Hi Everyone,
I am getting some new parts for my 5.2, one of which is a rudder alignment end cap. On the same line of thought I was having some issues with weather helm last year. I know there are various adjustments for this but one question I had is how the heck to you adjust rudder rake on a Nacra 5.2 (or 5.0, 5.5, etc for that matter)? My first thought is the only way you can do it is to shim under the gudgeons. I have also heard of redrilling the castings, something I am not in a hurry to do. Am I missing something? Is this an something i should just leave alone?
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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Nacra Rudder Rake
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Posted: Jan 06, 2010 - 11:28 PM
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Posted: Jan 07, 2010 - 12:06 AM
First, if you are using the Pivmatic cleats, if they are the ones with the plastic clam cleat, replace them with the aluminum clam cleats, and use a knobby line that has zero stretch. I found that at speed the line would slip thus increasing the weather helm. Make sure you are getting the rudder all the way down.
Moving weight forward also reduces helm, drive the bow.
Now to your question, when all else fails remove some material from the rudder where it meets the bottom of the casting so that the rudder can go further under the boat. Don?t do too much or you may end up with lee helm and then need the set screw to keep the rudder further aft.
How bad is your helm?
edited by: nacra55, Jan 06, 2010 - 11:09 PM
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Ron
Nacra F18
Reservoir Sailing Assn.
Brandon, Mississippi
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Posted: Jan 07, 2010 - 09:31 AM
i would certainly try everything i could before i touch the castings.
I know little about nacras but what about adjusting your mast rake? this can help or hurt tremendously with helm issues.
have you tried lifting your windward rudder? if yes does that effect it? (if it does it could also be a tow (toe?) issue. do you have weather helm on both rudders?
can you drill the rudder (fill the old hole.. drill a new) to adjust its alignment (vs. drilling a casting)?
good luck, take pics... keep us posted -
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Posted: Jan 07, 2010 - 09:49 AM
Hey Dave,
Ron and I definitely know these platforms and are very familiar with this. He is spot on.
Once you start raking the mast back, you adjust helm by removing material.
http://www.thebeachcats.c…434&g2_imageViewsIndex=1
I use a belt sander, works good and it very easy. Measure the rudder rake while on the trailer with the blades locked down. Scribe a pencil line with a straight edge. Remove a little at a time. The picture shows a moderate adjustment. On my latest platform (modern cut main, very agressive rake) I had to make a more aggressive cut that got into the core. If you need to go that route, cut beyond where you want to go, build it back up with epoxy filler, and then belt sand back down where you want it. The reason to do this is to seal up the rudder case. You don't want a penetration in the core. Water will eventually kill it.
This system of adjustment is easy. Do not modify the castings, and drilling the pivot holes in the blade is a total crap shoot, which gives you no room for adjustment.
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Philip
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Posted: Jan 07, 2010 - 10:28 AM
I had the problem with getting the rudder down and solved it by installing new pivmatics and rigging a 2:1 pull on the rudders.
I think I had almost no mast rake this year but am getting a new flat top sail, so I might try to rake it back a bit more.
What I don't know is how much toe in/out I may have had in the rudders. Now that I will have an adjuster I will pay more attention to it. THat is the most likely culprit at this point.
I also haven't played with setting the dagger boards much, I will look at that before I start removing material.
Darn, I was hoping that I was missing something and there was a built-in (i.e. reversable) adjustment for rudder rake. Sigh, belt sander it is, if it comes to that.
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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Posted: Jan 07, 2010 - 11:30 AM
oh wait,... did you try to adjust the auto-weather helm button first? Its right next to the engine compartment -
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Posted: Jan 07, 2010 - 12:18 PM
Go back and read Ron's post. You can adjust after the fact with the screws. That's why this is the preferred way to do it.
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Philip
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Posted: Jan 07, 2010 - 12:19 PM
Damn, missed that one. Might be under the ice cream machine too. :)
I was reading about F18s that have a set screw for adjusting the rudder rake and was hoping... Sigh, just makes we want an F18 more.
