Military recon powerboat concept

[kach22i]

Originally Posted by StianM

I'm not aruing the priniple, but the error is your statement.

Your statement is that the boat float on the aircoushin alone.

More cushion, less pushing.

[jehardiman]

Boys....go look up SES 100A and SES 100B. Both SES's, different concepts, different designs, different support factors.

Today in high speed vessels there are not distinct types, but rather hybrids. Think of a design area shaped like a triangle with hydrofoils at the apex (solely supported by hydrodynamic forces), cats and monohulls at one bottom point (solely supported by hydrostatics), and ACVs and airplanes at the other (solely supported by areodynamics). Most power cats are along line between cats and hydrofoils, ekanroplanes along the line between hydofoils and ACVs. SESs are along the baseline, each design falling somewere between cats and ACVs depending on the distribution of lift at any given time.

[kach22i]

I think if you ignore any critical aspect of the sidewalls when designing a SES you will fail and fail quickly. If we list all the things they do, most will be similar to boats as they come in contact with the water. So you will have drag, just a lot less of it. You will have lift, just a lot less of it.

In principal theory the SES does not derive lift from the sidewalls, in actual application this will vary depending on the designers intent. You can design the sidewalls so they only do their job (of sealing in air) within a very narrow definition or expand it to 15% lift of an "AirCat".

The only error I see is not being open minded to the basic concept of SES design and getting caught up on a few percent which if exists at all may only be intended to aid in getting over "hump speed" and or ballast to help level out the craft with load. The best sidewall designs from what I've read are intended to be as neutral as possible. In addition a useful reserve lift capacity is sought after for heavy weather operation as the drag from waves may pull you down with them, and falling seas can leave part of the sidewall open to the atmosphere allowing vast amounts of lift air to escape rapidly.

Having positive buoyancy in the sidewalls may be a nice thing, but certainly not a basic requirement for operation. You would not want too much lift generated at speed from the sidewalls because if it is not easily controled you could lift out of the water causing rapid cushion loss which would result in plow-in and injury to passengers. It's all about balance and control, each designer and engineer has to deal with the same physical world, they might take different paths to get there. And that is okay with me.

[StianM]

I wouls like to see how your theory boat would do the moment it hit drift wood with sharp edges riping the skirts open.

Would sink like a stone right?

Sound like you try to make a ses boat sound like a howercraft where the side coushins are replaced by fins.

[BTScow]

Alex,
Totally cool - very envious. I would love to be designing craft for the US military - big guns, fast, durable boats, close in support of special forces - what more could a guy ask for.

[kach22i]

Originally Posted by StianM

I wouls like to see how your theory boat would do the moment it hit drift wood with sharp edges riping the skirts open.

Would sink like a stone right?

Sound like you try to make a ses boat sound like a howercraft where the side coushins are replaced by fins.

1. Drift wood is mostly submerged and often smooth out, what makes it so dangerous is that you don't see it until you are on top of it or you hear a loud bang.

2. The bow and stern of a SES or hovercraft skirt most likely would go over such a thing without damage, if torn the fingers can be replaced at base.

3. The sidewalls of an SES hitting driftwood would have the same possibility of damage as a flying boat or boat hull, remember that the sidewalls have much less frontal area.

4. Don't confuse hydrofoils with hovercraft, SES or high speed catmarans.

5. A SES in very simple terms is a hovercraft with side skirts replaced by sidewalls.

6. I have had large long sticks/tree branches sticking out of both finger skirts and bag skirts. I did not even know the stuff was stuck in there until I got on shore and did an inspection. Pull it out, patch the hole and all is good as new.

7. Like many chambered or foam filled boat hulls, most hovercraft can be cut in half and still float.

8. Coming off cushion just puts you in displacement mode (like a boat), I've done this to do some fishing.

Skirt wear:
http://www.hovercraft-museum.org/swift1.html

[kach22i]

Originally Posted by BTScow

Alex,
Totally cool - very envious. I would love to be designing craft for the US military - big guns, fast, durable boats, close in support of special forces - what more could a guy ask for.

Our "Alex" has one post, I think he owes us for pulling our legs on this one.

A quick admission of guilt and all will be forgiven, save the fertilizer for the farm boys.

[Alex Alequin]

Originally Posted by kach22i

Our "Alex" has one post, I think he owes us for pulling our legs on this one.

A quick admission of guilt and all will be forgiven, save the fertilizer for the farm boys.

To be honest, with the holidays and the new year happeneing after my initial post i totally forgot to come back and reply to all your questions. -which by the way i do appreciate all the responses and concerns surrounding this concept.

