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Carbon/Kevlar Fiber Hull vs Steel

Discussion in 'Technical Discussion' started by TheAdmiral, Nov 12, 2010.

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  1. TheAdmiral

    TheAdmiral Guest

    It's well known that the latest in Hull Materials using Carbon/Kevlar Fiber is stiffer /stronger/lighter than steel yet the issue is "point of impact " strength.

    A reef/rock/floating container or even bullet can have a sharp point of impact where all falls apart literally.

    As a soon to be 1st time owner I dread the possibility that I will go with a no steel hull and suffer the consequences.

    Who can add here? Thank you.
  2. dan1000

    dan1000 New Member

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    While I cannot claim to be an expert in this area, I have at least considered the question much as you are doing now. Here's what led me to be happy with my stoutly built fiberglass-hulled boat.

    1) Steel and fiberglass (and aluminum and wood) are great building materials. The evidence is that a large number of boats built of those materials are successfully still keeping the ocean on the outside. Thick ones, thin ones, old ones, new ones. By and large, they float.

    2) All materials have their ups and downs in terms of what you can easily build with them, how long they last, what maintenance is required. A poorly built or maintained boat will do poorly, regardless of what it is made of. The opposite is true for a well made/maintained boat. Steel rusts (unless properly prepared). Fiberglass delaminates (unless properly prepared). Aluminum electrolyses away (unless properly prepared). Wood rots (unless properly prepared).

    3) There's no question, if you want to rub against rocks or corals, a steel hull is better than a fiberglass one. However, the number of boats of either variety that actually are holed is so small that making a decision on this basis is really a case of the tail wagging the dog. There are many other reasons to choose one material over another, but all such reasons involve compromises of one kind or another. There is no "best" material, but there will be a "best" set of compromises for your intended use and budget. But puncture-resistance is likely to be 10th on the list of goals, not first.

    4) While we all want a boat with a very strong hull so that it will forgive any indiscretion we may present it with, the stark reality is that even the well known brands of poorly built "price boats" actually keep on floating despite having apparently been built by the devil (according to people's views). While I'm not advocating buying a poorly built boat, even the poorly-built ones keep floating. Can one find counter-examples where a thin boat has been holed? Of course. But once again, in the list of things that can go wrong, being holed is way down that list.

    5) In my own case, the reason I bought the boat I did was because I felt it would be safe, reliable, comfortable, and economical to run, all in just the right order and with the right set of compromises for my goals. I would have bought it in fiberglass, steel, or aluminum. Not too keen on wood, but perhaps that's a personal bias. I would not have bought it at all if I thought it was poorly made, or if I thought the components on the boat were poorly chosen or installed. Mine happens to be fiberglass, which they now reinforce with kevlar.

    Finally, let me add the following:

    Boats sometimes sink, but usually because of rain (yes, I think this is actually the most frequent cause, albeit on small day boats), water intrusion via thru-hulls and plumbing problems, swamping/very bad weather, and so on. So, have good components and keep the boat well maintained.

    Boats are cursed when they fail to start or run reliably, ruining a planned trip, or creating anxiety for the family while at sea. So, have good components and keep the boat well maintained.

    Boats are further cursed when one looks at the money used for the value they provide. Less money is, for most of us, better. In my personal opinion, it probably costs more, but only a little more, to maintain a boat at 100% perfect condition rather than 80%. But I bet it costs less to maintain it at 80% than to maintain it at 60%, where every repair will be a "last minute" job done by someone who recognizes the urgency of your situation. So, have good components and keep the boat well maintained.

    And try to avoid running aground on rocks or coral. Even if not punctured, the boat could end up on its side and essentially ruined.

    I'm sure those with much more experience than mine will chime in with additional views, but these are the views of this first time boat owner.

    Dan Freedman
    Sea Spirit Passagemaker 60




  3. NYCAP123

    NYCAP123 Senior Member

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    Dan1000 is right when he points out that being holed is a small consideration for most boats, although it does happen. Far more likely scenarios would include being rolled, pitchpole, having the running gear torn out or damaged, fire, swamping and the list goes on. He's also right about the fresh water sinkings although I believe the biggest cause for this is leaving the dockside water turned on while off the boat and having an interior hose break. You will not avoid all risks. Instead, you minimize them by buying a quality built boat with good handling characteristics and learning you craft (how to read the weather, approach waves, avoid collisions and stay off the rocks). Of course, if you're heading into areas of ice you want as strong a hull as possible, but most of us compromise to add speed, comfort and price. I'd feel much safer driving a tank on the LIE at rush hour, but it wouldn't be real practical.
  4. brian eiland

    brian eiland Senior Member

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    You didn't specify whether this was sail or power, or what style hull?? These all have a bearing on hull material as well.
  5. TheAdmiral

    TheAdmiral Guest

    OK well.. its simply this.. I will be building a large motor yacht soon and piracy is ever on the increase. With the world economy going to shreds, piracy will again become prevalent and I wouldn't want some jerk with a gun be able to sink /ruin/disable my entire ship with one shot.

