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Hull Shapes

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  • Hull Shapes

    I am trying to decide on which boat to build next. I have to stay under 20 feet max and want something easy to launch with a cabin. I have narrowed my list considerably but am now struggling with the best hull shape for my needs. I want max volume for the length so the hull will be beamy. I had a beamy flatbottom boat and, while it was stable, didn't like the pounding or bobbing around like a cork in motorboat wake. I have a smaller beamy V bottom and much prefer its feel to the flat bottom. I also appreciate how well it tracks and gets up on plane. I am considering a lapstrake design which basically is a round bottom. Another design I am considering is a 3 chine shape with a small sized flat part on the bottom.

    So, my question for you is what are the advantages in my boat size and range of a V bottom, 3 chine, and a round bottomed hull? Focus on sailing characteristics, ability to handle inland lake waves (and chop), speed, launching, and behavior at anchor when you are trying to sleep on the boat.

  • #2
    Project: JustRight

    - Rick


    • #3
      gotta agree with rick. vegabond+ is a good boat. easy to build and from what i've heard/read sails axcellent. but, over 20 ft at 23'+.
      have you had a look at "sztrandek"?. you can down load the plans off the web site. google "strandek". i think one could put a 5% stretch to the station intervals to give 17' with no problems.


      • #4
        Thanks for the suggestions but I am really looking for advice on the qualities of different shaped hulls rather than specific plans.


        • #5
          Originally posted by Swidm:
          Thanks for the suggestions but I am really looking for advice on the qualities of different shaped hulls rather than specific plans.
          "Understanding Boat Design" Ted Brewer
          "The Nature of Boats" Dave Gerr
          "Boats With an Open Mind" Phil Bolger

          Seriously, you'll learn more in a few hours reading these guys than you will here on this group. They sure know more than I do.

          [ 09-30-2005, 01:17 AM: Message edited by: Rick Tyler ]


          • #6
            Accidental duplicate post.

            [ 09-30-2005, 01:16 AM: Message edited by: Rick Tyler ]


            • #7
              Vagabond+ is a 20 footer, and you can always build it as a 18 footer if you omit the 2' aft "skirt" which Jacques Mertens added to the original "Primo" designed by J. P. Villenave. Jacques also carries the Vagabond 23, similarly derived from B. Veys' original Serpentaire plans.
              Great boats indeed, but "easy to build" might be misleading.

              Originally posted by merlinron:
              vegabond+ is a good boat. easy to build and from what i've heard/read sails axcellent. but, over 20 ft at 23'+.
              [ 09-30-2005, 08:57 AM: Message edited by: pippo ]


              • #8
                I'd say that generally speaking round sections are better than hard chined ones because they allow for a smoother water flow, however I understand that the difference might be very small or negligible. A friend of mine has built a Vagabond and the boat is very fast, smooth and weatherly. More surprising, box shaped hulls (such as Bolger Micro), i.e. the quintessential hard chine hulls, are reported to sail very well. Another friend of mine has just launched a beautifully built Micro which is surprising everybody on the lake for how well she sails, but I'm told that it's way too noisy at anchor to sleep in it.
                In my opinion, sailing qualities depend much more on the general hull shape and boat design (i.e., rocker, beam/lenght ratio, sail area, displacement, rig, etcetera) than on the hard chine vs round section discussion.

                Originally posted by Swidm:
                So, my question for you is what are the advantages in my boat size and range of a V bottom, 3 chine, and a round bottomed hull? Focus on sailing characteristics, ability to handle inland lake waves (and chop), speed, launching, and behavior at anchor when you are trying to sleep on the boat.


                • #9
                  I have read Ted Brewer and Phil Bolger but haven't read Dave Gerr but now I definitely plan to. I also have read Howard Chapelle, John Gardner, and Reuel Parker all of whom give some information on the nature of different hull shapes. However, I kinda want to hear people's actual experiences as well as their opinions. I always need to hear some word of mouth before making a major purchase .

