Making spiral-wound paper tubing

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prfesser

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Usually it's easiest to buy the tubing you need, but sometimes it just isn't available. For example, a particular size for a scale model. Telescoping casting/liner tubes. A long coupler that slides over, not inside, another tube. And so on.

Convolute paper tubing---the kind used for BP motors---looks simple to make, but when it comes to model rocketry the devil is in the details. Wrinkle-free tubing of precise dimensions can be a challenge and takes a fair bit of practice. (I still have trouble with it.)

By contrast, spiral-wound tubing may appear to be challenging but it can be quicker to master than convolute winding, especially for long tubes. Industrially it’s made on a machine that winds all of the layers of paper simultaneously and continuously. Tubes are cut from the mandrel as they reach the proper length. This process is much faster and less expensive than convolute winding, and has virtually no limit to tube length.

But we don't need a machine for just a few tubes. We can duplicate, by hand, what the machine does. It will be slower…but after all, what is a hobby but a way to waste time? :)


Materials

Papertube001.jpg

  • A mandrel with o.d. the same as (or very slightly smaller than) the tube i.d. Metal, PVC, wooden dowel, almost anything that is round, very smooth, and rigid. It must be at least a few inches longer than the longest tube to be made. Here I'm making an adapter to fit 22mm research motors in 24mm motor mounts, so the mandrel is 7/8" o.d aluminum tubing. File or sand off any burrs on the ends.
  • Gummed paper tape, water activated. Not fiberglass-reinforced tape unless you prefer lumpy tubes. A convenient tape width is about half again the diameter of the tube. Tape thickness is roughly the “pound” rating with the decimal moved four places to the left. The roll shown here is 1½" wide and rated as "50 lb" so about 0.005" thick (it's actually a bit thicker). Thin tape, 40 lb or thinner, tends to wrinkle and tangle once wetted. I prefer 70 or even 90 lb tape if available.
  • Wax paper or other release paper. I like thin silicone paper backing from Con-Tac or from self-stick floor tiles.
  • Scotch tape, scissors and a sharp hobby knife or box cutter.
  • Foam paintbrush and a cup of warm water.
  • Talcum powder. Real talc is still available as a cheap filler for epoxy. Cornstarch might work but I haven't tried it. I don't know how sticky damp cornstarch would be.
Procedure for PAPER TUBES OF SCIENCE! (apologies to Bill Nye)

1. Decide on the length and wall thickness of the tube. This will be a 12" tube with 0.04" wall, so about eight layers of 0.005" tape.

2. Approximate strip length. You can calculate it: 0.875" x 12" x pi = 32.97 sq. in., divide this by 1.5" tape width to get 22" long strips. What I do is to simply spiral the tape around the mandrel to give the approximate length. It’s a good idea to cut the strips a bit longer so the rough ends can be removed. For this tube I’ve cut seven strips. I also cut the ends at roughly the angle needed to give a square end; about 45° will do.

Papertube006.jpg
An eighth strip is cut to the same length as the others, but is a mirror image of them. That is, the cut angle will be in the opposite direction of the angles cut on the other strips. This is the starter strip, #1, and will be wrapped gummed-side OUT. The image shows one of the regular strips and Strip #1 side by side; both are gummed-side up. (From here on I'll just say Strip #1 or just #1, instead of the word 'tape'.)
Papertube002.jpg

3. Two pieces of scotch tape, long enough to go around the mandrel plus a little more, are cut. A piece of release paper is cut a few inches longer than the finished tube, wide enough to go around the mandrel a little more than once. Or twice, if it's thin release paper. Experiment.

4. The release paper is wrapped tightly and smoothly around the mandrel (silicone side OUT). Scotch tape sticks to itself much better than it sticks to release paper, so the tape is wound around each end such that the ends overlap. If possible the tape should be positioned so that it adheres to the mandrel as well, as seen here.

Papertube003.jpg
If you have trouble getting the release tight on the mandrel before taping, lay it on a large flat surface and roll (not back-and-forth) with the palms of the hands while pressing down on paper+mandrel. If the paper loosens you may be rolling the wrong direction! For very long tubes it may be easier to cut long strips of wax paper and spiral-wind them around the mandrel. Leave about 1/16” gap between the edges of the waxed paper. Do not allow the edges to overlap as that will leave a ridge. Two layers of wax paper strips are recommended in this case, with the second layer covering the edges of the first. This will prevent the gummed adhesive from leaking onto the mandrel, which could make it impossible to remove the finished tube.

5. Cut two more pieces of scotch tape long enough to go around the mandrel. Now spiral Strip #1 around the mandrel, gummed side OUT, covering the release tightly and smoothly. Leave about a 1/16” gap between the edges. Tape each end of Strip #1 to itself and to the release, and to the mandrel if possible.


