utcminusfour forum posts in last 60 days

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YellowHelmet said..

utcminusfour said..

YellowHelmet said..

utcminusfour said..
I imagine the leviathans would fit on your fuse.
M8 is required.
At my size I know from firsthand experience that would it not be stiff or stout enough front wing connection. You may be fine at 75kg.
If you can uphaul and slog around on the Wizard 114 I reckon it would work fine. The foils are easy to turn and handle but you need enough float and stability to handle really light lulls with chop.
You may not need as much foil as I am using.
Your right it would be good to have an app that could help wade through all the options.
At the moment I am enjoying the challenge of exploring a design space that doesn't come with instructions.

I was thinking about Leviathan 1150 or Leviathan Pro 1260 + M6/M8 washers.

Also saw PTM999 and PTM1001 (are there even bigger HA Slingshot foils ?). Anyone experience with these foils for low wind in addition to PTM926.

I heard some brands (like Duotone) stop warranty with spans bigger than 100 cm.

So better not go to wide as well for turning.

Would the stress on the long carbon mast W103 be to stong ? I could use my old Hover Glide 90 cm with connector piece.

Slogging and uphailing sail on Wizard 114 liter is no problem for me at 75 kg, but I notice and friends say the rear of my board is low in the water creating drag.

It is the connection at the front wing that is weakest link with the compatible Sab and Slingshot options. Your mast will be fine.
I would strongly advise against using M6 bolts, you want to drill and tap or drill and add inserts to your fuse so you can use M8 screws.
I would recommend that upgrade even if you don't go for a bigger wing. Take it into a metal shop and have them do it if you not interested in DYI. The bigger screws are more forgiving and tolerant of sand and cross threading not to mention a lot stronger.
I have no experience with the Leviathan or PTM but the Leviathan are higher aspect.

Does this mean drilling through the fuselage and then treading, or can it be treaded without drilling through the fuselage. I have a threading set but this gear is for threading an open hole.

Once upgraded to M8 how do you fix the old PTM or PFI foils of Slingshot. Is it needed to make a tapered wider hole in the Slingshot frontfoils ?

The fact that you have taps and understand they are for open holes means you absolutely can do this.
The time for a machinist to do it is less than an hour so less than a new fuse. Either way it is a good thing to do and many of us on this forum have made this mod.

These are commonly available tools, but they are specific types of taps. Drill with the supplied bit, or be very certain you have the exact diameter bit required. Measure the depth of the hole and mark that depth on the bit with tape as a guide. Start threading with a "starting" tap. It has a taper on the tip with several lead-in threads. Like the name implies, it's designed to make starting easy and straight. It is likely that a starting tap is what you already own. Then use a "bottoming" tap. Its tip is much less tapered, and the threads go almost all the way to the end. This tap will cut threads nearly to the bottom of the hole.

Helicoil inserts are another route you can look into. They come with good instructions and often installation videos. Same steps really. I have struggled with the inserts. There is a length of the wire that is used to hold and install the insert that is designed to be hammered out and I sometimes can't get that out. Usually, I can get full thread engagement and just leave it.

The wings are easy. Drill with a normal M8 clearance bit. Then enlarge the tapered hole with a 90-degree countersink. Go slow and keep testing with the fastener until it sits flush with the wing.

If you botch tapping, you can still use inserts because there o.d. is bigger, the inserts can be replaced. If you botch the inserts a machine shop can still bail you out.

I know this stuff from experience; I broke, bent, cross threaded and stripped a bunch of M6 wing bolts before the industry acknowledged that M6 is too small.


Amazon.com: Aceteel M8 X 1.25 Metric Hand Tap, Right Hand M8 X 1.25mm Threading Hand Tap 1Pair : Industrial & Scientific

Vouyar Cobalt Steel Single End Countersink Drill Bit with Cobalt Coating Finish for Hard Metal Wood, 90 Degree M35 HSS, 8MM Round Shank, 14MM Body Diameter - Amazon.com

Amazon.com: fixinus 30 Piece M8 x 1.25mm Thread Repair Insert Kit, Stainless Steel Thread Repair Kit Helicoil Coil Compatible Hand Tool Set for Auto Repair : Automotive

I have a waterproof phone pouch and an iPhone, and I want to get started tracking my sessions. What are the good app options? I want speed, VMG, and a track. How is VMG calculated without an anemometer? I can see placing a "waypoint" well upwind of where I would be riding. It would be sick if it could call out the data audibly. Which ones are easy to use? Which ones can add the data to a video?
Thank You!!!

