Stiff Mailing Tubes for a new build - don't know what I want

Off Grid Gecko

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So I've had these mailing tubes in the rafters of my house for a while. about 36 and 38 inches long after "trimming."

I have a shorter one that is thinner and matches the dimensions for a FG nosecone pretty well. All 3" ID.

Did a little cutting and sanding today while I was supposed to be writing blockchain software. Thinking now that my L2 is done I want to make a 3" rocket. At first I was thinking min-diameter build because the cardboard is thick enough I think I can get a good solid fin mount in there if I cut slots and tiny tabs on the fins, but I've been sticking with Cesaroni hardware and I can't think of an easy way to make an extendable motor mount for different size cases without tapping the forward closure and I'm not sure what the rules are on that. I've only used Pro38 so I don't even know if the closures are steel, I assume they are aluminum and it just seems like a bad idea to tap threads in that, correct me if I'm wrong.

Now I'm thinking maybe a 54mm motor mount.

I think I can use the thin-wall piece to hold the nose cone and use some wood putty to smooth the transition for OD. Basically a 3" coupler with a piece of thin stuff long enough to hold the nose cone followed by a band of the thicker cardboard and then blend that edge.

The big tubes are quite stiff and I'm sure will hold up find to pretty strong boost. Little heavy, maybe 5oz per foot. I want to push the Mach barrier with it and my luan fin stock prolly a little wormy so I might order some birch aircraft plywood and up it to 3/8". I worked up a basic 4FNC design on openrocket.

I guess.. You ever get stuck and just want to build something to burn up the materials? I have another motor coming for my L2 rocket, just an I. May order some more motors for that one too. I don't have/want a huge fleet but these tubes have been laying around for over a year and just begging to be turned into a rocket so I thought it would be cool to have a speed demon around that if I go to a bigger field I can open it up with a GPS tracker and see what she can do.

It'll be a payloader too so maybe some fun ideas for experiments that will fit in a 3" tube?

Anyway, any real pitfalls I should look out for building a mach-capable rocket with cardboard and plywood? I don't plan on glassing the tube. Like I said it's very strong stuff. Any ideas for a skinny scale missle that might fit the bill? Final OAL will likely be over 6 feet.
 

teepot

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I have some 3" mailing tubes too. I only built a couple of rockets with them. They are thick walled. A 3" nose cone fits perfectly. The down side is that they tweak easily. A moderate landing speed caused a wrinkle in the tube. Your tubes might be more durable. I only flew one of the mailing tube rockets once. The other is yet to fly. Oh, and they are heavy. It was time consuming to get a half way decent finish. Mine have a fairly rough finish. I got them from Amazon.
 

Off Grid Gecko

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I have some 3" mailing tubes too. I only built a couple of rockets with them. They are thick walled. A 3" nose cone fits perfectly. The down side is that they tweak easily. A moderate landing speed caused a wrinkle in the tube. Your tubes might be more durable. I only flew one of the mailing tube rockets once. The other is yet to fly. Oh, and they are heavy. It was time consuming to get a half way decent finish. Mine have a fairly rough finish. I got them from Amazon.
The ID on these guys seems good for a 3" nc but there will def be a lip that I'll have to smooth out one way or the other. The tubes were used at the factory and some steel components were shipped in them (or perhaps brass). They are definitely quite rough on the outside so getting a smooth coat of paint is going to be a trick, but when it comes to that I'm kind of a glutton for punishment.

I have a sketch on OpenRocket and an order sheet for materials. It looks like I can share shock cords and chutes with my L2 rocket. Even with a 54mm mount it's pushing my flying field waiver limit on full power. I'll probably save the minimum diameter idea for a fiberglass rocket or something small to get a feel for motor mounts and rail guides. I'm assuming for min-diameter the guides would have to be surface attach. Prolly not the best idea on cardboard for a HPR.

Price just adds up so fast, I'm looking at close to $200 without motor hardware for 54mm tubing. Or fin material. lol. I guess I could backburner this idea or maybe just start cutting bulkheads and stuff from my current stock, make some couplers, then see where I end up. A lot of the money is on small stuff and a retaining ring.
 

teepot

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The ID on these guys seems good for a 3" nc but there will def be a lip that I'll have to smooth out one way or the other. The tubes were used at the factory and some steel components were shipped in them (or perhaps brass). They are definitely quite rough on the outside so getting a smooth coat of paint is going to be a trick, but when it comes to that I'm kind of a glutton for punishment.

