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Concrete Form Tube Mid-Power?

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joshismycaptain

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Hello Everyone!

I was on this forum long ago when I lived in Arizona. I was a member of the SSS and launched several times in Rainbow Valley. I have since moved back to Minnesota (my home state). After a few years of rocketryless living, I've decided I miss it and want to get back in. I retained my LOC Forte, Weasel, Leviathan, 29mm Executioner and a few other 29mm models which have been hanging in my garage. I'm hoping to join Tripoli MN, especially since they launch in North Branch and I live in Chisago. I also just bought a cabin on Mille Lacs Lake and am hoping to launch up there in the Winter on the lake!!!

Glad to be back to rocketry!

Ok, I'll get to the point now : I just bought a bunch of low powered parts for my kids to tinker with, along with an Estes Argent kit. I also bought a 38mm motor mount. I've always wanted to build a "large" mid powered rocket. I bought some 8" concrete form tubes and some lightweight plywood. Can you see where I'm going with this? Is it reasonable to assume I could launch an 8" form tube with a mid-powered motor? I realize there are NUMEROUS variables. I'm moreso asking, can it be done? Has it been done? Is it difficult? I'm trying to calculate my level of ignorance before I start building...

Now,,,, I'm planning to make it 38mm so that I can use high power at some point, although I don't have my L1 cert yet. Hoping to do it next summer with my Forte. I'm probably going to build this thing whether I ever fly it or not.

I'm sure there is exactly one million opinions on this post,,, and I'm not looking for negative Nellies. I'm looking for someone who can reply with useful information that lacks sarcasm. Well, maybe a little is OK...

How do I fly an 8" concrete form tube on Mid-Power??????

Josh
 

joshismycaptain

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How about a large scale Big Daddy? I've always loved that rocket! Something shorter, lightweight, with large fins. Thoughts?
 

ttabbal

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Concrete forms tend to be a lot heavier than the normal stuff we build with for LPR/MPR. That's more likely your limiting factor. Weigh it and see where you're at. Then compare to the max lift-off weight for some motors you might want to use. If you keep the build light, you can probably fly a smallish rocket on a "G" motor, but without the weight it's all guesswork.
 

dhbarr

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Hello Everyone!

I was on this forum long ago when I lived in Arizona. I was a member of the SSS and launched several times in Rainbow Valley. I have since moved back to Minnesota (my home state). After a few years of rocketryless living, I've decided I miss it and want to get back in. I retained my LOC Forte, Weasel, Leviathan, 29mm Executioner and a few other 29mm models which have been hanging in my garage. I'm hoping to join Tripoli MN, especially since they launch in North Branch and I live in Chisago. I also just bought a cabin on Mille Lacs Lake and am hoping to launch up there in the Winter on the lake!!!

Glad to be back to rocketry!

Ok, I'll get to the point now : I just bought a bunch of low powered parts for my kids to tinker with, along with an Estes Argent kit. I also bought a 38mm motor mount. I've always wanted to build a "large" mid powered rocket. I bought some 8" concrete form tubes and some lightweight plywood. Can you see where I'm going with this? Is it reasonable to assume I could launch an 8" form tube with a mid-powered motor? I realize there are NUMEROUS variables. I'm moreso asking, can it be done? Has it been done? Is it difficult? I'm trying to calculate my level of ignorance before I start building...

Now,,,, I'm planning to make it 38mm so that I can use high power at some point, although I don't have my L1 cert yet. Hoping to do it next summer with my Forte. I'm probably going to build this thing whether I ever fly it or not.

I'm sure there is exactly one million opinions on this post,,, and I'm not looking for negative Nellies. I'm looking for someone who can reply with useful information that lacks sarcasm. Well, maybe a little is OK...

How do I fly an 8" concrete form tube on Mid-Power??????

Josh
2x AT g76's in a pair of 29/40-120 cases. No hazmat fee, no cert required, among the highest initial thrust peaks available w/out a cert. Take care to have a solid ignition system and lightly use an emery board on the top grain slot.

