reef points

Moderator: GreenLake

reef points

Postby icdoubl » Wed Dec 29, 2010 2:15 pm

I would like to add reef points to my main. Does anyone know where they should be placed and how to attach them?

Thanks.

Dan
icdoubl
 
Posts: 7
Joined: Thu Apr 17, 2008 3:54 pm

Postby jeadstx » Wed Dec 29, 2010 4:24 pm

When I had my reef points (2 sets) put on my main, I just left it up to the sailmaker I took the sail to.

John
1976 Day Sailer II, #8075 - Completed the 2011, 2012, and 2013 Texas 200
1952 Beetle Boat Swan Catboat
Early Rhodes 19
1973 Mariner 2+2, #2607 - Completed 2014, 2015 and 2016 Texas 200
1969 Day Sailer I, #3229
Fleet 135; Canyon Lake, Texas
jeadstx
 
Posts: 1216
Joined: Tue Jul 08, 2008 11:10 am
Location: Dripping Springs, Tx

Postby jdoorly » Thu Dec 30, 2010 7:34 pm

Hi Dan,
I got a new Intensity mainsail this year and the single reef points that it came with were: On luff top of boom to forward reef cringle = 28 inches, and on leach top of boom to aft reef cringle (i.e. line pirpendicular to boom) = 34 inches. I felt that these points did not remove enough sail area when reefed; reef 1 reduced mainsail area by 21% and I would have prefered 24%.

I added a second set of reef points to the mainsail and placed them at 36 inches above forward first reef point, and 40 inches above the aft first reef point, for a an additional 23%, or a total sail reduction of 44%. http://forum.daysailer.org/forum/viewtopic.php?t=3528

This was a winter project and I have not gained experience with the second reef.
DS2 #6408 "Desperado"
jdoorly
 
Posts: 379
Joined: Mon May 17, 2010 2:24 pm
Location: CT

Postby GreenLake » Fri Dec 31, 2010 2:51 am

jdoorly wrote:I felt that these points did not remove enough sail area when reefed.


John, you may have stated that somewhere, but could you, again and for the record, tell us in what conditions you felt you had reached the useful limits for your first reef?

What was the wind like? Were you single handing? What was your crew weight and experience?

So much for experience (data). Now some more theoretical observations:

When it comes to 21% vs 24% area, I firmly believe that difference is in the noise. The difference is 3% of the full area and 4% or so of the remaining area — I suspect that this is close to the limit where you couldn't tell the difference in a "blind" test, other than perhaps while racing against a matched boat.

Also, by lowering your sail's center of effort by 2 1/3 ft, as well as reducing area, your heeling moment (from the main) should be reduced to less than 2/3 of the unreefed value.

If the way I am calculating this is in fact correct, your second reef should have you down to 20-30% of heeling moment - and by that time, the geometry is changing such that I'm not even sure whether the loss of the main behind it, doesn't affect the jib to such a degree that the effect for the combined rig isn't more than proportional.

Assuming the shape of the reefed sail is good, the reduction in driving force should more closely track the sail area — yes, the winds higher up should be stronger, but in strong winds, the air flow over the water is no longer laminar, and the windspeed is more constant across the sail.
~ green ~ lake ~ ~
GreenLake
 
Posts: 5182
Joined: Mon Jun 18, 2007 3:54 am

Postby jdoorly » Tue Jan 04, 2011 1:31 am

Hi GreenLake,

John, you may have stated that somewhere, but could you, again and for the record, tell us in what conditions you felt you had reached the useful limits for your first reef? What was the wind like? Were you single handing? What was your crew weight and experience?

Sure, but let me start with getting my name straight: Only the IRS and my gall bladder surgeon call me John, it's Jay or j or jdoorly. Back in Sept I started a thread about reef points location...
http://forum.daysailer.org/forum/viewtopi ... highlight=

Experience: before may 2010 I had not sailed since 1980 but almost won (DQ'd) the All Navy Regatta at that time in Mobjacks. After buying a DS2 this year had some family novice guests , but only one or none at a time (I'm 170lbs they are 170 lbs). I made few demands on them and I steered and held the mansheet ready to uncleat. Several times I was late in letting go the sheet, and several times the cleat would not let go due to wind pressure, and several people got dunked as the rail went under momentarily. Problem wind strength was gusts above 15 mph when on a beat, sometimes with and sometimes without a jib up.

