3 years ago I did an elaborate deep dive post:
“Ultralight wind (~5mph or ~4kt) windfoiling BAF for older "Heavy Dudes" 90kg+ and no pumping”
www.seabreeze.com.au/forums/Windsurfing/Foiling/Ultralight-wind--5mph-or--4kt--windfoiling-BAF-for-older--Heavy-Dudes--90kg--and-no-pumping?page=1

Now people ask me directly about my new “mareks360 dragonfly” config therefore It is better to share the Concept, Design and its actual Performance in my “platypus” configuration.
Why “platypus” ? You got to read the old post above.
Lets get back to where we left 3 years ago Graph:





Basic conclusion is that the bigger the foil, the earlier take off, BUT the narrowest range where the foil outperforms all the other.
Therefore we have to find different solution to reduce overall drag in wider range.
Science of Aerial drones come to help and rather than explaining complex equations, dominant vs contributing vs none-dominant factors: “picture tells the 1000 words”:





Source: “ Improvement of Micro UAV Performance using Tandem-Wing Design “
Figure7 The comparison of Drag force between the two models

Lets examine now new graph and conclusions:
1) Despite my mareks360 dragonfly config (SB M1000+800) at 1800cm2 comparable to Slingshot Quantum 100 at 1724cm2, the efficiency of twin config reduces the drag (both induced and parasitic) to the extent of faster slogging, earlier take off and faster fly when wind increases.
2) If someone guarantees me wind speed between 4-5mph, I would be the fastest on SS i99 + i84 biplane (see other post for details)
3) If someone guarantees me wind speed between 5-6mph, I would be the fastest on SS i84+i76 (my past tested config)
4) If someone guarantees me wind speed between 6-7mph, I would be the fastest on SS i99
5) If someone guarantees me wind speed between 7-11mph, I would be the fastest on SB mod mareks 360 dragonfly
6) If someone guarantees me wind above 11mph, I would be the fastest on the original SB Millenium 1000 – please note this is only up to 20 MPH wind analysis





Recommended by me Resources for your personal “deep dive and study”:
1. “ Improvement of Micro UAV Performance using Tandem-Wing Design “
2. “Twin-Wing Design Options Used for Unmanned Aerial Vehicles to Achieve High Altitudes at Low Speeds”
3. “Hydrofoil Design, Build Fly” by Ray Vellinga – Outstanding book to understand how hydrofoil works !
4. “What wing spacing is best for a tandem wing configuration?”
5. “Exploring the Different Wing Configurations Used in Airplanes”

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Here is Q & A:
From people asking directly:
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Please note that I am using 115++ in this case. There is more space between the wing and the mast to add 2nd foil.
I also have 115+ unmodified I use with SB Race 100 board single M1000 wing.

Questions:

Q: - What distance is the second wing from the first? How far back
A: Now we have to distinguish distance between the wings (which is still variable) vs distance from end of front saddle to beginning of second saddle.
Keep in mind that Starboard made wings that are not centric to the saddle therefore it will be different distance between wings (for interference sake) if I swap 800 to the front and M1000 to the back or if I use other wings I have e.g. FR1100 or 500
Distance between end of front saddle and beginning of second saddle is 71mm while distance from Trailing edge of M1000 to front edge of 800 is 127mm.

Q: - What stabilizer goes best w/dual wings?
A: Before adding second wing, I foiled this setup for 1000s of miles in M1000/115++/255(-2ver) +0.5 shim with Starboard Go 180 board. You can see my older post for pictures that I references from 3 years ago.
So I added just 800 wing and the setup is still balanced therefore I did not feel to change anything.

Q: - Any structural reinforcements when the second wing is installed?
A: Nothing, There is no need. SB 115 fuselages are solid alumunum

Q: - How did you machine the profile?
A: This was a “labor of love” with simple tools with “measure twice cut once” approach.
First I drilled the fuse horizontally with many holes. Fuse in a vise, hand drill [Upd: I meant electrical handheld drill]. Used reciprocal saw [Upd: I meant electrical] to cut out the aluminum out. Then used hand files to get to profile marked with permanent marker on the sides. Then I drilled the smaller holes and used threading tool.

Very nice design

FormuIa said..
Nice write-up, and I'd love to try it at 6 knots - conditions where I can't pump.

My question is, what's with the seemingly low speeds on SB 1000 config? In measured ~8 knots of perfectly steady thermal wind, with close to zero chop, I can easily fly 20+ knots (23 mph) with 9+ m foil sail. Freshwater speed would probably be even higher.