    Soon, things will change dramatically and even police boats etc.. once societies break down, will be hunting for themselves using whatever they have simply to feed themselves and their families.. As well, the ability to " park" on a deserted reef and live for a while is well within the possibilities until society reorganizes itself.

    KNowing that in the near future, some lands will rise and others will fall. Depth charts etc will be of only some use. Massive tidal waves will show themselves more frequently. THis is all part of whats coming and so nautical operations and navigation will change. The earths magnetic poles will shift throwing off compasses and perhaps electronics will not work as designed if at all. Yes i know it sounds like its out of a movie but trust me.. its not and its whats coming. The oceans will be the best place to be as plagues and disasters will dominate the cities and lands all around.

    So the best hull in these circumstances is really the question.

    I have seen evidence of the carbon fiber hulls being trashed from direct point of impact which of course no one hopes will happen yet it cant be a possibility in my mind. Whether its a reef or AK 47 doesnt matter but I know a steel hull wont be hindered by an AK 47. Would a Carbon Fibre hull reinforced with Kevlar or anything else technology offers be resilient enough?
  6. dan1000

    dan1000 New Member

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    Admiral: While I disagree with your assessment of where the world is going, I have also thought a little about pirates.

    My conclusion is that the choice of hull is largely irrelevant to the success or failure of a "professional" attack. A 5 gallon jug of gasoline poured down the engine room air intakes or other openings, and then set alight, will most likely get you out of that nice steel hull very quickly, or at least remove your ability to flee. And the AK-47 and a propane torch would likely do quite well against even 3/4 inch windows.

    On the other hand, a well-secured hull of any material is very likely to dissuade what I would call an "attack of opportunity" (ie: teens, fishermen, dinghy thieves, and so on).

    GOST has some interesting defense products, including one that fills the cabin with breathable fog in a couple of seconds, removing an intruder's ability to see, and therefore continue an attack. They also have an "acoustic barrier" that made a believer of me when I heard it demoed at FLIBS. I would not expect either of these to be definitive against a professional attack. They would be extremely effective against attacks of opportunity.

    Finally, while it is always possible to personally conduct a lethal armed response, doing so has at least as many consequences as not doing so. Those with the necessary training and demeanor should consider it, but those same people will be acutely aware of the responsibilities and limitations that accompany it. Those insisting to come aboard my boat will ultimately find out which camp I fall into.

    Tasers are probably a happy medium. An escort through known bad areas, or avoiding them entirely (use Dockwise/Yachtpath instead, etc.) is also worth considering.

    Since avoidance is always the best defense, perhaps one should aim for a modest, ugly boat that appears not worth the effort to rob, and yet appears well secured to those who try anyway.

    Choice of hull material does not, to me, appear to be anywhere near the top of the list of defenses.

    Dan
  7. NYCAP123

    NYCAP123 Senior Member

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    Admiral, When you talk of Kevlar hulls it is not the same as bullet proof vests. They do not stop a bullet. Most of what you fear is decades off and shouldn't even be a consideration in your build. Odds are that whatever boat you build today will be your previous boat in 5 years, and good luck selling it if it's a tank. Besides, unless it's nuclear or wind powered and huge (to stock years of provisions), you won't be off shore waiting for the 2nd coming. Yachts are built to be enjoyed and designed to withstand conditions of sea and weather. Don't even think of them as a refuge from revolution. If you're afraid of the poor and underprivileged taking over, a yacht is the last place you'd want to be. They are such an easily identifiable target and extremely hard to defend against a planned attack. Better to get a studio apartment in a slum, steel plate the walls and windows and paint grafitti on the door.
  8. JustMag

    JustMag Member

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    There was this odd fella a while back that built a very large vessel ( 135M x 22.5M ) out of wood. Bit of an animal lover as he had two of each species................ Seemed to work out pretty well for him
    :)
  9. Seafarer

    Seafarer Senior Member

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    You should do some research on metallurgy and ballistics.
  10. JWY

    JWY Senior Member

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    NYCAP -- I disagree with your opinions and statements-as-fact. While I have numerous classifications for my trawler and long-range cruiser clients, one group I respectfully call the "paranoid". These guys are concerned with protection of life, whether that protection includes close encounters with hard objects such as rocks, steel ships, or other objects, but also against the evils of humanity. For many of my clients whose # 1 priority is the ultimate protection from hazards at sea, whether by nature or man, I recommend steel. For the ultimate paranoid who has "escape" as the # 2 priority, I have sold many steel trawlers that hold 5-9000 gallons of fuel and can hold years worth of provisioning. And then there's the ultimate paranoid who is worried about EMP :eek: and also needs mechanical engines.

