No, I have never used a mast base extender since the stock tracks have been just fine for balancing my gear. I use single-bolt bases.
The front wing is a lifting airfoil body. Therefore, every foil in existence lifts more as the speed increases. No secret there. The faster you go, the more front foot pressure you need to keep it balanced.
I always tune my gear to have equal front and back foot pressure at 20 mph boat speed. That means I am back-footed at lower speed. Something like 40:60 (front:back) at 14 mph boat speed. It works. I like it. It helps to prevent foilouts in virulent gusts. Bruce Peterson steered me in this direction in 2017 when I got started. The downside is that you have to work harder to prevent touch downs during jibing. The answer to that is simple: just step further back. No mystery.
Select to expand quotesegler said..
No, I have never used a mast base extender since the stock tracks have been just fine for balancing my gear. I use single-bolt bases.
The front wing is a lifting airfoil body. Therefore, every foil in existence lifts more as the speed increases. No secret there. The faster you go, the more front foot pressure you need to keep it balanced.
I always tune my gear to have equal front and back foot pressure at 20 mph boat speed. That means I am back-footed at lower speed. Something like 40:60 (front:back) at 14 mph boat speed. It works. I like it. It helps to prevent foilouts in virulent gusts. Bruce Peterson steered me in this direction in 2017 when I got started. The downside is that you have to work harder to prevent touch downs during jibing. The answer to that is simple: just step further back. No mystery.
Thanks segler, it was foiling gybes that got me onto changing the mast base position, because I was limited to when I would practice my gybes to when I was balanced or front footed, with the mast base extender I noticed right away that my rear foot was farther forward even when in the lulls and that I stayed up in the lulls even though I was going slow. Without the extender in lighter winds, my back foot was as far back as I felt comfortable with and that was with my foot just on the rear-side of the rear foot pad.
What I learned with the mast base extender is you do not know the balance point for the mast base until you have gone past the balance point! Anyone trying this should be careful, since once you go past the balance point the board nose will want to lift up while powering up on the water, AND the kit will be very sensitive to gusts while up on the foil making catapults a real risk. My advice it to NOT hook in when testing out aft positions of the mast base, until you have gusts up on the foil and know how the kit responds to them. But really, if the nose comes up while powering up on the water, just stop and move mast base forward until board stays level while powering up, before getting up on the foil.
Select to expand quoteSandman1221 said..
What I learned with the mast base extender is you do not know the balance point for the mast base until you have gone past the balance point! Anyone trying this should be careful, since once you go past the balance point the board nose will want to lift up while powering up on the water, AND the kit will be very sensitive to gusts while up on the foil making catapults a real risk. My advice it to NOT hook in when testing out aft positions of the mast base, until you have gusts up on the foil and know how the kit responds to them. But really, if the nose comes up while powering up on the water, just stop and move mast base forward until board stays level while powering up, before getting up on the foil.
Foiling and dealing with Gusts:
In 'my neck of woods" (or water) we sometimes have days with SW wind that creates what I call "Zero to Hero" conditions. There is no Base Wind. Just Gust shooting often from 0 to 30mph.
Therefore we developed many strategies to deal with Gusts for Foiling:
a) using sails with power up on top - specific sails and/or rigging them specific ways for no lose leech.
When gust hits you, the power on top creates MBP and compensates for the foil increased with speed lift
b) mix match mast pieces - top from longer / stiffer mast, bottom piece from shorter / flexier mast, adding round tube shim between (for now different diameters). The credit for this idea goes to Jonathan R & Glenn R. They were the first to share that idea on NW Windtalk Forum.
c) Using stiffer top - longer masts - that is why for example I have been rigging Loft Oxygen 10.8cm designed for 520 mast on older 550 Gaastra Ignition Race 100% Carbon Mast. There is no lose leech on that sail. Plenty of power on top and outstanding response (bounce back)
Kudos go to "Segler" - Rick M for selling that mast to me. 1000s of joyous miles on it !
d) Using Race / HA Foils with stabilizer shimmed for speed, not lift - when gust hits you, the foil accelerates forward without "elevator effect" (unlike in LA larger Shovels), also there is no "Anchoring effect" both Induced (AoA) and Viscous (HA efficiency) Drag is less.
