<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px"><div id="yui_3_16_0_ym19_1_1471530034571_2707">Sean,</div><div id="yui_3_16_0_ym19_1_1471530034571_2707" dir="ltr">I have been thinking about GPR sphere's and wonder at what point they make sense, if ever. When you consider the huge cost for foam buoyancy and factor that into the total cost. If a sub can be built with little or no need for additional buoyancy, then the cost of GPR does not make sense. My sub Elementary 3000 is at that limit. The cost for foam buoyancy is under 10K, but if I want to go deeper it gets crazy pretty fast. So it makes me wonder if a GPR sphere makes more sense than exotic steel or thicker 516-70. To figure this out I have to start with a sample depth rating for a GPR sphere. Could you run a couple samples through your program for me? I would like to compare 50 inch ID at 2 inches thick and 4 inches thick. I had a chance to look at a GPR sub (Wrangler built by ISE) in Nelson of all places. I was amazed really, the hull is about 2 inches thick with no rings and the two aluminum dome seats sealed right on the GPR at each end of the hull.</div><div id="yui_3_16_0_ym19_1_1471530034571_2707" dir="ltr">The dome on Gamma is the spare for the Wrangler sub. The people selling it now claim it could be certified to 2,000 feet, that is quite impressive for GPR if it is true.</div><div id="yui_3_16_0_ym19_1_1471530034571_2707" dir="ltr">Hank</div><div id="yui_3_16_0_ym19_1_1471530034571_2707" dir="ltr"><br></div></div></body></html>