What makes model yachting fun is there are several different parts of a yacht which can be changed or adjusted to gain more speed. It can be a better cut of sails, improved hull or keel, an upgrade to the mask or rigging. What ever it is, the end goal is to use the wind as much as possible for increase speed. But the wind is a unreliable power source and it is up to the sails to capture and hold it.The one course leg were the sails must maximize the wind as much as possible, is sailing towards the leeward mark. When sailing downwind, the sails should be out all the way goose-winging. This is especially true for the jib but because of it's boom being out of balance, it tends to swing back to the center line of the boat and loosing this effect. The result is, the jib is not maximized and the yacht does not get all the speed it could have. To counter act this, the jib sail needs to be assisted in catching as much wind as possible, for as long as possible.
To do this, a counter-weight is put out on the forward end of the jib boom for balance, this will help keep the jib filled, especially in lightwinds. This is more apparent with a gust of wind, if the sails are goose-winging, then the jib is already filled with air and the yacht gains an extra second or two in speed. Thus, no time is lost getting the jib out and filled with a chance of missing the passing gust.
The main complaint to the counter-weight is that extra weight. Weight and sailboats do not go well together, so in order to keep the weight down, the counter-balance is put on the end of a lever. To accomplish this, I did not want to have the counter-weight to be permanent. I wanted to be able to change weights to get the best results. So the question was how to apply the counter-weight to do what I wanted to gain and keep my yacht's downwind speed. For the jib boom, I used fiber glass arrow shaft and after trying several different ways to install a counter-weight, they all failed. I then realized arrow shafts can use arrowhead screw-in reciprocals! Well, after a trip to the sporting goods store, I have built a low cost, easy constructed and adjustable jib boom counter-weight.
To hold the counter-balance lever at the front of the jib boom, I used an aluminum broad head screw-in adaptor. It's light weight allows the counter-balance's weight to be applied as far forward as possible. For the first step in construction, I measured up 1/4 of an inch from the bottom of the tapered shaft of the adaptor and sawed off the access metal. From this, I used a 3/16 bit and drilled 5/8 of a inch hole into the center of the sawed face of the adaptor. This can be done by line-of-sight and a steady hand or with a drill press. At this point I filed off the sawed edge to a round end. Since aluminum taps easily, I used a 4-40 tap and cut the internal threads into the drilled hole for 3/8 nches. Now I have a effective way of holding a counter-balance weight.
For the actual lever, I used 3/32 diameter brass rod cut to the length of 2 1/2 inches. To thread the end, I bent 1/2 inch over to a right angle then I threaded the rod for 3/8 of a inch using a 3/32 inch nut. I then sawed off the bent end to have a final length of 2 inches for the lever. One point should be brought out, the longer the length of the lever, the less weight is needed, keeping the weight down to a minimum. Note; when measuring the lever's length for your yacht, the complete length of the jib boom's counter-weight needs to be measured so it will swing clear of the boat's deck.
Now comes the discussion of the counter-balance weight. To have an effective balancing of the jib boom, the main question is how much weight to use? I did not want to use too much weight nor too little, I needed a way to adjust it. To take care of this, two points are to be considered. One, adjust the length of the lever with the weight being constant or two, keep the lever's length the same and adjust the weight. I chose the latter, by keeping the lever length fixed, I can use different bass worm lead fishing weights on separate counter-weight levers. This way I have inter-changeable levers to find the optimum results.
Another option which can be done, by drilling completely through the broad head adaptor and then turn it over and with a slightly larger drill bit, drill 5/8 of a inch toward the front of the adaptor. Then in place of a brass rod, use 3/32 all-thread rod for a lever. This way the counter- weight lever can be screwed in or out and locked in place with a nut for fine tuning. This way a better balancing of the jib boom can be done to improve the effect.
As mentioned earlier, for the weight I use bass worm lead fishing weights. They are low in cost, easy to find and comes in various weights, which makes it easy to find the right weight. To glue the weights on the lever, I drilled a 3/32 inch hole and epoxied the non-threaded end of the lever into the back end of the lead weight.
After building a jib boom counter-weight for my Marblehead, I have found it to have improved performance on the downwind leg which my boat did not have before. So give it a try, it is an easy two hour project which may make your yacht more competitive. It could make a difference!