Please note that Lift is a function of AoA (Angle of attack). AoA of Front wing is impacted by several factors but greatly by Stabilizer Angle (fuselage length acting as a "lever"). That is why it acts like Airplane trim. But keep in mind Airplanes also can fly upside down.
BTW. When Slingshot released i84 shovel and recommended to use 48cm stab, I mounted it the way 42cm was before (there was no info available that is should be mounted up side down). I went on the water and no force stomping on the back of the board could lift me out of the water even with increased speed.
Yea, we can joke that Slingshot designed i84 with 48cm stab for speed first 
If anyone is interested in more details, just use search NW Windtalk forum for specific "key words". We had many detailed discussions with pictures in the past.
here is for "elevator effect":
groups.io/g/nw-windtalk/search?q=%22elevator+effect%22
Cheers
MarekS
Got out today on Freespeed 5.8 and AFS S670 cm2 wing in 15-18 knots, using two bolt mast base extender at about 41" because I was going faster than previous time at 40.5" with F770 wing. Again noticed that my rear foot was more forward and that it was just easier, board nose did come up a little while on the water and powering up but that helped in waves, did some fast down wind runs and it felt really good and stayed up in a lull, whereas before at 42-3/4" would of come down in the lull with the S670 wing which is not pump-able (pumping the sail down wide does work for me either). So it is a sliding scale for wind pressure and foil speed going from about 40-1/2" in 12-14 knots to maybe 42-1/2" max at 30 knots, but last time in those conditions I thought 42-3/4" (max aft position using factory track and single bold base) was good will have to see on next 25-30 knot day. Big question is in 8-10 knots, will it help to have it back further than 40-1/2", I certainly can be back footed in those conditions at 42-3/4". And of course waiting for North wind to see how it affects my foiling gybes to have mast base further back than 42-3/4", now that will be interesting!
So with a single bolt mast base all the way back in the mast track my rear foot was on top of the rearward row of foot strap screw holes, so a rear foot strap was too far forward and I removed them early on.
But with the mast base extender my rear foot is now between the two rows of foot strap screw holes, so now the rear foot strap should fit good, will have to put back on and see.
Got to finally try out my 8.0 Freespeed and AFS F1080 cm2 wing with the mast base extender, it worked great at 40.5" and was pretty balanced on my feet, got up in some very light gusts that in the past would either of been not enough, or I would of been very back footed. But had not been out on 8.0 since last Summer when I had just started using 490 mast instead of 460. Wind picked up and put on AFS F770 cm2 wing and tried moving mast base back further because was not getting up easily but that made the sail very heavy on the rear hand, tried moving it farther forward and that did not seem to help either, so went back to 40.5", wind picked up more and should of tried the S670 cm2 wing with the 8.0 but forearms were getting tired! 8.0 Freespeed with Epic 100% 490 mast is definitely heavier than my next sail size a 7.2 Freespeed with Z-speed 100% 460 mast. I want to say the 8.0 is a lo easier to handle in higher winds with the 460 mast versus the 490 mast which really increases the power closer to a whole sail size.
What I did find is that I could adjust the two bolt mast base extender with Streamlined two bolt mast base while in ab deep water, was easy to remove mast from tendon and then laid bottom of mast/sail across both front foot pads, facing the wind, while I adjusted mast base extender position facing the wind on the leeward side of board.
That Goya/Freespeed with the adapted mast base really was foiling up early in the lighter air.
By the time we quit, if you wanted to stay on the 8.0, you could have just put a fin on the thing - 18-22 with some real gusts. I was down to a 5.7 and would have been happier on 5.2. The Palma Sola Northside spot is a riot on a fin because it's so flat - waterski jibes.
Select to expand quoteAwalkspoiled said..
That Goya/Freespeed with the adapted mast base really was foiling up early in the lighter air.
By the time we quit, if you wanted to stay on the 8.0, you could have just put a fin on the thing - 18-22 with some real gusts. I was down to a 5.7 and would have been happier on 5.2. The Palma Sola Northside spot is a riot on a fin because it's so flat - waterski jibes.
