Min Diameter drag racer

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T34zac

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Ok, so I thought I might try my hand at a build thread. Design will be simple:
-Conical nose cone
-38mm body tube (I'm leaning toward phenolic)
-Will take a 6-grain CTI casing
-around 4.5 feet tall
-Three fin design

So what had prompted this? Well I'm launching with MMMSC this weekend out in Berwick, ME. I went to their website to make sure I had the dates right and saw this:
ImageUploadedByRocketry Forum1407981749.333341.jpg

And I know, the I800 is a 4-grain motor not a 6-grain. I only have a 6-grain casing with two spacers and I don't feel like it would be worth it to get a 4-grain casing, especially when I can use a 6-grain motor and try to kiss the waiver at a later date.

I thought this would be a great excuse to build the min diameter rocket I've been thinking about doing for a while.

Now I don't have any simulation info yet (nor have I ordered parts), but I wanted to start this (so I wouldn't forget) and to ask everyone else about some of the parts I will be ordering.

Now I've ultimately decided on the PML 38mm conical Urethane nose cone. Is this any good? I've only used fiberglass in my high power rockets so I'm not familiar with this material.

Im also going to use phenolic tubing for this build. Or should I use LOC tubing? Again I've only used fiberglass so I'm unfamiliar with these build materials.

I'm also going to use plywood fins. Is 1/8" 3ply good enough? Or do I want something better?

Also, if you feel like giving a name suggestion, feel free. Although I do get the final say on the name.
 
I would use Blue Tube, and a single 4-foot piece at that, with a short section at the front which would be for attaching the nosecone to a coupler avionics bay of whatever length.

The PML urethane nosecone is solid material (not hollow), and isn't very long. I don't know how durable it is, I have only handled one.
 
So I am playing with the exact same thing and asking the same questions. I wonder if LOC w/o FG coating is strong enough. I also wonder if plywood w/o FG is strong enough. I have looked at the Wildman BlackHawk. It is a FG min. diameter rocket in 24, 29, 38 and 54mm. A min diameter 38mm will go super sonic on most I motors, so that is something I am considering when picking materials.
 
Well I have now decided on a primary build material. My father has (somehow) convinced me to use carbon fiber, saying that I can use this rocket to go for the single motor I altitude record at LDRS 34.

I will use just under 3' of tubing and build the fins out of two plates of 1/16" carbon epoxied together (these sheets are gloss one side and rough on the other). The nose cone will most likely be Performance Rocketry's 5:1 VK g12 nose cone.

The finish will be bare carbon with a layer of clear coat, polished smooth for max performance.

I'm also going to fit it for a 5-grain CTI case instead of 6-grain. The reason being is that a 6 grain case would require me to get a 4' section if cf. The savings from getting a 3' section will pay for the 5 grain case, allowing me to archive max altitude. Also, the shorter rocket goes higher.
 
Well I have now decided on a primary build material. My father has (somehow) convinced me to use carbon fiber, saying that I can use this rocket to go for the single motor I altitude record at LDRS 34.

I will use just under 3' of tubing and build the fins out of two plates of 1/16" carbon epoxied together (these sheets are gloss one side and rough on the other). The nose cone will most likely be Performance Rocketry's 5:1 VK g12 nose cone.

The finish will be bare carbon with a layer of clear coat, polished smooth for max performance.

I'm also going to fit it for a 5-grain CTI case instead of 6-grain. The reason being is that a 6 grain case would require me to get a 4' section if cf. The savings from getting a 3' section will pay for the 5 grain case, allowing me to archive max altitude. Also, the shorter rocket goes higher.

You won't need carbon fiber to break the record, not by any means. You just need a straight flight on a near optimal rocket: the current I record was on a flight that ended up 20 degrees off vertical in a rocket designed for another goal entirely. It simulated to 15000 feet but only achieved barely over 10000. Don't waste your money on carbon.

Here is the build thread for the current Tripoli I holder: https://www.rocketryforum.com/showthread.php?44148-Disappearing-Act-Minimum-mass-I1299-rocket
 
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You won't need carbon fiber to break the record, not by any means. You just need a straight flight on a near optimal rocket: the current I record was on a flight that ended up 20 degrees off vertical in a rocket designed for another goal entirely. It simulated to 15000 feet but only achieved barely over 10000. Don't waste your money on carbon.

Here is the build thread for the current Tripoli I holder: https://www.rocketryforum.com/showthread.php?44148-Disappearing-Act-Minimum-mass-I1299-rocket

Thanks for the info but I think I'm going to stay with carbon. I'd really like to shatter the record. My sims are only hitting 11299 right now with an I216, so I wonder what I'm doing wrong...
 
Thanks for the info but I think I'm going to stay with carbon. I'd really like to shatter the record. My sims are only hitting 11299 right now with an I216, so I wonder what I'm doing wrong...

