[wsmurdoch]

Chris Parker forecasted 20 gusting 25 yesterday, so thought I'd try the riding sail here in Big Majors Spot in the Bahamas. I recorded the true and the apparent wind, both speed and direction. I also put a dynamometer on the anchor snubber to monitor the pull on the anchor. The riding sail was set on the backstay and sheeted to the port staysail lead block then back to a cabin top winch. The triangular sail is about 6'-6" along the backstay and 7'-6" on its foot. The water was almost calm in this protected spot.

Here are the recordings:

I put the riding sail up at about the 45 minute mark, had some trouble with the hoist until the 40 minute mark, then all was well.

The riding sail cut the swing in relation to the wind from +/- 30 degrees to +/- 15 degrees, and maybe half of that was due to the true wind variation.

The force on the anchor did not seem to change much, but I had to stand on the bow to read the dynamometer dial, and I quickly tired of doing that. The average force was perhaps 80 lbf and the maximum (the gauge has a tell tale) was 195 lbf.

Bill Murdoch
1988 PSC 34
Irish Eyes

 

[CaptTony]

Fascinating information. I take it things are a little slow where you are. : )

 

[wsmurdoch]

I take it things are a little slow where you are. : )

Actually, I've been quite busy today. Between long periods of taking in the view and resting, I swam down to look at the anchor, took a saltwater bath, read a little, had a beer... That sort of stuff. Right now I'm waiting for 5 o'clock to have a G&T.

Slow best describes the group that just flew in and out in a Cessna 208 (a ten seater) on floats. They taxied over to the beach and spent a half hour feeding the pigs. I'm from East Tennessee. If you go to that much trouble and expense just to feed pigs, you're really having a slow day.

Got to run.

Bill Murdoch

 

[CaptTony]

Darn. I wish I was that busy.

 

[johnharch]

Very interesting. It looks like your riding sail is fairly effective in dampening the swing. I've thought about rigging one, but never came up with a good plan. Can you give any more information about its construction and deployment? How is attached to the back stay? Does the foot run parallel with the deck? What material did you use for the sail cloth? What would you do to improve it?

When I anchor in 20 knots, I swing all over the place.

John
PSC 34, '91

 

[Bene505]

This past summer, I made a "block" part way up the backstay using a piece of rope and a knot similar to a prussic knot. The line that tightened it had a loop in it. I slid it up into position using 2 dock poles taped together for extra reach. I had it pre-strung with a halyard before doing so.

That setup worked really well. We have a cleat on the backstay 12" above head level, so that served to secure the halyard at the bottom. the halyard was tied into a big loop, so there was no way it could get unthreaded from the top loop.

When not in use, we kept the riding sail connected, but rolled-up and lashed to the backstay.

To raise, run the riding sail's "sheet" loosely to the winch on the mast. Un-lash the sail from the backstay. Loosen the halyard on the cleat, raise the halyard. Cleat firmly in place. Then tighten the "sheet" on the winch on the mast.

Regards,
Brad

 

[wsmurdoch]

Here is a photo.

The sail is tacked to the stern rail with two short pieces of 3/8" line; one to the top of the stern rail to port and one to the outboard motor bracket on the rail to starboard. It is hoisted on the main halyard. The clew sheet is run forward to the staysail lead block then back to the port side cabin top winch. There are two jib hanks on the sail; one at the head and one at the tack. They are clipped to the backstay. Tacking the sail to the stern rail solves some interference problems with the HF antenna lead-in wire and its standoffs that run along the lower part of the backstay and takes some load off the backstay.

I bought the sail new from a Florida sailmaker on ebay. It was cheaper than I could buy the cloth. It is triple stitched zigzag, taped on all three edges, reinforced at all three corners, and with webbing loops at all three corners.

The real hero here is the software that does the graphing. It allows objective evaluation of the sail's performance. It's NavMonPC by Paul Elliott and Dirk Lison.

Bill Murdoch
1988 PSC 34
Irish Eyes

 

[johnharch]

Great, thanks Bill. The picture tells it all. Now I can add one more item to my ever expanding project list.

 

[svHyLyte]

For what it's worth, we have found the Banner Bay Fin Delta to be a great improvement over a traditional flat riding sail.

 

[Group9]

For what it's worth, we have found the Banner Bay Fin Delta to be a great improvement over a traditional flat riding sail.

I've got one of those, too. But, I haven't got it out of the box yet. I'm looking forward to seeing how much it stops my boat from tacking at anchor.

 

[ccriders]

WSM,
Looks like a comparison test in the making.
How about it? Maybe one if the Fin Delta owners could supply you with one.
Happy sails
John

 

[Bene505]

We use a regular flat sail. Toward the end of the summer, we ran the sheet for it forward to the midships cleat. That kept it angled to the wind and applying "straightening force" when the bow is into the wind so the hulls is providing no "straightening force". It minimized the "tiny tacking" of the anchor sail that occurs otherwise.

Net effect is likely similar to using a V sail.

Regards,
Brad

 

[wsmurdoch]

WSM,
Looks like a comparison test in the making.
How about it? Maybe one if the Fin Delta owners could supply you with one.
Happy sails
John

I'll leave the testing and comparing different riding sails to Practical Sailor. Actually, I don't know how it could be done. I have been using this one for three years and have been watching others use their riding sails for longer than that. Here are some thoughts:

What is the 'measure of merit'? What is "better"? I chose to visually compare graphs of the variations in the apparent and true wind with and without the riding sail hoisted. Others might be interested in heading variation, changes in boat GPS coordinates, chart plotter tracks, or something else.

