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#123183 - 11/10/07 05:52 PM how to point a sloop higher?  
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erice Offline
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japan
hi all,
i've read that raking the mast aft will allow a cat to point a little higher
and someone has said that sailing a sloop rigged cat with only the main will allow it to point a little higher, (in this case a nacra 5.2 with center boards)

anyone any ideas on how much higher for each change?

are we talking 1 degree higher for each and 2 degrees higher for both?

just wondering as if i am sailing "tourist" mode with an extra adult and a couple of small kids on board speed will not be an issue but being able to get around a small lake with minimal tacks will


eric e
1982 nacra 5.2 - 2158
2009 weta tri - 294
-- Have You Seen This? --
#123184 - 11/10/07 07:49 PM Re: how to point a sloop higher? [Re: erice]  
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gree2056 Offline
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If you have many people on the baot you don't want to take off the jib, she will be slow and not fun.

But I feel that my 5.2 does point a little better without the jib, but not enough to sacrafice the power.


Once you go cat you never go back! Nacra 5.2 (Elsies)#1499, running an inter17 spin!
#123185 - 11/10/07 07:59 PM Re: how to point a sloop higher? [Re: gree2056]  
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PTP Offline
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You can't point as high with the jib due to the nature of having a jib. It is because of what the jib does for the main.

#123186 - 11/11/07 08:53 AM Re: how to point a sloop higher? [Re: PTP]  
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Jake Offline
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and while you may not be able to point quite as high with a jib, you go faster and get upwind faster. Also note that as you go faster, your apparent wind goes more onto the nose of the boat...hence the faster you go, the lower you point.


Jake Kohl
#123187 - 11/12/07 08:01 AM Re: how to point a sloop higher? [Re: Jake]  
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jaybird1111 Offline
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Jake, you and peepee are joking, right?

#123188 - 11/12/07 08:11 AM Re: how to point a sloop higher? [Re: jaybird1111]  
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Jake Offline
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uhhh...no - why?


Jake Kohl
#123189 - 11/12/07 08:24 AM Re: how to point a sloop higher? [Re: Jake]  
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jaybird1111 Offline
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You and peepee might wanna have this conversation with the unirig guys, like Curry or Hodges, but here goes:

I'm just trying to understand how:
one "get upwind faster"
by
"lower you point."
'cause
pointing lower
takes you AWAY from the mark... ?!?


Like I suggest above, I'm sure a better explanation will be forthcoming when the Acat guys get done but here goes:

At high angles of attack (eg upwind/high on the wind), the jib, with its comparatively inefficient foilshape, creates more drag than it creates lift. In an ideal world, whenever you go upwind, you'd want to furl your jib and add that sail area to your main, making the main really high-aspect, like Acat, 18sq or other unirig sails (Ccat too). Of course that only will work in the movies ;-)

The jib is also not able to direct flow across the lee side of the main efficiently when at high angles of attack.

Raking back will prolly help some, but not much, and you'll pay for it downwind, so you have to strike some sort of balance there. Raking back will also cause helm imbalance because it changes the center of effort of the sails. So be prepared to reangle your rudders.

#123190 - 11/12/07 08:47 AM Re: how to point a sloop higher? [Re: jaybird1111]  
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hokie Offline
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Getting to a point upwind fast is not about pointing its about VMG; same goes for a mark going downwind. On a Nacra 5.2 or similar the VMG will be better sailing with the jib to cause that flow through the slot that you are talking about, without it the boat is much slower although you can probably point a little higher.

#123191 - 11/12/07 08:52 AM Re: how to point a sloop higher? [Re: jaybird1111]  
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Wouter Offline
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Jaybird,

In the F16 class we actually race uni-rig and sloops directly against one another and yes indeed what Jake says is true.

Pointing is only halve of the equation, boat speed is the other halve.

There are indeed two ways to achieving a high VMG.

