what material better wood metal etc

Discussion in 'Boat Design' started by Garth, Jul 25, 2006.


what material to use

Poll closed Aug 18, 2006.
  1. wood

  2. glass

  3. metal

  4. other

Multiple votes are allowed.
  1. MikeJohns
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    MikeJohns Senior Member

    I went to welding classes years ago, the first machine I bought was a 210 Amp continuous rated MIG welder and I have never looked back.....now on the 3rd machine after the other two were stolen at various times. No slag.

    I am currently helping a home builder (a Child care worker) putting together a steel hull, some of his welds have needed grinding out and doing again but on the whole without welding classes he is doing fine . Overhead welding is not so hard if it is a sealing run and vertical is a very easy weld. Home builders have the advantage taking things slowly, a little bit at a time. Pro welders working to a quote can cause distortion by charging into the job and laying down too much weld too fast. Often the amateur ends up with a better job and the slow approach works well with back-stepping techniques.

    Give it a go:)
  2. chandler
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    chandler Senior Member

    I have a copy of Gerrs Elements of boat strength. I also have a copy of McNaughtons scantling rules.
    I started McNaughtons course in Yacht design, and never went further than lesson 1 primarily because he tells his students "not to buy Gerrs elements of boat strength".
    I don't feel a good educator should ever tell a student what not to read!
    However the question remains, are either P.E.s or N.A.s? liscensed in the United States?
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    CORMERAN Junior Member

    Steel or............?

    To: chandler.

    Re: " .....at best a designer....."

    There's a long list of famous and capable people that would have a
    difficult time - getting work in a junior college today.
    - Like Churchhill, Einstein and Michelangelo.
    - Or the guy who created the Golden Gate Bridge.
    .....wasn't an accredited Engineer.

    - Einstein toiled for years as a clerk, before people noticed his ability.

    - One of my favourite stories about Mike is:
    - That he would not allow the Royal Engineer to smash holes in the the Sisten Chapel - to build a scaffold !!!
    - Instead; he erected scaffolding that was a self supporting, triangulated space frame.

    The Canadian who designed the Bluenose, that won race after race
    - against very tough American competitors - was an " amateur " designer.
    - The Bluenose was so famous that, the story goes - that when a U Boat
    Captain came across her in WW11 - he refused to sink her. Gave her
    safe passage.

    Dont get me wrong - I have hired on many Engineers, over the years.
    And have lots of respect for their diligence and expertise.

    Also, their inherent caution, can be a lifesaver.
    Said caution - might be why you arn't hearing too much from P. Engs.
    -in this discussion.
    As they can be sued for giving out advice that is too specific.
    - Even if they don't get paid for it !!

    Also, partly, because it's an apples to pomergranites situation - that
    requires a lot of explanation - that requires a lot of time and energy
    to achieve clarity.
    In the lab, there are MULTIPLE strength tests, that we do.
    Some - where steel shines - and others, where wood excells.
    Like DUCTILE qualities. In which metals do well.
    Tests of how ductile a material is - is really about:
    how TOUGH it is.

    So composites AND wood will show a much higher strength
    than a given metal - until they snap.
    Whereas the metal will still be keeping water out at the same P.S.I.
    Even if it is considerably deformed.

    The problem, if you want your race boat to stay fast, is that over time
    the metal becomes permently unfair - where ever it's deformed.

    Whereas, the wood or composite vessel - will happily return to a fair
    shape more readily. As long as you dont exceed it's break point.

    As, you can see, it's not a simple black and white issue.
    That's why designing boats is such a challenge.

    A well built vessel includs stuctural, mechanical and especialy today
    - electrical engineering. And a sophisticated overview of: - all of the above.

    Does any of us have the time to acquire 3 degrees in engineering before
    we dare to draw a boat ?!
  4. MikeJohns
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    MikeJohns Senior Member

    I thought I was being fairly vocal in this thread ?:rolleyes:

    That is a myth, We are protected if we stick to accepted engineering principles.

    True, science can be hard to understand at times and people tend to adopt a biased understamding to support a prejudice.

    Not correct, for a specific scantling design they show an equal strength up to the point where yield is reached, THEN the composite snaps and the metal deforms.

