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Engineering a raft boat cannon

Posted: Tue Nov 17, 2009 4:53 am
by wcjmason
Hi all,
This year we are building a boat for this annual river rafting event. I have reviewed some of the posts here on the forum but they seem outdated. So i was wondering if i could get pointed in the right direction.

The cannon itself has a "turret" position so it maybe heavy, initially i has going to use a water pump to get water straight from the river and pressurize it but I read that they arnt efficient at this? Am i better off with the human powered option? What designs are there?


Re: Engineering a raft boat cannon

Posted: Tue Nov 17, 2009 5:16 am
by Drenchenator
Using a water pump isn't inefficient; it's just overkill. But since it appears you are building this from scratch, I would suggest it: It offers the most power with the least human effort during use.

A sample of this kind of design is at this forum topic here.

The performance is top of the line. It sucks water directly from the river. It would also be easy to use with a turret. Is this what you had in mind?

Re: Engineering a raft boat cannon

Posted: Tue Nov 17, 2009 9:56 am
by wcjmason
Thanks for the link, it looks good however a gas pump is outside our budget and we want to be cranking victory music so the gas pump maybe to loud. The idea was a pond pump or something cheap to suck up the water and pressurize it and then to fire it out. Is this possible?

Re: Engineering a raft boat cannon

Posted: Tue Nov 17, 2009 12:45 pm
by JuchTurtles
You could suck up water, send it through a check (one-way) valve into a pressure chamber of some sort. Then, while building pressure, aiming, finding a target, and firing.

I don't know very much about the variety of pumps and stuff so I can't really help you there.

Re: Engineering a raft boat cannon

Posted: Tue Nov 17, 2009 9:40 pm
by Drenchenator
It you want to use a pump, I suggest you shop around and look at any kind of pumps that work for liquids. I have two aquarium pumps that I used in a engineering project that work very well and are reasonably quite, but I wouldn't recommend them for a water gun. Check McMaster-Carr for some pumps, but watch out: Prices may be high and many only use electricity.

If you can't get a pump, the only human powered option is a river gun, which these two links demonstrate: Waterzooka, Sac American River gun. You can also buy these at the store.

You could build something that pumps water into some kind of pressure chamber, but that would require some planning and would not be hard to use, just maybe hard to build, thought this depends on what you use to pressure the water (air pressure or elastic pressure).

Another option, that is simple enough, is to just get a regular hand pump, and have someone pump by hand while another person aims. If you have a team of people, this would work fine, and it wouldn't need any fancy building or planning. Plus it would be cheap.

Re: Engineering a raft boat cannon

Posted: Thu Nov 19, 2009 3:01 am
by cantab
You could build a pretty standard APH or CPH, and take the inlet as a hose that trails into the river, with a filter on the end. That could be turret mounted or handheld. You could modify a stock gun to do the same thing (the CPSes 3000 and 3200 spring to mind, but it's probably best not to use dirty river water in valuable guns).

Whatever you do, make sure the raft is stable. I've built a raft and found out the hard way it was too narrow and top heavy ;-)

Re: Engineering a raft boat cannon

Posted: Wed Dec 16, 2009 10:26 pm
by Bradisfun
i say that if u have a stable enuff raft ( i have also built rafts and found out the hard way that it was very stable) that u go with a hydraulic pump and think that u should have a look at the hydraulic pump sction on McMaster-Carr