D.
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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Posted: Jan 07, 2010 - 12:58 PM
Wait.. nacra's have an icream machine? damn... i want one now! :) -
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Posted: Jan 07, 2010 - 03:04 PM
It's an aftermarket, one of the innovations on the new 20. They took the idea from the US's Nuclear Submarine fleet. :)
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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Posted: Jan 07, 2010 - 03:19 PM
Come on... I've been on our subs...no ice cream there either...
(something to do with excessive gas's building up pressure inside the subs)....
However.. i was on a Norwegian Mine Layer and it had a bar (an innovation i later brought to my ship). :)
Oh yea.. i was also on a Canadian destroyer.. they also had a bar.. We (USN) drank every drop of beer on the boat... and then took the crew to our enlisted club to drink Sour Mash (Jack Daniels)... we then all got in fist fights! good times... -
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Posted: Jan 07, 2010 - 07:46 PM
Hmm, Tom Clancy was wrong then... or maybe it was the Nimitz Class Carriers that have the ice cream machine - the submarines may have had slurpees.
Those Norwegians sure know how to party! Nothing else to do in Norway, except cross country ski and pillage coastal towns in the UK. :)
Hmm, must you must have been on an Iroquois! Biggest ships we have right now. They are reasonably modern, fast and have a crazy helicopter landing system! We finally got some decent submarines a couple of years ago, hopefully a new heavy cruiser soon.
What is it with Jack Daniels and fist fights? I can drink Rye all I want and be happy, 2 shots of Jack and I want to punch someone!
D.
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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Posted: Jan 07, 2010 - 09:35 PM
haha .. this was 20 years ago that i was in norge and 22 when i we drank the canadian ship dry...
yea. i dont drink whiskey or tequila anymore ... i end up in mexico.. married.. in jail... etc
like a true sailor.. i only drink rum (and actually am back on the wagon) -
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Posted: Jan 07, 2010 - 11:46 PM
my 5.2 rudder casings have a hole for a rudder rake adjuster screw, but it looks like they've never been used...
so the rudders are as far forward as possible, which seems to give just the right amount of helm feel with the tiny amount of mast rake i use
sounds like the problem is elsewhere... -
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Posted: Jan 08, 2010 - 01:31 AM
Aye, probably still an Iroquois though. These days I prefer a good Scotch to anything else. I did drink a Tawny Port that was older than me (37) the other day. Damn nice drink but it should be for $50 a shot!
Likely, the problem lies in my mast rake, but it was a question I wanted answered. Obviously it wasn't a common problem with the stock setup so they didn't need an adjuster. I will have to look at my mast rake more closely, it may have been farther back than I thought. The idea of adding a set screw to the rudders is a good idea, I will consider it when I get to that.
Thanks guys!
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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Posted: Jan 08, 2010 - 10:50 AM
Dave,
Don't look at it as a problem, because it is not. It's all about tuning the boat and getting it balanced, (i.e. CE & CLR), and then it gets fast. The "problem" is nowhere else. Rake the rudders forward or reduce mast rake.
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Philip
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Posted: Jan 08, 2010 - 12:07 PM
You won?t see this anywhere and it goes against anything you will read, but if you have too much forward rake in your mast, it will increase the weather helm.
I had a similar problem on my 5.5 SL and kept raking the mast forward. It just kept getting worse. I asked a fellow sailor what my problem was and he said to rake it back. It worked.
Don?t worry about the set screws or reshaping the rudder. Measure your rudder toe in and adjust it so that it is almost neutral, within a 1/16 of an inch. Make sure that the rudders are going all the way down and are not slipping in the clam cleats; this could be the most likely cause. Keep your crew weight forward, don?t sit on the stern. The skipper should be at the dagger board well and the crew at the main beam. Then experiment with mast rake and find the sweet spot. While experimenting with the rake try and keep wind and crew weight a constant. As the wind and weight increase so will helm.
