Reality Check and Advice for Young Engineer

Discussion in 'Boat Design' started by PacificSails, Apr 13, 2015.

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

    Here we go again WindRaf. So tell us, how is a schooner hull different than a sloop? The above boat (my design) has three rigs available, a sloop, ketch or the schooner shown. The hulls are the same, though there are some appendage differences, which is understandable, but the hull's lines are the same and they sail well with all rigs. Of course each rig has it's advantages and disadvantages, but they all perform within the expected ranges.

    You make these nut job comments all the time, though most folks ignore you as your reputation points indicate, but maybe this time you can show us what you really know and explain why a sloop hull, isn't well suited for a schooner. Come on justify your statements with some knowledge and expertise. Please, as the first version of the 18' schooner above, is underway in Finland and maybe I need to warn the owner about how poorly suited it is.
     
  2. WindRaf
    Joined: Oct 2014
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    WindRaf Senior Member

    Different sailing rig, different centers.
    Different relationships between the centers.
    But not only the relationship between the sailing center and the center of drift.
    Changing the center of drift involves also the variation of the relationship between the center of drift and center of buoyancy
    Ergo different rig, different development of the hull.

    Of course there are those who mixes the wine with beer.
     
  3. WindRaf
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    WindRaf Senior Member

    I do not care, all those who have said the truth have always been marginalized by someone
     
  4. PAR
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    PAR Yacht Designer/Builder

    Lots of designs to your credit WindRaf? You're only marginalized by your own comments and inability to support the often ridiculousness of them.

    So, a schooner rig's centers (or any other rig for that mater), can't be balanced over a sloops hull, is this your assertion? What boring world you must live in. Good thing you weren't around in the old CCA rule days - you'd have had your transom handed to you by sloops, converted to yawls in every race.
     
  5. jimmoniky
    Joined: Apr 2015
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    jimmoniky New Member

    Hi, New here but having had a friend that converted a boat like this back in the 80's I was intrigued. He used a Cal 20, chopped of the whole deck and then glassed in plywood bulkheads and a plywood deck at the bow (maybe 10')with the rest an open cockpit. I helped with some rigging and hanging around drinking his beer. We sailed it a bunch of times on Lake Michigan. It was fun and worked quite well, but probably not as well as the original rig. I don't think he had any calculations of different centers of effort and all that, he just kinda made it up based on what looked right. I wish I had a picture or something.
     
  6. jimmoniky
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    jimmoniky New Member

    PAR,
    Do you know if the 18' schooner you referenced being built in Finland has been built with a different rig? I was wondering if you had a comparison of the way the schooner rig v. the sloop or ketch performed? Or maybe the larger design has actually been built with the different rigs so they could be compared on the same hull as it seems that most of the posts agree that a schooner rig doesn't perform as well especially in the size range.
     
  7. PAR
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    PAR Yacht Designer/Builder

    The Finland boat is my design, so I have clue about it's abilities. It is the first of this hull with the schooner rig, so difficult to compare with the other rigs, but no surprises have been found.

    The sloop is obviously closer winded than the ketch or the schooner and several of each have been built, all with similar performance envelop reports. The ketch and schooner share the same underwater profile, while the sloop has a different rudder and keel plan form. The ketch and schooner needed more lateral area, in places the sloop didn't have it, so the adjustment was made. This isn't an unusual thing to perform and many designs have optimized appendages for the rig it might sport. This isn't to say you can't take this optimization further, but it is to say you can put just about any rig on any hull, given a bit of thought, some basic math and eventual tinkering. It's just WindRaf has made these bland, sometimes grandiose comments previously, without any support for his assertions and I was just trying to pin him down for some refinement on the post.

    For example:

    Yeah, duh and your point?

    Yeah, again, duh, I'm sure you're going to point out why they don't work on different hulls right?

    I'm sure there's a point he's trying to make, but certainly not very defined, particularly in light of all the boats that have had these types of conversions done previously (read many thousands).
     
  8. sharpii2
    Joined: May 2004
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    sharpii2 Senior Member

    Just thinking aloud

    I'd take the original main and move it aft, so its mast would end up somewhere in the cockpit. Then I'd step a shorter mast where the main mast originally was, and use at least one pair of the original chain plates. I'd probably have to add at least one pair so the fore mast back stays would have sufficient drift.

