Why do uni-rigs have such longer bridles and shorter forestays compared to other Cats i know the difference is for jibs but why dont the use short bridles and long forestays like the others whats the reason/purpose.Never knew or understood why.
edited by: brjonair, Feb 06, 2010 - 09:43 PM
Question on Uni-rigs
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Posted: Feb 06, 2010 - 08:45 PM
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Posted: Feb 06, 2010 - 10:32 PM
Less force pulling in on the hulls.
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Ron
Nacra F18
Reservoir Sailing Assn.
Brandon, Mississippi
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Posted: Feb 07, 2010 - 04:51 AM
if you want to fly a jib you need a central single forestay to fly it from
the height of the bridal determines the size of the jib as it has to fly above the bridal
so the lower the bridal the bigger the jib, but this increases side loads on the bows, bad
on an una rigged boat, no jib means they can have the bridal much higher and so reduce the loads on the bows
ideally, from a structural loading POV, on a una rigged boat you would have 2 forestays, 1 going to each hull
nacra did this on the 18square and the f17 i think
on my nacra 5.2 the jib flys quite high so you can see under it when sailing and avoid collisions
make the bridal too low and you are cutting out visibility and also pulling in the bows too much
later nacras wanted the extra sail area and so use a bridal foil to get the jib lower and also reduce the pull in forces on the bows, but that was extra weight, cost and also required a window in the jib
good video here showing a nacra 6.0 with bridal foil, pelican striker and all, so a bigger jib could be flown, no window either so the crew has to help the helm avoid collisions at 18knots
while we are on about sails
some nacras have booms, some don't
with a boom the sail can go behind the blocks, as the blocks are generally on the rear beam this means more sail area, good
with boomless the sail has to end before the rear beam or sheeting it will pull it into too full a shape, bad
to get the lost sail area back, boomless boats often have the sail coming further down the mast, almost to the tramp
which means a window in the main is needed and the crew have difficulty getting under it during tacks
but they don't get hit in the head
swings and round abouts
edited by: erice, Feb 07, 2010 - 04:12 AM -
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Posted: Feb 07, 2010 - 11:50 AM
Nacra F17 has a similar bridle set up has the 5.2
F17 shown with the jib kit -
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Posted: Feb 07, 2010 - 04:55 PM
my bad
not the nacra f17 but the nacra/inter 17
edited by: erice, Feb 07, 2010 - 03:55 PM -
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Posted: Feb 07, 2010 - 09:04 PM
Thanks that makes alot of sense never knew why its nice when you can learn something everyday,Thank you much appreciated
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Posted: Apr 27, 2010 - 02:11 PM
I sailed my 5.2 the other day without the jib due to inexperienced crew and high winds. I was only able to tack once without having to do the "reverse rudder and back up" technique and not gybe. Is there a trick to tacking without the jib? I can't remember but I may have only had one of the daggerboards down when I did tack successfully, and which one was down I don't remember. Would the daggerboard position even matter? -
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Posted: Apr 27, 2010 - 03:00 PM
daggerboards would def make a huge difference, esp with no jib.
when tacking with a jib - the jib will quickly be backwinded and help you turn by pushing you around. without a jib you must have speed and gently turn (getting the bows through the turn).
Daggers act as like rudders and help "bite" into the water. without them your hulls are sliding sideways and insead of a nice smooth steady turn, you are being pushed backwards (again and sliding sideways) through your turn.. making it much harder (if not impossible) to tack.
Dagger-less boats have a different shaped hull and the entire hull is usually pointy and acts like the board.
PS its is the INSIDE board that matters the most for tacking (if you are tacking to port, the port board) -
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Posted: Apr 27, 2010 - 03:59 PM
Also make note of your traveller position when trying to tack without a jib. Usually when you depower by removing the jib, you are also having the traveller out to dump off air as well. However you can't point as far into the wind that way so it is harder to tack since you have further to rotate. So before you tack make sure to pull in the traveller and point higher into the wind before starting the tack. That is usually one probably I have when out in high wind and my jib furled.
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‘92 H18 w/SX wings
‘95 Hobie Funseeker 12 (Holder 12)
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Posted: Apr 27, 2010 - 04:22 PM
Understood on the daggerboards intent, knowing that is the windward one being the more important one to tack helps, thank you.
And good point on the traveler position, I doubt I was bringing that all the way back to center before the tack. Probably tried to make the turn too quickly too. Thanks guys. -
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Posted: Apr 27, 2010 - 04:30 PM
not sure why you would not have your boards all the way down with the exception of shallow water or going downwind with a spinnaker (unlikely on a 5.2 but possible) but the boards are key to better tacking in all air conditions.
