Rick,
I concur with Paul, great stuff thanks a lot. Things are progressing nicely on the learning curve and my design is showing it, thanks to all.
That term "total floodable interior space" came from the NAVPERS manual and I assumed that it is used in part to help determine soft tank volume during the design process.
I am discovering the specific gravity problem you mentioned. At this point it is becoming necessary to determine the total mass of all structures external to the crew compartment. Less is better, more density is better but you still need to maintain shape and structural integrity. This is like trying to design a submarine out of styrofoam dixie cups, it's a problem....lead is what now, 708 lbs per cubic foot?
The issue of trim aside from dynamic stability of the planes in my particular design, still needs work, this boat is going to be limited by design, to 33' by the limited air supply but she will be able to travel at periscope depth on the diesel for 10 hours. (Any leads on snorkel system designs from anybody is greatly appreciated).
Ah yes the appearance of the lines affliction! It sure would be easier to dispense with the lower free flooding spaces on my design altogether but she just wouldn't look right!
Thanks
Joe
From: Paul Kreemer <paulkreemer@gmail.com>
Reply-To: personal_submersibles@psubs.org
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Re: Working Schematic, specifications
Date: Fri, 25 Nov 2005 09:59:08 -0800
great note Rick. thanks for the explanations and news on your project.
On 11/24/05, Rick and Marcia <empiricus@telus.net> wrote:Hi, Joe . . .If I am understanding what I have learned sofar "floodable interior space" is the total displacement of the air volume that you are trying to submerge.I've never heard that particular term before. Itseems contradictory. Rather than complicate things by establishing nomenclature [just for the moment] I'll refer to the interior dry volume (cabin) as the bubble I have to force underwater.A dry cockpit volume of 4 x 4 x 4 will yield 64 cubic ft.or 4100 lb. of buoyancy. Weight includes two occupants at 150 lb. ea. Also include the seats, instruments, dash panels, batteries, controls, a good book [Busby - at least 35 lb.], a packed lunch with thermos and a sleeping bag and misc. other items. Obviously, if you have 4100 lb. of keel ballast in the form of, say, lead, you're going to the bottom fast. Let's put less lead in the amount of all that cargo we mentioned above.Lead + cargo = cockpit bubble. That'sit.All other materials, say, ply hull,fibreglass/resin, motors, deck fittings, anchor/chain/rope, skeg, etc. that will be fully immersed will have an amount of buoyancy depending on their particular specific gravitThis is the difference between dry weightand what would be required to submerge to neutral buoyancy. Quite frankly, I am having trouble determining how to look at it, whether soft water ballast is "increasing" weight or "decreasing" displacement or perhaps both?"Soft tanks" are upside down glasses that you fill withair at the surface to lift the boat higher out of the water. Open at the bottom like a glass. Very little inherent pressure internally. No reason to have much pressure. They still have to be sturdy.That figure above is roughly the 30% ratioto interior volume for a seagoing boat as Carsten had pointed out. He had also pointed out that high volume soft ballast ratios are not unheard of as in this example so I am still playing with the idea.Take a look at your own boat. Everything other thanyour dry cockpit/cabin will be wet. Those areas will be flooded 100%. No mystery. Your hull is for streamlining and lifting your boat out of the water while surface running.Where the confusion may be arising is in the hardtank[s]. At the surface, having lots of hull space to force air into will lift your boat up high. Those are the soft tanks.The hard tank [as in "hard-walled" to resist waterpressure] is used to fine-tune your neutral buoyancy. It is NOT open at the bottom - it's sealed against pressure. Ideally, if this sealed box is full of air, the sub will not dive - it's too light. Your cockpit canopy will be awash. If this box is filled 100% with seawater, your boat will be too heavy - it will sink.During normal use, if the usual occupants' weight isknown, the weight of Busby's book is known, your cell phone, note pad, video camera, box lunch and pina colada thermos are all known weights, THEN you can remove lead to the point where your hard tank will