Lindsay Lord, Daniel Savitsky, and Ocean Boats

Discussion in 'Boat Design' started by tananaBrian, Oct 15, 2017.

  1. tananaBrian
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    tananaBrian Junior Member

    Hi All,

    I'm wondering how many boats are built like the Great Alaskan, designed with a nearly prismatic hull form ala Lindsay Lord (I have his book) and Daniel Savitsky (I have several papers)? Back when LL was doing his landmark work on planing hulls, the combination of the boat having a prismatic hull form (same deadrise amidships as at the stern) and the right aspect ratio for the assumed operating conditions (0.37 for offshore if I recall), boats designed according to his findings were the fastest and most efficient, although back then, he used a deeper deadrise than many boats have today. Daniel Savitsky's papers on high speed planing hulls confirmed Lindsay Lord's work. I bought LL's book, and obtained several of Daniel's papers at about the time that I was going through the Westlawn School of Professional Yacht Design and designed a boat based on these principles, but also with some design concepts from dories and other boats worked in for other reasons, e.g. not just efficient and fast offshore, but also seaworthy, able to bob up and over seas even when the boat is adrift or moving slowly ... in other words, I wanted a boat that was efficient (cheap gas bill), fast ('cuz I don't like slow), but was still safe when fishing and trolling offshore. My Great Alaskan design, buildable 25 to 29 feet or so, was the result - initially designed for an assignment at Westlawn, but later fleshed out and offered as plans for others. Now, about 15 years since then, the Great Alaskan has been built and used all over the world and it exceeds all of my expectations - but I wonder what other boats may have incorporated the same design concepts and how well they are doing? In the Great Alaskan, the amidships deadrise is only 1-1/4 degrees steeper (14.35 degrees) than it is at the stern (13.1 degrees), but the boat's got a fairly fine half-angle of entry as well which helps it cut through chop... well, as fine as I could make it and still squeeze in a queen size bed in the bow.

    So, my question is this ... Are there any other boats that share similar characteristics to the Great Alaskan? Even if they are commercially built, not homebuilt or do-it-yourself etc?

    See: Glacier Boats of Alaska http://www.facebook.com/glacier.boats.of.alaska (Glacier Boats of Alaska facebook page)
    and: Glacier Boats of Alaska http://www.glacierboats.com (Glacier Boats of Alaska main web site)

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    Thanks in advance,
    Brian
     
  2. DCockey
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    DCockey Senior Member

    Renn Tolman, who also lived in Alaska, designed some similar boats, though Renn's bottoms have more warp. I don't know how many of his designs have been built, though they appear to be quite popular. Tolman Skiffs: Boat Plans in Book Form http://www.tolmanskiffs.com/ Renn Tolman and His High-Endurance Skiff - Professional BoatBuilder Magazine http://www.proboat.com/2014/09/renn-tolman-and-his-high-endurance-skiff/

    The C-Dory Venture 23 and 26 also appear to be somewhat similar, though I don't know what the deadrise angles are. C-Dory 23' Venture https://www.c-dory.com/boats/venture/cruiser-23/
     
  3. tom28571
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    tom28571 Senior Member

    Brian,

    All the Bluejackets were based on Lindsay Lords fundamentals although they are biased toward inshore cruising and do not have any dory form in them. www.bluejacketboats.com The website is somewhat corrupted and needs some work.

    C Dories are closer to true dories with high flare and narrow waterline beam. They are therefore not as efficient of power requirements, fuel or interior space as yours and even less so than Bluejackets.
     
  4. tananaBrian
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    tananaBrian Junior Member


    I like the style of the C-Dories and their seaworthiness is legendary, but they can be real pounders too ... been there, done that. I've never seen the Bluejacket up close, but have always really liked the styling - very classic. I can't remember hearing about how the boat operates in different conditions such as offshore, but I do know that it goes onto plane sweetly, like an elevator, and that in Puget Sound type water (which can be nasty, especially in tidal rips between islands), that it does very well and runs very efficiently. Arima boats, while they may not look like it, are very seaworthy too and I prefer them to the C-Dory. A friend's got a 22' Sea Legend that I've spent time in - Buoy 10 / Columbia. There was the Alfred W Davis from Tracy O'Brien that I thought would do better and heard that it was a fine runner, but the design never really did take off and I'm not sure why. I'm not aware of anything in the 25-29 foot class that is similar to the Great Alaskan (homebuilt that is)?

    When I designed mine, I had SE Alaska cruising and on-the-water camping on my mind. With a Bruce anchors, which are designed to dig in over a full tidal cycle, I know people are using the Great Alaskan for just that, and I know one guy that sleeps offshore in his and just tosses out a sea anchor before bed - He's got more backbone than me, but he's out far enough where the various currents won't get him in trouble with fixed obstacles. You know, beaches? LOL. He's got an omni-directional radar reflector on a mast over the pilot house though, so hopefully if drifts into a shipping lane, the big boys will see him and avoid (?).

    bd
     
  5. PAR
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    PAR Yacht Designer/Builder

    The seakeeping and worthiness of the dory is way over rated and blown way out of context now. Most boats that suggest they're dories aren't, except have the typical spring in their sheer and excessive flare in their topsides, to make them somewhat resemble a dory, especially if you don't know what a real dory looks like or more importantly, how it behaves at sea. I dare anyone that knows the differences challenge me on the subject. For example, show me one modern "dory" powerboat design that's actually a dory and not a dory sort of looking thing?

