Select to expand quoteazymuth said..
I'm learning a lot from the pigeon and reptile brains 
I can see why foil centre of lift should be roughly between your feet, but why is the foil mast so far to the rear of the board?
The foil would be stiffer if the front wing was closer to the mast.
Armstrong wing boards have a forward geometry that seems to work?
Reptile reporting: Some good takes here by WoH, IanK, Subsonic and others. And great one further down the page by DarrylIG who certainly has the option of putting a box where he pleases.
www.seabreeze.com.au/forums/Windsurfing/Foiling/Starboard-Fuse-115-vs-115-?page=2#12
Ah, the good ol days of LeeD. He certainly was... special.
Another reptile brain here. To try to answer azymuth's question, I think the reason masts are so far back is history. Foiling started with everybody using windsurfing boards with the boxes far aft. You had to compensate by running the front wing far forward of the mast.
If we had all started foiling with boards that had the boxes far forward (like in the current wing and sup boards) we all could have started foiling with the same foils that were used by kitefoilers where the wing is right next to the mast.
Then there is also the consideration of sail versus wing or kite. Wing and kite have only two points of downward force: front foot and back foot. We windfoilers have to add in the sail base. This changes the entire geometry of the system, and it changes the entire dynamic of balance. You don't see wingers and kiters porpoising like we windfoilers do. They just get up, balance their feet, and stay that way for the whole session. Easy peasy. We get up and have to keep three points balanced. Since the sail is always causing changes in the sail mast base downforce, we are always having to correct the balance.
This is also why some people recommend keeping the sail mast as far aft as possible (as close to the foil mast as possible) to minimize the moment arm effect of the sail on the overall geometry.
Select to expand quotePaducah said..aeroegnr said..
Seems then that a more optimized foil board would have the foil box even further forward to reduce the wing overhang, but maybe the point of diminishing returns is already there. This seems big, and indicates how new this sport is still. I'll hold off on that slalom board purchase....
The challenge with that is what was discovered a while back, the boards sail better with the mast further back where the fin would be all other things equal. I don't know all the reasons why that. I would speculate the way we drive upwind off the mast and the need to transition small wings from windsurfing to foiling at takeoff are just two of the reasons.
The advantage of not having to use + or even ++ style fuses suggests there are compelling reasons for having the foil box generally where it is. However, I certainly can see a case where the advantages of thinner masts and shorter fuses override the negatives of having a foil box further forward. As said more than a few times in the AC campaigns, they design stuff to go fast, not easy, and leave it up to the sailors how to deal with it.
With regards to the foil mast position debate, one could try something like the 'All in one' boards with a track and tuttle box.... and move the mast, testing different fueslages to keep the foil in the same location...?
patrik-windsurf.com/aio/
Opposite side of the same coin, tintingwen put a Loke foil on a wing board and I asked him what differences he felt with the mast back.
"the main one is the position of the front wing...the whole is a little more nervous especially for carving, you must use shims under the stabilizer.
Very fast take-off and maintains impressive flight in light winds"
I have a NP Foilglide set that I'll play with on my wind/wing combo board. I don't use the set much so it will take me a while to dial in the wind side and then put the wing fuse on. The wing fuse is approx 10cm shorter so that may muddy the results.
It looks fast, but until we see an actual GPS speed guage on the screen, we will never know.
In God we trust. All others bring data.
Select to expand quotesegler said..
It looks fast, but until we see an actual GPS speed guage on the screen, we will never know.
In God we trust. All others bring data.
Segler your comment seems a little harsh, the video has merit as is.
Berowne put a lot effort put into this to share with those who have the same passion.
Nice video Berowne, thanks for posting. Some good tips there. When I first got my SB GTR I put mast base and straps forward and ran with -2 shim to control the lift. I found the strong lift in gusts (very GAF where I sail) quite intimidating. As my skills have improved I've started bringing things back and to my surprise I've realised I'm not going to die!! What ive kept doing though is bringing my back foot forward as speeds increase. More recently ive tried to leave my back foot where it is, but this has been mainly to avoid touchdowns in gusts than for any increased speed.
My max speed is a pretty untidy 27.9kt with a 550 front wing and 6m twin cam sail. On the bearaway I'm unhooked, back foot forward, hanging hard off the boom and on the edge of disaster!. I'm still getting some touchdowns in the gusts, so I think my fear of breaching has resulted in some poor setup and posture - time for a mind reset (I.e. HTFU) and more tuning.
