What boatspeed should I expect, as a percentage of True wind?

[44'cruisingcat]

Nice sail last year in 15-20 kts, anchor up in Cooktown to anchor down in Watson's bay, Lizard is.

[arsenelupiga]

Originally Posted by BigBeakie

What are thoughts of having an inside rigged screecher, as opposed to an outside the shroud rigged Code 0 ? For light upwind work.

The same screecher can go outside shroud and be used in higher winds reaching?

i have carbon screecher designed for outside shrouds only. And can go 40 app in good conditions. Run it inside shrouds with some shrouds interference, and managed 4 - 4.5 kn at 35 app in 8 kn true which is 2.5kn VMG. This type of conditions is quite rare but do happen. Not prepared to have sail exclusively for this but I am in process of designing next screecher that will be actually 15 pct smaller, as this one expires soon. Idea is to be versatile enough to run it properly inside shrouds. Current screecher adds very little in stronger winds. i will beef up with large sym for small winds. I think it is just not designed well or maybe already stretched.

that was sailmaker design for upwind use case. see shroud around 1/3 from back.

[Tupaia]

Originally Posted by arsenelupiga

i have carbon screecher designed for outside shrouds only. And can go 40 app in good conditions. Run it inside shrouds with some shrouds interference, and managed 4 - 4.5 kn at 35 app in 8 kn true which is 2.5kn VMG.

You miss the point upwind performance is only necessary in light winds because the apparent wind difference is so much greater. A fast boat will create it's own wind and in the conditions you describe should be able match or even exceed the true wind speed. VMG is irrelevant in these circumstances.



In 8 knots of TW if you can pull the AWA down to 30 degrees you have a 10+ knot boat speed, the TWA will be 70-75 degrees and the VMG will be a poor 3-4 knots BUT you are NOT trying to sail directly to windward you are making use of the boats ability to sail close to the wind to achieve the highest speed possible towards your destination.

[arsenelupiga]

Originally Posted by Tupaia

You miss the point upwind performance is only necessary in light winds because the apparent wind difference is so much greater. A fast boat will create it's own wind and in the conditions you describe should be able match or even exceed the true wind speed. VMG is irrelevant in these circumstances.



In 8 knots of TW if you can pull the AWA down to 30 degrees you have a 10+ knot boat speed, the TWA will be 70-75 degrees and the VMG will be a poor 3-4 knots BUT you are NOT trying to sail directly to windward you are making use of the boats ability to sail close to the wind to achieve the highest speed possible towards your destination.

thread is not reaching specific, i thought. Upwind % of TWS is important as well. We actually used it in tropics. I am hoping to achieve 5 kn at 31 in 8 kn wind that gives 3.2 VMG with new sail. Your example produces 3.4 VMG. Probably there is better way for upwind for faster boat in 8 kn?

[GRIT]

Tupaia:

Thanks for your comments, I hadn't considered sheeting the schreecher to the sterns, due to the wide sheeting angle outside the shrouds. I've been concentrating on going very high upwind, since the AWA will pull forward quite readily. I'll run the numbers to see what angle the sheets will have, run to the sterns, and inside the shrouds. It would be nice to have a larger schreecher than we have planned.

We have a code 0 and are fairly happy with it, though I think it should have been bigger (it's 94m2). The spinnaker sheets will run identically to the Code 0 sheets. I may just buy double cheek blocks, for in front of the daggerboards, in lieu of the singles we have in waiting. And double blocks for the aft sheet blocks too. If I can leave all the sheets in place, I'll be more likely to use the sail.

The sheets run back to the stern, then fwd to just fwd of the daggerboard, to a block, then on to the winch 30cm from the mast. I'm going to install a clutch 1m before the winch, as a fairlead, and to clutch the sheet. With a clutch, I have the option of operating the jib sheet, or adjusting the halyards (same winch) while still running the code 0, or spin.

I have a schreecher planned, but would only have been 55m2, whereas my jib is 37m2. It would run from the bowsprit, and sheet to the same track as the jib (fwd of the windows, either side of the front cockpit). The jib tracks are fore and aft, 85cm either side of the mast.

Now that you've put that bug in my ear, I'll see about sheeting it further aft, and have a sheet lead to the top of the house, to narrow the angle. I've got a bit of room just next to the aft edge of the solar panels. I'll bet I can get another 10m2 of sail area if I can bring it inside the shrouds.

Something I'm considering changing, is to raise the spinnaker haylard to 18m.

There were some communication issues, with Selden, and the spinnaker and code 0 are both at 17m above the deck. The spinnaker was supposed to be at 18m (the mast is 19.5m) above the deck, which would allow more sail area. Still, Mack Sails thinks they can get us an Asym at 150m2, and that might just do the trick. I'm going to have them use every cm2 they can get on this sail.

I've been using the Outremer 4x as my baseline, as a reasonably safe/quick sail area for a performance boat.

We don't need to lift a hull, but we'd better be quick.

As an aside, we don't even know if we are fast. We haven't yet had the opportunity to sail next to anyone. We've passed a few monohulls, and not yet been passed ourselves, but I'm eager to sail next to someone else in a fast cat.

A friend has a very hot Outremer 49, with extended carbon mast, and extended hulls. We've been trying to sail together, but haven't yet managed it. He's just as curious as I am, as to how his cat sails compared to others. Nobody's ever passed him yet, and he's had it longer than I've been sailing mine.

Thanks for your comments.

Cheers.
Paul.

