Reverse Engineering (conversions And Modifications)

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

  1. viking north
    Joined: Dec 2010
    Posts: 1,868
    Likes: 94, Points: 48, Legacy Rep: 1146
    Location: Newfoundland & Nova Scotia

    viking north VINLAND

    Ok, TAD, Now this is getting scarey, i understand and comprehend every thing you say. I have already done a trial fit of the engine, fuel tanks, and mock up of wheelhouse, galley, heads, so once i present the lines and a rough scetch of what the superstructure and interior layout as i what i think will work, that should help me on the ballast CG and how it is installed, spread out or more concentrated close to the CB. And again in case i don't say it enought , Thank you, Geo.
     
  2. DCockey
    Joined: Oct 2009
    Posts: 5,229
    Likes: 634, Points: 113, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    Not applicable for a power only boat.

    The balance I was refering to is between the aerodynamic forces acting on the sails and the hydrodynamic forces acting on the hull. Fundamentally different than how the boat "trims", ie its fore/aft attitude when floating.
     
  3. DCockey
    Joined: Oct 2009
    Posts: 5,229
    Likes: 634, Points: 113, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    Have you estimated the mass (weight) of everything excluding the ballast, and then calculated the resulting center of mass/gravity without the ballast based on the mass and location of each object? Tedious but until you do so you won't be able to figure out where the ballast needs to go.

    The alternative is to go ahead and build without a reasonable estimate of the final, complete mass and CG. The builder hopes that once the boat is afloat they will be able to move and add/subtract enough ballast and other items for the boat to trim reasonably close to the desired waterline. For a one-off build the probability of success is questionable.
     
  4. viking north
    Joined: Dec 2010
    Posts: 1,868
    Likes: 94, Points: 48, Legacy Rep: 1146
    Location: Newfoundland & Nova Scotia

    viking north VINLAND

    I have gone thru this twice on prev, conversions and both boats ended up on their envisioned waterlines(one was 1/2 in higher in the stern) as painted on in the shop just from my looking at the hull and Guestimating them, now whether their Longitudional CG lined up with their CB i can't say, however neither vessel seemed to have any bad habits so to say.Both floated perfect transversely.I have already done a good trial fit of the heaviest items (engine, fuel tanks, water tanks) and have done a good mockup of the superstructure and interior so the calculations of mass and location would not be too difficult say within 90%accuracy.Iam an ex open Atlantic fisherman, an experienced boat builder but old school and i have what i think is a very potential hull . While it is not going to be a designed build from day one it will fufill one item in my bucket list and that is to build from a set of specs and understand what they are asking me to do, thus the importance and much appreciated education i am getting from this forum, again Thanks, Geo
     
  5. Scunthorp
    Joined: Dec 2010
    Posts: 122
    Likes: 5, Points: 0, Legacy Rep: 11
    Location: Halifax

    Scunthorp Hull Tech

    Cheers Steve he has done a "great conversion" and we are talking off line. I have posted an article which appeared in "Good old Boat" to inspire and provide hope. Things seem to have gotten quite civil around here nice to see sincerely John
     

    Attached Files:

    • GOB1.jpg
      GOB1.jpg
      File size:
      393.7 KB
      Views:
      361
    • GOB2.jpg
      GOB2.jpg
      File size:
      455.3 KB
      Views:
      379
    • GOB3.jpg
      GOB3.jpg
      File size:
      446.7 KB
      Views:
      357
    • GOB4.jpg
      GOB4.jpg
      File size:
      451.5 KB
      Views:
      278
  6. DCockey
    Joined: Oct 2009
    Posts: 5,229
    Likes: 634, Points: 113, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    When a boat is floating at rest the CG will be in a vertical line with the CB - basic physics. Whether they are the CG and CB that were guessed at or calculated is a different question.

    If you have confidence that you can envision with acceptable accuracy where the actual waterline will line up and are willing to live with the results then you don't need to do any calculations. Many designers and builders don't have that ability, particularly without a lot of experience with very similar boats.
     
  7. viking north
    Joined: Dec 2010
    Posts: 1,868
    Likes: 94, Points: 48, Legacy Rep: 1146
    Location: Newfoundland & Nova Scotia

    viking north VINLAND

    I,ve been around, played in, worked in fishing boats for the first 17yrs. of my life, then after a stint in the air force it started all over again to my present age, which certainly is young anymore.I think the experience of working in small to medium fishing boats on open Atlantic waters certainly gives one a 6th. sense of hulls, loading verses inches of emersion,and certainly gravity so maybe unknowingly it seeped into the brain. Then again possibly more good luck than good engineering. However really looking forward to this build where i am going to build to actual design parameters. Regards, Geo.
     