The first is by pointing high and not loose too much boat speed

The second is by pointing a little lower and achieving sufficiently higher boatspeed.

Often the sloops excel at the last method.

Also most of the jib related discussions along the lines as you provide are just BS. Jibs are not inefficient sails, to the contrary. Adding sail area to your mainsail actually lowers aspect ratio and does not increase it as you suggest. Really high aspect mainsails have to be depowered significantly sooner, losing all their advantage in the higher wind ranges. For designs like the A-cats higher wind speeds mean anything above 8-10 knots.

A-cats not so much fast boats because of their uni-rig status, The fact that they have highly developped masts and sail and weight next to nothing has something to do with it to.

In the F16 class we use exactly the same hardware for both roles and indeed losing the jib while keeping everything else the same (like the number of crew) is slower upwind despite being able to point higher.

Wouter

#123192 - 11/12/07 09:16 AM Re: how to point a sloop higher? [Re: jaybird1111]  
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Jake Offline
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So...if you take the jib off a Nacra 5.2 it will be faster to A mark? I beg to differ. In fact, if you put a jib on an A-cat (with existing mainsail size) or an F17, etc. It will be faster. The reason the A's don't have a jib is that they are limited to sail area and have found that when restricted to a specific sail area, uni is the way to go since having it all in the main is more efficient than allotting some of that area for a jib. We're talking about two different things here.


Jake Kohl
#123193 - 11/12/07 10:01 AM Re: how to point a sloop higher? [Re: Jake]  
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jaybird1111 Offline
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I didn't say 'take the jib off' I said 'move that same sail area to the main'

Jake, if you and Wouter are correct, then answer this:

--Why are A-Cats unirig?

--Why, when the rules provide for the choice to divide the 18 square meter sail area however one likes, is the predominant sail plan choice for 18sqM, unirig?

--Why are the C-Cats unirig?

--Why are the 18HT boats unirig, with hi-aspect chute for downwind, (which incidentally seems to me to be the optimum sail plan, best of both?)

--ergo, why unirig?

I mean, you yourself said, "since having it all in the main is more efficient"

Why would that be? Unirigs get tanked on a reach, and it gets tanked downwind for sure. There must be SOME advantage...?


Last edited by jaybird1111; 11/12/07 10:05 AM.
#123194 - 11/12/07 10:23 AM Re: how to point a sloop higher? [Re: jaybird1111]  
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Robi Offline
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Who's in?
[Linked Image]

#123195 - 11/12/07 10:24 AM Re: how to point a sloop higher? [Re: jaybird1111]  
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Wouter Offline
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Quote

I didn't say 'take the jib off' I said 'move that same sail area to the main'



Then you answer this :

-1- What is preventing me from adding a jib in addition to moving all that sail area into the mainsail ?

-2- Why are the most succesful catamaran classes like the F18's and Hobie 16's not uni-rigs ?

-3- Why do all modern boats have spinnakers when obviously putting all that spinnaker area in the mainsail is more efficient ?

-4- Why aren't all A-cats using the C-class solid wing sails ?

-5- Why has the A-cat class actively banned full foiling ?

-6- Why aren't the A-cat using spinnakers ?

-7- Ergo why is the A-cat class the way it is ?


I'm guessing your answer to all these questions is :"Because area in the mainsail is more efficient"

My answer is "Because the A-cat class members have written the rules such as to actively encourage the way the A-cats are designed now." Sometimes they have done because that is faster, sometimes they did it for wholely different reasons."

Ergo, looking at the A-cats is not always proof that something is better or more performant.

Wouter

Last edited by Wouter; 11/12/07 10:25 AM.

Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#123196 - 11/12/07 10:35 AM Re: how to point a sloop higher? [Re: Wouter]  
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Rolf_Nilsen Offline
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We already had this discussion, and not that long ago.

http://www.catsailor.com/forums/showflat.php?Cat=0&Board=Test&Number=118042

#123197 - 11/12/07 10:47 AM Re: how to point a sloop higher? [Re: Rolf_Nilsen]  
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jaybird1111 Offline
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Rolf: thanks for the link. I shouldn't have wasted my time here. As you see, I'm new.

