I use the level described here:

The thing to keep in mind about digital levels is, 0.2 degrees or even 0.1 degrees out of level across a 80 cm wide wing is a lot to be out of level. A real bubble level, where the bubble just fits between the lines on the glass sight tube is the most accurate.

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Sandman1221 said..
The thing to keep in mind about digital levels is, 0.2 degrees or even 0.1 degrees out of level across a 80 cm wide wing is a lot to be out of level. A real bubble level, where the bubble just fits between the lines on the glass sight tube is the most accurate.

The general recommendation seems to be that the fuselage should be at an angle of 1.5 to 3 degrees. How do you measure this angle by using a "real bubble level"?

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boardsurfr said..

Sandman1221 said..
The thing to keep in mind about digital levels is, 0.2 degrees or even 0.1 degrees out of level across a 80 cm wide wing is a lot to be out of level. A real bubble level, where the bubble just fits between the lines on the glass sight tube is the most accurate.

The general recommendation seems to be that the fuselage should be at an angle of 1.5 to 3 degrees. How do you measure this angle by using a "real bubble level"?

This link is much better for describing how leveler could be used for adjustment of the rake. You could get leveler app for your smartphone.

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boardsurfr said..

Sandman1221 said..
The thing to keep in mind about digital levels is, 0.2 degrees or even 0.1 degrees out of level across a 80 cm wide wing is a lot to be out of level. A real bubble level, where the bubble just fits between the lines on the glass sight tube is the most accurate.

The general recommendation seems to be that the fuselage should be at an angle of 1.5 to 3 degrees. How do you measure this angle by using a "real bubble level"?

For this application I'd use a digital level, myself (or just measure distance off the board), but there are definitely ways to use a traditional level too. You may own shims of known angles (you do if you do any ski-tuning) so you'd set the level on the appropriate shim and go for dead-nuts flat. However, if, like some of us, you've done a lot of construction or joinery you're accurate to well within a degree or so just by looking at the bubble. I know I'm good to around half a degree but I know guys who just laugh at me because they're so much more accurate.

This is really sort of academic, though, because for our application aren't we really tuning foot-pressure and nose angle and such? The fuse angle may get us close but after that it's going to be subjective tweaking.

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boardsurfr said..

Sandman1221 said..
The thing to keep in mind about digital levels is, 0.2 degrees or even 0.1 degrees out of level across a 80 cm wide wing is a lot to be out of level. A real bubble level, where the bubble just fits between the lines on the glass sight tube is the most accurate.

The general recommendation seems to be that the fuselage should be at an angle of 1.5 to 3 degrees. How do you measure this angle by using a "real bubble level"?

That was not my point boardsurfr, my point as stated was 0.2 or 0.1 degrees on a bubble level app is a lot to be off if you are going for 0.0 degrees level or any other value of degrees, that is all. So if you want 1.5 degrees and get 1.7 and think that is close enough, well maybe but it is a lot to be off. Now if you are going for 0.0 degrees level a real cheap level works fine, and then there are real high accuracy levels that have additional markings for when you want a few degrees out of level.

I was trying to get shims for my SB IQfoil and ended ordering Phantom shims in North America. I recently noted F4 is now providing mast shims significantly better priced. In addition, Jordy Vonk provides very good guide for setting up mast shims and angle that is applicable to all race shims.

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SA_AL said..

Sandman1221 said..

For my AFS W95 foil I used silicone grease to help get it in (was really tight), after a while it no longer needed the grease, and now slides in smoothly. And the top of the mast head has an angle/slope to it like any fin does, so there was space between the mast head and top of the DT box, and the screws were always loose after a session. When I made a shim for the mast head to set the angle to 0.0 degrees the shim also filled in the gap between the top of the mast head and DT box, then the screws stopped coming loose.

Great I may try the grease. How did you make the shim for the mast head? Those are not commercially available. Could you provide description of making the shim and a picture? Thanks

I have a detailed write up on the shim, just search for "1st session on home made shim for foil rake angle, works good!"

