Instructables

Step 2: Floatilla

About 2400 soda bottles in two wood pontoons float this beast. I tried to do some buoyancy calculations by estimating final mass and volume. And I predicted that it would float about 50 percent of the boat below the surface. I was right.
 
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ecarroll13 years ago
Here in SW VA we have a Coke plant and I can get 50 gal plastic drums that are fused together at top and bottom and only the lid which is a pain in the rear to get out is the only "leak" point. You have to buy 8 at a time and you get 8 for $40. 8 of those should float a "titanic" sized pontoon.
if those are two liter bottles, u guys drank 4800 liters of soda. wow
Silence4 years ago
I wonder if you could get away with a few rows of those 55 gallon plastic drums. If you strap em to your new frame and weld up a cone to fit for each row, you would have a damn good pontoon with low resistance to movement in the water.
deceiver (author)  Silence4 years ago
I can tell you from past experience that you can float almost anything with drums like that. We had a steel raft with a heavy plywood top. The raft was about 12x12 feet and very heavy. It took 4 men to successfully move one of it's three sections. Two rows of three barrels (6 in all) floated it very high in the water. The barrels on their sides were at least 60% out of the water.
Ummm ... I hate to sound dumb but, aren't the bottles completely enclosed inside the hulls and never coming into direct contact with the water?

If so, the only purpose the bottles serve is if you sprung a leak. If the hulls are sealed up and watertight, aren't THEY providing all the bouyancy?
deceiver (author)  nunja business4 years ago
 Actually if you look at the picture of the back of the boat you can see that the pontoons merely contain the bottles. They are open to the water completely. The point was that it is an expense and difficult to built and seal pontoons. The bottles solved that problem.
Gotcha! I thought the pics were while it was being dismantled and I assumed that was partially broken down.
deceiver (author) 6 years ago
The redemption center. In Maine we recycle our soda bottles. We turn them in to centers for a nickel each. You can buy them back too.
haha I was just thinking to myself, that's like $120 worth of bottles. I'm a Mainer as well, it's definitely a cool idea with all the little ponds and lakes around.
deceiver (author)  moddedpryck4 years ago
 Yes it is. In southern Maine we have hundreds of lakes. Just the small area of several miles here we have 22.
Southern Maine huh? You ever heard of Dayton? it's a tiny little town near waterboro lol
deceiver (author)  moddedpryck4 years ago
 Dayton, Yes, I was a teacher at Massabesic schools. Waterboro is one of the town in that school union. The school i taught at was in Waterboro. The jr. high.
Small world!
in michigan we get ten cents each!
crickle3215 years ago
Would pressurizing each bottle add any significant buoyancy? I figure the room temperature air pressure would reduce when in contact with cold water.
Pressurizing the bottles would not add buoyancy unless the size of the bottle grew. In fact, if you just crammed more air and the bottle didn't expand, the bottle just became more heavy (only slightly). Buoyancy is only dependent on the volume of the water displaced, i.e. the volume of the outside of the bottle. The fact that the water level changes with seasons is interesting. What must be happening is that the cold water does cause a significant enough change in internal bottle pressure to cause the bottles to shrink down a little.
I agree with you that buoyancy is dependent on the properties of displacement. I should have added to my question that I meant pressurizing as making the bottle firm and difficult to dent.

Empty plastic bottles at normal atmospheric pressure (with lid) can be squeezed easily. Compressing the bottle would decrease the volume and affect displacement. My idea wasn’t to make the bottle grow but just maintain its buoyancy underwater.

Fresh water produces approx 0.43 psi per foot, so if the boat’s lowest point is 3ft then the lowest bottles are squeezed by about 1.29 psi. Granted the volume lost per bottle would be small but depending on the boat size, the net loss could decrease by a several bottles worth of buoyancy.
this is actually a good point. pressurizing would prevent against bottle crinkle both from depth and cold. creating some kind of pressure chamber that you could fill the bottles with almost warrants another whole instructable. another idea would be to fill the bottles with really cold air, then close them so that when they come back to atmospheric temperature, they are above atmospheric pressure.
Yeah, a pressurized chamber would be quite extravagant. One teaspoon of dry-ice would probably do the trick.
An easier, safer way to pressurize bottles is to put them in the freezer with the lid off for a while, then take them out and immediately cap them. As they return to room temperature, they pressurize. I've done this to push dents out of mangled bottles. Even easier would be to build the boat in winter and leave the bottles outside prior to capping. That way you're not complicating things (merely changing where you store the bottles), but you still gain any benefits pressurization offers. As has been mentioned, the idea works great as is, so the cold air method is as far as I'd been willing to go to try to "improve" on things. No point in using pop bottles if your going to make things overly complicated anyway.
deceiver (author)  Kveldulf4 years ago
I just took the boat completely apart. I had about 40 of those huge clear plastic bags that they store bottles in. Winter maybe, but boy, I'd have to have a pretty large freezer! And ironically half the bottles, the ones below water line, were collapsed about 30%. I think that over the years either the cap seal leaked some or air escaped via the plastic much as it does in a balloon over time.
Man, that sounds like a better part of an afternoon. Was it winterizing or just masochistic fun? ;-)
deceiver (author)  crickle3214 years ago
Complete dismanteling of the boat. It's been in the water for many years. never removed. Even iced in some. Life over. sigh...
Sounds like a new boat is in order. Maybe a 'Soda' bottle jetski ???
deceiver (author)  crickle3214 years ago
No, a slimmed down one. I'm a welder now. So, it will have a framework of pipe with floatation of PVC tubes. A bit smaller and simpler.
ANOTHER option is to add something to the bottles to make them more stiff. something like painting epoxy on the surface. you would need to do some test bottles to see how much you need to add and then figure out if the extra weight of the epoxy is worth it.
deceiver (author)  brittohalloran5 years ago
And decide if you want to go tot he expense and time of epoxying 2400 soda bottles. Really folks. It floats nicely just the way they are. Anything else would be overkill.
deceiver (author)  brittohalloran5 years ago
This is so true, buoyancy is contingent upon volume and mass. And since the mass doesn't change only a volume change could affect floating. But I'll tell ya. In the spring when the water is still a bit cold to swim but the ice is out, those bottles are 25%-50% collapsed. So, pressurizing would help in that instance. For me it just means that the boat floats a few inches lower for a few weeks. Since it's usually 50/50 in and out of the water it doesn't matter.
chrisnotap5 years ago
did you pressurize the bottles at all or is it not necessary?
deceiver (author)  chrisnotap5 years ago
not necessary.
fslade5 years ago
Come to Pennsylvania. We recycle but there is no deposit or return fees with soda bottles glass or plastic. Recycle centers have heaps of soda bottles. Drive by on recycle day and pull as many as you wish right from peoples recycle cans. You can call local "townships" and speak to a supervisor and probably load what you want free of charge.
deceiver (author) 5 years ago
I don't think the bottles would hold extra pressure for very long. Anyway, cold water in the spring does cause less floatation.. but by a couple of inches that's all.
That's kind of cool. I figured the difference in buoyancy would be minute. But then again a few inches can make all the difference if your boat rides really really low. ;)
where do you get all those bottles?