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Re: [PSUBS-MAILIST] Hello; Design; Materials; Thanks



Jay,

Thank you for the clarification. 

"I think the issue that most of the people on here...that it doesn't really cost any more to go to a deeper depth." 

I understand that reasoning, and it's extremely valid.   However, this reasoning represents a cost/benefit analysis rather than an analysis of design viability.  Furthermore, it speaks to the philosophical idea of "as deep as you can afford" which makes sense, considering the amount of work is the same.  However, it's also a calculus based on sunk costs, and fails to include continuous running costs and maintenance.

Consider this perspective: a thin shell of mild steel will forgo deeper depths, but what it loses in ability it gains in maintenance.  Mild steel plates of a thin profile are more ubiquitous than plates of a greater thickness -- more or less.  In fact, the thicker the hull plating, the more specialized it becomes.  In a pinch, I could always weld a thick plate to a thinner one and enjoy roughly the same psi-resistance, but the reverse is not true, as the vessel can only withstand the pressure of its weakest plating.  When it comes to a boat in near continuous operation, the higher the serviceability, the lower its running costs.  All of which is well worth remaining in "milder" 30' - 60' depths. 

Now, in terms of budgets, I think I can agree with that assessment. Most people aren't' used to building in terms of volume and displacement.  Honestly, I modified the dimensions of a sail boat figuring the greater part of the weight/interior placement was done.   I added 5' fore and aft for control/engine stations and included another half-foot to the beam; all cylindrical, of course  My design might be a bit ambitious for my resources, and I appreciate you pointing that out.  I have no frame-of-reference for what is "big" in terms of submersibles, which is one of the reasons why I'm posting here. 

In terms of "safety" on something like the Russian sub, it wouldn't be too difficult to infer it's dimensions and ability.  Although this isn't mentioned, I figured it's an ambient submarine, considering it's depth restriction to 30', the number of portholes, and it's comparative lightness.  At one point his sole motive force were bicycle peddles attached to a propeller.  There's no reason why this design couldn't be into something safer. 

I have my reasons for wishing to keep my op-depths shallow, and my only request is that the community graciously help me clarify this concept. 

-T



On Sat, Sep 19, 2009 at 11:27 AM, Jay K. Jeffries <bottomgun@mindspring.com> wrote:

TC,

I think the issue is that most of the people here on the list that will give you some advice have looked at what it costs to build a shallow ops boat and one that has a deeper range and conclude that it doesn’t really cost any more to go to a deeper depth.  When they also run the numbers, they find that a sub with the dimensions you propose is outside of the budget of most home-builders.  And finally, a larger sub presents launching and handling issues.  There are very few large PSUBs, 1 completing construction and 1 undergoing sea trials in Europe along with a very innovative sub being built in Colombia for a US party that uses unusual hull materials that if successful, will open up opportunities for more large PSUBs.

 

When the membership considers subs similar to the Russian tinniest sub, there are a lot of safety issues that remain difficult to resolve.  Safety is paramount and the submarine community (the big boys) is very conservative, as a result they have few large catastrophes, many PSUBbers also hold these values.

 

Don’t be discouraged, the PSUB group sees a lot of new comers approach the list with ideas of building a larger submersible with some characteristics that are out of the norm.  Over time, these new comers if they are serious and stick around, usually end up with a more economical and easier to build smaller sub.  Those that don’t clearly define what they want their sub to do early on and perform a lot of research and supporting calculations usually pay for it later upon launching and sea trials where stability and trim issues finally become obvious…there are a lot of sub lawn ornaments and garage queens out there.

R/Jay

 

 

Resepectfully,

Jay K. Jeffries

Andros Is., Bahamas

 

Save the whales, collect the whole set.

 

 

 

From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of T.C. Craig
Sent: Saturday, September 19, 2009 1:43 PM

Subject: Re: [PSUBS-MAILIST] Hello; Design; Materials; Thanks

 

Dan,



If by "sarsacm" you mean my last comment to Alan, I can tell you that I wasn't trying to be sarcastic.  I was having an honest moment of revelation. 

That being said, you might be sensing some frustration with the process. 

When I say, " I'd like to build a 25' long submarine with a 6.5' diameter that has a crush depth of 80' " what I'm hoping to hear is,  "oh!  Why didn't you say so.  Traditionally, depths of 80' to 100' require roughly 3/8" steel +/- usually reinforced with x-type stiffeners though you need to run a full calculation.... "  Or, "TC, you're running in such shallow water (6' - 30'),  5/16" or less would work reasonably at those depths, as would (gasp!) GRP/composites, but those aren't ABS recommended, of course you'll have to do the full range of analysis, and probably run ambient." 

I think a lot of people come to this board expected to get a very informal/rough estimate of the viability of their vision, only to be disappointed by the repetitious suggestion of more research.  While research isn't bad, obviously, I think this board is seen as a resource to fill in the holes that other research didn't provide.  I know that I've had a huge problem finding design discussions of super shallow depths, that I hoped this board would fill.   Few are designing shallow divers, and even fewer are talking about them. 

For instance, does anyone remember the "tinniest sub in Russia"?  I don't recall his name, but his tiny sub could travel one-hundred kilometers and dive 30'.  And he built it during an era of sever soviet oppression.  That seems like a design to work with. While I'd certainly change the outside design, it looks like a fun, long distance craft that gives a nice taste of submarine travel. 

R,
-T