So I went out Saturday on Lake Lanier in the first reasonably windy day since I bought the boat in May (15knts gusting 18). I found that when flying a hull (first time and nearly always unintentional for now) the leeward hull buries very quickly. Even though there is enough forward hull volume - it just freaks me out! It was only myself and my 7 yr old so combined weight around 240/250lbs
So I have read that to alleviate this I could either a) rake the mast back or b) set the traveller out further or c) both.
Don't know if I need to be concerned with the setup of the boat but when I look at videos online of Nacra's flying hulls the leeward hull does not seem to bury as much.
Would like some advice. Anyone?
Thanks,
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David
NACRA 5.0
Mast Rake
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Posted: Aug 30, 2010 - 01:56 PM
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Posted: Aug 30, 2010 - 02:51 PM
Not sure on the mast rake for healing but with a boardless boat it could add more weather helm (tiller tugs) My 5.5sl buries the leeward hull too but it tends to pop back up and never feels like it was going to pitchpole. You can add more downhaul to flatten the sail and get less healing motion.
edited by: fa1321, Aug 30, 2010 - 01:53 PM -
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Posted: Aug 30, 2010 - 04:54 PM
This may not be exactly related to your issue, but this article can help explain the forces involved and the affect of raking the mast.
http://thebeachcats.com/Article15.html
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Damon Linkous
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Posted: Aug 30, 2010 - 05:37 PM
Damon - great article, thanks. I'll have to read it more than a couple of times in order to work through it.
I have a weather helm, which is good, and have not had this much of an issue in lighter winds.
Does anyone here adjust mast rake significantly for stronger winds? I have my boat at a dry storage right next to the lake so leave the mast up all the time and therefore don't adjust everytime.
I don't think it would pitchpole as she kept bouncing up to the surface, but it was on my mind. I am sure the powerboat chop did not help.
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Posted: Aug 30, 2010 - 06:54 PM
As the bow goes under you need to go farther aft on the boat.
I have been on the wire with my feet at the rear cross beam, crew right next to me.
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Posted: Aug 30, 2010 - 07:35 PM
Now I am confused, how do i rake my mast back? I thought it would be no more than a shroud adjustment.
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Nacra 5.2
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Posted: Aug 31, 2010 - 12:08 AM
David, I do as SKARR says, when the bow starts to go completely underwater, I ask (all my crew have never been on a cat before)my crew to move back. Shifting only a foot or so will bring the bow up. When I solo my 5.7 I experiment with positions varying from the fron tbeam, ( I can barely reach the tiller when fully extended) right back to feet straddling the rear beam. I have buried both bows right to the front beam, & the 5.7 didn't feel like it wanted to P pole, though the speed scrubbed way off.
GolfDad, to rake the mast you have to move the pin on the front stay upwards. I have a 10 hole adjuster, & have worked from the fourth hole (counting from the bottom, nearest the bridl wires) all the way upwards to the top hole. Everytime you move the pin upwards, the mast will tilt towards the stern. This will then slacken the shrouds, which willhave to be tightened.
I use the method someone on this forum gave me. I set the forestay where I want it, & the starboard shroud. Then I hang on the harness or get crew to, & set the port shroud to match the other. My cat sits mast up on a seadoo lift. IF I'm not sailing it for a few days I slacken the port shroud, that takes the tension out of the entire rig. I leave the chainplate cover up at the top of the shroud to remind me that I need to snug the port shroud down before sailing. With harness on, I can hook onto the top hole of the dogbone, partially hike out, & move the shroud pin down to match the starboard. You can also raise the main & have it load the mast, but I don't like doing that on the lift, as it has the potential to tip the cat off the lift, & my dock is not always aligned with the wind to load the mast in the correct direction.
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Posted: Aug 31, 2010 - 08:38 AM
Good input guys, thanks. Knew I was going to get some good advice on this forum
I will work on shifting my position around to see the impact - along with all the other things I need to be thinking about that are not second nature yet.
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Posted: Sep 01, 2010 - 04:26 PM
Conventional wisdom as learned from the dealer from whom I buy parts and seems to know his business is that there is no rake on a Nacra mast.
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Posted: Sep 01, 2010 - 05:31 PM
I agree Larry, I have been sailing Nacra's for the last 15-18 years, and I always carry my mast straight up. Ist 10 years on a Nacra 5.8 and the last 8 on a Nacra 6.0. Lots of positive bouyancy forward on these boats. If I need to depower I use all the other methods that I have available. 4 way jib lead, 16/1 main down haul, main sail clew traveler, main sail traveler, moving crew weight etc. -
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Posted: Sep 01, 2010 - 10:10 PM
Well for what its worth my dealer at Key sailing who has won some Worrel1 1000 legs says to rake just aft of the port. Of course I have no idea why or how but it is good conversation.
