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PostPosted: Sat Sep 30, 2017 6:47 am 
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I have enjoyed using the island platform as a way to explore different forms of sailing/rigging. These islands are great for this. First I made a jib that furled into the main sail. Then when Hobie came out with the spinnaker rigging, I set the island up with two snuffing bags- one on each side. One was for the jib and one for the spinnaker. This sloop rig uses a 110 percent jib and has been a blast to sail. Now I want to take it another direction and add a staysail between the jib and mast making this a cutter rig. Below is a nice YouTube video discussing these riggs and some of their advantages.

https://youtu.be/JQoinc_rPWA

The staysail in the cutter rig will be much smaller than my jib, cut very flat and will basically only serves to feed more air to the main. This hurts pointing in a close haul but adds speed in any reach. What I plan to do is have the staysaIL furl into the main. The jib and spinnaker will remain in the Hobie snuffing bags making for a four sail island. That way all sails are ready for quick deloping without having to change out sails. I could also make the staysail self furling like I did a previous jib which simplifies things.

When pointing close hauled the best rig is the mainsail by itself. I will be able to release the tack of the staysail so that it piviots aft and becomes one with the main, maximizing close hauled sailing without taking the staysail down. As soon as I fall off into a reach, I pull the tack line so the staysail pivots forward of the main and off we go.

The rigging is already completed and tested using the jib in both positions (staysail and foresail). The sail will take a couple mounts for the sailmaker to make (busy season for them) and I will néed to renforce a an additional padeye mid bow. I should have some pics and videos in a few months.

I have to worry about extra forces on the mast and the bow padeye. I don't want to distort the bow near that front hatch. Also may have a fight with leehelm although that has not bee a problem with the jib yet. Will have to see. Anyway looking forward to another experiment.

Anyone sailed a cutter before? Looks like fun to me. I hope to add speed when reaching and greater rigging options as winds pick up.

This is the idea...

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Greg

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PostPosted: Sat Sep 30, 2017 10:11 am 
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PostPosted: Sat Sep 30, 2017 7:17 pm 
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Thats kinda the setup I ran for about 5 yrs before putting my wing on, 3sails, 3masts, (didn't know that's what it's called). You may need to add a bowsprit because the main on the TI is mounted really far forward, and with 3 sails it's really hard to get enough separation between the sails to get air in. I also had to re-enforce and brace the bow much better because of the added strain from the extra sails. The other reason for the bowsprit is to angle all the foresails so they create lift to prevent diving and pitchpoling (I've pitchpoled plenty of times). Your boat will scream with 260 sq ft plus sail area. We recorded our fastest speeds with that configuration on a run from ft desoto to egmont key in around 20 mph+ winds, with all sails up, and both wife and I hiked out on our tippy toes, we were maintaining 20mph plus for quite a while, (probably really dangerous, and we shouldn't have tried). That was back in I think summer 2011, I don't remember many more specifics besides having two scuba tanks lashed to the rear AKA's.

I eventually widen our TI quite a bit to support all that extra sail area ( ama flotation is an issue when showing that much sail on a reach).
One thing I think you will find out is with your spinnaker ( if it's like mine) as you get above 90 degrees' (getting into upwind) my spinnaker tries to collapse, the small middle sail helps keep air fed to the spin so it doesn't collapse, so you can point a little higher with the spin before having to furl or snuff it. My 35 sq ft jib was on a furling mast, I usually ran it half furled when using the jib with the spinnaker on a reach.
Never had any issues with downwind sailing or sailing on a reach, upwind sailing and pointing higher and closer to the wind was always my issue, our TI was never very good at upwind until I got into the wings, then all the upwind sailing problems went away completely.
Have fun with it
FE

Edit: when re-reading the post, I wrote 100sq ft jib (oops), should have been 35sq ft (corrected above), sorry


Last edited by fusioneng on Sun Oct 01, 2017 7:09 am, edited 3 times in total.