If you're married to 38mm, check out the three no-haz no-cert loads Loki offers in their 38-120 case.
 

rharshberger

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Concrete forms tend to be a lot heavier than the normal stuff we build with for LPR/MPR. That's more likely your limiting factor. Weigh it and see where you're at. Then compare to the max lift-off weight for some motors you might want to use. If you keep the build light, you can probably fly a smallish rocket on a "G" motor, but without the weight it's all guesswork.
Also keep in mind that you will have to make a custom nose cone for a sonotube as they are not rocketry standardized. Sonotube and mailing tubes are quite a bit heavier than standard airframe materials as has been mentioned. Flying a 4lb rocket on a G motor is doable (I have done it a dozen times with mixed results) any bonus delay means a crashed rocket since the time for the motors delay is just enough to deploy the chute just before it hits the ground. I now only use electronics in heavy G powered rockets for reliable deployments.
I would recommend ditching the solid ply and using basswood cores with a 1/64" ply skin over that, the same could be done for the centering rings.
 

Bat-mite

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Never considered this for mid-power. Tom Cohen, of MDRA and METRA, builds HPR rockets out of concrete form tubes. He glasses them and cuts his own fins and CRs out of plywood. Builds his own nose cones out of plywood and other sources. Rockets come in at about 150#, and he flies them (usually) on M3700 motors to about 1000'.
 

Zeus-cat

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Go find OpenRocket. It is a free rocket simulation software package. You can design your rocket and then test it with various motors without ever going near a launch pad. If you need help you will get tons of free advice here. Sonotube may not be one of the elements included in OpenRocket, but I'm sure you can add it.
 

Cabernut

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Lake Mille Lacs! I love it. A winter launch there would be great! I too am from Minnesota and am planning moving back. I'll probably join TripoliMN & MASA when I get there as well.

Start with OR, see what you can get for a ballpark figure. However it may be tough to keep under the 1500g(53oz) weight limit for MPR as well. I would estimate an 8" ID Sonotube would be in the range of about 43g(1.5oz)/inch, if the wall thickness is 1/8" and the density is the same as your average thick-walled tubing at 0.83g/cm3.

It would have to be a short stubby design, which just reminded me, someone in our club(CRC) built a Dalek that flies on a G. It's about a foot wide and very draggy, but it flies(sorta). Tinker around with ideas, you might be able to find something that works.
 

Handeman

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It is probably very obvious, but your issues are weight and drag. Weight from the tube and drag from the 8" diameter.

You can reduce weight, maybe, by shortening the length of the 8" tube. A nose cone and a tail cone with only a 3" or 4" body. That will reduce the weight and the drag.

I guess that probably isn't what you wanted. My suggestion would be to fore go the cost of the concrete tube and buy a short 5.5" LOC tube, 38mm MMT, and nose cone. Some 1/4" ply at the box store or a hobby store like Micheal's You could then make your CRs and fins from the 1/4" ply. Sounds very much like a Mini Mag kit.

Or, test your skills, time, and patience with the concrete tube. Pick which ever one you thing will be the most fun. That's what this hobby is all about and all the opinions and advice we give isn't going to change what you think is going to be the most fun to build.

Good luck, do a build thread, and LOTs of pictures!!!!
 

dhbarr

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Negative Nellie here! Sonotube rockets are cheap, but are quite heavy. For really big and light you have to think outside the box. Check out the techniques for foam construction used by burkefj, who has some amazing large rockets that fly on small engines.

http://www.rocketryforum.com/showth...ght-Large-Pershing-1A&highlight=foam+pershing
8" Sonotube is 1.1lb/12in, or about 1.47oz/in. That's certainly not featherweight, but well inside the realm of possibility.
 

rstaff3

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It may be doable but I don't think that's the best route for your first build. 1.1 lb/ft will add up fast, as will large rings, fins and a big cone. I'd also suggest getting some more experience before clustering G motors.

That being said, my L2 rocket used an 8" Sonotube. It started life before I got my L1 and I was thinking about flying it on three G80s. Luckily, I had planned for a host mount so it could fly on 38mm motors. It grew past the three G80s FAST.

I have built a few 8" rockets mostly out of posterboard and foamboard. The first one just sneaked in under 3.3lb and flew on a G80-4s. All flew nicely on baby H's.

