Torpedo hull

[Hondaen]

Hello

I`m a electro engineer, but i`m facinated of marine designs.

Can a marine engineer give me som input/comments? I have toughts of some hull designs, but I lack the knowhow to predict if they have a "life" or not:

1. Torpedo hull design.

Two "torpedos" with propulsion are located 1 meter below water surface. They travel leveled with automatic boyancy systems.

Each of the torpedos have two struts holding up a frame, so persons can ride on the "boat". With this design, waves are minimalized. Will this design give us fast and econimic hulls?

2. "Ski" design.

Two long skiis are mounted at each side of a boat. They are twice the length of the boat, maybe longer. Main goal is so rice the boat from the sea and make a vessel that plan. Scnd goal is to lengthen the boat, so it can travel faster in heavy sea, as it "cuts" the amplitudes of the waves.

Ok, sorry my bad english, but what do guys think?

[timothy22]

#1 seems to be an excellent idea.
http://en.wikipedia.org/wiki/Small_W...Area_Twin_Hull

Don't know about #2

[messabout]

One of your Universities, in Norway, has an acknowledged school of naval architecture. One of the teachers is famous for his books, and particularly for vessels of unconventional design. The author is Odd Faltinsen. Perhaps you could contact that college for advice or counsel. ( I hope I spelled his name correctly)

[PAR]

It's much more efficient to skip across the water's surface then bore through under it. Early submarines, where power resources were quite limited, understood this particular trait, doing as much of their passage making on the surface as possible, where they could travel at 2 to 3 times their submersed speed.

The second concept has obvious issues, like docking, boarding and exiting, "tripping", having one "ski" out of phase, strength/weight limitations from a cantilevered set of ski supports, etc.

Hydrofoils are a way of getting the boat out of the water, above the harshness of existing sea conditions and dramatically increasing efficiency. Unfortunately, just like most else in yacht design, they have a negative side to weigh against the other compromises in convoluted concession that eventually develop into a design.

[marshmat]

It's much more efficient to skip across the water's surface then bore through under it. Early submarines, where power resources were quite limited, understood this particular trait, doing as much of their passage making on the surface as possible, where they could travel at 2 to 3 times their submersed speed.

True, to a point.... those early submarines, though, had hulls shaped like those of surface craft, with the ability to submerge being secondary. Since they had to run the diesels to get any kind of range, and so little power was available in electric mode, it was best to design them to run on the surface except when attacking.

Now, the US and Russian navies still refuse to say exactly how fast their nuclear subs can go, or how deep. But it seems to be generally accepted that they're the fastest boats of their size in the fleet, by a fair margin. The catch- they can only go fast when they're submerged, and the surface wave system taken out of the equation. On the surface they suck, but in their natural environment, subs can be shaped for remarkably low drag and no longer have the speed constraints imposed by dragging along a surface wave larger than your ship.

1. Torpedo hull design.
Two "torpedos" with propulsion are located 1 meter below water surface. They travel leveled with automatic boyancy systems.

SWATH, the rather awkward name for this type of hull, is a setup seen now and then for special purpose applications. Our Coasties use them for charting, among other things- with very small waterplane area, they're not very susceptible to wave action and so you get a very stable platform to work from. Unfortunately, it's hard to get the hulls deep enough to get rid of the drag-creating surface wake system, without also introducing excessive draught (thus lots of groundings), limited load carrying ability (because of the small waterplane) and structural complications (many SWATH ships have suffered fatigue damage in the strut-bridgedeck joint because of the enormous moment arm being applied on a very narrow strut). So the stability gains are real, the possible efficiency gains still a pipe dream.

2. "Ski" design.
Two long skiis are mounted at each side of a boat. They are twice the length of the boat, maybe longer. Main goal is so rice the boat from the sea and make a vessel that plan. Scnd goal is to lengthen the boat, so it can travel faster in heavy sea, as it "cuts" the amplitudes of the waves.