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Nacra 5.2
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Posted: Sep 01, 2010 - 10:23 PM
My mast is set so that when close reaching there is a little weather helm. This is with both boards down. I read the above article and other like articles. If I was to rake back more I would have so much weather helm my arms would start to look like Popeye's. -
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Posted: Sep 01, 2010 - 11:48 PM
Maybe I am raked too far aft cause weather helm is killing me upwind.
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Posted: Sep 06, 2010 - 02:59 PM
There are quite a few variables that contribute to weather helm, mast rake being only one of them. If I sail my 5.7 with several people on board, weather helm increases noticeably if they are towards the rear.
Adjusting those little white plastic screws in the rudder castings of the Nacra make a big difference. They only give a total range of about 1/2", but that 1/2" makes a very big difference.
Golfdad, make sure your rudders are being pulled down til they hit the castings, & that they stay there. I'm using 1/4" Sta Set & it works fine. I pull the line tight with one hand, then push the line into the V grooves with the other, preventing even a fraction of slippage as the cleat grabs.
When reading Berman & Whites books on setting up & racing cats I believe it says that raking is not merely to prevent pitchpoling, but that it also gives more power, & better pointing, at the expense of more weather helm.(correct me if I'm wrong on that last point, the books are at the cottage, I'm home moving kids back to University this weekend).
Bermans book also states that originally Nacras were sailed with near vertical masts, but the norm now was to rake them. I'll have to re read that section as I cannot quote the paragraph.
I think MUMMP has his set up with 2-10 hole chainplates, though the stay length would have to be accounted for.
I have not let the halyard hang, & measured how far mine is raked, but i am at the top hole of a 10 hole adjuster, using standard length stay, & weather helm is there, but not unmanageable for a couple of hours. I have more weather helm on a starboard tack than port, still trying to determine the cause of that.
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Posted: Sep 06, 2010 - 04:05 PM
I've been experimenting a lot with my 5.2 this year. I've found that raking the mast back so the top of the mast is just behind the forward ports is just about perfect for a blend of power, stability and keeping the bows up a bit. They still bury a bit but are meant to. I also keep my rig a little looser than I though was appropriate. Not enough that the mast is floppin around but loose enough that the mast rotates very freely. Finally I rigged a 2:1 downhaul on the rudders so I can make sure they are completely down. I have no adjustment on my rudders but as long as they are tight I am getting almost no weather helm at all.
All these settings together give me an extremely light helm and really good control. Took me awhile to get things set just right though, the key appears to be small adjustments until you dial it in. Small changes make big differences on the helm!
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Dave Bonin
1981 Nacra 5.2 "Lucile"
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Winnipeg, Manitoba, Canada
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Posted: Sep 06, 2010 - 05:58 PM
However, it's the most commonly adjustable variable.
Also, I think it's crazy that you or anyone use something larger than 3/16" for rudder lines.
Dave: I am shocked that have have neutral helm with that square top and a raked mast.
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Rob
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Posted: Sep 06, 2010 - 06:25 PM
Rob, I know what you mean, I have no idea why it works like that for my boat. Between yourself, EC and a few others I think I've come to the conclusion that each boat has it's own personality. None seem to be set the same.
I tried at least a dozen different settings and a little bit of rake seems to work the best. Last year I had a heck of a time with weather helm but I'm not sure exactly where my mast was set (too many other things being learned and adjusted). I have a feeling given the changes I have made that I had the mast tip near the rear beam. After reading Rick White's book, I think it could also be that I now have the rudders tucked under quite a ways also.
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Dave Bonin
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Winnipeg, Manitoba, Canada
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Posted: Sep 06, 2010 - 06:59 PM
It's not scientific or anything, but my guess would be that when double trapped on mine with the square top, and mast raked maybe one or two holes aft of center, I have about 45lbs load from the tiller and 35lbs load on the mainsheet (mine doesn't cleat from the trap) on a reach.
No matter, she's done for the year =(.
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Posted: Sep 06, 2010 - 11:05 PM
I used 1/4" because I bought a bunch of it for other purposes. What would be a disadvantage of using 1/4" over 3/16"? I can't see 1/16 making any difference, there is plenty of room for the 1/4" to run through/over the rollers & it cleats fine in the pivmatics.
I know what you mean about not being able to cleat from the wire, it is hard to hold the line in a blow & pull upwards enough. You can make it easy to cleat by changing the angle settings on the upper Harken block, but that will also change the way it UNCLEATS. I may change mine a bit next season, but for now I want it to UNCLEAT with a pull from any direction.
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Posted: Sep 06, 2010 - 11:19 PM
I've adjusted the cleat angle several times, and decided I like it best when it's never got a chance to 'accidentally' cleat.
3/16" cleats and holds far easier in the size of cleat in question.
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