Size limits of BIG wooden ships? (global strength issues/why not use metal frames)

Discussion in 'Boat Design' started by big_dreamin, Jan 4, 2014.

  1. Tad
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    Tad Boat Designer

  2. ancient kayaker
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    ancient kayaker aka Terry Haines

    Interesting paper, awesome project.

    The math existed in previous centuries when large wooden ships were attempted with limited success. The highest math I got goes back to Jo Lagrange in the 18th century and would have been more than adequate. Of course a computer is a great help in getting the math - all of it - correct.

    Lacking that last item, traditional ship designs and builders preferrred to work from rules of thumb rather than from first principles. First principles would no doubt have shown it wouldn't work back then, at least not for long, but then again they likely didn't have the database from which to compute stress.

    The real limitation was the effectiveness of available fasteners, which comes done to the lack of a decent marine quality glue, and the technology to use it effectively. Plus - of course - nobody had invented plywood yet.

    A project of this size has the resources to institute its own quality control, the use of laminated wood takes care of material size limitations, I guess there is a bottomless purse to solve the cost problem, and the design team no doubt assure us - who are we to disagree - that the availability issue will be taken care of in a responsible and envirnmentally sensible manner. So that deals with all the problems I raised for creating really large wooden ships. Leaving us to wonder, why . . . ?
     
  3. rwatson
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    rwatson Senior Member

    That was a great read. It will take a while to absorb such a lot of info.

    The only steel framed boat I ever saw live was a 25 foot, flat bottom boat.

    It was built by a farmer with 20mm angle steel, welded - with large wooden hull planking.

    I understand it was done this way, because it was used to transport cattle across a river, and the hooves of the animals had previously destroyed the framing of a the traditional wooden framed boat he had been using.

    On a more current project - a 28ft plywood sailboat needs 130 kilos of ballast near the bow.

    It occurred to me that I would be better off using metal framing of equivalent weight, achieving vastly stronger structure, and still having the required weight.

    I wonder how long galvanized steel would last in a marine environment ?
     
  4. Ilan Voyager
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    Ilan Voyager Senior Member

    Double hot dipped galvanized steel lasts a long time in a marine environment, if some precautions are taken with galvanic corrosion and with the species of wood used. For example oak because of its acidity is known to "eat" any steel.

    Metallic structure and wood planking have been used since ages. From the 18 th century diagonal bronze straps have been used to improve the rigidity, the weak point of big classic wooden boats. On mid 19th century cutters like Cutty Sark were made in steel and iron structure with hardwood (teak and rock elm) planking, Gloriana around 1880 by Herreshoff used also structure partly in steel.

    In the 1920 several German fast yachts used a metallic structure and a double planking. From 1929 to 1945 the German torpedo boats S-boats (very interesting and successful designs, worth to scrutinize in detail the plans and remake the calculations for learning about NA and NE applied to a fast boat...) used a riveted aluminum structure with wooden double planking. Some English torpedo boats during and immediate after WW2 copied this structural design. The German S-boats structures proved to be very strong and reliable (and the Daimler Benz engines were very good...).

    I have seen several big fishing boats (around 25 to 40 meters) made in wood with lots of steel structure built from the end of 50 to beginning of 70's. There are many other examples.

    A metallic structure is an improvement when the boat has a pretty big size with a "classical" planking, which being only longitudinal, in "no-glue edge narrow strips" is unable to improve highly the rigidity. Epoxy cold molded hulls result is monocoque structure, so the skins take most of the stresses. Thus, there is no need of a metallic structure until at least 40 meters/350-400 metric tons (I suspect that the limit must be around 65 meters/900 tons).
    The few big mine hunters made in cold molded wood (around 45 meters/450 tons) used very little metal, as the thick sandwich hulls made to withstand the explosion of a mine had plenty of strength for the normal conditions of navigation.
    But the mine sweepers in classic wood built around the 1940-1960's used no metallic structure, because of mandatory a-magnetism, and suffered of a severe lack of rigidity: they were known for spitting their caulking and for leaking heavily in hard sea.
     
