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

[GRIT]

I know there's a "how fast in light airs" thread ongoing, but it has drifted to posts about VMG, which isn't what I'm looking for.

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.

To start off, here's what we have, and a little information on how she sails, so far.

Some of you may know, we built (are still building) our boat, and launched last fall. We now have the boat rigged, as of July 10, 2020, and have about 1000 miles on her, without the dagger boards, as they're not yet functional.*

As near as we can tell, and since she was weighed twice, I'm sure we're close, she comes in at 8.5 tonnes (about 19,000lbs). That's more than my goal of 7 tonnes, but it'll have to do. She's fully loaded for cruising at that weight, with 750l of fuel and 400l of water, with spare parts and tools galore!

GRIT is 15m long (50 feet) and 7.6m wide (25 feet), has shaft driven props, and kick-up rudders. The bow beam is a carbon moulded beam, similar to what you'll see on Eric LeRouge Catamarans

She still points to 30 degrees, and makes 60% of true windspeed*between 40 to 70 degrees AWA; down to 3 knots of true wind, with just the main and jib.* Once we get to 90 degrees AWA (120 true wind angle) she drops to about 50% of windspeed.* We can get a little more than 50% with the spinnaker, and mainsail, but the spinnaker is just too small to make a big difference.* I really don't know what others get, but I'm impressed as is. (Coming from a heavy cruising monohull)

We don't have an overlapping genoa, which I think is slowing us down somewhat.* When we get the screecher, that'll round off our inventory, and get us some more speed in light winds.* We're aiming to sail at the true windspeed, below 10 knots.* I know Chris White Atlantic cats can do it, so that's my goal.

We rigged the boat with a Selden mast, a 75m2 (800 sq foot) square top mainsail, and a 37m2 (400 square foot) jib, which is about 101%, and not self tacking.* All sail controls are electric (Yeah, I know, but we wanted to try it, and now we have.)* So far, it's great.* My wife, who's pretty small, can raise the mainsail, tack, and control the mainsheet and track car, all at the push of a button, or pull of a joystick.* She's so pleased, she can't stop smiling.

I have no idea how well she'll sail when the boards are working, but I'm pretty impressed, even without boards. I'd guess we'll add a little speed since we'll convert some of the leeway to forward motion.

The following is unrelated, but in answer to questions asked by members:

The kickup rudders work great, we often anchor in less than 3 feet of water, and have already beached the boat once on a pebble beach, to install thru-hulls (watermaker and deck wash), and beached it twice on soft mud to get out of a heavy current which was keeping us up at night with all the bubbling water around the hulls.**

Fastest so far was 15 knots in 25 knots of wind, and fastest actual "passage" was down the coast of Nova Scotia starting in light winds, then across the bay of Fundy in 25 knots on the beam, running from Hurricane Teddy, where we had to slow the boat down for comfort due to the 15 foot seas.* 350 miles in 46 hours, or just above 7 knots average, and the first few hours shouldn't count.

We built Carbon dinghy davits, with electric captive winches.* It's the ultimate in laziness for pulling up the dinghy.* But, the splashing of the water on the bow of the dinghy, while tied to the boat, gives me migraines.* So we always pull the dinghy up when we're at the boat.* So it'll sometimes go up and down 4 times in a day.* That's where the electrics come in handy.

We have 720 ah of CALB lithium batteries, charged with 1100watts (soon to be 2000w) of solar. We have a backup alternator on one engine, which can only come on when we turn on a switch at the engine. It has a standard, built in regulator, and puts out 90 amps for a few minutes, then settles to around 60 amps. We don't use the engine for charging unless we have to, as engine noise isn't good for migraines either.

We have two espar Airtronic 4 heaters, and one Hydronic 5 for the hot water. The engines are naturally aspirated VW engines and put out 60hp, but we're overpropped (flex0fold) and they max out at 1900 rpm, which is about 30hp at 9.9 knots. It'll do, because 1900 rpm is a lot quieter than 3600 rpm. We're officially "derated" to 30hp, I'm good with it, and know all about what could happen to the cylinder walls.