Papertube005.jpg
6. Now comes the tricky part. Wind Strip #2, dry and gummed side IN, a little more than one turn around the mandrel. (These images were re-shot with blue tape for #2, for clarity.) The center of #2 should be over, or close to, the seam of #1. Again, leave about 1/16” between the edges of #2.

Tube01.jpg
7. With one hand, hold #2 in place a few inches back from the end of the tape, allowing the end to come free. Don't let #2 slip out of position! Brush water on the exposed gummed surface. It should be wet enough to activate the gum of both strips.

Tube02.jpg Tube03.jpg
Now with the other hand, wrap the wetted end of #2 back down onto #1 and smooth it down.

8. If this has been done correctly, #2 is now in the proper orientation, and the 1/16" gap should remain nearly constant as you wind. Wet about a foot of #2 at a time and smooth it down snugly over #1. I usually rotate the mandrel with the right hand and smooth the strip down with my left. Continue until you reach the end of #2. Have the scissors handy in case #2 needs to be trimmed shorter.

Sometimes the edges of the tape move together or apart a little as you wind. To fix this, apply a little more pressure, fingers against the mandrel, to one edge or the other of the strip as it is wound. Not enough pressure to tear the tape, but enough to slowly shift it back to where it’s supposed to be. Again, avoid the tape overlapping itself as that will leave a ridge.

9. Repeat Steps 6-8 for the remaining strips. Less wetting will be needed since only one surface has adhesive.

The tube will shrink a bit as it dries. I stopped this tube with Strip #7 to ensure that it would fit into a 24 mm MMT. If it shrinks too much on drying, another strip can be added later. Trim the ends, primer or filler, sand lightly w/fine grit.

When making tubes more than 2-3 feet long there’s a tendency for the seam to “drift” a bit. That is, you might start with the middle of a new strip over the previous seam, but by the time you get to the end, the new seam is on top of the old one. That’s just a consequence of the uneven pressure of human hands. Probably better to make shorter tubes and couple them together, if that works for you. Still, I’ve made 1” tubes five feet long after some practice.

10. The scotch tape is removed while the tube is still damp—you’ll probably tear the ends a bit in doing so, but that's ok, it's why you make it oversize—and the tube is gently slid off the mandrel. The release paper is removed from inside the tube by pushing a dowel down the tube. The mandrel is rubbed with a little talcum powder and the tube is slid back on the mandrel. This helps it keep its shape and diameter as it dries and shrinks.

The tube should be finished as you would papered fins.

A mandrel that is a bit undersized can be built up somewhat, if you expect to need more than a few tubes. Wet and wrap the undersized mandrel with gummed tape as was done for the tube. Each wrap of 50 lb tape will increase the OD of the mandrel by about 0.01”. After enough layers have been applied the assembly is allowed to dry thoroughly and the grooves are filled, sanded, and sealed as though you’re finishing a rocket. I've made several such mandrels from galvanized EMT wrapped and sealed with tape. The one below was the right size for casting tubes for 29 mm motors.

1679406981862.jpeg
 
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I roll lots of casting tubes, liners, and even body tubes ranging from 3.8" to 1-13/16 ID. I use 3" (now 72 mm) wide unreinforced paper tape. The pic is the mandrels I have for the various size tubes. For under 18 mm, I use 1/4 wide strips, 24 and 29 mm 1/2 wide and larger, full width. Don't over-engineer. Tape is cheap, around $7 for a 600' roll. Make the strips plenty long and don't worry about the ends. Make the first layer strips about 2 width longer than the rest. Wrap the first layer dry with the glue out. Following layers are wetted and glue in. It will take some practice to get smooth, consistent tubes.

Mandrels.jpg
 
I've made paper tubes like that in the past. They came out very nicely and were very straight (thanks to a perfect phenolic mandrel). And when I tried to glue on fins using water-based wood glue (apparently) the tube started to seriously go out of round and by the time my daughter had painted it with water-based paint, it was ready for the bin.
Just my experience, might be different for different types of tape - or just don't use any water-based products on them.

Oliver
 
For the 18 and 24 mm body tubes and couplers the same dimensions as the motor case and used a fin can over the motor (or glued the fins to the motor). For rule cops use the fin can. (Where is the *duck* smiley. NOT the bird :mad: .)
 
I use a similar technique. Once release paper is down. But, I do 2 layers gum out, 1 layer gum in the opposite spiral direction, 3 layers gum in back to the original direction. This makes it stronger for the same number of wraps, but slightly rougher finish. This is all done tight and dry and start-stop ends well taped with sellotape. Once all layers are down and tight spray the whole assembly well with water and wrap the whole mandrel with cling film. This gives some compression while it sets. Leave overnight, remove cling film, respray rewrap in cling film. Next day unwrap trim ends, remove from the mandrel, remove the release paper from inside, put back on the mandrel to dry. I usually allow a week.
 