  8. Scunthorp
    Joined: Dec 2010
    Posts: 122
    Likes: 5, Points: 0, Legacy Rep: 11
    Location: Halifax

    Scunthorp Hull Tech

    Geo when are you going to show us the money mate? I for one can't wait to see some photos. The information coming from the forum now is outstanding and I hope encouraging to those who might have been intimidated by the strong opinions found here. “Can do attitude” certainly helped me when I was serving our countries in the mountains of Afghanistan. Dreams are funny things but thank whatever deity you prefer that we have them. John
     
  9. viking north
    Joined: Dec 2010
    Posts: 1,868
    Likes: 94, Points: 48, Legacy Rep: 1146
    Location: Newfoundland & Nova Scotia

    viking north VINLAND

    John, just completed re doing my hull lines today and added a few intermediates on the ends, dam cold work with plumb bob and tape with bare hands this time of year. Hoping to get them transferred to paper over the next week or so, very busy with my regular job on a big renovation for a guy from California. Thought i might post a few of my prev. builds along with still seeking info to keep the thread active although as you say the quality of info on the forum now outstanding, especially the ability of the posters to express what is such a dynamic topic into laymans language. A vessel under the influence of the variences of wind and water is far more dynamic than an aircraft in flight, air being reasonably stable. Anyhow "UP THE KIBER" Geo.
    P.S. Great article on Chris Bauer's conversion, wow he did a good job, Funny world, He a German converts a lifeboat and sails it from Europe westward across the Atlantic to north america and me a north american(Newfoundland, Canadian) sold my lifeboat conversion to a German couple and last i heard they planned sailing it eastward from north america across the atlantic to Europe. Ships passing in the night, Reality is stranger than fiction.
     
  10. BertKu
    Joined: May 2009
    Posts: 2,521
    Likes: 47, Points: 58, Legacy Rep: 223
    Location: South Africa Little Brak River

    BertKu Senior Member

    Geo,

    If you like to have the excel files, I gladly e-mail them to you. All what you have to do is, to overwrite my information and add zeroes to what is not applicable. I you want, I can do it in inches and feet for you, instead of milimeters, centimeters, decimeters and meters. Except the Rigthing arm curve. I did not receive any comment, but I have to sort the input for the formulae out. It is not usable as it is in its present form. Do you have excel on your computer?
    Bert
     
  11. Scunthorp
    Joined: Dec 2010
    Posts: 122
    Likes: 5, Points: 0, Legacy Rep: 11
    Location: Halifax

    Scunthorp Hull Tech

    Bert I never thanked you for those files mate thanks a lot John...
     
  12. BertKu
    Joined: May 2009
    Posts: 2,521
    Likes: 47, Points: 58, Legacy Rep: 223
    Location: South Africa Little Brak River

    BertKu Senior Member

    John, What you have downloaded are in a Jpeg form, because Jeff is trying to sort a problem out I am having with the forum website settings. If you would like to have the actual Excel files, no problem, i e-mail them to you. They should have all the excel formula's in them. Please do not use the actual CURVE file, I have to do some more work on it. The others are fine, as long you understand what I have done.
    a) in some instances I use the actual Stations as per drawing from the designer. Because the hull is a very stable old fashioned long V type of hull, I was able, quite accurate to calculate the area. I could not use the Simpson rule, as the stations where not in equal 10 pieces.
    b) in other instances I use the LOA divided by 10, and in that case I could use the Simpson rule.
    c) as a result there maybe a small discrepancy, but it should not affect my conclusion on stability at the end of the day.
    Bert
     
  13. frank smith
    Joined: Oct 2009
    Posts: 980
    Likes: 14, Points: 28, Legacy Rep: 185
    Location: usa

    frank smith Senior Member

    While adding ballast , does this give you the opportunity to tune the pitch damping to some degree?
     
  14. viking north
    Joined: Dec 2010
    Posts: 1,868
    Likes: 94, Points: 48, Legacy Rep: 1146
    Location: Newfoundland & Nova Scotia

    viking north VINLAND

    Bertku, Thanks for the offer but i wouldn't know what to do with them, However i see you are forwarding them to John (Scunthorp) so maybe i can have him play with my hand drawn lines when they are ready. Just discovered he lives fairely close to me and he is in the process of converting a lifeboat, something i did some years ago and i'm going to pass along the don't does from my experience on it to him. Tnx. Geo.
     

  15. viking north
    Joined: Dec 2010
    Posts: 1,868
    Likes: 94, Points: 48, Legacy Rep: 1146
    Location: Newfoundland & Nova Scotia

    viking north VINLAND

    Frank, thanks for that e mail wanted to respond but couldn't figure how to do it, have to ask my brother in law to come back to show me how to post photos again, I'm a cave man when it comes to computers but learning slowely. Good question on the post, I think TAD, Gonzo, and D Cockey all touched on it, is also something i am interested in, I think hull shape plays a big role, maybe they could expand upon it. Geo.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.