First time poster seeking advice

Discussion in 'Boat Design' started by mbowser, Nov 23, 2015.

  1. SukiSolo
    Joined: Dec 2012
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    Location: Hampshire UK

    SukiSolo Senior Member

    Looks like it is coming along nicely. One tip with scaling in a CAD system is never scale the original model or drawing by 1/3rd - you can never get back to the original 1:1 size. Well if you need to, do so as a separate file.

    Personally I actually prefer to use small stringers to get the plank joints and back the butt joint area in the bow. Not necessary structurally if you glass and fillet though, just makes planing the angles a little easier, traded against the problem of cutting and setting the stringers themselves plus framing to hold them solid. Helps stiffen the overlaps though.

    The shape looks to have loads of initial stability and a reasonable entry to help through waves. The harder thing is to judge the pitch motion, you know the waters you wish to use her in. I'd be tempted to run with it keeping it fairly light but still a shade conservative strength wise. Every boat has a slightly different feel, even if supposedly of the same design, at least to me. Maybe Lasers are pretty similar, but as soon as any permissible tolerances are allowed, there is no question that the boats feel and go differently. Surprisingly small differences can make a significant overall change in behaviour of a shape. Least you have a pretty decent shape to start with, well done.
     
  2. mbowser
    Joined: Nov 2015
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    Location: Canterbury NH

    mbowser Junior Member

    Thanks for all the feedback. Realistically, if I decide to go for it and build, it won't be until next summer at the earliest because I have been told by the Secretary of the Treasury (wife) that I need to sell my other boat (Alberg 35) before I start a new project. So the bright side is I have lots of time to refine the design and actually get more knowledgeable about design.

    Anyway, I took a crack at an initial sailplan based on a few assumptions and properties (which may or may not be correct):
    1. Sail plan CE should be aft of Longitudinal Center of Effort.
    2. Main mast is based on O'Day daysailer (I happen to have several lying around and might save some costs reusing one of them).
    3. Using Bermuda rigged yawl for now, but I'm not set in this. I am open to other rigs such as gunter or lug, but I do like a yawl configuration.

    So my CE=9.78ft and CLR=10.25ft (lead=9.5%).

    Total sail area is 290sq. ft (seems like a lot), but I may be reading the FreeShip! calculation wrong (sailplan is in separate layer for calculation). Please chime in if that is way too much area.

    If my assumption that CE should be aft of CLR is correct, what is the general consensus on what the lead should be? Does the 9.5% for this configuration seem appropriate?

    To me eye, the main mast seems a bit far aft, but when I compare to similarly rigged boats, it is fairly close.

    Any comments are appreciated.
    Thanks again.
     

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  3. philSweet
    Joined: May 2008
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    Go to the rig layer and make sure you have "Symmetrical" unchecked (and most of the other options as well). If you get bored, you can make a sail by going to tools > foils > and creating a "foil" the size of your sail. It takes a few tries, and is mostly a waste of time, but looks cool. You'll get lots of practice with transforms, and save the sail as a "part" for later use.
     
  4. philSweet
    Joined: May 2008
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    One other random comment. Your freeboard is a bit small. This suggests either a modest sail area, use in protected waters, 6" wide sidedecks, or perhaps all of the above. For gusty bays and larger bodies of water, I'd add about 2" or so. It's not wrong in any way, it just suggests fair weather sailing.
     
  5. mbowser
    Joined: Nov 2015
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    Location: Canterbury NH

    mbowser Junior Member

    Thanks for the tip, I'll give it a try. I'm certainly getting lots of practice with FreeShip!.

    On the other hand, I spent some more time reading about CE/CLR/Lead relationships and I think my assumptions were all wrong. No wonder the sail plan seemed so far aft. Back to the drawing board.

    Oh, also, I have sort of a 'who came first, chicken or egg' question: Should the sailplan be designed after centerboard, or at the same time, or before?
     

  6. mbowser
    Joined: Nov 2015
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    Location: Canterbury NH

    mbowser Junior Member

    I didn't see this post before I sent my last post. My current thought is to have sidedecks, but I think your right, it might need a little more freeboard. It's not intended for offshore passages, but some of the areas I sail get a bit snotty when the afternoon southwesterlies kick up.
     
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