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PostPosted: Sat Sep 30, 2017 8:58 pm 
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Hi FE. Since I have an AI, I have a little more room to work with on the bow. Plan to try this without sprit. Measurents have me putting a reinforced padeye about 1/3 back from the tip of the bow. That can be moved and i am also going to keep the staysaIL small enough that I will be maintaining enough separation between headsails. The spinnaker would not be used when the boat is acting as a cutter. Just jib and staysail.

Some cutters use a Yankee sail instead of the jib. I actually like the looks of that better. Still, I chose a jib instead because it works better downwind than a yankee and I woun't have to change rigging when going downwind vs upwind. The picture in the first post is with a jib vs a thinner yankeen just like I plan to do. I won't be using the spinnaker unless winds are really light. The jib is plenty of downwind boost.

More sails, more lines, and Im sure more complex. But I like this sort of thing. I actually enjoy staying busy while sailing.

Selling my soul for more speed,

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PostPosted: Sun Oct 01, 2017 6:35 am 
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That's something I kind of figured out eventually also. With a larger jib on downwind if you put the jib to one side and the main to the other (with a barber hauler), the down wind performance isn't too bad, as a result (with me anyway) I found myself using the big spinnaker less and less, anymore I just leave it hanging in the garage and don't bring it along unless I'm planning a long downwind run, (which is very seldom). Actually I abandoned my old G2 assymetric spinnaker, ( using it was too limited, ( downwind only). In favor of something closer to a code zero or screacher, that can double as a big genoa and also works upwind, with a twist, I added an inflatable wing parafoil to the leading edge to hopefully get it to be able to point higher upwind, (the parafoil does nothing when downwind, it only fills up with air on a reach, kind of forcing it to work like a genoa. Everything works great with one caveat. It only works up to one to one with the wind, as soon as you exceed 1=1 with the wind it collapses and becomes one giant airbrake, lol we all live and learn.
We see a lot of really big monohulls cruisin up and down the intercoastal around here with giant genoas, and I've seen several similar to the pic you showed of a cutter, always wondered what that configuration was called, now I know.
I just like coming up with new ideas, then trying them out extensively, this gives me a reason to go out most weekends, plus I get good exercise, (I always pedal 100% of the time, I know most of the time pedaling does nothing to improve my speed, but does keep me in shape).
I'm just out there havin fun tryin to learn and come up with something cool and useful, and tryin to occupy my mind.
In seven years my ultimate goal has not changed, which is to complete the 300 mile everglades challenge in the experimental class (class 6), in a modified TI in under 24 hrs, (would need to average 12-13mph forward speed the whole way, totally independent of actual wind speed and direction) everything I have done is for that specific goal. Hopefully I'll get there someday.
FE


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PostPosted: Sun Oct 01, 2017 9:16 am 
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What does it mean to have the jib furl into the main sail? Reason I ask is that I had asked someone in the past (regarded a sailboat) how you tack a boat with the two fore sails deployed and the answer was that often you furl the most forward sail before the tack, then unfurl it on the other side for the new tack. Otherwise the most forward sail can have trouble getting around the luft of the second fore sail that is just behind it.. Seems that a nice working furler for the most forward sail could end up being useful????


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PostPosted: Sun Oct 01, 2017 12:15 pm 
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Hi Walt. The jib furling into the main is what happens if your jib is attached at the head and foot of the mast and then you furl the main. Both your jib and your main roll up around the mast as one. 12 minutes into the following video you see me demonstrate this.

https://youtu.be/DEofPRTQM24

When you have two headsails in front of the mast and you tack, you release the foremost sail's sheet first , in this case the jib sheet. Then as you come about (turn) the foremost sail will naturally slip between the gap in the sails. You pull the jib sheet tight and now do the same for the staysail just behind it. No furling actually takes place. Since the staysail is so much smaller and because of the gap, thEy don't really interfere with each other like you would think they would. You can even make the staysail self tacking avoiding sheets all together like in the video below...

https://youtu.be/v7jis_to_NA

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PostPosted: Mon Oct 02, 2017 6:58 am 
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Aha! Wow, lots of cool and clever stuff in your video! Thanks!


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PostPosted: Mon Oct 09, 2017 12:46 pm 
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vetgam wrote:
The staysail in the cutter rig will be much smaller than my jib, cut very flat and will basically only serves to feed more air to the main. This hurts pointing in a close haul but adds speed in any reach.

