How to Trim Your Mainsail on a Catamaran

[Catsoon]

Folks- Thanks so much for all your input- I also found this article this morning in Cruising World- its short, but reinforces Traveler usage and tell tales. I need to sew more tell tales in my sail and improve my traveler to make it work easier- we'll see what Harken or someone has! Thanks!

Article Link:
http://www.cruisingworld.com/how-to/...ts-mighty-main

[tsmwebb]

Originally Posted by Catsoon

I need to sew more tell tales in my sail...

For leach tell tails I make small patches (~2" x 1") from a roll of adhesive backed Dacron. I then cut a slit on the patch about halfway up the short side and to the middle of the patch. Peel the backing off and insert a length of yarn or whatever you plan to use for tails. To install wrap the patch around the leach so that the tail is right on the trailing edge... This takes much less time to do than it takes to install (I could have made a dozen up instead of typing this) and when the yarn dies it is easy to remove the patches... The quest for the perfect non-grabbing, non-sticking tell tail material is ongoing but yarn is cheap and works okay.

Tom.

[daddle]

Yarn is the way to go. Not perfect but better in most all situations. Adhesive patches to secure the yarn are popular but the leaking adhesive around the edges is problematic as it often catches the yarn. I thread the yarn under a stitch of thread.

[Bruce626]

"Yarn is the way to go." - Yarn? This seems way too inexpensive for the typical yacht, just look around any shop handling marine supplies - they would never carry something as cheap as yarn.

Clearly what is needed here is some kind of expensive electronic gadget that needs power and can fail. Perhaps performing sail trimming using a strain gauge (aka load cell?)? One would think that a tension strain gauge could be built into a stainless steel waterproof housing with an eye on each end. Connected to a common Bluetooth transmitter and powered by a (AAA?) battery it could be connected to a PDA without wires getting in the way. This is more like the stuff one sees on the shelves.

In the simplest case, a flying headsail that is attached to the boat by only three lines, it would seem that a maximum of three strain gauges would be needed (and possibly only one if it is confirmed that the total force generated by the sail is transmitted to the boat with one third of the total force loading each line). Using the gauge, one could read the force developed by the sail directly and as one made adjustments in the trim, the effect of adjustment could be seen immediately on the readout. This would have the advantage of isolating the power developed by each sail in use and make it easier to learn the best combination of sail trim for each point of sail. Figuring out how to instrument sails with more (cars) or continuous (furler, bolt rope) attachment points will likely be a tad trickier – but it might be easier to instrument the stays and/or the mast until a force model is developed and needs only input from one strain gauge. One would think that much of this work has been done in that the people who engineer the rigging and design the sails must have some serious idea of the loads that develop on the head, tack, clew, and cars that attach a sail to the boat. Knowing the maximum forces gear was designed to withstand should make it easier to accurately size the strain gauge needed. Since the area of the sail is known (usually – furlers might be tricky) and the apparent wind speed is also typically being measured, it might be interesting to measure the instantaneous horsepower(?) being developed by each sail and collect this data for a baseline polar at various wind conditions. Comparing the baseline with current might provide a good measure of increased drag due to loading and/or marine growth. One would think that racers would use this technology –but I think that it would be useful while learning to sail a particular boat. Once learned, the instrumentation may not need to be left in place.

By collecting a series of data points – perhaps: 1) sail force measured by the strain gauge; 2) apparent wind strength; 3) apparent wind angle; 4) boat speed through the water; and 5) indicated course; one could generate polars for the boat which might be of some use. A more detailed polar might show the contribution of each sail in a series of internal lines which then add to give the polar of the total rig. This would enable comparisons to be made between different sail suites and/or locations – the strain gauges telling you which sails that are contributing. This information could be sampled periodically and collected and then displayed or printed out for closer scrutiny.

[daddle]

Hilarious. Well done! I retract my suggestion of using yarn...

[Palarran]

Little bored today Bruce?

Pretty funny though.

[thinwater]

What! I can't use yarn? There's been a WM orchestrated embargo?

Sail Delmarva: Wind Vanes

My daughter--just turned 16--keeps telling me I'm old. Well, old school.

[mikereed100]

Originally Posted by thinwater

My daughter--just turned 16--keeps telling me I'm old. Well, old school.

I'm so old I still remember cassette tape, the stuff that your car stereo used to spit out in streamers after the music stopped. Remember what good telltales it made? I tried dangling an old i-pod from the leach of my main once but it was disappointing.

Mike

[Tropic Cat]

Originally Posted by mikereed100

I'm so old I still remember cassette tape, the stuff that your car stereo used to spit out in streamers after the music stopped. Remember what good telltales it made? I tried dangling an old i-pod from the leach of my main once but it was disappointing.

Mike

The numerous answers are amazing. For the record, I carry 1 video cassette to this day which I use to attach telltales to my side stays. It works great.

I set my sail shape for conditions with the halyard, outhaul and boom vang, and spend the rest of the day in the cockpit with main sheet and traveler. I use the traveler to control weather helm (depower the main sail). I have a newer main sail and the out haul trim makes a huge difference when pointing or reaching. I only have telltales on my batten ends.

It's been a number of years, but I seem to recall that you set up a monohull the same way?

As to mainsail luffing. This is heavily dependent on what type of jib is in use. With a smallish jib, I agree, trim the main in until it stops. However, with a large genny, that simply isn't true. This time of the year, I sail most days with a 175 on the furler. The large overlap in the slot induces a small amount of back winding in the main sail just behind the mast. This luffing occurs when perfectly trimmed and shouldn't be trimmed out.

I can carry the 175 genny to 20 knots of wind, if I had to, but it's approaching overpowered at 18. With the 110 jib I reef at 25 knots .

[Jerry Woodward]

Originally Posted by Bruce626

"Yarn is the way to go." - Yarn? This seems way too inexpensive for the typical yacht, just look around any shop handling marine supplies - they would never carry something as cheap as yarn.

Of course one should not use cheap yarn. The only yarn that accurately conveys the wind flow (with a tolerance of .001mm) is vicuna yarn at $300 per ounce.

Windy Valley Muskox Vicuna Knitting Yarn at Yarnmarket