[PSUBS-MAILIST] FW: Casper 2

Tue Jul 31 08:39:22 EDT 2018

I think you mean 14 inch diameter, not radius.  For each pod, I'm showing a weight of 308 pounds and displacement of 410 pounds resulting in 102 pounds of positive buoyancy.  Your battery weight and lead weight totals 258 pounds which then makes each pod 156 pounds negative buoyant.
Your batteries seem light.  Most batteries I've seen in USA are about 27 kg.  For comparison, each pod of a K-350 is 235 pounds with displacement of 204 pounds making it 31 pounds negative bouyant.  Four batteries at 60 pounds increases negative buoyancy to 271 pounds.
Bottom line is that if you are top heavy you need more weight low to counter act it.  I agree with Hank in that you have a lot of weight at the top in your soft ballast tank design.  You can see that a typical K-350 design has 230 pounds more weight (both pods total) than Casper2 and it's ballast tanks are designed to be both smaller and fabricated from fiberglass.  So more weight at bottom, less at top.
Additionally, consider that my K-600 which has the same battery pod and ballast tanks of the K-350, had 240 pounds of lead weight as ballast in-between the ribs of the pressure hull.  My point being that it takes a lot of weight in some cases.
I think that if you don't want to redesign your main ballast tanks, just keep pumping lead weight into the battery pods and as low as possible in the main pressure hull until you get it stable.  Obviously this is going to increase your overall vessel weight which may result in other modifications in terms of trailering or launch/recovery.
Not sure why Casper2 doesn't show on the web site when searching by name, but it does show up if you search by submitter under Graham Bayliss.  In any event, the direct link is: http://www.psubs.org/projects/1260127846/casper2/
We should convert you over to SUBDB.INFO which has a few better tools for uploading photos and documents.
Jon

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