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29mm MD rocket "The Minute Man" (Build Thread)

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rockets

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Here is my build thread for my MD 29mm rocket.
Here is how everything will work:
DIMENSIONS
20 inch long rocket
14 inch long body tube
6 inch long conical nose cone
29mm diameter
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AERODYNAMICS
(3) 1/8 inch plywood fins
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RECOVERY
200 LB test Kevlar
12 inch mylar (sparkly) parachute
possibly some flower, as in the white stuff that you use in cookies, (for tracking purposes)
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ELETRONICS
PerfectFlite APRA altimeter
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LAUNCH
motor: AT DMS H195T (OR) AT DMS H135W
Launch pad; not sure yet
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TECHNIQUES:
I glue the fins to the tube with STRONG CA. Then fillet with 30 min epoxy
IMG_2672.jpg
4/3/2017 - I have a name for the rocket. "The Minute Man"
4/18/2017 Here is the finished product!
IMG_2693.jpg

SO LET'S BUILD!

Thanks,
 

rockets

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LETS BUILD!!!!!!I glued the fins to the tube with STORNG CA.
Tomorrow I will fillet the fins with 30 min. epoxy :)
IMG_2674.jpgIMG_2675.jpgIMG_2676.jpg
The fins are decently straight. Straight enough!! I'll get pictures later.
Thanks,
 

rockets

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I know the fins don't look very good. But, it should be a cool flight!
Today hopefully I can fillet the fins!
Thanks,
 

DGBrown

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You might want to consider chalk instead of flour. Flour dust is pretty flamable.
 

dhbarr

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Baby powder, leak tracing powder are also decent choices. Chalkline is pretty stain-y, but that's better than a flour bomb.
 

timbucktoo

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This is what happens when you put a 2 pound bucket of flower on the launch pad!

flower.JPG
 

TangoJuliet

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Red Tempera paint powder is a great tracking powder also.
 

Incongruent

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Try Creamola or whatever it's called - powdered coffee creamer - chock full of fats and sugar - they it to make fireballs in pyrotechnics. Also maybe have a concave bowl or bucket of sorts so it sprays the powder out.
 

Mr Rocket

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Baby powder, leak tracing powder are also decent choices. Chalkline is pretty stain-y, but that's better than a flour bomb.
+1 to the above. I use baby powder usually.

What are you using to retain the motor?
 

Incongruent

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I would advise, based on my spotty research, to stray away from a conical nose cone.
https://en.m.wikipedia.org/wiki/Nose_cone_design#
The chart here summarizes the information: https://en.m.wikipedia.org/wiki/Nose_cone_design#Influence_of_the_general_shape

Are you are you going to round (or bevel/airfoil, depending on your flight profile and how much you want to optimize performance) the fins? Depending whether the CA is on the exposed surface of the fins and body tube, (where the fillets will go) you might be able to use wood glue for the fillets, which is recommended for paper to wood fins. If there is CA on the surface, though, the wood glue won't be able to form a good bond.

What body tube are you using? Thin wall or thick wall?

Have you considered a launch tower?


There have been many 24-29mm minimum diameter rockets being built and shown on the forum by the young'uns... so peer pressure did me in.
Wood glue fillets and CA coated body tube and fins, wet sanded to 4000 grit. I don't know why I did that, co sitering tge chances of recovery. I want to recover, of course, but to quote Tom Lehrer('s friend), "always predict the worst, and you'll be hailed as a prophet."

IMG_2792.jpg


IMG_2794.jpg
 

TRFfan

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I would advise, based on my spotty research, to stray away from a conical nose cone.
https://en.m.wikipedia.org/wiki/Nose_cone_design#
The chart here summarizes the information: https://en.m.wikipedia.org/wiki/Nose_cone_design#Influence_of_the_general_shape

Are you are you going to round (or bevel/airfoil, depending on your flight profile and how much you want to optimize performance) the fins? Depending whether the CA is on the exposed surface of the fins and body tube, (where the fillets will go) you might be able to use wood glue for the fillets, which is recommended for paper to wood fins. If there is CA on the surface, though, the wood glue won't be able to form a good bond.

What body tube are you using? Thin wall or thick wall?

Have you considered a launch tower?


