Round stern vs box stern??

Discussion in 'Boat Design' started by Deadrise13, Feb 8, 2009.

  1. robherc
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    robherc Designer/Hobbyist

    Keep to the facts, I promoted nothing but an opinion, and called it as much when I gave it...you're the one mis-quoting, and trying to read more into my posts than I put there. Stick with the facts, or stick your nose back out...you have yet to add ANYTHING of substance to this thread. All you have posted AT ALL here is to attack other people's opinions without either proving them wrong, or giving your own...welcome to the "blocked list".
     
  2. PAR
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    PAR Yacht Designer/Builder

    My post wasn't speculation, nor any guess work as has been indignantly suggested. I'm very familiar with the stern shapes used above, it's one of my favorites, one I've employed it in several of my designs and as I posted earlier, will impart no difference on the performance of the vessel. Shown are elliptical stern vessels, typical of the type I used growing up in they very area they are from. They clear the LWL and at best will kiss it when squatting under way, which will not affect the performance envelope in any noticeable regard. If you bother to test, the sterns that are slightly immersed will show a very slight increase in drag, but not enough to get concerned about as we're talking a fraction of a knot.

    The reason for their use, which was finally mentioned, was to prevent fouling the gear and nets as it was dragged back aboard over the stern. It also was a way to gain additional working deck space well aft, while having relatively balanced ends below the LWL. This was typical of the displacement craft from which the type was derived. As power was introduced to these types, the sterns took on a different, considerably fuller shape below the LWL, but retained the elliptical stern for practical reasons.

    The first photo posted by Deadrise13, clearly shows the transom is clear. The second and third images show the semi plane version of this type, where the stern is just kissing the LWL, but provides a fair amount of bearing area when she squats. The fourth photo is clear enough, but appears also to be a semi plane hull. The other photos don't show enough to offer much information, but much can be gathered from the 5th image as they all are in semi plane mode.

    In plain english, it's a lovely stern, particularly if kept clear of the LWL. If used on a planning hull there often is a distinct knuckle used to provide bearing area aft as she squats. If a displacement mode boat, then it's kept clear. It offers stylish and effective deck space aft on a fine ended craft, isn't as effected by following seas and breaking waves as a traditional transom is and isn't as hard to build as you might think.

    For those that would rather find fault or offer less then productive replies, then maybe they should just go back to the pub and suck down a few more beers instead.
     
  3. Leo Lazauskas
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    Leo Lazauskas Senior Member

    What's wrong with finding fault, or asking posters to substantiate their unscientific guesses and loopy speculations?
     
  4. Deadrise13
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    Deadrise13 Junior Member

    Thanks for the LOVE PAR

    Hey Par, it seems you have a special spot in your hart like I do for a dieing haratige. As I said I grew up on the bay and have a very special part of my past spent on these type of boats. Now I live in Fla the land of the supper boats, Don't get me wrong I love them as well. I am having a boat built this summer like the Albatrose and really appritiate all the help. I am trying to figure out how to power it. I want some sort of econamy, but need a little speed on the runs. My off shore run is about 25 mile each way and I am going to fish this boat hard. Once again thank you for your help, It shows you know your stuff and have a working knowledge of a peice of Good old American haritedge. Any Ideas on the power plan, type eng, size, set up. The boat will be 45' x14.5'. Funny when I ask the Old gentelman that is going to build her how much she will way, He said in a Harkers Island voice "I don't Know I anit never weighed one". Fine with me, they have done the job all these years, I think it will turn out just fine. I am jellouse of the guys that can figure this stuff out on a caculatore. Thanks again for all the positive input!! Peace--------
     
  5. PAR
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    PAR Yacht Designer/Builder

    Without a more defined design brief, I wouldn't want to speculate on propulsion hull form, etc.

    I suspect the old timer will build what he wants to build regardless of what the plans provided. This is more often the case then most realize, as the average owner couldn't tell the difference between 14 or 17 degrees in deadrise, if the builder "thought it should be this way". Most of the time they produce a boat that is inferior to the drawn plans, but it's difficult to compare so, they get away with it.

    I've designed quite a few elliptical stern craft and have specialized in shoal draft as in the Chesapeake and here in Florida, it's always been an issue with me. Who's doing the design work?

    You mentioned 25 knots as the top speed of the boats you're familiar with. Assuming they're around 40' LWL, at 25 knots they're pretty much up on full plane (2.9 S/L). Semi plane speeds (what most are capable of) would be from about 9 knots to near 20. Displacement would be below 8.5 knots of course.