PS. I apologize for the disjointed post, my mouse won't click to allow me to move paragraphs around.

[Tupaia]

Originally Posted by arsenelupiga

thread is not reaching specific, i thought. Upwind % of TWS is important as well. We actually used it in tropics. I am hoping to achieve 5 kn at 31 in 8 kn wind that gives 3.2 VMG with new sail. Your example produces 3.4 VMG. Probably there is better way for upwind for faster boat in 8 kn?

I suggest you re-read the Original Post.
To quote
I really don't care to talk about VMG, but I'd like to know how fast other cats are sailing in winds of less than 15 knots, at what angles, and using which sails. A little info on the boat would be nice too.

[Tupaia]

Originally Posted by GRIT

Tupaia:

Thanks for your comments,


SNIP


Cheers.
Paul.

PS. I apologize for the disjointed post, my mouse won't click to allow me to move paragraphs around.

I would be wary of having two sheets on very light sails. The weight of the lazy sheet itself, the fact that it is very long and hangs from the clew over places that it can easily snag. You can't realistically tack or gybe a sail like this anyway far better to furl it, tack or gybe then walk the sheet round to the other side and unfurl it. It will be nice and relaxed no flogging and it is not as though you will be doing it in rough conditions. Having only one sheet makes it easy to drop the sail especially if it on the bow sprit/ prodder. My bow sprit/ prodder is just over a metre long so I have a net rigged below it that gives me access to the forward end. Being able to take the sail off means you can keep it light by not having any UV strip and it is out of the way in a locker when the going gets tough and you are trying to beat under working sails.
You do need to check sizing with the mast guys as the forces when powered up are massive.

[GRIT]

Tupaia is correct.

Threads seem to get lost in talking about vmg. I understand it's important, but I find it clutters the thread.

For my purposes, and to keep the thread a little lighter, I'd like to forego discussions of VMG.

I'm interested in pointing high, and sailing fast. We can assume that vmg will be good if we can do both (point high, and sail fast), then perhaps we won't get lost in the minutia of VMG.

It's a great discussion so far, and I'm learning a lot from you more experienced cat folks.

Cheers.
Paul.

[GRIT]

Tupaia.

I've heard of folks doing that, with a single sheet. It just seemed like a lot of work, considering the extra block, extra length sheet, and fairlead I have, to accommodate for the forward cockpit.

I'll try it with the code 0, and see how it goes. It's true I wouldn't be tacking often, and the UV cover on the Code 0 is affecting the sail shape more than I'd have thought.


Cheers.
Paul.

[GRIT]

Could someone please explain the difference between a Code D and an Asymetrical Spinnaker?

Are they the same thing?

Thanks.
Paul.

[Tupaia]

I'd never heard of Code D before but it would appear it is a cross over between a Code 0 and Asym.





No idea what "langon" translates to. Must be a secret code

[GRIT]

I believe tangon is a pole, as it says "avec tangon au vent" which I assume means poled to windward.

I found it on Google. "Tangon au vent" is an outrigger pole, so I guessed right; more or less.

Thanks for the chart. That helps.

Looking at that chart, I'll keep with the Asymetric, or Symetric Spinnaker.

Cheers.
Paul.

[fxykty]

Originally Posted by GRIT

I believe tangon is a pole, as it says "avec tangon au vent" which I assume means poled to windward.

I found it on Google. "Tangon au vent" is an outrigger pole, so I guessed right; more or less.

Thanks for the chart. That helps.

Looking at that chart, I'll keep with the Asymetric, or Symetric Spinnaker.

Cheers.
Paul.

On a cat there’s no need to pole out a blade jib, but it will be necessary to pole out an overlapping genoa. In both cases you’ll need a way to rig a block for outhaul/downhaul on the rail a couple of metres back of the front beam. The jib out hauled with or without a main is our 25+ knots TWS DDW rig. It works fine wing on wing in lighter winds and unlike a monohull the mismatched sail sizes don’t really matter.

A symmetric spinnaker is perfect for DDW light to moderate and all the way up to 120* TWA in light wind. There you have a cross over with a gennaker/code 0 for reaching for light to moderate+ wind, then another crossover at 60* TWA with an inside the shrouds upwind screecher for light winds and the jib for moderate+ winds. So three flying sails, two of which furl bottom up.

The only benefit of an asymmetric spinnaker is using a top down furler rather than a sock with the symmetric spinnaker. The ASY can work for DDW, especially if you can move the tack to the windward hull.

The gennaker/code 0 works all the way down to 160* TWA with the tack moved to the windward bow.

[44'cruisingcat]

If you choose to ignore VMG when talking about sailing upwind, you're basically wasting your time.

10 knots in 10 knots at 45 apparent sounds good right?

[Tupaia]

Originally Posted by fxykty

On a cat there’s no need to pole out a blade jib, but it will be necessary to pole out an overlapping genoa. In both cases you’ll need a way to rig a block for outhaul/downhaul on the rail a couple of metres back of the front beam. The jib out hauled with or without a main is our 25+ knots TWS DDW rig. It works fine wing on wing in lighter winds and unlike a monohull the mismatched sail sizes don’t really matter.

We have a similar setup DDW using 2 head sails. It is much more controllable especially at night than a spinnaker. Contrary to instinct we have found in very light winds that when wing on wing downwind (170 degrees plus) flying the bigger sail on the windward side and the smaller sail on the leeward side allows the smaller sail to feed wind into the larger sail to keep it from collapsing.