[PSUBS-MAILIST] Commercial question

Tue May 20 16:00:17 EDT 2014

If you are asking specifically about horizontal thruster power, that is a bit of a more difficult question.  Power varies with the cube of speed, so if you can accept a slower design speed, you can get away with much smaller propulsors; however, you need to at minimum be able to counter the horizontal currents you will encounter in service, which will be dependent on your operating area and operating SOPs with regard to current.  Drag comes from two sources: form drag, and skin friction drag, and in both cases is proportional to the square of the vessel speed.  Skin friction will be about the same with horizontal flow (the skin area is the same, but when moving horizontally, the local velocities change), but the form drag changes significantly, generally with increased area presented to flow and decreased streamlining.  Your best best is to either do some CFD, or scale model tests. 
Sean 

----- Original Message -----

From: "via Personal_Submersibles" <personal_submersibles at psubs.org> 
To: "personal submersibles" <personal_submersibles at psubs.org> 
Sent: Tuesday, May 20, 2014 6:21:35 AM 
Subject: Re: [PSUBS-MAILIST] Commercial question 

Better a question for Phil, I think. Gamma has 2 hp and weighs 2 tons. PC-12 had a combined 13 hp for 8 tons (10 main plus two horizontal and one vertical maneuvering thruster). The Pisces boats used a pair of 5 hp thrusters for 12-12 tons. So it is beginning to look like about 1 to 1.5 per ton, now that I think about it. 
Vance 

-----Original Message----- 
From: Alan James via Personal_Submersibles <personal_submersibles at psubs.org> 
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Tue, May 20, 2014 12:40 am 
Subject: Re: [PSUBS-MAILIST] Commercial question 

Phil / Vance, 
as a rule of thumb what would be a reasonable combined hp for horizontal travel 
per ton of displacement, for a recreational sub. I make the distinction of recreational, 
as it would probably require less than a working sub that can't be as selective of it's operating environment. 
Thanks 
Alan 

From: via Personal_Submersibles < personal_submersibles at psubs.org > 
To: personal_submersibles at psubs.org 
Sent: Tuesday, May 20, 2014 9:41 AM 
Subject: Re: [PSUBS-MAILIST] Commercial question 

For instance: Tide changes in the Gulf of Suez are abrupt and run to 6-7 knots. Try flying out from under an oil rig with THAT going on!!! Disney has no thrill rides to match it. Anyone having questions about crash bars in front of viewports should try riding 6-tons into an immovable object in spite of everything you could do to avoid it. Got me a couple of fresh gray hairs, that time. 
Vance 

-----Original Message----- 
From: Phil Nuytten via Personal_Submersibles < personal_submersibles at psubs.org > 
To: Personal Submersibles General Discussion < personal_submersibles at psubs.org > 
Sent: Mon, May 19, 2014 4:43 pm 
Subject: Re: [PSUBS-MAILIST] Commercial question 

A ‘box canyon’ type current pin is as Vance answered – the term comes from flying light aircraft into a box canyon – you can get into a situation where it is too narrow to turn around and the box end of the canyon is approaching fast –if you try to gain altitude to get out ,your ground speed diminishes to where you will hit the end of the canyon before getting high enough to get out. It’s a situation where, if you get yourself into it – yer gonna crash! 
In the case of    submersibles, it’s where you’re proceeding with a reef of rock or coral higher than your sub beside you and a strong current coming from behind, if the reef/bank/cliff takes an abrupt turn in front of you, and you have to  make a tight turn to avoid banging into it, the tail current can push you broadside against the reef with enough force as to pin you there - and your thrusters may not be powerful enough to free you. Not a desirable situation! 
Phil 

From: Sean T. Stevenson via Personal_Submersibles 
Sent: Monday, May 19, 2014 10:09 AM 
To: Personal Submersibles General Discussion 
Subject: Re: [PSUBS-MAILIST] Commercial question 

Vance - when you were piloting subs in the oilfields, what contingency plans were in place for rescue in the event of becoming disabled? 

Sean 

On 2014-05-19 10:46, via Personal_Submersibles wrote: 

Pinned into some kind of "only one way out" configuration by the currents. Kind of nerve wracking, that one. 
Vance 

-----Original Message----- 
From: Brian Cox via Personal_Submersibles mailto:personal_submersibles at psubs.org 
To: Personal Submersibles General Discussion mailto:personal_submersibles at psubs.org 
Sent: Mon, May 19, 2014 10:38 am 
Subject: Re: [PSUBS-MAILIST] Commercial question 

What are  ‘box canyon’ current pins ?  I don't want to get stuck in one ! 

--- personal_submersibles at psubs.org wrote: 

From: Phil Nuytten via Personal_Submersibles < personal_submersibles at psubs.org > 
To: "Personal Submersibles General Discussion" < personal_submersibles at psubs.org > 
Subject: Re: [PSUBS-MAILIST] Commercial question 
Date: Wed, 7 May 2014 22:31:18 -0700 

Hi, Scott, 
The major reason that quite a few operators prefer subs over ROV’s is the absence of a surface  tether. This allows you to go places that you shouldn’t and wouldn’t go with a machine because the risk of entanglement – inside platform legs, pile jackets, etc., There are a number of other reasons that have to do with the operators senses being right on the site rather than a half a mile away. Difficult to explain is the ‘whole grasp’ scenario that ROV operators who try manned subs almost always mention. Simply put, in a sub with a wide view port or a 360 degree dome,  you have a strong sense of where everything is – how long ago you passed that pipeline, what direction it’s in to go back to, the lay of the bottom,  the trending of the currents, where to find lees to hide in, how to avoid ‘box canyon’ current pins, the ability to hit ‘auto altitude’ and fly a fixed height above a pipeline or cable regardless of the bottom (and therefore the cable’s) undulations. When it comes to doing complex work using manips, there’s no contest man versus machines. Machines do get the work done if they are set up properly, but much slower and with many tries, compared to the pilot whose hand on the joystick is five feet away from the work . 
You often hear ROV types say ‘well, it’s just the same as being there”. . .  Yeah, right! just like telephone sex is the same as the real thing! 
I’ll get off my soapbox now. 
Phil 

From: swaters via Personal_Submersibles 
Sent: Wednesday, May 14, 2014 7:43 PM 
To: personal_submersibles at psubs.org 
Subject: [PSUBS-MAILIST] Commercial question 

I have always heard that ROV's are cheaper to operate, less risky, and cheaper to buy. I was curious what is the advantages of submarines in the commercial world such as the oil industry? It seems like Phil Nuyten has been able to be sucsessful with submarines. Just a curiousity of mine. 
Thanks, 
Scott Waters 

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