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Sail trim quiz question

Discussion in 'Sail Trim with Don Guillette' started by Jackdaw, Nov 29, 2017. Add this thread to a FAQ

  1. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    563 posts, 138 likes
    O'Day 19
    US Littleton, NH Littleton, NH
    Hey, me too. :yikes:
    well... the software engineering is just an element of my Applied Computer Science degree.
    -Will (Dragonfly)
     


  2. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    563 posts, 138 likes
    O'Day 19
    US Littleton, NH Littleton, NH
    Nobody is questioning anyone's credentials. We are just getting to know each other.
    Now, back to the analysis.
    What part of the forward driving force does the main contribute to the overall driving force and how much is straight heeling force?
    - Will ("just the facts, sir", Dragonfly)
     


  3. Jackdaw

    Jackdaw

    Joined Nov 8, 2010
    7,523 posts, 1,348 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    Hey, who are you? Ask them to shut down one of your own threads. We're having fun here.
     


    Will Gilmore likes this.
  4. shemandr

    shemandr

    Joined Jan 1, 2006
    2,961 posts, 258 likes
    Marblehead Skiff 14'
    US Greenport, NY Greenport, NY
    Yeah! This is better than part # discussions.
     


  5. BobbyFunn

    BobbyFunn

    Joined Apr 16, 2017
    83 posts, 42 likes
    Hunter 170
    US FL Tampa
    I just like anything to do with sailing, not here to learn plumbing or debate if we should crap in buckets, bowls or over guunals. Please dont kill this thread.

    View counts support that as well.
     


  6. BobbyFunn

    BobbyFunn

    Joined Apr 16, 2017
    83 posts, 42 likes
    Hunter 170
    US FL Tampa
    If you thought the upwind test was an abomination of scince youll love the broad reach one. I should inform you though that on my rc boat the jib and main can only go out so much. I know the sails ahould go out more. It more or less stalled.

    Second on a rc boat tbe headsail has a boom. This boom swings in an cone shaped arc not a flat "sector".

    The redirction of air 90 degrees is cool. I think there is a huge circulation between the mast and head sail that dominates. I like how the incoming air is redirected, and lastly, the looks to be a pileup of air at leading edges if both sails.

     


  7. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    563 posts, 138 likes
    O'Day 19
    US Littleton, NH Littleton, NH
    Ah, I see the problem now. Your sailmaker cut your sails too flat. There's no camber at all. :frown:
    No wonder you need so much wind.
    Love the wand. That is so cool, SO COOL! :plus:
    If I get the time next summer, I'm tinseling my mariner up.
    - Will (Dragonfly)
     


  8. BobbyFunn

    BobbyFunn

    Joined Apr 16, 2017
    83 posts, 42 likes
    Hunter 170
    US FL Tampa
    May i suggest your crew wander the foredeck with a telltale wand? Yeahhhh.

    The sails were drawn up on sailcut and they are broad seamed. I noticed on the upwind test that there was too much camber so i got a hole punch and made a new clew. The headsail was originally shaped to have a full profile from luff to leech. Based on this thread im using the headsail for the first 25-30% of profile. That means the tack and clew were pulled tighter. There is still shape. It doesnot lay flat on a table.

    I placed tinsel on rigging and one trip on the trailer messed it up. They all braided themselves together while going 60mph down highway. Then i was mortified to see some strands break off and fall in the water. Im open for ideas for removable spreader tinsel. It was fantastic for the calm days.
     


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  9. BobbyFunn

    BobbyFunn

    Joined Apr 16, 2017
    83 posts, 42 likes
    Hunter 170
    US FL Tampa
    That is by design.
    This was a low budget entry level "paradise" brand model. I was in Kansas and into rc airplanes, it was always too windy and got tired of either crashing them or waiting fir calm days. Its really only calm in kansas city for about half an hour at sunset. If you dont get off water fast you end up paddling home or in my case watching a reflection of a sailboat ghost back to me.

    Rc sailing was a perfect replacement. The model i got had terrible sails, and i was always putting on my homemade "reef" sails.

    I eventully cut 8 inches off the mast, built a new heavier keel, and settled on a set if sails for the 15-20 mph lake.

    That video upwind? That was closer to real world than you think.

    My rc boat is more "bluewater" than my 17 footer.
     


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  10. Davidasailor26

    Davidasailor26

    Joined May 17, 2004
    907 posts, 103 likes
    Beneteau Oceanis 37 LE
    US Havre de Grace
    In addition to the way the jib “heads” the main, the main tends to bend the wind coming into the boat into an “upwash” which lifts the jib a bit. In that sense you should be able to point higher with both sails than just the jib.

    While easing the jib would reduce healing moment, it wouldn’t help reduce rounding moment. The problem is that the center of effort (COE) of the main is behind the center of lateral resistance (CLR) (roughly the keel). Therefore the tendency to round up is driven by the amount of force on the main. If anything the jib helps hold the bow down because its COE is in front of the CLR.

