Concrete submarine

[wellmer]

Originally Posted by bntii

Thanks Wil,

Cruising and being immune to waves in storm conditions is very impressive. Do you believe that the hull was exposed in the wave trough during this storm?

Thanks again

While snorkeling the sail of the prototype was barley below surface - so i suppose part of the hull was in turbulent zone.



I also experienced stroms on anchor place. (See photo) And i would not even have to put the coffee cup away when on surface.



(still no sail)

But this seems to be specific for my designs due to the rounded upper hull - little deck superstructure and the deep ballast center - i have reports from other submarines that movements on surface (in their case) tend to be unpleasant.

Cheers,
Wil

[Boston]

you guys do realize how much debris is out floating round in our precious oceans dont you

I would think that snorkle would catch a lot of abandoned gear

[bntii]

Originally Posted by wellmer

I had snorkel trips at less then 1m depth and when i came up i found that a severe storm had come up and several sailing yachts (of the ocean crossing type) where calling SOS.

While snorkeling the sail of the prototype was barley below surface - so i suppose part of the hull was in turbulent zone.
But this seems to be specific for my designs due to the rounded upper hull - little deck superstructure and the deep ballast center - i have reports from other submarines that movements on surface (in their case) tend to be unpleasant.

Cheers,
Wil

Thanks Wil,

This may have had something to do with the other submarines operating in wave heights of greater than 1 meter? I would be interested in testing done with the prototype in open ocean with mean wave heights of between 2 and 4 meters. I think these conditions should be considered to be common enough and do not represent storms. I believe that axial movement will prove to be a very real issue which will have to be addressed.

Thanks again

[wellmer]

Originally Posted by bntii

Thanks Wil,

...wave heights of greater than 1 meter...
Thanks again

Do you suggest when i speak of storm conditions and SOS calling i am talking of wave height of 1m ?!

I am malpelo diver - ( http://imulead.com/tolimared/malpelo/page3.htm ) so i am quite familiar with wave conditions in open pacific - and therefore can assure you that storms on my prototype test site ARE severe

[MikeJohns]

I cannot be very specific without more information on your design, you may have considered all but your reasoning rings a few alarm bells....at least in my head.

Originally Posted by wellmer

- i give you that TROLL A is not exactly the same load case - it is a much more severe load case including bending cycles and vibration…………….............. a bridge foundation is taking a pressure load cycle every few seconds - so it will take the number of load cycles that you have to expect in a sub hull - in less than a few hours......

Perhaps you'd like to put some numbers to the RELATIVE cyclic stresses from forces NORMAL to the surface there really is no comparison with these examples that you quote.

You also need to look closely at the stress flow in the structure. It is the stress hotspots that fail first, the indeterminate factors- unexpected stress concentrations due to items like cutouts and bulkheads-hull interfaces.

You should at least model your designs in an FEA package. If you haven't then you are flying blind as the FEA is an excellent design tool in this area.
You can email me your hull cad model and I'll show you the stress concentrations if you like.


Your argument and observations are valid for shallow dives but there will be some serious stresses from deeper dives.

I don't have your hull specifications and details as I would dearly like to give some numbers here.

Originally Posted by wellmer

.........i would not expect fatigue in a sub hull before some centuries of use - i honestly think your idea of failure by fatigue by dive cycles is out of proportion some serious orders of magnitude...

This is my concern, if you are basing this view on observations of static pressure structures , it is the magnitude of the cycled load and the number of those cycles.

we calculate our expectations and add safety factor for indeterminacy. History is full of unexpected failures, with each we analyze learn and then teach the reason for that failure.

Originally Posted by wellmer

I also think that the reason for the studies design with the concrete spheres that obviously skips completely your postulated "cycle problem" is just due to the fact that there is no "cycle problem"
Will

Fatigue testing is done quite differently and has been comprehensively studied and the information is out there. This was about high pressure static load long term durability of the material . The spheres are not fatigued with one cycle (Pity nobody proof read their synopsis (they meant permeability)

Originally Posted by wellmer

In general i am a friend of treating a sub hull like a scuba tank - check it every couple of months with a testdive that gives you at least a safety factor of 1:3 - expect the unexpected test it frequentlly

That's one way of doing it . Check it after a combination of dive frequency and depth.

Anyway I'll leave the hull there for the moment.

To operate over a seafloor that is below crush depth you need an emergency ballast release or some other means of emergency flotation. I'm wondering if you have tackled the volume reduction with depth of your hull? Vertical sinking velocity and time till you cannot blow your ballast tanks. Many small subs have crashed to the bottom because they had ballast tank operation problems. The hull loses buoyancy continually with depth and this can turn into an uncontrolled and surprisingly rapid dive. Emergency solid ballast jettisoning is a very desirable safety feature.