But, if you want to give it a try, go for it. If it gets too heavy, build another rocket, get the L1 and fly the sonotube rocket on CTI 29's.
 

joshismycaptain

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Awesome info! Thanks! I don't have zero experience, but will admit it's low. I'm definitely I interested in finding a mentor in the Minnesota club and doing things properly for my L1 and beyond. I think the form tube idea is nothing other than my ambition getting ahead of me. It's probably not where I should be placing my efforts, or at least I should be expecting to launch it on a L1 after I have my cert. Rather then experiment with mid-powered maybes, I should focus on something more realistic. And,,, I'm probably still going to build this thing, even if it never flies. Goodness,,,, I can use the garage decor! But yes,,, you all offer very valuable insight and I appreciate the information. I will think about it some more. And if I build it,,, whatever it is, I will be sure to have photos...

Josh
 

grandcross

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Having used sonotubes only as a mandrel for a fiberglass tube, I still have some useful input here. First off, as mentioned, they're heavy. Factor in centering rings and other custom made parts and your total rises fast. Secondly, they're notoriously not round. That affects your centering rings and all parts that might attach such as through the wall fins. I've had some luck sanding things down to make the tube thinner and rounder, but I haven't actually used that as a body tube. You may have to glass or coat the tube if you try that, and that means adding weight too.

As a smaller HPR I'd say go for it, but you may not find it suitable for MPR.
 

GregGleason

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Why 8" for the OD? Other than the "bigness factor", why did you settle on that size?

I know sonotubes are basically round and cheap, but I wonder if that is the best solution for your project.

If there is no compelling reason for the 8" size, you can use a 4" airframe and have a lot less headaches in the process.

But if you want something larger than 4" OD, here are some options:

https://www.apogeerockets.com/Building_Supplies/Body_Tubes/5in_and_larger_Tubes

This project, while doable, requires at least moderate (perhaps experienced) build skills. If you have great skills and experience in doing one-off projects then you should be able to do this.

The more "off the shelf" items you use for your project, the more expensive the rocket (but require only minimal build skills). The converse is true for a rocket with few "off the shelf" items, where you can have a potentially less expensive rocket but at the cost of time, fabrication, and the requirement for greater build skills.

Greg
 

joshismycaptain

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Why 8" for the OD? Other than the "bigness factor", why did you settle on that size?

I know sonotubes are basically round and cheap, but I wonder if that is the best solution for your project.

If there is no compelling reason for the 8" size, you can use a 4" airframe and have a lot less headaches in the process.

But if you want something larger than 4" OD, here are some options:

https://www.apogeerockets.com/Building_Supplies/Body_Tubes/5in_and_larger_Tubes

This project, while doable, requires at least moderate (perhaps experienced) build skills. If you have great skills and experience in doing one-off projects then you should be able to do this.

The more "off the shelf" items you use for your project, the more expensive the rocket (but require only minimal build skills). The converse is true for a rocket with few "off the shelf" items, where you can have a potentially less expensive rocket but at the cost of time, fabrication, and the requirement for greater build skills.

Greg
Yeah,,, I just want to own and fly larger rockets without the complexity and cost of high power. Obviously it's a limited idea. I mean,,,, the reason high powered rockets are high powered is because they were too big for mid power motors in the first place, right? :D

Keep in mind too, this form tube idea is not "my project", it's simply "an idea". I'm currently building an Estes Argent very meticulously with 38mm mount and planning to glass and pay very close attention to detail. That's my baby right now. This form tube thing is just a "hey, what crazy unrealistic stuff can I be doing in between steps on my very deliberate and carefully executed Argent."

Honestly, I'm not on a mission to launch a form tube on MP. It was just kind of a what if and I happen to buy a tube and some plywood. I'm leaning towards the fact that it's probably not worth my time unless I want to slap it together for a static display in my garage or at a launch...

::shrugs::

Josh
 

rstaff3

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I personally would say it could be worth your time. Just plan to get advice as you go and set it aside for HPR if it grows to be too heavy. If you don't get around to HP, it can be displayed and you can apply what you learned to a future build.
 

joshismycaptain

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I personally would say it could be worth your time. Just plan to get advice as you go and set it aside for HPR if it grows to be too heavy. If you don't get around to HP, it can be displayed and you can apply what you learned to a future build.
I like that. Yes. I'm very open to advice! So,,, let's say that I build it now with little to no knowledge of HPR. Is 38mm reasonable? And are there any other considerations I should take in effect if it were to one day be launched as HPR? Can I make it standard deployment? Is dual deploy something I should think about now? Obviously I'm ahead of myself. I'll be the first to admit I am not sure what I'm doing. I need a local mentor in the Twin Cities. Someone to stand in my garage, scratch their head with me and say, "no no no, you need to do it this way..."

