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Crash
25th August 2008, 07:15 PM
Just getting my mind around the fact that as you move the mast foot to a more forward position it helps keep upwind! I guess whats happeing is that the sail when you are in the starps is being pulled further back but as the sail comes back so the harness line length reduces so boom height should be higher for a more forward position? Sail size, larger sail more forward, smaller sails further back? Had some great sessions on the Apollo with the Wolfgang.Lessacher weed fin its better than the stock fin and has a good wind range.
Crash

WMarker
25th August 2008, 11:58 PM
Probably, hydrodynamically...the fin force is less since you are going slower...
An upright sail would drag the nose leeward. To compensate for the leeward turning force, reduce the moment arm between the sail's Center of Pressure and the fin by tilting the sail aft.

(I just flip down my daggerboard and press on..... (my $.02)) :)

Roger
26th August 2008, 08:46 AM
Hi Crash,
When did you send this originally?
Somehow I missed it last year, but I had a new heart valve installed last August, so
maybe it was during the time I was in the hospital.
Anyway, on your Apollo, which is very similar to a formula board (it's ISAF certified for formula racing) yes, moving the mast foot all the way forward can increase your upwind angle and VMG.
Exactly why, I have never been able to figure out, and while it has never worked for me, at my weight on my rigs and formula boards (I think an 11.0 m2 Retro or 10.4 m2 Sailworks NX are as large as I've ever tried to sail/race with) I know it works for all the formula pro sailors.
It might be as WMarker suggests.
In fact that really may be why it works.
I know that for a 75 kg sailor like me, even on Formulas and Apollos, I tend to run the mast foot much further back as this frees up the board and I do not have the weight
(might be technique or stance perhaps) to make a 100 cm wide board plane freely with the mast foot all the way forward.
For me, putting the mast foot up there just "sticks" the board, and makes it ride very hard over the chop at a somewhat slower speed than I can achieve with the mast foot further back.
But, as WMarker suggests, if you move the mast foot forward, you would be moving the CE of the rig forward as well and then you would need to rake the rig further back and probably shorten your harness lines and raise your boom to compensate for the additional rake angle to balance with the CLR of your big fin.
Makes sense.......?
Hope this helps,

tonymatta
26th August 2008, 10:12 AM
My experience has been with my Starboard Z-class which works much like a formula board in planing. I found that having the sail fully back helps get the board planing earlier in light winds and you haveto plane to get anywhere with a formula board.

When the mast is forward I need to tilt back too far to get the centre of pressure over the fin and the sail drags in the water. Moving it back helps to solve this problem by keeping the mast more upright.

In strong winds, moving the mast foot forward helps to make the board easier to controle.

In displacement with the centreboard down, moving the mast fully forward helps to enguage more leeward rail edge and this makes a very big difference to upwind progress. Roger has previously suggested that tilting the board to sink the leeward rail helps in planing upwind as well. I guess if moving the mast foot forward can help with keeping more leeward rail in the water without adversely affecting your planing then you should go upwind better.

Crash
27th August 2008, 01:06 AM
Hi Rodger only just posted hope your fit and well now.
In the latest edition of Boards Magazine it says:
" Forward.
Board more controlled with better/easier tracking. Gybing easier,more sercure with momentum on exit. Easier upwind. Tacking harder. Board slower less lively."
"Back
Harder to contoll in strong winds, feels faster and more lively. Harder to sail upwind Gybes more on the tail,so tighter, but less momentum and ease. More board in front feels bigger and moresubseptable to windage."
So are we saying that its differnt for Formula boards! I would have thought that moving the centre of effort forward would increase the boards downwing ability but this also means from the fixed position of the harness lines and straps the rig ends up futher back?
I run the Apollo with the mast track well back with the weed fin which has sorted a lot of the high wind control problems the board had with the normal fins.

toddewoell
17th October 2008, 09:26 PM
Hi Crash,
those fins put the center of effort right back, so you have to use the track in the backmost position. in my opinion the stance gets very comfortable this way. the advantage of high wind control is a nice feature on top. which version are u running? the "normal" Duo or the Formula Duo and in which size? I own the elder Formula Duo in 40 an 32cm , but i like the 40 better.

Crash
30th October 2008, 04:55 AM
Hi Toddewell I use awolfgang Lesstinger 40cm weed fin yes Im finding the lift it gives is more than the 75cm fin on my Apollo. I stuck it on my S/B 160 in its max back position it just took off in the lightest breeze, it gives incredible lift but as the wind picks up I think a couple of cm forward helps with control. Im toying with getting the next size down to see if there is a gain in high wind performance but would try a 35cm. Hows the 32cm as the wind picks up, which board are you using it on?
Regards
Crash