Smaller and lighter. Unless you go with hand-laid tubing, paper products will be lighter and easily strong enough.

Also, ditch the fiberglass nosecone. I used a handmade balsa one.
 
Smaller and lighter. Unless you go with hand-laid tubing, paper products will be lighter and easily strong enough.

Also, ditch the fiberglass nosecone. I used a handmade balsa one.

Yeah I can remove more of the body tube and reduce the weight by more than a few Oz. Do I will do that when I get home. I'm also starting to rethink the G12 nose cone
 
Yeah I can remove more of the body tube and reduce the weight by more than a few Oz. Do I will do that when I get home. I'm also starting to rethink the G12 nose cone

Just as a reference, Disappearing Act weighed only 0.75 pounds empty.

Another thing to try is using a longer burn motor, like the CTI I125.
 
Just as a reference, Disappearing Act weighed only 0.75 pounds empty.

Another thing to try is using a longer burn motor, like the CTI I125.

Thanks for the weight reference. I keep finding ways to reduce weight (and overall length). Now I only need to but 2' of CF tubing. This project keeps getting less expensive.

I'm still at work so it will be a while before I can update OR on the design changes. Also, does anyone know the weight (in oz./ft) 1/8" tubular Kevlar?
 
Thanks for the weight reference. I keep finding ways to reduce weight (and overall length). Now I only need to but 2' of CF tubing. This project keeps getting less expensive.

I'm still at work so it will be a while before I can update OR on the design changes. Also, does anyone know the weight (in oz./ft) 1/8" tubular Kevlar?

Once again, you DEFINITELY don't need CF unless you're going to turn around and stick a J530 in it.

Secondly, your fins are way overkill, and hurting your performance: just use a single piece of 1/16" FR4 for them. Disappearing Act used CF-laminated fins primarily because we had just made a big panel of the stuff in my club and they fit in the scrap.
 
Once again, you DEFINITELY don't need CF unless you're going to turn around and stick a J530 in it.

Secondly, your fins are way overkill, and hurting your performance: just use a single piece of 1/16" FR4 for them. Disappearing Act used CF-laminated fins primarily because we had just made a big panel of the stuff in my club and they fit in the scrap.

I'm aware I could break your record without CF. But if I can get a higher altitude with CF, then I will use it. I'm going to run sims with a whole host of different materials. The whole point is maximizing the possible altitude. If I can make this rocket fly higher on an I motor than anyone else for years to come, then I will.

I was also planning on reducing the thickness of the fins too. 1/8" is way too thick. I originally planned on 1/16", but I forgot that I was and put 1/8" instead.
 
I'm aware I could break your record without CF. But if I can get a higher altitude with CF, then I will use it. I'm going to run sims with a whole host of different materials. The whole point is maximizing the possible altitude. If I can make this rocket fly higher on an I motor than anyone else for years to come, then I will.

I was also planning on reducing the thickness of the fins too. 1/8" is way too thick. I originally planned on 1/16", but I forgot that I was and put 1/8" instead.

Running simulations with different materials only is impacted by weight. Depending on the motor you may have an optimal mass of as low as possible, as with long burning motors, or it could have some non zero value to aim for.

If you choose a slow burning motor you should pick the lightest material possible, which is possibly plain phenolic. Carbon fiber is only going to net you better altitude by letting you use very, very, very little of it. Commercial CF tubes are far thicker than needed in the smaller sizes, so I strongly urge you to avoid using them if you are trying to optimize. You don't have control over the most important parameter.
 
Running simulations with different materials only is impacted by weight. Depending on the motor you may have an optimal mass of as low as possible, as with long burning motors, or it could have some non zero value to aim for.

If you choose a slow burning motor you should pick the lightest material possible, which is possibly plain phenolic. Carbon fiber is only going to net you better altitude by letting you use very, very, very little of it. Commercial CF tubes are far thicker than needed in the smaller sizes, so I strongly urge you to avoid using them if you are trying to optimize. You don't have control over the most important parameter.

When you say far thicker, how thick do you mean?

The stuff I was planning in buying is 0.05" wall. Phenolic is 1/6" wall. That being said, however, the phenolic is lighter in a 3' length than the CF is. Still at work so I haven't looked at the other materials weights until now...

This project is getting cheaper still!
 
The price will go up again when you realize that you need a tracker.
 
Ok so it's back to the original plan (almost).

-Phenolic tubing about 2' long (I would really like to thank CarVac for opening my eyes there).

-Nose cone will probably be balsa wood turned on a wood lathe.

-1/8" tubular Kevlar shock cord, still trying to decide on a length but 9' seems to fit. Could probably go shorter though.

