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31-10-2020, 11:14
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#31
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Registered User
Join Date: Oct 2011
Boat: KH 49x, Custom
Posts: 1,765
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Re: What boatspeed should I expect, as a percentage of True wind?
Thanks Brent. We had both boards down, and will start to experiment with using one or the other, as soon as we get our up-haul/down-haul equipment designed and installed.
The boat does turn on the proverbial "dime" now though. It's so much more responsive to the helm.
We sailed again today, for 25 miles, and found the same results as yesterday. We mostly had winds abaft the beam (110-120 AWA), and were sailing at 66% of windspeed most of the time. When the wind went forward of the beam, we managed 80% a couple of times, but there was a favourable current, so we'd have been sailing at 70-75% of windspeed. Still pretty thrilling for a couple of former monohull (fat cruiser) sailors.
Cheers.
Paul.
__________________
If you can dream it; with grit, you can do it.
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31-10-2020, 11:29
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#32
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Registered User
Join Date: Jun 2017
Location: Coastal Virginia
Boat: Maine Cat 38
Posts: 611
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Re: What boatspeed should I expect, as a percentage of True wind?
Your polar data is looking very good. I expect tweaking the boards will enable squeezing a bit more speed out. But the numbers as they are now seem reasonable and satisfying.
__________________
Brent
S/V Second Star
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31-10-2020, 14:15
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#33
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Registered User
Join Date: Oct 2011
Boat: KH 49x, Custom
Posts: 1,765
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Re: What boatspeed should I expect, as a percentage of True wind?
Thanks Brent.
The board tweaking might help, but where I really need help is on mainsail trimming. I heard flat tops are easy to trim, but I can't believe they're as easy as it seems. I'm sure I'm doing something wrong.
The tell tales are most often doing just what I want them to do. I'm going to try to get them to flip to leeward more often, as I read that the mainsail should possibly be trimmed a little tighter than what the tell tales show. Though, every time I try it, I lose speed.
I'm also having luck with a very tight leech, and the main far to leeward, in 12 knots or so.
I've got to pay more attention to the foot tension too. I know I can do better.
I'm forever trimming the darn thing. On my old boat, I'd adjust it once an hour or two, or once a day offshore. On this one, I can't seem to stop tweaking! All of a sudden, a quarter of a knot means something...
I'm looking forward to sailing on a reach or a close reach, to see how things go.
Cheers for now.
Paul.
__________________
If you can dream it; with grit, you can do it.
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31-10-2020, 15:19
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#34
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Registered User
Join Date: Oct 2011
Boat: KH 49x, Custom
Posts: 1,765
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Re: What boatspeed should I expect, as a percentage of True wind?
FXYKTY Yes, you're right, I meant backwind the jib. I should have proof read that post before posting...
Cheers.
Paul.
__________________
If you can dream it; with grit, you can do it.
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31-10-2020, 15:33
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#35
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Registered User
Join Date: Jan 2018
Boat: 50ft Custom Fast Catamaran
Posts: 12,231
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Re: What boatspeed should I expect, as a percentage of True wind?
Congratulations on the boards, Paul!!
This is a great thread to follow along with.
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31-10-2020, 15:37
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#36
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Registered User
Join Date: Apr 2016
Location: SE Asia, for now
Boat: Outremer 55L
Posts: 4,170
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What boatspeed should I expect, as a percentage of True wind?
Quote:
Originally Posted by GRIT
Thanks Brent.
The board tweaking might help, but where I really need help is on mainsail trimming. I heard flat tops are easy to trim, but I can't believe they're as easy as it seems. I'm sure I'm doing something wrong.
The tell tales are most often doing just what I want them to do. I'm going to try to get them to flip to leeward more often, as I read that the mainsail should possibly be trimmed a little tighter than what the tell tales show. Though, every time I try it, I lose speed.
I'm also having luck with a very tight leech, and the main far to leeward, in 12 knots or so.
I've got to pay more attention to the foot tension too. I know I can do better.
I'm forever trimming the darn thing. On my old boat, I'd adjust it once an hour or two, or once a day offshore. On this one, I can't seem to stop tweaking! All of a sudden, a quarter of a knot means something...
I'm looking forward to sailing on a reach or a close reach, to see how things go.
Cheers for now.
Paul.
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Is your sailmaker local? If so, ask them to come out with you and show you how to best trim the sail.
If you used a distant sailmaker, engage a local sailmaker on a per hour basis to show you the same thing. They may also trash the design and workmanship of the sailmaker you used.
