Garmin GWind use?

[kbowen]

This device (GND 10) is good at showing me a bunch of data that is just one step short of what I hope for: I want to learn how to achieve the best VMG, (velocity made good) on my boat which is to say best upwind performance. It already computes the difference between real wind speed and apparent wind speed, real angle and apparent angle, GPS speed and course, but the next step would be simply "how well am I getting upwind?" I am not trying to win any races here, I am hoping to use the gizmo to learn how to sail the boat better. This is a centerboard gaff ketch, she seems happiest about 60 degrees off the wind, but would it be better to pinch it a bit higher? What is the best depth for the centerboard considering drag vs leeway? I have two "slots" with three sails, and how should I best trim those? Can anyone help me wring more information out of this device?

Ken

DSC_0026-001.jpg

[Zane Lewis]

Re: Garmin GWind use?

Can't help you much but if you are only getting 60 deg off the wind in flat water conditions I would say you have a huge opportunity for improvement.
Probably start by looking at your sail settings, Tensions on the yards and hoists etc. followed by sheeting position, and tension to control gaff sag.
Just looking at that picture your jib looks under sheeted as the top 2/3 is flapping, The main looks very full. Looking at the angle of the mizzen gaff compared to the Main gaff it looks under sheeted.
Next thing to look at is the shape and hydro shaping of the centre board and rudder. Plus play with mast rake and sail trim to get COF sail balance lined up with the centreboard and rudder balance.

It may be worth getting an experienced sailing mate out for an afternoon and work together on trim.
Z

[Ben Fuller]

Re: Garmin GWind use?

I start these by sheeting the mizzen as hard as I can, then the main so it doesn't backwind the mizzen, then the jib. Check the headstay tension. These traditional rigs will never get to the 45 or narrower of a tall marconi sloop, and for some i'm happy with 60. A foilshaped CB makes a huge difference.

Unless your device has some way of intergrating the various inputs into a VMG which the fancy ones do, you'll not be able to wring more data from what you have. The next step is some kind of race software.

[kbowen]

Re: Garmin GWind use?

I start these by sheeting the mizzen as hard as I can, then the main so it doesn't backwind the mizzen, then the jib. Check the headstay tension. These traditional rigs will never get to the 45 or narrower of a tall marconi sloop, and for some i'm happy with 60. A foilshaped CB makes a huge difference.

Unless your device has some way of intergrating the various inputs into a VMG which the fancy ones do, you'll not be able to wring more data from what you have. The next step is some kind of race software.

Despite costing $600, this wind gizmo seems to be a bastard child at Garmin: The only manual I can find is for installation, not for use or options. (grrr)

Both jib and mizzen are used sails and neither is pristine. The mizzen has always seemed too flat, so when I rigged a couple weeks ago I took some advice I had read and split the Port / Stb'd Topping lift / lazy jacks. So now I can lift the boom a bit with the windward line to get more draft when the wind is light, this seems to help, but I wish I could get clear data on it.

The jib is set flying and becomes the headstay under tension, perhaps I was careless in choosing the photo I did, that was casual beer sailing. One of my totally unexpected problems is that I can't see the jib at all from the helm, I have to lash the tiller and go up there to take a look, or to adjust the trim. I have tried rigging the jib with the jib-boom shown, or with separate sheets, but I don't yet understand what that is doing.

I only built the CB trunk 2" wide, but the board is shaped as best I could within that limit; fattest part in the first third. Historically builders of these type boats used flat boiler-plate.

I have arranged a meeting / short sail with a local sailmaker for this coming Wednesday and am trying to understand my instruments and prepare my questions beforehand.

I am interested in further thoughts from all...

Ken

[John Meachen]

Re: Garmin GWind use?

I don't know the instrument but would suggest you wait for a day with a steady wind.Find a buoy at the windward end of your sailing zone and set it as a waypoint/landmark.Go downwind and select the buoy and using the advice in post #3 sail upwind.Try to maximise the VMG reading and it may greatly help your quest if the jib sheets are marked to aid repeatable sheet position.Marking the other sheets may also help.Does the boat have any possibility for altering the lateral position of the jib sheet lead?The point about an efficient centreboard shape in posts 2 and 3 is absolutely crucial to good windward performance.

[Ben Fuller]

Re: Garmin GWind use?

Despite costing $600, this wind gizmo seems to be a bastard child at Garmin: The only manual I can find is for installation, not for use or options. (grrr)

Both jib and mizzen are used sails and neither is pristine. The mizzen has always seemed too flat, so when I rigged a couple weeks ago I took some advice I had read and split the Port / Stb'd Topping lift / lazy jacks. So now I can lift the boom a bit with the windward line to get more draft when the wind is light, this seems to help, but I wish I could get clear data on it.