After I installed the auto pilot I still wasn't 'free' having to remain vigiant on the mainsheet. The old main didn't have any reefs. After I got the Intensity main with 1 reef things eased up a bit especially with cracked sheets. But I still felt the need for a second reef to keep the auto pilot happy (he doesn't like to heel and absolutely cannot deal with weather helm) and to let me relax my grip on the mainsheet!

Since 21% is in the normal range for a first reef (although I would call it a 'racing' as opposed to a 'cruising' reef), after some thought on the subject I believe that my perception of the location of the reef points may be skewed because my DS2 is the lowest aspect ratio mainsail I've ever set.



So much for experience (data). Now some more theoretical observations:

When it comes to 21% vs 24% area, I firmly believe that difference is in the noise. The difference is 3% of the full area and 4% or so of the remaining area — I suspect that this is close to the limit where you couldn't tell the difference in a "blind" test, other than perhaps while racing against a matched boat.

Also, by lowering your sail's center of effort by 2 1/3 ft, as well as reducing area, your heeling moment (from the main) should be reduced to less than 2/3 of the unreefed value.

If the way I am calculating this is in fact correct, your second reef should have you down to 20-30% of heeling moment - and by that time, the geometry is changing such that I'm not even sure whether the loss of the main behind it, doesn't affect the jib to such a degree that the effect for the combined rig isn't more than proportional.

Assuming the shape of the reefed sail is good, the reduction in driving force should more closely track the sail area — yes, the winds higher up should be stronger, but in strong winds, the air flow over the water is no longer laminar, and the windspeed is more constant across the sail.


I suspect your right about noise, heeling moment, and driving force. I don't know. I didn't approach the question of reefing positions that way, math is my method of last resort. I pondered what works? What do other people do?
Searching the internet I found 4 sets of data (I was planning on taking off dimensions from drawings but didn't feel the need after finding these numbers). They were (in percentage of reduction):

REEF1...REEF2....REEF3
20-25....40-50....60-75
25-30....45-50....60-65
25.........50.........75
20.........40.........--
AVE:
23.7......45.6......68.3

The fourth item is http://www.cruisingworld.com/how-to/sys ... ll-seasons
The cruisingworld article also says that a storm trysail is about equal to a 3rd reef at 70% reduction but probably performs better.

My first reef is 21%, and I added another 24% with the second reef for a total of 45% reduction. At this moment my old jib is spread out on the floor waiting for me to shear off the bottom 3 feet and convert it into a storm jib to balance a double reefed main. The old jib is waiting because I'm trying to figure out what is going to happen to the fairlead when I chop more than half of the sail away!!!
DS2 #6408 "Desperado"
jdoorly
 
Posts: 379
Joined: Mon May 17, 2010 2:24 pm
Location: CT

Postby GreenLake » Tue Jan 04, 2011 2:24 pm

J,

On larger keelboats, the storm jib would be set higher than the regular jib, I believe the reason is so that it doesn't catch water as easily in higher waves. If that is done, then the fairlead positions don't have to change as much. (That in itself may be the other reason why storm jibs are cut as they are).

I'm heavier than you are, and at times, have an even heavier crew. One of those times, with a novice crew, we hit gusts of 20kn (true wind, per local weather station) and managed them quite nicely without leaving our seats 8)

Needless to say, I did play the mainsheet a lot. With an experienced crew, we could have turned more of that power into forward motion. I sometimes put a reef in when singlehanding, just to make things less stressful, but so far, I haven't really been in a situation where I can positively say I needed one.

If you are having trouble releasing the mainsheet, perhaps you might follow K.C.'s suggestion and use a ratchet block, possibly with additional purchase. That might allow you to run the mainsheet without cleating it.