As for how I made it, got a scrap piece of starboard from a marine salvage store and used a miter saw to trim width to be just narrower than box, then measured depth of box and height of foil mast head and subtracted the two for the height of shim in back, then used miter saw to cut wedge out of trimmed starboard, drilled hole for rear screw, and then used a sanding block with 200 grit paper to fine tune shim until fuselage was at 0 degrees.

I won't even get started on this. (Wrong, yes I will.) We are talking about DT fittings without flanges.

For a DT box if you do anything that compromises a tight and intimate fit of the front and back rounded tapers between foil top and box, you are asking for trouble.

Shimming usually means getting the top or bottom of the tapers to touch, but not entire length. Top front with bottom back. Or bottom front with top back. This adds point loads and can lead to box failure.

If the foil top fitting can move--at any amount--back and forth because you are shimming the inside top surface, it will also lead to box failure.

The tuttle design was never meant to include a touch of the top of the fitting to the inside top of the box. Instead it was meant to include ONLY a tight and intimate fit of the front and back rounded tapers. Period. Google the tuttle drawing and study it.

People that sell DT shims are foisting bad engineering on us. Don't fall for it. If there are shims that touch the ENTIRE length of both rounded tapers as a matched kit, with no shimming of the top surface, then fine. I have not seen nor heard of such.

So, what to do if you absolutely MUST change the ride angle of the board wrt to the water surface?

1. Get away form DT and use only the dual-track so that you can fit a big tapered shim under the entire contact surface. This is safe and effective. Such big shims are available. For freeride foiling, the industry is migrating away from DT and toward dual-track anyway, so this solution is becoming more doable.

2. Depending on the design of the mast to fuse connection, shim that to change the angle of fuse wrt to mast. This is easy for something like the Slingshot that uses two bolts to mate flat surfaces. Can't do this for any connection that includes a sideways bolt.

3. Depending on the design, shim the front wing to change its angle wrt to the fuse. You will have to shim the stab to match so that you don't change the relative angle of the stab to wing. Shimming the front wing is a new idea and only works for those designs that have the wing bolted to the bottom of the fuse. Don't worry about increasing fuse drag. It's already a drop in the bucket compared to induced drag of the wings and parasitic drag of the mast.

By the way, if your DT foil fitting includes a flange, it's the flange that controls the mast angle. You have only #2 and #3 available.

OK, I got started on this. Sorry. I prefer to see DT boxes used correctly.

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segler said..
I won't even get started on this. (Wrong, yes I will.) We are talking about DT fittings without flanges.

For a DT box if you do anything that compromises a tight and intimate fit of the front and back rounded tapers between foil top and box, you are asking for trouble.

Shimming usually means getting the top or bottom of the tapers to touch, but not entire length. Top front with bottom back. Or bottom front with top back. This adds point loads and can lead to box failure.

If the foil top fitting can move--at any amount--back and forth because you are shimming the inside top surface, it will also lead to box failure.

The tuttle design was never meant to include a touch of the top of the fitting to the inside top of the box. Instead it was meant to include ONLY a tight and intimate fit of the front and back rounded tapers. Period. Google the tuttle drawing and study it.

People that sell DT shims are foisting bad engineering on us. Don't fall for it. If there are shims that touch the ENTIRE length of both rounded tapers as a matched kit, with no shimming of the top surface, then fine. I have not seen nor heard of such.

So, what to do if you absolutely MUST change the ride angle of the board wrt to the water surface?

1. Get away form DT and use only the dual-track so that you can fit a big tapered shim under the entire contact surface. This is safe and effective. Such big shims are available. For freeride foiling, the industry is migrating away from DT and toward dual-track anyway, so this solution is becoming more doable.

2. Depending on the design of the mast to fuse connection, shim that to change the angle of fuse wrt to mast. This is easy for something like the Slingshot that uses two bolts to mate flat surfaces. Can't do this for any connection that includes a sideways bolt.