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YellowHelmet said..

utcminusfour said..
I imagine the leviathans would fit on your fuse.
M8 is required.
At my size I know from firsthand experience that would it not be stiff or stout enough front wing connection. You may be fine at 75kg.
If you can uphaul and slog around on the Wizard 114 I reckon it would work fine. The foils are easy to turn and handle but you need enough float and stability to handle really light lulls with chop.
You may not need as much foil as I am using.
Your right it would be good to have an app that could help wade through all the options.
At the moment I am enjoying the challenge of exploring a design space that doesn't come with instructions.

I was thinking about Leviathan 1150 or Leviathan Pro 1260 + M6/M8 washers.

Also saw PTM999 and PTM1001 (are there even bigger HA Slingshot foils ?). Anyone experience with these foils for low wind in addition to PTM926.

I heard some brands (like Duotone) stop warranty with spans bigger than 100 cm.

So better not go to wide as well for turning.

Would the stress on the long carbon mast W103 be to stong ? I could use my old Hover Glide 90 cm with connector piece.

Slogging and uphailing sail on Wizard 114 liter is no problem for me at 75 kg, but I notice and friends say the rear of my board is low in the water creating drag.

It is the connection at the front wing that is weakest link with the compatible Sab and Slingshot options. Your mast will be fine.
I would strongly advise against using M6 bolts, you want to drill and tap or drill and add inserts to your fuse so you can use M8 screws.
I would recommend that upgrade even if you don't go for a bigger wing. Take it into a metal shop and have them do it if you not interested in DYI. The bigger screws are more forgiving and tolerant of sand and cross threading not to mention a lot stronger.
I have no experience with the Leviathan or PTM but the Leviathan are higher aspect.

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YellowHelmet said..
Maybe it would be an idea to find out a formula, algorithm with all the necessary input and output data.

If not possible by formula, then by neural network, some AI.

Maybe some savant mathematical member can do this.

Input :

- Weight.

- Volume of the board, maybe also width.

- Size of the sail (camber or not).

- Span and surface of the front foil = aspect ratio (maybe thickness and volume).

- Maybe size of the stabilizer.

- Take off wind speed.

- Pumping : no - lazy - active

- Resulting cruising speed.

- Salt / fresh water (salinity)

- Other ?

All with sliders, all dynamically interacting, selecting what input(s) are to be changed for what output(s), for example asking for a take off wind speed of 10 knots by changing span / surface of the front foil for a given board size and fixed sail, or asking for the sail size for a fixed board and foil.

An app would be nice.

I think in commercial airliners there is a stall alarm when the steering wheel starts to shake. If this can be calculated for air foils, such should be possible for water foils.

This should also be possible for wingfoil and even windsurfing, but for windsurfing the window of possible changes by sail and board size to start planing is much more narrow than for foiling.

Dreaming about a wishbone with stall alarm that wakes me up when it's time to start pumping.

I think he's got a good point here. Why shouldn't we have a velocity prediction program for the entire package right? I mean there weren't even barely computers around and sailboat racing had every variable calculated in one place. Or even better how about a simulator! I've got some energy for that for sure. I don't have all the knowledge or data required, it's gotta be a community grassroots open source approach. Just planting that seed.

I thought I remembered you had tracks. When it warms up try it with the foil all the way back and sail full forward. Mackite will let you demo wings right? Maybe try spitfire wings, I have been really impressed with them once I realized that I needed to move the foil full aft.

I thought I remembered you had tracks. When it warms up try it with the foil all the way back and sail full forward. Mackite will let you demo wings right? Maybe try spitfire wings, I have been really impressed with them once I realized that I needed to move the foil full aft.

I thought I remembered you had tracks. When it warms up try it with the foil all the way back and sail full forward. Mackite will let you demo wings right? Maybe try spitfire wings, I have been really impressed with them once I realized that I needed to move the foil full aft.

I imagine the leviathans would fit on your fuse.
M8 is required.
At my size I know from firsthand experience that would it not be stiff or stout enough front wing connection. You may be fine at 75kg.
If you can uphaul and slog around on the Wizard 114 I reckon it would work fine. The foils are easy to turn and handle but you need enough float and stability to handle really light lulls with chop.
You may not need as much foil as I am using.
Your right it would be good to have an app that could help wade through all the options.
At the moment I am enjoying the challenge of exploring a design space that doesn't come with instructions.