How much weight should be given to any increase in anchor load? I know that when I hang my sun awning vertically behind my bimini to shade the cockpit in the evenings, the swinging of the boat diminishes, but no doubt the anchor load also increases. After all, the awning is just a square sail pulling the stern of the boat downwind. I imagine that, compared to a flat sail, a dihedral sail has some increase in average anchor load. Is that important?

What about cost and simplicity? How much do they matter?

What about the boat? I have a 34' Pacific Seacraft with a canoe stern. The backstay comes down at the pointy stern of the boat and there are no easy spots to tack down the two corners of a dihedral sail. Other boats like the Beneteau/Jeanneaus with their wide sterns or boats with huge stern arches have perfect places for attaching the two tacks of a dihedral sail.

How much does the boat swing on its own? Those same Beneteau/Jeanneaus with their masts set forward move around a lot. Some of the catamarans anchored with a wide bridle don't seem to move at all. Obviously, not all boats act the same without a riding sail. Perhaps the same is true of boats with a riding sail.

What about the effect of current? Many times, we find ourselves anchored with the anchor chain leading off to one side of the boat or on occasion even back under us. It never looks like that in drawings in books or magazines, but it happens. Sometimes instead of just swinging back and forth, we go in circles. Other times we just fly like a kite off to one side of the anchor. How does the riding sail effect the boat when there is a current flowing?

How much wind should be blowing and how rough should the water be while the riding sails are being tested and compared? I know from my own experience in wind to 30 kt and waves to 2' that it does make a difference in both the anchor load and in the boat behavior. A gusty wind is different from steady wind, and wind that swings back and forth is different from wind that blows from a constant direction. When strong winds are forecast, we shelter behind land. That is a guarantee of gusty, shifty wind.

Anyway, if you want me to test a dihedral sail, box it carefully padding it with wadded up $100 bills and have it sent via Watermakers Air of Ft Lauderdale to me c/o Staniel Cay Yacht Club. I'll get right on it.

Bill Murdoch
1988 PSC 34
Irish Eyes

 

[ccriders]

Well then, let's go back to anchor testing.
Thanks,
John

 

[BirdBrain333]

Dear Bill,

It is wonderful to get some real data on this topic. It comes at a good time for me as I was just now reading an article on the Morgans Cloud website in which a writer documents his various "solutions" to the problem of sailing about at anchor. His latest iteration is a small drogue (18" mouth reinforced with wire) fastened onto the anchor chain just about where their 30' snubber attaches -- so that the drogue stays in the water when the chain is pulled tight in strong winds. He says it almost totally eliminated sailing around. Worth a read and worthwhile subscribing for lots of great articles on and by knowledgable bluewater cruisers.

I think I may do both!

Jay
PSC 37 Kenlanu

 

[Bene505]

...Bill Murdoch
1988 PSC 34
Irish Eyes

Bill,

Happy St. Patricks Day!

Regards,
Brad

 

[HankOnthewater]

Bill (WSMurdoch), what meter do you use?
I am interested in that kind of stuff, and logging the data on a PC/laptop will show real values
thanks
hank

 

[wsmurdoch]

The anchor load was measured with a 0-2000 lbf dial dynamometer. I bought it on ebay. Both the seller and I mispelled dynamometer. I was the only bidder and got a real deal.

The instrument data was taken from the boat's Simrad instruments. The IS-15 display heads have a NMEA 0183 output which carries on two wires all the data that can be displayed on any of the heads (depth, speed, heading, wind, position, COG, SOG...). That data stream is converted to USB with a RS-232 to USB adapter. The USB signal from that source is combined with signals from several others in a USB hub before going to a small cheap notebook PC. NavMonPC software decodes that and produces the graphs that I included in the original post. NavMonPC does two other things that I find useful. It will sample the data stream at any frequency I specify and produce an Excel file for later analysis. It also will produce virtual serial serial ports on the PC which can be used by other programs to access the data stream.

Bill Murdoch
1988 PSC 34
Irish Eyes

 

[mbianka]

Dear Bill,

It is wonderful to get some real data on this topic. It comes at a good time for me as I was just now reading an article on the Morgans Cloud website in which a writer documents his various "solutions" to the problem of sailing about at anchor. His latest iteration is a small drogue (18" mouth reinforced with wire) fastened onto the anchor chain just about where their 30' snubber attaches -- so that the drogue stays in the water when the chain is pulled tight in strong winds. He says it almost totally eliminated sailing around. Worth a read and worthwhile subscribing for lots of great articles on and by knowledgable bluewater cruisers.

I think I may do both!

Jay
PSC 37 Kenlanu

I've used an anti-sail drogue from the bow for a number of years.
THE BIANKA LOG BLOG: LESSONS FROM A HURRICANE: AN ANTI SAIL DROGUE
It works very well and is easy to deploy. I just drop it down from the bow anchor roller. Though making a Riding Sail is on my list of projects too. But, I'm happy with the drogue.

 

[mondofromredondo]

Not really sure how my experience relates to this conversation but I added weather sheets to the cockpit of boat.

These weather sheets of course provide a similar windage as a small sail would. Simply located closer to waterline. I've noticed that the boat when anchored now squares up to the wind much nicer.
Not having to deal with an additional sail. Obviously with alot of current this may not be adequate to point the boat into the wind but for the most part one less thing to deal with after dropping the hook.

On one ocassion with light winds I raised my triple reefed main which worked great !!