Dan.Cummins's blog archive for January, 2011 - RC Groups
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Archive for January, 2011
Posted by Dan.Cummins | Jan 20, 2011 @ 01:07 AM | 12,259 Views
SUMMARY: Basic story is that some local San Diego slopers were looking for a quick and dirty way to obtain better wet seams with out being a proctologist, rocket scientist, a millionaire, or some sort of mechanical genius.

Goal is to find a bladder material that is readily available and can be inflated without elongating in the mold. If the bladder elongates, all that material that you so carefully laid into your mold just got moved around. So after a bunch of trial and error, Throne and AJ found that you could use a bicycle inner tube IF you prestretch the inner tube such that when inflated, it doesn't elongate.

Technique works best on closed molds, but can be used on existing molds with canopy openings.....but at much lower pressure...which works fine for most applications. Inner tube will conform 100% to inside of mold at relatively low pressures (as little 5 to 7 psi is plenty for most applications.....more pressure is better up to a point). Minimum tail boom diameter is limited to the width of your deflated (into a ribbon) inner tube. For a 5/8" bung hole, I use a 1.125 to 1.250 ten speed inner tube. I have given up trying to use used inner tubes, new ones are cheap and pop less frequently. Limitation of standard butyl rubber inner tubes is that they are limited to about 3X diameter inflation. Ward Hagaman is planning to do some testing using some Latex inner tubes that are 3X the cost but have a potential of 7X diameter burst inflation. Last goal...Continue Reading