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

[GRIT]

Thanks so much for that info Fxykty. I really have no idea what to expect. I thought some of the leeway, without boards, would translate into extra speed with the boards down. Perhaps due to cross flow across the hulls, or whatever my imagination was inventing. Now I know it won't.

How large is your screecher, and how close to the wind would you normally sail with it deployed?

I'm debating as to where to sheet it. I can sheet it ahead of the pilothouse, and have 55m2, or I could sheet it to the back of the boat, and have more like 80m2 of sail. Or, I could get both sizes, one for close winded work, and one for a little more off the wind...

Lastly, as a rough guess, how much extra speed would you normally expect from your screecher.

Thanks very much for your reply.
Paul.

[Dave_S]

It does seem like a lot of fuel and water. You can reduce the water weight by carrying a watermaker. If you need the fuel then I guess you need it.

[Sparx]

GRIT,

My Maine Cat 38 has a very powerful flat top main sail and a small fractional jib. With dagger boards up the big main sail tends to pivot the bow up into the wind and the boat is moving cross wise through the water on a course lower than the heading. This can happen both upwind and broad reaching. Dropping some dagger board straightens the boat out which gives both less leeway and also reduces friction delivering higher speed through the water.

When you get the dagger boards fitted play with them while comparing the course of your wake to the boat heading. I expect you will see some speed increase both upwind and downwind when using your dagger boards. I find that small amounts of dagger board are all that is needed in many cases. Also watch the impact of dagger boards on rudder angle.

I am looking forward to hearing of your findings.

[GRIT]

Originally Posted by Dave_S

It does seem like a lot of fuel and water. You can reduce the water weight by carrying a watermaker. If you need the fuel then I guess you need it.

It is a lot of fuel, no doubt. But my wife insisted we have enough tankage for 1500 miles, so that's what we have, more or less. We usually have less than 200l aboard, except when it gets cold, we run the furnace more often, so carry more fuel. The water is similar, in that we carry 200l or less, but for offshore we fill them both up. We have a watermaker, and run it often... but showers, and freshwater toilets consume more than I'd have thought. Anyway, happy wife, happy life!

Cheers.
Paul.

[fxykty]

Originally Posted by GRIT

Thanks so much for that info Fxykty. I really have no idea what to expect. I thought some of the leeway, without boards, would translate into extra speed with the boards down. Perhaps due to cross flow across the hulls, or whatever my imagination was inventing. Now I know it won't.



How large is your screecher, and how close to the wind would you normally sail with it deployed?



I'm debating as to where to sheet it. I can sheet it ahead of the pilothouse, and have 55m2, or I could sheet it to the back of the boat, and have more like 80m2 of sail. Or, I could get both sizes, one for close winded work, and one for a little more off the wind...



Lastly, as a rough guess, how much extra speed would you normally expect from your screecher.



Thanks very much for your reply.

Paul.

We have a large 120m2 screecher that sheets outside the cap shroud to the stern running backstay chainplate. It overlaps the shroud by about 3m when fully sheeted. It’s only good to about 40* AWA but with the 120% TWS boat speed it generates that’s a TWA of about 80*, not too good upwind. Slightly better in really light air (<5 knots TWS) where our speed isn’t so much and TWA improves slightly. This size sail is better for reaching and too fast for upwind with the wider sheeting angle. We take it down at 15 knots AWS.

I’m getting new sail quotes for an upwind screecher that will sheet inside the shroud and sheet to the aft end of the cabin top, where our sisterships that have overlapping genoas have their genoa sheet winch. The designed size is 75m2 (genoa is 55m2) and with the sheeting angle should provide for a 25-26* AWA. Boat speed will be slowed to 90-100% TWS and 50* TWA. A lot better for upwind in light winds as it’s bigger than the stock genoa. It will also do well for moderate and stronger wind reaching and running and we can transition to sheeting outboard.

We’re fine upwind with the 95% self tacking jib in 8+ knots - 80-85% TWS upwind. Slower at the crossover but VMG increases quickly with stronger wind.

Regarding skidding sideways, that pays when going 80-100* AWA but you really want to go 10-20* further to leeward. I’m not sure the boat speed is faster, but the increased leeway allows a faster angle and still go deep. That’s a passive benefit. Aggressive steering to take the apparent wind speed down, then heading up when it bleeds away, then steering again, plus playing waves, is more fun but takes active steering.

Boards are not complicated; I don’t know why people write that.

- Upwind - in lighter conditions one or two boards down. In heavier conditions rougher water windward board down only
- Every other wind angle - no boards
- In rough conditions any wind angle - half of a windward board down

[GRIT]

Thanks Brent.

