can you decrease plate thickness or use FC for a tug?

Discussion in 'Boat Design' started by tugboat, Apr 17, 2010.

  1. tugboat

    tugboat Previous Member

    Hi Tad- understood- The small tug in the pics on here is called the Alert- it is fiberglass hull 1.25 inches thick. It was used commercially until it was bought by a maritime school.
    i would sya this was successful. there mya not be any urls that point to successful commercial tugs in either of those materials but that doesnt mean they didnt exist. some time ago i saw one listed on french creek boat sales in BC. a fiberglass tug. 40 feet. She was listed for around 75000 i think.. she sold right away...the samson blueprints were lost...
    the tug is not intnded for towing -however it could be -if i am not mistaken- insured as a commercial vessel. but dont quote me on it--ill call TC and find out.
    have you ever seen this stuff?..its stronger than concrete. by far. in all stresses.
    but its true i dont plan on towing day in day out other than some aoccassional work here and there under the table. ie to unground yachts etc..its half the price of a steel hull completed...
  2. Tad
    Joined: Mar 2002
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    Location: Flattop Islands

    Tad Boat Designer

    Akkk.....The commercial registration is a whole other ball of bureaucratic requirements...stay away from it if you can.......If you want to register the boat as a tug you have to meet TC requirements for tugs, including stability, electrical, construction scantlings to approved class, crew certification and manning (no more 2 man tugs), fire, bilgepumping....on and on....And if you want to go out and compete with Sea-Tow keep your head down...those guys don't take kindly to non-certified competition.....

    The true beauty of steel in this type of application is it's enormous plastic will bend forever without ripping open and letting the water in. Fer-a-lite cannot do this.......
  3. pdwiley
    Joined: Jun 2008
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    Location: Hobart

    pdwiley Senior Member

    Build a panel of Fer-a-lite. Firmly attach it to something solid. Bolt/attach a hard point to it to whatever spec you think necessary to hold expected load. Apply load using a big winch somewhere else and see if it holds.

    Now triple the load pretty much instantly to simulate a snatch load coming onto a towing cable. See what happens.

    I've sheared 8 24mm steel bolts when this happened. Well technically we sheared only 7, the last one was not quite sheared. I spent 11 years working on icebreakers loaded with oceanographic winches, net winches etc and another 5 years on lighter displacement oceanographic research vessels. I don't think you've got the slightest clue of what sort of stresses you're dealing with in a seaway.

    You are setting yourself up for a very painful and expensive failure but some people simply can't learn through others' experience, they have to do it for themselves. It seems that you're one of those.

    Good luck.

  4. tugboat

    tugboat Previous Member

  5. tugboat

    tugboat Previous Member

    Tad--(laughing) yea i will probably stay clear of beaurocracy if at all possible--the boats not for full time commercial service...seriously ive worked on tugs--ive never seen a situation where either material would be so stressed. ive seen it puncture though!!! easily ive seen ice boats walls flex so much they would tear at any second--and thats like 1 inch steel!!
  6. tugboat

    tugboat Previous Member

    I will do some tests..but i believe the tests will hold if done right...
  7. apex1

    apex1 Guest

    Do it, we will see...........

    Never you have seen a Icebreaker hull flexing to such extend! Now you start telling Icebreaker crew about their vessels?
    Come on........
  8. tugboat

    tugboat Previous Member

    what about frp layup of a tug hull? what would be the diff compared to fer-alite which is pretty much fiberglass?
  9. tugboat

    tugboat Previous Member

    Not an icebreaker hull no...but a regular hull in ice..for example 1/4 inch steel hull would be crushed in ice but a thicker fc or fer-a-lite- probably wouldnt...

    interesting--did the distributer send you some samples?...I have talked to him and I have seen not worried about the material..i actually did some experiments using the same idea - using some simple chopped strand and was slighty brittle but I could have hit the thing with a sledge hammer full force and it would have only cracked it slightly--imagine that with reinforcement!!-i bet its indestructable (within reason)..this is why i KNOW the product will be a good boat--i have never seen micro cracks on the test work i did...
  10. pdwiley
    Joined: Jun 2008
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    Location: Hobart

    pdwiley Senior Member

    Somewhere I've a photo from one of our visits to dry dock.

