505 Tuning Sheet by Howard Hamlin

Jay Glaser at Danger Sails has numerous main and jib patterns. After testing al lof them and in various combinations, we have settled in on one main and jib combination that is really fast in all conditions. In making that determination, we also placed a large emphasis on evaluationg the speed of others. Bruce Edwards and Dave Shelton had placed 3rd at the 1989 World's using the same main and jib combination I am referring to. Mike Punnett and Scott Ikl‚, considering their very light weight, have very successfully used this same main and jib combination. The jib pattern we are referring to is known as the Short Luff All Purpose Jib (long luff for non-launcher boats). The mainsail pattern is referred to as the All Purpose Main.


1. Centerboard. The leading edge of our centerboard in 8'5-1/2" from the transom.

2. Mast Step. The aft edge of our mast at the butt is 10'1-1/4" from the transom. I personally believe that this dimension is not that critical, although the general consensus is that the mast should be placed as far aft as possible.

3. Spreader Height. Our spreader bracket isn located on the mast 10'2" above the deck. I also feel that this dimension is not that critical.

4. Spreader Dimensions. I believe it is inappropriate to sompare spreader dimensions on one boat to another due to the multiplae variables such as spreader height, hound height and chainplate locations. However, for your own boat, I do believe it is useful to keep a record of spreader tip-to-tip and deflection dimensions, for purposes of making changes or repeating dimensions on a new mast. Over the years, I have tried many different spreader dimensions and found that I always come back to something very close to the following dimensions. If you drew a straight line between the point at which a shroud exits the mast and the chainplate, the spreader should be approximately 1" forward of that line and 1" out to the side. If the trapeze hound is located very close to the shroud hound, this test can be made very easily by holding the trapeze ring at the chainplate and then by sighting upwards and evaluating the didtance between the trap wire and the spreader tip. To be consistent, I always make this analysis when the mast is upright (rake at approximately 25'7"), the rig tension just snug, and with no prebend in the mast.

5. Shroud Hounds. We have two hounds heights, high and low. In the high hound location, the shroud exits the mast 10" above the forestay exit. We use the high hound location almost all the time, unless we are very confident a regatta is going to be sailed consistently in overpowering conditions. For example, we used the low hound location at the 1990 North American Championships in San Francisco. In the low hound setting, the shrouds exit the mast 1- 1/2" above the forestay exit.

6. Trapeze Hounds. I believe the trapeze hound should be close to the shroud hounds. Ours are approximately 2" above the shrouds.

7. Side Bend. In order for the boat to have the same speed on each tack, I believe that it is critically important that the side bend behaves the same on each tack. I also believe that this is the only culprit in a 505 which would cause unequal speed/performance on each tack. There are two causes for the mast to not behave the same on each tack: 1) the mast is not set up properly side-to-side in the boat, and 2) the mast has permanent side bend (all masts have some). The process of setting the mast up begins in the dinghy park. With the rig upright (i.e., no rake) and a slight bit of rig tension, adjust the mast ram so there is no bend. Without a main on, put your eye against the aft edge of the luff groove, and sight up the mast. If there is even the slightest bend to the rig, loosen the shrouds and make adjustments to them until the mast is perfectly straight sideways. For example, if the mast tip bends off to starboard, then ease off the starboard shroud. If, after making these adjustments, the mast bend is not perfectly straight sideways from the tip to the gooseneck, then it is probably a result of some permanent bend in the mast. If this is the case, continue to make the adjustments until the mast makes an "S" shape which is evenly balance an each side. Now comes the water test. In moderate trapezing conditions, have the crew drive from the wire, go forward, put your eye on the luff groove of the mast, and sight upward. When the main is all the way in, I believe that when sighting between the gooseneck and hounds, the mast at the spreader should be in the slot [bend to leeward] approximately 1". The mast tip wil lalways be falling off to leeward, so I tend not ot pay too much attentionto what is going on above the hounds. Next, while sighting up the luff groove, have the crew slowly ease the main out until the end of the boom is approximately at the corner of the transom. While this is taking place, focus on what is happening to the side bend of the mast in the area of the spreaders. It is my belief that, while easing the main as described, the mast bend should go from 1" to leeward to straight or just slightly popping to weather. Now tack over to the other tack and repeat the same procedure. If the mast is not behaving the same on each tack, you need to make adjustments. For example, lets say that, with the main all the way in, the mast at the spreaders is further in the slot on starboard tack than on port. In this case you would need to ease off on the starboard shroud.