Since some posters here like to rag on my opinion about favoring the back foot for foiling, let me explain some things about this.

All foils are lifting bodies. This means that the faster the speed the greater the lift. Combine the up lift of the main wing with the down lift of the stab, and the increasing speed effect is magnified. This is basic physics.

So, if your feet feel balanced at a board speed of 12 mph, you will feel front-foot-heavy at 20 mph. This makes it too easy to breach at 20 mph.

So, what to do?

Start with a heavier back foot at 12 mph. Then as your speed increases, the lift increases, and your feet will go more into balance. It's the feeling as if your lifting wing is "effectively" moving forward with increasing speed. We know it does not, but it "feels" like it does.

I balance and shim my gear to have a somewhat heavy back foot at 12 mph board speed. When my board gets up to the 18 mph that is my usual cruising speed, the lift has increased to where both feet are balanced.

The sail plays a role, too. A properly designed and rigged sail (especially foiling sails), will push down with increasing wind load. Such foiling sails as the Flyer have more cloth up high and rig to a tighter leech up high to help push down. The Fringe has this, too, as do some other popular sails for foiling. This "pushing down" helps to mitigate the heavier front foot at higher board speed. Note that people talk about moving the mast base forward in strong or gusty winds. Same effect. Increase the mast base pressure to take some of the load off the front foot.

So, if you are constantly breaching, or feel like you are constantly on the dangerous ragged edge of breaching and catapulting, or burning out your front leg, try moving things or changing things to bias your stance more to back foot heaviness at slow speed. You can then "haul" your foil up into flight at 12 mph board speed, and feel it all come into balance as your board speed increases.

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segler said..

I look at the foil and shim setup differently. You say:

"All foils are lifting bodies. This means that the faster the speed the greater the lift. Combine the up lift of the main wing with the down lift of the stab, and the increasing speed effect is magnified. This is basic physics."

However, you are ignoring the effect of angle of attack on the lift from a foil wing. As you go faster and stay in level flight you adjust the angle of attack (the board becomes slightly more nose down) so that the lift remains constant to match your weight. At slow speeds you increase the angle of attack (i.e. nose slight up) to get sufficient lift.

It seems to me that the lift actually remains fairly constant. What changes most is the amount of drag. Drag on the foil at higher speed causes the nose to be pulled down due to the forward thrust from the sail not being in line with the drag. That happens with all sails because the centre of effort of the sail is way above the backwards drag force on the foil.

In my view the job of the stabiliser is to balance out the drag at high speed so that you don't have to use excessive rear foot pressure to keep things in balance. I setup the shimming of the stabiliser to minimize the balance change across foiling speeds. If I feel the foil becoming more front footed as speed increases I know the stabiliser is creating too much downforce and I reduce the shimming. And likewise increase the shimming if it's more rear footed as speed increases. Once I've got the foil relatively stable for changes in speed I'll then work on it's position (i.e. move foot straps, mast foot, foil tracks etc).

As you say, I think you're always going to be rear footed at low speeds but with the right stabiliser and shimming you can maintain a fairly constant front/rear foot balance from 12 knots to 20+knots.

Yeah everyone is going to be back footed trying to get going when its light. This is the advantage of setting things up so that when powered most weight is on the front foot.

I reckon weight distribution when powered varies lots on the type of equipment you ride.

The only mistake in this sport is to not vary settings during the same session everynow and then

I like your comments about drag. Good input.

One other reason why I like more back foot at low speeds is that I can pump the board up to a slow plane before lifting it up into flight. Everything is under control, nice and easy. This also lets me come down off the foil, but keep planing, during jibes.

Being an Engineer I find this discussion educational and makes me want to try using shims and moving the mast base around to explore the potential for even more fun on a foil. However I ride without foot straps, and can not relate to not having a pretty close to a 50/50 weight balance between my feet no matter what. Sure I do shift my weight while riding but if during any reach I seem to be applying constant pressure on one foot or the other I simply move my feet to were I feel balanced.

I admire the skill folks display with huge weight shifts between feet while foiling; I am just not good enough to do the same. I took the easy way out and stopped using foot straps. Straps definitely have their advantages but I have more fun without them. And defiantly spend zero time adjusting foot straps, shims, foil or mast positions.

