Re: [PSUBS-MAILIST] Re: Greg Cottrell's Sub

[Jon Wallace <jonw@psubs.org>]

Cliff, Dan,

Thanks for the great information.  I'll try to capture this discussion 
for the Wiki.

Jon


Daniel Lance wrote:
> Jon,
> Greg will be first one to admit that if he had it to do over again he 
> would not put stiffening ribs on the heads of his sub. He readily 
> explains that when he began constructing his sub in the late 1980s his 
> enthusiasm for building  out paced his knowledge of the engineering 
> principles involved. When we did the refit and added tee bar 
> stiffeners internally in the cylinder section theoretically  we 
> increased his dive capability.  In reality he still had the problem of 
> the external ribs on the hemi heads.They are undesirable  for two 
> reasons. #1 The heads should be allowed to compress in a uniform 
> manner. The ribs prevent that. #2 The ribs were not welded on using 
> full penetration welds. If there is a weld failure any number 
> of unpleasant things could occur. In the end we decided it was not 
> cost effective to remove them . Greg is currently building a new sub 
> incorporating all the lessons he has learned along the way.
>          Stiffeners on cylinders are fine. On elliptical heads ,hemi 
> spheres and spheres they are not.     Did anyone see stiffeners on the 
> DeepWorkers or on the hemi-heads of the Aquarius?
>   This issue illustrates the potential hazard of designing a sub just 
> by looking thru the Psubs photo gallery or the archive. Because some 
> one else did it and took a picture of it does not mean it is an 
> acceptable method. Unfortunately as a group we lack a peer review 
> mechanism to sort photo gallery or archive entries into categories 
> that could prevent this type of misunderstanding . 
>  
> Dan Lance
>  




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