IFA Clinic 9-12 September 2003, Cadiz
Arif Gurdenli
http://www.finnclass.org/interestingstu ... c_2003.htm
Leseprobe:
Luca's lecture was on boats, rigs and tuning : all the secrets for a fast Finn. (9th Sept)
Optimum weight for a Finn sailor
These days the optimum weight seems to be around 103. This may be down to 95 as minimum, and up to 115 as max. to be competitive.
Centreboard pin position
In general, heavy guys can move the pin forward where the lighter sailors would prefer to move it back. Also in light winds it would be faster to move it forward and would be faster to move back in heavy winds.
Deck ring position
Considering Devoti boats, 1 big + 1-2 small pieces of blocks would be ideal in from of the mast ring. In heavy wind the ring can be placed more forward and in light winds could be moved aft.
Mast rake
More technology is involved in the rake measurement. A tape is still used but a weight system seems to be more accurate.
With a tape, 6.77 metre would be an average rake. Using a cord of leach length where an electronic scale is attached at the end, boom is positioned on deck and the load is measured as 37 kg for an average measurement. This can go down to 32-33 kg as a minimum (by raking the mast aft).
In flat waters and light winds you can rake the mast more back and in choppy conditions more forward.
Mast types
Two type of masts seem to dominate the class these days:
a) Diamond shape; can deliver more consistent masts according to the required measures. Since the shape is more symmetrical and the draft position is in the middle, it's easier to build the mast to the numbers. Also the centre of gravity may be slightly lower. These masts have quick response (more nervous)
b) Teardrop shape; may have a better aerodynamic shape to produce a narrower angle of attack on the sail. This type of masts is more difficult to produce to the required numbers. Therefore, would be vise to get the numbers of already built masts and choose in between. These masts are slower in reaction.
Mast deflection
Most sailors and sailmakers test the masts by supporting the mast at the bottom and at the deck ring, then by attaching 12 kg at the tip.
Fore/aft measures:
Tip deflection (difference of mast tip position before attaching the 12 kg, and after attaching it); 49 cm is stiff - 52 cm is on the softer side.
Middle deflection; 110 (stiff) - 125 (soft)
An all-round mast (fore/aft); 86 mm at 1/4 - 117 mm at 1/2 - 86 mm at 3/4 with 51.5 cm tip deflection
Side to side measures:
Tip deflection; 37 (stiff) - 42 (soft)
Middle deflection; 115 (stiff) - 130 (soft)
3/4 deflection; 90-93% of middle deflection
An all-round mast (side to side); 127 mm at 1/2 - 92% at 3/4 with 39 cm tip deflection.
Sails
North Sails have a firmer cloth and is built for relatively stiffer masts.
Victory Sails have softer clothes, need more mast bend in the middle.
In general, best would be to decide on one sail and stick with it, since the feelings are very different.
1 mm of change in the mast curve (by the measurement) may result in 0.8 mm change in luff curve of the sail.