Have fun foiling

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Hess said..
Being an Engineer I find this discussion educational and makes me want to try using shims and moving the mast base around to explore the potential for even more fun on a foil. However I ride without foot straps, and can not relate to not having a pretty close to a 50/50 weight balance between my feet no matter what. Sure I do shift my weight while riding but if during any reach I seem to be applying constant pressure on one foot or the other I simply move my feet to were I feel balanced.

I admire the skill folks display with huge weight shifts between feet while foiling; I am just not good enough to do the same. I took the easy way out and stopped using foot straps. Straps definitely have their advantages but I have more fun without them. And defiantly spend zero time adjusting foot straps, shims, foil or mast positions.

Have fun foiling

yeah

I will have to pay attention to my weight distribution when i ride strapless. My guess is subconsciously I just move my back foot around versus adjusting my body weight to control pitch.

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segler said..
I like your comments about drag. Good input.

One other reason why I like more back foot at low speeds is that I can pump the board up to a slow plane before lifting it up into flight. Everything is under control, nice and easy. This also lets me come down off the foil, but keep planing, during jibes.

With a proper setup at planning speed you won't come off foil. With an incorrect setup you'll get the behavior you describe.
Should be able to gybe on the foil with the leeward foot just behind the front strap.

This is very good information but it seems there are other factors when someone switches to a race foil. It seems that when one gains good speed on a race foil set up, it is easier to put pressure through the harness and foot pressure from the side of board with a riding position similar to regular windsurfing. The stance is different for freeride foil versus race foil. When one gains speed on a race foil with this positioning and higher velocity, ride becomes easier to control despite it is scary since it is faster. It is almost similar to riding a bike when you go faster, you could ride without holding handlebars but the speed allows controlling your direction with minimal change in body position. I am trying to push myself to learn this skill currently on a IQ foil and I found it difficult to learn that despite I felt very comfortable riding low/medium aspect freeride foils. So far, I have not seen any discussion regarding this aspect of foiling. I hope some of you engineers or physicists or experience race foilers could give some perspective on the techniques of riding race foils.

SA_AL, Berowne's got some good info here on his F4 foil as he pushed towards 30kts: www.seabreeze.com.au/forums/Windsurfing/Foiling/F4Foils-Tuning-Tips-Towards-30-knots-?page=1

I'm still working at it and I've had some humbling windsurfing experiences lately, but it really seems like in both straps, staying sheeted, and hiking out further to counterweight for gust control is the way. For a while I was very over-top of the board and I would lose control and freak out in gusts. This was from my own general inexperience as well as habits from freeride foils coming over. I'm still working up the balls to do a full send and push it further, my top is just a little over 22kts but getting faster.

But, this is much more comfortable now than how I was sailing it before. That sail lean kills power when I need to, in fact, sometimes kills it a bit too much in lighter conditions.

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aeroegnr said..
SA_AL, Berowne's got some good info here on his F4 foil as he pushed towards 30kts: www.seabreeze.com.au/forums/Windsurfing/Foiling/F4Foils-Tuning-Tips-Towards-30-knots-?page=1

I'm still working at it and I've had some humbling windsurfing experiences lately, but it really seems like in both straps, staying sheeted, and hiking out further to counterweight for gust control is the way. For a while I was very over-top of the board and I would lose control and freak out in gusts. This was from my own general inexperience as well as habits from freeride foils coming over. I'm still working up the balls to do a full send and push it further, my top is just a little over 22kts but getting faster.

But, this is much more comfortable now than how I was sailing it before. That sail lean kills power when I need to, in fact, sometimes kills it a bit too much in lighter conditions.

Thanks for sharing the Berowne's info. I think for me some of most important factors that will integrate during my transition to race foil are
You can send the nose down by sheeting IN the back hand, which seems counter intuitive if your about to breach! Don't sheet out too much... ever!

....keep the harness pressure pretty stable.

Reaching at speed can require an amazing amount of downforce, Sometimes I think I've had about 70% of my weight through the harness lines a few times, which can hurt with a waist harness, and is why I prefer a seat harness.