3. Depending on the design, shim the front wing to change its angle wrt to the fuse. You will have to shim the stab to match so that you don't change the relative angle of the stab to wing. Shimming the front wing is a new idea and only works for those designs that have the wing bolted to the bottom of the fuse. Don't worry about increasing fuse drag. It's already a drop in the bucket compared to induced drag of the wings and parasitic drag of the mast.

By the way, if your DT foil fitting includes a flange, it's the flange that controls the mast angle. You have only #2 and #3 available.

OK, I got started on this. Sorry. I prefer to see DT boxes used correctly.

With all due respect (and I've mentioned this ad nauseum), the current boxes being used, while they adhere to the DT dimensions are no longer the DT boxes you knew from way back when. They are beefed up to handle the additional stresses of both the foil and foils inserted at an angle. Some companies simply call the new standard "Foil Box" while the measurements adhere to the DT standard except for the flat internal top to facilitate wedging. There are literally fleets of windfoil boards out there with foils being wedged in and I've seen no mentions of issues from the practice. Starboard and Phantom explicitly tell you how and why to wedge foils in their boards.

I get it that it doesn't appeal to your aesthetic but it doesn't fit with current industry practice from either foil or board builders. If the builders were having an issue with it, we'd have heard about it by now. The average IQFoil campaigner is putting more wear and stress on their gear in a season than most of us in five years or more. They are the people that are literally putting so much wear on their foil masts that they are going "soft" (for them, not us mortals).

Well I have been using the foil mast head shim for 2 years now every time I go out in my 2016 Goya Bolt 135 board, hit plenty of sea life, crab trap lines, dragged an anchor line with anchor attached to shore, and bay bottom and my DT Foil box is good, no cracks, AFS foil which has a flange is tight in the box and screws do not come loose like they used to without the shim. Those are the facts and you can not change them!

In a foil box you want at least one part of the foil head to make contact with the roof of the box, more is better.

Like was mentioned these aren't really "tuttle" anymore and thats a good thing. Being able to install the mast right to the roof is both stronger and more consistent.

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segler said..
I won't even get started on this. (Wrong, yes I will.) We are talking about DT fittings without flanges.

For a DT box if you do anything that compromises a tight and intimate fit of the front and back rounded tapers between foil top and box, you are asking for trouble.

Shimming usually means getting the top or bottom of the tapers to touch, but not entire length. Top front with bottom back. Or bottom front with top back. This adds point loads and can lead to box failure.

If the foil top fitting can move--at any amount--back and forth because you are shimming the inside top surface, it will also lead to box failure.

The tuttle design was never meant to include a touch of the top of the fitting to the inside top of the box. Instead it was meant to include ONLY a tight and intimate fit of the front and back rounded tapers. Period. Google the tuttle drawing and study it.

People that sell DT shims are foisting bad engineering on us. Don't fall for it. If there are shims that touch the ENTIRE length of both rounded tapers as a matched kit, with no shimming of the top surface, then fine. I have not seen nor heard of such.

So, what to do if you absolutely MUST change the ride angle of the board wrt to the water surface?

1. Get away form DT and use only the dual-track so that you can fit a big tapered shim under the entire contact surface. This is safe and effective. Such big shims are available. For freeride foiling, the industry is migrating away from DT and toward dual-track anyway, so this solution is becoming more doable.

2. Depending on the design of the mast to fuse connection, shim that to change the angle of fuse wrt to mast. This is easy for something like the Slingshot that uses two bolts to mate flat surfaces. Can't do this for any connection that includes a sideways bolt.

3. Depending on the design, shim the front wing to change its angle wrt to the fuse. You will have to shim the stab to match so that you don't change the relative angle of the stab to wing. Shimming the front wing is a new idea and only works for those designs that have the wing bolted to the bottom of the fuse. Don't worry about increasing fuse drag. It's already a drop in the bucket compared to induced drag of the wings and parasitic drag of the mast.

By the way, if your DT foil fitting includes a flange, it's the flange that controls the mast angle. You have only #2 and #3 available.

OK, I got started on this. Sorry. I prefer to see DT boxes used correctly.