Speed needs confidence > needs control > needs balanced setup (I'm not there yet)
Select to expand quotesegler said..
It looks fast, but until we see an actual GPS speed guage on the screen, we will never know.
In God we trust. All others bring data.
Seagler if you know how to get the gps data off a GoPro 360 let me know!
I used to use GoPro Quik to add widgets on screen but this is not possible on pc with 360 AFAIK!
Select to expand quoteFreeflight said..
... your comment seems a little harsh, the video has merit as is.
Berowne put a lot effort put into this to share with those who have the same passion.
+1
Data: www.seabreeze.com.au/forums/Windsurfing/Foiling/F4Foils-Tuning-Tips-Towards-30-knots-?page=3#8
He competes and results are posted. If he was slow, we'd know it. Lots for me to digest in the video and appreciate him sharing.
Select to expand quoteberowne said..segler said..
It looks fast, but until we see an actual GPS speed guage on the screen, we will never know.
In God we trust. All others bring data.
Seagler if you know how to get the gps data off a GoPro 360 let me know!
I used to use GoPro Quik to add widgets on screen but this is not possible on pc with 360 AFAIK!
Yeah can't get gps from GoPro when on 360 mode. Need to sync you watch or phone gps with rendered 360 video.
Sorry, I did not mean for it to be harsh. I apologize. Yes, berowne races and is all kinds of fast. I always look forward to seeing his videos. His trajectory of learning, improving, and racing has been very instructive and inspiring. In fact, he's my idol.
I am trying to see people's speeds as instruction for me (and maybe others). Above was written: "Yeah can't get gps from GoPro when on 360 mode." OK, thanks. I did not know that since the camera manual does not say that. I suppose the Quik manual does say something about that.
Since people already go to the considerable trouble to edit and publish their videos into the great products we see here in these fora, I am hoping that they would include the GPS overlay guages (where possible, of course). My dinosaur-vintage Contour+ and Gopro 5 Black cameras do a great job of this, but they certainly do not show 360 and you definitely see the mounting stick.
Thank you Berowne for the very helpful and perfectly timed video. For me most important take away is that foiling flat is comfortable but ultimately limiting. So I am working on angling the board to windward to hold the nose down and ignoring the sirens advising mastfoot forward.
But I have a challenge and am looking for advice.
When I reach and angle the board to windward I round up and end up foiling fastish upwind, it is good and stable but the opposite of what I am aiming for which is going fast across or slightly downwind. The only way I am succeeding reaching/broad reaching is with the board flat and back foot out - not good for all the reasons you explain so well in your video (you reach a point where you cannot lean far enough forward to hold the foil down in a gust)
My set up is F4 100 slalom fuse, 620 front and 200 stab. HG4 7m, JP foil slalom 91, mast rake 2.7 deg. mast base 112 from front screw. 38" lines seat harness. Plenty of TOW is available in 10-18kt.
Advice please......
I'm same as you gaviota, not really sure of correct technique/pressure to angle the board without heading upwind. I try to push down and forward with front foot to push the nose away.
Think back to your days on a long board sub-planning. To get the nose to turn downwind angle the sail more over the nose. To turn upwind lean the sail back over the fin.
Now think about your time spinning out on a slalom board - maybe in weed. To get the board back in conr you pull the back foot in and under your hips. While pushing away with the front foot.
now do both these things while foiling with the windward rail down.
simple 
Select to expand quotegaviota said..
Thank you Berowne for the very helpful and perfectly timed video. For me most important take away is that foiling flat is comfortable but ultimately limiting. So I am working on angling the board to windward to hold the nose down and ignoring the sirens advising mastfoot forward.
But I have a challenge and am looking for advice.
When I reach and angle the board to windward I round up and end up foiling fastish upwind, it is good and stable but the opposite of what I am aiming for which is going fast across or slightly downwind. The only way I am succeeding reaching/broad reaching is with the board flat and back foot out - not good for all the reasons you explain so well in your video (you reach a point where you cannot lean far enough forward to hold the foil down in a gust)
My set up is F4 100 slalom fuse, 620 front and 200 stab. HG4 7m, JP foil slalom 91, mast rake 2.7 deg. mast base 112 from front screw. 38" lines seat harness. Plenty of TOW is available in 10-18kt.