Formula,
There are probably at least 3 aspects that differ:
1) Total weight: sailor + gear (wetsuit, backpack, etc.) + rig + board with hydrofoil. My case measured with a floor scale: me 198LB in shorts, me in wetsuit +backpack + harness+2L water pack, foldable paddles etc.: 218LB, Rig: 32LB, Board with hydrofoil: 47LB, therefore total is: 297LB = 135kg
2) Using relevant sensor at relevant height that represent windfoiler actual wind. I am using Tempest sensors that are on docks out on the water, at windfoiler /sailor height. Please note that wind increases with height and there are graphs /calculators to scale it down (if sensor too high above)
3) Wind definition: either "gust" or "average" will let you start flying (pumping or not) but it is the "lull" that defines sustainable flight after taking off (no pumping).
I will post about it shortly.

I have an iq foil (900 front) and sail it on a sb 177 foil board.
I haven't been exactly happy about the low end - this does gets me a thinkin - a 900 and my extra 800 wing together...

Who do i know that has a cnc machine??

Q1. Marek - can you compare the takeoff speed of your dragonfly vs slingshot i99 (I used to have a i99 so I can relate to that takeoff speed)?
I understand that the dragonfly will be faster but I am wondering about takeoff speed. From your graph it looks like the i99 takeoff is a touch earlier?

A1: Yes, it is the surface 1800cm2 dragonfly M1000+800 vs SS i99 2374cm2 BUT your only gain is between ~ 6.5mph and 7.0mph wind. The efficiencies (reduced drag) from HA twins are “tipping the scale” in so many aspects.

Q2. I have the + 115 fuse. Should I still use 71mm space or could I reduce the gap? (photo below with 71 mm space)

A2: The rough idea or “rule of the thumb” is that you would like to keep one chord length between the wings to avoid any interference at higher speeds. In my case the chord of M1000 is 125mm and the gap between trailing edge of M1000and leading edge is 800 I designed to be exactly 125mm. That means 71mm between the saddles.
Now, coincidently my second wing saddle is exactly as Starboard Black 75 Fuse distance between the saddle and the mast. I knew I do not compromise any structural integrity.
See the picture:





In your case, you need to evaluate what is a safe minimum distance between front of fuse for mast cavity and end of fuse for wing cavity.


Q3. How does it turn? Does it move the centre of lift back somewhat? Any weird control issues?

A3: I do not notice any turning impact. I have not noticed any control issues.
One interesting observation (after last session) is that I may adjust a stabilizer shim slightly to be more aggressive for lift. It seems like twin configuration already makes some “self stabilization” already so I need stronger initiation to pop it out of the water with stronger nudge than original 115++ with M1000 only.


Q4. I would probably 3d print a spacer to put back in if I wanted to run it as a single foil.
A4: I was lazy enough to make a dummy insert out of plywood.
See the picture:

joe87879 said..
Great info thanks Marek.

With my + fuse, I am very close to the mast cutout if I maintain a 71mm space between the saddles. (Roughly 0mm between the mast cutout and the new saddle cutout)

Do I risk that either (1) the aluminium sides are strong enough at the mast cutout or (2) do I cheat and shrink the distance between the wings say from 125mm to 95mm (would give me about 30mm between the mast cutout and the new saddle cutout)

It looks like Marek has ~ 50mm between the mast cutout and the new saddle cutout.

Edit: AI says 30mm is the minimum I could go

Joe,
My thinking is very similar to yours. "The chain is as strong as the weakest link". The thickness of the fuse at this point is 35mm, width 25mm, making a saddle narrows fuse to about 22mm . Major forces are the upward fuse pressure on front of the mast but the torque from the riding dynamics in particular during cranking upwind (railing, hilling) can not be ignored.
BTW: This is also why I wanted the foil fit very snug in the fuse (like it is in the original port).
Also, the mast socket is at an angle therefore if you leave 30mm (on top), as you plan, it will be about 35mm space between foil port and start of foil mast cavity.
To me, there is no reason how this could create the weakest link.
Also, your plan is like my plan: If I expect wind to be consistent over 11mph (9.5kt), lulls not dropping below 7mph (6kt), I would remove 800 and put dummy plug.
My personal preference is to play with changing foil wings rather than a rig. Faster. Simpler.
Since I created "dragonfly (M1000+800)" back in February this year, I rode about 300miles on it with max board/GPS speed at 16.7mph (14.5kt) .
BTW2: You already have in the post my total weight (gear + me) ands sail size to evaluate loads I am creating.
So far the setup works exactly as expected. No interference between wings.
I am really happy with the setup therefore I am happy to share what can help others too.