Good point AWS, I just always forget to do that, even though I have the fins in my vehicle in the rear seat foot well! But the AFS S670 cm2 wing would of been fun to try too, but have never used it on the 8.0 in the past and was so focused on the mast base extender adjustments did not think of it at the time. Have used S670 with Freespeed 7.2, that was a blast!
Will move fins to back of vehicle with wings. But the last time I was on the Freespeed 9.0 with min. downhaul and F1080 wing and winds picked up I switched to a fin because the wind increased to 16-18 mph. I remember the whole board was pushed underwater by the sail pressure, so stopped then. Called up Bigwinds where I got the board and was told the Bolt 135 was a "light wind" board. Guess I could also increase downhaul next time too for fin or wing, since I usually run my sails with min. downhaul.
Finally got to test mast base extension out in 18 knots with 4.5 Phantom sail and AFS S670 cm2 wing. The maximum forward position of the two bolt extension is 41-3/4" (so 1" further aft than a 1-bolt mast base in factory track). In the past in 18-30 knots that sail/wing combo felt balanced at 42-3/4" with a 1-bolt mast base all the way back in the track BUT my rear foot was on top of the rear foot strap aft screw holes. Yesterday with the mast extender set all the way forward at 41-3/4" the kit felt balanced in 18 knots BUT then my rear foot was "between" the rear foot-strap screw holes which means I could use the rear foot straps. I have never used rear foot straps foiling because they were too far forward, and have noticed I move my foot from the rail to center of board depending on what I am doing, downwind speed runs foot is on center of board.
So looks like mast base extender works good for winds from 8-18 knots. What I need to remember is if for the conditions and kit I am back-footed, is too stop and move mast base backwards, easy to do in chest deep water with the Streamlined 2-bolt Quick-Lock Universal.
Well it looked good for my 7.2 Freespeed and AFS F1080 wing, a few scattered whitecaps, but by the time I got on the water the two kite foilers got off, never a good sign, cause they are my canaries in the coal mine when it comes to wind dropping. Set mast base extension to 40" and had fun for a while, then whitecaps faded away and I was in 8.0 conditions at the minimum. But decided to move mast base all the way back to 39.5", and went back out. Took some coordinated sail, and then added foil, pumping and I got up for a few good long flights, was really amazed doing it with the 7.2. Rear foot was between the foot strap screw holes and felt balanced, definitely not back footed like I normally would of been. So for light winds in the ~9-10 knot range the mast base set to 39.5" was great! Only bad news is now I wonder if with my 8.0 in lighter conditions if it would help to have more extension! Will see, scrap starboard is cheap.
And I was able to adjust the two bolt mast base extender in chest deep water with the sail attached, had to wiggle it a little, but was easy to do once both screws were almost unthreaded from the nuts.
Select to expand quotemareks360 said..
I think there are many major (dominant) factors that affect mast base placement for foiling and the placement will vary greatly even for one sailor:
1) Sail size (MBP)
2) Sail weight (MBP)
3) Sailor Weight
4) specific Front Wing position (that you stand over) you are using at the time
5) footstraps position
6) Are you in winds closer to 100% foiling or 50%/50% Slogging ?
7) Board type (weight/volume distribution)
So for example for "Heavy Dude" going with larger sails in relatively lighter winds the double bolt quick disconnect chinook plate goes max aft (for max lift) therefore distances (between center of chinook plate and center of first foil mast screw) for my boards I use for foiling look like this:
Exocet RF91 (155L) 113.5cm
SB Go 200 113.5cm
SB FW167 (182L) 109.5cm
Exocet RF81 109.5cm
SB Go 180 109.0cm
SB Race 100 107.5cm
SB Race 100 (mod) 99.0cm (See the Note 1)
Slingshot Flyer 280 85.0cm
Note 1: For picture what Modified Chinook Plate Extender (moving MB aft beyond track) looks like, check:
www.seabreeze.com.au/forums/Windsurfing/Foiling/Impressions-of-new-Windfoil-boards-for-super-heavyweights#2809771
Interestingly enough, when you have much more lightweight person going with much smaller sails in stronger winds like Darius L (Racing in Winduro 2019), on the same SB FW167 Board, He moves the plate max forward and actually uses the Modified Chinook Plate Extender Forward !