    The reputation the dory got was from some massively skilled surviving sailors (not power boaters), as they dragged, sailed or rowed home a ton and a half of cod, from deeper water fishing grounds. No place for an open fishing boat and a huge percentage of these gentlemen, didn't return, but they needed to eat and OSHA regulations didn't exist then and the crew/boat were considered expendable. The sailors that survived these excursions into deep water, credited the boat, instead of their truly serious skills at small boat handling and the fact, that the shape of most dories load down well, making for a much more solid platform in a rough slosh, if well loaded.

    I'd like to see this myth dispelled to some degree, still giving the boat credit where it's due, but not the seemingly unabashed "seaworthy" title it never really earned. Better yet, take a real dory out for a sail or row, with a modest, even light load and see what you think. Don't eat a big lunch before you shove off, trust me.

    Lastly, at the turn of the 20th century, when dories were being modified into power dories, they quickly figured out they needed a skiff, not a narrow bottomed dory. They also figured out, that the traditional file planked bottoms had to go, in favor of a fore and aft planked bottom, unless only a year's service was all they expected, before that 1,000 pound 15 HP engine would shake every seam open.
     
  6. tom28571
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    tom28571 Senior Member

    I don't usually like to get into attacking a legend but PAR opened the door. C Dories and dories in general are very popular, which may be due to the fact that small cruising powerboats are not numerous on the market and C Dory is, by far the most marketed one. When loaded, a dory is (can be) pretty seaworthy but their main claim is the people think they are cute. Its a decent boat within its proper parameters and has made some impressive voyages, but in every case I've seen as a powerboat or sailboat, there are other better boat designs available than dories.

    I've had some experience with the 22 foot C Dory. Dealers will not sell one with less than a 90hp for that reason. The narrow bottom means a high bottom loading which translates into more power required to plane. A relatively flat bottom means that pounding is an issue as well. Interior space is cramped and and the narrow bottom and high angle of flare means that a 6 foot tall operator cannot stand at the helm. A dark secret is that they can also heel over in some conditions running downwind, get stable lying on the side, and will not right themselves without help from the helm and throttle. Happened to me once, which was neither expected not appreciated. I drove an Arima while fishing in Baja for two weeks and think it is a far superior handling boat to C Dories.

    Modified dories like the Tolman and Simmons plus some others get more useful as the bottom gets wider and less like a true dory. A Gerr Offshore Skiff 28' is another of the type. It can heel inward on a turn so far that the helmsman can easily stick his hand in the water and is tender at the dock which is another dory feature. As the bottom gets more beam and more deadrise, the "dories" get better. There are special times when a dory is the choice but I think, in general, they are way over hyped.
     
  7. DCockey
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    DCockey Senior Member

    Historically a dory had a fore-aft planked flat bottom and flaring sides. Originally dories had narrow transoms and were rowed or sailed. Later dories with wide transoms were developed for use with motors. Perhaps because of the dories reputation (correct or not) for seaworthiness the word "dory" has been used in the brand name of various boat which have little or nothing in common with traditional dories.

    My understanding, perhaps incorrect, is the "Venture" series of C-Dories do not have flat bottoms, and differ from what C-Dory now calls the "Classic" series. The "Venture" series was what I mentioned above, not all C-Dories.

    The Tolman skiffs do not have flat bottoms, unlike the Simmons skiffs. The Tolman skiffs have V-bottoms with 8 degrees of deadrise at transom, and increasing deadrise forward. Tom, what is the deadrise on your Bluejacket boats?
     
  8. tom28571
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    tom28571 Senior Member

    David,

    Monohedron deadrise is 10 or 12 degrees depending on need to maintain a fine entry and equal forward deadrise for the larger and beamier 28' model. Its a compromise between smooth ride in chop, displacement, efficiency and draft. If designing for more offshore, I'd go a few degrees more and accept a bit less in interior footprint for berths, helm foot room, etc.
     
  9. tananaBrian
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    tananaBrian Junior Member

    When it comes to the Great Alaskan design, the 'dory' in my original description only applies to the flared sides and really, nothing else is dory-like at all. Flared sides, combined with a reasonably high transverse metacentric height (GMt) helps the boat roll slightly more than the big heavy fiberglass boats do (as swells or waves pass under the boat), which in turn helps prevent water from spilling in when you're moving slow and large waves are passing buy - you know, what you do when camping or fishing. The flared sides also result in a PPI (pounds per inch immersion) that increases more rapidly with inches of submersion than do the straight-sided big glass boats and more rapidly helps maintain buoyancy as the boat is 'submersed' (hogging over the top of a wave for example). All good. The downsides to these design trade-offs is that if you have too high of a GMt, then the boat becomes too stiff, and snap-rolls with every wave. This is hard on boat and crew. The trick is to try to find that magic sweet spot where the boat has an optimal ability to bob up and over waves, rather than letting water climb up the sides and possibly enter the boat, but don't take it so far that the boat wears you out to be in it or over-stresses the boat itself. To determine the best GMt, you simply have to study a lot of boats in the same class that have similar dimensions and displacement, then choose what GMt you'd want for your design. From what I hear from owners of the Great Alaskan, I think I came pretty close to optimal on this boat. For that, I'm happy. There is always some risk in making your decisions and then waiting to see how it turns out. I'm pleased with the results that I got.