K.C.'s other suggestion, to use vang sheeting to keep the sail flat in strong winds, is on my list of things to try next (soon as I can get a vang fitted).
~ green ~ lake ~ ~
GreenLake
 
Posts: 5182
Joined: Mon Jun 18, 2007 3:54 am

Postby jdoorly » Wed Jan 05, 2011 8:46 pm

On storm trysails and jibs they don't use the regular sail fairleads, the clew is tied to a sturdy padeye on deck (not the boom) and the same for the jib. But I don't consider my mainsail second reef or my jib recut project to be storm sails, they are just the next detent down on the comfort potentiometer.

I considered a ratchet block, but that solution just lets you deal more smoothly with the problem, I want to reduce the problem, be able to manage the mainsheet, not be a slave to it. To me that means the goal is to allow the mainsheet to remain cleated for enough time to get something else accomplished, like getting a drink out of the cooler, or updating a DR plot on the chart.

When I got the boat it had a standard 3::1 mainsheet purchase on the stern leading to a camcleat on the CB box. I changed it to a 4::1 midboom, and replaced the old Scheafer cam with Harken 150 and then again with a Spinlock, and I'm still not happy with it. I tried the vang once but the midboom sheet seems much more effective at flatening, although I can make a good case for installing a travellor I can't afford it now.

The best solution for me, at this time, is to deal with less sail area. However, if Spinlock or someone else comes up with a cleat that will 'let go' partially under particular loads that might work too!
DS2 #6408 "Desperado"
jdoorly
 
Posts: 379
Joined: Mon May 17, 2010 2:24 pm
Location: CT

Postby GreenLake » Sat Jan 08, 2011 2:25 am

I have a 2.5:1 end-boom sheeting setup and so far not had problems with using the cam cleat for the main. It releases when the main is pulled up and that seems to work quickly enough in all conditions that I've encountered - occasionally I'll keep the mainsheet in hand for some periods.

However, that may merely reflect the circumstances that I've encountered so far, obviously.

I was early on taught the "trick" of kicking at the mainsheet from below to get it to release, and this does require less pull to free the sheet. However, I rarely find it necessary.
~ green ~ lake ~ ~
GreenLake
 
Posts: 5182
Joined: Mon Jun 18, 2007 3:54 am

Postby algonquin » Sun Jan 09, 2011 2:06 am

jdoorly wrote:I considered a ratchet block, but that solution just lets you deal more smoothly with the problem, I want to reduce the problem, be able to manage the mainsheet, not be a slave to it. To me that means the goal is to allow the mainsheet to remain cleated for enough time to get something else accomplished, like getting a drink out of the cooler, or updating a DR plot on the chart.


I really don’t feel that additional gear will solve the problem and give you freedom from the tiller that you are looking for. This boat is just to light to allow the attributes that come with a heavier and ballasted keel boat. Additional weight down low in the hull will help. I carry two 50 pound sandbags. I place one on each side of the keelson just forward of the centerboard trunk. It seems to help by adding stability and taking the place of a crew members weight when I single hand and that is quite often. Brad
"Feather" DS1 #818
algonquin
 
Posts: 475
Joined: Sun Sep 30, 2007 9:16 pm
Location: Maine Highlands - Grand Lakes Region

Postby jdoorly » Mon Jan 10, 2011 7:50 pm

You right about equipment and boat weight Brad, none-the-less it is a problem I hope to find a answer for.

I already have 2 100Ah (134 lbs) batteries down low between the mast and CB, and now I have both a first and second mainsail reefs. Soon I will have a small jib for heavier winds. BTW the boat does great in winds below 12kn: I can leave the mainsheet cleated for long stretches of time and the autohelm steers great. It is only higher gusty winds that are a problem for the mainsheet cleat and and the weatherhelm on the tiller. Unfortunetly, it will be a few months before I can see how my smaller main and jib will work in a breeze.

