I have a standup boxing bag.

 

 

The base is filled with water, but it's too light. When stuck the base jumps up. 

 

How much heavier is concrete than water, and what type of concrete would I use?

 

TIA. 

The base doesn't look big enough and probably still going to move if filled with cement. 

More information:

 

This product includes a plastic base that can contain 28 litres of water and up to 38 kg of sand to ensure good stability

 

I believe that one liter of water is 1kg, so adding sand instead would take it from 28 to 38kg. 

 

Sand has the advantage that you can get it out again ???? 

 

I'd fill it with as much sand as will fit, then fill it with whatever water will fill the gaps in the sand.

 

Does it have any means of fixing to a baseboard (which you can stand on too)?

51 minutes ago, Crossy said:

Does it have any means of fixing to a baseboard (which you can stand on too)?

It doesn't. 

 

 

 

What's the easiest way to buy 38 kg of sand? 

Just now, JeffersLos said:

What's the easiest way to buy 38 kg of sand? 

Local building supply place, do you have a means of moving it?

Get an old tyre and fill it with a concrete stone mix and get someone help you lift it up and put over the bag. 

Once the mix is set of course.

Actually, the sand from our building place comes in large rice sacks, a couple of those place over the base (already with water) and it's not going anywhere until you want it to.

 

or this :   

 

7 minutes ago, rumak said:

or this :   

 

Nah...you're literally only talking about 2 or 3 bags from Thai Watsadu...38Kg is not a lot.

Velcro tape