Maybe, maybe not

Discussion in 'Boat Design' started by valery gaulin, Oct 23, 2021.

?

Should I build?

  1. Maybe

    88.9%
  2. Maybe not

    11.1%
  1. DogCavalry
    Joined: Sep 2019
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    DogCavalry I aim to misbehave.

    Thanks Martin!

    Bien Sur, Valery. As @bajansailor says. I am comedy central on here.
     
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  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    'Comedy Central'?
    Non!
    Far from it - your epic threads and photos are an excellent education in wooden boat building with strip plank and plywood.

    You just need that YouTube channel now - and if it 'goes viral', it might pay for an engine (or two) - who knows?
     
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  3. sharpii2
    Joined: May 2004
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    sharpii2 Senior Member

    You can probably get the general sailing qualities from a scale model.

    But don't expect it to sail in the kinds of wind that the full sized version will.

    The important info is whether or not the balance is right, and whether or not the bilge keels have sufficient area.

    You can probably also find out its windward capability.
     
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  4. valery gaulin
    Joined: Jan 2017
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    valery gaulin Senior Member

    As I am not a sailboat designer this is the reason why I am building a scale model. I heard some where that at 1/10 th the scale it should be possible to start seeing major flaws!

    The wind gradient at very low altitude is not at all the same as it would be at actual size.

    I also do the model to get a sense of the size and space using a scale human model. 3D drawing is good to figure out all this but it is never the same as real world!

    I am taking a big risk with this design as I know that I am stretching the dimension for a 26 foot sailboat/motorsailer to have headroom, as I am 6'2" tall. Freeboard is high and might create undesirable traits when going upwind. This is the reason why I gave a strong sailplan with low center of effort, 550 sq. Ft. The form stability should be able to sustained to sail area combine with the 4 feet draft bilge keel each 1100lbs for a total 2200lbs of keel ballast.

    I am affraid to have the wrong balance between the COE and the CLR. and having sufficient keel lateral area.

    I just don't want to design a pig! But I want maximum living space in 26ft x 10ft X 4ft! Very contradicting.

    I already dsicussed with a naval architect to run some CFD analysis. To find out the keel size, sail plan location and 2 hull efficiency iteration. I still did not gave him the OK yet because I am saving a little more money!

    I am bias but I actually really think the look of my design is cool looking! Kind of boxy but with descent line and a spacious protected center cockpit pilothouse area.
     
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  5. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    Hi Valery,

    My Dad had that boat around 10 or 12 years, he likes to build things... that's the interest, like lots of boats not so much use. Mostly just used as a weekender and general distraction. When he sold that he went halves in a Thunderbird class yacht with an old workmate and had some fun in that, actually good to share the sailing and work.
    All the best from Jeff.
     
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  6. sharpii2
    Joined: May 2004
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    sharpii2 Senior Member

    I think your design has too much Sail Area for its intended purpose.

    Motor sailors typically have less Sail Area (SA) than pure sailboats. This is because they usually use their engines in light wind conditions (as you pretty much stated you would do).

    Being that you intend to work the rig from below deck adds more reason to go with a smaller sail plan.

    Imagine sailing on an almost ideal day, with just the right amount of wind. Then, suddenly it really starts to blow. How are you going to quickly reef?

    With this huge rig, you would have to let go three sheet lines, or round up into the wind, to avoid being knocked down.

    Then, you will have to stay in that condition until the squall either ends, or you manage to shorten sail somehow.

    With a rig the size you intend to have, it won't take much of a squall to make this happen.

    When I figure the keel area for one of my designs, I add everything above the WL to the SA.

    My closest guesstimate is that your design will need about 17 sf of keel area to work reasonably well. You specify only 12 sf (2ft x 3ft x 2).

    I suggest you make two changes:

    1.) Reduce the SA by about 1/3rd to about 365 sf, and
    2.) Increase the chord length of your keels by 50% to 3 ft.

    This will leave you with a Sail Area Displacement ratio (S/D) of about 15, which is considered reasonable for even a pure sailboat, and keels that are long enough to have their ballast stored lower. They would also be far less likely to stall.

    True, your whetted area would go up. But whetted area is far more important on a pure sailboat than on a motor sailor, for reasons stated above.

    I suggest you complete your model with the sails and keels you originally planned on. If the model doesn't work, try making the changes I suggested.

    Now that I have looked at it a few times, I like your general idea. There's a lot to be said for a sailboat designed more for comfort than for performance.
     
