<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></head><body ><div>Thanks Sean. I appriciate the explinations.</div><div>-Scott Waters</div><div><br></div><div><br></div><div><div style="font-size:9px;color:#575757">Sent from my U.S. Cellular® Smartphone</div></div><div></div><br><br>-------- Original message --------<br>From: "Sean T. Stevenson via Personal_Submersibles" <personal_submersibles@psubs.org> <br>Date:01/08/2015 9:52 PM (GMT-06:00) <br>To: Personal Submersibles General Discussion <personal_submersibles@psubs.org> <br>Subject: Re: [PSUBS-MAILIST] Scott's new sub <br><br>On 2015-01-08 20:09, swaters@waters-ks.com via Personal_Submersibles wrote:<br>> I am really new to the engineering side of all this, but am working on it. I have some questions about the calc.<br>><br>> *It shows material weight is 16351.9 n. Which I show a newton is .224lbs making material weight 3662lbs. Is that right?<br>><br>> *Displacement is 1899.67kg which I show a kg is .453 lbs making displacement 860.55lbs which seams wrong to me?<br>><br>> *Boyancy is 2277.43 n which means 510 lbs? Does that mean it is positive 510 lbs boyancy with no payload and no additional weights?<br>><br>> *at 1000m the pressure is 10.0518 MPa and max working pressure per ABS is 10.0762 MPa meaning it meets requirements. The sphere limit is 15.0391 MPa. Correct?<br>><br>> Sorry, student learning in process.<br>> Thanks,<br>> Scott Waters<br><br>Scott, my solver works in an iterative process, increasing shell<br>thickness by a very small amount in each iteration. Consequently, there<br>will be minor (but negligible) differences between the stop condition,<br>which is the pressure at the desired working depth, and the maximum<br>allowable working pressure at the final shell thickness, which is a<br>multiple of the increment. In any case, the sphere limit pressure (~15<br>MPa in this example) is the theoretical "crush", or instability<br>pressure, and the maximum allowable working pressure is this pressure<br>multiplied by the usage factor, eta, which is prescribed by ABS to be<br>0.67 for spherical shells. This is the minimum value, and you of course<br>can (and should) increase the factor of safety over and above this value.<br><br>As regards unit conversions:<br><br>1 Newton = 1 kg*m/s^2 = 0.22480894 pounds-force<br><br>1 kilogram = 2.20462262 pounds-mass<br><br>As regards terminology in my software:<br><br>"displacement volume" = volume of seawater displaced by closed sphere<br>"material volume" = volume of steel in hull shell<br>"material mass" = mass of steel in hull shell<br>"material weight" = force due to gravity acting on steel in hull shell<br>"mass of displaced seawater" = mass of seawater displaced by closed sphere<br>"buoyant force" = gross buoyant force due to displaced seawater<br>"net buoyancy" = buoyant force minus material weight (net force acting<br>on closed sphere)<br>"payload capacity" = net buoyancy divided by gravitational acceleration<br>= adding this mass inside the sphere will drop buoyancy to zero.<br><br>Sean<br><br><br><br>_______________________________________________<br>Personal_Submersibles mailing list<br>Personal_Submersibles@psubs.org<br>http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles<br><br></body></html>