I agree with Grant that foil ready or foilbox have the same dimensions than a deep Tuttle but they are reinforced so the tapers don't necessarily need to work. I talked last year (or the year before?) with Mr Tuttle over the phone and he confirmed that the design was not meant to carry the loads on the top of the box. To repurpose the box, builders are putting a crazy amount of carbon on the top. There is a video of Seatex showing how it makes boxes and I counted something like 14 layers of carbon.


The top of my Roberts foilboard box is roughly 1/4 inch thick. Although the foil mast does not touch the top of the box, Rob Mulder told me I can shim the foil mast if I want to.

yes, I know some foilboxes are failing but that is because manufacturers are trying to balance weight and strength (same with masts, foil masts, booms, bicycles, you name it). But I guess most of us weekend warriors won't encounter many problems with foilboxes.

The problems I've heard with some foil boxes of the new kind were Lateral looseness. May be due to grit wearing them down or something else? Also, some of the aluminum iq mast tops of the old design were getting crushed but they have since reinforced them.

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aeroegnr said..
The problems I've heard with some foil boxes of the new kind were Lateral looseness. May be due to grit wearing them down or something else? Also, some of the aluminum iq mast tops of the old design were getting crushed but they have since reinforced them.

The Goya Bolt foil box was super tight for quite a while, but is now just snug, I do make sure mast head and box are free of sand every time I insert it. But with the shim it is really locked in, no more loose screws at the end of a session. Without shim rear screw would be loose every time after a session, that could lead to wear for sure. Then the AFS mast head is solid carbon too, that helps.

As for the foil box design, I think they made the top of the box super strong not for shims per say, but to make sure the screws did not get pulled through the box when hitting something with the foil at high speed. Know someone who had a foil on an old slalom board and hit a manatee, almost pulled screws completely through the DT box.

Today's current "foil boxes" all conform to the tuttle design. They all have the front and back rounded tapers at the angles and radii on the drawing, and they all have the inside width from the drawing. What varies is the depth and shape and angle of the inside top roof. Since tuttle does not specify a height inside the box, they still meet the design standard. They call them "foil boxes," but they are all tuttle. Fortunately, they also are beefed up with extra wall thickness and reinforcement to carry the fore and aft loads from foil wings that lift as much as 12" forward of the mast. That is a very strong forward angular force on the box and also explains why you have to really watch the forward fin screw to make sure it remains tight.

If you match brands for "foil box" and "foil top fitting" you will be fine even if they touch inside the box at the roof.

However, all over the place you see people mounting brand-x DT foils into brand-y DT boards. The only thing in common is the standard design of the DT box. (Unless, of course, you have gone to dual-track, which solves a lot of problems.) The main issue with mismatching brands is making sure the foil fitting is not too tall for the box it's going into. If it is, it will move. That's trouble.

I mount no-flange Moses and AFS DT into Fanatic, Exocet, Starboard, and Mike's Lab. As long as the fitting is not too tall, it fits perfectly and tightly without any movement. If it is too tall, shave it. I had to shave the AFS to fit into Exocet. Movement means failure (we have seen a couple examples on these fora).

Always and forever, you want a tight and intimate fit of the fore and aft rounded tapers regardless of height or inside roof contact.

I foiled for over 50 hours with a setup that had exactly ZERO taper contact, using only the top of a standard Cobra shallow tuttle box with a deep tuttle foil and had zero problems.
I've seen people not get 2 hours foiling out of a box using just the tapers and no top contact. That was a quality glass box from the peak of the formula era tied to the deck (no bolt tunnels).

All the designers, manufacturers and apparently Tuttle himself say that box top contact is fine compared to literally one guy on the internet saying it isn't.

Foils aren't formula fins. The loads are completely different.

So shim those masts, just make sure you have some box contact preferably at the front.

Partially correct. Formula fins exerted massive side forces, so FW board makers used DT finboxes designed (over many years) for these side forces. It was a well matured technology. In the end, FW racers went to very soft fins that bent to windward under the racer's butt to act as a kind of foil to help lift the board off the water. This greatly increased speed upwind. This was why you saw the best racers railing their boards to leeward by pointing their toes. Get that soft fin working as a foil.