Josh
 

rstaff3

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A face to face mentor is a great idea. I learned a lot on the field...but back then all we has the r.m.r Usnet group. It was tough to learn much there. A mentor can inspect what you are doing to make sure it all will hold together etc.

I'd go 38mm, single deploy for the first go around. There are plenty of 38mm options to get it as high as you want and you can also adapt down to 29mm. On my early concrete form tube, I added an altimeter bay between the upper CR and the point where the cone's shoulder stopped. Very high tech. The charge as armed by twisting wires together and shoving them back into the body. First flight was motor ejection only. L2 was altimeter with the motor as a backup.
 

joshismycaptain

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So,,,, build it how I know to build a single deploy rocket,but use 38mm, be weight conscious and try to build soundly. That's the plan...

Should I make it 4 foot or 8? :D
No, but seriously, I bought two form tubes.
Start with 8"x4'? Let's just plan on it being heavy and HPR. Whether I attempt a MP launch or not will be secondary...

Josh
 

rstaff3

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Sounds like fun to me. Nosecone...buy a slab of 2" pink styrofoam insulation. Cut circles, glue together, make a mess. Or, go fancy and make a hot wire cutter. Mine was turned by a HS shop class. They made the mess and the teacher made them clean it up. :D
 

dhbarr

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Two 24 holes, two 29 holes, two 38 holes, all arranged around a 54 hole?

It's not like you don't have the tailroom :)
 

rstaff3

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Two 24 holes, two 29 holes, two 38 holes, all arranged around a 54 hole?

It's not like you don't have the tailroom :)
I guess weight will be no problem in that case!
 

Nytrunner

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Trying to squeak it off the pad on G-power will take some amazingly efficient construction, But with this heavy a tube and some solid plywood fins, you could almost certainly get a level 1 and 2 certification with this thing. Semi-half-scale Patriot maybe:cool:?
 

joshismycaptain

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Two 24 holes, two 29 holes, two 38 holes, all arranged around a 54 hole?

It's not like you don't have the tailroom :)
Choose your own adventure! Love it!

I think I'll just put the 38 in it, attempt to launch on a MP once, and keep it around for a possible HP launch, but mainly comic relief... :D

Josh
 

rstaff3

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We'll all kinds of things are possible. I've seen an 11.5" N-powered rocket that was screwed together and heard of one that, presumably other than the laundry and electronics, that was scavenged from construction sites and glued together with liquid nails.
 

joshismycaptain

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We'll all kinds of things are possible. I've seen an 11.5" N-powered rocket that was screwed together and heard of one that, presumably other than the laundry and electronics, that was scavenged from construction sites and glued together with liquid nails.
Screwed and glued? :D
 

scsager

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Hello Everyone!

... although I don't have my L1 cert yet. ...

How do I fly an 8" concrete form tube on Mid-Power??????

Josh
You may already be aware that a rocket with a "lift-off-weight" of more than 1500 grams is considered "high-power" and requires the flyer to be HPR certified REGARDLESS of the size of the motor.

I'm doubtful you could lift an 8" tube with a single G80 motor. If you build a single motor tube, and without a cert, you are limited to just one G80 motor as the most powerful... You can fly a rocket with a "cluster" of TWO G80 motors to provide the maximum power. This is still allowable without certification.

Two G80's weigh about 260 grams, leaving you 1240 grams for the rocket and recovery gear. The questions now becomes... Can you build a rocket with an 8" concrete form tube that weighs no more than 1500 grams ready to fly???
:cool:

The attached pdf should help show where HPR cert is needed.
 

dhbarr

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Sure, we already established the weight per inch upstream. Assuming a blobbo-style cut-tube nosecone, a single flat thrust plate notched into three fins. Heck, now I want to build one, maybe twice as long as it is wide?
 
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