Do you have any idea of the Youngs modulus of the matrix you are using? It will be somewhere between 70 and 100 GPa presumably .

Talking about waves, the ocean swell is going to generate heave on the submerged vessel and it will be continually rising and falling lagging the surface contour, so it may not be as smooth a ride in the ocean as in your lake.

Some other concerns:
I would be very concerned about collision with shipping.
If you tow a snorkel and surface pod the drag is going to be very detrimental.

[wellmer]

Originally Posted by MikeJohns

... alarm bells....in my head...

It is one of the annoying things about submarine discussions that the discussion forums quickly fill with "phobic questions" submarine yachting shares this phenomena with, snakes, spiders, flight fear, etc... some typical of those are: what are you doing when you sink like a stone in groundless deep ocean after a super tanker collission, with oxigen running out, and all this catastrophic "technical problems" set in ???

The truth is for a phobic person - things will never be safe enough, tested enough, studied enough...

The reasonable thing to do is keep all safety issues inside the safety factors that are of common use in other fields of engineering where life depends on it.

Similar to airline industry i have no big interest in doing large scale discussions about "phobic questions".

The good thing about submarine yachting is you can adress real issues by TEST things out. This is something you can not do for example about earthquake resistance in buildings.

Whatever your concern is a 1:3 test with the finished boat can give you peace of mind - if this is not the case you are probably boderline phobic and submarine yachting is not your sport.

[wellmer]

Originally Posted by MikeJohns

... Emergency solid ballast ...

I like solid ballast due to its independence of dive depth - on the other hand for a boat concept that is designed to stay decades in the water a reliable mechanical release mechanism is a problem. - i like a blow out solution similar to military subs due to its lack of vital mechanical parts - a lot of different emergency systems exist, private submarine projects have great variety working - see some at (psubs.org)

[wellmer]

Originally Posted by MikeJohns

Talking about waves, .... so it may not be as smooth a ride in the ocean as in your lake...

I have quite a good experience base to compare wave conditions in open pacific and on the prototype test site. I am confident that the hull size and wavelength on the prototype test site is a very exact model for the 18m boat in ocean conditions. In any case i will find out and test out this soon. I expect "leave coffee cup on table" cruising in storm conditions.

[ancient kayaker]

There's a certain amount of repetitiveness in the questions that appear in threads related to submarines. I am not referring to the previous thread, but to some of the earlier ones. Wellmer seems remarkably patient but he is reaching his limits, not surprising.

It is true that some threads get pretty unwieldy, however, I do try to skim through all the posts in a thread before posting questions, and the thread search tool, although flawed, is still a good resource. I think it would be a good thing for all of us interested in this fascinating topic if we try not to overload this thread, so the remaining serious issues can be explored more readily.

[bntii]

Thanks for the information Wil

[wellmer]

i got a lot of "flaming" on the "decorative item shop" from jon at psubs.org - so i do not really want to repeat this here... the underlying argument ist : safety comes not from stamping by any kind of organisation - safety comes from solid over dimension, solid security factors in dive depth, solid testing, solid knowledge about what you are doing. - the comment was for Ian Roxborough - AFTER he had read the thousand plus pages about of stachiw about acrylic view ports in submarines - so it should not be necessarily seen as a "beginners guide to submarine view ports" but left as it was intended a "spicy comment under experts" to heat up the discussion. What you safe on stamping will give you a budget for : Buying Jerry D. Stachiw´s book to get informed, double the thickness of your view ports to increase safety factors, buy a high tech autoclave for annealing just in case it was not done right, and run your own personal test series with the viewports included mountings - which would result in a general safety increase - compared to a stamp - anyhow i hope you understand that i will not publish here something like a "ACME guide to cheaper submarine view ports"...

[ancient kayaker]

Agreed on the stamp. It reminded me of old times.

I formerly worked with a Space engineering company, and the only failure we had with our product was caused by a connector, supplied by NASA, duly stamped and accompanied by reams of certificates. But it failed in orbit. Turned out the inspection process was non-existent, just paper work. But because it was from NASA it did not go through our own rigorous qualification and inspection process. That predated the Challenger and Columbia disasters.