So, sort of like a wave-piercing trimaran, with very long, slender amas? That could work..... reminds me a little of the BMW/Oracle America's Cup trimaran, although that thing is designed more to carry a flippin' huge sail than to be comfortable. Make them planing hulls.... that could cause some issues with ride harshness, and I'd question whether that would be the way to go. Since you're already talking long and thin, sticking to displacement mode might give a smoother ride without much of a drag penalty. The annoying and destructive dynamic instabilities PAR mentions would have to be very carefully analyzed. (And I'd hate to see the marina bill for docking the thing.) But it might be neat to see it tried.

[Guest625101138]

Originally Posted by Hondaen

Hello

I`m a electro engineer, but i`m facinated of marine designs.

Can a marine engineer give me som input/comments? I have toughts of some hull designs, but I lack the knowhow to predict if they have a "life" or not:

1. Torpedo hull design.

Two "torpedos" with propulsion are located 1 meter below water surface. They travel leveled with automatic boyancy systems.

Each of the torpedos have two struts holding up a frame, so persons can ride on the "boat". With this design, waves are minimalized. Will this design give us fast and econimic hulls?

2. "Ski" design.

Two long skiis are mounted at each side of a boat. They are twice the length of the boat, maybe longer. Main goal is so rice the boat from the sea and make a vessel that plan. Scnd goal is to lengthen the boat, so it can travel faster in heavy sea, as it "cuts" the amplitudes of the waves.

Ok, sorry my bad english, but what do guys think?

You need to decide what you want to do with the boat. Existing boats look the way they do for practical reasons.

SWATH type craft will outperform other displacement craft providing the hulls are deep enough. Typically about 3 diameters deep. The optimium shape has a slenderness ratio of 8.

I built the boat pictured to test viability. The big issue is static stability. The pictured boat was pedal powered and even with the widely spread outriggers it took me over an hour to work out how to mount it. The buoyant "submerged" hull has a powerful tendency to want to get to the surface. If I accelerated at even moderate rate the front outrigger would rise over 2m high until the from of the "submerged" hull was at water level.

The boat did ride like it was on a cushion of air, totally immune to any waves up to 0.4m high.

I learnt about the need for three diameters after it did not perform as I expected and made quite large waves. The main hull was less than 1D below the surface. If it was set any lower I would have needed to wade neck deep to mount it and then try to climb up in some way.

So as Matt points out the concept is sound but there are many issues to resolve satisfactorily. If you google SWATH you can get ideas.

Rick

[Hondaen]

Hello

Thank you for all replys. They where all very informative.

Rick: Very interesting project you have. Wish I could have seen it in real life and tryed it myself.

I guessed that it would be a big problem with boyancy. However, I had this idea using electronic microcontrolles to controll the up/down movement of a vessel, by the use of servos and mini fins.

You get powerfull calculation in a very little package, full PID regulation is possible for cheap. Offcourse it is hard to develop and fabricate if you are unfamiliar with theese things, but mayebe it would have worked.

Thanks

[Shore_Fisher]

I am looking for a small, transportable, near-shore, fishing boat design. To fit my requirements (2 people, side-by-side fishing, camp on-board) I need a very beamy conventional design that just gets too big to be easily transportable. I'm not interested in high speed, but want the best efficiency I can get.

I was thinking that this type of 'twin torpedo' design, with a flat, 'party boat' style deck well off of the surface may be good for me. If I could design the hulls and sponsons (?-The bits that break the surface and connect the hulls to the deck) in some removable fashion, I may even be able to get a 'car-topper'.

I was wondering whether it is possible to use pumpable water ballast in the submerged hulls to adjust hull depth on the fly. Empty and above the surface for launch/shallow running, and well down under the surface for 'cruise'. I am assuming that this would require the sponson buoyancy to be substantial enough to affect overall buoyancy, but would this size of sponson just negate any benefits of the submerged hulls?

I was also thinking that a height-adjustable deck-to-sponson connection could allow adjustment to accomodate different wave heights and fishing down close to the water.

What does anyone think?

[Guest625101138]

Efficiency and added ballast are inconsistent. The most efficient boat will be the lightest you can make within a given size envelope.

Eliminating reserve buoyancy in the hulls with ballast will make it very sensitive to load shifts. It will have tendency to roll and pitch in the extreme by small movements on the deck.

You also need to set a speed range as your definition of high speed may be different to others.