-1/8" plywood bulkheads

-RRC3 altimeter for deployment. Dual deploy, drogueless.

-Fins are still undecided however.
 
Got my altimeter today. Ground tests look good for use with 7.4v li-po. Just one more thing that saves weight.

On a side note, I will probably use this altimeter for most of my projects. I'm going to do my L2 certification in two weeks (same day I launch this on it's maiden voyage/drag race).
 
Got my altimeter today. Ground tests look good for use with 7.4v li-po. Just one more thing that saves weight.

On a side note, I will probably use this altimeter for most of my projects. I'm going to do my L2 certification in two weeks (same day I launch this on it's maiden voyage/drag race).

For the record, for the record you will have to use (fit) a Raven in the avionics bay.
 
I'm aware. I was planning on using the raven as the flight computer for the actual attempt, but for now I will use my own RRC3.

If you are into optimizing, keep in mind that the RRC3 is about 2.5x larger. It will also have significantly different wiring; the Raven is fairly unique.
 
If you are into optimizing, keep in mind that the RRC3 is about 2.5x larger. It will also have significantly different wiring; the Raven is fairly unique.

I'm aware of that. I'm thinking of buying a raven anyway. However for now it will use the RRC3. I will have spare tubing and about year of time, I'm sure re-optimizing for the raven will be no big deal.
 
So I thought it was high time this could use an update.

I have been working a lot on OR to optimize the design of the rocket and i now have a (hopefully) final design. The entire rocket will stand 29.5" tall, empty it will weigh 9.5 oz (weight of the av-bay is estimated, will probably be heavier along with nose cone), the body tube will be a total of 22.5" long (with only 3" to fit the shock cord/parachute), the fins and bulkheads are going to be made out of 1/16" G10.

My Father an I have been calling it MD-38 until we can come up with a name. If you feel like you have a name/color scheme, by all means PLEASE share.

For the drag race in two weeks (on a CTI I800) it is expected to hit ~9,312'
Max speed: Mach 1.48

When I go for a record attempt (on a CTI I216) it is expected to hit ~13,557'
Max speed: Mach 1.6

Screen Shot 2014-08-17 at 1.10.46 PM.jpg
*shown with motor casing

Screen Shot 2014-08-17 at 1.13.54 PM.jpg
 
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So I thought it was high time this could use an update.

I have been working a lot on OR to optimize the design of the rocket and i now have a (hopefully) final design. The entire rocket will stand 29.5" tall, empty it will weigh 9.5 oz (weight of the av-bay is estimated, will probably be heavier along with nose cone), the body tube will be a total of 22.5" long (with only 3" to fit the shock cord/parachute), the fins and bulkheads are going to be made out of 1/16" G10.

My Father an I have been calling it MD-38 until we can come up with a name. If you feel like you have a name/color scheme, by all means PLEASE share.

For the drag race in two weeks (on a CTI I800) it is expected to hit ~9,312'
Max speed: Mach 1.48

When I go for a record attempt (on a CTI I216) it is expected to hit ~13,557'
Max speed: Mach 1.6

View attachment 181550
*shown with motor casing

View attachment 181551

3 inches is extremely optimistic for the parachute and shock cord. Put it together before cutting the tubes...
 
Yeah that was the plan. I figured that it's mathematically possible to fit the shock cord 1 cubic inch, so in pretty optimistic for the chute
 
Yeah that was the plan. I figured that it's mathematically possible to fit the shock cord 1 cubic inch, so in pretty optimistic for the chute

The parachute usually doesn't like to fit around things... also, the ejection charge definitely needs length (and the parachute needs protection from it).
 
The parachute usually doesn't like to fit around things... also, the ejection charge definitely needs length (and the parachute needs protection from it).

The ejection charge canister (that I used yesterday) is going to be a small plastic bag with the appropriate amount if BP and the e-match inside. Then it's just taped down with masking tape.
 
The ejection charge canister (that I used yesterday) is going to be a small plastic bag with the appropriate amount if BP and the e-match inside. Then it's just taped down with masking tape.

1. That doesn't work at high accelerations. I lost Disappearing Act on the I1299 because the ejection charge fell off.

2. It can break due to packing the recovery train in so tightly.

3. Holding it tightly against everything else in there is a recipe for burning them.
 
Just ordered The Aeropack MD retainer and CTI adapter. This build has officially taken off!

Will be ordering airframe components from PML soon, just need to supply them with a custom fin template.

Nose cone has also been decided, it's going to be a 5.1" long ogive nose cone made of spruce. Will be made from a 2" diameter dowel turned on my fathers wood lathe.
 
Tracking for this rocket (and all future projects that require it) has been solved. I have a friend who is more than willing to let me use one of his trackers in my rockets that need them.

Also made an order to PML this morning. I'm hoping to have everything except the fins within the week.
 
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