We've been living aboard since we launched in September 2019, and sailing since mid July 2020, and are pretty happy with the boat so far.

We'll be hauling out this winter to finish the boards, and set the waterline to the second of the two waterline options. There's just too much stuff for the lighter optional waterline.

She's a light design, but well loaded for cruising. We've made our compromises, as we all do, and we're happy so far.

Now, back to sailing speed please. How does this boat sail, in your opinion? And, what can we do to go faster, in winds less than 15 knots. Any suggestions?

Thanks.
Paul.

PS. I don't know what all those stars are doing in the post. They aren't there on edit... Please ignore them.

[mrybas]

Hi Paul,
Crowther 150 47’ 12,000lb empty (probably cruising around 15,000)
We generally are doing 50-90% of wind speed from 5-20 knots of true wind depending on sea state and how fast we want to go! Under the right conditions (without a lot of junk onboard), the boat will sail at wind speed.
We generally average around 200mi per day.
The navionics screen shot is crossing the Delaware Bay the other day while heading South. Wind was 12-20 knots true, angle of 120-160 true.

I don’t really bother with the screecher as the profurl drum is a PITA and I need to iron out the kinks. Mostly use just the main and the jib, but use the asymmetrical spinnaker in when it’s light.

[Dave_S]

If you search for polar diagrams for boats with similar specs to yours you can see what you might expect. On this one the coloured lines are wind speed, the radial black lines are boat speed and the degrees are wind direction.

Handy if you can find one close.

You can make your own using MS XL, there are YouTube videos on it.

[GRIT]

Thank you both for your replies. Our specs are very similar to the Outremer 45. As I said before, our daggerboards are presently non-functional, but, I'm hoping to fix that next week. We've scheduled a haulout here in the Chesapeake bay, and we'll see what we can do to get things running properly. Then, perhaps, we can match those numbers (Outremer 45 polars).

Mrybas, those are fantastic numbers. I don't think I'll ever be that efficient with just our main and jib, but it's inspiring to know how fast you can sail. I hope we share an anchorage somewhere this fall, I'd love to pick your brain on "Cat stuff". We'll be keeping an eye out for you. Are you staying above Hatteras until Nov 1, or does your insurance care about that?

Does your jib overlap the main?

I'm guessing your hulls are skinnier than mine, we're 12.5:1

We are ordering a screecher this winter, so I'm hoping with everything working properly, we can reach windspeed, with the screecher.

Cheers.
Paul.

[GRIT]

Mrybas.

My wife just connected to your instagram account. WOW, that boat's amazing!
Congrats, you did a fine job on the refit.

Cheers.
Paul.

[GRIT]

Dave. I think you've posted the Outremer 4x polars. I assume that's just for the main and genoa right? They have a nice sized genoa at about 55m2.

Anyway, I was hoping for numbers like that, but my foresail is just too small. I'm hoping to beat the 4x in light air, as we're lighter, wider, longer, and will have similar sail area with the screecher/gennaker. I used the outremer 45 as a guide when specifying my sail areas. We're close enough in specs that I knew we'd be safe if I used similar sail areas. The 4x didn't exist when I made these decisions.

Grit compared to Outremer 45 (not 4x) specs.

Outremer main: 67m2, GRIT 75m2
Outremer jib: 39m2, GRIT 37m2
Outremer displacement: min 8.2 max 11.1, GRIT loaded now, 8.5 tonnes
Outremer beam: 23.3, GRIT 25 feet
Outremer length 48, GRIT 50
Outremer length to hull beam ratio ?, GRIT 12.5:1

As you can see, we're close enough that I think it was a good model for my sail area choices. The original plans called for nearly 40% less sail area, so I decided that wouldn't do at all.

