Calculating ballast for a motorsailer

Discussion in 'Motorsailers' started by Annode, Sep 22, 2019.

  1. Annode

    Annode Previous Member

    Aaaargh OK... let me see if I can put this another way.
    Yes, the boat is inherently very sea worthy *BUT* it was was designed to be laden with fuel, heavy engine, 100s of tons of frozen fish, all LOWERING the CofG. It was not designed for a mast and sail forces. It will not need tons of fuel and big heavy engine so all that ballast is gone. the superstructure would be heavy and high adding to the problem. The Hull design is inherently stable at LOW angles. As discussed in AD Hocs posts, this at the sacrifice of roll resistance at higher angels (like heeling from sailing and a knock down)

    IN the thread about wingnuts everyone was appalled that the owner took opinions, removed ballast and subsequently had a boat that could not withstand a combination of events that a sailboat should have been able to withstand. He did not do any calculations. I am not so arrogant and Im not going to find out the hard way that my CofG was raised such that i find myself unconscious in the water!

    This thread and the others was spawned by a boat I considered and rejected. Now it is a theoretical discussion of the mechanics of stability as it applies to a large heavy steel trawler hull. The Videos in the above thread are not intended to display an emotion of fear, simply that large heavy boats mean NOTHING to a big sea. Nothing. If your calculations are not in the ball park, you will be swimming. I note that the Queen Mary survived that Rogue wave at an angle approaching 60 deg. That is an incredible testament to the engineering that went into the boat. Can you imagine the loss of life if that had been capsized? I am not obsessed with this, but as my grandfather used to say, plan for the worst, hope for the best.

    I want to run some numbers. Thats it. Its not rocket science. Not going to space or flying at 30k feet. Just want to run numbers to find out how such a conversion affects the stability at larger angles of heel and calculate a keel and weight sufficient to enable righting force somewhere around 60deg. Thats it. Yet here we are almost at page four and..... still no idea how to do this even with a bad approximation.
  2. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Because it requires facts and data and not one liners...and cannot be done with mere 'words'.

    Stability must checked be very carefully. And since you do not even know how to even get some feel or "approximate" this in a qualitative manner, should be sufficient enough of a red flag to you that you should not even attempt to do it. Considering your 4 pages of, at times, paranoia on the subject.
    Employ a naval architect... then you'll know what is or is not possible.
  3. Annode

    Annode Previous Member

    Ad Hoc, This kind of response "hire a naval architect" is not helpful. Characterizing my posts as "paranoia" is insulting. Implying that the ONLY way yo do this is "very carefully" is factually inaccuate, and suggesting that this is a "red flag" and concluding that I should "not even attemot to do it" is disengenuous.

    I am new to this forum and, as always, it takes time to understand the characters in a forum and the usefulness of their contributions. I have been a little puzzled by you until now. Clearly you have qualifications and understand the physics of boats well, but this kind of response is simply not helpful and frankly condescending.

    If I had purchased such a boat, and was moving forward with such a project, I would indeed engage a qaulified Naval Architect (with a better attitude) to calculate these things precisely. But I havnt. As I have stated, this thread is about HOW to estimate these things to get a sense of the feasability of such a conversion, the efficiency of such a conversion and the sea worthyness (in this case as measured by stability; specifically righting from heel and knock down events!) of such a conversion WITHOUT the risk of loosing large amounts of money and wasting years of life.

    This is a public forum. I am asking for a discussion of the topic, not a free workup of a a specific case. I believe Trawler designs are much the same in their class of hulls and general specs and that these are well understood. The hull material is well understood. Sailing calcs are well understood. I believe it is not a stretch to make some rough approximate calcualtions using rough guidelines like; 60 deg of heel! You dont have to be able to use complex math to get a sense of this. You do not need exact measurements to be in the ball park. While this mght offend your sense of accuracy, it helps those of us that must put down real money, in a real world, to understand if a project is going to be fruitful.

    If you do not want to contribute to this with your extensive knowledge, thats fine, but please refrain from casting aspersions.
  4. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    Some time ago I wrote in my notebook of interesting notes the following sentence, which I don't remember where I read : "I am not impressed by your money, position or title. I am impressed by how you treat others. It´s nice to Be Important, But More important to Be Nice¡"
  5. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    That is because, like many that come onto this forum, they do not like to hear cold hard facts. It goes against their preconceived ideas and notions and they usually just want someone to sing from the same hymn sheet as them. Whether you like my blunt replies matters little to me, as i'm trying to grab your attention so you will listen. Your safety and your life, and that of others, is far more important to me than your bias and polemics.
    Naval architecture is based upon facts…not emotions or feelings or belief!

    It has nothing to do with my ‘want’ or not.
    The audience is NOT listening …however, if you wish to arrogate the stability of a vessel … that is your prerogative. Just like those in the K35 thread did. How did that work out…
    Last edited: Oct 11, 2019
  6. gonzo
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    gonzo Senior Member

    Do you own the boat? In that case, a stability test is easy to do with a pendulum and weights.
  7. Annode

    Annode Previous Member

    its a 200 ton 30m steel hull. How much weight are you thinking?
  8. Annode

    Annode Previous Member

    Sheesh, any other words you want to put into my mouth?
    preconceived ideas - Nill
    hymn sheet - none
    cold hard facts - few and far between the rhetoric (hire a naval architect)
    grab your attention - I think you got that three pages ago
    you will listen - ears wide open since page one...
    Your safety and your life - wasnt that my point from the videos you accused me of being in fear?
    Naval architecture is based upon facts - yes please )))

    Requesting facts on how to calcuate ballast weight (first clue was the title of this thread)
    thats *HOW* .... not more rhetoric or hyperbole... ya?
  9. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    So, let's review the facts.

    So, no lines plan and no weights of centres....just theoretical.
    Thus no facts...just an endless circular debate about the not having any facts.....yet wanting to know how to "calculate" them when you have nothing to start with.

    Your only riposte - shoot the messenger.....ggeesssss!!! o_O
  10. BlueBell
    Joined: May 2017
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    BlueBell . . . . .

    Absorb the information given and ignore what you perceive as personal attacks.
  11. Annode

    Annode Previous Member

    >you have nothing to start with.
    How different do you think trawler designs are at this length and weight in the last say 50 years?
    Here are the detailed plans:
  12. Annode

    Annode Previous Member

    >Absorb the information given and ignore what you perceive as personal attacks.
    Its not personal attacks it "why is that the question" and dont you know z y and z detail that are required for fourth order accuracy. Its absurd.
    Where is the center of lift on a 747 about 1/3 chord. Where is it on a Cessna... about 1/3 chord
    Where is the C of G of 30m of steel plate in the shape of a Trawler? About 1/3 height I am willing to guess, at least good enough for govt work!
  13. gonzo
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    gonzo Senior Member

  14. TeddyDiver
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    TeddyDiver Gollywobbler

    About is not precise enough, sorry. You haven't stated (or I may have missed) where're you going to sail, which determines how much heeling the hull must withstand. So you have basicly nothing.
    To get started (that is if you are not going to hire a pro NA) measure the hull as accurately as you can, get CAD software for boats and ships and redesign your vessel there with all the gear and weights included. Study some dozen NA books on the way and discuss things you don't understand with experts. Just in few years you are able to do better than about..
    BR Teddy
    Ad Hoc likes this.

  15. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    And that says it all .... such hubris!

    Seems 'about'...appears to be 'good enough' for some!
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