    This fore mast would have a jib and a gaff fore sail.

    The main mast would have the original main sail.

    It would need at least two pair of chain plates, but probably three, so the original spreaders could be used. The fore and aft pair of these chain plates would have to be further apart than before, as there will be no single back stay, as there probably was when the boat was sloop rigged. There would be no fore stay either, for this mast.

    Attaching these to the hull could be a real pain.

    The hull will probably have to be locally re-enforced to take them. This will most likely mean adding laminates to the hull in that area, working in the cramped quarters of under the cockpit.

    Once the chain plates, some arrangement must be made take the compression loads of this mast. I'd consider putting a bulkhead, athwart ship under the cockpit, to spread the compression loads. Shaping that accurately and installing it securely would quite a challenge, to say the least.

    The new jib will probably need a bowsprit, as it will not be as tall as the original. Extending it over the bow will win some of that area back. Such would also probably be needed to get the proper balance for the original keel.

    If everything goes right, the boat should be able to sail under fore sail alone, or with just the jib and reefed main sail, with just a slight weather helm.

    Just my thoughts.
     
  9. WindRaf
    Joined: Oct 2014
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    WindRaf Senior Member

    profilo naso blu.png


    Bluenose profile.
    Schooner America the same.
    The center of the buoyancy is in correspondence of the main mast
    The sloop, ancient and modern, have the center of the buoyancy more forward.
    Normal.

    If someone were to turn Bluenose in sloop, would transform a masterpiece in a toilet.
     
  10. PAR
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    PAR Yacht Designer/Builder

    The schooners BlueNose and America aren't even remotely the same WindRaf and this is the point I've been trying to make about your posts. Talking out your butt about stuff you clearly don't understand, is the reason you're where you are. FWIW, America was a lousy schooner, an ill handling and balanced boat. In fact the recent reproduction, built on the original lines, has had it's keel deepened and it's rudder enlarged, just to address some of it's handling issues, of which the original also suffered from. The only thing these two boats have in common is the rig type and the general hull form shapes employed in their era. Both are very different comparatively. Just take a look at the lead used on both sail plans for a clue.
     
  11. WindRaf
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    WindRaf Senior Member

    'The same' relative to the center of buoyancy and the arrangement of the mainmast.
    This was the point of my post.
    Relation that there is also in the whole Malabar series.
    It was not an analysis of diffference between Bluenose and schooner America, but the point at issue that unites them as schooners - verso sloop
    The post was on the topic of the thread.
     
  12. WindRaf
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    WindRaf Senior Member

    Why you can never write a post without being rude?
     
  13. Skyak
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    Skyak Senior Member

    PS, my first thought from your original post was that the answer is 'yes it can be done, but no it should not be done'. The conversion will be costly, the result is unlikely to be desirable, and the process is no fun to say the least.

    Your motivation -small schooner as a fun sailer -is good and I second the recommendation that you build Bolger's small schooner. It is designed exactly for your purpose -delightful day sailing, and it is a very fast build. It will likely be cheaper than a conversion. It will certainly be quicker, and vastly more fun. If you sit low on the floor it will make a beautiful silhouette on the horizon.

    It is also the perfect project to prepare you to build a full size proper schooner.

    https://www.flickr.com/photos/hallman/tags/singlehandedschooner/
     
  14. pdwiley
    Joined: Jun 2008
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    pdwiley Senior Member

    Agree that POGO is damn heavy. It'd be better stretched - then it's resembling local crayfishing boats which are also pretty heavy. The weather and sea conditions where I live are *substantially* different to where you are so I don't regard some mass as a bad thing.

    However if I wanted a small boat I'd be very tempted to build that last one you show above, it's cute. Have to figure out how to graft in a small diesel inboard, though. I hate saildrives & outboards.

    PDW
     

  15. PacificSails
    Joined: Apr 2015
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    PacificSails Junior Member

    Hello everyone, thanks for all the responses and advice, it's good to hear some discussion on the subject.

    I'm leaning towards the suggestion of just building one rather than converting a sloop, and I agree those pictures posted by PAR are quite nice.

    Is it correct that more mass (below the center of mass) can make the boat more seaworthy (more stable, less likely to capsize, etc.), with a trade-off in speed? It seems intuitively true.

    Thanks again everyone,

    Matt
     
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