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  #21  
Old 04-02-2007
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Skrap-

Be aware that the GPS doesn't work as a compass unless you're moving. It can't give you a direction if you're sitting still, as it uses changes in the GPS reading to determine your heading. The GPSMap 76CS does have a fluxgate compass and altimeter in it, which doesn't require you to be moving.

FYI, raising the boom, while a convenient idea, isn't always a good idea, as it will move the Center Of Effort upwards, increasing the weather helm on the boat and such. Not all that ideal for a smaller, less stable boat.
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—Cpt. Mal Reynolds, Serenity (edited)

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  #22  
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I am aware of the GPS compass issue. Fortunately, I have a pretty inherent ability to know roughly which direction the 4 points lay, as long as I am outside.

Regarding raising the boom... The cat 25 comes with 2 options, the standard and the tall (I believe the hull is the same). Now, I understand that on the tall rig, you have more sail area, and maybe I am not understanding all the dynamics at work here, but wouldn't using a shorter, standard mainsail on a tall rig with the boom raised, be no different really than sailing with the tall rig with the main reefed?

Or is the difference in dynamic because the boom would be further from the centerline of the hull?
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  #23  
Old 04-02-2007
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The key here is 'Center of Effort'. Think of the forces of the sail being generated from the geometric center of the sail (not true, but hey, gotta start with something easy with no math.. ) If you raise that point up, you are raising the 'center of effort', which means more heeling moment, change in the portion of the hull that is below waterline, how that interacts with the 'center of boyancy', and 'center of balance', etc.

for a reefed main the center of effort lowers the more you reef, which is what you want along with less square footage to catch the wind lowering the power. What you are talking about raises the center of effort, resulting in many bad things.


Spinnaker Sailing Online Sailing Course = Lesson 2

doesn't talk about the center of effort in relationship to the rest of the forces in the boat, but the picture is useful.

Last edited by tenuki; 04-02-2007 at 06:09 PM.
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  #24  
Old 04-02-2007
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Quote:
Originally Posted by skrap1r0n
Or is the difference in dynamic because the boom would be further from the centerline of the hull?
Got it in one... the whole sail has shifted upwards, so the center of effort for the main sail has effectively shifted up by the same amount. The boom on the tall rig version isn't any higher than the standard rig IIRC, so reefing it brings the center of effort down, not up...

Another point I should have made earlier... moving the boom up and using the tall rig, increases the weight aloft effectively, by raising the Center of Gravity of the boat slightly. The boom is now x-feet higher...so the keel has more weight working against it... combine that with the higher Center of Effort, you're starting to get a more tender boat... Do you like swimming???
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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Last edited by sailingdog; 04-02-2007 at 06:06 PM.
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  #25  
Old 04-03-2007
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Quote:
Originally Posted by sailingdog
... Do you like swimming???
Gotcha! I love swimming, but only in a planned circumstance. I already had one kid yell at me. He was asleep crosswise in the V-berth and came out yelling at me when the boat heeled unexpectedly. He was complaining about being asleep one minute and standing on the wall the next minute. He wasn't happy, I thought it was funny. (the boat didn't heel that much, just to the rail, but it was a sudden gust...)
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  #26  
Old 04-03-2007
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This is a great book that is clearly written and has great graphical support. Standard crew issue on my boat!

Sail and Rig Tuning by Ivar Dedekam
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  #27  
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Skrap-

Since my boat doesn't heel... I do other things to wake sleeping crew... like going through the swells to get water to wash over the decks and soak the poor bastards... unfortunately, my crew is starting to figure out that I'm turning the boat in their sleep, and wake up before I get a good wave...

One of my crew, a girl that crews regularly, was smart and curls up on top of the cabin, beneath the dodger... I'd have to use a hose to soak her there... totally protected.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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  #28  
Old 04-03-2007
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Skrap, it is possible to install a bimini on a tall rig Catalina 25 with no modifications at all, but the boom will be 1' lower than the boom on a standard rig boat. If you buy a new, shorter mainsail, it'll cost you
$7-800., and you can install the bimini at the same height as the standard rig boat, but when you get ready to sell your boat, you'll be selling a boat with a bastardized sail, and that won't do anything good for the value of your boat. There's a third alternative, that I think is much better than either of those two alternatives. Your mainsail probably already has a cunningham installed in it, about one foot above the boom. If you have your sailmaker install a cringle for a flattening reef at the same level on the leech of the sail, you can use the flattening reef and the cunningham as a sort of short reef. Then, when you raise the mainsail to the top of the mast, the foot of the sail will be about one foot higher, and that will provide more clearance for a bimini. Except for the most recently built C25s, the height of the boom is adjustable.

The advantage of this method is that your mainsail is capable of being used in its full size. If you wish, you can lower your bimini in light air, shake the short reef out of the mainsail, and use the full-sized sail for racing or cruising. By raising the boom one foot, your boom will have the same amount of clearance as a standard rig boom, and that will provide plenty of room for a bimini. The nice thing about the tall rig boat is that the extra sail area makes it much more enjoyable to sail in light air. If you cut your sail down, it permanently destroys that advantage.

For daysailing and casual cruising, sailing with a short reef in the mainsail won't hurt the boat's performance significantly, or make it tender. By comparison with a standard rig boat, it will still have a bigger jib than a standard rig boat, but the size of the mainsail will be about the same as the size of the standard rig mainsail. Your mainsail won't be carried any higher than if it was sailed without the short reef. It'll be carried at the same height, but the boom will be one foot higher, so there'll be a little less sail area at the foot. That certainly won't make your boat more tender than any other tall rig C25 sailing without a reef.
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  #29  
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sailormon6,

That is an excellent point and idea..guess he needs a loose foot main.

One of the most convenient posts I saw here in the last few days..

I can raise my boom a lot, simply by rigging the cuningham, on the tack end of the main and hoist the sail to the max, allowing the cuningham to to go up, thus lifting the end of the boom. Almost 40cm.
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I am not sure I will even worry about the Bimini on this boat, at least not under way. It has a pop top that I cannot use while under way either. The Boom vang gets in the way of that. I have to unhook the boom vang to pop it. Raising the boom would resolve a lot of minor issues, but not at the expense of sailing. I think I am going to pop over to the C-25 owners group and see if there are some alternate work arounds or what others are doing.
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