Just for an offseason mental exercise, I'll compare the above "jib feeding main" theory vs. the latest windtunnel simulation results and theory which is kind of reverse... "main loads up jib" that has been discussed in another thread. Are there any practical implications if the new theory is true that the jib does the work and the main is the modifier? I think the only implications are that the jibsheet and jibstay will be loaded up disproportionately to the jib size. In fact, I read a top advantage to a cutter rig on large yacht is to make jibsheet loads manageable for a single hander.

NASA mythbusts the theory that lift comes from a venturi constriction and resulting air speedup on the upper side of airfoil in https://www.grc.nasa.gov/www/k-12/airplane/wrong3.html . Granted PART of their critique is the lack of the other side of a venturi, which the jib may comprise. But it seems to be agreed among top sail nerds and their windtunnel results (referenced in Kayak Sailing section) that the jib/main slot in a racing yacht design only gives traces of extra velocity atop the main, and mainly gives a stagnating backup effect under the jib. Presumably this would have a domino effect with a cutter, where each sail stagnates and thus powers up the sail ahead of it. But maybe the size variation and lesser overlap accounts for less upwind efficiency.

By the way, NASA also poo-poos on the theory of lift coming strictly from asymmetry of an airfoil (which sails don't have) in https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html . Also it gives thumbs down on lift coming from air bouncing off the underside of a foil in https://www.grc.nasa.gov/www/k-12/airplane/wrong2.html . All of these incorrect theories have elements of truth and have sufficed as rules of thumb, albeit with dangerous counterexamples. They give the "true" answer in the last paragraph here https://www.grc.nasa.gov/www/k-12/airplane/bernnew.html which is basically that lift surpasseth all understanding, at least for the non-mathematical:

Quote:
The real details of how an object generates lift are very complex and do not lend themselves to simplification.
...
For example, from the conservation of mass, a change in the velocity of a gas in one direction results in a change in the velocity of the gas in a direction perpendicular to the original change. This is very different from the motion of solids, on which we base most of our experiences in physics.

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PostPosted: Tue Oct 10, 2017 4:29 pm 
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It occurred to me that it might still seem controversial that the jib "slot effect" is a dead myth. The jib is still a mega assistance. Try googling slot effect in image mode and hitting the "visit" button for the explanatory web pages. For example notice the central caption below that a large jib can give 90% of your drive!!!

Image

That unless you bring down the feeble 10% main; then the jib is more feeble alone. Note the velocity map below; the jib is a monster due to the choking effect of the slot. There is some smoothing of flow over the main, but it's thrust angle is uselessly to the side vs the forward pulling jib:

Image

Below is a pressure difference map of a smaller jib rig where jib is 30% size of main but 40% of total rig force yet 50% of forward drive (due to jib better angle): Note the orange color on mainsail where the jib overlaps - it is orange = 0 = a useless dead zone rather than enhanced zone!

Image Image

I include an odd finding that the sails (esp jib) actually experience upwash angle to windward. These type of pix are from various sail makers and boat design sites; here it is in words from boatdesign.net :
Quote:
0. Venturi-effect myth: Faster airflow through the slot has been said to increase the rig's power.

For the most part, this does not occur. A venturi is a closed passageway that forces air through a restriction. Air encountering a slot between two sails will also flow around the sails on either side of the slot. There is some variation in flow speed within the slot, but the average speed is slower than freestream.

I would put it as the slot effect is now seen as a choke down area to inflate the underside of the jib for power and a better angle for drive. You would never entirely close the choke because the secondary goal is to make it harmless to the mainsail.

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PostPosted: Tue Oct 10, 2017 7:11 pm 
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Love this stuff. Thank for sharing Daft. I'm going to need to read this again with a strong cup of coffee first thing in the morning when I'm most alert. :D

I noticed that when I now use a jib with a low cut clew (very little space between the foot and the bow),I get a noticeable boost in jib power. Either that or going to a 110% vs 100% jib has made the newer jib im using now more of a work horse.

It will be a sad day when there is nothing new to change on the boat.