The most efficient submerged buoyancy is achieved with a single hull having slenderness ratio of 8 and sitting at least 3 diameters below the surface. This can result in intolerable draft. Going to two submerged hulls negates the efficiency benefit. Twin hulls are used to improve ride quality on larger SWATH craft but does not do anything for efficiency.

Rick W

[BMcF]

Originally Posted by Hondaen

Hello


I guessed that it would be a big problem with boyancy. However, I had this idea using electronic microcontrolles to controll the up/down movement of a vessel, by the use of servos and mini fins.

You get powerfull calculation in a very little package, full PID regulation is possible for cheap. Offcourse it is hard to develop and fabricate if you are unfamiliar with theese things, but mayebe it would have worked.

Thanks

In fact, active micro-processor-based control of pitch, roll and (often) heave is a characterstic feature of all of the most successful SWATH ever built (successful in terms of maximum stability and minimum motions). Nearly all use two forward control fins (canards) and two aft control fins (stablizers).

So your idea has obvious merit..since you basically 'thunk up' what is a very accurate description of many SWATH in service today.

[jehardiman]

1) SSP Kaimalino, circa 1968



2) HYSWAS Quest, circa 1975



or RV Triton, circa 2005

[Guest625101138]

John
The reference to Quest is appreciated. This boat is a larger version of what I hoped to achieve. This video shows it in operation:
http://www.youtube.com/watch?v=kRuUtOmMGR0

The initial part with the pedal powered boats show similar problems to what I experienced.

The submerged section is very similar to my submerged section and is probably the optimum for fully submerged operation. In flight it seems closer than 3 diameters to the surface so would make some waves.

My idea was to use the wide set outriggers on foils to provide good inherent static and dynamic stability so I did not need to go to dynamic control surfaces. This aspect was discussed after my initial experience but it adds complexity and more wetted surface.

The main issue for me was the draft but the idea has merit if the load does not change much and there are deep berths and moorings available.

The ride quality is outstanding compared with any other craft with maybe exception of full foil. Also the single hull used on Quest would be more efficient than any other displacement craft. The advantage over foils is that you have something solid and streamline in all planes under the water although it would not have much propensity to climb over solids obstructions.

Rick W

[BMcF]

"2) HYSWAS Quest, circa 1975" uh..make that about 1995, at least. The young engineer on the deck, Danny J., was barely in to high school yet in 1975.

[jehardiman]

Originally Posted by BMcF

"2) HYSWAS Quest, circa 1975" uh..make that about 1995, at least. The young engineer on the deck, Danny J., was barely in to high school yet in 1975.

I have no idea when that picture was taken, or even when Quest was built, I guessed the mid to late 70's, but the HYSWAS concept pre-dates my Senior Design Study ('83-84) as I went through most of the David Taylor data on HYSWAS and SWATHs from the '60's and'70's at that time. The TAGOS-19 (ordered 1986) class is basicly identical to my design study SWATH because thats what the data converges to. My advisor decided that a nuc sub based HYSWAS was a little out there for a design study.

Edit; OK, Googled it up, earliest HYSWAS paper I could find was 1976 (which seems about right), Quest was built in '98.

[BMcF]

Originally Posted by jehardiman

I have no idea when that picture was taken, or even when Quest was built, I guessed the mid to late 70's, but the HYSWAS concept pre-dates my Senior Design Study ('83-84) as I went through most of the David Taylor data on HYSWAS and SWATHs from the '60's and'70's at that time. The TAGOS-19 (ordered 1986) class is basicly identical to my design study SWATH because thats what the data converges to. My advisor decided that a nuc sub based HYSWAS was a little out there for a design study.

Edit; OK, Googled it up, earliest HYSWAS paper I could find was 1976 (which seems about right), Quest was built in '98.

Good stuff. I've worked with the DTRC guys who pulled off the original Kaimalino project. In fact, that was where the first active control system development came from...what we still base ours on today.

HYSWAS was the gleam in the eye of one John Meyer for a very long time before he finally got that demonstrator funded (John believes that everything should have foil lift and done right, never any hull left in the water. ) The young fellow in the deck in that pic cut his teeth working with me on SWATH and SES controls before moving on to tackle the HYSWAS control problem with MAPC. They did a fabulous job on the craft.