Of course the best solution to this problem is a bronze or lead centerboard, both of which are more than $500. Maybe I can find some depleted uranium in the back yard?
DS2 #6408 "Desperado"
jdoorly
 
Posts: 379
Joined: Mon May 17, 2010 2:24 pm
Location: CT

Postby Alan » Mon Jan 10, 2011 8:37 pm

Jay,

How would you rate the effect of the low-mounted batteries on heeling, boat speed, planing, etc? My nearest reservoir is electric only, so I'm thinking of doing the same thing, as least until a Torqeedo magically prices itself within my budget.
Alan
 
Posts: 696
Joined: Wed Jun 17, 2009 4:39 pm

Postby TIM WEBB » Mon Jan 10, 2011 9:38 pm

Regarding ballast: has anyone tried using Fat Sacks? They are water filled bladders that are used in the stern of wakeboard boats to make a really nice rideable wake. My buddy puts two in one corner of the stern of his Ski Nautique and it makes a wake you can surf on! They're impossible to move around the boat when they're full tho, and take quite a while to fill/empty with a standard 12V bilge pump ...
TIM WEBB
 
Posts: 1208
Joined: Wed May 18, 2005 10:28 pm
Location: RIVERSIDE, CA

Postby GreenLake » Tue Jan 11, 2011 12:43 am

Alan wrote:My nearest reservoir is electric only, so I'm thinking of doing the same thing, as least until a Torqeedo magically prices itself within my budget.


I know that feeling. :cry:

I have "high mounted" batteries. For various reasons, mine are stored right in front of the seats, on either side. Occasionally, I sail without them, but I can't say I notice a strong difference. Could be that cew-weight dominates....
~ green ~ lake ~ ~
GreenLake
 
Posts: 5182
Joined: Mon Jun 18, 2007 3:54 am

Postby GreenLake » Tue Jan 11, 2011 8:40 pm

It's a bit peripheral to this thread, but since the Torqeedo was mentioned, I recently came across this companay (Electric Paddle).

The weight is so low, that it could be a game changer, and the price is a tad more competitive.
~ green ~ lake ~ ~
GreenLake
 
Posts: 5182
Joined: Mon Jun 18, 2007 3:54 am

Postby jdoorly » Wed Jan 12, 2011 3:05 am

Hi Alan. I was going to give you a link to something I wrote in the "DS2 Only" section but now that I look at it again I see it is full of errors and wrong assumptions, for which I apologize, once again.

Here's the deal with weight on the cuddy floor..
935

Fig A just shows a boat at rest, the weight of the boat and crew pushing down on the CG (Center of Gravity) and the bouyancy of the displaced water pushing upwardly through the CB (Center of Buoyancy), the CG and CB always act equal and opposite and inline vertically. When the wind blows on the sail there's a heeling force that heels the boat, Fig B. When the boat heels the hole in the water made by the hull changes shape and the CB moves away from the centerline due to that change. So,when the heeling force forces the CG and CB out of vertical alignment a new righting force, equal and opposite to the heeling force is generated. This force can be measured by measuring the horizontal component between the CG and the CB, it is called the Righting Arm (RA) and the longer it is the more force.

If the righting arm is positive then the direction of the force is to right the boat and it will do so when the heeling force is taken away. If the RA is negative it will try to capsize the boat as in Fig C. Some boats have no negative component in their stability and they will try to right themselves no matter their orientation, even upside down. But some boats heel more than 65 degrees and just won't come back!

Fig D shows the affect of lowering the CG. Not only is the boat stiffer but it will not capsize under the same heeling force.

I can't say the boat got faster or slower or that I noticed any changes since I installed the batteries. But there are a whole bunch of improvements that should happen when you lower the CG!

My battery box is fiberglassed in and can't move and the batteries are well secured inside, but I would be leery of anything used to add weight that isn't tied down- it will shift and fall to the low side just when you need it to stay put.
DS2 #6408 "Desperado"
jdoorly
 
Posts: 379
Joined: Mon May 17, 2010 2:24 pm
Location: CT

Next

Return to Rigging

Who is online

Users browsing this forum: No registered users and 1 guest