I need to determine what size pvc pipe I would need to make a certain weight float. Dog float.?

Asked: I need to determine what size pvc pipe I would need to make a certain weight float. Dog float.?

Hey guys, basically what I want to do as a fun project is make my dogs a float. They love to float at the river. The problem I have is that all the cheap floats are either plastic which the dogs puncture pretty quickly or they have a blow up float ring around the edge and mesh in the middle. The middle sinks if they don't lay down and distribute their weight and they panic. We used to have a nice thick foam pad that would hold two dogs no problem, but if one would start to wiggle it would usually sink the other dog off the float. Those float are also very expensive.

I've had it in my head to make a dog float. I'll cover the part here that I need the science help with. Basically, I want to take 4 pieces of PVC pipe and make a square float with 90 degree angles. I feel like I want to make it roughly 36"x36". There will also be a few spare inches added by the 90 degree angles, but that won't affect calculations much. I then plan to put nylon in the center with velcro attachments down the length of each side. It will make it hold stronger and make it pull on the PVC evenly.

Now that you have a picture in your head, of a square of PVC with nylon in the center, what I need to know is what sized PVC would I need to hold up a certain poundage of weight. For instance, if I had a square made of four 36" pieces of PVC pipe that is 4" in diameter, how much dog weight can I put in the center and still have it float.

I know there are variable, but things to keep in mind are that I'll want more bouyancy than I need, because when a dog climbs on from one side I don't want him to be sinking the whole raft and flipping the other dogs off. If I put all 4 dogs that come to the river on there, it would probably be less than 170lbs, but 90lbs of that is one dog.

It would be great if you guys could set me up an equation that I could plug different variable into it such as (total pounds = variable 1 (length of pvc), variable 2 (diameter of pvc)). Set up something like that I could figure out how big i want to make it and if I'd need bigger pipe to make it smaller.

Also, would filling the pipe with bouyant material such as great foam make it more/less/or the same amount of bouyancy. And while I have you looking at this problem, could anyone thing of a simple ramp for the dogs to help them get on the float. Anyone who has seen a dog try to get on something from the water will know that they can get their front feet on easily, but then their butts tend to sink and they really struggle to get their butt on, especially if they're older. I thought that some kind of ramp that sits just under the water would allow them to get their back feet some purchase and climb on more easily. I was half thinking that taking some 1" pvc pipes, sealing the ends, and attaching them to the backside of a strip of canvas that's hooked to the side of the main float would work. When they try to climb on, their body weight would easily push it down and if I had the pvc spaced out about 6" apart, then their feet would catch on them and it would be like ladder rungs with material in between.

I may be over thinking all this and if you guys know a simpler solution, let me know. I'm just looking for a good tough dog float that they can get onto and off of easily. Thanks for the help and be sure to check back if you have a comment or question, because I may have replied to you in the more info section. Thanks. Let me know if I'm in the wrong section.