size of anchor sail for a 25?

Ray Bowles · Apr 16, 2013

I can not advise exact measurements on the size of your sail but I can give you a starting point. Your Mac 25 is a light boat and you are probably using a line rode rather than chain. I would think you are using a delta style anchor in the neighborhood of 10 to 12 lbs. All this is based on the Hunter 26, Catalina 22 and San Juan 23 that I have owned and anchored on many, many times.
Because of the weight factor and rode you will need a larger sail than would a heavy boat and heavy rode.
I sail in fresh water and use the gear described above with 25 feet of 5/16th chain and 150 feet of 1/2 nylon line. I try to anchor in 10 to 12 feet of water and add an additional 3 feet of rise for the distance between the water and anchor roller. I always use at least a 7 to 1 ratio for scope. Thus 10 to 12 feet of water and 3 feet to the roller equals 13 to 15 feet of depth calling for 91 to 105 feet of anchor scope. I lay down approxamatly 50 feet of line and back down the anchor as hard as possible until it holds and then run out the rest of the line and again back it down. After all this I have never needed a anchor riding sail.
If you still need this sail I would try a luff of 4 feet and base of 3 feet.
Ray

tkanzler · Apr 16, 2013

If you have a small tarp laying around, fold it diagonally around the backstay and join the two grommets with a piece of line and secure it to the base of the mast or wherever is convenient. See how it behaves, and if you like it, make one of similar size. Or mess about with an old bed sheet, reducing the size until you're happy, or too far and no longer happy, whatever the case.

Sumner · Apr 16, 2013

We bought the kit...

http://www.sailrite.com/Anchor-Riding-Sail-Kit-12-5-Sq-Feet

...and it has the measurements on that link. Ruth sewed....

.... it up and we use it quite often and it does help.

We have followed their instructions on how to rig it going off the center-line from the backstay off to either port or starboard and it seems to work well that way. It doesn't eliminate sailing on anchor but sure slows it down and limits the swing.

The page on it and its use is here...

http://purplesagetradingpost.com/sumner/macgregor-canvas/canvas-5.html

and here are two videos of it on anchor....

http://www.youtube.com/watch?v=vkLbyBld1lY

http://www.youtube.com/watch?v=MKjU842c9Zo

Sum

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sinnettc · Apr 16, 2013

Mine looks to be a little smaller than Sumner's. I made it from an old pentex genoa.

Sumner · Apr 17, 2013

centerline said:
...Sumner, and Chris, do either of you think more sail would be better?... if so, would you have it taller, longer, or proportionally bigger?

I think ours is about as large as I would want to go as far as rigging it and I think it is designed for boats quite a bit larger than ours, but I think our lighter boats probably sail on anchor more. At least that is the case between our two boats. From the one trip we did take with the Endeavour I don't think we will need an anchor sail for her.

The sail is a sail and the way it seems to work is that it sails the boat off in one direction and then keeps it pretty much there. Of course the wind isn't steady even though it seems to be and you still move some. Since is a sail if I think the winds are going over 25 I'll take it down.

I can rig it in just a minute as I added another uphaul line and block just for it and the bottom lines are fixed once you set them up once and snap on with carabiners. I found that by raising it some above the solar panels higher on the backstay that it was more effective.

As far as an anchor our 22 lb. claw worked very well in Canada and Idaho and I'd think you might be in similar conditions. We never drug anchor there. We now also have a 25 lb. Manson that I think is a better anchor, but if you didn't want to spend that much the 22 lb claw is great.

Two anchors off the bow would help in either a Bahamian style moor or in a "V", but I'd never put out a stern anchor in those conditions unless you were 100% sure the wind was going to be in the same direction all night.

You know we finally got so use to swinging on anchor that we don't even notice it. I think I use the sail more as something else to do to keep me busy

. We use the anchor alarm on the Garmin 76 and it is amazing when you look at the distance you have traveled on anchor in 2-3 days. Set the alarm right where you drop the anchor and before you back down and the alarm can be set for a smaller radius,

Sum

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topcat0399 · Apr 17, 2013

Sumner said:
I think ours is about as large as I would want to go as far as rigging it and I think it is designed for boats quite a bit larger than ours, but I think our lighter boats probably sail on anchor more. At least that is the case between our two boats. From the one trip we did take with the Endeavour I don't think we will need an anchor sail for her.

