First time poster seeking advice

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

  1. mbowser
    Joined: Nov 2015
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    mbowser Junior Member

    Hi all,
    First time poster and a complete newbie when it comes to boat design, so forgive the dumb questions. I've spent the better part of my life mucking around boats (mostly sail) anywhere from 8' prams up to 50' ocean racers and everything in between. I'm drawn to larger classic displacement designs but appreciate and enjoy small planing hulls that get up and go (I've owned an o'day daysailer for 25 years).

    I also currently own an Alberg 35 that I did a complete re-core and restoration on (www.alberg35.com), but my boat building experience from scratch is limited to a few stitch and glue dinghy's and kayaks.

    So anyway, I am looking to start a new small boat project for camp cruising and want to build it myself. I am considering a number of designs that include Iain Oughtred's Caledonia yawl or Sooty Tern as well as a number of other designers that draw similar lines. I sailed a CY this summer and know that it is well behaved, but after spending hours online researching other designs, I know it it not particularly fast and I've started to look at faster semi-planing hulls such as the Core Sound 20. The stitch and glue build of these would make it easier than the Caledonia Yawl or the like, but the problem with many of these boats is that they just don't appeal to my eye. I know the CS 20 seems to be a pretty good performer, I just can warm up to the cat ketch rig and a hull that looks like a powerboat. Call me vain, but I like pretty boats.

    Not having found a design that I can completely fall in love with I am now considering designing my own. I've come up with a preliminary design for a multi-chined camp cruiser for sailing the inshore waters of Maine coast that might work (at least from my untrained eye), but I was hoping for the following advice:
    1. Is designing a boat that actually sails well even feasible for someone with no design experience? This assumes that a proper rig, centerboard and rudder can be developed for it, but that's another can of worms, right now I'm just focused on the hull shape.
    2. If the answer to #1 is yes or maybe; would the attached design be potentially suitable for carrying at least 2 people and camping gear safely and reasonably fast?

    Thanks for any advice you can give.
     

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  2. John Perry
    Joined: Nov 2003
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    John Perry Senior Member

    Yes, I think it must be feasible since the first boat I designed sails well (IMHO!)

    As for being just focused on the hull shape, I would say that hull shape is a small part of the whole design work and also pretty well everything in the design of a small boat is related to pretty well everything else. So you cannot (for example) choose the hull shape without a pretty good idea in your mind as to how much ballast there will be, if any, how much you can rely on the movement of crew weight for stability, the rig, etc etc. Its all interrelated. Quite different from, say, designing a computer program where a good approach is to consider the whole as a set of modules that can be separately developed then assembled at the end.

    Taking a very quick glance at your sections, I would say that these have the look of a boat that relies on ballast for stability, but I doubt that you have the displacement you would need to carry that ballast. You also seem to have quite hollow waterlines forward, I am not keen on that myself, but its hard to say with certainty that it is actually wrong.
     
  3. mbowser
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    mbowser Junior Member

    Thanks John,
    This kind of feedback is exactly what I need. Most of the designs I'm looking at use minimal or no ballast and use crew placement to counteract the heeling forces. I'm inclined to do the same and don't want to add any substantial ballast since this boat will be beached regularly and don't want the extra weight to manhandle. How did you come to the conclusion that this design needs ballast? Is it the fairly narrow beam? If so, I'm not set in the beam as it stands, but I do need to row this boat (it will be motorless), so I have to keep it within reason.

    The hollow waterline forward and plumb-ish stem was intended to cut through chop that is common in the area I sail, but maybe that isn't how it's done.

    To your point about everything related and that the hull is a small part; I agree fully, I'm just trying to gauge whether or not this whole idea is an exercise in futility. Currently, I plan on a yawl rig (see attached rough sailplan) but I'm holding off on placement until I mostly finalize the hull and can locate the centerboard and trunk appropriately.

    I may never proceed beyond design stage and may just end up building a stock plan, but this is fun anyway and I'm learning lots.
     

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  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    You might want to start with a couple of things before committing to any lines. First would be a comprehensive list of what you expect from the boat and their value on the priority list. Next an approximate gauge on what going in and on this boat (weights). With these in hand, you can start thinking about the midship section, Cp and volumes you'll need to support what you want and need, plus offer the performance envelop desired.