The boards are simple:
- one or both going upwind to minimise leeway
- lift boards partially when powered up to prevent overloading
- lift leeward board completely in conditions where tripping could be an issue
- 1/3 or 1/2 board (windward) reaching or running if your autopilot has to work hard to prevent yawing
Upwind, you want the top horizontal batten (not the angled gaff batten) be parallel with the boom. Top telltale should be showing most of the time, but in lighter conditions it’s usually better to have it flowing all the time. Boom should be somewhere between parallel to the centreline and the sheeting angle of your jib/genoa, say 15-20 degrees down from the centreline. Experiment with combinations of sheet tension and boom position to find out what works best for your boat.
As you get overpowered, ease sheet to twist off the top batten, and/or ease the traveller to leeward.
As you bear away to a reach, ease the traveller to match the jib’s sheeting angle and ease the sheet just enough to continue mostly showing the top telltale. Another guide is to have the leeches match, but likely your jib will be twisted more than it should unless you’re barber hauling it.
Once you run out of traveller into a broad reach you can decide whether a boom downhaul is needed. We’ve never bothered and accept some extra twist.
With full battens, the outhaul is not doing much. Unless we have a long upwind leg, we set and forget it with a foot depth equal to that at the first batten.
Depending on your mainsail material, the cunningham is not much use. You will not be bending the mast, so there is no need to pull it on, assuming you have reasonable halyard tension to start with. Even with our tired HydraNet main, the maximum draft position is lock solid and doesn’t move around.
This Yachting World article is pretty good for the basics: https://www.yachtingworld.com/multih...amarans-127848
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31-10-2020, 17:25
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#37
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Registered User
Join Date: Oct 2011
Boat: KH 49x, Custom
Posts: 1,765
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Re: What boatspeed should I expect, as a percentage of True wind?
Quote:
Originally Posted by Chotu
Congratulations on the boards, Paul!!
This is a great thread to follow along with.
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Thanks, we're pretty chuffed!
Paul.
__________________
If you can dream it; with grit, you can do it.
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31-10-2020, 17:35
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#38
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Registered User
Join Date: Oct 2011
Boat: KH 49x, Custom
Posts: 1,765
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Re: What boatspeed should I expect, as a percentage of True wind?
Fxykty
Thanks for the pointers.
We've been experimenting with sail twist quite a lot, leaving the boom midships, or even slightly to windward, as per some of the suggestions on another thread. But we've also had luck doing as you say, and tightening the leech, so the top batten is parallel to the boom, and letting the boom go down the track. Both methods seem to work well, and with some experimentation, we'll figure out what works best in which winds.
Now, with boards, we'll have to relearn everything, as the boat sails like an entirely different animal. No complaints here.
I've recently made acquaintance with a fellow who's sailed quite a few fast cats, and is a professional in the field. I'll be having a nice chat with him in the near future.
Thanks again.
Paul.
__________________
If you can dream it; with grit, you can do it.
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01-11-2020, 05:30
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#39
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Registered User
Join Date: Jun 2016
Location: Brisbane Australia
Boat: Schionning Waterline 1480
Posts: 1,987
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Re: What boatspeed should I expect, as a percentage of True wind?
Quote:
Originally Posted by GRIT
Thanks Brent.
The board tweaking might help, but where I really need help is on mainsail trimming. I heard flat tops are easy to trim, but I can't believe they're as easy as it seems. I'm sure I'm doing something wrong.
The tell tales are most often doing just what I want them to do. I'm going to try to get them to flip to leeward more often, as I read that the mainsail should possibly be trimmed a little tighter than what the tell tales show. Though, every time I try it, I lose speed.
I'm also having luck with a very tight leech, and the main far to leeward, in 12 knots or so.
I've got to pay more attention to the foot tension too. I know I can do better.
I'm forever trimming the darn thing. On my old boat, I'd adjust it once an hour or two, or once a day offshore. On this one, I can't seem to stop tweaking! All of a sudden, a quarter of a knot means something...
I'm looking forward to sailing on a reach or a close reach, to see how things go.
Cheers for now.
Paul.
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If you draw a graph of lift and drag of a sail, as the sail produces more lift the drag is increasing at a different rate and at a point before peak lift, the drag increases rapidly and you will loose speed before you reach peak lift even though everything looks right. The peak motive force is when the windward luff tell tails start to lift.
It seems to be ok to have some seperation on the leach with tell tails ducking between streaming and flicking up the leeward side I think because any lift from this part of the sail is slowing forward travel. I have noticed that the amount is different on the two boats I have trimmed on. So it is probably different for all boats and just something you will work out.
__________________
Regards
Dave
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01-11-2020, 05:56
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#40
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Registered User
Join Date: Oct 2011
Boat: KH 49x, Custom
Posts: 1,765
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Re: What boatspeed should I expect, as a percentage of True wind?
