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Lift from fin?
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westender



Joined: 02 Aug 2007
Posts: 1167
Location: Portland / Gorge

PostPosted: Mon Mar 25, 2019 7:42 pm    Post subject: Reply with quote

rtz wrote:
I'm trying to get this beast to plane easier. For easiest planing; run the mast base all the way back?


For top speed I'd try it all the way back. Maybe not for early planing. Probably going to take some skill and effort to make that thing go no matter how you move the parts around.
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kmf



Joined: 02 Apr 2001
Posts: 493

PostPosted: Mon Mar 25, 2019 9:35 pm    Post subject: Reply with quote

It seems to me that Rtz has the footstraps in the inboard beginner position. I think to unleash more performance from this board the footstraps need to be moved back and out. Along with installing the appropriate giant fin for a 9.0 sail.

Kmf
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coachg



Joined: 10 Sep 2000
Posts: 2767

PostPosted: Tue Mar 26, 2019 12:37 am    Post subject: Reply with quote

kmf wrote:
It seems to me that Rtz has the footstraps in the inboard beginner position. I think to unleash more performance from this board the footstraps need to be moved back and out. Along with installing the appropriate giant fin for a 9.0 sail.

Kmf


Exactly, if you want to get that beast moving. A bigger fin requires more leverage by standing farther out towards the rails. You have the straps forward & inboard limiting the size of fin you can run. With your 9.0 slap a 50-60 cm fin on that board & move the straps out & back.

This is a picture of a Starboard Start with 8.5 sail & 51 cm fin. With straps out & back you can see how it frees up the board to plane.

Coachg



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swchandler



Joined: 08 Nov 1993
Posts: 9470

PostPosted: Tue Mar 26, 2019 2:19 am    Post subject: Reply with quote

I'm with kmf and coachg. The front and rear footstraps need to be located in the outboard positions to open up your performance options. That would apply to improving both earlier planing and upwind abilities.
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isobars



Joined: 12 Dec 1999
Posts: 19222

PostPosted: Tue Mar 26, 2019 10:29 am    Post subject: Reply with quote

DanWeiss wrote:
isobars wrote:
I'd like to see a longitudinal video from a GoPro mounted beneath a board looking back at a long blade fin being pushed hard. SNIP


Here you go: https://www.youtube.com/watch?v=OEhYC9IYOSU

THANKS. Those shots at 8 and 24 seconds REALLY emphasize fin curvature, which (as some folks here suggested) probably contributes noticeable vertical lift, especially when the hull is contributing none if it's out of the water.
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boardsurfr



Joined: 23 Aug 2001
Posts: 1209

PostPosted: Tue Mar 26, 2019 11:05 am    Post subject: Reply with quote

Yes. Interesting difference is that the vertical lift from the hull is directly linked to drag. Assuming a flat wetted area that does not change, increasing the angle of the board will increase both vertical lift and drag.

But for vertical lift from the fin, the lift is not directly associated with the drag. For example, if you increase the vertical lift by increasing how much the fin bends, the drag does not change.

As windsurfing skills and speeds increase, you may learn that keeping the board flatter and using the vertical lift from the fin to push the board up makes you faster. Perhaps the most impressive speed session during our trip to Oz was when Chris Lockwood (Slowboat) did 40 knots on a 138 liter board, on a day where other speedsailors were on 60-90 l boards (and slower). He picked the big board because he was fighting a bad cold and "barely made it down the stairs", so he wanted an easy session. His mastery of vertical fin lift is one big reason he's the fastest windsurfer in Australia, according to the GPSTC rankings. Although if might help that he designed his own boards and fins..
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westender



Joined: 02 Aug 2007
Posts: 1167
Location: Portland / Gorge

PostPosted: Tue Mar 26, 2019 12:02 pm    Post subject: Reply with quote

So how much planing time does RTZ actually have? I could get my old Alpha 160 planing without too much trouble so I know it's not impossible?
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rigitrite



Joined: 19 Sep 2007
Posts: 486
Location: Kansas City

PostPosted: Tue Mar 26, 2019 8:23 pm    Post subject: Reply with quote

bericw wrote:
Incidently and off-topic, rigitrite, I know you're going for it on the water! Please let me know if you are ever in the area and want to sail the eastern gorge. Yeah buddy!

Finally got another day on the water a couple weeks ago after a drought from the last days of west wind out here which were around Christmas. Summer is coming! Hope you're getting some!


Thanks man! I finally get to sail tomorrow (3/27). This is by FAR the longest I've gone without sailing: 6 months! It's been a looooong, cold, ugly winter. It got cold on October 4th and didn't warm up until March. Finally we get the ice all melted off and the wind/warmness to line up. I'm going to OBX-wind in about two weeks, so that'll be nice. I'd love to sail the gorge again, last time was 2003!

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Kansas City
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