    We cut out a dent the size of a VW car at the bow well under the WL. Hit a bergy bit at speed in the sea ice. The whole bloody ship rang like a gong and a lot of my datalogging equipment came down off the mast from the whip - in pieces. No leaks, just bent internal frames and deformed/stretched plate. A simple dry dock fix and the repaired area is as strong as the original hull.

    Please, tugboat, do not tell Richard (master of an icebreaker) - or myself (spent 11 years sailing on one and was manager of a marine science engineering group) about materials and working in severe conditions.

    There is no information on structural properties of fer-a-lite that I can find on the net so it's impossible to compare to A36 steel for example.

    Here are the specifications for A36 steel.

    Tensile Strength, Ultimate 400 - 550 MPa
    Tensile Strength, Yield 250 MPa
    Elongation at Break 20.0 %
    Modulus of Elasticity 200 GPa
    Bulk Modulus 140 GPa
    Poissons Ratio 0.260
    Shear Modulus 79.3 GPa

    Please post the equivalent values for Fer-a-lite. The manufacturer should be able to supply them for any engineering product, along with any caveats.

    I can think of a number of pretty simple tests you could do to find out its properties for yourself.

    Here's a simple one. If the product is so wonderful, then it should be capable of taking the load of a shroud or forestay, yes? Form up a section of say 100 x 12 x 75 using it, put a shackle through a hole in it 20mm from an edge and start loading it up. Do the same thing to a piece of A36 flat bar of the same dimensions. I'm willing to bet and give you odds that the fer-a-lite gives up first.

    Since this product is so cheap and easy to use, really you have no excuse for not running some serious tests. How about you stop posting and telling ship builders, scientists and engineers with lifetimes of marine experience that they're all wrong and go and PROVE it? IOW, put up and until then please shut up about new miracle products. Do not talk, DO.

    You have 'wanna boat' disease. You know what you want and it exceeds your available budget. You're looking for a miracle that allows your budget to stretch to your dream. It's not going to work; you need either more money or less boat (or a different SOR). The only reason I'm still here is so that other people reading this thread might learn something.

  11. tugboat

    tugboat Previous Member

    PDW- are you finished your assasination attempt on my character?? since you know my financial situation so well and you know ive never built skippered or designed any boats right?? make idiotic assumptions about me...

    ok--we can play chess-

    on a stress point the size of a quarter--steel will puncture easily-that means the yeild of that point at a small stress point will puncture steel or rip it open or cause failure in some way. it wouldn't take much force either- a berg which has a large surface area and blunt impact. plus its ice-it cracks crumbles and generally isnt nearly as strong as that doesnt impress me-
    fer-a-lite boat would bounce off a berg as would wood and fiberglass because the force is deflected through the large surface area and dispersal of impact- so i dont buy your implication that steel is a better material and that it would hold up better than a FC hull against a berg--the FC hull prolly wouldnt even be damaged.

    sure steel is stronger-i never said the FC material was "stronger overall" than steel--read my posts--not once did i say that thickness per thickness its stronger-- what i did say was that under normal conditions- its as good as steel..and in some areas stronger- depending on the type of stress...i dont need to prove anything to anybody--you seem very admant about disproving it however...

    btw-how many boats have you designed and built?? ive done six to date-and i designed them all then sold them and they all floated on thier lines and were excellent boats. so dont tell me im some wanna be- ive done my "build-time"-
    its even possible i have more experience building boats than you- and certainly i can design better than you-since you dont design them. or you would be building your own deisign now.

    and heres the kicker: whether i failed or succeeded- at least i had the guts to try my own designs instead of being some sheep in the herd who parrots off info from any first year community college engineering book- If we lived in the 1890's youd tell me welding a hull was never going to work and that heavier than air vehicles would never fly!!

    you havent a red clue about my situation. accusations about finances and 'wanna be' status?-WTF?--just because you are plating a hull right now i suppose that gives you license to be tell me to shut up? good luck with that!

    tell me how long have you been working on that boat of yours???

    perhaps you feel threatened that there might be something as good and cheaper---because if there is--then those who pay twice the bucks for thier pet material--look stupid. when the cheaper one performs the same and can achieve more-anything new-is always first criticized...then finally it becomes the accepted way..

    fact is steel has just as many drawbacks as any other material
    there isnt a perfect material and when you build a boat its a risk!!all materials have drawbacks and strengths..even for commercial operations...

