Reverse Engineering (conversions And Modifications)

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

  1. viking north
    Joined: Dec 2010
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    viking north VINLAND

    First no good books are available on this topic, and i want this to be an ongoing informative and educational thread that involves all sides of the equasion, Dreamers, backyard builders, pro builders, self taught and formal educated people involved in boat design. You notice i give credit where credit is due in my listing of the above as was the case in the evolution of the modern seagoing vessel. Before making the next statement i must qualify i am a combination of the first four catagories above as many of us are but to get the most out of your conversion or modification i stress that in the search for safety, function, appearance and resale value (you will recoup your investment)spend the extra dollar and involve the input of those engineering and design people that have the education and resources to give info and guidance to make the most of your project.
    Ok lets get to the topic at hand by presenting the following scenario to our fellow forum engineers/designers. We have obtained a structually sound hull that has the appearance it could be converted into a sailing craft or an incomplete sailboat project that has the hull completed but no keel or ballast installed. No design info can be found. First we want to know if the hull would make a reasonable sailing craft, motorsailer, or not applicable to either. Keep in mind our finances are tight, what info would you need to start the project, in otherwords step #1.
     
  2. hoytedow
    Joined: Sep 2009
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    hoytedow Wood Butcher

    Please post some pictures so we can assess hull type. Merry Christmas.
     
  3. Scunthorp
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    Scunthorp Hull Tech

    I for one am interested. I have an old Polish lifeboat hull fiberglass quite thick and I am in the process of converting it into a motor sailor. I am in “well over my head” and I know there is plenty of engineering expertise here so here we go. I am interested in some of the basic questions like how to establish a base line how I calculate her existing volume and then what I might need for ballast. It’s a big fat boat hull which I have to put a keel on for sailing and deck over. I wonder how high the deck should be. I think it should be a 60/40 motor sailor but I am determined to make it the best I can. So reverse engineering figuring out the unknown from what I have shouldn’t be too hard should it??? Oh and a very Merry Christmas too all.
     
  4. Bruce46
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    Bruce46 Junior Member

    You can put lipstick on a pig but you still have a pig. Having said that, I know that there have been many adventuress souls who have tried to recreate a boat from someone’s cast off, generally you wind up with something that others scorn.

    Power boats are designed to work best under power and lack many of the attributes necessary for a sailboat, i.e.: ballasted keel, adequate rudder, reinforcements for chain plates, etc. Sailboats on the other hand have all that unnecessary stuff if they are going to be used as a power boat. Dragging around a deep keel means there are a lot of places you can’t go. Without the masts and rigging to balance out the weight in the keel the boat would be VERY stiff and uncomfortable, additionally the deep keel adds a lot of drag and decreases fuel mileage.

    We’ve all heard the old adage; ‘The jack of all trades is the master of none.” This is certainly true in the case of boats.

    If your goal is to resurrect a boat don’t try to make a male out of a female. I believe that there are enough unwanted boats of either flavor that would benefit from a refit/update/restore.
     
  5. gonzo
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    gonzo Senior Member

    If your finances are tight, the best advice is to forget it. You are just another dreamer that will drain his bank account paying for storage but will never be able to finish the project. Buy a used boat and go sailing.
     
  6. Scunthorp
    Joined: Dec 2010
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    Scunthorp Hull Tech

    Sorry if I am wasting our time. I was hoping for something from a naval architect or someone who has some knowledge of stability calculations and boatbuilding. Who could answer some of the technical questions I have. I have several boats this is just another project. I think I am more interested in an “informed and educated” understanding of reversed engineering than just another dull opinion. I am converting a lifeboat into a motor sailor has anyone done this or have anything useful to share in terms of working the information I require. Merry Christmas indeed…
     
  7. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Hello, I think it would be interesting and informative for the rest of us if you could show few pics of boats you want to convert. Without, it is hard to tell more than few generic observations on the feasibility of your projects.
    Cheers!
     
  8. cthippo
    Joined: Sep 2010
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    cthippo Senior Member

    I really wish people would stop giving this sort of "advice"

    No doubt, building or restoring a boat can be a huge time and money sink, but if someone understands that and wants to try anyway, we should be supporting them by sharing what knowledge we have.

    Never tell someone it can't be done, tell them how to do it instead!
     
  9. Ad Hoc
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    Ad Hoc Naval Architect

    Firstly….support your hull on hard level ground, check with a spirit level.

    The mark off locations at a fixed and constant distance from the transom in the longitudinal direction, “x”.

    Ensure your boat is then level, transversely, ie not listing to port or stbd, then do the same transversely, “y”.

    Drop a line, with a plumb bob, from each location, longitudinally and transversely and measure the distance from the horizontal level ground to the location on the hull. This gives you a vertical distance.

    Do this for every location. You’ll end up with a table of offsets, from the ground. Use the figure with the lowest vertical distance, and take this value away from all the others, as this becomes your baseline.

    You now have a full 3D table of offsets for your hull, which can be plotted on graph paper and calculate the areas for each transverse section and then “Simpsonise” longitudinally to get your volume and second moments of inertia for stability.

