sub build underway christmas 2011

Tugboat,

Why don't you just post progress and ignore nay sayers such as myself.

I actually am concerned with you hurting your self and wasting your money and life. But, I am not your grandmother.

You should go ahead as you want. Other visionaries have been called the village idiot before, and still proved they were right (just not all of them).

Trying something is better than corroding away in bed, I agree.

There are people who are trying to help, in their own way. Just take anything valuable you find from the forum. If it is too dismal just withdraw, you don't need our "comment" to proceed on.

Marc

 

yes-thanks Marc- i was trying to locate the 'delete profile" button but i guess this is like the song hotel california--you can go anytime you want but you can never leave...weird..
im going to go now and keep my build up--i made a mistake coming back here...so people know where my youtube link is--sorry to the low bandwidth guys...good luck on other projects--over and out...

 

I worry about your safety.
And it's so big, it could be one of those never-finished dreams real easy for most people.

As long as you don't risk others' lives, I'm with upchurchmr.
It's your life to risk and more power to ya.
Calculate 3x and cut once - you don't get a second chance with what you are working on. Hope you succeed.

 

Your link to http://en.wikipedia.org/wiki/UC3_Nautilus was surprising
58' for $200,000 and only 3 years to build in 2008.
I would never have dreamed that was possible with the cost of everything today.
How many volunteers helped build UC3 Nautilus?

 

OK, just one more lengthy post on this from me, then I'm off, as this is taking too much time. Before I go I just want to illustrate that you really don't seem to understand some fundamental stuff, tugboat, and that you need to go off and do some research on how to tackle some of the issues mentioned. They can be resolved and you can build a submarine of the size and type you want, but you have to understand these issues at the design stage because they have a big impact on the structure and layout.

A submarine has to be trimmed to just about neutral buoyancy when submerged, to minimise power from the high induced drag from the planes that would otherwise arise when trying to give good depth keeping (induced drag is directly proportional to plane lift, either positive or negative). Too buoyant and the planes work too hard to keep the boat down, not buoyant enough and the planes work hard to keep the boat up.

Buoyancy control to maintain close to neutral buoyancy is by blowing air into the ballast tanks to increase it, letting air out of them to decrease it. The ballast tanks are open to the sea on the underside for this to work, but may have rapid "blow" ports on the upper surface for an emergency dive (not really applicable to a civil or amateur boat, though). The volume of air that needs to be quickly moved in and out of the ballast tanks to maintain trim is large, even for a 50ft boat.

When the boat is trimmed to neutral at any depth the ballast tanks will be part filled with air, part filled with water, as needed to give the right trim. If the boat dives from plane action, then the increase in depth will increase the pressure in the ballast tanks and this will compress the air, reducing its volume. When this happens the buoyancy will reduce too, making the boat descend at a faster rate then the planesman intended. Left uncorrected the boat will continue to dive even with no dive plane input, as the increasing pressure compresses the air in the ballast tanks (not that in the hull) and further reduces buoyancy. This rate of descent can exceed the authority of the planes to correct; it’s possible to have full up plane and still be descending due to ballast tank compression. The same happens in reverse when you blow the tanks to surface, with the air expanding and increasing buoyancy as you ascend, causing the ascent to speed up.

The fix is to use depth compensation, where the air pressure in the ballast tanks is adjusted to compensate for any depth change. This isn’t rocket science, but you do need to understand the need for it and design in systems to do it. In principle it needs something like a scuba demand valve that will work both ways, but remember that the rates of air movement from the ballast tanks on even a 50ft boat are going to be pretty large, hence my earlier comment about the sizing of the air bottles and compressor.

An alternative to open ballast tanks using air for buoyancy is the system used on smaller deep diving submersibles, where air compressibility is too big a problem to resolve because of the depth they go to. They often use oil for buoyancy control instead, as it’s virtually incompressible and so doesn’t need depth compensation. Fitting oil filled bladders in the ballast tanks allows water to be displaced cleanly to increase buoyancy as required (and remember you need to have pitch and roll buoyancy control, so need several tanks either side and along the length of the hull). The oil is pumped via valves to a reservoir inside the pressure hull, where the air it displaces has no effect on buoyancy; it just changes the hull interior pressure slightly. The downside with this system is that oil provides a lot less buoyancy for a given volume, so the ballast tanks need to be a lot bigger. This may be an issue when you look at the size of the ballast tanks outside your 50ft boat’s pressure hull. A look at the size of the tanks in the space between the hull and the casing of a typical submarine will give you an idea of the volume they take up.

Edited to add: I just spotted the mention of ballast tanks inside the pressure hull. This removes the problem above, but creates a much bigger engineering challenge, because you now have to build a much larger pressure hull. Generally sub design is about keeping the pressure hull as small as possible, as it is much easier to build a strong small pressure hull than a strong big one. The relationship between size and stiffness is non-linear and stiffness is key to preventing buckling failure. This is the reason that subs stick as much kit out in the space between the pressure hull and the casing as they reasonably can.

Remember that you will still need several ballast tanks to give good pitch and roll trim and that there will still be trim changes that arise from compression, both the small volume change on the pressure hull and the compressibility of stuff outside it. It's easy to imagine that things won't change in volume under pressure, but anyone who has seen an in-water scuba tank test will know that even really strong high pressure tanks change displacement under pressure. You will also need to ensure you have really good ballast tank baffling to prevent unwanted trim change from motion (and there is a fair bit of motion on a small submarine, both on the surface and when submerged in the wave affected zone).




