Comments on: The Bat Boat

By: Walter Schwall IV

Walter Schwall IV — Wed, 09 Jan 2008 14:20:50 +0000

I bet i put a hole in it. It seems to me that we sacrafice defense for speed and firepower for stealth. Mabye just mabye we need to create and develop a new material that is flexiable, moluible, and super dense/strong. mabye its just me.

By: bracecast

bracecast — Tue, 03 Jul 2007 06:16:18 +0000

I am in the orthopedics industry and am looking for information on a composite of titanium,carbon ‚and kevlar for making lightweight and extremely durable braces for patients who need them .the current technology uses polyeth or leather for containment and stainless steel for support,depending on the size of the supported limb these can weigh anywhere from 2.0 Kg to 7Kg,and in the higher weights they also require more effort to ambulate ‚a tough order for a person trying to recover from a traumatic event

By: Lee Wahler

Lee Wahler — Thu, 29 Mar 2007 08:30:27 +0000

Where’s the beef? Or in the case of the Stiletto, where is the actual sea trials data. I have yet to see anything posted showing this craft peforms in the way is it is being hyped AT SEA!
Sure the SEALs need a sea boat like this for insertion, but it must be able to operate effectively in the marine environment. Go fast and be steathly is NOT reason enough to buy more of these, yet some congress types want to throw money at M-Ship, why?

By: Vstress

Vstress — Mon, 12 Mar 2007 17:55:11 +0000

Yeah, I agree, the person misunderstood the term modulus of elasticity and interpreted it as stiffness — don’t worry, I still did it in university, didn’t quite get it till I started working ; )
Moisture absorption was a question I was interested in as carbon fibre naturally absorbs moisture (at least epoxy-carbon fibre composites). In manufacturing specs it has to have a limit to how much moisture it naturally absorbs.
Just intrigued as aircraft have this problem… clearly a boat would be even more vulnerable.
Also… corrosion resistance is very good, yes!
But… you put metal into the equation (ie. a metal bracket that is bonded, or bolted to the composite) and it exacerbates any corrosion on the metal, due to the carbon fibre composites ability to retain water.
It is a major problem in aerospace again… therefore I presume even more so with boats.
Then again, maybe they have developed a method to prevent this absorption to a large degree.
Would be cool to find out!

By: Stephen Russell

Stephen Russell — Fri, 09 Mar 2007 18:45:08 +0000

2 bad we cant Rent or charter one.
Great use in a 007 movie.
Love to see off So FL for counterdrug raids & Persian Gulf area.
SE Asia area.
Weapons to add:
MiniGuns
M60
50 cal MG
Mortars
LAWS
Stingers.
20mm cannon.
rocket pods
EW array
Gun lockers for crew.
mini torpedoes.
50mm cannon fwd???

By: JH

JH — Fri, 09 Mar 2007 09:04:53 +0000

Welcome to last year DefenseTech!

By: jeff

jeff — Fri, 09 Mar 2007 08:32:18 +0000

carbon nano tubular materials? Not avail. as of yet! Coming soon.

By: George Skinner

George Skinner — Thu, 08 Mar 2007 21:20:17 +0000

Vstress,
I think the stiffness being referred to is the high modulus of elasticity of the carbon fibre in the tensile direction. The anisotropy of the material is an important design factor, but it can also be a valuable asset when used properly. The problem with a lot of carbon fibre use is the tendency of designers to treat it as “black aluminum”, which turns the anisotropy into a disadvantage.
As far as coatings & water resistance, I think it’s important to note that boats have been built out of fibreglass for decades. Carbon itself has got great corrosion resistance, which is why it’s the material of choice for fuel cell components. Impact resistance is another question, though — work boats tend to be built with aluminum or steel hulls rather than fibreglass for a reason!

By: Vstress

Vstress — Thu, 08 Mar 2007 16:41:40 +0000

“In structural design the key element is usually stiffness hence carbon fiber is good“
Was written by a person.
This statement is wrong.
Carbon fibre has very little stiffness. That is the biggest problem in it’s applicability. Otherwise everything would be built from it.
It is also the problem in it’s design, as structures need to designed for carbon fibre use, with material directions being extremely important.
A big question I have on this subject is the absorption rate of moisture into the carbon fibre. Hence I question the length of time this boat can be used, due to the corrosive sea atmosphere on the coatings that protect moisture ingress.
PS. I’m a structural engineer for an aerospace company… I know a thing or two.

By: jc

jc — Thu, 08 Mar 2007 13:15:10 +0000

In structural design the key element is usually stiffness hence carbon fiber is good.
In the real world boring ill understood matters like impact strength can be important. Think of hitting a log at 40 knots which was a key factor in removing seaplanes from the equation, now think of a floating container.
Physical data on composite strength is not that easy to obtain and izod or charpy results are a lot more difficult to obtain for carbon fiber because the people selling the stuff realize it is not a pretty picture.
When you see a film of a racing car crash with some degree of integrity remaining you are seeing kevlar holding it together; The carbon fiber having very little impact strength is a fine dust of sharp needles (like asbestos) creating a health hazard for everyone.