When people started using the same DT boxes for foils, the boxes now had to carry massive fore and aft rocking forces, which the boxes were not designed for. In many cases (a certain SB model comes to mind), the boxes failed. There are examples with pictures of split boxes out there.

Fortunately for me (and for the SF racers who went to foils), Mike's Lab formula boards fortuitously already had strong enough DT boxes to carry the foiling forces. My L6 is still working just fine. Many other brands and types as well. Yes, there have been some failures, but it's not like there has been a huge rash of these causing panic across the sport.

So now, when the industry started coming out with "foil ready" boards they used beefed up DT boxes that had thicker structure and sometimes extra stringers to carry the fore and aft rocking forces. In true marketing fashion, they call them "foil boxes" but they are still DT boxes per the tuttle drawing, albeit with all kinds of variable heights and inside roof shapes and slopes.

No, Tuttle himself did not say that. Just look at his design drawing. The engineering intent is clear. Stick that puppy in there and immobilize it completely with tight and intimate contact of the front and back rounded tapers. Do that and your system will last forever.

All I'm trying to do is help people prevent failures. Point loads (shimming inside the box) and movement result in failures.

If you don't like this whole DT discussion, switch to dual track and solve the problem completely. The industry is migrating this way anyway for everything except for windfoil racing.

Foil boxes are parallel not DT. The intent is to have the mast touch the roof of the box. My Seatex foil box is on a different level from a normal DT. I have a Starboard foil box on order and might be able to show pictures between the Seatex and Starboard foil box. SB instructions for the IQ foil wants you to make full contact on the box.

The DT sides are always parallel. Are you saying that the front and back rounded tapers are also parallel?

On the "foil boxes" I have (Fanatic, Exocet, Starboard), the front and back rounded tapers each lean in by 10 degrees, as per the tuttle design.

If you measure your StingRay you will see the difference between a foil box and DT. The depth is 67mm on each side (parallel=both depth the same measurement).

Here is the IQ foil setup guide. "Make sure that the top of the foil's mast makes full contact with the bottom of the board's foil box. This full contact gives maximum support to the foil and sets the mast firmly at the recommended angle."

My point is that foil boxes are no longer the traditional DT.

iqfoil.star-board.com/wp-content/uploads/2020/09/iQFoil95-Board-Trimming-Guide.pdf

This is true. However, the depth is not what matters. On the original tuttle drawing, there is no specification of depth. It shows a height of 5 inches, which no box or foil or fin features.

What matters is the 80 deg angle and radius profile of the front and back rounded tapers. Also, the thickness and parallel walls.

You can fit any DT foil or fin into any "foil box" as long as it is not too tall, and it will fit tight and intimate to the tapers. My Stingray 140 and Exocet FF132, both have the exact same tapers (80 deg angles and radius profiles) as on the tuttle design. Where they vary is the inside taper length and roof height and angle.

The IQfoil setup guide is a good example of matching the brand of foil to brand of board. They design them to match everything inside the box, tapers and roof and everything. That's fine when you match brands. If I mount a Fanatic foil into the Stingray or a Exocet foil into the FF132, they will go all the way in to the roof. Brand matching.

But if you are matching non-flanged brand-x foil and brand-y DT box (this was all we had until a couple years ago), all you can rely on are the standard design tapers. If you ensure the tight fit, you will be fine. The only way to ensure a tight fit is to leave room inside between top and roof. Point loading those tapers with roof contact or shims is a path to failure. Unless you match brands.

Since day one (2016) with AFS no-flange foils and all the various DT boxes out there (formula and big slalom boards), Sailworks has coached "insert, wrench forward, tighten screws, wrench back, tighten screws, wrench forward, tighten..." for 3 or 4 cycles until the screws do not tighten anymore. Once you have done this, the tapers are tightly fit, and the foil will not move. The tapers will carry the fore and aft loads, and things will be fine. Watch the Sailworks team mounting non-flanged SAB foils into Roberts or Pacific foil boards. This wrenching-tightening cycle is exactly what they do.