    so-while steel probably is the strongest material its also the heaviest- its hard to work and fit properly-it expensive as you know- anything beyond a chine hull is exremely difficult for an amateur builder, so the builder must rely on very inefficient chine hulls, it is easy to hole in a small surface area-i.e. rocks-pilings,reefs, steel protrusions, and fatigue or rust will hole plate easily...its heavy, backbreaking work,- it rusts away very fast-prone to electrolyisis
    - even when sand blasted-in a few years its gonna need to be reblasted and then you lose plate thickness- its not really monolithic either.

    plate is welded so its prone to heat buckling- bad quality steel-
    and during welding; distortion, bad welds, etc. in other words unless you are real good at welding you better be sure the metal doesn't rip apart in a seaway,this is why people x-ray the welds...because its not easy to get good penetration. how will you know if you got good penetration? soundings cant tell you that...
    steel can fatigue causing instant failure of the hull and I can go on ad nauseum--so dont tell me i dont know about steel or other materials...
    ..and dont think cuz you worked on an ice breaker you are more experienced than i am as a sailor! or the guru of materials science either..dont tell me that I dont know what its like to work a commercial vessel, i bet i have more actual seamanship skills on a tug than you ever had on your icebreaker-

    ...maybe you should be the one to put up or shut up..i need to prove nothing ...if this is a threat to you- start a thread denouncing it...but dont come on mine and tell me i dont know what im talking about-or im some wanna be, --better be careful first that you dont assume too much...
    oh yea im sorry- im just making sure that others who read this thread will be just as informed...
  12. apex1

    apex1 Guest

    Until now, I thought, we deal with a nice guy, who has a bit a preconception towards Ferro Cement rubbish.
    But here you have shown, you are not to convince, and worse, you even feel to have superior knowledge!

    When each and all and everything contradicts you, what do you guess, who is wrong?

    Sorry, your impertinent rant has shown you have not been worth the input of NA´s builders, homebuilders, sailors and seamen.

    Go your way and fall on your face, I hope it hurts enough to clear your brain.

    Over and out (finally)
  13. sorenfdk
    Joined: Feb 2002
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    Location: Denmark

    sorenfdk Yacht Designer

    How come you suddenly became such an expert? Earlier, you demonstrated that you didn't know the difference between stations and frames!
    Most of the drivel quoted above is utter nonsense.

    I'm out of here, too!
    1 person likes this.
  14. pdwiley
    Joined: Jun 2008
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    Location: Hobart

    pdwiley Senior Member

    Just because you were a deckhand on a tug or something doesn't mean you actually know anything about marine engineering or structures. A single piece of scientific equipment that we used to put in the water cost 10X your entire budget and I was responsible for all the equipment for the entire program. I had 6 engineers working for me full time. Money wasn't really the biggest driving factor, the ability of equipment to work consistently under very harsh and remote conditions was. I have a strong dislike for stainless steel wire rope for example because its mechanical properties are inferior to galvanised steel yet 99% of yacht types use it....

    You don't know what you're talking about, that's obvious. I feel sorry for you, not threatened, because you simply haven't got a clue and you simply don't want to have a clue because as I said, acknowledgment of reality would show you that you can't afford what you have your heart set on.

    Off you go, then. Get back to us when you've built something. There's no point in your posting here asking for advice because every bit of advice you've gotten contradicts your preconceptions so you're simply wasting your time. ATM you're a wannabe dreamer who doesn't know the basic structural properties of materials let alone how to build anything. Perhaps you should consider building a BS origami design?

    OBTW there's at least 1 person on this forum who's seen the boat I'm building and the house and the machine shop, all of which I personally built. In case you were wondering.

    1 person likes this.

  15. tugboat

    tugboat Previous Member

    good for you PDW-- i would LOVE to build origami--but its really for chine hulls...

    perhpas i was probably a bit harsh in my response and for that i apologize--

    the problem here with this: is people DO TRULY feel threatened by something new and good...
    I am not asking others if i think what i am doing is going to work or not--im asking for help in specifics of what im doing--not to have people tell me " this wont work" or "that isnt good" -"or that i dont know what im doing" or (and this is actually so rediculous its comical) that i dont have enough money etc..--tall assumptions--I would rather others inputed creative ways tosolve problems not try to dogmaitcally convert me to thier way of thinking...

    anyway-- i am building the boat now...itll take probably as long as yours will...btw i wouldnt mind seeing some pics--not because i dont doubt you--because i am very interested...
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