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Strange difference in VMG between free race and free foil gear

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Created by thedoor > 9 months ago, 5 Aug 2024
thedoor
2469 posts
5 Aug 2024 12:53PM
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Had two sessions today: first one on more of a free race set up second on my typical free ride set up. I got way better upwind angles on the freeride set up that I dont think are explained by the slightly lower current (1/2-1 knot) and higher wind (~2-3 knots)

Red Session (free race) ~120L Roberts with outboard straps front only, 6.4m single cam, sabfoil w1110 (1180 cm2, AR = 10), sabfoil s399 with 1 deg shim, fuse 101 cm. 101 cm mast.

Blue Session (free foil) 103L foilstyler with inboard straps, 4.7m wave sail, sabfoil w799 (1100 cm2, AR =5.8), sabfoil s450 no shim, fuse 899, 92cm mast placed quite forward in tracks.

The blue session is much more front foot biased due to mast being forward in tracks and the 450 stab.

Anyways i overlayed the GPS data onto a polar plot (red is freerace and blue is free foil) and it looks like I am getting about 3-4 knots higher VMG on the free foil gear. Seems surprising to me, perhaps a bit more powered on the blue session but still....I would expect the higher aspect foil, larger sail and longer fuse to really help upwind performance, maybe it takes more skill to get raceish kit upwind (ie bearing off to get more speed before pointing like a fin)






Here is the wind sensor data in MPH and the approx tidal current




cad184
61 posts
5 Aug 2024 2:53PM
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Two thoughts:

Maybe Your 120 l board is not wide enough, to put enough power on the wider frontwing. Normally You use 91 to 100 cm wide boards for VMG.

The 101 ist the sabfoil slalom fuse. For better up-/donwind You use a longer fuse (Sabfoil had a 110 and a 115 Race Fuse, that also puts the frontwing further forward for better upwind power).

Subsonic
WA, 3354 posts
5 Aug 2024 9:42PM
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That is odd. It'd sort of make sense if the tracks were similar, and maybe the free ride one was slightly better, but for the free race foil/board combo tracks to be back and forth only (I presume you were trying to point?) something is amiss, probably with the set up

putting aside differences in wind/current and presuming that you were well powered on the free race set up, how does it feel to ride it? I find to get it upwind I have to keep a fair bit of pressure on the back foot, and use the overburdening power to wind the board up into the wind. You start to feel the need to heel the board to control the pressure when it's happening right.

cad184
61 posts
5 Aug 2024 10:24PM
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Thats what I meant. With a too small board You don?t have the leverage to tilt the board to windward.

thedoor
2469 posts
5 Aug 2024 10:40PM
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The roberts is awesome to ride, it gives a very similar feeling/stance to fin windsurfing and its also is unusually comfortable when powering up on a reach. Seemed to be a weird combination backfoot pressure and harness pressure while reaching that seemed to work really well in controlling the lift of the foil. On my freefoil set up reaching is dicey and I doubt I ever get the foil close to its max speed on a reach.

I would say that I was moderately powered on the free race gear, certainly not close to OP. I was very well powered on the freeride gear, but as you know its hard to get OP on foil as you just point higher or lower. Although, I wasnt able to comfortably reach on the freefoil gear, but as mentioned above, I am rarely able to do that.

I was definitely trying to point on the roberts as i intended to use it as a foil raid board. With my current skill level I suspect I would need a lot more stabilizer or a lot more sail to get the freerace set up to point. edit: I was definitely on my back foot, and I think any more may have just resulted in a breach, maybe thats a sign i was underpowered

The roberts is 73 wide, but my foilstyler is only 64cm

thedoor
2469 posts
6 Aug 2024 1:13AM
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I checked another session on that freerace set up. and am wondering if yesterdays issue was more just a lack of wind than set up, esp as that sensor isn't on the water so possible it came up more than my estimate of three knots.

The session below was on 5.4 single cam, sab w800 (840 cm2, AR =7.4), same stab (s399) but no shim, same 101 cm fuse and mast. It was probably closer to 20 knots, anyways much better angles and VMG






Tide was it was also flooding with opposing current






Grantmac
2312 posts
6 Aug 2024 3:42AM
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Not enough front foot pressure on the first setup.

foilMead
7 posts
6 Aug 2024 7:16AM
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Off topic question: what tool are you using to generate the VMG plots? I also have a coros watch, but have not been able to find a good way to make a polar plot like that. Is there a preferred way to export the coros data? (.kml, .gpx, etc...)

aeroegnr
1731 posts
6 Aug 2024 7:47AM
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foilMead said..
Off topic question: what tool are you using to generate the VMG plots? I also have a coros watch, but have not been able to find a good way to make a polar plot like that. Is there a preferred way to export the coros data? (.kml, .gpx, etc...)