  5. peter radclyffe
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    peter radclyffe Senior Member

    an aluminium lattice framing and epoxy multi diagonal, fore and aft larch planking is one answer
     
  6. fredrosse
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    fredrosse USACE Steam

    Composite Hull Construction Iron + Wood

    The fast Clipper Ship - Cutty Sark built 1869 is a very good example of the composite type of construction, transitioning from wood hulls to the last iteration, all steel/iron hulls.

    Many of the US large sidewheelers needed a very big "hogging truss", sort of like a railroad truss bridge structure, running through both sides of a wood hull, perhaps 30 or 40 feet deep x a couple of hundred feet long, because the wood hull structure was just not strong enough to allow big shipbuilding without the truss.
     
  7. ancient kayaker
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    ancient kayaker aka Terry Haines

    I read someplace some at least of the US sidewheelers could be "walked" over a shoal (Mississippi?) - an advantage over a sternwheeler which also speaks volumes for strength and rigidity.
     
  8. gwboats
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    gwboats Naval Architect

  9. Ilan Voyager
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    Ilan Voyager Senior Member

    gwboats Thanks for the picture link of this beautiful boat. I had the curiosity to google Brave Class and I found this jewel http://www.bmpt.org.uk/\/other_boats_history/Brave class/index.htm
    The Development and Running of the Brave Class Fast Patrol Boat By PETER DU CANE, M.R.I.N.A., M.I.Mech.E., A.F.R.Ae.S. Yes a very good paper by the master himself. Very instructive for those that are interested by real Naval architecture and engineering, not advertisement papers.
    The site is more than interesting. I'm afraid I'll go to bed very late this night.
     
  10. chinaseapirate

    chinaseapirate Previous Member


    If you are still alive (lol). maybe you would care for a "positive" answer... Wood is a superior choice for any sized/length boat /ship -than steel, and loses now in cost no object competition to composites . One only has to design/build it within its own "wood unique" limitations. some specialized designs it may fail at. impact damage control (stopping a bullet, resisting recoil of large naval guns maybe even icebreaking (but i doubt it-just redirect the fibers)). Common arguments against this that I have run across include - "hogging", "internal stress" , "lack of strength/stiffness", "expense","labor shortcomings", but I haven't come across any argument so far that can't be defeated simply and reasonably. Hogging is simply defeated by plies or other fiber reorientation. Internal stresses from expansion and contractio at different moisture levels can be limited by laminates of smaller thickness. Lack of strength/ stiffness is the most common joke argument. Doug fir is over twice as "strong" as shipbuilding steel on a per weight basis. And before any of you "real" engineers decide to to feed me any youngs modulus "proof", please describe an aspect of post 1966 wooden shipbuilding techniques of semi monocoque structures where this would even remotely factor in. Welds are weak and 110% reinforced weld/joints are heavy. Expense? steel is $350/ton, logs are 30-40$/ton (retail) - cheaper from the government still in the forest.
    labor shortcomings? Well whose fault is that? the wood ?
    Almost any shortcoming of wood boils down to its incompatibility with steel material/steel fasteners/steel industry/steel based design. If you are still serious about a huge wooden vessel, I would suggest to forget wood / steel composite and go for bamboo /foam (for the holes in a woven bamboo structure) composite. I would bet that you could build a 400 ft catamaran aircraft carrier for 5 figures (maybe all 9's) in Madagascar , labor and materials included. Get yourself 3 Piper Cubs and a bushmaster 25mm cannon for another couple hundred grand. Serious - call for plans
     
  11. PAR
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    There is a decided size limit a wooden vessel can be practically built and it's not so much the materials as the labor, modulus and weight. Yes, 400' ships can be done, but not quickly, nor economically, with reduced internal volume and a host of other concerns, many of which aren't nearly as a concern, as other hull material choices. Ship building is all about money and labor, not hull material choices. With other choices you can have 75 year old, perfectly serviceable ships, but try to find a wooden one of this vintage and it's long since been cut up and dragged to the land fill, for obvious reasons.
     