    For example, if looking for a performance oriented raid boat, you might want to sacrifice some accommodation for a more favorable hull form, with it's lighter weight and flatter bilge, compared to say a cruiser, which might need a deeper bilge, heavier scantlings and more commodious hull form. This is the point of the list making (SOR), it keeps you focused, so you can reasonably attain the design's goals.

    Reconsider the proportions of the rig. The cat lug yawl thing is a novelty, but not particularly functional. The mizzen does offer some hoist height for off wind sails, but precious little and the mizzen itself is little more than a steadying sail.

    [​IMG]

    This is my Rocky design and shows a unique rig, though not cat lug, I took a more traditional approach to get some balance, an effective mizzen and reasonable downwind sail hoist. It has several interesting features, including an offset centerboard, so the cabin is free of a case intruding into the space (hidden under a cabinet about 8" off the centerline).

    [​IMG]

    This is my Flint design, which is a larger hull and a different rig, but still using the 5 panel hull form approach and offset centerboard (same reasons). It's available in round bilge as well. Both Flint and Rocky show a bit of hollow in the LW's forward, but not a lot (just enough given their Fr numbers). My point is you can have your cake and eat it too, but you have to define the goals and get an idea of weights, before you can consider hull forms. For the novice or budding designer, you're best off sticking to more conventional arrangements and shapes.
     
  5. mbowser
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    mbowser Junior Member

    Hi PAR,
    You pretty much nailed what I am looking for: a performance oriented raid design. Perfect...

    The design I put up earlier today was by no means the end of the process. I have a lot more work to do before I solidify anything.

    I do have a list of criteria that have been shaped by past experiences.
    1. Simplicity - I'm pretty much done with complex boat systems. Been there, done that. My wallet has been emptied.
    2. No motor - a set of Shaw and Tenney oars will be my motor.
    3. Easy to rig and strike. That was my primary reason for looking to the lug rig. No standing rigging allows one to strike the rig in just a few minutes if a long distance row is needed. I have my O'Day Daysailer rigged to row and have had to row for several miles at a stretch on occasion, and I can tell you that having that standing spar swinging around really gets old fast. A free standing cat ketch rig like your Flint design is an option (and similar to the Core Sounds). I do like the versatility of a yawl and it's ability to make the sail area manageable.
    4. Light - I want to be able to manhandle this thing and want to keep the weight low (<500 lbs loaded, minus humans). This means no cabin other than a tent that I can rig at day's end. My Alberg 35 has a cabin, I don't need 2.
    5. Fast - O'Day Daysailers aren't exactly known for speed, but that Uffa Fox planing hull really gets up and goes when there is enough wind. I like the idea of having something that can escape hull speed. My Alberg 35 can only dream of hitting 10 knots. I feel like a boat with a similar semi-planing hull form to the O'Day that doesn't have a big heavy cuddy and other furniture would get up and fly that much faster.
    6. Pretty - I like pretty boats and I'm a sucker for classic lines. I've had the privilege of being able to race aboard a number of classic yachts that are stunningly pretty (New York 32 Buzzards Bay 25 for example).

    Thanks; all this helps me crystallize the vision in my head.

    Also, I checked out your site and really like the Murphy. Great looking boat and looks like it could check a number of things off my list.

    -matt
     
  6. SukiSolo
    Joined: Dec 2012
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    SukiSolo Senior Member

    Welcome to the forum. I don't see why you should not be able to design something perfectly serviceable for your requirements. There are as usual some conflicts to resolve but tbh anything over about 14' will plane pretty easily with even fairly small sail area.

    Pity the Mirror 16 plans got lost!. Not sure you'll get a 20'er down to a light enough weight to manhandle easily. It may well be worth a look at the Laser Stratos (although FRP, a wood close copy is not out of reach) which has/had a ballasted option, although shorter it is relatively narrow, and fairly quick. Just for some inspiration and also perhaps a look at these links.

    https://en.wikipedia.org/wiki/Laser_Stratos

    https://en.wikipedia.org/wiki/Mirror_16

    http://uk-hbbr-forum.967333.n3.nabble.com/John-Perry-td2159398.html

    http://www.bluelightning.co.uk/

    Like John above, I would be tempted to try and eliminate most forward hollow waterline curvature and widen the stern garboard plank a bit, might help in the planing department...;);)

    If you use 4 planks per side you can get within about 2.5 -3mm (less than 1/8th") of a smooth shape btw. A bit harder with three planks but be prepared to bend the bottom plank a bit to help. Surprising what a small amount of curvature here can do to help straighten waterlines and move volume around.