    Caveat - on a broad reach when the sails are eased further from the centerline the forward pull of the jib could provide some rounding moment, since its COE is far to leeward, pulling the leeward side of the boat forward. But that doesn’t really apply going upwind with sails close to centerline.
     


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  11. jwing

    jwing

    Joined Jun 5, 2014
    292 posts, 72 likes
    ODay Mariner
    US Guntersville
    The upwash from the main that lifts the jib increases the forward driving force of the genoa. How much? It depends.
    The mainsail shape affects heeling vs. forward drive, too. How much? It depends.

    This may be of particular interest to you, Will. I bought a new mainsail for my Mariner, and when I installed it I also switched the mainsheet from the fixed point on the swing keel housing to a bridle pseudo-traveler (This is a super easy modification.). The vang takes over as the boom-height controller. The magnitude of the result startled me: less heeling + more speed = lots more sailing pleasure. Since I changed two things at once, I can't say which ha more effect. But I ain't changin' back to find out.
     


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  12. JRacer

    JRacer

    Joined Aug 9, 2011
    589 posts, 120 likes
    Beneteau 310
    US Wichita, Kansas Cheney KS (Wichita)
    We average 15. It's either blowing zero or 30! :biggrin:
     


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  13. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    563 posts, 138 likes
    O'Day 19
    US Littleton, NH Littleton, NH
    Thanks jwing, for your response.
    Did you post this on the mariner web site? I would love to see a picture of it.
    My boat is still setup with the original sheet configuration. I don't have a vang but I am planning to make one.
    -Will (Dragonfly)
     


  14. jwing

    jwing

    Joined Jun 5, 2014
    292 posts, 72 likes
    ODay Mariner
    US Guntersville
    I didn't make any photographs, but I plan to next spring. I will post them to usmariner.org
    This diagram is a good illustration of what I did, except instead of two #2148 blocks at the end of the boom, I used one block with a becket:
    [​IMG]
    For a discussion on how long the bridle should be, see http://www.wayfarer-international.o...iggingTips/UncleAl/Bridle/bridle_length2.html
     


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  15. Jackdaw

    Jackdaw

    Joined Nov 8, 2010
    7,523 posts, 1,348 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    Some may know this straight off, but for the rest:

    Why is this bridle better than attaching the mainsheet directly to the deck??
     


  16. BobbyFunn

    BobbyFunn

    Joined Apr 16, 2017
    83 posts, 42 likes
    Hunter 170
    US FL Tampa
    I asked myself that same question an stared at this like it was an invisible picture.

    It seems like a pain to have all that clutter in the cockpit & and the rudder.

    The key is that yellow line under tension. Thats an awesome technical drawing. Instead of the mainsheet pulling the boom down to center cockpit floor, it is pulling the boom to a point off center towards the starboard stern. This is closer to the angle the boom is supposed to be moving versus beong pulled up and down.

    I kinda like the rs boat that has the bar reaching up to boom. Does the same thing but in a different way.
     


  17. Apex

    Apex

    Joined Jun 19, 2013
    621 posts, 47 likes
    Oday 28
    US Muskegon
    Are you asking or fostering additional comments?
     


  18. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    563 posts, 138 likes
    O'Day 19
    US Littleton, NH Littleton, NH
    I'm going to say not exactly. The results of that particular type of traveler would be exactly the same if you pinned a block to the point where the yellow line crosses over the tiller. In part, that system is designed to make room for the tiller, allowing the sheet to pull from the back of the boom where it has the most leverage rather than from mid boom where it needs more mechanical help from heavy blocks. Because it is limited in its travelling and the angle is more acute, when the sail is out on a broad reach, the boom rises a little more and bellies, that's why jwing added a vang. It can't pull the boom to center because the yellow line is too long. However, you can take up the traveler cord by putting both ends on cam cleats for that close haul. That would allow you to get the boom to midship and point higher.
    My opti had a string traveler with the sheet on a pulley. I use to contemplate for hours about why that was a better system than one that was pinned like jwings. The answer was in the lack of vang.
    - Will (Dragonfly)
     


  19. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    563 posts, 138 likes
    O'Day 19
    US Littleton, NH Littleton, NH
    Lol! Yeah, jackdaw, you really want to know? ;)
     


  20. jwing

    jwing

    Joined Jun 5, 2014
    292 posts, 72 likes
    ODay Mariner
    US Guntersville
    That may be the case for the diagram I copied, but it is not necessarily the case for all bridle arrangements.

    Adjusting the bridal like that will pull the boom down, thereby defeating the purpose. But it is true that the system illustrated in the diagram cannot bring the boom windward of the block that is tied to the bridle.
     



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