A simple shim removes all that pushing and pulling while also adding much more consistency and a stronger connection to the box. Which is exactly why every race foil manufacturer recommends it.

Please post a photo, with measurements, of these shims.

The only shims that will not point load the box are full-length shims. That is, they run the entire length of both the front and back rounded tapers.

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segler said..
Please post a photo, with measurements, of these shims.

The only shims that will not point load the box are full-length shims. That is, they run the entire length of both the front and back rounded tapers.

www.phantom-windsurfing.com/spare-parts/p/goybox

Those in the photo are top shims since they show holes for the bolt. Every single one of them will point load the front and back rounded tapers. Unless...

...if they result in a really tight connection to the inside top of the box (matched brands again), that is where all the load is being carried. In such a case there might not even be any tight contact of the front and back rounded tapers at all. So, if the inside roof of the box is stiff enough to carry those loads, it might not matter, and the tapers are just along for the ride.

IMHO this is questionable engineering.

So, regardless of whether you rely on top shims for inside roof contact, or no shims for front and back rounded taper contact, make sure that nothing moves after you have mounted and tightenend the bolts. If there is any movement, the box will eventually fail.

Roberts, North Pacific, Mike's Lab, and many others do not depend on roof stiffness. They run reinforced DT boxes from bottom deck to top deck, all the way through (no bolt chimneys) with inside heights varying from 2.0" to 3.5". They depend only on the front and back rounded tapers to carry foiling loads. (Some even have longitudinal stringers bonded to the sides of the box to spread the fore and aft loads into the board even more.) As a result you can mount any DT foil (even flanged DT) into them and have it work well.

So, recommendation. If your board has bolt chimneys, or you want to shim the foil to vary the rake angle, be sure to match the brand of board and foil. If you mismatch brands (80% of what I see in the gorge), don't shim. Mount any DT foil that is not too tall inside and make sure it is tight to the tapers, or mount a flanged foil.

I have had good luck fitting non-flange SAB and AFS foils into Roberts, North Pacific, Mike's Lab, Fanatic, and Exocet (with chimneys) boards. Flanged DT foils (such as LP and Slingshot and some SAB) with fairly short tops fit everything.

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segler said..
If your board has bolt chimneys, or you want to shim the foil to vary the rake angle, be sure to match the brand of board and foil. If you mismatch brands (80% of what I see in the gorge), don't shim.

What do you recommend in this case, when there's a brand mismatch and one would like to set the correct rake angle?

Would it be okay in your opinion to create a custom shim to ensure full contact between the mast and the box? For reference, it's a "bolt chimney" DT foil box and a flat (not angled) top of the mast, so it would be relatively straight forward to get the shim thickness right.

Sure, you could try that. People have done this. In order to ensure roof contact, I think you want to start too thick, then keep shaving down until the fit is correct.

I think the main challenge is make sure you get contact all along the roof rather than just at one end or other.

Even then my main concern is point loading the front and back rounded tapers. If you shim enough so that there is no contact on the rounded tapers AND there is zero movement, I suppose it would be ok.

A similar example in my experience. My Exocet FF 132 has the bolt chimneys, and so it supposedly has a DT box with a strong enough inside roof to carry loads. A Exocet foil designed for it will fit to the roof and be fine.

However, I am using a Slingshot i76 with a flange. A flange solves lots of problems with fit this way.

I also mount a AFS-2 no-flange foil, but ensure it is tight to the front and back rounded tapers, as I always preach. No inside roof contact. Don't want any.

With both mountings I accept the mast rake angle as is. I don't try to change it. Board angle in flight is just fine.

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FormuIa said..
What do you recommend in this case, when there's a brand mismatch and one would like to set the correct rake angle?

What brands and gear are we talking about and what is your current angle?

If you have a foil box you don't need any of that, just shim the end of the foil head that needs it and carry on. This is how literally every race foil manufacturer does it.