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excav8ter said..

Grantmac said..

excav8ter said..

Grantmac said..
The 909 is a VERY good foil. I'm winging it and am extremely tempted to get the WS fuselage for light wind days. You may wish to go up on the stab size, the 370 is very loose.

Thanks for the tip. I'm guessing I'd have to order a larger stab separately? What size would you recommend? I stepped back from wind foiling last spring to try wing foiling again, and hopefully get my jibes down. But I really miss wind foiling. Hoping I can find a balance and do both

I'd go to one of the curved stabs with a bit more area.
Gullwing 430 if you want easy.
Reverse 395 if you want more sporty.

The 370 is what I have and I think it would be a handful windfoiling.

Thank you! I'm cautiously optimistic that the SAB foil set up will be better than the Axis HPS1050 and BSC1060 that I was riding. On those foils I constantly fought over foiling in windy conditions. Especially when I'd try to cruise on a wave. Our waves on Lake Michigan are very short period and very steep.

With those Axis foils I mentioned, my smallest sail was a 3.8 Sailworks Revolution. I'd be basically at my limit by the time the wind hit 22-25mph. The 3.8 would feel too big. Maybe it was just the foil?

Hey Mate,
What fuse are you using with your Axis foils? Do you have one the few boards Casey built with tracks? The wind speeds and sail sizes you are talking about are reasonable, 25 is a lot of wind and those are powerful wings. The axis 899 windsurf fuse options all place the front wing really far forward and that might be your challenge especially if you are light. I am exploring Axis atm and with the black 899 v1 windsurf fuse I have my foil at the back of the tracks and the sail at the front to get the balance right.

Thank you, JJ!
Simon, I feel like you have been camera shy lately!
Okay that make me wanna put more effort into my duck gybes!

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YellowHelmet said..

utcminusfour said..
Or another option is to add a pump foil and skip the large board and sails.
I am at 196 kg and can takeoff in 10 knots and fly through less using a 5.1 meter freestyle sail.
For me I am finding it not just for the very lightest days.
It makes marginal days magic days! If there any waves or wakes you can ride them endlessly without sail power or use them to get flying in a lull.
It is the only foil set up I have tried that I can actually get to go upwind in winds less than 15 knots.
The low stall speed is a great tool for learning new maneuvers, it gives you more time an opportunity to finish the move.

Nice, very nice.

So in the video you use a big board IQ, big sail 7 m and big foil with very high AR ?

How much wind ?

Severne Hydro better than SB IQ ?

That is not me in the insta vid. I am one_slice_short on insta, I did make a couple of comments on that post that are relevant to this convo.
The gent who posted said it was 5-7 knots. He is using an aluminum mast, a first gen red 899 windsurf fuse and PNG 1300 from Axis, this is all gear that can be found used at reasonable prices. Looks like an IQ board and Severn sail, he is friendly and I am sure he would answer any questions you may have.
The main point I am trying to convey is High AR is only part of what is needed for early flight, you need big span > 1100 and foil cross sections designed to be efficient for low-speed flight. Put your money into your foils first to reach your goal. A wide board is only needed to lever an 8+ meter sail, all that extra flat bottom actually makes it harder to get free. You may not need all that sail to reach your goals and if you don't then you do not need a separate big, dedicated board
Grantmac makes a good point about most of the large wings have fuselages that place the front wing too close to the mast for windsurfing.
I am not here to promote any one brand, but that detail is one of the main reasons I am riding Axis atm, they have a windsurfing fuse that accepts their large span wings, and the connections are up to the job. I am experimenting with the other sizes of off the shelf axis fuses as well as the Spitfire wings 900-1180, stand by for that post when I have more time with em, but so far I am thrilled.
Here is a pic of my current configuration for light air, I am 106 kg I can honestly say I can takeoff in 10 knots and that it is really fun especial in small swell. It goes upwind amazing! The day this pic was taken was magic, it had been blowing hard for days so there was nice left over wind waves, but the wind dropped to 8-12 and I surfed for hours. Board is a custom 2m x .71m x 150L. Sail 5.1 Severn R4D. Cedrus wind ~85cm foil mast, axis black 899 windsurf fuse, PNG v2 1200, progressive 450 stab.

