28 replies to this topic

[FaithlessRock]

Thanks all for your comments. I've ordered some wax beads to give them a go.

Does anyone have any experience using wood varnish - sounds like ti would do the job just as well and it is readily available!

Cheers

[Arthur Brown]

The few card tubes that I have are plugged with polyester resin and filler and the bottom edge of the tube is also painted with resin.

[Karl Mitchell-Shead]

The few card tubes that I have are plugged with polyester resin and filler and the bottom edge of the tube is also painted with resin

Bit risky due to the expansion nature of card and HDPE for that matter. Tis why most card mortars will be bunged with wood that has been glued AND nailed allowing some give, the last HDPE 16" tube i used had something like 24 pins around the circumference holding the glued into place HDPE disc that bunged the base.

Think one or two of your 4" mortars suffered that night if i remember, oh meant to ask how did you get one with those lovely bits of 6" pipe mate?

[pyrotrev]

Or you could try this method by Myke Stanbridge:

Perhaps the cheapest, easiest and most effective treatment for paper mortar tubes is the following:
Clean out any debris, cobwebs, etc. Use PVA adhesive to stick down any 'flapping' edges.
Rinse each tube internally with a strong solution of calcium chloride in water. Allow your tubes to stand until they are just damp. Calcium chloride is rather hygroscopic and will not dry past remaining damp.
Using a 25% w/w solution of sodium silicate in water rinse each tube internally. Pour out the excess into your bucket and let the tubes dry open end up. There is a chemical reaction that produces tough insoluble calcium silicate in the structure of the paper. This hardens and binds the surface making it resistant to damage by abrasion and alkaline residues. When dried give the tube a fresh water rinse to remove residual sodium chloride produced in the reaction and let dry open end up in a warm location.
Coat your tubes externally with a mixture of spirits of turpentine 1 part (pine spirit NOT mineral turps) and boiled linseed oil 3 parts. Add 15% lampblack to the mixture if you want black tubes. Leave the tubes to dry for about two weeks, open end up... Omit this step if the tubes are for immediate use or will form elements of a boxed mortar block...

Note: I'm still using tubes prepared like this around 25 years ago, and they still function perfectly! The method of treatment is very quick and cheap once you've got set up... You can treat a hundred tubes in an hour or so for around 10 cents per tube. Painting costs around a dollar per tube and is not as effective... Regards, Myke.

I would advise against this as it's difficult to get right in practice. The problem is residual unreacted CaCl2 (+ its moisture) in the paper, when the tube is fired the moisture gets turned into steam and the pressure blisters the inside of the tube. The best treatment I found when I used to use paper tubes (though I didn't try everything) was yacht varnish thinned down with white spirit so it penetrated the paper well - but as with other methods make sure the tubes are VERY DRY before you treat them, otherwise you're just sealing in moisture.

Edited by pyrotrev, 23 February 2010 - 01:47 PM.

[CCH Concepts]

what do you guys think about the risk of hardened paper becoming projectils in the case of a cato.

[Karl Mitchell-Shead]

In the case of failure (CATO probably only relates to rocketry), card merely becomes confetti posing little or no threat.

[CCH Concepts]

In the case of failure (CATO probably only relates to rocketry), card merely becomes confetti posing little or no threat.

which is exactly the point of a card tube, but what i read stated when you vanish or otherwise treat the card it becomes harder like with firbe glass its nothing till the resin is added, but afterwards it would make shrapnel galour.

[RFD]

The cheapest method i found was to use the cheapest tesco"s extra hold hairspray,give the ends a good dosing, ends of tubes act like endgrain on timber and will soak up moisture easier and a spray on the outside,unfortunately i think you have to consider cardboard tubes as an eventual consumable,as for shrapnel,ive tested some old 3" tubes after various coatings of different waterproofings and found they either unwound or sent bits of fluffy cardboard around, i think to get a hardener to soak all the way through you would end up with paper mache.

[CCH Concepts]

cool, well next time im defiantly treating my tubes. this year i left them out over night after my attempt at a show to join the festivities and they didnt fair well. well treated tubes would have done much better.

[Karl Mitchell-Shead]

which is exactly the point of a card tube, but what i read stated when you vanish or otherwise treat the card it becomes harder like with firbe glass its nothing till the resin is added, but afterwards it would make shrapnel galour.

Hardly mate, why do you think we use fibreglass?

[mike_au]

I would advise against this as it's difficult to get right in practice. The problem is residual unreacted CaCl2 (+ its moisture) in the paper, when the tube is fired the moisture gets turned into steam and the pressure blisters the inside of the tube.

I haven't had any problems so far. I've only made up 10 mortars using this method, and the oldest has only had about a dozen shots through it but they all seem pretty dry and are all in fairly good condition.

I would say it is certainly worth trying.

[Arthur Brown]

While I have and use paper tubes professionally I strongly prefer GRP as it's possible to carry a rack full without pain! I'd regard paper tubes as for initial an occasional use only, and keep them dry with bags.

[pyrotrev]

I haven't had any problems so far. I've only made up 10 mortars using this method, and the oldest has only had about a dozen shots through it but they all seem pretty dry and are all in fairly good condition.

I would say it is certainly worth trying.

Maybe you're somewhere with rather lower humidity than the north of the UK!

[mike_au]

Maybe you're somewhere with rather lower humidity than the north of the UK!

You might be right there

Perth, Western Australia. Not exactly known for being a particularly wet area.