BTW: Darius made curvature to support to the bottom of the board. Like in the picture below from 2019 Winduro.
I actually shaped (shaved off) thick plywood piece to remove that curvature to use that Mod on SB Race 100 (see in the link above) for the area of flat surface on the board.
Experiencing similar situation to Darius L. Also a lightweight. Have slowly been moving the mast base more forward. Initially the mast was positioned as far back as the track allowed. The supposed ideal ~42" position. Improved smoother (level) flight in both choppy and gusty conditions. Haven't really noticed any added effort to foil up. So many variables in "proper" positioning of the wing and stab. Add body mass as variable. Has been a bit of a trial and error process.
Select to expand quoteOldGuy3 said..mareks360 said..
I think there are many major (dominant) factors that affect mast base placement for foiling and the placement will vary greatly even for one sailor:
1) Sail size (MBP)
2) Sail weight (MBP)
3) Sailor Weight
4) specific Front Wing position (that you stand over) you are using at the time
5) footstraps position
6) Are you in winds closer to 100% foiling or 50%/50% Slogging ?
7) Board type (weight/volume distribution)
So for example for "Heavy Dude" going with larger sails in relatively lighter winds the double bolt quick disconnect chinook plate goes max aft (for max lift) therefore distances (between center of chinook plate and center of first foil mast screw) for my boards I use for foiling look like this:
Exocet RF91 (155L) 113.5cm
SB Go 200 113.5cm
SB FW167 (182L) 109.5cm
Exocet RF81 109.5cm
SB Go 180 109.0cm
SB Race 100 107.5cm
SB Race 100 (mod) 99.0cm (See the Note 1)
Slingshot Flyer 280 85.0cm
Note 1: For picture what Modified Chinook Plate Extender (moving MB aft beyond track) looks like, check:
www.seabreeze.com.au/forums/Windsurfing/Foiling/Impressions-of-new-Windfoil-boards-for-super-heavyweights#2809771
Interestingly enough, when you have much more lightweight person going with much smaller sails in stronger winds like Darius L (Racing in Winduro 2019), on the same SB FW167 Board, He moves the plate max forward and actually uses the Modified Chinook Plate Extender Forward !
BTW: Darius made curvature to support to the bottom of the board. Like in the picture below from 2019 Winduro.
I actually shaped (shaved off) thick plywood piece to remove that curvature to use that Mod on SB Race 100 (see in the link above) for the area of flat surface on the board.
Experiencing similar situation to Darius L. Also a lightweight. Have slowly been moving the mast base more forward. Initially the mast was positioned as far back as the track allowed. The supposed ideal ~42" position. Improved smoother (level) flight in both choppy and gusty conditions. Haven't really noticed any added effort to foil up. So many variables in "proper" positioning of the wing and stab. Add body mass as variable. Has been a bit of a trial and error process.
Oldguy, just note that I move the mast base forward as the wind and board speed increases and move it back as the wind and board speed decreases. In 9-10 knots I have now been putting mast base at 38-3/4" and that really helps to get up and stay up in those wind speeds. In 11-17 40-1/2" is good, 18+ knots 42", 30 knots 42-3/4".
Had a good light wind day (9-10 knots) with no whitecaps to test out mast track extender modified to give 4-1/4" aft adjustment (extra inch), used Freespeed 8.0 sail with min. downhaul and AFS foil F1080 wing with no stab. shim, with mast track extender all the way back was at 38.5" to foil front mast screw, was just barely getting up with sail pumping, but once up was good with pretty balanced weight, in a stronger gust noticed I moved my rear foot forward from center of foot strap to be on top of forward screw holes for rear foot strap, so feels like 38.5" is as far back as needed for 9-10 knots. The factory track only gets mast to 42-3/4" with a single bolt mast base! All those years with my rear foot on top of the rearward screw holes thinking that was good, I guess it was okay, but was back footed a lot in light winds.