    Personally if you wanted a simple rig a fully battened una main would be fair and could be reefed quite fast. Only proviso with full length battens is you MUST be head to wind to hoist the main. Maybe a small furling jib would help especially upwind and is certainly enough on its own in storm conditions. I will admit my own preference is for somewhat more modern aesthetics but without losing the practicality of old, and keeping as much sensible seamanlike technology as possible.
     
  7. mbowser
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    mbowser Junior Member

    Thanks for the encouragement, and for your patience. The knowledge on this forum is astounding.

    I should qualify manhandle. I don't expect to be able to drag it 100 meters up a beach, but I'd like to be able to launch on a falling tide with the help of some fenders under the keel. My Daysailer is likely in the 5-600lb range and is doable, but is a bit more than I'd like.

    Excellent, I really like some of the blue lightning designs, they do look fast. My only concern with those (and the Stratos) is the ability to row reasonably well. I know that it's all a trade off, but 'rowability' needs to be part of the equation.

    I'm not opposed to eliminating the hollow forward, but I guess I don't understand why. Honestly, I didn't even intend to add hollow forward, I was just drawing what looked good to me and thought that the hollow would allow the hull to cut through chop. I'm curious as to why one would add or eliminate hollow to begin with though.

    On that note, I just ordered Skene's 'Elements of Yacht Design'. Hopefully that will help to get me up to speed on terminology and some of the 'whys' of boat design. Are there any other design books that would be good for a beginner?

    Next iteration, I will try 4 planks instead of three, I see what you mean.

    I am keeping an open mind to all rig possibilities at this point.
     
  8. Tiny Turnip
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    Tiny Turnip Senior Member

    Hi Matt - just in response to your emerging SOR, here's something a bit different, which would seem to fit your needs very well. (Allowing of course that beauty is in the eye of the beholder.)



    I have one of these cat rigged trimarans by Solway Dory. Unstayed rigs, reef by rolling around the mast. 16ft, in the ballpark of 200lbs rigged, so a two person lift up the beach. will carry its own trolley on board. Designed for 2 person camp cruising on the west coast of Scotland. Leeboard rather than centreboard, simplifying construction and keeping the interior clear. Modest rig, 90 sqft, but will happily see 10knts plus if you want to play. Solway Dory have subsequently developed a system of aluminium beams with keyways and locks rather than the lashings, which reduces the setup of the outriggers to 5 minutes or less, and allows the outriggers to be slid over to come alongside a dock. Also available is a canoe stern, which to my mind is prettier than the transom, albeit at the cost of a little volume.

    Very, very simple.

    Oh, and it will paddle all day at 3knts.


    (there is also a more conventional sailing canoe in the video)
     
    Last edited: Nov 24, 2015
  9. SukiSolo
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    SukiSolo Senior Member

    The trade off is reasonable righting moment (or arm) and beam, I've tried to keep to reasonably narrow (rowable) suggestions, at least I hope so, even if the blades may need to be a little on the long side. Don't forget stern sculling either.

    With forward hollow on this type of shape (as per your initial outline) you get a trade off in my experience. It may be marginally 'better' upwind but the downwind/offwind penalty is big - the boat won't take off easily and nose dives on a run more than is comfortable. The trick would seem to be getting the rocker right, though this is not that easy. Mainly I've played with smaller boats than 20' but these are the traits that show up when shapes are moved even by only a few millimeters!. My take is that a lot of (and please excuse the term here) beginners see a lot of forward V as desirable as cutting through the water. Better to think of trying to get the water as sweetly as possible under the hull to recover the energy expended. Water thrown out sideways is energy lost. BTW you have way too much sheer especially forward on the initial sketch.