Cheers, and thanks for your input.

Paul.

[Dave_S]

I would be surprised if you didn't make the numbers, I only have experience on two boats, my own and a Seawind 1250 so probably not the best to answer your questions but when I looked at the chart I thought they were slower than your boat would be.

P.S. I think it was the 5X and yes just jib and main.

[GRIT]

Hi Dave.

I notice you have a waterline 1480. Our very good friends, who's boat was the first Catamaran we ever sailed on, have a 1480. It's wicked fast. He regularly sails at windspeed, and beyond, and has seen 20 knots on many occasions. Of course, at something like 15:1 hull beam to length ratio, the water barely knows he's there.

Lovely boats.

Cheers.
Paul.

[Dave_S]

I love it but I don't use it anywhere near enough. We have always just been getting it ready for retirement which has been put back twice now, should have waited to buy it but all life would be easy with hindsight.

Wind speed +/- a bit happens quite easily, plus 2 or 3 knots happens sometimes when conditions are good. I'm sure we can do 20+ and maybe have without knowing it riding a wave but just under 19 is our fastest claim. I back off when I feel the boat is stressed or getting a bit light or if it is digging in.

12 to 15 knots is it's groove. No stress, just cruising.

To be honest, I don't really know what the sails are, I have a non flat top main on a taller 19.5m mast, a jib that would be around about 130% and a reacher that is big.

There is a big Schionning G Force here built super slick and light that makes 2x wind speed on a good day.

[barnakiel]

Best racing ones go faster than the wind speed but the cruising ones do not.


It all depends on what cat you have.


b.

[seandepagnier]

For perspective, my full keel monohull 27' did 50% of wind speed (100% wind speed with spinnaker on a reach) but was limited by 6 knots hull speed. I did a few 150 mile days on that boat which is not much slower than you going 175 miles in 24 hours.



Considering you don't have large headsail and you have more than a ton of gear it's not a surprise that the speed is not more. Better than most cruising catamarans, but you aren't doing 300 mile days either.



If you want to go faster you are going to have to get rid of some weight. Maybe you don't need so much water? I left on a 50 day passage with 20 liters (relying on catching rain along the way) I don't have engines or fuel which the amount you list seems extreme. The battery bank also seems large, how much does it weigh? It seems like you have enough battery capacity to motor the boat on electric for significant distance (at least 50 miles): you could save a lot of weight. Is your standing rigging synthetic?


It's going to be a trade off of speed vs how much weight you carry. Don't forget to fill the dagger boards with helium.

[GRIT]

Originally Posted by Dave_S

I love it but I don't use it anywhere near enough. We have always just been getting it ready for retirement which has been put back twice now, should have waited to buy it but all life would be easy with hindsight.

Wind speed +/- a bit happens quite easily, plus 2 or 3 knots happens sometimes when conditions are good. I'm sure we can do 20+ and maybe have without knowing it riding a wave but just under 19 is our fastest claim. I back off when I feel the boat is stressed or getting a bit light or if it is digging in.

12 to 15 knots is it's groove. No stress, just cruising.

To be honest, I don't really know what the sails are, I have a non flat top main on a taller 19.5m mast, a jib that would be around about 130% and a reacher that is big.

There is a big Schionning G Force here built super slick and light that makes 2x wind speed on a good day.

Yes, I think Schionning designs some of the fastest cats these days. I just love their looks too.

Speed is always a consideration, for me, as starting this thread shows. It's not the only consideration, but it's in the top three. How much more fun is it to sail at windspeed, rather than half of windspeed. So much distance can be covered in smooth water, rather than needing 15 knots of wind.

I think half my issue is that the foresail is just too small. A screecher will help there.

I do envy your sailing speeds.

Thanks so much for that information. Good luck retiring soon.

Cheers.
Paul.

