From syahn@tscnet.com Sat Nov  1 06:47:09 1997
To: kmfdm@iname.com
Subject: spudgun

The quality of the solvent cemented joints is very key to maximum joy in 
spudguns. I'm writing to tell you of my expertise in this area. I worked 
in the research and development department for R&G Sloane. They are or 
were a very big manufacturer of plastic pipe fittings. Fittings only,no 
pipe. Now and againe some contractor for a very big or expensive project 
would experiance some joint failures and contact us THE FACTORY to find 
out why we made junk. We got them to send us samples of the failed 
joints. We cut the open and discovered what they did wrong in making the 
solvent cement joints. These were commonly 1, pipe not sawn off 
squarely , 2,sharp corners on the end of the pipe which scraped the 
cement off the walls of the socket and making a starved joint, 3, 
plastic sawdust left clinging to the end of the pipe and scraping 
leakpaths thru the cement coating, 4,failing to chamfer the end of the 
pipe, 5, using pipe which had become out of round( this happens when a 
retailer stores too deep of a pile of pipe and the pipe on the bottom 
gets squashed over a period of time),6,not cleaning dirt off of the 
pipe,7, using the part of the end of a pipe that has been dragged on the 
ground and has longitudinal scratches which are leak paths.
General good craftsmanship is the key to proper joints. We also did 
quick burst tests of plastic pipe. This frightens grown men. The pieces 
were daggers. They stuck into the plywood walls of the test chamber. We 
tested sch 40 and sch 80. I would recomend sch 80 for potato guns 
because the wall thickness is much thicker,and the burst strength is 
much better. The only problem is that sch 80 is not common and you must 
call around at industrial suppliers for this as not everybody needs it.
 By the way the engineers always refered to the glue as solvent 
cement,never glue. One time we hade a batch of clear pvc fittings molded 
for research purposes and had our chemist mix up some standard solvent 
cement but with red and blue dyes in them. We made joints by putting red 
on the pipe,say and blue in the socket of the fitting and observing the 
purple mixing as the pipe slid into the socket. From this we learned to 
give the pipe a turning as it was shoved in. This tended to smear over 
any leak paths thru the cement. We also viewed the clear fittings thru 
polarized light to see the stress lines which formed when the molten 
plastic cooled in the mold. I got hold of some extra 2 inch caps and 
made wine glasses from them!
 I hope you might share some of this for the benefit if the spudgun 
world.

Sincerly, Stephen Yahn     syahn@tscnet.com