be filled about half way to achieve neutral buoyancy.Until then, using these known weights, your canopy willforever more be doomed to be awash until that hard tank is filled half way with sea water.So why is it hard? To keep Boyle's Law out of yourhair. An open [soft] tank will accomplish the same thing as a hard tank - for the first few feet of depth. Once the air starts to compress, you'll face every diver's dilemma - keeping neutral buoyancy.A hard tank will isolate the ocean pressure from thecontents and the air in this hard tanks will not contract.A company called Dacor designed a hard tank scuba pack[back in the eighties, I believe] to get around Boyle. It wasn't a success. Apparently the pack wasn't strong enough to last through to full scuba depths and you had to release pressure mid-dive. Not easy to control. Now, if you build one out of Al2. There's thought.If you want to maintain some degree of scalein a replica you run into these volume and length problems. What have you worked out for your Typhoon replica "Magical Child?"Hardy-har. Finally someone else with the samedilemma!!! These subs were designed around using the entire interior as dry volume.Your particular affliction - and mine - is to maintain thesame degree of "look" or authenticity as the original. It wouldn't look cool if the lines weren't right. You, I suspect, have an artsy streak running through you. I'd be willing to bet you'd never be happy with anything but an Italian motorcycle [damn the electrics]. http://www.motoguzzi-us.com/bikes/v11lemans/index.html Soo-weet.[origin of the name Magical Child: http://www.thewellspring.com/cat/adult_books/magical_child.html] For Magical Child, I've had to compromise between authenticity [the cool factor] and the length of my workshop. I truncated Magical Child until I could squeeze it into my 18 foot shop. A 15 X 2.5 ft. [NOT the original Typhoon L/B ratio] hull allows tandem seating [not my first choice] and a 6:1 ratio. Not bad. It'll flow smoothly on the surface, offer a large deck area for movement, lounging, etc., will be fairly kind in a seaway [no thanks to its bows], will be hydrodynamic underwater, and will keep the props in the water during heavy seas.It'll also be aesthetically pleasing.Dans words keep ringing in my ears thoughand I believe it was you who suggested a "proof of concept" boat. I am seriously looking at downsizing even further to a two man craft or smaller.I'd like to share the u/w world with mykids, hence the two seater. Think "kayak" around a cockpit. See this link. http://www.psubs.org/pic/wet.html#sleepingbeauty It's a wet boat - pic contributed by someone back in the '90's. ;-)Put a canopy on it, compensate the cabin and Bob's youruncle. Proof-of-concept still has to be fun. I have not the resources to do this solely as an intellectual exercise (hmmm . . . that didn't come out right). It HAS to be fun as soon as the thing hits the water.The S-boats at 219' by 20.6' could be scaledto roughly 1/10 and come to about 22' x 3'. A single cylinder diesel/electric would be damn cute!A different L/B ratio would simply make a fatterboat. Decent lines could still be maintained. I enjoy inserting a jpg of a sub drawing into Word, then using the image markers to expand or contract the image as I see fit. Hold a ruler up to the screen or use Word's built in rulers and you can get INSTANT visual results with ratio changes.Do it with both the elevation and plan views. It's ascream. BTW, if the technique appeals to you, mess with the sectional views, too. Print out a copy of the proportions you like, white-out the yucky parts, draw in your own canopy design, scan it back in to the puter, then play with THAT jpg in Word.A word on modeling: I've bought several well proportionedhuman figures so I could work with them during the modeling sessions. This link shows one of my human figures. Obviously, the gentleman in the picture is not in proportion to the hull he's sitting in. It was for roughing out. I've since bought three more Typhoon hulls of different scales to play with as well as several other human figurines/dolls.The Magical Child model I'll be building willbe thirty inches long because the figure I've chosen is twelve inches tall. His arms, legs and torso all bend at the right place and are anatomically well proportioned (my smart-ass 13 year old daughter, looking over my shoulder, wants to know if he has a penis) Same boat building techniques as the final build: glass-over-ply.Warm regards,RickVancouver