Looks like GPS Speedreader but the website looks to be down?
www.seabreeze.com.au/forums/Windsurfing/Gps/GPS-Speedreader?page=1

thedoor
2469 posts
6 Aug 2024 8:51AM
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yeah i drop the gpx file from coros into gpsspeedreader.

Just for reference this is my VMG on fin (7.1m race sail and 72 wide slalom board with 38cm fin) today at same location similar current (if anything a bit higher).












thedoor
2469 posts
6 Aug 2024 11:15AM
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Grantmac said..
Not enough front foot pressure on the first setup.



Kind of my conclusion too. More I think about it, I like riding front foot pressure because I can get up with less sail, make more of my gybes and allows flagged swell riding without dropping off foil. And I guess it also allows me to point higher and lower. The only negative is that I cant really reach.

Gwarn makes 99% of his gybes, flags on swell rides, but I believe he likes his foil box all the way rear like that roberts. I wonder if he is front foot pressure biased too

Grantmac
2312 posts
7 Aug 2024 1:31AM
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thedoor said..

Grantmac said..
Not enough front foot pressure on the first setup.




Kind of my conclusion too. More I think about it, I like riding front foot pressure because I can get up with less sail, make more of my gybes and allows flagged swell riding without dropping off foil. And I guess it also allows me to point higher and lower. The only negative is that I cant really reach.

Gwarn makes 99% of his gybes, flags on swell rides, but I believe he likes his foil box all the way rear like that roberts. I wonder if he is front foot pressure biased too


Reaching is where the slalom fuselages seem to be most effective. The VMG biased ones are built to support large sails and higher angles.

You could try a more powerful tail on the shorter fuselage like Starboard did with the 330 in their original slalom set-up.

BullroarerTook
297 posts
7 Aug 2024 7:34AM
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I've not seen you on a Robert's so I'm guessing it's new. You've spent years tweaking that freeride foil setup. Give it some time.

Paducah
2784 posts
7 Aug 2024 10:50AM
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My freeride set up has a decent amount of front foot pressure and goes upwind very well when powered up. My traditional race set up does better with front foot pressure (more stab angle) not to mention the plus fuse. I imagine the two are related.
If your freerace set up is dialed in for a reach, you are probably lacking enough foil "power" to go upwind well. A good vmg set up can be a little uncomfortable reaching.

Subsonic
WA, 3354 posts
7 Aug 2024 9:19PM
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I doubt the the Roberts board ( combined with the fuse length etc) is orientated towards upwind downwind vmg, but it should do upwind at least a little better than a fin, and arguably the free ride foil gear.
underdone wind speed wise would make the difference, but I don't think it could be put down to slalom foil vs course race gear.

thedoor
2469 posts
7 Aug 2024 9:38PM
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Subsonic said..
I doubt the the Roberts board ( combined with the fuse length etc) is orientated towards upwind downwind vmg, but it should do upwind at least a little better than a fin, and arguably the free ride foil gear.
underdone wind speed wise would make the difference, but I don't think it could be put down to slalom foil vs course race gear.


Yeah. I have no doubt a big race sail and 115cm fuse would go upwind way better than my 6.4 and slalom fuse or my freefoil set up. I think my point was more about the comparison between the free foil set up and the "freerace set up" esp as I was thinking the free race set up would be a lighter wind cruising option.

The roberts board with that big front wing (w1110) should def beat a fin too, so like you say it must of been underdone windwise

Gwarn
245 posts
7 Aug 2024 9:55PM
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Yes front foot pressure is alive and well with my style of riding it's much easier to control as it allows you to use your hips to trim your ride so It just happens subconsciously for me.

To the Door that was a fun day as I was up at 3rd ave with a sweet ebb going so nothing but swell ride one after the other.......

thedoor
2469 posts
7 Aug 2024 11:00PM
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Gwarn said..
Yes front foot pressure is alive and well with my style of riding it's much easier to control as it allows you to use your hips to trim your ride so It just happens subconsciously for me.