Or keep the big gear and add a pump foil.
www.instagram.com/reel/DTHlxYBE1Fo/?utm_source=ig_web_copy_link&igsh=NTc4MTIwNjQ2YQ==

Or another option is to add a pump foil and skip the large board and sails.
I am at 196 kg and can takeoff in 10 knots and fly through less using a 5.1 meter freestyle sail.
For me I am finding it not just for the very lightest days.
It makes marginal days magic days! If there any waves or wakes you can ride them endlessly without sail power or use them to get flying in a lull.
It is the only foil set up I have tried that I can actually get to go upwind in winds less than 15 knots.
The low stall speed is a great tool for learning new maneuvers, it gives you more time an opportunity to finish the move.

Yeeew! Getting things done!

Use that fuse in the position that puts the front wing furthest forward.
Put your sail all the way back in the track.

Remove the back straps. Until you are jumping, they are not needed.
The front straps are not necessary either. They are handy for carrying the gear, but they are a risk to your ankles until you learn to balance in roll. Half straps or a Bartlett release straps are a good call.

Bum a small scrap of deck pad about 6" by 6" from Mark and use it as a back foot locator. Cut holes for the bolts and put it over the Tuttle with the front edge about 3-4 inches forward of the front bolt. You want to feel that under your foot right when you are ready to take off.

Hang on to the boom when you crash. It keeps you away from the foil.

Your body goes where you look. Do not look down. Stare at the horizon.

Take that 5.7 out in a steady 15 knots. The two meter less sail thing comes later with skills and with a more efficient setup.

The biggest risks are at the edge of the water getting worked in waves, so start in flat water. Wear booties. A wetsuit with legs if you can. Helmet and impact vest make sense too.

Avoid water starting at first or at least don't kick.
I used a marker (wipes off with alcohol) to mark the rail of the board where the front wing sits so I could see where it was when water starting.
When you get more comfortable with where the wings are you can ease into water starting.
Once I clear the sail from the water, I slowly reach my back foot for the fuse near the back stab. That is my prep to water start mode. It locates the foil and works great for body dragging the last bit into the beach instead of running aground standing up.

The biggest challenge for most people is taming pitch. If you can windsurf you already have pitch control skills, they just are not sensitive enough yet. Time on the water is the only way.

The time on the water does not all have to be under sail. If you have access to a modest power boat or jet ski, spend time tow foiling. It isolates the foil riding skills. Wake parks and cable parks are useful and fun. Yes, with your formula board, don't worry how it looks because you are doing something cool that most people won't try so that is cool! Start on your belly going slow, work your way to your feet, then have the driver go. I still remember when pitch control finally clicked for me, it was behind the boat and suddenly I could start looking around and still fly level, my next session sailing after that was in control and playful!

Have fun! Stay safe! Keep us in the loop!

Congrats Mate!
Tell us about the board, what is the length, width and volume. How far from the front tuttle bolt to the sail track, often that dimension is too large (north of 41") when converting older fin boards? That is not a deal breaker, fuse details can sort that, or you can add a sail track behind the original. What size and type of sails are you using? 6 meter or less wave sails will pair better with free ride foils like the Infinity, if you are 8 meter + with cambers you may do better with a used IQ or race foil.
A lot of us here used the SS infinity to get started successfully. I had the Infinity 76 at a similar weight, and it needed 15+ knots of wind to launch me, the 84 may be a better fit.
One more comment on the fuse, that is the main difference between windsurf and the other foil sports. Our fuses are longer with the front wing further in front of the foil mast. If you see a used big guy wing set up at a great price see if you can find a windsurf fuse separately.

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DarrylG said..

utcminusfour said..
Love It!
I like how your bevels run parallel to centerline and the die out before the tail. I have tried a couple boards with bevels that wraps around to the tail, it is essentially massive tail rocker and that pork's planning. I still feel like bevels or similar arced cross sections can help release the flat bottom surface tension and therefore launch earlier, but they have to be detailed properly so they don't cause drag at planning speeds. Your design looks like a nice balanced design in this aspect. Love the thickness with the full outline, short but stable! Perfect finish details! Tuttle and tracks! The Tuttle is a light, strong off the shelf way to connect the tracks to the deck, I built my board that way and I am glad to have the option to run both! My best mast these days is track but I use the Tuttle to gauge foil location. I make sure the Tuttle is never completely covered with the mast plate so any water can drain in flight. Keep us in the loop as you put more hours on it and really learn how she goes.
Any core or is it single skin? What the laminate schedule, EPS density and board weight?

