Easyway out

Discussion in 'Stability' started by evantica, Feb 17, 2010.

  1. peter radclyffe
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    peter radclyffe Senior Member

    any book by john leather,
    boatbuilding- chappelle
    down channel,r t mcmullen
     
  2. Itchy&Scratchy
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    Itchy&Scratchy Senior Member

    Ive just bought a book on clinker bulding by John Leather, very nice and informative little book, well worth the money. Actually there are some really nice books full stop, on the market at the moment.
    Itchy
     
  3. evantica
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    evantica Senior Member

    will have to live, to be 135 years old..OK theres somethings a man have to to go trough, This is probably one of them.
    The seaworthy offshore sailboat... is likley on the shelf?! The same "John" who wrote 20 small sailboats to take you anywhere?????
    Bad wheather sailing also (Peter something)
    the "forgotten factor"...I've read something about?! there was a whole serie in the PBO (english mag.) about "Bluewaterboats" and the "Why's and How's" Wich was very learning for me.
    "Element of boat strenght" Sound like a very good ide' Teddy:Thanks for taking the time and write this down for me, Appriciate it alot.
     
  4. TeddyDiver
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    TeddyDiver Gollywobbler

    Leather, Chappelle and also Tom Cunliffe are on my "best reading list" too..

    evantica, if to choose only one book of boat design it's the Larsson&Eliasson, Principles of B...n
    Most of the books mentioned are must as references to checkups concerning different things involved in boat design and building process. Even pro's use references during the process thou not as much as we amateurs need to do. Of course if you have done something repeatedly it gets embedded in to your spine permanently. Like I don't have to open a book to produce small skiff or clinker boat but an offshore vessel is totally different animal.. :)

    chears Teddy
     
  5. Perm Stress
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    Perm Stress Senior Member

  6. evantica
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    evantica Senior Member

    Perm stress what are you saying???
     
  7. evantica
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    evantica Senior Member

    Perm. I went trough the whole link tread... My god, what were they thinking??? And how a bout the "common sense"??? An more tragic! there where manyboats how was incredibly whitout thinking?!
     
  8. Perm Stress
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    Perm Stress Senior Member

    What I am saying, building without plans could easily end up with not adequate results.

    Just few points, easy to see:

    1) Prototype

    Hull used for plug is that of motor boat, (or so it appear from the photos in Your tread "Building in progress"). It should be remembered, at ~8m in length, motor boats have lighter displacement by ~30 to 50%, because they do not have massive ballast, sailing rig, and structural reinforcements to carry them. While for the type of boat in question engine and interior are about same.

    For this, it is probable that plug have too small volume to carry weight required for sailor. Yes, new hull is larger, as original, but if it will be large enough is anyone's guess for now.

    2) Hull shape

    Motor bots do not need so much stability, as sailboats need to carry their sail efficiently. In fact, for motor boat less initial stability is better, as it mean softer rolling at sea. And their hulls are shaped accordingly .

    For this, it is possible that new boat will lack adequate initial stability (at 0 to 30 degrees of heel) to carry her sails efficiently. I do not mean capsizing. I mean enough "power" to be delivered to hull.

    3) Hull weight .
    steel density is ~8t/m3
    wood density is 0.55-0.8t/m3 (pine to oak)
    when we assume a wood density 0.6 (pine), steel is (8.0t/m3)/(0.6t/m3)=13.3 times heavier as wood.

    This mean, steel plating of 4mm is same weight as wooden planking ~13 times ticker:

    4*13=52mm !!!

    I do not believe, that boat used for plug, do have so heavy planking, it should be closer to 20-30mm. So, steel plating only will be ~2 times heavier as wooden prototype, even before framing and stiffening.

    4) Overall displacement

    Add to heavier hull:
    * interior (read lightly built second, wooden boat inside of steel hull + insulation),
    * sailing rig,
    * ballast,

    And overall displacement will easily more than double that of prototype hull. Is it accounted for when shaping the new hull?
     
  9. evantica
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    evantica Senior Member

    Thansk for very informativ answer but...
    1.The Plug/ former boat was a rigged Lots from early 1907
    2. The Oak planking is/ was 30 mm. and on the "edge" the planking is almost 50 mm.
    3. The orig Frames is huge pieces of Oak
    4.The weight of her: close to 5 tons, and this without rigging. now the shell is ca: 1,5 tons!
    we used just the engine to take him/her around and. but coz' of her very full and round hull she was rolling = Will have a rigg to "build her up".and make her steady!..so the scepsis from some of you could be right, even if I!!! dought it. But as I sead A pro boat designer will come and do the math and then we'll see:cool:
    Whats facinating is your "knowledge" without seeing the boat? perm you sead the planking couldn't be more than 20-30mm planking based on what? Now I tell you it is at least 30mm and then some...If you like I can post some more pic's from different angels on my steel hull?!
     
  10. evantica
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    evantica Senior Member

    Kind of interesting is : As you can see in the "progress photo" there's an "outtake" for teh prop. I decided to close this "propspace" as seen in the other pic' What do you think this will ad, for sailing purposes? eg. make it worse?
     

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  11. Perm Stress
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    Perm Stress Senior Member

    Part of my work is initial designs of ships and boats. At that stage, very scarce information is usually available. So it necessary to make weight estimates, based on overall dimensions and similar, very general and not accurate information.

    As it was a sailboat originally, so much the better. It is not apparent from the photos, as there are many motor boats in Scandinavia with similar hull shape of any size and age. I have seen lots of them in Denmark and Sweden too. Than there is volume in hull to take ballast. Than the hull shape is adequate for getting enough stability for efficient sailing.