Thanks for that Dave.
Do you have luff tell tales on your mainsail? It seems like a good idea, in truth. How far back from the mast are they?
Paul.
__________________
If you can dream it; with grit, you can do it.
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01-11-2020, 13:35
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#41
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Registered User
Join Date: Apr 2016
Location: SE Asia, for now
Boat: Outremer 55L
Posts: 4,170
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Re: What boatspeed should I expect, as a percentage of True wind?
Quote:
Originally Posted by GRIT
Thanks for that Dave.
Do you have luff tell tales on your mainsail? It seems like a good idea, in truth. How far back from the mast are they?
Paul.
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If your mast doesn’t rotate there’s not much point. In this case the telltales are placed about midway between luff and leach 1/2 and 3/4 of the way up.
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01-11-2020, 15:15
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#42
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Registered User
Join Date: Oct 2011
Boat: KH 49x, Custom
Posts: 1,765
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Re: What boatspeed should I expect, as a percentage of True wind?
Ok, that makes sense now. I wondered why I hadn't seen them before.
Thanks fxykty.
Paul.
__________________
If you can dream it; with grit, you can do it.
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07-11-2020, 02:28
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#43
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Moderator
Join Date: May 2014
Boat: Shuttleworth Advantage
Posts: 2,806
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Re: What boatspeed should I expect, as a percentage of True wind?
Quote:
Originally Posted by GRIT
Thanks for the screecher information, that's going to help me when I talk to my sailmaker this winter. I was thinking 80m2 for a gennaker and 55m2 for a closewinded screecher. It looks like I'll be increasing the size of each by at least 30%. It's nice to hear numbers from folks using their boats.
The close winded screecher, if sheeted ahead of the pilot house, comes to 55m2. If I can put it at the back of the pilot house (without damagine the solar panels), then I could get another 30% or so.
Cheers.
Paul.
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With regards to the screecher our mainsail is 63sqm and our screecher is 65sqm. It has a high cut clew to allow it to be sheeted to the jib tracks on the coachroof (11 degrees). This enables much tighter apparent wind angles to be achieved in very light winds. Once sheeted in it is important to play the mainsail out-haul to match the draft of the mainsail to that of the screecher. The reason I prefer a removable mainsail cover rather than a sail pack that hides the foot of the sail.
I have been on cats where the owners have never adjusted the out-haul since it left the factory, I've even been on cats where it was fixed. It is big sacrifice of furling booms. Ignoring the out-haul is a real performance killer.
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07-11-2020, 05:46
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#44
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Registered User
Join Date: Oct 2011
Boat: KH 49x, Custom
Posts: 1,765
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Re: What boatspeed should I expect, as a percentage of True wind?
Thanks for your comments Tupaia.
I agree, most cruisers never adjust the foot of the mainsail, and find it a chore. Some booms aren't really set up well, for access to the out-haul, so I guess I can understand that. We rarely touched the out-haul on or last two boats.
Fortunately, having a forward cockpit, and the out-haul coming out of the front of the boom, next to the reefing lines, it's no chore at all to fine tune the sail for light or heavy airs. We've been playing with it often, and are amazed how much difference in shape it can make. We can have a draft of what seems like 60cm and goes all the way to the leech, or down to somewhere around 20cm and ending midway to the leech. It's one of the first things we do after raising the mainsail, is to adjust the out-haul.
As an aside:
It's been brought to my attention that our 20 degree AWA is pretty tight for a cat, and was only on Stb tack. It's been suggested there's a possibility that the boat won't point to 20 degrees on Port tack, which would indicate the anemometer could be misaligned. I'll check on that on our next outing.
Thanks again for the trimming suggestions.
Paul.
__________________
If you can dream it; with grit, you can do it.
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13-11-2020, 09:13
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#45
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Registered User
Join Date: Oct 2011
Boat: KH 49x, Custom
Posts: 1,765
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Re: What boatspeed should I expect, as a percentage of True wind?
The daggerboards are working well. Just for fun, I tested the boat's tacking abilities. It's pretty slow, and not the best VMG, but I wanted to know what the minimum was, in light winds. It looks like just above 20 degrees awa. Making 33-50% of windspeed, and tacking through about 60 degrees (315-015). Pretty cool.
The steering gearbox has excessive backlash in the gears. We're planning to change them to helical, composite, gears, to reduce the backlash and noise.
The fan sound is the two espar heaters keeping the boat warm. We're still in the chesapeake, and travelled overnight to Deltaville. This was our arrival at around 7am.
Cheers.
Paul.
__________________
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