Reverse Engineering (conversions And Modifications)

Discussion in 'Boat Design' started by viking north, Dec 25, 2010.

  1. Scunthorp
    Joined: Dec 2010
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    Scunthorp Hull Tech

    I like this last post of Berts
    Hi Bert are you working on a project connected to the topic in this thread or just doing some calculations for fun? I understand that books can be difficult I have "The principles of ship stability by brown son and Ferguson Ltd" It is a heavy bit of work but all the basic information is there. I don’t think that my project is that complicated. I think that a good investment of time and consideration should go into fitting out. “ Look I want to be honest, anybody who is ever planning to reduce a boatplan by a percentage over the 5% is a lunatic. But I have gone that far” We do torture our selves. John
     
  2. Scunthorp
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    Scunthorp Hull Tech

    Use a wide angled lens so as to get a truer depiction.
     
  3. Scunthorp
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    Scunthorp Hull Tech

    Downloading delfship as we speak
     
  4. viking north
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    viking north VINLAND

    Bertku, no problem, this thread was an idea to create a make believe(not real) boat conversion or continuation of a discontinued build, which in both cases there are no design papers available and the idea was to use a make believe person, Mr.X and show the process of "reverse engineering"(has to be given some name) to create design info to do the conversion or continue the build. The idea is that MR X is an amature but has some boat building experience who is operating on a tight budget and wants to engage a designer to maximize the outcome of his project.As such the thread not only shows the steps in the process but also gives info on how MR.X can supply info to his chosen designer to keep costs down. Thus far in the thread he has supplied photos or taken his designer to see the hull(make believe) Weighed the hull and taken off it's lines and has passed all this info to his designer to plug into the computer to obtain the magical numbers(my take)'We are about to proceed from there. I wanted to create a thread with input from the dreamer right up to the professionals. It's been a bit of a battle but thanks to some informative openminded positive thinking people i can see it coming to an end. The thread was to help those people out there that dream of owning a boat, can't afford an initial big cash outlay to buy one but can scrape up enought to buy a hull to convert or a discontinued build and over a period of time beg, borrow, barted and sweat to complete it.Will the result be perfect, maybe not maybe so, but certainly it will have a better chance with help from a qualified person and the educational input from this forum. Geo.
     
  5. BertKu
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    Location: South Africa Little Brak River

    BertKu Senior Member

    Hi John, I am dead serious and already planning this project for quite some time. After Tom Lathrop explained what happened, if somebody reduces a boatplan by a percentage, I had to find out for myself, how bad the stability will be and whether it could be corrected. Tom gave the example with 50 % reduction. Because I only reduce the plan by 13%, I had to pull up my sleeves and start learning from scratch. I am pleased I did so, even if it is a tremendous lot of work and reading. But now I am pleased that all the configurations is done on excell and by manupulating inputs, I am able to see what can be done about the stability. But it looks bleak, except if I drop the idee that the boat shall be turning back on its belly at all times. But this studying has allowed me now, to understand the basics better. I need to present all those calculations in anyway to the authorities, if I want to take a boat onto the sea. I don't know how your officials are, but here they are very strict.

    It will be for me, a 2 to 3 year project. Thus the few months of studying, keeps me young.

    Yes, I did torture myself, but it is absolute an eye opener, to see that even professionals not allways speak the same language. per example. Most of this forum state that a twin blade propeller is the most efficient. During reading I read on page 95, that 3 blade propellers are more efficent. Thus if somebody tells me to jump of the Eifeltower, I will politely accept that, climb the Eifel tower and see for myself WHY I should jump. Therefore Tom, my profound apology, but I had to find out for myself WHY the stability takes a knock.
    If Jeff can fix my up-loading I will up-load all my calculations and my conclusions.
    Bert
     
  6. gonzo
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    gonzo Senior Member

    If someone can't afford to buy a used boat, they certainly can't afford a project. They are much more expensive in time and money.
     
  7. BertKu
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    BertKu Senior Member

    Hi Viking North,
    Yes, I am pleased that you started this thread. Indeed I believe that many youngsters are in that sort of position and also, who has money to waste?.

    This thread could help them to reduce cost, by doing themselves that portion, what is needed for a professional to make a costeffective proposal. Not everybody is a computer fundy, nor an expert on Delftship and similar programmes.
    I have learned a lot from this forum.
    Bert
     
  8. gonzo
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    gonzo Senior Member

    The main problem is the denial of amateurs of the cost of "reverse engineering" compared to buying a used functional boat. If you have a humoungous budget, it is not a problem. However, the proposition is the the budget is limited. Then the "boat project" is not realistic.
     
