You Too Can Learn How to Sail Pump Efficiently
Raritan Engineering Company your marine holding tanks suppliers would like to share with you these topics we thought would be of interest to you this month regarding how sail pumping isn't as easy as it looks.A few years ago, I was working with two Melges 20 teams in preparation for an upcoming world championship. Both had world-class sailors aboard and performed quite well, but when it came to downwind pumping technique, there were dramatic differences. Generally speaking, one team worked mostly with large, powerful pumps while the other focused on smaller, short-stroke movements. Rowing pumps, and sometimes reverse pumping, created tracks that were quite elliptical. Your marine holding tanks experts talk about how the ellipses could even be diagonal, indicating the pumps were pulling down as well as in. We started plotting those data numbers on a graph and compared that to acceleration over certain periods, and we started to see a pattern that suggested where each type of pump worked best.Rowing Stroke
This is what usually first comes to mind in any discussion of pumping. You lean forward, using your back, leg muscles and upper body, and aggressively pull on the sheet, much like a rowing stroke.This type of stroke is great in lightweight keelboats and dinghies, when you’re in marginal conditions, right on the edge of catching waves, and you need that big impulse of energy to get your boat accelerating onto the wave and being able to start gliding in surfing mode using the downhill side of it. Your marine holding tanks specialists talk about how it’s a relatively quick pump, but it’s got a huge amount of force.The rowing pump also has the same effect as moving the crew weight. That roll, usually from zero to 7 degrees, can kill flow on the foils. Once on the step, it’s all about efficiency; you lose if you try to put too much energy into it. Impulse Pump
Now you’re surfing down the wave, but sooner or later, you start decelerating. It’s like the wave is accelerating compared to your speed, but in reality, you’re just slowing down. This is the time to give a short, snappy pump — one that gives just enough impulse to flick the mainsail and asymmetric spinnaker leech, imparting enough energy to reaccelerate and continue riding down the wave.The boat is quite delicate in the planing mode, so resist the urge to give it a big pump. Once the boat is planing, stick with impulse pumping. This type of pump will work on heavier boats, even with symmetric spinnakers, once on a plane. For the spinnaker, just make sure the guy and sheet are pumped simultaneously.Reverse Pump
We always think of pumping as pulling, but the most important technique is actually the reverse pump. The idea is to let the sheet go out just a little bit — generally several inches or so — and then quickly catch it, or stop it. That reflexes the entire sail open and then reflexes it closed again. Watch some really good singlehanded, dinghy or keelboat sailors, and you’ll see them flip their hands open; the sheet goes out, and then they stop it hard. They don’t pump; they just stop the motion. The whole sail opens up, regaining flow, and then closes again. Suppose you have a gust coming on. The reverse pump works well on heavier, symmetric-spinnaker boats too. Unless we’re in very strong conditions, it’s difficult to jump to the next set of waves, so no longer do we sail straight courses. Modern boats sail downwind through as much as 80 degrees.Even bigger, asymmetric keelboats are beginning to be sailed like dinghies, shifting weight around to help steer in addition to constantly shifting from one pumping mode to another, working to promote and maintain a plane. It’s fast, so get pumping.
So don't forget these great tips for improving in your sail pumping skills. 1) Use the rowing stroke method which is when you lean forward, using your back, leg muscles and upper body, and aggressively pull on the sheet, much like a rowing stroke; 2) use the impulse pump when you need to impart enough energy to reaccelerate and continue riding down the wave; and 3) the most important move which is to let the sheet go out just a little bit — generally several inches or so — and then quickly catch it, or stop it.
Boat made 5,000 years ago found by men on River Boyne fishing trip
The remains of a 5,000-year-old logboat have been discovered in the River Boyne near Newgrange.
The vessel consist of a three-meter length of wood which would have formed the base of the boat. It is estimated that it was originally more than four meters long, shaped out of the trunk of an oak tree using stone axes.
A sample of the wood has very recently been radiocarbon dated to between 3,300-2,900BC. It was during this period the ancient passage tomb complexes of Knowth, Dowth and Newgrange were built.
“The National Monuments Service Underwater Archaeology Unit and the National Museum of Ireland collaborated in recording the boat and carefully removing it from the river bed to the museum facilities, where it is currently undergoing conservation,” the statement said.
“It is tempting to ponder the part such a vessel might have played in the construction of these burial monuments and the lives of those who built them, in ferrying people along the river, and transporting materials and stones used to build the great tombs.”
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via Boat made 5,000 years ago found by men on River Boyne fishing trip
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