Before working in Aerospace I worked for many years with companies that did business with the military. It was axiomatic that you could, and still can get far better product at a fraction of the price by buying non-military approved items. One of my first experiences was with a massive piece of electronic wizardry of a design so old that it used thermionic tubes (valves to Brits and their ilk). The commercial units worked fine but out of date and being replaced by transistorised ones. By the time the design worked it's way through the military approval process it was a real challenge to build it to the drawings provided, and when we did it would not work at all well. Having got the military-introduced bugs out of it we replaced all the tubes with commercial ones. finally, it met its specifications. When we replaced the tubes with military hardened and approved ones supposedly with identical specs, we had to replace them one at a time (over 100) and retest after each time, changing the tubes until it worked again. Took over a month. Then we demonstrated it to the customer and got paid. I visited the installation site a month or two after it had entered service: the first thing the operators had done was replace most of the tubes with commercial ones bought from the local radio shop. But the paper trail was impeccable.

[Jimbo1490]

I have a friend and business partner that worked in QC locally for NASA out at KSC. He told the tale of how many items that QC certified and stamped and then bagged and stored away would fail prematurely upon retrieval from stores and inststallation. He found that they were using a certain tape to attach tags (QC decals, really) to the items before bagging for storage. The glue in these decals degraded with time (of course) and caused various problems some obvious (fowling with sticky glue) some less obvious (vapors from the volatile components of the glue degrading wire insulation and seal compounds). The simple solution was to stop using stickers/decals of any kind for ID and QC purposes. This took many months to implement. So much for the 'stamp'.

Jimbo

[MikeJohns]

Originally Posted by wellmer

...............
Similar to airline industry i have no big interest in doing large scale discussions about "phobic questions". ….……….
Whatever your concern is a 1:3 test with the finished boat can give you peace of mind - if this is not the case you are probably boderline phobic and submarine yachting is not your sport.

Wilfreid
As I said …..“In my head” in other-words maybe it’s just my problem. But I’m an engineer so bear with me.

But I think that what you call phobic questions of mine, are actually very reasonable and deserve a reply. You also have the possibility of improving your design with sensible discourse.

This is partly my field of expertise and it seems plausible from your posts that you have some concerning gaps in your knowledge. It appears that your approach is not so much an engineering approach as one of building and trial. That may be a valid up to a point. However if you are then unaware of some of the pitfalls and refuse to consider significant safety issues because you believe them paranoid then you have a very serious problem.

If you are just tired of covering the same material then please just give me a link to where you addressed it before.

Any engineer would expect to be asked these sorts of questions in any peer discussion and at a very pre-cursory level without taking umbrage. You are the engineer of this proposed vessel and you could respond with your consideration of the issues addressed with clarity and sensible intelligence. You are posting on a boat design forum in a design discussion thread. What do you expect ?

None of the questions I was posing are anything other than practical and I really wanted to see how well you had considered them. Apparently you haven’t.

So facts not phobias, and one very simple scenario that any subersible opearator is trained for.

Consider an uncontrolled descent due to water density vertical currents , accidental over ballasting … whatever. Then take the available volume pressure and rate of compressed air for ballast ejection , also calculate your elastic loss of buoyancy with depth. You need to be able to gain buoyancy at a rate faster than you are losing it. At a certain depth you lose this ability. This is very real and has lead to the loss of many small submersibles over the last 60 years and many deaths.

So I am very curious and not at all phobic. Have you considered what this depth is , what methods have you available to vent the ballast water ? How much energy will it take to pump air if your compressed air tanks have failed? What are the rates and pressures of the pump? Small subs are very limited in the gear they can carry and the redundancy they can afford. However of all the systems aboard the ability to emergency surface is number one.

As for long term reliable release of fixed ballast : I’ll propose that there should be at at least 2 ways of dropping it. For outright simplicity perhaps One automatic hydrostatic device and one through hull rotating shaft. For the rotating shaft you need to work out the shaft torsion required to overcome the seal friction at depth.
The hydrostatic device can be something as simple as a single use collapsing diaphragm pulling a pin on a pelican hook. Made of copper nickel it could last longer than your hull and be non fouling…just a thought..

[ancient kayaker]

Originally Posted by Jimbo1490

I have a friend and business partner that worked in QC locally for NASA out at KSC. He told the tale of how many items that QC certified and stamped and then bagged and stored away would fail prematurely upon retrieval from stores and inststallation. He found that they were using a certain tape to attach tags (QC decals, really) to the items before bagging for storage. The glue in these decals degraded with time (of course) and caused various problems some obvious (fowling with sticky glue) some less obvious (vapors from the volatile components of the glue degrading wire insulation and seal compounds). The simple solution was to stop using stickers/decals of any kind for ID and QC purposes. This took many months to implement. So much for the 'stamp'.

Jimbo

I often wondered why my former employees and some of their customers banned decals outright. now I know. A bit off-topic though.