    What ? this is in the elastic range, all materials will return to original shape within the elastic range.
  5. chandler
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    chandler Senior Member

    I'm in the process of designing my own boat, I have no degrees.
    My point was that we have 2 "designers" publishing material that should probably be published by engineers.
    I have total confidence in what I'm designing and my own scantlings because I've been building for 27 years.
  6. Sonadora
    Joined: Jul 2006
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    Sonadora Scatterbrain

    I met a man who was building a Dix 43 from steel. Beautiful boat. He was halfway done - according to him. He had already spent 5 years on the project, working pretty much every day. When I saw the boat, he had just finished with the hull shell (stringers and skin). He had taken a few welding classes at the community college and his work was pretty good. The hardest part, he said, was getting the hull fair (it was a radius chine). I would have thought the hardest part was digging the hole in the ground to accommodate the keel. This was done due to height restrictions in the neighborhood.

    What astonished me the most wasn't the work on the boat or handling the material, but what his life was like. For 5 years, this is all he did. maybe a slow worker, but everything in his life revolved around this vessel. There was no escaping it. His office floor was carpeted with every industry magazine you could imagine. He worked two jobs to help fund 'The Dream' (which could explain why it was taking so long).

    Luckily, his kids were grown and out. His wife demonstrated full support of her husband by helping out when she could. She was melting lead and helping pour it when I last visited them.

    He was building the boat in a temporary out building in his yard. The plan was to be off by 2000. I drove by there a few months ago and noticed the building was still there. It looked as though he was still there too. I didn't stop. It would be nice to know how it worked out.

    Point is, there are many, many vessels and dreams in the same 'boat'. If you are serious about building a boat, the odds are against you. That doesn't mean you shouldn't do it, but you can't go at it half-assed. When I first got into sailing, I thought building a boat was something I wanted to do too. Meeting this guy proved to me that I absolutely do not want to do it. If I do want one of my designs built, I will do whatever I can to have someone else build it. When the thing is done, the costs in comparison will be minimal. Plus, I'll have someone to complain to if there is a problem.

    That being said, I have the plans for a 15' sailing skiff sitting in the bottom of my nightstand, waiting....


  7. Redsky
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    Redsky Senior Member

    and Sonadora just what does this reply have to do with the thread in general
    ??? scratches head.....
  8. Grant Nelson
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    Grant Nelson Senior Member

    Hey Chandler,
    No, I don't think Dave is a P.E or N.A. There are many long debates on the value of these degrees / certifications for yacht design. Probably Dave could be P.E cerficated, except in most states a 4 year engineering degree is a prerequisit, even if you have the knowledge via other means - P.E. is mostly a way to protect the careers of those who went to university, and a good Marketing tool, at least the way its applied - the tests have little to do with less than ship design, etc. etc. N.A.s can get their degree and never have to write the word Yacht, or think about things at that scale. Maybe it says something that a P.E. or N.A. never wrote a book like Daves... plus, I think you will agree that experience is perhaps more important - past scantling rules where written by those building boats, like your self, who know what works. Lastly, I have not yet seen any reviews of Daves book by an N.A. or P.E. who say his scantlings are wrong, so either they are not interested, or he seems to have gotten it right. Just my thoughts, and not disagreeing with you in any way.
  9. Sonadora
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    Sonadora Scatterbrain

    What I meant was...

    The discussion was regarding best material to use for boat construction, no?

    I now see I left out a whole train of thought regarding steel construction. What I tuned in on, however, was the comment from the author that '...I hope to build my own boat...'

    See, years ago when '...I hoped to build my own boat...' I looked into all of this too. Wood seemed easiest just from a material handling and 'perceived' cost. Of course, there's a great deal of literature on the plusses of using steel in small (~40') vessels. A lot of that literature deals with safety and spins yarns of how the opposing force (rock, coral, other boat) was subdued almost unnoticed by the steel vessel under way. As a husband and father of 3, this sounded great!

    So, steel it was. The more research I did, the more I convinced myself I wanted to build a steel boat. That all came to a screeching halt when I saw what it meant to build your own boat. But I digress again...

    What I discovered about steel was that it requires as much maintenance as wood. Of course, a lot of that maintenance is elective. Don't care about rust streaks? No problem! That's great for a tug. Not so great for the owner of a yar yacht. No matter how much coating you do, rust is inevitable. And, left for too long rust can eat clean through...metal rot.

    Still, if I was going to have someone build me a boat, it would be steel. I like the idea of crushing stuff before it crushes me. I also think the whole 'safest in a lightning storm' aspect of steel is pretty cool. In addition, as mentioned, welding/cutting is pretty easy if you're not looking for Abeking-Rasmussen quality.