The jib is set flying and becomes the headstay under tension, perhaps I was careless in choosing the photo I did, that was casual beer sailing. One of my totally unexpected problems is that I can't see the jib at all from the helm, I have to lash the tiller and go up there to take a look, or to adjust the trim. I have tried rigging the jib with the jib-boom shown, or with separate sheets, but I don't yet understand what that is doing.

I only built the CB trunk 2" wide, but the board is shaped as best I could within that limit; fattest part in the first third. Historically builders of these type boats used flat boiler-plate.

I have arranged a meeting / short sail with a local sailmaker for this coming Wednesday and am trying to understand my instruments and prepare my questions beforehand.

I am interested in further thoughts from all...

Ken

A jib set flying needs a different cut from one supported by rigging, namely some hollow on the luff. Interested to see what the sail maker says. These rigs are quite different from the norm. Assume you have tell tales on the jib and main. If not the sailmaker will tell you to get some.

[kbowen]

Re: Garmin GWind use?

I don't know the instrument but would suggest you wait for a day with a steady wind.Find a buoy at the windward end of your sailing zone and set it as a waypoint/landmark.Go downwind and select the buoy and using the advice in post #3 sail upwind.Try to maximise the VMG reading and it may greatly help your quest if the jib sheets are marked to aid repeatable sheet position.Marking the other sheets may also help.Does the boat have any possibility for altering the lateral position of the jib sheet lead?The point about an efficient centreboard shape in posts 2 and 3 is absolutely crucial to good windward performance.

"Steady Wind" is not an item I often find here, the last couple days it has whacked around 180 degrees and all else inbetween morning and afternoon. We also have mountains and the wind fluctuates around them depending on where one is on the bay, Still I understand your process and have tried it on another boat, and will do so again on this one if I can't find another option..

Yes, your point is well taken about marking sheet leads, but I have been perhaps careless in how far I hoist and downhaul each sail as none of the tack positions are fixed. To avoid heaps of halyard around my feet, my peak and throat halyards are each single part which i hoist and set and then have a downhaul tackle on the tack to set luff tension. So perhaps I need to mark the spars at the gaff yoke for a consistent hoist location?

About "lateral position of the jib sheet:" Yes, there is a raised wooden rail all around the boat and I can put a snatch-block anywhere on that. However when I single-hand this boat I have a lot of "strings" to deal with and tend to set the self-tending jib boom when alone. I have boxes of salvaged hardware, and can put in a pad-eye wherever it might help.

The photos don't show it, but when beating to windward, the Mainsail (some would say foresail) is about 1 1/2" outboard of the lee mizzen shrouds.

Re: centerboard shape, this is not a daggerboard, it is a centerboard that pivots at the lower forward end, so when lowered it is pie-shaped underwater, 6 feet from the thin forward end, to the arc shaped after end, about 30" immersed below the bottom of the boat. There is no physical way I can see to get it close to a NACA foil or whatever, it will always be too thin for it's fore / aft length. Am I missing something??

Ken

[John Meachen]

Re: Garmin GWind use?

I think you may have highlighted the problem.The jib does not "have" to be led to the rail of the boat does it?It may be convenient or even conventional for some boats,but it dictates the angle of the boat relative to the apparent wind.Here are a couple of examples of how far inboard a jib can be sheeted.






You will, naturally enough, notice that the mainsails are also sheeted much nearer the centreline than your boomless foresail will allow.Which for practical purposes is the limiting factor and all you can do is bring the jib sheet leads as far inboard as backwinding the foresail will allow.The other thing that aids consistency is marking the actual jib sheets so that a reference point is present and ideally situated close to a shroud or fairlead.Some measure of calibration is always helpful so that you can repeat settings that work.The sails can generate the drive,but it's the underwater elements that determine the leeway.I have used NACA sections down to 6% thickness to chord ratio but the training edge can be a bit fragile.A rectangular slab of wood with little effort to relieve the edges is nothing like as efficient.

[kbowen]

Re: Garmin GWind use?

Much of my interest in this thread is history or archaeology, I am trying to use whatever I can from instruments and/or this forum to learn what the guys in the 1800's never wrote down: somehow fishermen on the Great Lakes used boats shaped like this to get out to their nets or long-lines despite winds of every strength and direction. If they left the nets out more than two days the catch didn't fetch a good price, or became worthless. Their sails were most likely cotton, spars were debarked trees, many of the old photos show no stays on the mast at all, some of the boats had no centerboard, or a flat iron boiler plate. (no NACA!!) So what did they do? Did they live with tacking thru 130 degrees? Or more? They clearly knew some tricks I haven't learned yet, and who knows what they were??

In the historic boats with no stays, clearly there was no restriction to how far they could haul the sails in: so were cotton sails stable enough to work well when that close hauled?

My boat sometimes grows more into her name, "Saga"

Ken