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  9. Scunthorp
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    Scunthorp Hull Tech

    The Cornish fellow is back. Thanks for that gonzo I like scrumpy mate but not all the time. I just downloaded "Boats: a Manual for Their Documentation" from the “taking lines off” thread it is an interesting read. I am looking forward to seeing Bert’s calculations and conclusions sounds like a work of art.
    Viking I am still trying to figure out what a professional would want and why you would hire one. Perhaps if you get your lines off and give him/her your intended use for the vessel that might help. I am not far enough along to help much still scraping around in the dark. Where are you on NS and are you up for a visit as I would love to see whatever project you might be working on? Well back too it cheers John
     
  10. BertKu
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    BertKu Senior Member

    Fully agree with you, But not everybody wants to buy. In my case, I like to build something myself, go through the process, make bloobs and learn and experiment. There are lots of those people in the world and indeed there are others who should just buy a "previous owned" boat.

    I hope that this thread will give them the basics on what to do and either come to their senses or understand what to do first before they lay out the money for whatever "reverse engineering" object they want to buy.
    Bert
     
  11. daiquiri
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    If you want to talk about costs and savings, then I'm with Gonzo, Landlubber, PAR, TAD and Ad Hoc on this one. If you guys think that you will save money by doing this small part of designer's or engineer's task by yourselves, then I'm affraid you'll be disappointed. Apart that you have a fair chance of doing it wrong, and be the only ones liable for that.

    The only cost saving, compared to a newly-built hull, is related to materials and work hours necessary to build the hull structure from scratch. And that's between 10% and 15% of the total cost of the finished boat. Once you have the bare hull, all the costs are the same for both a newly built and a refitted or converted boat. That's because all the equipment you would put into a converted boat can be put in a newly-built hull too (if one is ready to live with the fact that the old equipment - well, the old hull too - can malfunction or fail at anytime, with no warranty that any quality standard is respected).

    Plus, when you consider that a conversion has the additional cost for the removal of the old equipment, stripping the boat down to a bare hull, thorough inspection and taking the unknown measures, before starting any work on it, the money-saving margin gets even smaller, if there remains any.

    So yes, Gonzo is right - if you cannot afford a decent and functional second-hand boat, or a buy a project for a new one, then (as we use to say in Italy) you are probably making a step longer than your leg.


    BertKu, it's ok. The important thing is that you are aware of additional costs (respect to a newly built hull) implied in that process. Once you realize and accept that, go ahead and make your dreams come true. :)
     
  12. gonzo
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    gonzo Senior Member

    That is my point. Not that it can't be done, but that it can't be done if you have a limited budget as the thread poster specifies.
     
  13. viking north
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    viking north VINLAND

    Gonzo, you're back now give up that foolish logic and join the boys for some fun and help pass on some good knowledge(i know you have some in there). Did you read my post to TAD re all that logic. Regardless in this post no one is actually spending money, it's not a real build. It's an informative process that teaches the basics and can be applied to a new designed build, a conversion, a completion, preserving the design info on an old rotted out traditional. An informative tool that helps new guys maybe not to piss around with conversions or continuing an interrupted build, Christ some landlover might use it to impress a young female sailer and get lucky, think about it, apply your positive input in the actual engineering, I.E. what the magic numbers represent and how to use them to benifit any project. I know alot of this is just basics but remember when grasping basics gave you confidence, help do it for someone else. Geo.
     
  14. viking north
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    viking north VINLAND

    Daiquiri, not you too, whats with you guys, do you both work for the bank and are afraid some guy might withdraw his savings and have fun pissing around with a richmans passion while having a cold beer. Get off the logic trail, it's not logical to mate with one woman for life either but we do it. And don't tell me we don't spend money there. You guys got the education, I'm just a self taught builder sometimes a dabbling designer, I've been that guy that was cash strapped and started with a conversion, still in the same boat after three. Without that past, the experience, pride of building with my own hands, the 40yrs. of sailing those converted craft i wouldn't be the craftsman/sailer i am today. Every cut building a boat is three dimensional which in turn develops three dimensional thinking and vision,(few people have it to any degree) which is the best right hand man any designer can work with especially if there's a good red dry wine on the drafting table. Geo.
     

  15. Tad
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    Tad Boat Designer

    Viking.......

    Realize that if you weigh the hull with a crane or scale you still do not know anything about the location of CG, it must be located in three dimensions, (longitudinally, transversely, and vertically). Now you only need this info if you are trying to achieve balance, trim, stability, or a particular flotation.

    Again if you have the lines plan (hand drawing or computer model) you can launch the boat and calculate weight, longitudinal and transverse CG, but not vertical CG, which is the important one for transverse stability calculations. To get VCG you need to (with the boat in the water) do an inclining experiment. This involves heeling the boat with fixed (known) weights a measured distance from CL and measuring the heel angle very accurately (2-3 millimeters).
     
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