On Sat, 3 Mar 2007 22:53:58 +0100, "Rob Turk"
wrote:

clare at snyder.on.ca wrote in message
.. .
On Sat, 3 Mar 2007 08:36:23 +0100, "Rob Turk"
Can you hog it out to the next size pipe thread and put a reducer
bushing in? Make sure you use a tapered pipe thread and do not
overtighten it. Make sure you use FLEXIBLE line from the tank to the
fuselage. Rigid tubing WILL eventually take the threts out of the poly
tank.


That would get me back to the starting situation; What do I use to seal the
bushing, considering nothing seems to stick to polyethylene..

Rob


There is a marine product for repairing polyethylene: PolyDura
http://www.marinetex.com/PRODUCT%20P...FAQ%20page.htm

However, the tank must be flame treated for it to adhere!

"Can I use PolyDura to fix my polyethylene gas tank?

We do not recommend flame-treating any project that may be associated
with flammable materials. Flame-treating of items such as fuel tanks,
chemical tanks, pipelines or other flammable containers is not
recommended due to the danger of explosion or fire."

For sealing to polyethylene, Dow 730 fluorosilicone rubber:
http://www.aircraftspruce.com/catalo...ges/dow730.php
http://www.skygeek.com/rtv730-3oz.html

Pretty expensive! Dow 730 is specified in the maintenance manual for
the DeHavilland DHC-8, for tacking down rubber seals in the wing fuel
cell access panels. However, the Dow 730 Product Data Sheet
http://www.dowcorning.com/applicatio...t.aspx?R=406EN
states the following limitations:

• On Teflon®1-coated materials,
polyethylene, polypropylene or
methylmethacrylate (Plexiglas®2);
sealant will not adhere well
• On or near sensitive metals such as
copper, brass, zinc, carbon steel,
galvanized iron or magnesium; these
metals may be corroded, especially
in confined cure conditions, due to
the acetic acid released during the
cure


Or, you could try a visit to your friendly ski repair shop and pick
their brains about hot-air welding of polyethylene ski bases.
http://www.svst.com/page5.html

Harbor Freight offers a hot-air plastic welder, $29.95 :
http://www.harborfreight.com/cpi/cta...emnumber=41592

This sounds like a Proseal-type compound:
http://www.patentstorm.us/patents/6113820-claims.html
Although they package 2 part polysulfide rubber compounds in
polyethylene containers, from my experience it sticks to some of them
pretty well.

Post some feedback on your results, please.

D. Anderson