    The displacement hulls will be the most efficient in fuel savings, with increasing speed, exponentially increasing fuel costs and HP requirements. This could be mitigated to some degree with a narrow beam/length ratio, but most working craft want the beam and just pay the price.
     
  6. ancient kayaker
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    ancient kayaker aka Terry Haines

    Lovely yes, and great for fishermen, but those round/ellictical sterns must be much more difficult to construct. Just in case you're thinking of getting serious.
     
  7. PAR
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    PAR Yacht Designer/Builder

    No they’re not as bad as you’d think Terry. The traditional way was vertical staves, which can be tedious, but not so tough. On my plywood designs, I use a conical section, which permits a piece of plywood to wrap right around with no trouble. On a planked hull, the planks take on some pretty weird shapes, but it can be done.
     
  8. Deadrise13
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    Deadrise13 Junior Member

    PAR, Thanks again for the input. I do understand your reservations on advice without facts. I will come back at a later date with more info as I get it. This prosses will take a year or more and there should be plenty of down time to look into the details. To the round stern construction process, I would not take it on myself but the gentelman that is going to build the boat has been doing it for 55 years. He is a native to Harkers island NC and we all know what has come from that readgen of the country in reafrence to uniqe desine. Caralina Flair, I would pick to top off the list. Forgive me I have only scrached the surface in my reaserch, but should know quite a bit more about there boat buildeing culture buy the end of this build. When I ask him how hard it would be to go round vs box he just laghed and said "It aint that bad, just takes a little longer". Thanks again for the continued input------
     
  9. PAR
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    PAR Yacht Designer/Builder

    Send me his name and where he works in an email, it's likely that I know him and can provide the "low down".
     
  10. BMcF
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    BMcF Senior Member

    Oh Leo..[sigh] there you go wanting the science to work again. :D

    This thread has been a hoot, simply because I live right where so many of those specific boats were invented, built..and rebuilt..and modified. I still drink a beer every now and then with Francis Goddard, Ben Goddard, Billy Deagle, Donald Thompson and a few others..the few who remain that banged out those things (and bateaus, skipjacks, buy boats, and various working skiffs) one after another. Not a one of them could probably even use a calculator..but all built beatifull vessels.

    Nearly all of the 'original' wooden roundsterns hereabouts (as differentiated from the box-sterns and drake-tails) have had what are called locally 'settling boards' added to them so they could benefit from the advent of V-8 engines that made a whopping 100HP (or more). 'Settling boards', quite simply, are big flat planks attached to the bottom of the hull and extending aft, supported by reach rods that are attached to the rising portion of the roundstern near or above the orignal displacement waterline.

    Thus is achieved speeds well above the orignal design, with the higher installed power of todays engines, of course. ... next time my pal Greg pulls his 1940s vintage roundstern with setttling boards out for annual paint, I'll try to snap some pics.

    St. Georges Island, MD
     
  11. Deadrise13
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    Deadrise13 Junior Member

    Hey BMcF, I think I have a pix I can scan of that plaining board. I will try to post it. THANKS FOR YOUR INPUT-----
     
  12. Deadrise13
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    Deadrise13 Junior Member

    PAR, I did send you an e-mail. Let me know if you did not get it!?!? Thanks
     
  13. Deadrise13
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    Deadrise13 Junior Member

    I think this is the plaining board BMcF was refering too. Sorry for the bad pix it is scaned out of the waterman of the cheasapeak bay book.
     

    Attached Files:

  14. BMcF
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    BMcF Senior Member

    Yes..quite the typical retrofit detail as seen from above the water. A crude but effective means of making a displacemnt hull at least a semi-planing hull....

    I've yet to see one of the roundsterns with the settling boards added reach the speeds the typical box-stern deadrise dories do with the same power though. That is just a personal observation of those here locally....
     

  15. PAR
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    PAR Yacht Designer/Builder

    Even with the bilge runners (settling boards), the displacement hull runs are usually too steep to permit much more then 2.5 S/L. They do help considerably at 1.5 to 2.5 S/L though, which is semi plane mode. A full plane hull can be developed with that stern shape.

    Greg, I did get your email and yep, I know him. I'll send you what I have in a few days. I got to go sit at a booth in a boat show, which I just don't like to do, but was talked into it.
     
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