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Square Top Main  Bottom

  • In my haste to quickly purchase new sails last minute I ended up getting a square top. I do not know if it is more square footage or not. I am being told I should get an 8:1 mainsheet system as my 6:1 may not be enough, also, being told I may need a 5:1 down haul as my 3:1 may not be enough. These are unexpected expenses but don't want to get caught with a sail I cannot trim properly. It is for a gcat 5.7. I ordered a pin top off ebay just to be safe but the square top is in better condition. Have a long trip coming up and have some decisions to make. Thanks for any advice
  • Are these sails cut for the G5.7? Is the square top laminate? Do you have swept spreaders?
    and how long of a trip?
    I am sure you could "sail" with your current tackle. How well do you need to sail?

    --
    Robert
    81' NACRA 5.2 "Chris's Flyer"
    Previously owned H18, Trac 14, G-Cat 5.0, H14T, H16, N5.0
    BYC, Mobile, AL
    --
  • The 3 to 1 is not enough. You would have to be Superman to get the right downhaul tension. The same is true for the mainsheet. A 6 to1 is fine for a 5.0 but boomless boats like the 5.7 need more power partially because of the short foot. Perhaps you can contact the sailmaker to see if they added square footage. Generally speaking when a sailmaker converts a pin head to a square top they shorten the foot a little to keep the square footage the same. Don't know how well that would work on the 5.7 that has a short foot to begin with. Maybe you wound up with a larger sail.

    --
    Bill Townsend
    G-Cat 5.7
    Sarasota
    --
  • For what it is worth, most racing sailors use 16:1 downhauls on G-Cat 5.7 sized square top mains...and 10:1 or 12:1 mainsheet systems. I personally recommend 12:1, especially if you are doing a lot of sailing, but 10:1 is probably adequate and what I keep as a spare.
  • Interesting, and might explain, like a lot - my stock down haul on my H21 is only a 4:1. I THOUGHT I was getting a good bend on the mast but could never tell and have always been running overpowered in 12-15 knots wind. Though not the only reason, I'm sure. But 16:1 ??? - wow, I'm a bit off where I need to be.

    --
    Chuck C.
    H21SE 408
    --
  • When you are racing you want the downhaul to be easily pulled by your crew from either a sitting position or on the trapeze. That's the reason for all the power. They usually have some kind of swiveling cleat on each side of the mast so the downhaul can adjusted from either tack. If not racing, a cleat on one side of the mast will do and you'll get by with a lot less purchase but you'll have to pull with all your might. When you start getting above an 8 to 1 on your mainsheet remember that's a lot of line and you'll need the highest quality blocks you can buy. Also in light air, the line won't play out as efficiently so use the smallest diameter that you can still grip effectively.

    --
    Bill Townsend
    G-Cat 5.7
    Sarasota
    --
  • charlescarlisI'm sure. But 16:1 ??? - wow, I'm a bit off where I need to be.

    Most of the 16:1 downhauls I have seen are internal to the mast, and the mast is carbon fiber. Their sails are cut differently than your is. Your GCat will do fine with a 7 or 8:1 downhaul.

    shortyfox A 6 to1 is fine for a 5.0 but boomless boats like the 5.7 need more power partially because of the short foot

    Really good point. The difference between 8:1 and 10:1 (especially on a mainsheet) is significant, and the extra line on the deck is a PITA.

    --
    Sheet In!
    Bob
    _/)_____/)_/)____/)____/)_____/)/)__________/)__
    Prindle 18-2 #244 "Wakizashi"
    Prindle 16 #3690 "Pegasus" Sold (sigh)
    AZ Multihull Fleet 42 member
    (Way) Past Commodore of Prindle Fleet 14
    Arizona, USA
    --
  • klozhald
    charlescarlisI'm sure. But 16:1 ??? - wow, I'm a bit off where I need to be.

    Most of the 16:1 downhauls I have seen are internal to the mast, and the mast is carbon fiber. Their sails are cut differently than your is. Your GCat will do fine with a 7 or 8:1 downhaul.

    shortyfox A 6 to1 is fine for a 5.0 but boomless boats like the 5.7 need more power partially because of the short foot

    Really good point. The difference between 8:1 and 10:1 (especially on a mainsheet) is significant, and the extra line on the deck is a PITA.


    16:1 is an external system common on most F18's. Essentially you have a 8:1 setup that goes to a pair of blocks on the clew of the mainsail. Details here: https://www.catsailor.com/forum/ubbthreads.php/topics/196604/all/viper-cunningham

    The Nacra Evolution manual also has great rigging diagrams for easy reference!

    Yes, these boats have larger square tops with a bit more draft in them to give a larger operating range during racing.
  • Not to drag the thread too far, but I am thinking about a new set of sails for my H18 - and Whirlwind has a couple of square-top options.

    What issues should I keep in mind in making that choice?

    --
    Tony H
    Hobie 18
    Sailing Mission Bay and nearby CA
    --
  • For your location, I would probably go for the biggest square top possible.

    Issues to consider are the running rigging, as discussed here. While not a “must”, an 8:1 mainsheet abs 8:1 downhaul will make sailing with the new sail more pleasant. I would recommend Pentex Apen 06 for the cloth, it is nearly indestructible.
  • you need at least 6:1 downhaul and 8 or 9:1 main sheet to control the shape of your sails easily.
    I have a downhaul 6:1 on a Gforce 21 with NEW Glaser squareTop (2019) and it works but JUST and it is very simple but it takes a fair amount of strength to pull. I know because I also recently acquired a Falcon F16 with a cascade 12:1 and it is much easier to adjust often and quickly.

    --
    Colin
    Hobie 14, Hobie 16
    Gcat 5.7, Gforce 21
    Falcon F16
    sailing Connecticut Fishers island sound
    --



    Edited by colinress on Mar 14, 2021 - 11:35 AM.
  • I upgraded my 5.0 in 2011 with a square top main. The gain of square footage is not the biggest deal (maybe under 1m²) but the force center changes. The 6:1 sheet isnt enough. 8:1 makes sense. But really fun is the 10:1 system i have since last year. Total control at the sheet.
  • Don't forget your traveler. You'll do a lot more controlling with the traveler than you did with the pintop.

    --
    '82 Super Cat 15
    Hull #315
    Virginia
    Previously owned: '70 H14, '79 H16, '68 Sailmaster 26, '85 H14T
    --

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