I have a sketch on OpenRocket and an order sheet for materials. It looks like I can share shock cords and chutes with my L2 rocket. Even with a 54mm mount it's pushing my flying field waiver limit on full power. I'll probably save the minimum diameter idea for a fiberglass rocket or something small to get a feel for motor mounts and rail guides. I'm assuming for min-diameter the guides would have to be surface attach. Prolly not the best idea on cardboard for a HPR.

Price just adds up so fast, I'm looking at close to $200 without motor hardware for 54mm tubing. Or fin material. lol. I guess I could backburner this idea or maybe just start cutting bulkheads and stuff from my current stock, make some couplers, then see where I end up. A lot of the money is on small stuff and a retaining ring.
There are fly away rail guides from several vendors. That's what I'm using on my MD's.
 

dhbarr

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Big Daddy nosecone & body, some scrap plywood, and a bt60 body tube w/ some couplers to hold 38mm motors... Presto, it's an L2 tubefin!
 
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SolarYellow

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Price just adds up so fast, I'm looking at close to $200 without motor hardware for 54mm tubing. Or fin material. lol. I guess I could backburner this idea or maybe just start cutting bulkheads and stuff from my current stock, make some couplers, then see where I end up. A lot of the money is on small stuff and a retaining ring.
Check with the "Best Carbon" seller on AliExpress. Look at their offerings, then use one of the email addresses they include in their listings and talk to them about dialing in your order for non-listed sizes, wall thickness, etc. Remarkably affordable. They also have the c.f. plate for fins, etc.
 

Off Grid Gecko

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There are fly away rail guides from several vendors. That's what I'm using on my MD's.
This did actually occur to me, I've seen the ones from apogee but haven't actually used them myself. The more I thought about it, the more I think I need to invest in tracking before tackling that arena. So I'm gonna go ahead with the 2" motor in a 3" airframe. Still giving me some cool results on the sim and within the waiver at most fields. My current flying field I'll have to keep it tuned down to an I or baby J, but maybe if I visit a different site I can run it full K.
 

Off Grid Gecko

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Screenshot from 2022-09-22 08-51-39.png

Think I'll be going with this setup for now. When I checked the chutes they worked out the same as my L2, so I can just unhook the links and put them on this birdie. Other than the motor-mount centering rings, if I cut the rest of the stock bulkheads and stuff out of luan that I have already, the cost drops to like $100, and I think I have $80 worth of store credit at apogee, not sure if I want to dip into that just yet though, haha. Saving that for a FG order I think.

If the bays look funny that's the nature of the build. I need to couple my smaller cardboard up front to hold the nosecone as it will have a much closer OD, then where it's coupled to the "beefy" tube I can do a minimal transition, just try my best to make it smooth. The Ebay should be about 12" long so plenty of room for backups and I'm going to build out the forward nosecone area as a payload bay. Maybe for testing new electronics before I fly them on another bird or if I can come up with some neat experiments to do.

EDIT: will be making my own couplers as well. I have plenty of tubing and they seem to work just fine for this larger tubing.
 
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Off Grid Gecko

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Ordered some parts. Going with a plastic nose cone after all, 12.5in Ogive. I think I'm going to try sanding the thicker tubing to meet up with the nose cone, though not sure exactly how just yet. if that fails I'll insert an upper coupler and slide on a piece of the thinner stuff to mate with the NC.

I've run the simulation over and over again and confident that my 18" and 48" chutes from my L2 will work just fine for recovery. Got a length of LOC 54mm tubing for the MMT, rail buttons, 4 centering rings for the mmt, and a 54mm aeropack motor retainer.


I cut my tubing to length, 36" fin can/MM, 5" E-Bay band, 15" main chute bay. Will figure out the payload for the nosecone wen it arrives. I made an 11" coupler tube for the electronics bay so 3" will stick out on the top and bottom. Glue has been drying on it for a couple hours and I'm getting ready to secure the band on it. Still a little sick so I'm not going to break out the power tools to cut the bulkheads yet.

I will have to cut the MMT to length so perhaps the extra piece will work for a payload bay in the nose cone. If I cut it full length for 6xl cesaroni casing I'll only have about 8 inches left over, but I can prolly short the casing a little bit.

Never thought to ask before but is it critical that there's MMT around the entire length of motor? Okay if some of the motor is sticking out the top? Honestly I see no need to use a 6xl but never know, I might win the lottery and get froggy. Starting off I'll prolly just be using 2G and 3G motors, limit for tripolimokan field is probably 4G at our current flying field.
 

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