Friday night Roommate Dan and I took our girlfriends out sailing around 7pm. Wind was a fairly consistant 8-9kts according to the birthday present from him, a Kestrel 1000 wind meter. Normally I would have just put up my normal working genoa (110%) in anything over about 8kts, but I figured as late in the evening as it was it should die down soon, so I had Dan rig my drifter. I don’t recall the exact measurements of the sail but the foot is roughly 22 feet long, giving it something close to 400sq ft of sail area. I cannot run it into the jib sheet car, as the track stops 5 feet forward of the clew of the sail. I have snatch blocks that I attach to the stern cleats and run the sheet line forward to the jib sheet winches. The only picture I can locate of it at the moment is this cell phone pic from last season.
Edit: Found another picture of the drifter, you can really get a feel for the size of the sail in this one.
The wind stayed pretty consistant around 8 kts for most of the night, and I’ve never seen my boat move so quick! We crossed the sound in roughly an hour, with the GPS reporting speed over ground hovering around 6.8kts, and jumping as high as 7.3kts for brief moments (my LWL is 22.3 ft, so my calculated hull speed is 6.2kts). with the knot indicator reading pretty close to the same most of the time (so current probably didn’t play much into it)
We ended up sailing across the sound and tieing off at the Huntington town dock and having a very late dinner at Rosa’s Pizza in Huntington Village (highly reccomend it). Followed up by a couple beers at Christophers Bar before catching a cab back to the docks.
As we came into Huntington Bay the wind died down to 2.3kts (app), when I measured the wind speed in the slot, it was reading 3.8kts, and the GPS was reporting our SOG as 3.8kts and the knot indicator was reporting ~4 kts as well. The tide was going out, and we were heading into the harbor, so any current there was, we were fighting it. That means we were cruising along at 1.7 times the wind speed. 🙂
The trip back was just as quick as the trip there. We were on a reach, so I pulled out the whisker pole and attached it to the clew of the drifter with a shackle, unfortunately I am still working to come up with a good way to attach the whisker pole to boat with this sail. I have to use the shrouds to attach to. I don’t like doing that as it puts side load on the shrouds that they are not intended on taking, but until I come up with something better, that’s what I’ve got to work with.
While Dan took the helm for a while I took a few pics of the chart plotter with my phone showing the reported speed.
reading 6.7kts, you can also see the cabin in this shot, with the red night time LED lighting I installed this spring.
The winds held up for the rest of the night and we didn’t slow down until we entered Stamford Harbor and started to drop the sails.
Installed my new halyards earlier this week, took the time to calculate the size I should be installing as opposed to just guessing. built a excel sheet to calulate the percentage of working load on the line based on the square footage of the sail, and the tensile strength of the line.
according to the American Cordage Institute the Safe Working Load of a line is 90% of the tensile strength, minus a safety margin of at least 5 times the load you are expecting to put on the line gives you the Maximum Safe Load. Put simply, take 90% of the tensile strength, and divide by 5, and that gives you the Maximum Safe Load you can use that line for.
then to calculate your wind loading of the sail, use the following formula (Square ft of the sail)*((wind speed in kts)^2)*0.00431
I created a Halyard Size Calculator in Excel to do all the number crunching for me… to use it, look up the tensile strength of the line you are considering using, enter the values in row 4, and enter the square feet of the sail you are looking to replace the halyard for in cell C7.
The table below will give you a percentage of the Safe Working Load the line will be at in a given wind speed. You then need to determine what the maximum wind speed you intend on having the sail hoisted in, before you reef it (for most people this will be around 15 or 20kts). Then you need to look down the wind speed row, and find the smallest line that is under 20%. This will be the smallest halyard (or sheet line) size you can safely use on that particular sail.
The other thing you will want to factor into your decision is the working elongation, or stretch of the line. Look at the line specs and see what the stretch specs are for the line you are considering. Most companies will give you percentage of stretch at a given load. so if you are operating the line at the maximum 20% load, and the line has 1.75% stretch (such as the New England Ropes Sta-Set X line that I just bought) you need to calculate the length of your halyard, for example I’ll use 100 feet, you would have 1.75 feet, or 21 inches of working elongation, or stretch of the halyard. You will probably want to minimize this as much as reasonable, and to do so, you will need to use a larger line, so you are working at a lower percentage of it’s safe working load.
For my halyards, to reduce stretch as much as possible, I went with the 3/8″ line, and assuming I am always reefing my 165sq ft main any time it is blowing over 20kts, that gives me a maximum load of 5.75% of the safe working load of the halyard, and roughly .35% working elongation, which over the roughly 40 feet my main halyard that is not coiled in the line bag in the cockpit when the sail is hoisted, gives me roughly 1 3/4″ of working elongation / stretch of the line when a gust of wind blows, thus keeping the sail shape as best as possible.
This is the first post I’m making on the new site. so just to summarize what I’ve done on the boat so far since buying it in June 2009. I’m sure I’ll be referencing many of these things in the future, so here’s the list:
2010 projects completed so far