how much explosive would it take to destroy a ship, a tank or something simular ?

The question is way too vague. What do you mean by destroy? The You can get a mobility kill on a tank with a fairly modest chunk of explosive.

Same with a ship if you could hit it in just the right place.

pretty vague. Do you want to blow a hole in it? how big a hole? explosives inside or outside? Or break it into small pieces and vapor and melted metal?

The last, would take the largest amount of explosives. I'm not an expert, but for a large warship, which has a hull thickness measured in feet, would take many tons, with the explosives attached directly to the hull. A WWII torpedo carried 500 pounds of explosive and could punch a hole in a large warship, but that's all. It took many of these to sink it, and that does not count as "blown up".

So even with tons of explosive attached to the hull, you would break it in half, but the stern and bow would still be mostly intact.

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It all depends on what type of explosive you're using. It takes a lot more dynamite than Semtex or C4 to get the same results. And a lot of the answer depends on how good you are at setting a charge. The poorer a job you do, the less effective the result will be.

Doug

For a tank: 125 pounds of military grade explosive, properly shaped

http://en.wikipedia.org/wiki/AGM-65_Maverick

Pick any of the below for anti-ship

http://en.wikipedia.org/wiki/Anti-ship_missile

20 tonnes of TNT (or equivalent) would take down practically any ship.

I HAVE TO ADMIT; THIS SOUNDS LIKE A STRANGE PROJECT.

I HOPE THIS IS ON THE UP AND UP; FOR YOUR SAKE.