The game is afoot

Discussion in 'Boatbuilding' started by Boston, Apr 20, 2011.

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  1. Boston

    Boston Previous Member

    started painting plywood today so I have a nice white surface to draw on.
     
  2. cthippo
    Joined: Sep 2010
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    Location: Bellingham WA

    cthippo Senior Member

    I'm running 2.6 so it wouldn't open. I guess I should go hunt down a copy of 3.1, but it sounds like Boston has things well in hand and I did learn a few things.
     
  3. Boston

    Boston Previous Member

    Actually I cant make out anything on the print of the transom but the booklet says a 6' radius and thats all the info I really needed anyway so hopefully the stuff on the print was superfluous. I can draw in the radius in plan view and transfer where it intersects key stuff. should work but its the one part of this I'm most curious about. Might take me a bit to figure that part out but its a simple radius so at least its easy to draw. The compound curve of the edge and the idea that I want a nice border of equal dimensions means if I miss the mark to badly or end up whittling down to much off the transom I won't end up with a nice even border all the way around, Would kinda like to try some carving on that piece to. I could build it in pieces in place I guess but thats kinda cheating, I should be able to build it on a rack and fit it once I get the hull planked. unless I'm supposed to herringbone the planking together at the transition in this method. Oh well I got a ways to go on that one. Tomorrow I get the nod on if I can use a separate piece of floor for my lofting and I finish painting all the plywood.

    cheers
    B
     
  4. Lurvio
    Joined: Jul 2009
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    Location: Mid of Finland

    Lurvio Mad scientist

    Well, I had to try it also. I think there is an error in one point as it came out a lot out of fair in Delftship, Waterline 2 at St.4. The bow shape forward of St.1 is pretty much guesswork.

    Lurvio
     

    Attached Files:

  5. Boston

    Boston Previous Member

    I think the water line is 2'6" but it calculates out to 2'6"1/8 using several different aproaches

    try looking at where the chine intersects the waterline at station 5

    Oh hey I found my Yanmar engine 13.4 HP for $975 finally, I was worried I'd have to recalculate everything

    cheers
    B
     
  6. cthippo
    Joined: Sep 2010
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    Location: Bellingham WA

    cthippo Senior Member

    OK, I tweaked Terry's model some and fixed an error I made in it and came up with the attached, which i think is pretty close. It doesn't have the curved transom, but since I can't get transoms to work at all, I think we'll have to live with that.

    Lurvio, I tried to open your file with FS3.2 and it said it wasn't valid. Not sure what happened.

    The design draft you originally stated in your first post was 2'4" Make up your mind! :p
     

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  7. Lurvio
    Joined: Jul 2009
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    Lurvio Mad scientist

    cthippo
    Might need to update to newer version, mine is 4.38.130 (latest I think). I can't open your files either. :)

    Boston
    In the posted version the waterline was at 2' 4'' (710 mm) and didn't even touch the chine. I adjusted it to 2' 6 1/8'' (764 mm) and sure enough, chine hits water at St.5.

    The first has a displacement of 1460 kg (fresh water, 3250 lbs) and the latter 2060 kg (4580 lbs). According to Delftship. :p

    Lurvio
     
  8. Boston

    Boston Previous Member

    yup sure is 2'4" ( 2'4" and a half or 4/8 to be exact ) but then you have to add the distance the low point of the keel is above base line. The draft of the boat is not the location of LWL above baseline, its the LWL down to the bottom of keel. So I found bottom of keel and added its height off baseline ( 0' 1" 5/8 ) to determine where LWL is in the lines grid. From there if you draw out the lines on the grid then at station 5 it also calculates out that the LWL crosses the chine within 1/8. Once again if you go to the offsets you can figure it out.

    You have to draw out the grid and then do the lines in relation to the grid. If your developing your own grid you will never get it right.
     
  9. Lurvio
    Joined: Jul 2009
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    Lurvio Mad scientist

    No grid here, just points with three coordinates. Two given in offsets and third is the grid line. I printed the linesplan and used a ruler (and calculator) to guess the placement of buttocks, waterlines and stations.

    You are right about the waterline, I had not taken that into account in Freeship. However the displacements I posted seem to be correct, it seems the program calculates the numbers from the the actual shape, not from where it is located. The program changed the draft setting automatically when I moved the boat around. :)

    Lurvio

    Edit. The coordinates: Station, halfbreadth (offset or buttock) and height (offset or waterline)
     
  10. Boston

    Boston Previous Member

    hmmmm
    I think it you go look at both the lines pan and the table of offsets you will find that in order to loft accurately you must measure those points off a baseline, that baseline is not a measure of extreme draft but a random point of reference. Extreme draft is the distance from LWL to bottom of keel. The height of LWL off baseline does not represent extreme draft. If you look at the lines plan it says at the bottom "all measurements taken from baseline" so unless you create the grid as specified and measure off of it then your not likely to get an accurate drawing.
     
  11. Lurvio
    Joined: Jul 2009
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    Lurvio Mad scientist

    Pointless, this debate is. (with Yoda voice) :)

    You know, were talking of the exact same thing.
    I made assumptions (unreadable small text on the drawings) for the grid locations. Here's the measurements I used:
    Waterline 1 57'' (above baseline)
    Waterline 2 48''
    Waterline 3 39''
    Buttock 1 9'' (from centerline)
    Buttock 2 18''
    Buttock 3 27''
    Stations spaced 36'' centers except St.9 - St.10 30'' and St.0 - St.1 28 1/8''

    All of these are used in the model, as are most of the offsets, I dismissed some points that were close to each other (minimal influence to the overall shape) and the bow is a guesswork as i said before. All in all, the model is pretty accurate. The main difference to lofting is that Freeship draws the lines through the midpoint between two points and in lofting you draw the lines through the actual points. How much this affects the model depends on the number of points, more points - more accurate.

    Lurvio
     
  12. cthippo
    Joined: Sep 2010
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    Location: Bellingham WA

    cthippo Senior Member

    Interesting. According to my model the displacement at 2' 4" is 2.5 tons and at 2' 6" is 3.166 tons. I wish I could get my copy to open your model.
     
  13. CatBuilder

    CatBuilder Previous Member

    Could you share that source?

    I'm engine shopping too.
     
  14. Boston

    Boston Previous Member

    my bad
    I must have misunderstood you

    I'm just now working out the odd spacing of the first and last stations, I'm basically blowing up the drawing and scaling it then averaging any deviation from what the total length is supposed to be. Spent my evening after work hauling material over to complete the floor.

    will have to see if we end up with the same numbers.
    I got 2' 5" 4/8 on both ends and I averaged the distances that where supposed to be 36 ( the station lines ) to find the average known scale. adds up to exactly 28' 11" after adding 24' of station spaces.

    I also scaled the buts to the water lines and they appear to be identical so I'm going with 9" spacing on those as well.
    cheers

    OH and ya, none of those programs are Mac compatible or at least I cant get them to open, maybe one of our computer dork friends can do it but I'm lost on how to convert it.
     

  15. Boston

    Boston Previous Member

    hey Cat I've not heard back from them yet but when I do I'll pas on the information
     
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