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  12. gonzo
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    gonzo Senior Member

    Wild claims like yours are easy to make. However, saying that fir is twice as strong as steel is simply nonsense. On a large structure, like an aircraft carrier, the fibers would collapse when an anchor chain gets dragged over it. How about "Serious-call for plans" add a website, email or phone where somebody can call you for you so called plans.
     
  13. chinaseapirate

    chinaseapirate Previous Member

    I agree there exists a decided limit, who decided and when and why those old conditions (like the nonexistence of epoxy, fiberglass, many other synthetics, internet at sea) should apply today is what I disagree with. I'm sure there are some 50 year old wood/epoxy composites floating around by now. But forget all that, it does bring material cost up to $200/ton minimum. Have you ever seen you tube videos of ship scrap yards in India where they drive 15-40 year old ships up onto the beach as far as they will go? Well here is a short story of what you can do in a country where they still believe that if there is a will there is a will there is a way, still.
    One day a ship scrapping foreman got so sick of threatening his workers with starvation and extra unpaid work just so his brother-in-law could underbid his nephew on the next scrap out, he came up with a practical solution. He came up with the idea encasing one of those beasts with a very weak beach sand /cement mold 1/2 way up the waterline and build a scrap hauling ship from scratch. Why should he have to know how to build something that costs a zillion rupees, all he has to do is believe... He went partners with his wife and nephew and became "boss". A couple of old buses drive up one wagging a huge cement mixer being rolled over small logs because the "boss" don't want to waste money on a trailer for it. 4 months later 80 workers are camped out inside the "mold" 700ft x 100 ft( the last 200 ft of junk ship was too far in the water still) next to a pile of 40,000 tons of scrap steel. Also the cement mixer, 1/3 of the bamboo in the surrounding 100 km^2, 500 drums of creosote/heavy oil,and 80,000 sacks of Type II, and a mysterious bin of tangled up long green plastic strap. The nephew, who was upset at his father who had steered him into this deal, and who was out the quarter million dollars cash for the pre-panama enlargement tanker, set a time limit of 3 months to completion. Otherwise he would sell the steel and no one would be paid. So "the "boss" got started right away. After boiling 75% of the water out of the bamboo in a tank of creosote, the canes of all different sizes were set in a continuously poured slurry of "aircrete". Layer by layer of bamboo was bundled in 7 roughly equivalent diameter pieces and strapped securely into 700 ft lengths , often it was just tied with nylon and pinned to its neighbor with electric drill and bamboo carved dowels, as many as all the workers' kids could make between constant snacks and fighting with the bamboo. Each "layer" was forced down into the wet(extremely slow drying) slop below by strapping it between the previously strapped cross bracing below(thinner canes) and the new from above. Although "boss" went cheap and dedicated two workers to hand splitting the mysterious green plastic (imported polyester lumber strap detoured from recyclers before chopping them into flakes) into thirds, he did his best to make sure as little as possible of the bamboo could be dislodged by walking and jumping on everything he could. Too make a long story shorter...