Advice please......
I used to have problems keeping the foil in the water in gusts, that was solved when I matched the wing and sail to the conditions. So if you have a problem keeping the foil in the water first try reducing the shim on the stab. if possible, 0.0 is best for speed though on my AFS W95 foil, and then use smaller wings first so you are still going fast, and then reduce the sail size last. I went from the AFS F1080 cm2 wing and Aerotech Freespeed 5.8 m2 sail in 15-24 knots with heart racing runs on the borderline of foiling out and of course foiling out too, to a F770 cm2 wing and Freespeed 5.8 in 14-18 knots where I do have to pay attention to not foil out but it is not difficult, and a S670 cm2 wing and Aerotech Phantom 4.5 sail in 18-30 knots where I rarely feel even close to foiling out upwind, crosswind, and even downwind going really fast! (but have only tried the downwind runs on the S670 in 18-20 max knots so far).
Select to expand quoteberowne said..
Think back to your days on a long board sub-planning. To get the nose to turn downwind angle the sail more over the nose. To turn upwind lean the sail back over the fin.
Now think about your time spinning out on a slalom board - maybe in weed. To get the board back in conr you pull the back foot in and under your hips. While pushing away with the front foot.
now do both these things while foiling with the windward rail down.
simple
Nicely explained. I think I'm doing all that with the rig and front foot, but I'm ignoring my back foot. Sounds like putting the back strap back on might help with the gymnastics...
Back foot locked in is "safer" and more controlled. until it isn't.
I "practiced" by putting my back foot inboard, and pushing my heel against the strap. This way I knew I had the right leg spacing but still felt a bit safer with the back foot inboard and not locked in the strap.
Then when I'd done a few runs at speed and felt confident I would try another run in the strap.
Now of course I come out of a gybe and put the back foot in the strap without hesitation.
Good explanation of why we should sail with neutral harness lines. or fairly far back relative to most people feel is safe!
Too far forward and when you sheet in the power goes onto your back foot just when you do t want it too. www.seabreeze.com.au/forums/Windsurfing/Foiling/Harness-line-position-and-effect-on-mast-foot-pressure
Thank you Berowne et al, the description of regaining direction after a spin out is very helpful, never tried pulling with the back leg before as I push with the front. Yesterday was a 10-12kt day and I started to get some deep downwind runs in straps hiked out with the board angled. After putting the mast further back in 5mm increments I used the push/pull technique and I was amazed at the power and controlled speed as I bore away for some downwind runs in the straps, railed and hiked - now to build confidence and skill in doing this in higher windspeeds.
Next challenge, how to get back foot out of the strap at speed as I prepare to jibe without losing control, there is a lot of pressure at speed through both legs now.... at the moment I head up to slow a little then take it out but that can mess up my jibe entry - advice?
Next next challenge how to get my back foot back into the strap on the happy occasion of a full on air jibe.... when I come out I am going too fast to get my back foot in, partly fear and partly inability to unweight the rear leg when flying. So I bring the board down, head up, get the rear foot in pump up, hook in and off I go. Exhausting.... again advice sought - do I need a more front foot weighted set up to make it easier to unweight the back foot? Bigger front wing for more stability (760 instead of 620?)
I'm told I my JP foil slalom pro 91 board vintage 2020 (Blue) makes life hard for me since the straps are
very much outboard, but I guess that is where you need to be.
Gaviota, good question on the rear strap entry. I find it much less difficult on inboard strap (71cm wide) free ride foil to get in and out of the rear as needed. I struggle greatly with a 95cm wide race board. The only method that I've found is to migrate the rear in a pump. But I see pros get in the rear so quickly on race setups I wonder what else I can do. I definitely need help too.
At speed you definitely need to pick the right moment to move the back foot. if Blackfoot pressure sends nose up a lack of pressure will send the nose down. So move your foot when the board is already heading up a bit. Then after the gybe try to get your feet settled ASAP! Gybe speed is typically under 20 knots so this is the best time to get resettled. Before you get up to 30 knot top speed. 