[GRIT]

Originally Posted by seandepagnier

For perspective, my full keel monohull 27' did 50% of wind speed (100% wind speed with spinnaker on a reach) but was limited by 6 knots hull speed. I did a few 150 mile days on that boat which is not much slower than you going 175 miles in 24 hours.



Considering you don't have large headsail and you have more than a ton of gear it's not a surprise that the speed is not more. Better than most cruising catamarans, but you aren't doing 300 mile days either.



If you want to go faster you are going to have to get rid of some weight. Maybe you don't need so much water? I left on a 50 day passage with 20 liters (relying on catching rain along the way) I don't have engines or fuel which the amount you list seems extreme. The battery bank also seems large, how much does it weigh? It seems like you have enough battery capacity to motor the boat on electric for significant distance (at least 50 miles): you could save a lot of weight. Is your standing rigging synthetic?


It's going to be a trade off of speed vs how much weight you carry. Don't forget to fill the dagger boards with helium.

Thanks for your reply. I never would have considered it possible to sail a monohull at windspeed, whatever the wind. I've learned something today.

I appreciate your suggestion, regards weight, we certainly could lose a few pounds. But, the weight isn't going down, as we live aboard full time. We usually keep 200l of fuel, and 200l of water aboard, unless doing a longer passage, where safety dictates that we carry what we can. My wife prefers to have lots of fuel aboard, it doesn't matter why, just that she does; so we do. The fuel tanks are all integral to the hulls, so an empty tank is a very good buoyancy chamber, especially the aux tanks, which are in the bilges.

I think we'll see better numbers when we get the dagger boards down. It would be interesting if someone here with boards could lift them up for an hour to do a speed comparison, especially upwind. I'm hoping to see at least a knot in the difference.

The screecher/gennaker will add a fair bit of sail area, which should add a knot or two...

In any case. I hope to have working boards in a couple of weeks, as we're hauling out next week to see if we can fix this issue.

Cheers.
Paul.

[GRIT]

Thanks Barnakiel.

We're not a racing cat, but neither is Chris White's Atlantic series, and they are able to sail beyond the speed of the wind. Since our specs are very similar, we expect to do the same.

We've made some compromises, which added weight the build, but we're still on the light end of things, for cats of this size. So I really do expect to see speeds increase substantially, once we have things sorted.

Cheers.
Paul.

[fxykty]

Originally Posted by GRIT

Thanks for your reply. I never would have considered it possible to sail a monohull at windspeed, whatever the wind. I've learned something today.



I appreciate your suggestion, regards weight, we certainly could lose a few pounds. But, the weight isn't going down, as we live aboard full time. We usually keep 200l of fuel, and 200l of water aboard, unless doing a longer passage, where safety dictates that we carry what we can. My wife prefers to have lots of fuel aboard, it doesn't matter why, just that she does; so we do. The fuel tanks are all integral to the hulls, so an empty tank is a very good buoyancy chamber, especially the aux tanks, which are in the bilges.



I think we'll see better numbers when we get the dagger boards down. It would be interesting if someone here with boards could lift them up for an hour to do a speed comparison, especially upwind. I'm hoping to see at least a knot in the difference.



The screecher/gennaker will add a fair bit of sail area, which should add a knot or two...



In any case. I hope to have working boards in a couple of weeks, as we're hauling out next week to see if we can fix this issue.



Cheers.

Paul.

I haven’t noticed any speed difference boards up or boards down that could only be attributed to boards. The relative wetted surface (3.5 sqm per board, vs 25 sqm per hull) difference is pretty small.

Going upwind it’s leeway - two boards a couple of degrees less than with one board, until 9+ knots boat speed when no difference in leeway. With no boards then 4-5* more leeway. No speed difference.

Reaching or running we pull the boards up fully, except maybe a bit of windward board to steady the balance. But full boards down would matter only in light winds when we’re under powered.

We have a self tacking jib and the screecher is critical for lighter winds upwind. It’s worth a lot more than 1 or 2 knots.