    The 16,000 ton , 16lbs/ft^3, 80/20 "fiber" to "resin" ratio (maybe a few more voids than he thought) full scale model 740L x 106W x 28"H" ship shape raft was completed in less than 2 months. "boss" had to sell about 1000 tons or so of the scrap steel under his nephew's nose at local pricing of $40/ton to keep everyone paid/fed/happy, and square the books on material purchases with his father-in-law. But he did manage to outfit the new ship with a propulsion system from the 600hsp aux generator, shaved prop, shaft, crane, anchor chain and windlass (for those of you who still drag anchor chains across wooden rub rails - they make smaller versions) from the scrap pile, kind of Thailand river boat style hanging off the transom. He loaded it to within 4 feet of "freeblock", with the understanding of its "unsinkable" nature. He "set sail for China" with #200 55 gal drums of fuel, sold the remaining 38,000 tons in Shanghai and purchased 10,000 tons of cement loaded extra heavy into 80 shipping containers Pocketed his 3 1/2 million and change topped of his fuel drums. No one there mentioned SOLAS or IMO, even when he had to return to port and buy another 1/2 million dollars of "cement ballast" because his ship was rolling uncomfortably outside the harbor. A little better now the "boss" mused, but still dangerously HIGH on her lines...He would stick to the coast and venture to Vietnam to seek bamboo. He would turn his into a real ship with outriggers and floats...or maybe just saw it in half and lash some beams across the two decks...
    I haven't heard from the "boss" lately. I'm sure he did not sink. Maybe he was "eliminated" for dropping too many containers at once into the ocean (uninsured). Can't say. I can say with fair certainty the his ship would not ever have broke up and if it did jump way out of the water and land on a pointy iceberg...or get hit by a meteor... the two halves are still there...floating. It is estimated from section modulus that a ship that size and thick and using a single point load amidship suspended by static reaction forces at both ends, depending on how much rhum and beer that crew consumed while constructing it, would have a built in safety factor of 50-100 instead of 3 for steel of the same weight. 40-50 psi strain vs 2,000 - 5,000 for the bamboo/aircrete composite. And that is not even a fair comparison because steel ship designers use distributed loads and allow for plastic deformation in their calcs. I've never put a boat (including a 70 footer LWL 67, newspaper full of **** same as district attorney, -motored to CNMI 2003 -multiple news rags -"six Pinoys Saipan" including my wife/son/2 brother in-laws,chief carpenter and diesel mechanic- all with passports - AG Fat Turd told me "We can't allow this" - Filipino tourists at the time were allowed but only for use as servants and approved by governor apparently) in the water that I didn't jack the bow up and measure ZERO sag.
    I don't think original poster is alive or interested in wood ships anymore...maybe. But I'm done telling "wild stories" here. Wan't a 400 ft aircraft carrier for $200,000.00 - I'm in the yellow pages...chinaseapirate@yahoo.com. Otherwise, I'm done here. Pretty much the exact responses I expected. My fault..I was trolling for answers as to see if there really was a "structural limit" to the length of a ship. I already know that most wood BY WEIGHT is stronger and all woods BY WEIGHT are stiffer than steel. If YOU don't...well build yourself a bridge over an 18 ft crocodile pit. You get 4 sticks of 20 ft rebar. I'll be waiting on the other side of my (4)2x6 with my motorcycle I drove across. You want 100 sticks or whatever ABYC calls for and a welder? Then I get to glue or lash and the same number of sticks. I'll have an army across before you find electricity. By the way, you can anchor a 70 foot trimaran on a reef with a 10" Rapala lure and 150 lbs test mono 95% of the time, no need to wear out the rub rail.
     