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“Out of sight of land the sailor feels safe. It is the beach that worries him.”
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PostPosted: Tue Oct 10, 2017 8:35 pm 
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Thanks vetgam, but while I was trying to rediscover an article on jib foot vortices https://cdn2.hubspot.net/hub/209338/new ... index2.htm for you, I noticed google showing your older posts on the jib slot effect. You already seemed wise to the issues, and maybe you suffer foolish replies more gladly than they deserve if it advances the discussion. So I better bow out, not knowing when I am typing nonsense amid all the politeness.

BTW, there are other interesting sail aerodynamic articles in the link above, possibly including foot vortices. Also I was intrigued by physical windtunnel pictures of trimming a jib. http://www.sailingworld.com/how-to/boat ... low#page-2 . The discussion is kind of obvious, but consider the picture of a well trimmed jib:

Image

It is supposed to be wonderful how the jib is holding the laminar flow to the main which would want to stall otherwise. BUT this means to me the main really wants to swing out to a lower angle of attack and be more efficient, yet the jib would then try to deflate it. So good jib trim seems to need to sabotage the main potential and blossom out as the main driver at a better angle of attack.

However, what does this mean for small jibs like yours which may have more or less effect as you go up the main - which scenario do you tune for?

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PostPosted: Wed Oct 11, 2017 7:13 am 
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daft wrote:

However, what does this mean for small jibs like yours which may have more or less effect as you go up the main - which scenario do you tune for?


Daft I not sure what you mean by tune for. Jib trimming is different vs the main.When I first set the jib, I typically set it in what is can an acceleration trim, where there is more bow to the foot of the sail. In other words the sheel is more relaxed. This maximizes powore a the expense of pointing abilities. As the boat maximizes speed I pull in the jib sheet to a point where speed is maintained but now pointing is maximized. They refer to this as maximized trim. Pull the sheet too much and the jib will stall. I set the main after setting the jib.

What do I think is really happening between the jib and main. I really have not figured it out based on all the reading I did. Obviously lots of theroy out there. Great reading though. Experimenting with the jib keeps my interest in sailing. Not to mention the convenience that the Islands bring to the table.

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“Out of sight of land the sailor feels safe. It is the beach that worries him.”
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PostPosted: Fri Oct 13, 2017 6:05 am 
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In the end, when you add the jib to the main, the mains power actually gets compromised while the jibs power is amplified to a point where the two sails provide more force than the sum of the individuals. It's opposite of what you would think. The jib is not actually enhancing the mains power. It does reduce the mains drag though.

With a cutter rig, when you add a staysail between the jib and the main, the.staysail adds no power itself but redirects the air in the slot back towards the jib and towards the main which enhances the power sum of all the sails. It does this by increasing the jib power and reducING the mains drag even more. That's my understanding.

So I need to accept that when I add this staysail, I'll have greater forces on the mast to worry about. If I break the mast, so be it. I want to push the boat as far as I can.

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“Out of sight of land the sailor feels safe. It is the beach that worries him.”
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PostPosted: Fri Oct 13, 2017 8:07 am 
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When I was running the spinnaker, jib, and main (265sq ft of sail) all at the same time on a reach, I had difficulty with the top of the mast bending over to one side a little too much. For a while I ran side stays attached to the very front of my mast topper (about 8-10" in front of the main mast), but they were rigid lines (non stretching), Quite a few years later someone on here (don't remember who), posted pics with side stays that had bungys on them, I remember thinking what a great idea, (why didn't I think of that one (lol)). It allowed his mast to float around as designed, but limited it from bending too far.
In my case I used those side stays a couple times then abandoned them (too much of a pain to rig). I ended up rigging a single rope tied to the front of the mast topper, that I used as a trapeze line when really pushing the boat way too hard with all the sails out. While hiked out I just hung onto the line, or tied it off on an AKA when pushing the boat way too hard. Ended up using it maybe 3 times, then stuffed it in one of the mesh pockets (just in case I needed it). Found it in the mesh pocket when cleaning the boat out a couple weeks ago, all moldy and smelly so I tossed it (lol).
Just throwin out ideas
FE


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