To the Door that was a fun day as I was up at 3rd ave with a sweet ebb going so nothing but swell ride one after the other.......


We gotta coordinate

WsurfAustin
651 posts
8 Aug 2024 8:39PM
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I recently got a free race sail just to try something different (Sailworks FR 3.9). Really not what I was expecting. High aspect ratio, shorter boom length. Comparing to my 3.7 wave sail. The FR is a lot harder to launch. Gotta pump like crazy for a long time. No low end power. When I pump, it feels like there's a big hole in the sail. Flying feels really odd with very little back hand pressure and sail trim is going to take some getting used to. I should have up sized a meter. I'll keep at it, but going to need a good consistent wind day (rare here) so I'm not constantly re launching. I've used the regular Flyer which was fine, good power and stability, but the Fee Race version is a completely different animal.

thedoor
2469 posts
9 Aug 2024 11:52AM
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WsurfAustin said..
I recently got a free race sail just to try something different (Sailworks FR 3.9). Really not what I was expecting. High aspect ratio, shorter boom length. Comparing to my 3.7 wave sail. The FR is a lot harder to launch. Gotta pump like crazy for a long time. No low end power. When I pump, it feels like there's a big hole in the sail. Flying feels really odd with very little back hand pressure and sail trim is going to take some getting used to. I should have up sized a meter. I'll keep at it, but going to need a good consistent wind day (rare here) so I'm not constantly re launching. I've used the regular Flyer which was fine, good power and stability, but the Fee Race version is a completely different animal.


My limited experience with flyers is that push to pump ratio is lower than my other sails. Could be that different technique is required or that they are designed to be super stable in flight so people can carry more sail and do less pumping?

boardsurfr
WA, 2454 posts
9 Aug 2024 9:52PM
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aeroegnr said..
Looks like GPS Speedreader but the website looks to be down?
www.seabreeze.com.au/forums/Windsurfing/Gps/GPS-Speedreader?page=1


GPS Speedreader downloads are now at github.com/prichterich/GPS-Speedreader

aeroegnr
1731 posts
9 Aug 2024 10:51PM
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boardsurfr said..

aeroegnr said..
Looks like GPS Speedreader but the website looks to be down?
www.seabreeze.com.au/forums/Windsurfing/Gps/GPS-Speedreader?page=1



GPS Speedreader downloads are now at github.com/prichterich/GPS-Speedreader


Thank you!

berowne
NSW, 1522 posts
10 Aug 2024 10:39PM
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Try moving the mast further back... physically the relationship between mast base front foot and front foil are the most important. If you give the foil excess power then you should be able to point higher... rear shim angle and or longer fuselage can help to.

Subsonic
WA, 3354 posts
10 Aug 2024 9:05PM
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Agree with that^^^^
making the geometry more compact should improve pointing ability

utcminusfour
749 posts
10 Aug 2024 9:44PM
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berowne said..
Try moving the mast further back... physically the relationship between mast base front foot and front foil are the most important. If you give the foil excess power then you should be able to point higher... rear shim angle and or longer fuselage can help to.

berowne,
You are saying move the sail back, right? I hate the vernacular that we use, there are two masts on one small craft! Don't get me started on front wing verses hand held wing! Which wing are you on brah?

I don't have polar graph or any data other than lining up against mostly wingers these days but bringing the sail aft has noticable improved my VMG. The other thing it (sail close to foil) changes is yaw balance (ie weather/lee helm) bringing the sail back increases weather helm which improves upwind vmg but makes it harder to reach. I only use reaching for brief moments to get flying or accelerate for a turn or wave. It's funny I do less and less dingy racing so I can go foiling more but still sail windward leewards out wave riding

thedoor,
Nothing beats two boat testing! I wish could line up against ya, I am sure we could learn a ton! ATM I am the only one in my area that windsurf foils. I am sure you can find some one in San Fran! Maybe Gwarn????

thedoor
2469 posts
10 Aug 2024 10:30PM
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Me keeping up with gwarn is a bit like gwarn trying to keep up with GG. Gonna be interesting to see their battle in baja this winter. Keep in mind that I don't anyone told greg its a competition :)

I love that app Boardsurfr esp the turn analysis. I have been working on turns recently. this is on my freefoil gear




Here is one from my best recent free race session at third







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"Strange difference in VMG between free race and free foil gear" started by thedoor