In a message dated 10/25/2009 4:34:46 P.M. Pacific Daylight Time, lanceind@earthlink.net writes:
Frank,
Before you commit to a radial pattern of "like ribs on a pumpkin" inside the heads. I think you should get a second opinion engineering wise. Maybe even have an FEA done.
Dan Lance
Hi Dan. I haven't committed to any stiffener design yet except for the ribbing across the floor. I need that to provide attachment points for the stuff, contain and attach the ballast bricks, and give me a flat surface for the floor plates.
At this point I'm favoring the "pumpkin" ribs only because I can visualize it easily and it looks pretty easy to do. The hatch ring sticks down into the sub 4 inches and the pumpkin ribs would go from there down the sides and connect with the bottom grid. I was planning on using 1/2 inch plate cut into the curved pieces and tying them all together with round stock rather than making "T" bars.
8 ribs with a little extra at the window area seems like it would do the job.
I respect your knowledge in this area and would appreciate any advice you might offer on an alternative design.
At some point I'll have to do a real FEA on it, ( actually, I'll have to get some one else to do it ) so for now I haven't decided what exactly to do with the ribs.
In the mean time I can get it wet and do shallow dives until either I get a bit smarter or my engineer buddy
becomes available to do it.
I've made all the interior stuff just bolt on and when the time comes to put the final ribbing in, I won't have to torch out anything.
Got any good ideas on it ? I'm willing to listen.
Frank D.