One thing i feel i do have to make clear though. While working on this project the theme was "protect our borders". this vehicle was designed to be a sitting duck and intercept ie drug trafficers off the coast- immigrants beiing illegally imported and terrorists alike. that was the idea. i was given a layout and options for engines (some more feasible than others) and was also given the freedom to explore any concept that revolved around our theme no matter how wreckless and unfeasible it may seem -hence the sketches posted. those skectches inspired the next phase of concepts and established a direction which go inline with all your concerns about stealth capability.

this boat would most likely be seen off the coast of florida with emphasis on cuban waters in the near future.

it might not make sense as to why anyone would invest in such a project but to be frank theres alote to say for unsecured borders when it come to the water.

anyways, i hope i shed some light onto your concerns i'll post up later in the week about some comments i read that i felt were good concerns. let me just reiterate this last point before i go. when money is no object, and people will do anything to be safe or atleast feel at peace when they go to sleep at night- everything is posible. nothing is unfeasible and theres an answer for everything. i learned that while doing this project.

thats all i can really say without saying everything but when the website goes on i'll be sure and post it.

best reguards;
"alex"

[kach22i]

Originally Posted by Alex Alequin

sitting duck............ those skectches inspired the next phase of concepts and established a direction which go inline with all your concerns about stealth capability.

A ship designed to intimidate all those who dare to pass................just gave me an idea.

http://www.partytimeleisure.co.uk/


.........and it's cheap.

All kidding aside, please post when your are ready.

[Alex Alequin]

ready for what?

[kach22i]

Originally Posted by Alex Alequin

thats all i can really say without saying everything but when the website goes on i'll be sure and post it.

best reguards;
"alex"..........................ready for what?

Your website, post a link to your website when you are ready.

Considering the trooper going on trial for shooting at illegals who tried to run him over, I would consider putting a heat ray on the boat.

US military unveils heat-ray gun
http://news.bbc.co.uk/2/hi/americas/6297149.stm

Called the Active Denial System, it projects an invisible high energy beam that produces a sudden burning feeling.

[safewalrus]

Alex
I like your spelling of "wreckless" you seem to have got it in one!

BT Scow
Designing them for REAL special forces maybe? not border guards! anybodies!

[wellmer]

Hello Alex,

Best way to go stealth on water is to go below surface.

A submarine is completly OFF radar and if you make it quiet it is OFF sonar too - jet turbo whatever - engines are not a great way to stay undetected... so this is what seals are doing right now - aproaching in subs - no need for a stealth surface ship ...


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personal submarine yacht, weekend submarine on mooring


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[arnonrod]

Hi Alex,

have you approached anybody from Defence? They always look for different things that can be of immediate use.

[BMcF]

An interesting place for me to stick my first post. I had a bit do with the KNM Skjold design..and trials..and those of many SES prior to that.

First, the Skjold is not stealthy in 'run away' mode..the GT exhausts are huge and stick right out of the transom. Her stealth characteristics are focused on approaching a potential adversary..the assumption being her anit-ship missiles will make sneaking back away from said target unnecessary.

All SES' built since the late 70s are what are termed 'fat sidehull' designs..in Norway, they even started calling them ACCs - air cushioned catmarans. The very early (most USN prototype models) SES concepts did have very thin sidewalls instead of 'real' hulls and were typically low L/B designs They proved impractical for reasons too numerous to go in to here.

The state of art in current SES designs - Skjold being a prime example, but there are others - is to not exceed a cushion lift fraction in flat calm water of 80%..down to as low as 60% in rough water. With 40% of the vessel supported by its cat hulls, hull hydrodynamics do play a significant role in the seakeeping of the ships. Cushion L/B ratios are also much higher 'nowadays'; the high L/B designs with fat sidehulls were found to have much lower hump drag and better resistance in the region just beyond the drag hump, at the expense of increased resistance in the 'very high' speed regimes that the orignal short L/B boats were intended for (the SES-100B..at 95 tons displacement..still holds, I belive, the record for achieving the highest speed at the displacement of any ship built . 93 knots IIRC.

Skjold spent some time here in the states on demonstrations and USN evaluations (as can be seen in pictures and text on the vessel's web site log) but the USN could not quite figure out what to do with the information that they gleaned from testing her.

Here are a few pics of other SES for your viewing enjoyment..to try and spice up my otherwise boring dissertation

The Swedish Navy's Stealth SES prototype..


The Norwegian SES mine-countermeasure vessels..


A 50-knot 400-pax ferry we designed..built in Korea