Reverse Engineering (conversions And Modifications)

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

  1. breschau
    Joined: Nov 2010
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    breschau Junior Member

    This thread is still confusing. It is not clear what the project is. It is not clear who the OP is. It is not clear why they are pissed off for advice after explicitly asking for advice.
    Do not give up just now, its getting funnier with every page:D
     
  2. Scunthorp
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    Scunthorp Hull Tech

    Whatever way you like to do things. Its ok somewhere
     
  3. viking north
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    viking north VINLAND

    Ok, time to get caught up, TAD, thanks so much for that thread link, Eric while so well educated and knowledged has that wonderful gift of being able to put it into laymens(me)terms. About half way thru and some info off in left field but learning alot. Gonzo, was hoping that someone would point out that CP alone might not be enought but would also expand on other indicators and partake of their knowledge. Example displacement to length ratios, reference material,Aero/Hydrodynamics of sailing, by Marchaj, 2nd. ed. page 155 if you would like to read up on it. And again we drive home the point stated way back in step #1 of this thread, provide good photos or better yet arrange for a Designer to view the hull, even before purchasing if possible.Ad Hoc, will supply that info shortly.PAR my good man, great experience at a young age, me thinks might have been the driving factor for you to become qualified in this field from which we all gain. Just think all for the price of a converted life boat, smart man your dad.Been to Eustis many times, Antique cycle meets, I am an Indian groupie. Battan, exactily the point as per my prev. post. Ok, as a result of a CP# 60, a Displacement to Length ratio #400 Mr.X has decided to convert his hull into a motorsailer and to install a full keel. Now i realize that installing a full keel will reduce the CP but this is still a heavy, full hull and my question is what is the Longitudional Reference used when determining the central location of the ballast mass. Is this a valid question as i have always done this by just looking at the hulls shape as to it's volume fore and aft below the waterline and went with my gut feeling as to it's Center and installed the resin encapsulated auto wheelweight ballast using that as the reference.(My system, i install the keel bolts, keel shell and ballast with the hull inverted) I know this sounds crazy but in my past two builds once launched they didn't need any trim ballast, then again i was working with almost symetrical hulls(double enders) and the big challenge was to ballast them in such a manner that the stern is approx, 1 foot more emmerged than the bow. I know i'm going to get 10 answers here to different levels of civility and engineering but can someone out there supply a good basic answer, I suspect in engineering terms it is the longitudional center of boyancy as i think thats what i am doing , Ok my armour is on, Geo,
     
  4. gonzo
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    gonzo Senior Member

    Symetrical hulls are fairly easy to balance. Calculating the CB only takes a measuring tape. They usually keep the balance when heeled too. I think that any reverse engineering of a design should start with drawing a set of lines.
     
  5. viking north
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    viking north VINLAND

    Breschau, Boys get serious, i'm trying to lean something here, Brescheau, that could be the problem i am not asking for advise but technical info, what the f---K difference does it make weather it's a conversion or a straight forward build, it's good info. Once i am confident with that' i would like to present an actual build where by i hope to receive more good info for myself and others out there. I chose a conversion senario to learn the process, understanding and language so to better communicate with the Qualified people on this forum. Like i said it's one thing to get technical info but another how to apply that info hands on, thats the bridge i'm trying to cross so one more time boys smarten up, if you can't help then dont try to destroy.I really would like to do my build thru the great knowledge that exists here , If not the hell with it i'll find a way to do it thru another means and we would have all lost. Geo.
     
  6. gonzo
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    gonzo Senior Member

    Let's get down to basics then. What is the specific question and the parameters?
     
  7. viking north
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    viking north VINLAND

    Exactly, Gonzo, and as soon as i become a little better educated with and how to apply the magic numbers thats what i intend to do, a real build,photos and all,and i would be very pleased and appreciative if you could expand and give me your input on the question( not being mean here, just asking for help). My logical mind says regardless of hull type the reference to work from should be the longitudional center of boyancy, am i on track, If i am my next question is given the hull lines, is there a fairley easy way long hand to calculate the distribution of the weight fore and aft of this point to maintain the CB. Or would it be more realistic to process this thru a designers computer program. The other thing i seem to remember in my long lost memory is instead of spreading the ballast longitudionally over the entire length of the keel, volume permitting it's more effective to concentrate it close fore and aft of the CB.I think thats now a total of three questions. Tnx. Geo.
     
  8. BATAAN
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    BATAAN Senior Member

    I guess I failed to convert a lifeboat.
    In 1969 bought a 22' steel lifeboat for $200. Put in floor timbers for a keel, then decided it was a lousy idea for a sail boat so made a little house boat out of it and lived for free on anchorage for a year. Sold boat for a good profit and learned many lessons. Success through failure.
    Aspiring to be stupid and irritating.
     
  9. frank smith
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    frank smith Senior Member

    It appears that everyone here is more Qualified than you. Do you own a tape measure and a level?

    Have Fun.
     
  10. Pierre R
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    Pierre R Senior Member

    Now that we have dropped the budget requirement I will say that every project has a budget. With that said and the reason for build is that building is the exciting part and the satisfaction we are down to suitability before build.

    If you have developed a reasonable SOR then all you need to determine suitability is someone very knowledgeable to take one look at the hull. In about one minute that person will have a damned good idea if the hull has a chance of doing what is in the SOR. Now it the knowledgeable person says yes then we are down to taking a set of lines and making out a plan.

    In the long run the NA's time might come to more money than the hull but that may be well spent as the time that can be saved may be substantial in the long run and the project may have suitable resale with good documentation.
     
  11. frank smith
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    frank smith Senior Member

    A good 30' sailboat can be picked up for $5000. in the US right now.
    ,
     
  12. Pierre R
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    Pierre R Senior Member

    Good is a matter of opinion.
     
  13. frank smith
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    frank smith Senior Member

    How about a S+S designed Tartan 30 for a start,
    Might get one with good interior , good set of sails , and in some cases a fairly new diesel.

    Right, lets get back to converting the life boat .
     
  14. Pierre R
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    Pierre R Senior Member

    Relevance? The lifeboat is somewhat of a hijack. Used boats are the way to go for sure IF the "tight budget" is in the mix.
     

  15. rwatson
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    rwatson Senior Member

    Hey what fun. Lots of good advice, but when the naked lumberjacks start appearing, then you know the party is humming :)

    Just a pot stirring idea - if I was wrecked on a desert island, with a lifeboat hull and a container full of tools and sails and old masts, I would bet I could sail the lifeboat to civilisation without professional advice, as could most desparate and innovative human beings.

    Of course, if I wanted insurance on the boat, a guarantee of sailing performance for an accurate estimate of when I would arrive at my destination ( because I have to have enough stores to survive) , then I could be in serious trouble.

    If the island were populated by naked lumberjacks, it might all be just too much of a bother.
     
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