    Brian
     
  10. tananaBrian
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    tananaBrian Junior Member

    True ... for offshore, the heavy deep-Vs run like a Cadillac. The shallower deadrise of the C-Dory gives it higher mileage though. We know the trade-offs. The number one killer of efficiency on the water is weight / displacement. Number 2 is the hull form, monohedron hulls better than 'warped' hulls that have more deadrise variation from stern to the forward sections. The 'warped hulls' tend to operate and maneuver well, especially in the class of boats that are equal to or shorter than 24' or so. The fast monohedron / prismatic hulls of Lindsay Lord's day were what we'd consider deep-V monohedrons today, and the design necessitated extra length in order to incorporate a fine entry forward of the 'line of highest pressure / line of highest lift' (the V-shaped waterline when the boat is on plane is just forward of the line of highest lift).

    Brian
     
  11. tom28571
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    tom28571 Senior Member

    I haven't paid much attention to the new Venture series C Dories. Kind of lazy as a friend and the Southeastern distributor is only about 12 miles from me and I will go take a look. The specs bring these boats more in line with my thinking in this size range and should be more capable cruisers but that is only looking at numbers, not boats. The basics look fairly close to what yours may be although I'd suspect they are of heavier displacement. The Venture 23 displaces as much or more than my 28 footer. There are economic reasons for this but it is what it is. A wood or composite boat will always offer efficiency and performance advantages over a non exotic fiberglass commercial one.

    Edited to add: Lord used the section 25% aft of static waterline entry as a reference of forward deadrise fineness and I use that as a reference also.
     
  12. tananaBrian
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    tananaBrian Junior Member

    Ah, the age-old trade off! You always pay ... but will it be with your time, or your money? The Great Alaskan can be on the water (boat, trailer, electronics, motor etc) for less than $30k. That's a small percentage of the price of a new commercially built boat, and less than most used boats as well ...but you have to dedicate time to the project instead. So far, on the calendar, that ranges from a few months to a few years, depending on the who and where and their personal time schedules. At least nobody's been divorced right after a build so far... LOL....

    I use the same waterline entry as Lord - noting that it's a reference for you to compare with other boats (or articles). When a well-designed planing hull is on plane, it'll be right around 4 degrees bow-up and the forefoot will be 'just out' of the water. What is the effective angle of entry in that condition? I'd have to measure it with CAD..... :)

    Brian

    PS: It sounds like the 28' C-Dory is the most comparable boat to mine ... anyone know the deadrise? I'll google it ... and will have to go take a look at one up close too. Now that I live in Idaho, I doubt that I can do that until I get over to the Oregon coast area again....
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    All these types of boats have one thing in common, they cannot handle chop. Or more correctly, the unfortunates aboard cannot. Throttled back they can be OK on the open sea, but where tides and currents oppose wind, and waters shallow, it can be an endurance test.
     
  14. tananaBrian
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    tananaBrian Junior Member

    In varying degrees, this is true and is the main trade-off. Nothing rides like a big Orca or SeaSport with their high displacement and deep V hulls - Cadillacs on the water! The one and only C-Dory that I rode in was a pounder, but it was one of the older ones with the flat bottom towards the stern. I did try looking into the deadrise on the 28' Venture C-Dory, but a) apparently there is only a 26' Venture out there (?), and b) while their website says 'deeper V to help ...', I didn't spot any deadrise specs. I suspect it's right around 13 degrees, possibly 14, but C-Dory has always tended towards 2 things ... low deadrise and a somewhat bluff bow. I'm sure that as they iterate designs, that they don't want the apple to fall too far from the tree, so I suspect the Venture might have both a finer entry (a luxury awarded to boats with more length) and a deeper deadrise (to some degree - pardon the pun!).

    Just looking at pix, I believe the Great Alaskan has a finer entry than the C-Dory, but can't say for sure without lines drawings or meaningful specifications to look at. I know that the Tolman series of boats are more bluff in their forward sections, and the GA entry is finer. In a Great Alaskan based out of Homer, Alaska, I witnessed how it ran through the chop versus a Tolman Jumbo and was happy to see that the GA ran smooth and with consistent spray along the sides while the Jumbo was going 'splash! splash! splash!' against the chop and didn't look like it was running smooth. The small differences in entry and deadrise angle do make a difference on the water. I would now like to see how the Venture class C-Dory's run... I suspect they do well.

    Brian
     

  15. tananaBrian
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    tananaBrian Junior Member

    Anybody out there know the stern deadrise of the C-Dory Venture 26? We don't have them in the boat shops around this part of the country, and C-Dory appears mum on the topic.....

    Thx,
    Brian
     
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