| Author | Message | ||
     Mike Bergmann New member Username: Mike_bergmann Post Number: 15 Registered: 09-2005 Rating: N/A |
Hi Scott I am not very worried about this - I have owned the boat for 10 years and this situation has been pretty constant over that time. In my experience of boats, all hulls settle or shift slightly from the "land" support to the "water" support. In the case of our boats, the load on the keel stub is an upward force supporting the rest of the boat when on land, and it is a downward force supporting the weight of the keel (less buoyancy) when in the water. The "ring" shape of any hull will change slightly when a force on it changes from 4800 lbs. upward (the weight of the boat without keel) to 3000 lbs. downward (the weight of the keel less buoyancy). My measurements on the tie rod show that the deflection is in the range of 1/4". If I launched the boat with the partners already set up I would never even see this. My previous boat (a Cal 24) would deflect about 1/8" to 3/16" from the trailer to the water, and I have never seen a boat that does not. As a structural engineer, I can tell you that all structures will flex or deflect under load. If the deflection is excessive, you will observe damage or distress in the material. I have no stress cracks or other signs of distress. The shroud turnbuckles have not shifted since I have owned the boat. As I noted before, the lowers are closed up (about 3/4" remaining.) The uppers have about 1 1/2" left, and the intermediates are almost fully extended. If the step had settled, all turnbuckles would be closed up, not just 2 of 6. I think the people who cut these shrouds just had a slightly off day. Since the lengths are almost identical from port to starboard, I am guessing that they had a slightly defective set of measurements. My method of setting up the shrouds is simple and reliable - I learned it from my first racing skipper on a Lighting in the early 1970's. Once the boat is properly tuned (I follow the factory instructions), I leave it that way until the mast is to be unstepped. I release exactly 10 full turns on all turnbuckles on the boat before unstepping, and leave them that way (cotter pins inserted) through the winter. In the spring, after the mast partners are set up, I crank the same number of turns back on each turnbuckle. Since the boat has slightly settled over the winter, I can generally only get about 7 to 9 of the turns back on immediately. I wait about a week and then put the rest of the turns back on, and I generally do not have to retune for the rest of the season. If I do have to tune, it is never more than one turn on an upper. The fact that the tune stays almost constant for several months, and is repeatable over several seasons, tells me that the boat is very stiff, and tells me that there is no structural problem. I have checked the mast step area several times, and everything is extremely rigid there. If I find a problem, I can fix it easily. My previous boat had a deck-stepped mast supported by a laminated wood beam (no post) and the beam had been cracked by a collision before I owned the boat. I repaired it with a steel reinforcement, and that eventually settled. I finally laminated the wood beam with unidirectional carbon fiber as wll as carbon roving, and that ended up stronger than the original. I also had a broken boom on that boat, and I spliced it with carbon also. That boom is still on the boat 12 years later. My problems with the S2 are very small compared to the work I had to do on that old boat. Anyway, thanks a lot for the advice. Your recommendations on the mast stepping process are excellent. I had learned some of the same things "the hard way" so I'm glad you are passing on the experience to others. |
