Making a fake time bomb

Real bombs don't usually have an LED timer ticking away the seconds. That's a Hollywood invention.

You would need some kind of clock if you want it to be timed accurately. A cell phone would work for that as easily as it works for a remote-detonated bomb (hook the detonation wire to the speaker wire).

It really depends on who he's trying to fool and how good your MC is at this sort of thing. If he doesn't really know what he's doing and he's trying to fool an expert he's not going to have much luck.

To make a believable bomb that would pass light inspection from non-experts you'd probably want something to use as a fake timer, some wires, a primer explosive (fake blasting cap or something like that) and the main charge (which you've got with a propane tank). Maybe some tape to package it all together (and obscure bits you're not sure will pass inspection) and you're set.

Propane isn't an incredibly effective explosive for that sort of thing, if he really wanted people to believe the bomb could do serious damage it would need some kind of shrapnel layer too.

Seems to me you could use almost any kind of electronics, from a handheld videogame to a microwave oven. Tear out a circuit board, run a couple of wires from it to a phone, and run a couple more wires to the bomb.

And/or your hero could wrap some duct tape around a piece of wood and make it look like a chunk of explosive. Stick a couple of wires in that, tell the bad guys it's got a motion sensor, and watch them squirm.

Why couldn't there just be some duct tape in the camper? Lots of campers carry supplies like that.

They're propane generally. Never, ever kerosine that I know of.

Just who is your MC trying to fool, anyway? Someone who doesn't know the first thing about bombs, or someone who has some expert knowledge?

A printed circuit board that he takes at random from consumer electronics probably wouldn't fool anyone who took basic electronics in high school. Something that looked homemade, possibly badly soldered, with the manufacturer information scraped off the IC chips, might give me pause, though.

I knew a guy in college who claimed to have pulled a prank of scaring away what he thought was a drug dealer, someone who habitually hogged the phone booth (yes we used to use phone booths) by taking some red construction paper and then using stencils and grey spray paint, painted dynamite on it and wrapped it around sections of broom handles, attached a 30 second section of rocket fuse (used to be commonly sold) and then when the guy was next in the booth, he walked up, taped it to the door of the booth and lit the fuse with his cigarette and calmly walked away. Supposedly the guy stopped using the booth

I second the "cover it with tape!" idea. That'll cover a multitude of sins. Do people carry tape into the woods? Depends on the person. The kind of guy that knows how to defuse bombs might well. I know a lot of people that have a Leatherman/Gerber/Swiss army knife & some form of tape in their backpack by default, especially when camping/staying in a cabin. Certainly doesn't seem unreasonable to be in the stolen bag.

Re the propane: this is more problematic. How do you plan to use it? You'd need a real bomb to make the tank go bang without a lot of inconvenient rocketing around first (so then why bother with the propane), and fuel/air explosions aren't as bomb-like as Hollywood would have you believe.

Does he even need to see it? Id' be instantly suspicious of a device a) because it's easier to keep away than get blown up, and b) if I can't see it I don't know it's real or a fake. So if the idea is just to scare someone into caution, it's almost as effective just to say "I've got a bomb and I'll blow you up if you come near here." It would be a more effective scare tactic if the bomb wasn't visible anyway, talk about trip wires or booby traps and he'll be wary to open doors/looking for it everywhere. If you make a Big Obvious Bomb Right Here then all he has to do is keep a healthy distance and it's not a problem.

Some red road flares taped together, wire, and an alarm clock might look like a bomb at a glance.

There are probably plenty of things kept in the cabin that would be useful here. Naturally that'd depend on who last used the cabin, how regularly it was used and when the last person stayed there.

Consider that in a remote location, you're more likely to keep whatever you need for instant repairs. I can see duct tape, nails, screws and razorblades (shrapnel), an old radio for listening to the weather (circuit board). Whoever owned the cabin might have left an abandoned car or generator (wires) or might even have a stash of wire left over from building the cabin (if it has electricity).

Camp stove fuel comes in propane, alcohol, white gas and kerosene versions.

To deal with the propane tank rocketing around, duct tape it right to the kidnapper's daughter.

Be sure to paint ACME Explosives on the outside. (Works for Wile E. Coyote)