Standard 13kg/m3 eps, 3mm core cell btm and deck, ( 6mm around foil tracks). 200 g T700 biax carbon, plus innegra rail band. It was under 9kg before pads and straps. Design borrows heavily from the original Severne predator proto.

Thank You Darryl!
Our little niche sport is so lucky to have pros like you and Mark sharing your knowledge for the good of the community!
I have a love/hate with Innegra! I love it when I am done, the boards never need repairs. I hate it when I am so close to being done with the build, but I am covering up all the bare Innegra spots where I sanded through the carbon I know if I tried an Innegra rail wrap like that I would have a burn through top and bottom at the seam edge. It is really amazing how tidy and precise your laminating and fairing skills are!

Love It!
I like how your bevels run parallel to centerline and the die out before the tail. I have tried a couple boards with bevels that wraps around to the tail, it is essentially massive tail rocker and that pork's planning. I still feel like bevels or similar arced cross sections can help release the flat bottom surface tension and therefore launch earlier, but they have to be detailed properly so they don't cause drag at planning speeds. Your design looks like a nice balanced design in this aspect. Love the thickness with the full outline, short but stable! Perfect finish details! Tuttle and tracks! The Tuttle is a light, strong off the shelf way to connect the tracks to the deck, I built my board that way and I am glad to have the option to run both! My best mast these days is track but I use the Tuttle to gauge foil location. I make sure the Tuttle is never completely covered with the mast plate so any water can drain in flight. Keep us in the loop as you put more hours on it and really learn how she goes.
Any core or is it single skin? What the laminate schedule, EPS density and board weight?

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Bender said..

azymuth said..
About 25 cm of extra length was added to the tail over two modifications, giving more lift for takeoff without excessive pumping.

The longer tail and more forward foil create a downwind-style feel with improved glide and stability similar to a more conventional big board, while still retaining a small area nose that feels great, thanks to reduced swing weight and less buffeting when flying upwind.
At 90kgs I can now uphaul it without much anxiety

At 191 x 65 cm the board feels efficient and balanced, and the added tail area is essentially free - once up on foil, it isn't noticeable.

Testament to Mark Oz's board building skills that this is his first windfoil custom build - used for hundreds of sessions by Mr Smooth and me over 3 years yet still structurally perfect to be worth modifying

That boards getting closer to looking like my Severne Alien!!

Similar outline but his foil tracks are about a foot further forward.

I love it! I had similar results with similar modifications. Gotta love it when a mod improves performance AND is easier to use!
There is another benefit that's the SUP downwinders talk about but windfoilers rarely do. When you put weight and volume behind the front wing it helps move the center of gravity of the board closer to the front wing. This helps balance pitch. When the CG of the board is over the front wing it is one less thing that you and the stab have to compensate for.

It is cool seeing Simon's current set up next to your adaption of his old board, the same but different! It would be interesting for him to ride it and tell us what he notices about the performance differences. Pick those two boards up by the front wing like the downwinders do, I bet your new mod hangs level and Simons little ripper hangs nose down.

JJ what was your final take on that short wing board you tested? Did that motivate you to try something longer?

I have been reaching for funny names for your board because of all the edits it's gotten. The best I have so far is TRANSFORMER I can see it in orange letters like the original offering.

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Paducah said..

John340 said..
Gestalt, windfoiling would replace sailing your LT. You like sailing your LT, so it's understandable that you have no desire to windfoil

Some of us do both. I sailed five six boards in 2025: 3 4 windfoil, LT and Equipe.

* I have too many windfoil boards

Both! I love my beginner board for working out new moves and for teaching the basics to future windsurfers. I can see an inflatable longboard in my future. I have added a pump foil wing to my quiver of foils and there are suddenly very few days I can't go foiling. 2026 has already started out salty!

Wait, that board again? Is that Simon's then JJ edited like twice? And now you are kicking it some more? If so, it needs a funny Frankenstein type name or a play on terminator Let's go!

Quick update, it works! Really well! Stand by for more after I sail it like I stole it. Basically, sailing a pump foil is exactly what I have been reaching for in my first gear/light wind set up.