Here's a 6 1/2-inch tube I made earlier..... This allowed me to get the weight down to 1200gm loaded and ready to fly. This is bigger than a Minie Maag which would normally come in at just over 1500gm. So into the HPR weight limits whereas making your own tube you can get to launch in the lower category. Flies OK too....

Mullaley_010423_GK_31.jpgMullaley_010423_GK_05.jpg
 
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Made a triangular lobed 6-layer cardboard tube. Ironed it with a hot iron while still damp. That removed almost all imperfections. We'll see if I can get it off the printed mandrel tomorrow. YMMV.
Across the lobe to the apex is about 90mm ish. That's the nosecone beside it. 400mm long.....
IMG_20230413_162721.jpg
 
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Hey, @prfesser, any recommended sources for the tape? I'm looking to do a 1.5-inch tube. Amazon is a zoo of chinese garbage and the prices seem really high. Could buy a case from Uline and probably be happy with it, but I don't need a case.
I used to get it from Mcmaster but they stopped carrying the 3" (now 72 mm) that I use. I use it for casting tubes but a roll lasts about a year unless I make a lot of 54 mm.
 
I made a tube winder out of an okidata dot-matrix printer years ago; printers in the 80's weren't great at reliability, and test mode on the printer can be invoked by holding the paper feed button while turning it on.
It will roll continuously; there's another mode, that makes it print it's character set; wrapping a sheet of paper around the platen let it print over each other, showing kerning problems.
Makes a great inexpensive tube roller. Check your older printer, it may be similar.
 
I've had spiral wound tubes "unwind" by twisting in the opposite direction of the original spiral wrap. Of course, that shouldn't happen if all the glue is properly moistened and the wraps are tight, and so on; but sometimes it happens.

I've wondered, therefore, about alternating the winding direction from layer to layer. When one layer is trying to unwind, the one's around it are trying to wind tighter, and that would keep either thing from happening, making for a stronger tube than you get when all the wrapping is done in the same direction.

That's the idea, what I wonder about. Have any of you done that? It would be inconvenient at best to do on industrial machinery, but really no extra effort at all by the method here.
 
I've had spiral wound tubes "unwind" by twisting in the opposite direction of the original spiral wrap. Of course, that shouldn't happen if all the glue is properly moistened and the wraps are tight, and so on; but sometimes it happens.

I've wondered, therefore, about alternating the winding direction from layer to layer. When one layer is trying to unwind, the one's around it are trying to wind tighter, and that would keep either thing from happening, making for a stronger tube than you get when all the wrapping is done in the same direction.

That's the idea, what I wonder about. Have any of you done that? It would be inconvenient at best to do on industrial machinery, but really no extra effort at all by the method here.
Norman mentions it above. I also do one layer wound the other way - but it's layer 3 (of 5) for me.

And i use this: https://www.uline.com/Product/Detai...Non-Reinforced-Kraft-Paper-Tape-2-x-600-White
 
I've had spiral wound tubes "unwind" by twisting in the opposite direction of the original spiral wrap. Of course, that shouldn't happen if all the glue is properly moistened and the wraps are tight, and so on; but sometimes it happens.

I've wondered, therefore, about alternating the winding direction from layer to layer. When one layer is trying to unwind, the one's around it are trying to wind tighter, and that would keep either thing from happening, making for a stronger tube than you get when all the wrapping is done in the same direction.

That's the idea, what I wonder about. Have any of you done that? It would be inconvenient at best to do on industrial machinery, but really no extra effort at all by the method here.
Opposite spiral direction greatly increases strength for a sacrifice in surface finish.
Depending on the diameter, I'm using 6-8 layers 29mm ID is 6. 161mmID is 8 layers. in a 2 layer each way
If it's coming undone, you're probably not getting enough compression on the tube while it's drying. I get a roll of cling film and cut it in half so I've now got 2 rolls 5-6" wide. once the tape is fully applied, spray the tape until it's soaked and wrap the clingfilm around the outside under good tension. If the clingfilm breaks, just restart where you are. You can remove the cling film after about an hour. This works OK up to about 6 layers.
Alternatively, once you're happy handling the tube and wrapping as you go, you can put 2 layers down glue up, then 1 -2 layers opposite spiral and spray, get a warmish iron and iron out the tube a bit at a time till it's smooth, add another 2 layers and repeat.
The tape I'm using is Venhart 60 mm wide. Don't use the reinforced tape. It's strong as a single layer, but lumpy as heck layered. Doesn't work.
The result will be a strong usable tube, but it's not going to have the same finish as a bought one. Of course, I can't buy one, so that's why I'm doing it.
 
Here's a 6 1/2-inch tube I made earlier..... This allowed me to get the weight down to 1200gm loaded and ready to fly. This is bigger than a Minie Maag which would normally come in at just over 1500gm. So into the HPR weight limits whereas making your own tube you can get to launch in the lower category. Flies OK too....
Here's George from Air Command Rocketry inspecting my work.....
1705341975102.jpeg
 
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