                  A little more on my thought processes might help. I believe flat bottom hulls are good but, as Chapelle and Parker would say, best in a long narrow hull. Since the length of my build/storage area is limited I can't build a long-enough hull that has the volume I need.

                  I do like the V bottom hull on my 12' cat. It gets up on plane easily, is steadier in chop, and has great directional stability compared to the flat bottomed boats I have experienced. One V bottomed boat I identified as fitting my needs is the Hartley 18 ( but I am not in love with the lines of the boat. I have to say it has a great reputation and is loved by many but...

                  Then there are the multichine boats like the Vagabond that kinda are like a deep V bottom with the bottom part of the V whacked off. Kinda a cross between a V bottom and a flat bottom. This hull type is a mystery to me not being talked about in depth in any of the books I read (though I don't have Brewer's book anymore to check). Most of the books refer to this type of hull as some sort of step between V bottom and true round-bottomed boats. However, I wonder if there is more to this hull shape than that since I see it on a lot of boats including some who have great performance like the Vagabond. In some ways it looks like the hull has more flat plaining surfaces than a round-bottomed boat which makes me think it might be able to exceed hull speed easier.

                  Why is this important? Most of the time it isn't but there are times that I am sailing with or near a longer boat and I love to surprise them...I like speed or at least a boat that is faster than most production boats on one or more points of sail. I guess the reason for this is the deliciousness of beating a production boat with the boat I constructed with my own two hands. Many people are nice when you show up with a homebuilt boat but there still is a bit of snobbery in them thinking it won't perform nearly as well as a boat built in a factory. It is really fun to then blow their doors off and see their jaws hanging slack.

                  Back to boat plans. In this category I have looked closely at the boats. I already built their c12 and love the performance plus the great instructions they give. If I were to build one of their boats I would look at their new Vagabond 18 ( However, their boats look too modern. I want something that really stands out against all of the production boats out there. It is even more fun to blow someone's doors off in an antique looking boat that doesn't look fast. The Vagabond looks fast even when it is sitting still.

                  My current favorite boat plan is John Welsford's Sweet Pea ( It has a degree of traditional looks with an underwater shape that just looks fast. I also like it because it is a big little boat. In other words, it has a high beam to length ratio in a lightweight package compared to other boats of its volume. It is 17' 6" long, has a 7'4" beam, and is around 600-700lbs. This means it is easy to tow and launch (daysail) and has a lot of volume for its length. It also means that it will bounce around more in waves than a heavier design...tradeoffs. For comparison, the Vagabond's 18 stats are LOA 18'2", beam 7', and trailer weight of 1450lbs.

                  Roundbottom hulls interest me primarily because I have always wanted a lapstrake boat ever since living in Norway. Lapstrake boats, with enough strakes too look traditional, are round bottomed hulls. My understanding is that a round-bottomed sailboat with a cabin must have ballast. Wereas chined boats get initial stability from hull shape, round bottomed boats get it from ballast. This means more weight to trailer and launch. Having said that, who couldn't love the eye candy that is Eun Mara?

                  Eun Mara is on my list but I have also contemplated taking some of John Welsford's designs, particularily the 6 meter whaler, and putting a lid (or cabin) on it. I like the cabin for dry storage and a place for family members to nap, read a book, and etc... Basically it gives me longer time on the water. However, John Welsford recommends ballast when putting a lid on the whaler. Also, the beautiful round stern results in a longer boat than needed for the interior volume.

                  Reading through my comments you might ask what I have against ballast? I know a good system can make it easy to launch and retrieve a heavier boat. However, a heavier boat necessitates a bigger vehicle (costs) and uses more gas to tow (a consideration before the current rise in prices). I have considered water ballast but don't like the complication nor the potential problems inherit in building a system like that.

                  Sorry for the long post but I really would like to hear what other builders think. Also, now that you know the boats I am considering I would love to here more. Some of the other boats I have looked at include: B&B Belhaven, Selway-Fishers lovely designs, Glen-L's designs, and Dudly Dix's beautiful Cape boats.


                  • #10
                    If you want a planing boat, there are compromise hull.