As Phillip said, It?s all about tuning.
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Ron
Nacra F18
Reservoir Sailing Assn.
Brandon, Mississippi
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Posted: Jan 08, 2010 - 12:20 PM
I'm definitely planning on playing with the mast rake.
That is also a good point about crew weight distribution. I'm still not used to the way the Nacra can handle crew weight forward and dive the leeward hull so far under. I tend to keep the crew weight back too far I think. My old hobie 16 instincts still tell me to hang off the back of the boat or your going to pitch pole. :)
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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Posted: Jan 09, 2010 - 11:18 PM
WOLFMAN
Here is a picture of one of my rudder castings. You can see the adjustment screw at the top right. I could back it out, & gain almost 1/4" greater rake,(lee helm) or turn it in to add weather helm. Looking at the picture, it would be very easy to shave a few mm from an appropriate spot to gain more lee helm. You are an engineer, a cursory study of the geometry of the rudder down line will quickly show how a slipping/stretchy pull down line will result in some weather helm.
I am certainly no expert, but after a week in Cuba reading my newly gained copy of Catamaran Racing, I think I understand exactly what Philip & Ron were talking about. I certainly would never drill the casting/rudder, to paraphrase MUMMP, you could really ph@#$K it up, with no way to backtrack.
I learned quite a bit from this thread. I brought my rudder assembly home, & studied it with regards to Phil Bermans books + the info in this thread. I think Mr Berman is a very accomplished Cat sailor, but his books are almost exclusively Hobie. MOST of the physics are the same, but I think other Cats different setups/hulls/rigging mean some of his ideas may not translate exactly to a NACRA.
edited by: Edchris177, Jan 09, 2010 - 10:38 PM
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Posted: Jan 09, 2010 - 11:34 PM
3 questions for Ron & Philip...or anyone with knowledge. What is the hole in top left of the rudder casting for? It is only on one casting, the other does not have this hole.
Also, MUUMP, with regards to your post above, could you enlighten a Noob as to what CE & CLR regard to... center of effort? can't think of CLR other than a rust cleaner
How much free play is OK between rudder & casting? Right now I can slip 2 credit cards between casting & rudder, there is a bit of play if I wiggle the rudders sideways. Should I attempt to build the rudders up, wrap waterproof tape around the casting where they rub? What do you cosinder excessive? I have read about shims/washers, wouldn't it be better to build up the are where the free play is (the worn white line in the casting cutout in picture above). That would provide much better support for the rudder as opposed to a shim/washer on the bolt.
Picture 2 shows the Pivmatics that I have. The rudder down line that came with the boat is shown. That is as far "into" the Pivmatic as I can get it. It doesn't seem like it goes down far enough into the teeth of the jam cleat. Are these cleats worn & should be replaced, or is this line diameter to large? Can anyone sow me a picture of what a line fully engaged in the cleat looks like? Pulling this line tight (assembly is not mounted on the boat, I can't do the same job with it on the floor as I could on the boat)then pulling on the rudder to simulate water force, seems to show the line slipping/stretching...with resulting displacement of rudder towards the up position, which would result in weather helm.
RON, what line would you recommend, diameter & type, (no stretch nobby) They are pretty short lines, cost wouldn't be much.
I also realize the connection between the rudder tubes & the cross tie is not as shown in the assembly manual, a few parts from Murrays, or D Berger will cure that.
Wolfman, this is what my adjustable cross tie looks like, looks pretty simple to adjust & get rid of any rudder misalignment. Damn, I wish I had the boat at my home garage, I'm itching to tweak.
Wolf. here is a shot of the pivmatic & adjustable tiller
Is this enough "bite" or is the jam cleat worn, or line to lasrge?
edited by: Edchris177, Jan 09, 2010 - 10:51 PM
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