I certainly do have a lot of leeway, and I was hoping to convert some of that to forward motion, with boards functioning properly. I will certainly have a report for the group, when we get them set up properly. My rudders, at lower speeds, are slowing the boat down somewhat as the angles are exagerated, especially when making adjustments. There's probably an extra 5 or 10 degrees of rudder in cross seas, or lighter winds on the beam and forward.

Cheers.
Paul.

[fxykty]

Originally Posted by GRIT

Thanks Brent.



I certainly do have a lot of leeway, and I was hoping to convert some of that to forward motion, with boards functioning properly. I will certainly have a report for the group, when we get them set up properly. My rudders, at lower speeds, are slowing the boat down somewhat as the angles are exagerated, especially when making adjustments. There's probably an extra 5 or 10 degrees of rudder in cross seas, or lighter winds on the beam and forward.



Cheers.

Paul.

We find a third or half board down when not upwind to really help the hulls to track, especially in cross seas.

[GRIT]

I'm not sure what happened to my reply, fxykty. I'll try an abbreviated version.

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.

I guess that makes sense anyway; now that I've been sailing for a couple of months, I've decided that I really should have maxed out the mainsail size. We'll do that on our next one. I believe my sailmaker said that I could get up to 85m2 for the mainsail. So we'll do that, and probably max out the rest of the sails too. 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.

The gennaker was always planned to go to the running back chainplates, as you've done on yours. I don't know how big that makes it, but it should be at least 80m2.

Cheers.
Paul.

[mrybas]

Originally Posted by 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.

Hi Paul,
We went around Hatteras yesterday and currently anchored at Cape Lookout. We’ll hang here for a week, then down to Folly Beach, SC.

I don’t know the official fineness ratio of the hulls, but a quick estimate from inside the boat is 13.25:1

I’d love to checkout Grit in person. Im very impressed with anyone that has the determination to build a boat from scratch! Is that how you got the boat name?

[GRIT]

Mrybas.

Thanks for your estimate of your "fineness" ratio, or Length to beam ratio.
It helps me to get a feel for what I can expect from ours. (Hint: it's not 17 knots in 21 knots of wind! )

I hope you had a nice trip, and arrived before the southerlies! I'll be going that way in late November. I'm getting ready to haul the boat on Monday, and get those boards down!

I'll be happy to trade you "boat tours" when I see you.

I just had a nice conversation with the owner of an Outremer 55l, about his single handed Atlantic crossing. Those boats amaze me too.

Yes, we named the boat GRIT because we think it's one of the most important qualities one can possess, to accomplish difficult tasks. For my wife and I, GRIT is a sort of cheer, we say it to each other when times are tough, or when we are feeling emotionally drained. Sort of like that old saying about winners never quit, and quitters never win. But much more abbreviated!

Cheers.
Paul.

[GRIT]

Just a quick update for those who might be interested.

The dagger boards are now available for use.

We launched yesterday morning, and sailed 30 miles today. According to the chartplotter, we had .7 knots against us, but I'm having a hard time believing that, judging by the speeds we were getting. So I'm only going to talk about Speed over Ground, True wind speed, and Apparent Wind angle.

First off. We'd never felt the boat "dig in" before. We had a gust, and actually felt the boat heel. Ok, so it was just a couple of degrees, but that had never happened before. No surprise to those of you who've never been "board handicapped", but it surprised us!

We don't have the downhaul and uphaul set up yet, so we put the boards down 1.5m (we can go down 2m) below the "keel". 1.5m is roughly where the boards reach neutral buoyancy; they're 4m long overall.

We're sailing faster by at least 10% and often closer to 20%, going upwind.

It's only been 30 miles, but we did get wind from 20 degrees to 180 degrees on this trip, so it's a good start. This is only a preliminary analysis, but it sure looks good.

From 180 to about 140 degrees AWA, we're about 50-55% of windspeed (No change). The last 12 miles were at 160-180, so we furled the jib, and still easily made 50% of windspeed on the mainsail alone.

From 60-90 AWA we made between 66 and 75% of true windspeed.
From 30 to 60 AWA, we made between 60% and 70% of true windspeed.
From 25-30 AWA, we made between 50 and 55% of true windspeed.
At 20 degrees AWA we made about 30-45% of windspeed.

Windspeed was between 5 and 15 knots, and quite variable in speed and direction. And, according to the chartplotter, we were against a current of about .7 knots. If that .7 knots is accurate, then all those numbers go up between 8 and 10%, which will really impress me.

I'll be watching things closely, and then build a set of polars, as soon as I learn how to do that.

That's it for now.

Cheers.
Paul.

[seandepagnier]

When I put my dagger board down, I am able to fall off and change my compass heading while still maintaining the same course over ground. So this translates into more speed. I also need the dagger board to efficiently tack in 80ft wide channels. Without it, I would make a lot of tacks.

