Sleaving large-bore pipe for added streangth?

[Bonggoggles]

Where does the president keep his armies?
In his sleevies.

Has anyone tried sleeving larger diameter pipe? My idea is to sleeve a solid piece of 4" sch 40 into a piece of 4" sch 40 that is sliced lengthwise down the center on a table saw. It will leave a gap, but over all, it should be considerably stronger. Is the gain worth the effort? Would it be stronger than sch 80 for a hybrid design?

I was also thinking about sleeving some 2 1/2" with 3", centering it with spacers and filling the gap with spray foam (the non expanding stuff for windows and door jams). I know this would be strong but I would prefer a shorter, wider chamber to a longer, narrower one.

One last thing. Would using small screws at the joints increase or decrease the over all stength of the joint?

[boilingleadbath]

You'll never be able to bond the 4" sleeve well to the 4" - which will result in very little improvment, if it's not counterproductive. Furthermore, you'll be spending more money on fittings - just go with sch 80 3".

Same goes for the 2.5" in 3" idea.

If you solvent weld correctly, in will not be neccisary to use bolts; the pipe will fracture before the fitting fails. The bolts might even make it worse; because they will yeild less (unless you use synthetic bolts) than the PVC bond area, there will be higher stress on the PVC in that area, which could lead to a fracture forming... and of course, the area taken up by the bolt can't support tension, causing a area of increased tension surrounding the bolt.

[Bonggoggles]

Thank you, BLB.
I figured it wouldn't do much good. Sch 80 is scarce around here and there is an abundance of sch 40. It seemed that doubling up some 40 would add strength, but there really isn't any feasible way to accomplish that.

[boilingleadbath]

You know, sch 40 1.5" is rated to the same pressure as sch 80 4". It'd save you from ordering pipe, which considering shipping prices, is a very good thing.

[Bonggoggles]

Ya, I don't have the scratch to shell out on ordering materials right now. I can get stuff from home depot on my work account. (I work for a building contractor) My boss is very lenient when it comes to paying for my personal supplies. I think I will have to shelf my current design idea and wait untill work picks up in the spring. I'm usually sitting pretty fat on cash then. It sucks, though, because I'm bored now and when I have the cash I'll be super busy with work.