Mast Plate Shimming,huge effect for little $

[Dontsink]

I have a Takuma LOL 1600 full carbon.I love it for winging but i could not make it work for prone foiling.
It felt super draggy paddling into the waves and it would rise like a psycho when dropping in.
I thought it was too big for my 75kg, or that my board (Gong Matata EPS 5.0) had the boxes too far forward for this foil.I had almost given up on surf foiling it.

But reading about how the Kujira riders are shimming their mast plate for increased angle of attack on wave entry with great results made me think that maybe my LOL needed exactly the opposite.
So i made a 4mm epoxy shim(with some carbon to keep it from splintering) and screwed it on for todays session,thick side at the front to reduce angle of attack when paddling in.

Wow, worked like a charm.Easy paddle in on foamies or unbroken waves, nice controlled rise.Perfect

For winging i like it unshimmed, as the rise on foil is very progressive compared to surf foiling.

This mast plate shimming is a huge factor , so if anybody is having trouble with a particular board/foil/activity combo i encourage them to experiment with this before spending money on stabs,foil wings etc...

3 to 4mm has a huge effect, i would not try more than this as you would need longer screws and even with this the angle would put stress inside the rail inserts. Foilmount makes swiveling hardware that allows for big angles if needed.

[PonoBill]

Absolutely true for a lot of boards, especially those with some tail rocker. I've been shimming my mast plate since I started foil surfing. I don't agree that 3-4 mm is a maximum. Whatever it takes to get the center of the total incidence angle aligned with the centerline of the board will make it much easier to catch waves. On my L41 and later on my Jimmy Lewis starter board (after I foolishly added mast tracks to it, Jimmy set up the Tuttle to be correct to start with) that was 10mm (1/4") in the back--that transformed the board. If your shim is hard enough and matches the contour of both the bottom of the board and the foil plate (in other words, it has a gradual taper and extends all the way from back to front) the mechanical stresses aren't that much different. Just be sure to use screws long enough to engage the threads for five full turns at full tightness (the standard for max strength of screws in the size range we use is five threads engaged). When I got my Flying Dutchman board I didn't like the plate angle even though Mark makes a channel in the bottom of the board to mostly eliminate the tail rocker. I was using some thick washers to shim the plate (my fabrication capabilities are very limited on Maui) and I could feel some wobble. Junya gave me a 1/4" shim that Mark had made for him and the wobbles went away.

It's not quite so vital with wingfoiling, but when you see someone foiling along with the nose of the board waving around higher than the tail, it's obvious that they've either got some tail rocker or too much total incidence angle.

Dontsink, if your board is flat bottomed and you're shimming the front of the plate, it's possible your real problem is excessive total incidence angle between the stabilizer and the wing, though I can picture some situations in a wave where having a negative overall AOA would be helpful. I'd measure the total incidence angle, either with an angle gauge or using Admin's method, if it's more than 2-3 degrees you might shim that down. If you do, you'll likely be happier with the performance both for surfing and winging.

[Dontsink]

10mm is a big shim!, nice to know that it works OK, what worries me with bigger angle shims is not the shim(works in compression only) or the screws but the angle you are forcing on the sliding inserts inside the plastic box rails.They will have all the pressure concentrated on the front or back end of each slider, not ideal.
But if yours has not gone bust i guess there is a lot of leeway.

Foilmount sells hardware that will work up to 3* shim ,they have a swivel that will always align the surfaces nicely.
Anyway, i think 1* is a huge change ,3* is mostly meant for surfboard to foilboard conversions where the board has "surf" rocker at the tail.

My Gong has full flat bottom in the back half ,i did try shimming the stab (and different stabs) but in my case it did not help at all.Shimming the mast did the trick.

For comparison,my  Armstrong foils work perfect for prone surfing sans mast shims but do not rise as nicely as the shimless Takuma when winging.

Every manufacturer is setting different angles on their foils, add different rockers and volume distribution on boards plus different disciplines and it can get confusing and frustrating

[PonoBill]

10mm is a big shim!, nice to know that it works OK, what worries me with bigger angle shims is not the shim(works in compression only) or the screws but the angle you are forcing on the sliding inserts inside the plastic box rails.They will have all the pressure concentrated on the front or back end of each slider, not ideal.
But if yours has not gone bust i guess there is a lot of leeway.

No, it's not ideal, but it works (so far). The plates are generally countersunk. If I was worried about the issue I'd just make the fit between screw and hole a little bit bigger so the screw could cock a bit. I lost the 1/4" shim Junya gave me, it's probably in the back of my van in Maui, so I've been using a bogus shim made from hotel card keys, expired credit cards and aluminum tape. It's substantially less than 1/4"--probably about 5mm--but it's okay. I don't detect any wobble. My board feels draggier going after waves but that's probably more the difference between Maui outer reef waves and Cali sand bar stuff. And the nutty currents and backwash at SanO, not to mention all the sudden stops in grass, kelp, and occasionally the bottom.