#123198 - 11/12/07 10:50 AM Re: how to point a sloop higher? [Re: jaybird1111]  
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Jay, no worries. Thread was heating up and I tought I would save everybody some screen time.

#123199 - 11/12/07 11:28 AM Re: how to point a sloop higher? [Re: jaybird1111]  
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Jake Offline
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Quote
I didn't say 'take the jib off' I said 'move that same sail area to the main'

Jake, if you and Wouter are correct, then answer this:

--Why are A-Cats unirig?

--Why, when the rules provide for the choice to divide the 18 square meter sail area however one likes, is the predominant sail plan choice for 18sqM, unirig?

--Why are the C-Cats unirig?

--Why are the 18HT boats unirig, with hi-aspect chute for downwind, (which incidentally seems to me to be the optimum sail plan, best of both?)

--ergo, why unirig?

I mean, you yourself said, "since having it all in the main is more efficient"

Why would that be? Unirigs get tanked on a reach, and it gets tanked downwind for sure. There must be SOME advantage...?



The question was: "someone has said that sailing a sloop rigged cat with only the main will allow it to point a little higher, (in this case a nacra 5.2 with center boards)". The question was not, "can I redesign my entire boat to point higher".

I explained why an A-cat doesn't have a jib...it's because the A-cat (the 18sq as well) is limited to X sail area. When under such limits, it is more efficient to have it all in the main instead of building a smaller main to allow for some sail area in the jib. This may also be a factor of the lightweight boat that it demands efficiency more than it needs horsepower provided by a jib. A single sail is also much easier to handle when sailing solo.

In the case of this 5.2, which this thread is about, the boat will be slower upwind if you simply leave the jib off. The main is shaped wrong for it, the boat is not balanced for it, and it looses sail area and overall speed. Yes, it might be able to point slightly higher without the jib but, overall, it will be slower if you leave the jib off.

You're confusing this topic with a uni-platform vs. sloop. We're strictly talking about a sloop platform (i.e. thread title).


Jake Kohl
#123200 - 11/12/07 11:39 AM Re: how to point a sloop higher? [Re: Jake]  
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jaybird1111 Offline
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jaybird1111  Offline
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Actually, no, I did answer the question:

"At high angles of attack (eg upwind/high on the wind), the jib, with its comparatively inefficient foilshape, creates more drag than it creates lift. In an ideal world, whenever you go upwind, you'd want to furl your jib and add that sail area to your main, making the main really high-aspect, like Acat, 18sq or other unirig sails (Ccat too). Of course that only will work in the movies ;-)

The jib is also not able to direct flow across the lee side of the main efficiently when at high angles of attack.

Raking back will prolly help some, but not much, and you'll pay for it downwind, so you have to strike some sort of balance there. Raking back will also cause helm imbalance because it changes the center of effort of the sails. So be prepared to reangle your rudders."


See? I told the man why his jibbed boat won't point so well, and I offered him suggestions to help. (That would be the 'raking' mentioned above.)

I won't make the mistake of posting, much less travelling to this site again. newbie out

#123201 - 11/12/07 12:16 PM Re: how to point a sloop higher? [Re: jaybird1111]  
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NCSUtrey Offline
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Somebody is a polly pissy pants...

#123202 - 11/12/07 12:34 PM Re: how to point a sloop higher? [Re: NCSUtrey]  
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Clayton Offline
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Dang! Lost one in 5 posts! Do I hear 4!!!!!

Some people are wayyyyy too sensitive.

I've got a sensitive side too, but I leave it hidden when I'm around any cat sailors, don't want it stepped on <img src="http://www.catsailor.com/forums/images/graemlins/smirk.gif" alt="" />

Happy Veterans Day!!!

Clayton

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