Gybes should be in a different thread.
www.seabreeze.com.au/forums/Windsurfing/Foiling/Foil-Racing-Windfoil-Gybe-Technique
Went for speed today. Haven't broken my PB (but less than a knot from it) but I felt more in control after reading this thread and others. Lots of room for improvement. Not impressive compared to 30kts but I think I now know what to do to go faster.
My back foot was out and more inboard, but I was able to hunt around a bit for power and found the groove where it felt best and was able to quickly glance at my watch. There was a point where I felt I was just pushing more and had more power in the sail but it took a little hunting.
A big thing I'm noticing is how limited I have been by site selections. Today, I felt more on tap if I changed stance, but I ran out of deep water. Gusts weren't that strong but the water was flat. I think I need to try at a different spot, hopefully will be able to try it soon. Another bay spot was way too choppy and scary for runs. There's an intercostal area that is deep enough and is much less choppy, with tons of room, so I'll need to try there. At these foil speeds you really run out of room quickly.
You can see the sandbar coming in at the bottom of the run. I got off the accelerator and tried to drop slowly onto the water. I was touching the weedy bottom at the end.
9.0/115+/725 with +0.5 shim.
Looks like the wind sensor was reading 12-14kts during this run.
Select to expand quoteaeroegnr said..
Went for speed today. Haven't broken my PB (but less than a knot from it) but I felt more in control after reading this thread and others. Lots of room for improvement. Not impressive compared to 30kts but I think I now know what to do to go faster.
My back foot was out and more inboard, but I was able to hunt around a bit for power and found the groove where it felt best and was able to quickly glance at my watch. There was a point where I felt I was just pushing more and had more power in the sail but it took a little hunting.
A big thing I'm noticing is how limited I have been by site selections. Today, I felt more on tap if I changed stance, but I ran out of deep water. Gusts weren't that strong but the water was flat. I think I need to try at a different spot, hopefully will be able to try it soon. Another bay spot was way too choppy and scary for runs. There's an intercostal area that is deep enough and is much less choppy, with tons of room, so I'll need to try there. At these foil speeds you really run out of room quickly.
You can see the sandbar coming in at the bottom of the run. I got off the accelerator and tried to drop slowly onto the water. I was touching the weedy bottom at the end.
9.0/115+/725 with +0.5 shim.
Looks like the wind sensor was reading 12-14kts during this run.
Damn that looks like a short run!
Select to expand quoteberowne said..aeroegnr said..
Went for speed today. Haven't broken my PB (but less than a knot from it) but I felt more in control after reading this thread and others. Lots of room for improvement. Not impressive compared to 30kts but I think I now know what to do to go faster.
My back foot was out and more inboard, but I was able to hunt around a bit for power and found the groove where it felt best and was able to quickly glance at my watch. There was a point where I felt I was just pushing more and had more power in the sail but it took a little hunting.
A big thing I'm noticing is how limited I have been by site selections. Today, I felt more on tap if I changed stance, but I ran out of deep water. Gusts weren't that strong but the water was flat. I think I need to try at a different spot, hopefully will be able to try it soon. Another bay spot was way too choppy and scary for runs. There's an intercostal area that is deep enough and is much less choppy, with tons of room, so I'll need to try there. At these foil speeds you really run out of room quickly.
You can see the sandbar coming in at the bottom of the run. I got off the accelerator and tried to drop slowly onto the water. I was touching the weedy bottom at the end.
9.0/115+/725 with +0.5 shim.
Looks like the wind sensor was reading 12-14kts during this run.
Damn that looks like a short run!
It definitely was. I tried the newer spot on fin, as it has been very windy and lower tide, and I could just stay on the gas much longer. Hopefully it'll be good foiling conditions soon as there's way more room.
Select to expand quoteberowne said.. Good explanation of why we should sail with neutral harness lines. or fairly far back relative to most people feel is safe!
Too far forward and when you sheet in the power goes onto your back foot just when you do t want it too. www.seabreeze.com.au/forums/Windsurfing/Foiling/Harness-line-position-and-effect-on-mast-foot-pressure
I have to say in my experience forward harness lines are better for preventing foil outs because they give you more range for sheeting in/out, have tested that in 25-30 knots on a Phantom 4.5 sail and AFS S670 cm2 wing, was definitely overpowered in the 30 knot gusts, but sail automatically sheeted out when they hit me, did not get even close to foiling out. With centered lines you cannot sheet out as far or as easily, and then when those gusts hit you you breach