When broad reaching in 6 knots of wind, if the main blankets the jib I am only going 3 knots. If I head up to fill the 180% head sail (sheets all the way to the aft wing) the boat speeds up to 6 knots, then I can fall off and maintain the same course as before at this speed, but in a lull if the boat slows down, the apparent wind shifts back and it's stuck again at 3 knots and I can repeat this maneuver to power up again.



So using autopilot on compass course, I need to make pypilot smarter to do this! Or use autopilot in wind mode, but this won't follow the route... So plenty to keep me busy trying to improve things.



As for full keel mono hulls going the wind speed: This is rare, but I did have a huge spinnaker that went from top of mast and was difficult to keep out of the water (3x the area of main sail) as well as full main, and apparent wind on the beam in 3 knots of wind (which means no wave drag since hull speed was 6.5) a very clean bottom (huge difference there) and flat seas. So in this case I could achieve 3-3.5 knots in 3 knots of wind but it is a special case and not something I could do all the time.



With the trimaran it goes wind speed in a much wider range of conditions, and even goes 7 knots in 7 knots of wind on a reach. I haven't even tried the spinnaker yet. This is also a racing trimaran and at 33ft long it can carry a lot less than a 27ft monohull, but most of that crap I didn't need anyway, and I do have 10 sails which is a bit heavy, so I'm trying to figure out which ones to get rid of.


Also realized yesterday I had 20 gallons of water in 2 tanks both forward that were full!! No wonder the boat was so bow heavy. I pumped that out, at least the tanks act as watertight bulkheads if I can keep them dry. I would never need to carry that much water (I sailed vanuatu to philippines and left with 5 gallons and arrived with 10 took lots of showers along the way too)


Also have not replaced the rigging with synthetic yet and many other ways to improve speed possible. My friends trimaran would go 1.5x the wind speed fairly easily but he also had a carbon mast that could rotate and all spectra rigging and spectra sails. I think his boat cost him more than 3k though.

[GRIT]

Ah yes, tacking.

Without the boards, we had to backwind the main to get the boat to tack, even then, she'd get stuck in irons about 50% of the time, especially in heavier winds.

We didn't need to tack today, but since we wanted to see if she'd go through the wind, we made a circle, and the boat went through the wind without issue. She turns much more sharply now. We didn't realize how sluggish the boat was to turn, until we got the boards working. Much better.

Cheers.
Paul.

[fxykty]

Originally Posted by GRIT

Ah yes, tacking.

Without the boards, we had to backwind the main to get the boat to tack, even then, she'd get stuck in irons about 50% of the time, especially in heavier winds.

We didn't need to tack today, but since we wanted to see if she'd go through the wind, we made a circle, and the boat went through the wind without issue. She turns much more sharply now. We didn't realize how sluggish the boat was to turn, until we got the boards working. Much better.

Cheers.
Paul.

Backwind the main??? Do you mean backwind the jib? Backwinding the main is a good way to stop your boat and sail backwards - that is an escape if you are stuck in irons (remember to turn the rudders the opposite way to the tack). Backwinding the jib will help the bows come around.

Regarding tacking with board or boards down, you will find that you don’t have to turn the rudders as far and can carve around the turn. Start with say 10 degrees of rudder angle, increase through the middle, then straighten out a few degrees low, ease the jib a touch, and use the extra power to accelerate up to speed. Easing a bit of mainsheet once the boat is through the eye of the wind also provides a bit more power, unless you have a square top. In that case, bring the main sheet on a bit instead. Once you’re back up to upwind speed, come up to your upwind angle and trim both sails to suit.

Basically the boards keep your boat from skidding around the turn, so the boat’s power is better utilised in the forward vector.

Since you built the boards and cases yourself (is that right?), presumably you know the loadings with boards fully down, half down, etc? It’s a combination of boat speed and wind speed, but basically once your boat speed goes faster than nominal hull speed upwind, or you are near maximum power right before reefing, your boards are fully loaded. Any faster boat speed or more wind speed, you need to lift the boards(s) to prevent over loading the boards and their cases.

In our case boards fully deployed have their tops 0.9m below deck level and protrude 1.7m below the hulls. We lift the tops to deck level when fully powered up and have about half a board down. That’s plenty at 8-9 knots boat speed.

[Sparx]

Our experience is similar to what Fxykty describes. We use maybe 2 feet of board below the boat when powered up. The full 6 foot of board below the hull is reserved for light to moderate winds.

The boat is often fastest with some board down on all points of sail...more board when close hauled. Off the wind just a bit of board is all that is needed.

When do you use both boards down? For us it is a rare condition of light to moderate wind in a confused sea. I dont think i have fully explored this issue. I do use just a little of both boards to help turn the boat when motoring in close quarters. I also use both boards down to rudder depth when exploring shallow water.

When do you use the windward board versus the leeward? Sometimes it seems windward is best and sometimes leeward board is preferred.