    I did take a look at Your tread about building progress. There was a few photos of original boat You are starting from.

    As you see, my guess about planking in about right. It was based on the length of 8.5m. Boats this long rarely have planking more as 30mm or less than 20. Below 20is too weak, above 30 is too heavy.

    Than steel plating will have weight as (8t/m3)/(0.7t/m3)*4mm=45mm of Oak planks. Still overweight of ~50%. It is not entirely catastrophic, but still a thing to consider.

    Because here a spiral could start: more weight need more sail area / bigger engine to drive it >>> bigger sails need heavier masts and heavier ballast, bigger engine is heavier and need more fuel >>> resultant bigger overall weight require more sail area / bigger engine.... and so on.

    In order to break this spiral, something has to be done: either some of the weights reduced drastically, or expected speed (sailing and powering) / range under power set at some much lower level as was originally expected.

    I am not trying to discourage You from Your project in any way. I could only applause Your desision to consult a NA. Simply I did see (in the flesh, not Internet or magazines) more than a couple of boats turned out radically different from what was expected at the start of building "without plans". All of them were grossly overweight, grossly underspeed, one of them had close to 0 initial stability -with crew on deck in CL, the list was ~5 degrees port or starboard, at random. Many had systems (fresh/waste water, fuel, engine cooling even) only functional at the dock. Authors of all of these boats did not consult any NA/boat designer, or did not follow their advice, or did show a boat to designer when everything was ready and no real changes possible.
     
  12. Perm Stress
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    Perm Stress Senior Member

    Prop still need a space. If this space is given as cut out in the rudder, it will increase force on the tiller / steering wheel several times. Or lower rudder bearing will need to be supported on rather long extension, to have rudder rotation axis close enough to its center of pressure. In any case, aperture for prop will be here, unless twin engines or outboard motor on the quarter (on the bracket) are installed. And of course, this aperture do no real good for sailing properties.
     
  13. evantica
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    evantica Senior Member

    perm stress thanks for your consern! Have to say I'm not looking for a fast sailer. I would much rather have a heavy, slowgoing, nice movment kind of ship. I will also/ probably put on a Gaff rigg in the future, as I learn more and more about them. About the engine...this is a bit of dilema. I don't know what, or even if I shall have one??? Think the price of an engine is to much for me...not sure yet?! Purhapse I can do an arrangement to an outboarder, on the rear side of the boat?! Have to figure this out in the future...
    I also tries to figure out an alternativ deck on the boat??? I am thinking about the weight, purhapse a wodden one is lighter and even better ??? a plastic??? hm...why?!: Don't want that much weight on top of the boat (steel) so...
    And:) :) :) Today I was a way and bought a new Welder, yes expensive but good enough for almost anything:D
     

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  14. Perm Stress
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    Perm Stress Senior Member

    Sailing without an engine is great fun an perfect school of seamanship, boat handling, courage and patience. However, it is necessary to be free from anything resembling tight schedule. "Yachts do not have Estimated Times of Arrival, they only have Destinations". If your main base is far from the open sea (somewhere in the Skerries), it will be painfully slow to sail those last 10 or 20 miles. Will it be acceptable to devote, say 3-5 days to travel from Sandhamn to Stockholm? It is quite normal to have Force4 at sea and Force 2 in the Skerries. Or Force2 at sea and random puffs in the Skerries. As this boat is not going to be excellent "flautenlaufer", closeness of main base to open sea (read strong and steady winds), simplicity and sufficient width of approaches for maneuvering under sail will be a real concern.

    An outboard on the quarter will only function in almost perfectly flat water; in this case, the question of windward efficiency receive an entirely new level of importance.
    Tho extremes have to be considered:
    1) almost no wind, with current setting You towards rocks, shipping lane, etc. In this situation, outboard will help, provided that there is no swell running.
    2) heavy wind, above Force 6, driving to rocks, shore, shipping lane, etc.. In this situation, anything less than oversize inboard engine with good (large 3 blade, slow turning) propeller will not help. Unless You have built-in windward performance, adequate storm sails, boat handling skills to make it to weather in gale force conditions by sail alone. Under performance I do not mean stellar speed or close-windedness. I mean ability to reliably gain considerable ground to weather in most any imaginable wind and sea conditions. this is not necessarily much, example, if in Force 8, boat is capable to make 4 knots at 60 degrees to True Wind (leeway included), it is still acceptable. At least in the Baltic, it is hard to imagine situation, when this kind of performance will be not sufficient to keep out of real trouble.

    The bonus of engineless sailboat is greatly increased performance under sail in any conditions, from Force "0.5" to to Force "Snap Your Masts Off", especially close-hauled. I know first-hand accounts of 9m boat with 3-blade fixed prop haviong same windward performance as 6.5m boat with no engine or propeller, eperienced in race (i.e. boats equally well handled). So there physics of sailing are in favor of "pure" sailer: no prop (and no aperture) -less drag, more speed, better pointing, nicer feel on the helm.

    It is not to discourage You, it is to weigh up the possibilities. If You decide to go engineless, I will applaud to it.
     

  15. evantica
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    evantica Senior Member

    everything you sead is absolutley true! But it all depends on the income/ money earned/ affordable?!. I will not make this an option/stoper to not build my circumnavigator. But I will have to make a "dicition" soon before I continue building, else it'll be to late! so lets see...
    And Thanks Perm stress!
     
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