                    The boat with the least wetted surface would have semicurcular sections, but would have no form stability.
                    A box would have the greatest volume but huge wetted surface, it would have great form stability and would plane easily. it would pound.

                    Let's try a Laser on for size. It planes easily but is slow in light winds. The fast sailors all move forward to pick the back of the boat out of the water in light winds, reducing the wetted surface. This got so bad that the class had to introduce a rule forbidding the crews from sitting in front of the mast (I think you are allowed to put your fingers in front of the mast)

                    This would be difficult but not impossible in a boat of the size you are trying to build.

                    Weight comes into the equation too, if you want to plane, then it's got to be light. Look at the Melges 24. When i was growing up the only planing keel boat I knew of was the YW Black Diamond designed by Jack Holt, I guess there would be the 210 over here too. There are plenty of planing sport boats now, that's becuse of materials technology.

                    I tried to keep within your parameters of discussing experiences. I'm going to break the rule now and suggest you take a look at this site.


                    • #11
                      I have a Dobler 16 which is similar in hull shape to Sweet Pea. It has a lwl of slightly over 14 ft (loa is 16'4"). The boat has a low wetted surface area and a moderate sail plan (86sqft) and it flies. Clocked her once on a gps doing 6mph close hauled in around 20mph winds and doing 8.2mph on a run downwind in the same conditions. I've had it going faster in 25mph winds, but since I did not have a gps with me at the time, I could not tell you how fast we were hooting along. Too fun!!! Having owned a flat iron skiff prior to this one, I can say that it pounds very much less than the skiff, but when it rides over a boat wake bow on, it is no different than the skiff in its behavior. But one slap/pound and you are done.

                      Hope this helps and sorry I can't speak to the round hull or v-hull shape. I've never been in one.


                      • #12
                        HWYL,thanks for the blue lightening link. Interesting boats and some good information in there. I am really struggling with this decisions. Seems like a light hull has the advantages of easy and economical trailering, small draft (beachable and gunkholing), and the possibility of keeping up with larger boats in certain conditions. However, it does have the disadvantages of being tossed around in waves (particularily powerboat wake when there is little to no wind) and behavior more similar to a sailing dingy than a heavier trailerable cruiser.

                        Dennis, thank you for sharing your experiences with the multichine hull shape that is similar to Sweet Pea and Vagabond. From your experience, it sounds like this hull shape still dampens out waves as compared to a flat bottom hull (similar to my experience with a v bottom hull).


                        • #13
                          Swidm, I've had that Dobler out in 25mph winds gusting to 30 with 2.5-3ft chop. The hull, even in those conditions, has been very seakindly in comparison to the skiff I used to own, but probably just as wet. The hull shape does dampen down the waves pretty well, and the deadrise of the hull makes her fast through the water (so I'm told). Being a fan of Welsford's designs, I'd vote for the Sweet Pea. The boat will be easily constructed, and a good performer. The Vagabond is a little too modern in her looks to my eye. Have you looked at Bolger's sheet ply Chebacco? Same multi-chine shape, and a good sailer from what I hear.

                          [ 10-02-2005, 10:01 PM: Message edited by: Dennis M ]


                          • #14
                            If I remember correctly, a lot of shallow-water cruisers recommend the v-bottom with the flat section so the boat will ground out upright. A comfort thing more than anything else.


                            • #15
                              Great point about the flat part being for comfort when grounded! I assume it also allows for a deeper V at the waterline without having to go so deep in the water. Lowers the displacement (ballast) needs resulting in a lighter boat.

                              Dennis, the Dobler is an open boat whereas the Sweet Pea has a cabin between the cockpit and the bow. I wonder if this would make the Sweet Pea a little less wet. Anyway, being honest with myself I am a fair weather sailor particularily if sailing with family on board. When weather kicks up I am more likely to head to a cove or protected area and anchor out than stay out and sail. However, I have had some fun by myself in small sailing dingies in heavier weather.

                              I will take another look at Chebacco. I have always loved the looks of that boat.