    Have a good look at stuff like the Blue Eyes 20 by Keith Callaghan. There is a lot of modern good thinking in the shape, and note the 4 plank version with two very narrow planks (in the bow), the garboard and one next to it. These planks turn very fast, similar to modern Merlin Rockets. Glad you are finding some inspiration in these shapes, they behave well too, from personal experience of sailing some of his dinghies.

    On one of the sections on this Forum is a list of useful books. TBH one of the best things is just study loads of similar plans IF you can find them. There's a lot of information in them if you look carefully. Also be a little open to stuff either side of the length range.
     
  10. mbowser
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    mbowser Junior Member

    Thanks Tiny. What you are suggesting makes absolute sense in every respect and seems like a tri or cat would work admirably for my intended purpose, but as much as I try, I can't warm up to the look. I am fully aware that I put far too much emphasis on form over function, but if I am going to devote considerable time and expense into a boat, I want it to be something that pleases my eye.

    It's my loss.
     
  11. mbowser
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    mbowser Junior Member

    Ah! I thought that cutting through the water was what you wanted, but it does make sense to get the water under the hull as opposed to pushing out to the sides.

    By too much sheer, do you mean along the bottom of the hull? Or does increasing the curve at the top along the sheer line have another unintended effect?

    The BlueEyes 20 really caught my eye, I will be investigating that more. Thanks again for the links and help.

    -matt
     
  12. SukiSolo
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    SukiSolo Senior Member

    I meant the sheerline at deck to hull level. Look at PAR's designs, much more even and closer to level. You only need to accomodate a reasonable oar/rowlock height, the bow area can be relatively a small way above this as any foredeck will allow breaking seas to run off.

    Be careful with the BlueEyes in the sense that she is ballasted (weighted c/board) so her rocker and underwater displacement is suited for that, but she is a good shape to head for, with suitable changes. I think you would love her performance, also believe there is some Youtube video of one under sail, and planing, if not, a similar one of Keith's is, and in quite choppy east coast UK conditions. You'd be surprised how much a little forward volume underwater will lift a boat offwind even with the deck almost submerged forward. A 20' is/will not be as sensitive as a 12' or 14'er to body wight being thrown aft so the hull ironically has to do more work.

    In terms of energy movement, think of the hull acting as a centreboard but on it's side a bit.. It takes a little imagination because one side is in air but the key is that a foil tends to recover most of the energy in the after part. Yes, it is a different shape to deal with the interface of air and water. The actual wedge angle (in plan) or entry angle (waterline) at the bow is important for upwind work ie the thinner the wedge the better but again balanced by stability and lift offwind. The Mini Transat boats show how a scow shape works.....

    There's also the excellent Cox's Bay Skimmer deigned and built by the Kiwi, Gary Baigent, which is an excellent alternative.

    See this thread.

    http://www.boatdesign.net/forums/sailboats/coxs-bay-skimmer-49353.html
     
  13. mbowser
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    mbowser Junior Member

    Thanks SukiSolo,
    Over the Thanksgiving holiday, I spent a little more time making changes to the design. Here are the major changes:
    1. Added an additional plank (4 total per side).
    2. Added 6 inches to the beam.
    3. Flattened out and lowered the sheer a bit
    4. Took at least some of the hollow out of the bow (I think I did at least).
    5. Widened the garboard plank to hopefully help with planing.
    6. Changed the transom from flat to angled (is that called 'counter').

    The design seems to pass the developability check in FreeShip! (still a few bad spots in the transom and bow to work out) and I was able to develop plates that I printed and made a paper boat (my teenage kids think I am a complete nerd).

    Anyway, I hope this iteration is going in the right direction, but any critique is welcome.
     

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  14. Tad
    Joined: Mar 2002
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    Tad Boat Designer

    This is a better looking boat but you still have a ton of twist in the bottom panel under the bow. That will, by far, be the most difficult part of building this hull. If you drop the first chine (in profile) to the very bottom of the stem (on this boat that's a bit aft), you'll eliminate that twist.
     

  15. gonzo
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    gonzo Senior Member

    If you were considering an Ian Oughtred design, study the lines. They are easy to plank boats, for a whitehall type. The garboard has relatively little twist, which is usually the hardest.
     
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