Do you mean the wizardhat stuff? I like the design of their hardware, but it used to all be 6mm and I like 8mm. I guess I could get over that.  Especially since the Carbon Axis masts I'm using have hole mounts instead of slots, which are a bit of a PITA with standard T nuts.

[Dontsink]

Yup, the wizard hat hardware.
But mind you, i have not used it, just liked the concept

[PonoBill]

I bought the carbon foilmount to build a board with an idea I had that turned out to be more or less what Gong did with their new inflatable. I was going to build a rectangular carbon box around an XPS core with top and bottom handles, foot strap inserts, and a foilmount stuck on the bottom and then wrap it with a lightweight shell that is the floaty parts of the board. A rigid, super strong core for all the stressed elements and super light shell around it. I might still do it some time but I have all the wizardhat stuff sitting at my shop. Unfortunately, all that is in Hood River and I'm in La Jolla.

I just ordered the shim set and hardware so I can get rid of my bogus shim. Thanks for the inspiration.

[Dontsink]

I bought the carbon foilmount to build a board with an idea I had that turned out to be more or less what Gong did with their new inflatable. I was going to build a rectangular carbon box around an XPS core with top and bottom handles, foot strap inserts, and a foilmount stuck on the bottom and then wrap it with a lightweight shell that is the floaty parts of the board. A rigid, super strong core for all the stressed elements and super light shell around it. I might still do it some time but I have all the wizardhat stuff sitting at my shop. Unfortunately, all that is in Hood River and I'm in La Jolla.

I just ordered the shim set and hardware so I can get rid of my bogus shim. Thanks for the inspiration.

Modular boards are something that could be really interesting.
I would like some manufacturer to make a strong carbon box+core like you describe as the system "base" and sell softboard Wing,SUP and Surfoil bodies to fit around it.
We only need serious stiffnes where we stand.

[Califoilia (formerly - SanoSlatchSup)]

Yes, mast shimming depends on whether the board has tail rocker or not, and how much. I had to throw a 1^o shim under the front of the mast on my previous board to get to to fly level instead of nose down, but my next board from the same shaper sets the fuse perfectly level with the deck, so no need to shim that one. Basically shimming the ride angle of the board when the wing is flying level in the water is what you're doing.

[PonoBill]

Yes, mast shimming depends on whether the board has tail rocker or not, and how much. I had to throw a 1^o shim under the front of the mast on my previous board to get to to fly level instead of nose down, but my next board from the same shaper sets the fuse perfectly level with the deck, so no need to shim that one. Basically shimming the ride angle of the board when the wing is flying level in the water is what you're doing.

Actually, you've doing a bit more than that. You're also setting the AOA of the foil--both wing and stabilizer--when the board is in the water. To see what that affects consider an extreme in both directions. Say the foil is pitched down 10 degrees. Obviously draggy as hell, but it also pulls the board down onto the water when you're moving forward. You'll have your work cut out for you trying to get the wing to fly--you'll have to stand on the tail like crazy. And when the AOA reaches zero degrees it will explode out of the water. Now pitch the wing 10 degrees up. Still draggy, but now it's trying to lift the tail. Get the board up to speed and it will come up easily--and stall.

[Dontsink]

Yes, mast shimming depends on whether the board has tail rocker or not, and how much. I had to throw a 1^o shim under the front of the mast on my previous board to get to to fly level instead of nose down, but my next board from the same shaper sets the fuse perfectly level with the deck, so no need to shim that one. Basically shimming the ride angle of the board when the wing is flying level in the water is what you're doing.

Actually, you've doing a bit more than that. You're also setting the AOA of the foil--both wing and stabilizer--when the board is in the water. To see what that affects consider an extreme in both directions. Say the foil is pitched down 10 degrees. Obviously draggy as hell, but it also pulls the board down onto the water when you're moving forward. You'll have your work cut out for you trying to get the wing to fly--you'll have to stand on the tail like crazy. And when the AOA reaches zero degrees it will explode out of the water. Now pitch the wing 10 degrees up. Still draggy, but now it's trying to lift the tail. Get the board up to speed and it will come up easily--and stall.

Yes, the AOA for takeoff (for a given foil) depends on the boards trim on the takeoff "run" and the angle at which the foil is held by the whole support system (rocker,mast,fuse angles).

Ideal board trim position is whatever provides lowest resistance to forward movement .

But the foil system angle to the board we can alter at will via mast plate shimming.

This is just my experience but i think that using the same foil i prefer bigger initial AOA for winging than for surfing.

I think the reason is the very different way we accelerate to takeoff speed with wing power vs wave power.
With wing power the acceleration is very progressive and under our control,like stepping on a gas pedal, with wave power this acceleration is like lighting a rocket. From zero to full blast in a blink.

There is also the fact that when paddling into an unbroken wave you are always battling to keep the nose from rising (pushing it through the ledge).

Anyway, my point is this:
 If your board+foil combo is giving you trouble when getting up on foil experimenting with mast plate shimming can be a very effective solution with little work or money involved,and fully reversible.

