56 replies to this topic

[pyrotechnist]

Hi agian how much dextrin whould you normaly use for a standard tube? I am still wondering about this and just got myself some nice thick lining paper from B&Q 1000 grade. It has made a thick tube with not much of a long peace and i used PVA but it is not yet set so i will see how it goes.

[Phoenix]

Don't know how much dextrin to use... I'll get back to you when I've tried it.

I just tried tube rolling a la Weingart - that is as follows:

"After seeing a great many case rollers at work and employing, at different times, their various methods, the author has come to the conclusion that the following is not only the easiest, but the most efficient method. Take a small scrubbing brush of good quality with long, stiff hairs. Make the paste somewhat thicker than that used for candles. Lay a single sheet of paper on the rolling board... Now, with the scrubbing brush, rub some paste (not as much as for candles) evenly over the sheet and immediately roll up as tightly as possible... This leaves a case that is already half dry and, when completely so, should be firm enough so that it cannot be bent in on the ends with the fingers. The advantage of this method of rolling heavy cases is that there is no time for the paper, especially the straw or pulp board, to become softened and swoolen as is the case when a number of sheets are pasted down at once. A tighter, cleaner case, which is more easily and quickly dried, results. If too much paste is used, the water from the paste evaporates on drying, leaving the case spongy."

I used some very thick wallpaper paste (it would stay in the dish if you turned it upside down) and a nail brush. The results were exactly as Weingart promised: rolling was very quick and easy, and the cases are now rock solid and very dense - the layers of paper show no signs of having split apart as they dried, as is usually the case (NPI) when a thicker layer of paste is used. The stiffness of the bristles allows a thin film of glue to be applied to the surface of the paper, and a thicker glue to be used, so a denser, more strongly bonded case results.

[Jerronimo]

Well, I tried rolling tubes with dextrin.
I used 90grams kraftpaper and a very concentrated dextrin/water solution.
The trick is to first paste the whole strip of paper(like you would do with wallpaper)
so the solution impregnates it and the paper won't wrinkle.
After this procedure the paper rolls very easily, the produced tubes have been drying for 3 days and are already rockhard.

This is by far the best glue I ever used, no shrinkage whatsoever, rockhard tubes and cheap as chips!
And totally homemade

[karlfoxman]

Jerronimo:

tried your glue and its really good, great tip. made some gold tourbillon-report shell inserts and it set rock solid. thanks!

[paul]

Three questions about that:

Do you use hot tap water for making the glue?

And how much dextrine do you use per lets say 500ml of Water?! Is it simply a saturated dextrine solution?!

Thanks in advance,

paul

[rooster]

I always get air pockets after my tubes dry. I have used PVA glue/water, dextrin, and gum arabic. I found out that if you have a too thin mix(too much added water), the water will suck up a lot, making the tubes rock hard, but much harder to roll. They seem to always wrinkle or leave air gaps.

Anyone got any good tips?

I will try some different thicknesses of craft this weekend, different adhesives, and different rolling methods, and let you know the results. Maybe I'll even take pics.

[Jerronimo]

Yes Paul, I will try to explain.

The dextrin has a tendency to clump together when added to the water.
Simply put on a pan of water and heat it until it boils, then add the dextrin.
The dextrin will still start to clump, but because of the high temperature will desolve easier, let it simmer and stir occasionally untill no more lumps are present.
(god I feel like Dilia Smith )
Then let it boil down to a siruppy consistancy and turn of the heat, like this the glue can be stored for at least a week.
When needed, simply add hot water to the dextrin sirup and stir well, keep adding water until a ''watery'' consistancy is reached.
Now the glue is ready to be aplied as staded in my earlier post.

[paul]

Thanks alot to jerronimo. Yes, this explanation helps I?ll have to try that.

To roosters problem: Use thicker glue, it isn?t really harder to get good results with a bit practice.
Put the glue on with a wide and flat brush. Then roll up the paper immediately. So the paper hasn?t even the chance to suck up the water from the glue and so you will get a very smooth surface with no blubbles/gaps in it.

Edited by paul, 02 March 2005 - 06:36 PM.

[Phoenix]

I've always rolled all of my tubes myself, with the exception of mortars above 50mm, and have have found it very difficult to roll them without any air pockets. The closest I've come to completely solid tubes is with heavy, slightly glazed (and not very absorbant) paper and thinned PVA. Extramite (or a similar "setting" rather than "drying" glue) would work better, but it is unpleasant to handle, so I don't usually use it.

In my experience, even if a tube does have a few air gaps in it, it will be fine for any use that I put it to. I have rolled tubes with thick wallpaper paste and lining paper that I can't deform by hand or split with a big mallet, even though they did have some little gaps between some of the layers. However, I don't press big rockets. If I did, I may find that I needed stronger tubes.

Unless you're making really high performance devices, completely solid tubes that look like porcelain aren't necessary. Ordinary hand rolled tubes are perfectly strong enough. You can always foll them a bit thicker if need be.

[paul]

I tried jeronnimos dextrine glue today. I?m impressed how d*mn adhesive it is. I boiled 50ml of tap water and put a mix of 10g dextrine and 5g rice starch in it. Soon I had to realize that this becomes too thick. Even after adding over 150ml of extra water and cooling it down it was very thick but usable. Great for casings and shell pasting!

EDIT: I made a shell around a tennisball with this glue and it got extremely hard. Harder than a shell made out of wood glue....

Edited by paul, 08 March 2005 - 11:29 AM.

[fishy1]

i just use flour paste.

[JamesH]

Over the years I have tried many different glues and papers for tube rolling.
I used to used wheat paste and lining paper but i was never happy with the results. The tubes used to shrink on their internal diameters and the layers separated upon drying - that was the thing that bothered me the most. Yes the tubes were tough but the lining paper was not strong enough for rolling rocket tubes - the nozzles used to rip out the inner layers of paper.

I now use a 50/50 PVA white glue and water solution to roll my tubes from 100% virgin kraft board (232gsm). These materials produce very strong tubes that don't shrink on the I.D. and neither do they suffer from layer separation during drying.

The trick to minimising layer separation and diameter shrinkage is to roll the tube perpendicular to the grain of the paper. However, it is slightly more difficult to roll in that direction. The reasoning behind this is the fact that paper shrinks mainly in a direction perpendicular to the grain upon drying. Therefore the shrinkage will occur on the length of the tube rather than the diameter, and layer separation is avoided.

It is also advantageous to roll the tube as quickly as possible after applying the glue, and tighten the windings up using a rolling board.

Hope thats any help to anyone experiencing difficulties with tube rolling.

[paul]

I recognized shrinking only with wheat paste! I think it is due it?s high content of water.
White glue doesn?t has this "disadvantage". At least not that noticeable.

As I got beware of that, I rolled all my tubes with white glue till then. Wheat paste is great for shells, anyhow. This is because of the shrinking. It gives the shell a bit extra strenght.

[JamesH]

The absorbancy of the particular type of paper also plays a roll in the shrinkage. Did you use diluted PVA?
I always use wheat paste for pasting my shells. It gives the casing a more brittle quality compared to PVA.

Edited by JamesH, 24 October 2005 - 10:00 PM.

[sizzle]

I just use PVA. Plain and simple, does the trick.