Couple things.

Yes, sheeting IN actually increases mast base pressure. If your foil is starting to come up, sheet in to push it back down. This is one of those muscle memory things we all have to learn with this "new" wrinkle on the windsurfing sport.

Grant is right. If you are front-foot-heavy, to jibe you place your back foot on the opposite side just behind the front footstrap. Then, when you switch feet it is easy to get the new front foot right into the strap. If, like me and BP with back-foot-heavy trim, you jibe you have to keep the back foot further back to keep things in flight during the carve. This is how we used to jibe when on a fin.

Foiling strapless is great. You have no preconceived notions about where to place your feet. You just find the balance instinctively and foil off into the sunset.

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SA_AL said..

aeroegnr said..
SA_AL, Berowne's got some good info here on his F4 foil as he pushed towards 30kts: www.seabreeze.com.au/forums/Windsurfing/Foiling/F4Foils-Tuning-Tips-Towards-30-knots-?page=1

I'm still working at it and I've had some humbling windsurfing experiences lately, but it really seems like in both straps, staying sheeted, and hiking out further to counterweight for gust control is the way. For a while I was very over-top of the board and I would lose control and freak out in gusts. This was from my own general inexperience as well as habits from freeride foils coming over. I'm still working up the balls to do a full send and push it further, my top is just a little over 22kts but getting faster.

But, this is much more comfortable now than how I was sailing it before. That sail lean kills power when I need to, in fact, sometimes kills it a bit too much in lighter conditions.

Thanks for sharing the Berowne's info. I think for me some of most important factors that will integrate during my transition to race foil are
You can send the nose down by sheeting IN the back hand, which seems counter intuitive if your about to breach! Don't sheet out too much... ever!

....keep the harness pressure pretty stable.

Reaching at speed can require an amazing amount of downforce, Sometimes I think I've had about 70% of my weight through the harness lines a few times, which can hurt with a waist harness, and is why I prefer a seat harness.

SA-AL, apologies in advance if this is common knowledge but anyway...
(For background, equipment is JP135 Hydrofoil epoxy, SB GTR with 800/650 front wings, 255-2 rear 95+ fuse, sails are mostly 4 cam windsurfing race sails from 6.2-8.4m)

From my experience and talking to other foilers, going fast with a race foil on a reach (say >22kn) is challenging to control the ride height. The natural inclination is to either head up wind to reduce speed or bear away to reduce wind speed past the sail. I certainly agree with others about keeping mast foot pressure to control ride height and a have been using a seat harness to help with that. The other thing from watching the pros is to lean the board onto the windward rail as you get powered up. This does a couple of things. Firstly wind pushing down on the nose of the board to counter the lift, and secondly reduces the vertical lift from the foil because of the angle.

I am in both footstraps for the reach. I took the rear straps off for a few sessions. As other have said, definite freedom of weight transfer by moving back foot around, great for gybing, BUT hard work for fast reaching. I was actually cramping up in the calves from trying to grip the board curling my toes when reaching/going upwind. Again, this is only for fully powered up, faster sailing on a race foil, not cruising.

You do have to be pretty committed because you are leaning out, heavily dependent on the harness (yes, at least 70% of weight), so much more like a conventional windsurfing position. And it feels scary. Then keep a very close eye upwind for the gusts - you can either shift weight forward if you want to send it, angling the board more on upwind rail, or the easier option is to point further upwind as the gust hits.

And from the advice above, I probably need to move the harness lines back a fraction and sheet in even more!

Since a race foil places the front wing further forward of the mast, the geometry is changed also. In order to balance it on a reach, or with a small sail (5.0-7.0), you have to stand further forward of where most boards place the forward-most footstrap positions. I know this from experience with a Moses race foil under several production foil boards with stock freeride footstrap positions. I have to foil strapless with my feet in front of the footstraps, even with the sail mast base fully forward.

The solution in my case is a custom board with the footstraps 5 inches further forward of the usual freeride positions. I will dedicate this board to foiling only with the race foil.

My Fanatic Stingray LTD 140 and Exo FF 132 will continue to be the rides for my freeride foils.