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RE: Mast Track forward, back or centered?
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SteveFoy



Joined: 15 Jan 1995
Posts: 27

PostPosted: Thu Jul 17, 2008 12:05 pm    Post subject: Reply with quote

The mast base should be positioned so that the center of effort of the sail falls between the front and rear straps. That way when you are powered up in your sailing stance, the pull of the sail is perfectly balanced against your body supported evenly by each foot in the strap. Any other approach means you will be over-weighting one foot over the other and why would you want to sail that way? You can temporarily lean forward to go upwind better, or lean back to go deep down wind, but this is easiest when you're balanced to begin with.
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isobars



Joined: 12 Dec 1999
Posts: 19220

PostPosted: Thu Jul 17, 2008 12:28 pm    Post subject: Reply with quote

WSing textbooks, based on physics, say the sail's center of effort (COE) should be directly over the board's center of lateral resistance (CLR) in a beam reach. If it's not, the board constantly seeks to turn in the direction required to put the COE over the CLR. We thus have to put the sail's trim out of whack (OOW) to sail in a beam reach. This compensates for the off-beam steering (OBS) but induces both aerodynamic and hydrodynamic drag, slowing us down in a beam reach. Thus unless the center of footstraps (COF) happens to match the CLR caused by fin style and size and location, average hull lateral drag location, and rider lateral aerodynamc drag (FSASALHLDLARLAD), the COF should not necessarily match the COE.

Capische (C)?

Mike \m/
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swchandler



Joined: 08 Nov 1993
Posts: 9465

PostPosted: Thu Jul 17, 2008 12:38 pm    Post subject: Reply with quote

After a deft series of movements mixing up the face down walnut shells, the question is asked. Where's the pea?
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isobars



Joined: 12 Dec 1999
Posts: 19220

PostPosted: Thu Jul 17, 2008 1:14 pm    Post subject: Reply with quote

OK, I'll simplify.
If the COE is forward of the CLR, the board will turn downwind.
If the COE is aft of the CLR, the board will turn upwind.
Using sail trim to compensate for either will slow the board down.
Screw footstrap placement except for its impact on the CLR.

\m/
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LeeD



Joined: 12 Jun 2008
Posts: 1175

PostPosted: Thu Jul 17, 2008 9:37 pm    Post subject: Reply with quote

I certainly ain't no physics engineering marvel, but when you hit my head with a hammer, I can feel it......
JohnI, you might rethink your statement a hair....
Track forwards means less weight on the nose WHEN YOU ARE PLANING!!
Hard for me to believe, also, but Cydall, one of the locals, told me that and I had to really try it. Track forwards means more rake angle, with the top of the sail going farther BACK over your center of footstraps!!
Wierd, I know. You gotta raise the mast the same amount as you move the track forwards.
Huge rake angles allow the older track forward, superheavy poly boards to actually get up and go.
Track well back might mean upright mast positioning, and all the weight straight down on the mast track.
Wierd, I know. VYV says the same thing, more or less, with experiementing thrown in.
Of course, raked sails tend to LIFT the front of the board over straight up and down rigs which should drive the board forwards! That was thrown in for you, a counter to my proposal.
I like argueing both sides of the equation......
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jingebritsen



Joined: 21 Aug 2002
Posts: 3307

PostPosted: Fri Jul 18, 2008 5:04 am    Post subject: Reply with quote

Yet, with my base forward, why does the nose of my board seem lower than anyone else's when we're comparing one sailor vs the next? Methinks there's more than one thing going on with sailor/rig dynamics. Sheet home is something I'm constantly saying to folks that want to go faster, or be more controlled when they ask me what's going on with their techniques. Maybe based on what you're saying, most folks don't sheet home over there too? Part of my technique must have an extra measure of mast foot pressure? Someone taking pics on a Mother's Day westerly mentioned that my board was trimming flatter than anyone else's no matter whose kit I was using.

Sometimes, when testing, someone will trade the whole kit with me. Sometimes, they comment about my trimming choices being better than what they would choose or be too oriented for tall people. He/she will lower the boom a bit and we retry. The base stays where it was. On Gnigler's stuff, other than some of the SS's, I tend to like the base way forward. On Exocets,F2's, Fanatics, RRD etc. about 135-138 is about right for me.