  14. rwatson
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    rwatson Senior Member

    Yes, there may be incredible things done with old technology, and secondhand materials and desperate and poor people, but its only done rarely.

    When you have timetables, and you need 95% reliability and time is super expensive, these "seat of pants", "out of the box" solutions are just so iffy, that you cant hang a 20 million dollar investment on them. The insurers and port authorities alone would make life too difficult.

    The same with timber solutions. Engineering wise, timber does have competitive structural advantages BY WEIGHT as you say, You forgot to add BY VOLUME as well. Are you going to log the last of the Burmese forest illegally to build this ship ?

    Traditional wooden ship builders are having trouble getting decent quality and size timber for years now, so wooden commercial size ships are out of the question.
     

  15. chinaseapirate

    chinaseapirate Previous Member

    Paragraph 1) Agreed.

    P 2) All true but that is just a majority viewpoint. The "boss" found a way BECAUSE he had nothing to lose but time. I don't have the vocabulary to describe what I really think of the 3 different port authorities I met. First ***** in Palau sent me and my crew(isolated on board for four days waiting for an "early" typhoon to pass) on our way through a small boat reef passage without any thought of the 10-15 foot late arriving swells from the typhoon. Harrowing experience that first 10 minutes, coral heads everywhere on a forced beam sea route in a low buoyancy outrigger trimaran. Turning around looked worse. Yap Island was great except for the first night 4 BIG island policemen literally climbed aboard in the dark with no announcement holding automatic rifles. next day they escorted us to the "proper entrance" and everyone was allowed on shore after a day of "quarantine". Should have stayed there, they had provisions for permanent residents "with skills"..probably just a simple bribe payment for a couple signatures...lots and lots of fish. But no, I decided it was best to go to "my country". CNMI is officially like Puerta Rico, were all the same Citizenship except they had their own independent labor and administration code titles which DIDN'T contain any excludeable alien INS crap in it. Loophole was continuing to be used by Chinese mothers arriving by airplane pregnant. Suffice it to say they were ALL liers and petty extortionists. Port authorities...if they can't even read and speak ( English) and understand their own codes and regulations, what is their purpose?

    P3) I don't agree with stronger by volume. Maybe I'm just being a stickler...I know what you are saying - that because of it's volume (at the equivalent weight of steel) wood has an exponentially great advantage over steel related wood's sectional modulus/moment of inertia being based on two of the three dimensions contained in volume- did that make more sense? Too me its like if someone were to tell you "gas does't bur, vapors burn". Excluding their misappropriation of the slang "gas" as opposed to gasoline, technically I'd have to agree that they are correct. It doesn't always happen as planned but you can indeed suffocate a flame with the liquid known as gasoline. Hints for those trying at home - very cold days - small volumes (think shot glass or less) - wait till the phosphorus in the match has burned out - and don't try to put out the fire if you fail, just back away. Always have a permit when logging.

    P4) Are we talking about traditional ship building? I thought the topic was "truly large" wooden ships. I've described two examples of what I thought were large enough. One in far too much detail. The aircraft carrier was maybe traditional skills, long oversized basket weaving, but that idea was based on 1970's ferro-cement. Just replace the steel mesh and rods with woven bamboo and "mortar it" with foam cement - "aircrete" like the "boss's" 740 foot scrap hauler. Bamboo is a grass but its close enough to wood. There is probably more bamboo on Earth than steel, not iron ore, steel. It regrows in 3-5 years, very fast. And if used as described - whole or split pieces, extremely labor efficient. It can be indefinitely preserved by soaking it "traditionally" in a hot bath of wood oil or flavor of the decade chemical under pressure. Its quite possible it only needs a quick soaking in boron salt to last the duration of the construction if its ultimately encased within a cement/fiber matrix. I'm not sure if bacterial soft rot applies to marine environment but bamboo can host it and boron offers no protection from it.

    Ran across an article today that referenced a newspaper from latter stage World War II. They were building prefab ferro cement ships at the end of the war in an Diego. One was built start to finish and LAUNCHED in 6 1/2 days. They installed 20 bulkheads in 3 hours ! Takes a war to get people moving ? Mothballed. hulls were 7 inches thick with 20 % of the steel in an equivalent sized steel ship. 5000 psi concrete. They were making earlier WW I carry over design ferro cement ships earlier in WW II that were substandard and heavy, but this article said these prefab ships were not those and that project was mothballed and didn't say how many were built other than the ONE. So its more like a conspicuous lack of need from entities already owning steel ships that wooden ships are not considered or built. Does anyone know who designed this? upload_2018-4-3_6-12-34.jpeg

    hideous. why not clamp all the containers together like a brick wall and stretch wrap it in with inner tube rubber. toss the ship. I'm almost certain those containers are structurally integral they are clamped or strapped to something.
    Designer Chris White - "L cubed" ...
     
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