SpudFiles

Oh, actually you can get those here...

EDIT: Actually, helium isn't that expensive, you just need to know where to look. And yeah, I didn't say hydrogen because it's flammable/explosive/dangerous for that use.

I believe a 55 gallon drum empty will support 500lbs. When it comes to presurizing the PVC, I would'nt, I don't know much about scuba diving but if their tanks have a few thousand pounds of pressure, why do they still sink instead of floating?

I have an inflatable kayak that can support 500 pounds. it is about 12 feet long and has 2 tubes that are about 6'' in diameter. so 3 people, maybe a total of 30 feet.

If i were you i would lay them all out and and cut then into 4 equal sections and attach them to the bottom of a peice of ply-wood. I also would NOT put air pressure in it because the water it make the pvc cold and brittle.

Maybe, just maybe ABS would be better suited for this.

Orpackrat wrote: if their tanks have a few thousand pounds of pressure, why do they still sink instead of floating?

yes, a scuba tank all ready to go will sink.

for buoyancy you want as large a volume and as little weight as possible, therefore as opposed to pressurising your PVC vessel, you should be looking at ways to evacuate it - nothing weighs less than nothing after all

Cell core ABS would be your best bet.
Impact resistant, light weight, durable!
Oh and would having a vacuum in the vessel help?

Kind of random but...

You should put on a check valve and then a ball valve and attach that to your raft. You can pump it up and it shoots out bubbles when you open the ball valve. You could also have a water tank so its propelled by water. Maybe you could do a combustion too.

hi wrote:

Orpackrat wrote: if their tanks have a few thousand pounds of pressure, why do they still sink instead of floating?

yes, a scuba tank all ready to go will sink.

Yes, if I were to drop a 12 gram Co2 into a lake it would sink immediately but if the Co2 was opened and the gas was allowed to expand and fill a bag with the expanded gas, it would shoot to the surface.

Basically, the same amount of gas is more buoyant in a larger low pressure area than in a smaller high pressure area.

What I would do is install a pressure chamber on top with a valve that would allow the buoyancy tubes to be pressurized upon opening. With this, if you ran agains some sharp rocks and cracked the bottom allowing water to seep in, partially opening the valve would increase the buoyancy tubes pressure pushing the water out and keeping you a float a bit longer.

Use water jugs from drinking dispenser. They are 5 gal and light. Taller than PVC it will bring your raft higher off the water, more free board.
Cheap/free if you liberate them. If a 55 gal drum will float 500 lbs 11 jugs will do the same. The jugs can be spread out on raft for stability. It would be easy to keep adding jugs untill ya get the right lift.
I have thought about this before.
Have a great time Huck Fin!!

Orpackrat wrote: I don't know much about scuba diving but if their tanks have a few thousand pounds of pressure, why do they still sink instead of floating?

they have extremely thick aluminum walls, and the air is at very high pressures (denser, more weight) so there is no way it would float.

Up in ohio we use trees.

Pros:
very strong
free
fairly lightweight (if you use the right kind)
no solvent welding
never leaks
doesnt shatter when you drill/nail
authenic look
wont disolve if you happen to wash into a lake of acetone.

cons:
worse for environment
heavier than pvc=
slightly less buoyent

</sarcasm>

Good luck with this project. You can buy heilium at any party supply store and also at walmart. A better option would be to draw a vaccuum in the floats, but then they might collapse

schmanman wrote:

Orpackrat wrote: I don't know much about scuba diving but if their tanks have a few thousand pounds of pressure, why do they still sink instead of floating?

they have extremely thick aluminum walls, and the air is at very high pressures (denser, more weight) so there is no way it would float.

It was not an actual question, when others were saying pressurizing the PVC would make it float better, this is somewhat of a comparison. If pressurizing the PVC makes it float better, then pressurizing a scuba tank with a few thousand pound should make it shoot to the sky, but instead it still sinks even though even though it is at a higher pressure. The scuba tank still sinks the same, mabe a hair faster, so pressurizing the PVC will not give you any extra buoyancy.

Basically it was a question that would make someone understand why pressurizing the PVC would not give any extra buoyancy.

cork9 wrote: increasing the pressure of air in the flot u increase the volume of air there for makeing it more boyant

just...no, do you believe the statement you just pulled out of your ass?

EDIT: didn't see the 2nd page...

wow no joke I seriously was just about to do this with my friend but 4" end caps are really expensive which is dumb. I think that 4-6 would be fine. Then just put a sheet of plywood on top of it and bolt it down.

dont bolt holes into the pvc, water will get in it and you will have no way to get it out.

if you do this the pun epoxy around the bolt.

you will also want a relief valve. it the tempature is really hot, then pressure will build up and you will need to let it out. a simple ball valve will do.