    Last edited: Nov 25, 2021 at 4:55 AM
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  7. valery gaulin
    Joined: Jan 2017
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    valery gaulin Senior Member

    Thank you so much for your input! You might be totally right about my sail area being to large and my keel to small! This is exactly why I am building a model to see the balance.

    I mention motorsailer because my design as too many compromise to be a very good sailboat! Therefore all the negative aspect will be accepted as motorsailer.

    But I still want this boat to be a good sailing craft, in my area in the summer wind is low, 2-6 knots wind for july and augaust is the average! Full main, full staysail and full yankee.

    In the fall september and october wind goes way up 15-25 knots is not uncommon. Double reef main with staysail should balance the boat OK!

    Now how to quickly reef, good question! With my unexperience sailor/designer with cutter rig as drawn, kind of more traditional proportion, I was thinking that I could drop the main and roll the yankee. Keeping only the staysail out for that blow that came in unexpectedly!

    I might be wrong about quickly dropping sail!

    Thank again very much for your input sharpii2.

    I will keep in mind your suggestions of 1/3 reduction in sail area and inceasing my chord lenght to 50% for the keel! It would actually help building stronger keel!
     
  8. clmanges
    Joined: Jul 2008
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    clmanges Senior Member

    The larger the scale the closer you get to real-world performance, and especially, it allows the use of more accurate copying of full-sized materials. The model you've done is very nice, but for the next one you might consider hobbyists' plywood instead of balsa. You can get aircraft-grade plywood in thicknesses at least down to 1/32", and its physical characteristics will more closely match full size.
    Junk rigs are good for that. You can reef as much or as little as you like in seconds without ever having to leave the cockpit.
     
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  9. CT 249
    Joined: Dec 2004
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    CT 249 Senior Member

    You can reef a modern rig in seconds, and depower it as much as you like in seconds, without leaving the cockpit. Our boat goes from 0-25 or so knots without needing a reef, and it's quicker than a junk rig all through that range. With a modern rig you also don't have to pull up those heavy battens every time you sail, and you don't have a whole bunch of sheetlets flapping around.

    The claims that JR fanatics make about the "problems" of modern rigs are often absolute rubbish.
     
  10. CT 249
    Joined: Dec 2004
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    CT 249 Senior Member

    When you say you'll drop the main, what's going to happen with it? In 25 knots many mains flog and flap when dropped, so you will probably have to get on the cabin top to stow it.

    If you're going to round up to drop sails, and as they flap as you drop or reef them, you'll be experiencing high side forces and very high wind drag. In those situation, foil size is important. Small rudders and keels can stall if you're moving slowly and trying to round up, so as Sharpii says making them much bigger could be a major advantage.

    Low aspect rigs develop their optimum drive at wider angles of attack than high aspect ones, and I think they therefore develop higher side loads. That's one reason why designers in gaff rig days had so much keel area much of the time. Herreshoff, Watson, Payne, etc were not fools. In the 1890s they reduced lateral area faster than anyone ever has before or after, but they only did so when they increased draft to compensate for reduced area, and they did it with very low-freeboard hulls with much smaller rigs than in older gaffers. An 189s gaffer like Linton Hope's Sorceress or Sibbick's Unorna had a higher-aspect keel than most modern boats - but they were also deep. If you match a hull and rig with high side loads and low speed with small high -aspect foils you're very likely to be in trouble if you try to go upwind, even to tack.
     
  11. valery gaulin
    Joined: Jan 2017
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    valery gaulin Senior Member

    I did use hobbyist plywwod, very thin birch plywood. The reason it looks darker in alot of area on the hull it is because I used putty to fair the hull. I actually screwed by not using enought station/ bulkhead to hold the shape! I had to add station/bulkhead after the fact! I learned that when I will built full size to properly old the shape I need more station even if they are temporary.

    I did actually contemplate a single large junk sail! But after my calculation the weight of all the battens was way to much!!! I investigated with a large lugsail with batten similar to what Nigel Irens did with Romily! Weight was much better than a Junk sail. Still this single lugsail solution is still on the table!
     
  12. valery gaulin
    Joined: Jan 2017
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    valery gaulin Senior Member

    Thanks for your comments! They all make sense and will for sure think about it.

    Right now I sail a 1973 Grampian 26. When wind pick it and need to drop the main it get stuck alot of time in the track unless pointing perfectly into the wind, even then I still need to go jn the cabin top to pull on it! I hate to do this and don't want this situation with this sailplan! My thinking is that the gaff combine a laced mainsail will be heavy enought to help drop the sail. The yankee would be on roller furling system single line type with soft luff that would be full in or full out. So that I can bring the bowsprit in for the marina. The staysail will probably be hank on and boom with one reef and self tacking.

