability and low drag, and use fiberglass in the front end, to provide useful density, while being RF transparent, easy to work with, and electrically non-conductive.
Materials:
For tonight, I'm ordering airframe materials. The main body tube should ideally be about 15 inches long in order to fit the longest 29mm motors on the market. I'm going to do an inexpensive and easy woven carbon sleeve over thin cardboard for the main tube. Unfortunately, Apogee only sells their thin 29mm cardboard tubes up to 13 inches long. I think I will tape 2 together before doing the carbon over-wrap, or I might change my mind later and just stick with 13", and let my largest motors overhang a couple inches.
Main tube:
A 6-pack of cardboard tubes is $9.60.
The carbon overwrap from Soller composites (1.25 in diameter, 3k weave) is $5.70 for 5 feet.
The 1.9" clear heat shrink tubing is $12 for 5 feet. Note that for $27 in materials not including epoxy, I can make 5 feet of carbon-reinforced tubing, which is only about $6 per rocket.
The epoxy is actually the expensive part. The epoxy at Soller composites seems promising, with arated temperature of 210F. I have used Aeropoxy with success, and its Tg is 193. Every little bit helps when you're planning for supersonic flights. A quart of 820 system sold at Soller is $50, and it will bump up the shipping, too. But I'm due for some fresh stuff. Also buying some microballoons to make a lightweight putty for fin fillets, $13 for a many-rocket supply.
Fins:
I already have some precut carbon fiber fin core stock from a previous project, so they're free for this build. But if I were to make them again, I would start with thin carbon sheet stock like this https://www.cstsales.com/a-carbon-f...M6-vSXawsEZI9BR_D2Qr2reM6MJwPhoBoCTDYQAvD_BwE, which is $12.65 for 5.75" x 5.75" , plenty for 4 fin cores on a rocket this size. Most of the fin strength comes from unidirectional tip-to-tip carbon which I will add. A 12" x 12" square of lighter uni is $1.49. Release fabric for compressing the tip-to-tip layup is $7.
Nosecone:
Since I have a nosecone mold, I'll use fiberglass sleeves to make the cone structure. Carbon fiber would also be o.k., except I want to maximize my GPS performance, so fiberglass it is. I'm buying biaxial braided sleeves in nominal diameters of 0.75, 1, and 1.5 inches. Smaller ones go toward the front, and so on. 1 foot minimum quantity for each one adds up to a whopping $2.52. Most people will just buy a cone, but so far nobody makes 29m Von karmon cones, so you would need to settle for conical ones.
Coupler/Chute Cannon
A strong fiberglass coupler is important for those > 100 G flights. One from Madcow looks promising. And it's only $6. The chute cannon itself will be a leftover 18mm Estes cardboard tube reinforced with more fiberglass. I should have plenty of biaxial sleeve left over from the nosecone. The av-bay will need some fiberglass sheet stock that I will reinforce with more fiberglass. Madcow sells 1/16" plate in 8.5" x 11" size for $11.
I'm going to ignore the shock cord and chutes for now, and add up the damage:
Apogee rockets: $9.60
Madcow Rocketry: $21.43 (not including a replacement 38mm cone I'm getting for another build)
Soller composites: $104.6, most of which is enough epoxy and release fabric for a lot of builds.