23 replies to this topic

[Sam Miller]

Hi all,

I'm planning a show for the 5th (very excited as I'm building 2x30 cue firing systems to make it a well timed pyro musical) and I have alot of 3" mortar tubes to plug and waterproof. I'm used paper/cardboard silage wrap tubes which I've got off my local farmer for free! Great as he has hundreds of the things every year. The ID is 3" exactly and the OD is 4" so it has a perfect 1/2" wall. Problem is as the weather in the UK is great as always, I don't want all my mortars to be ruined when it rains! and I also need a way of pluging them!

 

Anyone got any suggestions?

 

I was thinking maybe concrete/floor leveller with a small mesh of screws in the base for the plug.

 

Thanks

 

 

Sam

 

[Arthur Brown]

Plug;

a layer of gaffer tape across the bottom and a paper cup full of polyester resin has served me well. Use dry sand as filler if you want. Aim for bore/2 as a plug thickness.

 

Also I have a local spindle turner who makes ornamental bannister spindles. He will produce wooden plugs to any size by the bag of 50.

 

Water proofing.

Card never will be waterproof but a light dip in polyester resin top and bottom will stop the cut edges of the paper taking up water.

A quick coat of spray paint will help seal the edges too.

If you want to go to extremes then a full coating outside of wax will preserve the tube.

 

On site paper tubes are well used inside dustbin bags, the bottom is off the ground and the top is closed til the shell fires.

NO you cannot leave card tubes out overnight -they go all squishy.

If you want proper waterproof tubes then buy proper GRP mortars. The time and expense of waterproofing paper tube is not worth the money compared with the cost of a commercial (Chinese) GRP mortar.

[Sam Miller]

Thanks! I'll give it ago I've got quite a few of the things to plug but one day i'll invest in GRP mortars!

 

 

Sam

[Deano 1]

Hi Sam, I used a few discs of plywood cut out with my band saw. I made them tight so that I had to tap them in with some wood glue smeared inside the tube, then I screwed through the tube wall into the discs, then I poured an inch of polyester/fiberglass resin into the tube making sure you don't drip any on the inside walls of the tube. I fired some of them tubes at least a dozen times, and then the walls started to peel. good luck matie.

[Sam Miller]

Cheers dean, I'll give it all ago and see what's quickest and easiest !

 

For then length of the mortars am I correct in thinking 18" for a 3" mortar? and with a 3" plug that'll be a 21" tube?

 

 

Sam

[Arthur Brown]

Slightly longer tubes will usually give slightly higher lifts, so long tubes should be fine

[Vic]

Hi Sam, How I did mine cut disks from ¾”- 1” pine glued in with cascamite wood glue you need this as it won't shrink, it will fill up the voids in the not so perfect disc cut with a jigsaw. Then four screws. To proof them I used wood hardener and then a coat of black board paint to finish

[Karl Mitchell-Shead]

Be cheaper just to buy tubes from Essex Tubes?

[cooperman435]

PVA glue is an excelent waterproofer as thats its intended use in the building trade, ts not a LONG term barrier but for a night of rain its fine.

 

Free must be cheaper than buying anything chief?

[pyrotrev]

Your idea of using wood hardener is a good one (even if it's not the cheapest stuff) as it penetrates very well: dry your tubes well, leave it inside for a while and it'll go in quite a long way and help avoid getting blebs on the inside caused by water in the cardboard being vapourised by the heat of the lift. Before I moved on to GRP tubes I used to cut disks of plywood with a tank cutter (grind the cutter head the opposite way for the cleanest cut) to plug the bottom: 2 pieces of 19mm stacked and glued in with PU adhesive seemed to do just fine for a 3".

[starseeker]

We use card tubes and to water proof ours we just wrap pallet wrap around the racks once they are loaded,cheap,quick and no worrys

[charlie3]

Be cheaper just to buy tubes from Essex Tubes?

Agree Chief. Alot safer and reliable as well !

[Karl Mitchell-Shead]

PVA glue is an excelent waterproofer as thats its intended use in the building trade, ts not a LONG term barrier but for a night of rain its fine.

 

Free must be cheaper than buying anything chief?

 

Not when safety is an issue.

[Sam Miller]

I think I might go for buying GRP tubes, they'll last longer than the cardboard tubes and there's the safety issue  which chief said. Can anybody point me in the right direction for the cheapest place to get them? 2" and 3"?

 

Thanks

 

Sam

[digger]

I think I might go for buying GRP tubes, they'll last longer than the cardboard tubes and there's the safety issue  which chief said. Can anybody point me in the right direction for the cheapest place to get them? 2" and 3"?

 

Thanks

 

Sam

 

There is no reason why GRP tubes are any safer than cardboard tubes, the bursting pressure of a 3" x 15mm wall card tube far exceeds that of a GRP tube. In fact a properly prepared card tube can often outlast a GRP tube. Not all GRP tubes are equal in quality, there are some cr@p ones out there for sure. With either type of tube you should inspect them for damage and chuck them away when they have reached the end of their life.

 

The main advantage of GRP is weight, card mortars are heavy.

Edited by digger, 04 August 2013 - 09:44 PM.