There have been many 24-29mm minimum diameter rockets being built and shown on the forum by the young'uns... so peer pressure did me in.
Wood glue fillets and CA coated body tube and fins, wet sanded to 4000 grit. I don't know why I did that, co sitering tge chances of recovery. I want to recover, of course, but to quote Tom Lehrer('s friend), "always predict the worst, and you'll be hailed as a prophet."
He cant find any other nose cone apart from a conical one.
 

TRFfan

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rockets

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The root tip of that fin looks like a little bit is chipped off. The airflow could exploit this weakness and tear the fin off so maybe you could consider making a new fin?
I see what you mean. Hmm, could I take a Dremel® and round the tip off? It's kinda too late becuase I have already filleted. BTW, pictures of that coming soon. :)
Thanks,
 

Incongruent

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Build up more material with epoxy or the filler of your choice and sand to fit of necessary.
 

TRFfan

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Good Idea, I'll try it! Now I'm not as worried! :blush:
Thanks,
Yeah thats a good idea. But make sure to seal the leading edge of that fin with epoxy to prevent delamination.
 

rockets

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Oh, boy I think I'm going to need some HELP!
IMG_2677.jpgIMG_2678.jpg
The first two fins were good, but the last fin didn't go over too well. I redid the simulation on RockSim with the canted fin. It still was stable. But, I want a second opinion. What are your guys ideas??
Thanks,
 

cavecentral

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The lean right concerns me less that the front to back is not straight (2nd picture). Going to spin if the fins are twisted! Doubting mach flights and twisted fins are a good combo.
 

chris m

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What I would do is redo your fins and use a fin guide to make sure there straight . Small and fast
 

dixontj93060

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What a hack build.

Before you start anything that is minimum diameter, high-velocity, do some reading/studying.

Jeezus!
 

Incongruent

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What a hack build.

Before you start anything that is minimum diameter, high-velocity, do some reading/studying.

Jeezus!
How do you know it's going to fly minimum diameter and high velocity? Haven't you heard the terms: "You can always adapt down" and "confetti doesn't fly fast"? (Okay, I made the second one up.)

And rockets, I have picked up a lot of shoddy advice over the years... well, months. Anyways, you can ask me so you have a scapegoat when things fail. Just no lawsuits please!
 

dixontj93060

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How do you know it's going to fly minimum diameter and high velocity? Haven't you heard the terms: "You can always adapt down" and "confetti doesn't fly fast"? (Okay, I made the second one up.)

And rockets, I have picked up a lot of shoddy advice over the years... well, months. Anyways, you can ask me so you have a scapegoat when things fail. Just no lawsuits please!
Uh, duh, title of the thread, MD=minimum diameter.

Flour as fight tracking?? Jeez, please do some research.
 

dhbarr

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h195 in naked MMT is maybe not a great plan?
 

OverTheTop

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There is a useful discussion here on fin alignment:
http://forum.ausrocketry.com/viewtopic.php?t=3510

You can cut a pair of in alignment guides out of some corrugated cardboard using a steel rule and craft knife. Mark it out with a protractor (use trignometry for bonus points and more accuracy!) and a sharp pencil carefully, and watch your fingers!
I used the same technique for my 8.25" Nike Smoke (works for small rockets too :) ).
121.jpg

I have also used alignment by eye, assisted with two set-squares on the bench which works quite well. I will try to find a pic...
 
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rockets

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I ran a simulation on RockSim last night. I put it at a very canted fin. It was still stable, it lost maybe 200 ft off the simulation, and lost about like 50 MPH. So near the same. It's too late to rip off the fins due to the 30 min. epoxy. :(
Thanks,
 

TangoJuliet

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If I were you, I think I'd start over and pay a little more attention to my craftsmanship; especially if I were going to put some kind of High Power motor in it.
 

chris m

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That rocket will not get rso'ed . Not to be mean but MD rocket and a bigger motors is no place to test . And your a teen and your mentor will be on the flight . I would not even let it go to rso table .
 

rocketgeek101

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If I were you, I think I'd start over and pay a little more attention to my craftsmanship; especially if I were going to put some kind of High Power motor in it.
+1. Call it an opportunity to learn for your mistakes and do better next time. Fortunately you're using cheap materials, so the cost to rebuild will be minimal (and take the time and effort to cut and shape your fins properly). Here is a useful list of tools including one to make a fin alignment guide you can print out for free.
 
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