    Aluminum seems like a good idea too. Jimmy Cornell has sailed around and around in aluminum boats. I'm just nervous about galvanic corrosion. Dropped a screwdriver in the bilge and forgot about it? hmmm....

    As for wood, it's probably easier to build a fair yacht in wood than in steel. Maybe I've breathed too many varnish fumes, but wood just looks better.

    What I haven't seen in this discussion, however, is that it may be entirely feasible to build a FRP one off. My understanding is that the forms are fairly simple to build it's just that the lamination schedule needs to be done very carefully.

    Or better yet, just have your boat machined from a giant billet by one of those huge 5-axis milling machines!

    I hope that cleared up my stream-of-consciousness ramblings...;)


  10. Redsky
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    Redsky Senior Member

    actually if one Grew a boat out of a single steel molocule now that would be hi tek.

    sigh i considered ,wood,ferrocrete<naaa bad image>,wood/glass, carbon fiber, steel
    then i considered the sledgeomatic method of what happens with each kind of material when u accidently run it up on the rocks..and which your most likely to be able to remedy from inside! while keeping the boat pumped out.
    n steel wins every time. and if you back that with a ferrocrete bathtub then u gain a huge amout of impact resistance. as somone else recently noted.
    which if your building a sail or motorsail boat just fits right in with the ballast side of things
  11. marshmat
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    marshmat Senior Member

    Oh, I wish that were so easy. I've spent most of the last few months trying to get a pair of five-metre plugs milled that way. There aren't many places that can do it, and the ones that can are expensive and busy. A 5-axis with a six metre bed is worth over $600,000. And since they're used three shifts a day year round, they break down, and need realignment often.
    One-off fibreglass is indeed feasible. The forms can be made quite cheaply if you're doing hand layups at room temperature. Factor in an infusion system or autoclave and things get a lot more complicated, but for ambient-temperature hand lamination there are many ways to get a plug or mould made.
    The tricky part is in laminate design, if you're doing it yourself. Books of scantlings are a good guide, but you need to be able to see where the stresses are concentrated, and then to calculate how much of what materials are needed there to ensure things don't break.
  12. Sonadora
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    Sonadora Scatterbrain

    Hi Matt,

    I work in the CAD/CAM industry where we deal with a lot of CNC machinery. $600,000 seems kind of low, actually. Maybe missing a zero? ;)

    There was a comment made here about composites. The recycled plastic 'boards' that are used for decking comes to mind. Not suggesting that you use these to build a boat, but could there be some type of material like this that would be suitable for marine construction? Think of wood construction but composite lumber rather than actual wood.

    Or perhaps walker bay will come out with a 40'er!

  13. Poida
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    Poida Senior Member

    Everytime I fibreglass I seem to fibreglass myself more than what I am supposed to be fibreglassing. Working with wood stuffs up my sinuses. Aluminium boats I've been on are too light and bangy.

    Steel sounds good to me. What do you reckon would be the smallest craft that it would be feasable to make a steel boat out of? Probably 3mm 1/8" would be the minimum thickness of sheet.
  14. marshmat
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    marshmat Senior Member

    Rick, I know what ya mean! This kit ain't cheap at all. I've seen many units that are indeed worth seven figures... the cheapest, most basic one I could find that's suitable for our job is over $600k. Want an extra decimal place of accuracy? That'll be another $725,000 please!
    Poida- A former neighbour on the lake had a 16' steel work/runabout, he ran it with a number of outboard engines. Thing was insanely heavy but pretty close to invincible against our local rocks. It was looking a bit rusted and dented by the time he ditched it though, it must have had over 20 years of abuse by then.

  15. timgoz
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    timgoz Senior Member


    Topside plate of 1/8" (0.125") would be as light as I would go. Designed and built well a small steel vessel utilizing said plate posesses imense strength. The bilges, keel, ect... would use heavier plate as appropriate.

    MIG would be the best choice for fabrication as it gennerally produces less heat and therefore less distortion and a fairer hull.

    I love many designs of a variety of materials, but for a true voyaging boat that intends to see service in remote and rugged areas, steel has no rivals. Nick Smith, Capt. of John Bockstoces "Belvedere" says "no deal, without steel". John says "Smitty" is one of the best small vessel ice captains in the world so his opinion carries wait. Put John R. Bockstoce into a search engine for his extremely capable credentials.

    My own thought concerning the argument of wood's extreme strength compared to steel is "we use steel tools to work wood, not wooden tools to work steel.

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