    Or….input the figures into a stability program.
     

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  10. Landlubber
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    Landlubber Senior Member

    "Never tell someone it can't be done, tell them how to do it instead!"........

    ......I am sure gonzo was in fact not being critical, but practical. There are many of us on this web that shudder at the though of another total waste of time and money spent on trying to make a silk purse out of a sows ear......it actually hurts us to see this waste.......we all know of sooooooo many "project" boats that simply suck the life out of the owners (and their families).....in the perpetual dream of the uninitiated....making a cheap "whatever"...

    I guess the answer to the question is that the proposer should sit down and try to understand the enormity of the task and the expense of the result, and weigh up if it is really all worth it, or is it better as gonzo says, to simply go and buy a good second hand boat that can be used without much time or expense.

    On the other hand, if the project owner is determined to go ahead, despite the devastating end results to his financial status and his families well being, then why should someone that knows from the start what the result will be, waste his time and effort trying to encourage this wasteful deficiet to continue....OK, give me grief now, I am used to it.
     
  11. cthippo
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    cthippo Senior Member

    I'm not going to give you or gonzo grief.

    I disagree, but I respect your opinion and I do see where you're coming from.

    I've always been a believer in "go big or go home" and "it is better to have tried and failed than to have never tried". I've tried and failed plenty of times, but I've also succeeded lots of times as well, and so I want to encourage others to try.
     
  12. PAR
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    PAR Yacht Designer/Builder

    Reverse engineering is the absolute worst engineering endeavor, you can possibly submit yourself to. You don't know what the design perimeters were, so you can't tell how well their engineering decisions addressed them, you don't know the restraints placed on the SOR or brief and any results from testing, observation or disassemble will just yield slightly educated guesses, at the real reasons things where done the way they were. Unless the government is paying you several times more the you're likely worth, to reverse engineer an alien propulsion system, then I can think of no other thing more discouraging to employ you time.

    Scunthorp, how did you come to the location, shape and plan form of your Keel? I ask this is light of the comment, found further along in your post. You do realize we like to optimize the appendages for the rig choices made.
    Simply put, you need a professional to workout the details for you. It might be possible for you to get a "student of design" to work up the calculations, but it's not as easy as it might appear. Figuring out the volume of the hull for example, will involve hundreds of measurements. A novice could do this, but not easily. Someone that's preformed this task before will have a much less difficult go of it.

    Lastly, it was a lifeboat which means it'll neither be a good sail or powerboat. You may "convince" it to sail and she certainly could have an engine shove her along, but she'll just remain what she is, a well burdened craft, design to "settle" uniformly as loaded and tolerate unmerciful seas, if the proper decks are installed.
     
  13. Ad Hoc
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    Ad Hoc Naval Architect

    I agree with your sentiments.

    However, there is a major difference between say, as an example, wanting to fly to the moon with a sheet of A4 paper, some glue and a wooden ruler. One outcome is good effort but recognising all you’re ever going to achieve is a folded up bit of paper made into a paper aeroplane which will fly about 10feet, the other being a blind dogged insistence that no one is going to tell you that you cannot fly to the moon with just paper, glue and ruler and you’ll keep searching until someone somewhere tells you that you can...

    If you are unaware of the limitations placed upon your “dream”, owing to lack of knowledge in the field of investigation, and if you won’t listen to the good advice of others who are…, you’ll make serious mistakes and/or loose endless amounts of time and money.

    Keep telling yourself over and over again shall only convince yourself XXX is possible, not anyone else. Recognising the difference between the two is sometimes a fine line…
     
  14. cthippo
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    cthippo Senior Member

    Fully agree. That's why I and many others are here, to collect the info needed to convert dream to reality. Unfortunately the response is so often "it can't be done" or "only a professional can do that, don't even try". None of these drive the process forward.

    In the case of the OP, of course, it CAN be done, but there are inherent limitations on performance doing it that way. You're probably better off getting a used boat than trying to do the conversion, but if you have the hull, here is how you can make the best of it.

    Likewise, I've been looking at hull forms for my kayak tender design. One of the questions I needed to answer was hard chine vs soft chine. I know if I had asked that here the answer would have been "we can't answer because we don't know what you're going to use it for". Instead, why can't people say "well, generally a soft chine is best for sailboats because they heel over a much wider range, while a hard chine is usually best for powerboats, and a necessity for planing hulls." Of course there are exceptions to that statement, but fir 90% of circumstances it's adequate.
     

  15. PAR
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    PAR Yacht Designer/Builder

    I'm convinced there are two types of people: those that try, but are unprepared to have a reasonable expectation of success and those that prepare to succeed. The ones that try, may very well be quite noble, though their exploits are often preceded with the "had they only . . ." comment. Those that succeed most often, if not for dumb luck with isn't reliable enough to count on, do so with research and the resulting preparation this generally suggests in an attempt at success.

    I guess my point is, reverse engineering is a half assed way of doing things and if you can't do it, you can hire someone to do it or spend the next few years researching the various subjects and do it yourself. All I'm suggesting is one of these choices is considerably more practice then the alternative.
     
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