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Hi Jon, There is much figuring, FEA work, and actual unmanned testing to do before I'll know where I want to set my max operational depth to. To develop a plan, I decided to shoot for 500, but it might end up being 350 or 450. I have the same basic tube and heads as the K-350. In text documents I received with my sub, Kittredge says "the elliptical steel ends to the pressure hull are designed to withstand a pressure of 763 feet". I don't know how he did his figures, or if that was figured using A36 or A516 GR70. But I have some data that tells me those heads can take a fair bit more then that if they are made of A516 GR70. The knuckle area is by far the weakest area on those heads. Welding in supports in that area such as Carsten did on Euronaut may be needed to obtain a certain max depth. A number of K-250's were built by Kittredge out of A36 before he changed it. That means that the ones with A516 GR70 will be tougher. I have a few more test to run in when I get the sub to Portland for it welding upgrades, but at the moment I have reason to believe mine is made of A516 GR70, except the support ribs of course. I was also thinking about spacing the new ribs between the existing one today, and perhaps also double up the end ones. That might be a good way to go. I'll have to look into it further. I would be a bit tighter in regards to welding them in, even with the webs pre-welded to the flanges in stepped sections. I had thought of welding the webs to the flanges with both parts being straight and flat, then taking them to be rolled. I don't know if any one has tried this before. If I can calculate and/or find some one that can calculate the strength that the syntactic foam would give me against external hydrostatic load, then I might just be able to use it to strengthen the space between the existing support ribs instead of adding the new ribs there. Thanks for the input Jon. Are you working up a acrylic tube calculator? If so I think it would be well worth while. Regards, Szybowski > Date: Sun, 12 Jul 2009 22:23:20 -0400 > From: jonw@psubs.org > To: personal_submersibles@psubs.org > Subject: Re: [PSUBS-MAILIST] KL-250's Syntactic Foam Data > > Brent Hartwig wrote: > > > > > > Hi Jon, > > > > ** Sure I'll see what I can do. The Captian did at least one > > unmanned dive test of every K-250 he and his crew built, to 500 fsw, > > except mine, according to his book. Mine was later tested to at least > > 500 ffw by Dr. LeShack. Kittredge took a K-250 to the US Navies test > > chamber at General Dynamics and the blown dome imploded at 824 feet, > > which was very closely to George's calculations. Page 249 in his book. > Using 500 feet as a max depth for a K-250 design leaves no safety > margin. George tested to 500 feet because it was near the calculated > crush depth of the hull design and provided a 2:1 safety margin which he > could use as advertising. He didn't intend for the K250 design to > operate at that depth. > > > > The new 1.5" thick cast acrylic conning tower will be able to resist > > more pressure then that. I'll have to gather more data and run the > > FEA on that part and the rest of the new assembly and see where I'm at > > from there. I'm shotting from the weakest part, and/or assembly to > > have a FOS of 2.5. So 1,250 fsw minum. I might not be able to > > comfertabley do 500 fsw, once all the figuring is done. But I might > > have even more. We'll see what we see. > > > > I was not planning on factoring in the syntactic foam for dealing with > > the external hydrostatic load for the FOS of 2.5. But if I was able to > > obtain good data on the mechanical properties of the type of syntactic > > foam I go with, then that area of the design might very well be able > > to with stand far more then 500 fsw. Because I'm using syntactic foam > > between the support ribs. I don't plan on needing the horizontal > > weldments I had once planned to use, for collision protection and > > resistence to external hydrostric load. Because I have a good source, > > I might go with Divencell micro spheres, and a high grade infusion > > molding vynel ester resin > I'll wait to see the results since I'm doubtful that you'll have the > ability to engineer and apply the syntactic foam as you suggest. > > > > I fully expect to need to replace the forward viewport welded in > > seating ring, and thicken up the acrylic. I'm considering increasing > > the current 14.75" viewing to 16 or 17. I'm currently working thru > > the detials, and getting ready to run the FEA. According to your > > conservative viewport calculator for a 16" Di, and a operating depth > > of 500 feet, it would have a OD of 20", a thickness of 3.20". With the > > failure depth being 3,300 feet. That's an odd thickness, so I'll > > likely got with 3 or 3.25". I had guessed I would need about a 3" > > thick window there, so I must be getting better at this. ;} > Yes, you may find that 3 inch is sufficient. If you play with the > calculator to find out what water depth 3inch material will get you, you > should be able to determine what safety factor you get with it. > > > > I'm planning on installing a full set of K-350 type A516 gr70 steel > > support rubs. Right next to the extisting A36 rolled angle iron one. > > This way I get the extra strength, and I have a flang on both sides of > > the void space to better hold in the syntactic foam. The current rubs > > have a ID of 32.50". The new surport ribs will have a ID of close > > to 33" so they can overlap the current flanges, and a OD of would need > > to be about 35" to allow them to go over the top of the current weld > > bead that is against the inner hull surface. > Well it will certainly provide some additional strength, but I think > you'd be better off adding the new ribs equi-distant from the existing > ribs. The ABS hull calculator might help here. > > > > > ************************************************************************ > ************************************************************************ > ************************************************************************ > The personal submersibles mailing list complies with the US Federal > CAN-SPAM Act of 2003. 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