    Dan1000 wrote a remarkable response (x2) and gave a lot of wise and practical advice for the "non-ultimate paranoid."

    Admiral - Welcome to YachtForums :D
  11. TheAdmiral

    TheAdmiral Guest

    Thanks for the welcome. All useful.. And paranoid becomes realist when it happens.

    ...and I didn't expect people to agree with my assessment.. just the best kind of hull.

    Camping out on a reef for a year - in an out of the way place may not be a bad idea - with the right ship and crew of course. I would like to think it can be done in a remote place.. and yes.. lethal defense is the best way to make sure the pirates know there is lower hanging fruit somewhere else.. perhaps on one of JWY's trawlers ;-).

    And with that said and back the the original thread, just how durable is a GRP hull? Can they be made bullet proof? Would they be better than steel on a reef scraping?
  12. dan1000

    dan1000 New Member

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    Bulletproof FRP hulls are discussed here and many other fora. Note that the size, speed, and composition of the bullets is of no small significance.

    Please notice however that most modern pirate attacks are against bulletproof steel-hulled freighters/tankers.

    Some of the items mentioned previously, such as fogging and acoustic responses, seem to make a difference in the ultimate outcome, though hardly definitive.

    I'm not in the physical security business, but have been in cyber-security for the last 20 years. All I can say is that expecting one's adversary to only attack the hardest points in your defense may work against incidental attacks, but will not deflect a professional. Sun Tzu had many things to say on the subject, not the least of which was "When strong, act weak. When weak, act strong". Guiding the assailant's attack is vital. Avoiding it is even better.

    Dan
  13. NYCAP123

    NYCAP123 Senior Member

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    Sorry, but I can not see a yacht as anything less than the worst possible place for a paranoid to go. It reminds me of the bomb shelter and 'duck and cover' exercises of the 1950's. Interesting, costly and utterly useless against the percieved threat.
    Dan1000 did have a good response, but we've had enough macho discussions about arming boats to fill an NRA convention. So I wasn't going to drag this thread there.
    My response was to:
    I understand and agree that certain people or people in certain places need to protect themselves, but if a customer hit me with that....Well, maybe that's why I'm not a salesperson.
  14. tirekicker11

    tirekicker11 Senior Member

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    Maybe Dashew's new FPB 112 from that other tread would suit OP.

    (If societies fall apart and "Waterworld" is the only way of surviving what is it worth living for?)
  15. kdumph

    kdumph New Member

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    Why not just use normal material and invest in a remote weapons system;) Heck you could put the monitor and joystick right next to your chart-plotter!

    Pirates use a lot more then 7.62 rifles. A RPG will go through a good amount of armor and will turn any ships hull short of a destroyers into swiss cheese. If your truly worried about it, the old saying applies. Best defense is going to be a good offense.
  16. NYCAP123

    NYCAP123 Senior Member

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    Or a lot of hp.
  17. motoryachtbill

    motoryachtbill New Member

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    You can build as strong as you want with either material. It is not fair to compare the properties of Kevlar/Fibergalss vs. steel as most modern builders are using a composite cored construction and you have to consider the strength of the overall structure. We had a boat hit a sea buoy at speed and the outer laminate was damaged but the core material spread the load and the inner skin held. If it were relatively thin steel or single skin fiberglass would it have fared as well? It is hard to say. When you see the internal framing from the outside of a containership that is 10 years old it reminds you how thin these skins can be. Composite boats are getting bigger and better all the time and I think it is a mistake to assume steel is necessarily stronger. Do some research on Corecell foam composite construction.
    As for being bullet proof I do not know how different they really are when you consider Kevlar outer skins, dense foam cores and an inner laminate. It would be an interesting test to build a panel for a given yacht in each material.
    We just did a fire test on a panel and after several minutes with a torch it self- extinguished as soon as the source was taken away. Steel is better in a fire no question, but is the overall boat that much more fire resistant? How is the steel hull insulated? What types of coatings are on all the surfaces?
    The Steel hull will require a lot more framing than a composite hull. The overall weight will be considerably more. If you want to travel above displacement speeds the composite hull will give you better performance.
  18. Highlander

    Highlander New Member

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    Ditto on the Dashews FPB line.
    With one of those, you can go far enough away that no bad guys have the range to get there.
    Built to take a beating from groundings or bad weather.
    A roll over in a storm is a more likely event than worlds end, and the FPB can handle it.

    The Dashews design for the worst case. Don't know about bullets.