    If I feel curagious a large asymetrical spinaker could be flowed instead of the yankee! But this will be only to show off when other sailboat think I am a slow motorsailer!!!! LOL

    I keep all your comments and seams to all direct to larger keel with more lateral area. I will in my model try to allow different keel to be tested easily to see the pros and cons of them all!

    Thanks again!!!

    PS: By sharing my concept on this website I was expecting more people to bash my design! This way I would not have to go ahead into insanity and actually go about building this sailboat!
     
  13. sharpii2
    Joined: May 2004
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    sharpii2 Senior Member

    Would you please explain what you mean by a "modern rig"?

    Do you mean a fractional sloop with a "flat top" main?

    And, if so, how do you reef the relatively large main "in seconds"?

    I personally know of two options:
    1.) an in boom roller-reefing system, or
    2.) a slab-reef, "jiffy-reefing" system, with a dedicated tack and clew line, each needing to be separate to be really effective (the tack and clew need to be, not only pulled down to the boom, but firmly pulled to its ends). This means you need one pair of such lines for each reef point. And there is generally just one winch on the mast to handle this job. So the first reef can go relatively quickly. But the second one?

    Am I missing something?

    Also, a gaff sail can come down rather quickly, but only under these two conditions:

    1.) The sail is luffing into the wind (so it doesn't hang up on the shrouds), and
    2.) There is a system of "lazy jacks" to contain the sail cloth, as the gaff comes down.

    A gaff main can be quickly depowered by releasing the peak halyard, or simply loosing it.

    I agree that the Chinese lug (aka the "junk rig" is a bit over rated. But it does have virtues that I see as un matched.

    The quick reefing is certainly one of them. Just relieve the halyard until the boomlet reaches the boom, then you're done.

    The sail cloth is likely to last a lot longer than it will on more conventional sails.

    These are the two virtues I see as pretty much unassailable.

    But then the vices start stacking up.

    The first big one is the weight of all those boomlets. This can be a major stability consideration.

    The second big one is that it is relatively difficult to get an airfoil sectional shape for the sail cloth. There are two popular methods to do this. Neither one allows for an adjustable airfoil depth.

    The third big one is that the sheet line must end a considerable distance from the aft end of the boom. This why we see a lot of single-sail Chinese lug rigs.

    The flat head Bermuda sail is said to require exceptionally strong sail cloth to work well. I also haven't heard much on the durability of this type of sail.

    I understand that in racing durability is not high on the priority list (newer sails usually mean a faster boat). Nor is lower cost.

    The flat-head main may be an excellent sail for racing and other high-performance uses (such as on fast multihulls), but whether or not it's really the best deal for everyone else remains to be seen.
     
    Last edited: Nov 27, 2021 at 6:27 AM

  14. sharpii2
    Joined: May 2004
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    sharpii2 Senior Member

    Valery.

    I see one major likely flaw in your concept.

    What you have is essentially a covered porch, with standing head room, with the sail rig above it.

    The question I have is: how are you going to be able to see the sails when you work them?

    I once worked on a design which was supposed to be a live-aboard ocean sailing boat, with a length less than 40 ft. I wanted as much cabin volume, in the sharp, double-ended hull as possible. So, I went with a raised deck.

    The problem quickly became apparent. If I was to work the sails from the deck, the boom would have to be about 4 ft above it. I found that unacceptable.

    So I had the boom just high enough above the deck to fit a decent vang under it. I then steeled myself for the necessity for working the rig from below.

    I had a strategically placed hatch for dealing with the halyards, but, with standing headroom below, how was I to reach them?.

    I came up with an odd idea. I would place the pantry box just behind the mast and put toe-rails around its top. I would then stand on top of it to have my head and shoulders above the hatch coming to get at the halyard.

    Probably not the best idea. But one virtue is that, if the boat suddenly rolled, I would not likely be thrown overboard. But imagine dealing with this in a rain storm. Most sailboats have trunk-cabins for a good reason.

    A few possible suggestion:

    1.) Have the cockpit roof lower than standing headroom. Then you can have a hatch in it from which you can work the rig (while standing up).

    2.) Have a bridge-deck high enough to get your head and shoulders through a hatch to get to the halyard.

    Watching the sails can be another problem to consider. How are you going to see what the main is doing through the cockpit roof?

    Maybe you can use closed-circuit TV.
     
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