Right now this initial AOA is set by the manufacturer, whatever they thought was optimal .If you are mixing board and foil brands and practicing different foil disciplines this AOA can be a hit or miss thing, but easily tweaked via mast plate shimming.

[Califoilia (formerly - SanoSlatchSup)]

Yes, mast shimming depends on whether the board has tail rocker or not, and how much. I had to throw a 1^o shim under the front of the mast on my previous board to get to to fly level instead of nose down, but my next board from the same shaper sets the fuse perfectly level with the deck, so no need to shim that one. Basically shimming the ride angle of the board when the wing is flying level in the water is what you're doing.

Actually, you've doing a bit more than that. You're also setting the AOA of the foil--both wing and stabilizer--when the board is in the water. To see what that affects consider an extreme in both directions. Say the foil is pitched down 10 degrees. Obviously draggy as hell, but it also pulls the board down onto the water when you're moving forward. You'll have your work cut out for you trying to get the wing to fly--you'll have to stand on the tail like crazy. And when the AOA reaches zero degrees it will explode out of the water. Now pitch the wing 10 degrees up. Still draggy, but now it's trying to lift the tail. Get the board up to speed and it will come up easily--and stall.

I say "potato", you say "potatoe", but we're saying the same thing(s) just looking at the problem differently.

Yes, it is the "AOA", but you look at it as the AOA of the fuse (the connects "both wing and stabilizer") to the board on the beach, and I look at it as what the AOA of the fuse to the board is doing to my flight in the water.

Sure, you can theorize on the beach with however many degrees of pitch you have between board and fuse, and what you think it's going to do wrt how the wing will come outta the water, and/or how fast or slow, and whatever other beach talk things we all chatter about there when we're not actually surfing.

I on the other hand simply look it as what the board is doing (what's its attitude or pitch) when the wing is flying level in the water...which it's always seeking to do unless I futz with it screwing that up. Allowing the wing to fly level at speed, is made much easier to feel and control when the deck of the board is level to fuse, and thus the board is flying level with "both wing and stabilizer"...shimming the mast one way or the other accomplishes that.

Always want the AOA to be zero when the deck of level, and change either the mast placement on the board, my foot placement, or both to change how the board comes out of the water at takeoff. But never would I change the AOA of board to fuse just to make the board come out of the water differently, because I'm more concerned with how it's going to fly down the line, and through the turns...not for the couple of the seconds of whether I make the wave or not.

 If I'm not catching waves it's not the AOA that's the problem, but rather my timing, technique, wing choice, or board selection is off. But that's a whole other story once again. 

[PonoBill]

Yes, dontsink, I think you are correct. As I said, I can picture situations in a wave where some downward AOA would be beneficial. The force applied by the wave to the board and foil is not a vector parallel to the water. How that ultimately works would require substantial analysis. The wave energy is roughly a sine curve with energy being transferred through a continuously varying vector. I'm reminded of that every time I try to get some energy from the backside of a wave. The energy is there, it's just harder to get at it.

The force applied by a wing, kite, or sail is a bit less complicated. For a kite or wing, it's mostly a vector applied parallel to the board, through the feet of the rider. It's not simply parallel and in line with the center of the board. With a wing the force is applied relatively high on the rider's body (shoulders, rotated some through the extension of the arms plus whatever deviation of the wind force vector is caused by wing angle) so there are substantial forces pushing the nose down through the lever of the rider's body and pushing the whole assembly downwind. That's one reason we can reach a little higher with a harness--the force is applied lower and with less downwind vector through arm extension, as it is with a kite.

All that aside, it's unquestionable that what works for wing foiling is not necessarily and automatically what will work for surf foiling.

And yes, SanO, technique and ability trumps setup. 70 pound kids with their energy and agility can take something totally unsuited, slam it together with no regard to AOA or any finer point, and pump their way off to the horizon. Geezers who weigh three times what they do with the agility of a hippo need all the help they can get.

[jondrums]

catching small to medium sized waves the wing is not in the same water flow as the board.  The water is flowing more vertical at the board versus at the foil which is deeper down below the wave.  So I wouldn't be surprised if there is a different sweet angle for catching waves depending on the wave too

[PonoBill]

When I explain how the water actually moves in a wave most surfers decide I'm totally nuts, so I don't do that anymore. I just say "google it".

[Califoilia (formerly - SanoSlatchSup)]

catching small to medium sized waves the wing is not in the same water flow as the board.  The water is flowing more vertical at the board versus at the foil which is deeper down below the wave.  So I wouldn't be surprised if there is a different sweet angle for catching waves depending on the wave too

Agreed, and I believe the "theory" that with a longer mast, you're putting the foil even further away from the energy in small(er) waves. But again, I personally, am more concerned with how the board/foil flies and performs once I'm up and riding...and not so much whether I catch every single wave I paddle for.

Heck, I keep going smaller, and smaller with boards, knowing full well that each will reduce my wave count some, but just for how much more fun they are once in the air that they are. But I know that's just personal preference, and not for everyone.