mast rake problem

Moderator: GreenLake

mast rake problem

Postby jdoorly » Tue Aug 02, 2011 9:24 pm

I am trying to get the proper mast rake in order to steer correctly. But, I'm getting goofy results from my efforts to try different mast rake angles, sail on a beat, and evaluate the helm.

I started with the mast at 3.5 degrees and had bad lee helm in light air. Moved the rake to 5.5 degrees and had very bad lee helm in light air. Then I moved the rake to 8.5 degrees and had very bad lee helm, until the wind increased from under 5kn to 12-15kn and I had a reasonable amount (a hair too much) of weather helm. The wind continued to fluctuate from light to 15kn and the steering continued to fluctuate from lee to weather helm. I tried raising the cb 25% but didn't notice any variance in steering.

I don't remember any keel boats acting like this, is it a centerboarder thing?
DS2 #6408 "Desperado"
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Postby Alan » Tue Aug 02, 2011 9:36 pm

Was this with the UPS? I've been wondering whether the forward placement would cause lee helm.
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Postby jdoorly » Tue Aug 02, 2011 10:15 pm

These results given were the standard Intensity main and jib. However, the UPS, and I use it quite close to the wind in light air as well as reaching, had the same lee helm in light air and weather helm in gusts.
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Postby algonquin » Tue Aug 02, 2011 11:59 pm

This is a tuff situation to analyze by just adjusting your mast rake angle. To many other factors are at play here. Especially sail position and adjustment with your prevailing wind direction which is rarely consistent. Water surface condition is also at play. I believe sail trim has a larger impact on lee and weather helm than mast angle. It will be difficult to summarize your data. Another factor on your mast angle observations could be the height of your mast hinge. Good luck with your journey. Brad.
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Postby swiftsail » Wed Aug 03, 2011 1:44 pm

Hey,
Another huge factor is the heal of the boat. As soon a the boat heals you will get weather helm and, should, if the mast rake is correct. The proper rake is with the boat flat in about 10-12 knots you should have just a bit of weather helm close hauled. A common mistake is when close hauled, not sheeting in the main enough. The boom should be centerlined and sheet/vanged enough to bring the top baton in parallel with the boom.

The DS when sailed flat and with proper rake is a very balanced boat and very easy to sail.

Steve
DS 307 "Security Risk"
DS 14024 "Flight Risk"
Live Slow, Sail Fast
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Postby GreenLake » Wed Aug 03, 2011 2:31 pm

swiftsail wrote:The DS when sailed flat and with proper rake is a very balanced boat

I found that so, with both the old, used sails I had before and with the replacements.
~ green ~ lake ~ ~
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Mast angle and tuning

Postby Wyatt » Thu Aug 04, 2011 1:43 am

Try using this guide:

http://www.northsailsod.com/class/daysa ... uning.html.

In my experience you shouldn't have to fiddle with the mast location too much. It's the shroud/stay tensions that seem to matter most.

Good luck.
DS1 2922
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Postby swiftsail » Thu Aug 04, 2011 2:24 am

Actually that is an old link. This is the new one. It is a good place to start.
http://www.onedesign.com/class/daysaile ... uning.html

Steve
DS 307 "Security Risk"
DS 14024 "Flight Risk"
Live Slow, Sail Fast
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Postby Mike Gillum » Thu Aug 04, 2011 3:29 pm

Steve Lowry #307 is correct that you want to use the North Sail Daysailer Tuning Guide to set-up your mast and rig as it's a proven Tuning Guide used by most of the past Daysailer North American Championship winners in the last decade.
Measuring by angles is terribly inaccurate as it depends on too many factors that can't be replicated on a regular basis.
Steve is also correct that a flat Daysailer or one heeled slightly to weather will provide the least amount of helm.
Correct fore/aft weight placement of skipper and crew will also greatly affect the amount of helm you feel.
Generally you want the skipper and crew as far forward as the Cuddy Cabin will allow. The skipper and crew only start moving back in the boat as the wind and/or waves increase.
I have found the Daysailer helm to be relatively neutral relative to most of the other one design classes I've raced over the years.
You want just a little bit of weather helm upwind to encourage your Daysailer to easily point into the wind.
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Postby jdoorly » Thu Aug 04, 2011 6:45 pm

Thank you all for sage comments and the tuning link.

My mast is 5.5" shorter than the allowed 20' 6", I'm not sure how the 11' 1/2" mast base to transom distance translates to a DS2, and I don't have a clue what a magic box is... but I'm beginning to appreciate the complexity of these dynamic and multi-force equalibria.
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Postby Mike Gillum » Fri Aug 05, 2011 9:14 am

I would start by getting the Mast plumb in the boat by attaching a Plumb-Bob weight to the schackle on your Main Halyard, launch your boat, and with your boat loosely tied to the dock in calm water end-up with the weighted Main Halyard hanging just aft of the base of the Mast at the top of the Cuddy Cabin.
Once the Mast is plumb then you can start playing with incremental fore or aft adjustments of the rake over time to help balance the helm if you're still experiencing problems.
I would still work on sailing your boat flat while experimenting with fore/aft skipper and crew placement.
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Postby jdoorly » Fri Aug 05, 2011 12:40 pm

Thanks Mike, will do...
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Postby jdoorly » Fri Aug 26, 2011 10:36 pm

I got the mast as close to plumb as I could, had to add several shackles to the shrouds to lengthen them. I found the boat didn't like having the jib up at all! Though it seemed to balance well under mainsail alone.

As I understand it, to reduce lee helm I need to move the CLR (center of lateral resistance- Skenes (actually Kinney) says cut out the underwater profile and balance it on a pin to find the CLR). or, move the CE (center of effort) of the sails aft.

So, I raked the mast aft to about 6 degrees. That is I laser leveled on my water line and cranked the trailer jack until they agreed. I double checked with a precision level on the cockpit floor, then I measured the mast rake with a level/angle finder [with the safety pin in the tabernackle so the mast is straight]. I also added another block to the outhaul to better control the outhaul but I still can't get 10ft of foot But the lee helm remained unless the wind gusted to above 10 then the boat healed and I had weather helm until the wind dropped.

When I added the bow sprit for the UPS I continued to use the same holes in the deck for the stem fitting but the sprit height and Harken furler moved the jib up 5". That should increase heeling moment but not change the CE. So, I drilled new holes in my bow sprit to be able to move the jib tack either 9 or 18 inches aft.

I was sailing today in 5-10 with the tack 9" back and was able to let go of the tiller and steer with the mainsheet, however the main was luffing a bit. I then pulled in the main and needed to pull the helm to weather (actually to centerline) to hold coarse. Yea!

I anchored and moved the jib tack to the 18" mark but the wind died and I wasn't able to evaluate it. I would guess increased weather helm.

As soon a Irene goes by I'll see how the boat balances under a reef
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Postby Jeepman252 » Sat Aug 27, 2011 3:20 pm

I've tried to search, and being new to sailing, what is UPS?

The only one I know of is the one in my car that tries to give me accurate directions... :oops:
Larry
'83 DSII
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Postby TIM WEBB » Sat Aug 27, 2011 4:29 pm

Utility Power Sail, made by Doyle.

http://www.doylesails.com/cruising/ups/index.html

It's also the thing that keeps your PC running when the power goes out (Uninterruptable Power Supply).

The thing in your car is a *GPS* ... :P
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