Finally, why not try an experiment to see whether you need air treatment in the volume available in a 50ft long boat? Mock up the size of cabin (it’ll be small on that size boat, I can assure you) and seal yourself inside it for 12 hours. I reckon your respiratory rate will start to increase fairly quickly as your blood pH reacts to the CO2 build up. Within maybe a couple of hours your body will be struggling to get rid of CO2, because the partial pressure of CO2 in your bloodstream will be closer to the increased partial pressure of CO2 in the air in the boat, reducing exchange effectiveness. At the same time, the reduced O2 partial pressure in the air will be causing poorer O2 exchange, so you may start to get slightly hypoxic, the initial effects being similar to having had a drink. The CO2 concentration will increase further, after a few more hours it’ll start to cause you to hyperventilate (you do know that breathing rate is controlled by blood CO2 concentration, don’t you, which is why scrubbing CO2 out is more critical than providing oxygen?). When this happens your blood oxygenation level will rapidly drop, as the fast, shallow, breaths the body needs to try and get rid of the blood excess CO2 build up are less effective at allowing O2 transfer to deoxyhaemoglobin in your lungs. You’ll then start to get seriously hypoxic, not an unpleasant sensation, gently drift into unconsciousness and may be die within another three or four hours if someone doesn’t come and get you out.

 

No fence but or First you have to use compressed gas, in one way or another, and second if you have researched the "stuff" so what did you learn?

 

It imploded because the containing vessel could not stand against the outside pressure.
Oui, mon ami, un peu.

might be right about the ice? Of course I'm right, well nearly so. 1/9 above water, not 1/11. So if 25 feet sticks out of water, 200 feet depth of base.

http://en.wikipedia.org/wiki/Iceberg

"Because the density of pure ice is about 920 kg/m³, and that of sea water about 1025 kg/m³, typically only one-ninth of the volume of an iceberg is above water. The shape of the underwater portion can be difficult to judge by looking at the portion above the surface. This has led to the expression "tip of the iceberg", for a problem or difficulty that is only a small manifestation of a larger problem."

"Icebergs generally range from 1 to 75 metres (3.3 to 246 ft) above sea level and weigh 100,000 to 200,000 metric tons (110,000 to 220,000 short tons). The largest known iceberg in the North Atlantic was 168 metres (551 ft) above sea level, reported by the USCG icebreaker East Wind in 1958, making it the height of a 55-storey building. These icebergs originate from the glaciers of western Greenland, and may have an interior temperature of -15 to -20 °C (5 to -4 °F).[4]"

 

Jeremy,

That was a nice, useful summary of the problem. I hope Tugboat reads it line by line and takes care of the details.

If he is still here.

Marc

 

Jeremy- I trust you realize that this threads contend is a direct reiteration of topics raised during the Welmer concrete sub thread. It a appears Tugboat is a disciple of Welmers approach right down to quoting all of his list "concrete submarine yachting" benefits, construction methodology and the odd design conspiracy angle:

If you followed the prior threads there was hue and cry over Welmers presentation. Not because of a persons participating in a life passion of building a one off sub though.

Welmer was selling his hulls here and elsewhere on the net. He was providing specific performance specifications on the hulls and extensive explanations over how they are used as cruising platforms in the open ocean.
He had no built sub, no testing, no experience cruising the boat etc etc etc.

It drove the professionals here nuts as he was selling his ideals not just building a hull. Many believed that other novices would follow his argument and come to peril.
He continues to lead the movement as it were for concrete submariners and I am assuming the Tugboat has been drawn in by his argument.

Use caution Tug- Marine professionals, NA and engineers work from a body of knowledge developed over many many lifetimes of practical "empirical" experience. Failing to avail yourself to this body of knowledge is unwise me thinks. And declaring that your approach is somehow better than these practitioners is hubris at its worse: "the "Empiricist" school of boat design"

It reminds one of a man standing by the sea holding a thimble full of water.

For those who have interest, Welmer is dragging his creation towards the water:

http://www.youtube.com/watch?v=Acat0PuYemM&context=C3955c5cADOEgsToPDskK-2s5Zp2SUAQNXAPvJhYhP

What had he said about it- "designed and tested to 1200 meters depth"?

 

I like the idea of an escape pod being mounted in the sub but I have doubts about the ability to board said pod within the time available to save one's life.

 

I hadn't read that thread, but have just taken the time to skim through it. The first thing that hit me were a bunch of inconsistencies and errors, like the statement that the 20 tonne boat contained 20 m³ of air (ignoring the fact that 20 tonnes of concrete would take up around 8.5 m³). The second was that I couldn't see how structural integrity could be assured when using an essentially prototype construction method using a composite material with no simple way of checking for flaws, voids, stress raisers etc after construction.

Unless I missed it, it seems that the concrete boats mentioned relied wholly on static trim. I couldn't see any planes. That, and the mention of 200 litres reserve buoyancy being OK for a 20 tonne boat and all the other errors convinced me that the guy hadn't even done any rudimentary homework.

 

http://www.youtube.com/watch?v=hVJGtU8dGMk&feature=endscreen&NR=1

Here's a way of getting most of the benefits of a submarine without most of the hazards.

 

Given that professional submarine builders see no sense in making the outer hull the pressure hull, I see no sense in amateur builders doing just the opposite.

 

I would highly recommend that all do-it-yourself submariners read and absorb the comments of Jeremy Harris and get a copy of Modern Ship Design (by Thomas Gillmer) which touches on the critical design issues discussed by Jeremy.

Then download and figure out the implications of these Rules for Building and Classing Underwater Vehicles. I think almost every underwater vehicle built in the USA is classed by ABS. As a start your sub needs to meet or exceed these rules..... http://www.eagle.org/eagleExternalPortalWEB/ShowProperty/BEA%20Repository/Rules&Guides/Current/7_UWVS_2012/guide

 

It only takes one hazard.