The sail is a sail and the way it seems to work is that it sails the boat off in one direction and then keeps it pretty much there. Of course the wind isn't steady even though it seems to be and you still move some. Since is a sail if I think the winds are going over 25 I'll take it down.

I can rig it in just a minute as I added another uphaul line and block just for it and the bottom lines are fixed once you set them up once and snap on with carabiners. I found that by raising it some above the solar panels higher on the backstay that it was more effective.

As far as an anchor our 22 lb. claw worked very well in Canada and Idaho and I'd think you might be in similar conditions. We never drug anchor there. We now also have a 25 lb. Manson that I think is a better anchor, but if you didn't want to spend that much the 22 lb claw is great.

Two anchors off the bow would help in either a Bahamian style moor or in a "V", but I'd never put out a stern anchor in those conditions unless you were 100% sure the wind was going to be in the same direction all night.

You know we finally got so use to swinging on anchor that we don't even notice it. I think I use the sail more as something else to do to keep me busy . We use the anchor alarm on the Garmin 76 and it is amazing when you look at the distance you have traveled on anchor in 2-3 days. Set the alarm right where you drop the anchor and before you back down and the alarm can be set for a smaller radius,

Sum

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On anchor in daylight its kind of fun watching the land pass by the windows from inside the cabin...sort of. At night its just plain disconcerting when suddenly waking up and the shore lights are whizzing by.

So; could I just cut and hem a similar size and outline shape from say....a couple of yards of nylon, and hoist it up off center like you did and use it as an anchor sail?????

Sumner · Apr 17, 2013

topcat0399 said:
On anchor in daylight its kind of fun watching the land pass by the windows from inside the cabin...sort of. At night its just plain disconcerting when suddenly waking up and the shore lights are whizzing by.

So; could I just cut and hem a similar size and outline shape from say....a couple of yards of nylon, and hoist it up off center like you did and use it as an anchor sail?????

I'd try it if you have the material. I can't really see an air foil shape to the one we sewed up from the kit. It it pretty straight forward. The kit did have the stuff to hank the sail on so it was convenient.

The lights at night are pretty interesting as you mentioned. I often think it is someone motoring by

,

Sum

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sinnettc · Apr 17, 2013

My riding sail seems about right. I think I took the dimensions from sailrite's smallest one and cut my old sail to fit. I'm pretty sure it would work ok for your boat.

Anchor wise I have 11 & 17 lb claws. The 11 has about 12' of chain and 150' of rode. The 17 has 20ish feet plus 150' of rode. I also have a 13 pound danforth with 6' of chain but that's strictly a lunch hook for the lake.

Have you taken a look at Detroit Lake lately? Deep enough to sail? Still less than 4' of water at the foot of the ramp at Richardson and I've got a bad feeling we're not going to get enough for me to launch this year. Time to start doing some serious planning for the San Juans trip.

Ron20324 · Apr 18, 2013

I have a DIY article from the January 2007 (Sailmagazine.com) issue about making a riding sail. Jess Gregory, author. There is a graph to calculate the area of the sail. For the 25, they suggest a 15-square-foot sail. The small print says boats that have the sail mounted to the topping lift (as opposed to the back stay) can improve results by increasing by 15 percent. Not sure how they calculate it, but here is a sampling. It seems starting at 15 feet, for each increase in length by 5 feet, add 5 sq feet of sail. Boat length/sq feet:
15/5,
20/10
25/15
30/20
35/25
40/30
45/35
50/40
55/45
60/50

topcat0399 · Apr 18, 2013

Sumner said:
I'd try it if you have the material. I can't really see an air foil shape to the one we sewed up from the kit. It it pretty straight forward. The kit did have the stuff to hank the sail on so it was convenient.

The lights at night are pretty interesting as you mentioned. I often think it is someone motoring by ,

Sum

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Thank you Sum; I'm going to rig something up.

15 Square Foot sounds like a good start.