Also, it should be noted that it is VERY easy to blow a tack in heavy air. I blew several last week with jib/boards/exp crew etc.. it took me at least 3 or 4 tacks to find my rhythm in heavy air.. -
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Posted: Apr 27, 2010 - 05:12 PM
Andrew,
In heavy air couldn't you raise the dagger boards some to give you more side slip through the water to help reduce being overpowered. It wouldn't help you get where you are going faster, but might help keep you upright.
Except for shallow water I leave my daggers down. I agree it is easy to blow tacks in heavy air, especially if you are sailing a uni-rig.
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Scott,
‘92 H18 w/SX wings
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Posted: Apr 27, 2010 - 05:54 PM
hmmmmm, interesting point and perhaps we need to get some engineers in on that one .... I am not sure... but i have never heard that as a method of de-powering
I would say... that you would definatly slide you around, but you could lose a bit of steering, ability to point high (i.e. "pinch" which is critical) and would cause you to have to tack/gybe more to get home (unless you are right near the beach and slide home).
It MIGHT actually decrease your ability to heal without capsize as he boards provide resistance to healing motion and this is especially desired when you get hit with a gust of 30 or more... but on the other hand.. maybe you wouldn't heel so hard if you get pushed sideways....
Curious to hear what the others think -
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Posted: Apr 27, 2010 - 05:55 PM
on my 5.2 i often leave the jib off in high winds
when it's really blowing and i'm soloing it's almost guaranteed to go into irons as the forces trying to weather-vane the rig and hulls overcome the boats momentum going through the tack
the way around this is to reduce the weather-vane forces by not just releasing the mainsheet during the tack but by also releasing the traveler
with the travel released the weather-vane action of the whole rig is greatly reduced as it simply pivots on the turning hulls. this allows more momentum to the hulls around
but you're not sailing on the new tack yet as the rig is still idling, the boat would have lost most if not all hull speed now so the daggers and rudders have very little bite so it is very important to pull in the traveler SLOWLY and keep steering off the wind onto a broad reach until boat speed builds, the daggers start biting etc.
if you just haul on the traveler you are likely to pull the hulls around back into irons
once the boat is well underway on something like a broad reach, perhaps with only half the traveler pulled in, (depending on wind strength), the rest of the traveler can be pulled in and the boat pointed higher to make ground upwind
so to summarize, when sailing a sloop on main only in high winds, once you blow the first tack with your usual tacking method, and have to back out of it, start releasing the traveler, get the boat well across the wind and then SLOWLY bring it back in
edited by: erice, Apr 27, 2010 - 05:01 PM -
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Posted: Apr 27, 2010 - 11:38 PM
. . . that maybe you should lay off the double rummies?
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Philip
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Posted: Apr 28, 2010 - 03:01 AM
as far as i'm aware it is accepted practice to raise the daggers half way on older nacras when reaching in 20+knot winds
there are 2 reasons for this
1. when reaching in those conditions there is no problem flying a hull, rather the hull flies too much and the boat could easily capsize in a strong gust. lifting the boards half way allows the boat to side-slip more in gusts and so gives the helm more time to control the mainsheet and prevent tip-overs, the helm will automatically point higher to get to where he wants to go and with less working of the mainsheet and/or less travel on the traveler
2. daggered nacras have always had deep,large area boards that are great for pointing. but on the older boats at least they were made with a heavy, sold resin core that will break before it flexes much
reaching with 2 on trapeze, to try and keep the boat flat, in howling gales means the boards are dealing with huge side loads that can and will snap boards off. typically the leeward board goes 1st, soon followed by the windward board, if it isn't pulled up quickly, now has to handle an increased load
boarded boats without boards become large bits of driftwood with only limited downwind control
so, if you have 2 on trap and gusts still send the hull skyward it pays to get the boards up and reduce the loads on them
edited by: erice, Apr 28, 2010 - 05:04 PM -
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Posted: Apr 28, 2010 - 09:01 AM
Great info on the daggerboards, mine are definitely the solid, heavy ones.
I know I was releasing the traveler once I started my tack but where I went wrong was not pulling it in before attempting the turn in order to point further up wind therefore making my turn that much longer which would require more momentum to complete it successfully. -
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Posted: Apr 28, 2010 - 10:02 AM
hahah.. double?
i only drink singles. How can anyone drimk more than 1 bottle a day? -
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Posted: Apr 28, 2010 - 10:45 AM
[quote=andrewscott]
Well by sharing with others of course!
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Posted: Apr 28, 2010 - 11:52 AM
yes, you've got to be sailing as high as possible, and that means traveler centered, before initiating a tack on a cat
seen a h16 trying to to do 180 degree tacks with his traveler half out in high wind
was slowly going backwards across the lake
later he said
"but aren't you supposed to travel out when the wind is strong..."
yes, but light weight, high drag (2 hulls) cats can only tack through 90degrees in medium to strong air so you have to be sailing as high as possible before you start the tack or you'll never make it all the way through
