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

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

atl76

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.

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
1992 Hobie 18
Memphis, TN

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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.

David

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.

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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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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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
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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.

David

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.

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.

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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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.

Maybe I am raked too far aft cause weather helm is killing me upwind.

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Nacra 5.2
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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.

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--

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!

--
Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Edchris177

There are quite a few variables that contribute to weather helm, mast rake being only one of them.

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
OKC
Pile of Nacra parts..
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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
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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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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Rob
OKC
Pile of Nacra parts..
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Quote

Also, I think it's crazy that you or anyone use something larger than 3/16" for rudder lines.

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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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--

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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Rob
OKC
Pile of Nacra parts..
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I have to disagree that 3/16" cleats or holds "far easier". You pull the line with a bit of downwards force & it cleats, & holds, mine has never let go. What is easier than that?
I don't think one would have to be "crazy" to use 1/4"
In fact a case could be made for using line that doesn't sink deeply into the pivmatics. The 1/4" line has less tendency to recleat itself after you yank it out in a panic as you realize the water is getting shallow fast. Also the deeper the line sinks, the tension on it becomes almost completely horizontal. If you sank a very thin line right down to the bottom of the cleat, it wants to shear the rivet, instead of popping the pivmatic. The higher in the cleat you are, the longer the arm trying to pivot the pivmatic, & the less force it takes to pop the rudders when striking an object.
My lake has dropped around 1' & my rudders now tend to hit the sand as I round up to the dock. I like them letting go easily as there are some logs buried in the mud/sand.
If I wear the teeth near the top, maybe I'll change to thinner line so as to extend the cleats life,(mine are the plastic ones)but for now 1/4" is golden.

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--

hah, fair enough...'crazy' might be a bit strong, but I'll agree to disagree on the rest.

1/4" would be easier on the hands trying to lock the rudders down initially, but doesn't seem like the right call overall to me.

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Rob
OKC
Pile of Nacra parts..
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golfdad75

Maybe I am raked too far aft cause weather helm is killing me upwind.

I have the same problem on my Prindle 18. I have to keep constant pressure on the helm to maintain course and if I need to adjust something and need to hands I try to tuck it under my rump and leg a bit to hold it otherwise I start to turn upwind. In heavier winds it can turn quite quickly. I understand why having some could be good if you fall off the boat or something or lose the tiller but it sure can put a strain on my grip and forearm after a bit.

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Dustin Finlinson • Magna, UT
Member: Utah Sailing Association
1982 Prindle 18
1986 Hobie 17
1982 Prindle 16
1980 Prindle 16(mostly)
1976 Prindle 16(mostly)
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Quarath

golfdad75

Maybe I am raked too far aft cause weather helm is killing me upwind.

I have the same problem on my Prindle 18. I have to keep constant pressure on the helm to maintain course and if I need to adjust something and need to hands I try to tuck it under my rump and leg a bit to hold it otherwise I start to turn upwind. In heavier winds it can turn quite quickly. I understand why having some could be good if you fall off the boat or something or lose the tiller but it sure can put a strain on my grip and forearm after a bit.

Something is wrong. you should not have so much helm that you are having it tug out of your hands. either your rake is extreme, or your blades aren't angled in correct, or your hulls are out of alignment, or your jib is wrong (height, angle, its upside-down?), or your hulls are on backwards, something is out of whack if you have extreme lea or weather helm and can't fix it (or you own a aqua-cat)

most people want a small amount of weather helm to round your cat up in the event you fall off... drop the stick, break your extension cross-bar, etc. the amount of helm (when set close to neutral) will fluctuate with things like speed, up vs. downwind, travel etc...

i personally have almost neutral helm and prefer that due to when i am dousing my spinnaker, the last thing i want is to round up while i am snuffing (as i would then have my spin tangled in all my stays)


Disclaimer: never owned a prindle/nacra

my p-16 had some big time weather helm last season. after adjusting the rudders to the manual specs, only a small amount of pull was left. this season, i raked my mast way back(next to last hole) with almost no affect on the rudders. the boat got faster with every increase of mast rake but surprisingly did not affect the rudders. i could probably rake my rudders a little more foreward but i don't want to jinx it.

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bill harris
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prindle 16- "BLUE RIBBON"
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