I've tried base back numerous times and find with my sailing style that the fin loads up too much and the boards get flighty and nose high. Also, the planing power can diminish with the nose high. Base back helps when I've got a dedicated wave board with lots of features that make it a great wave board, but dullish for flat water on those days when that board is all that I've to play with on a flats day. If base back worx for you in Berkley, then have at it. Cheers.

Maybe, if I had a ton of fins, I could base back on really strong wind days and change my fin? Certainly would consider doing so when planing is not much of an issue. I haven't bothered much with cluttering up my life with lots of fins, since the industry has delivered a higher quality stock fin of late.
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windoggie



Joined: 22 Feb 2002
Posts: 2721

PostPosted: Fri Jul 18, 2008 12:42 pm    Post subject: Reply with quote

isobars wrote:
OK, I'll simplify.
If the COE is forward of the CLR, the board will turn downwind.
If the COE is aft of the CLR, the board will turn upwind.
Using sail trim to compensate for either will slow the board down.
Screw footstrap placement except for its impact on the CLR.

\m/


But what about the BFD?

_________________
/w\
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LeeD



Joined: 12 Jun 2008
Posts: 1175

PostPosted: Fri Jul 18, 2008 2:22 pm    Post subject: Reply with quote

Interesting personal observations, JohnI.....
My observations are based on a pro level sailor using dialed gear, then changing the mast track about 1.5" from standard.
NOT anything to do with intermediates, can't jibers, or guys who aren't the best at any location.
Seems if you are riding a go fast board with a low nose, you should be OK as that board HAS a lower nose and somewhat flat trim angles mean speed thru lighter windholes, then you lean back to get top speeds. Aren't you usually the fastest guy out in the water? That usually translates to highest speeds in LULLS, then slightly higher in the gusts.
Anyone riding around with a high nose is plowing, going slow, too high trim angle, can't glide thru holes, can't plane up early.
Since the board tries to find it's natural trim angle regardless of rider positioning, rig positioning, or board speed, a lower nose should mean you are going faster on average.....not an undesireable trait.
I suspect at your 195 lbs or so, and using modern wider, shorter boards, that some other aspect is involved with the board's trim angle.
And at my 145lbs., track positioning on older 9' slalom boards translates almost exactly 134-137cms, the SAME as yours, and I'm 50 lbs. lighter.
I assume you use backstraps back, front straps forward on your go fast slalom boards.
I do, as does some very fast 240 lbs'ers!!
We adjust final trim angle with sail and fin sizing differences.
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jingebritsen



Joined: 21 Aug 2002
Posts: 3307

PostPosted: Fri Jul 18, 2008 2:37 pm    Post subject: Reply with quote

Leed, my tastes on foot straps is fairly out of the box. Boards I've made this observation of forward base is better for me are too numerous in brand and class to list or number. Yes, typically, I can go more fasta than the avg sailor in my humble pond. Others pick up speed/technique when they ask for a bit of coaching from either me, Eddy P. or Steve Gottlieb.

The Mag board test crew has very few can't gybers. Sure, there are plenty of those about in any other venue anywhere I sail...

Sheet home, in my world, includes telling folks to get their boom heights right, harness lines further back/longer, and straightening their lead arms while adding downward pressure with their hands thru the boom to apply more MFP. Worx even in onshore ugly wave sailing.

Sometimes week enders forget the fundamentals.....
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LeeD



Joined: 12 Jun 2008
Posts: 1175

PostPosted: Fri Jul 18, 2008 2:52 pm    Post subject: Reply with quote

I suspect your 195lbs is quite a bit faster than my 145.
I usually sail only with guys who ARE the fastest in Berkeley, ranging from 160lbs Chenda to 240lbs BenB.
Let's imagine here.....
We stand where we stand on a board. Moving the track forwards, and raising the boom the same amount, means you tilt the mast BACK more than before (track more back), meaning weight over the back of the board MORE, maybe weighting the front of the board LESS ????
We stand where we stand. Moving the track back from standard, a position you got dialed, means standing the mast more upright, necessatating lower boom, meaning more rig in front of you, meaning more weight on the nose, maybe meaning LOWER nose ???
Notice my double question marks.
I'm NOT the authority on mast base positioning, and am constantly fiddling and asking really good sailors of THEIR opinions.
I HATE being slower than the big guys on their newest gear.
I DO suspect pro sailors your size use tracks well back.
I see the fastest little guys using tracks pretty far forwards.
Yes, pro sailors your size are faster !!!
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