Any foil ready board built in the last 6 or 7 years would more than likely never break. All the brands build them reasonably strong.
Anyway sounds like you have options.

The answer to hitting max speed in light wind has actually been around since the 80s: Div. 2.
Maybe you can find some inspiration in this thread:

www.windsurfing33.com/forum/viewtopic.php?f=42&t=121365

Bellerophon said..
The answer to hitting max speed in light wind has actually been around since the 80s: Div. 2.
Maybe you can find some inspiration in this thread:

www.windsurfing33.com/forum/viewtopic.php?f=42&t=121365

Bellerophon & Utcminusfour,

Argument: “The answer to hitting max speed in light wind has actually been around since the 80s: Div. 2.”

My perspective:
We tried and compared in light wind races pretty much everything.
Actually Crit D2 is not the fastest in the lightest wind. It is Serenity, then Mistral Superlight I at par with CritD2, then Mistral Superlight II.
Each board has its specific wind speed “sweet spot” (max performance).
BTW: There is a video of Balz Muller putting Serenity on hydrofoil. So as an experiment, it can work.

Q1: How to distinguish Real Science from Manufacturers Propaganda
A1: When a Manufacturer “sells you idea” and you go and verify on the water, you only gain is “weight loss” … of your wallet ;(

Q2: What can we learn from Windsurfing Evolution & snow skiing / snowboarding (both watersports)?
A2: Try cross country skis (long and narrow) on powder. Wrong way ? You need wide front skis that stay on top. Also planes, airfoils & hydrofoils efficiency comes from High Aspects.
Windsurfing Evolution: This is exactly how windsurfing started with long and narrow boards, then short narrow boards, then short and wide boards (Formula Windsurfing) evolved.

Here is the pic from the document on-line: "tuning-formula-gear_windsurfing_competion_0299v01.pdf"





Wide board (with large sail) bounces off the chop/waves, stays on top. Also e.g. double V concave bottom keeps water from escaping to the sides (in planes, winglets are added to reduce vortices).





Traditional longboard sinks in the chop/waves because the water escapes to the sides.

Slingshot Flyer 280 Practical Truth from my Experience:
Despite the “Marketing Video” from Andy Brant (also earlier from Tony Logosz himself) in link from Bellerophon (discussion in French) it is a board that has not been designed for foiling in light winds at all !
It is a board designed to do a little bit everything from SUP, Windsurf, Windfoil but completely flawed for foiling. I did test it in winds up to 34mph gusts!

Another proof: If it was such a great design then why Slingshot sold only few and discontinued it?

SS Flyer 280 flaws for foiling:
1. Hydrofoil Slingshot Mid-Tuttle box is so far back – I even tried it in Reverse B fuse.
a) It causes tremendous “swing weight”
b) It makes transition from displacement to foil assisted planing inefficient & ineffective
2. Slingshot Flyer is long and narrow – wrong design for early planing (like the cross country skis for the powder)
3. Horrible technology: every picture of used flyer you will see how it was dented, patched up, cracked in the front. It is a Styrofoam log with thin coat of glass fiber laminated on top.

I guess we did a large Detour from the topic of Hydrofoil for ultra light winds to Board designs and what they actually, factually do in practice.

I hope people can learn from it and apply towards steep learning curve, Joy of Windsurfing & Windfoiling to the Max.

FormuIa said..
Marek, what about a wide board that's designed with displacement in mind? Something like this: www.elix-funboard.com/index.php/condor-concept/

Benjamin Tillier said it's quite technical to ride, but it might be worth exploring this direction. IMHO, you want an efficient board shape that starts to glide and gain speed while in non-planning/non-foiling mode as efficiently as possible, while offering enough leverage or width to be able to load the foil once flying.

And maybe paired with high aspect, downwind-like foil, something like Starboard MF collection. But, $$$...

I had spent my lifetime career in Telecom Industry traveling around the World introducing what I call "Bleeding Edge Technologies".
Please note: I am explicitly highlighting "Bleeding, Blood, Suffering, etc.". These Technologies were pushed, due to competition, without properly maturing first.
After windsurfing for 46 years, I would love to use proven pieces of Technologies to optimize and maximize positive experience on the water in my Gusty 5-20mph winds where often lulls drop It to 0.
Now when it comes to Condor-Concept - To me it is similar to Starboard Concord-Concept from 2018 .
Here is the link and the pic from that website:
starboardfoils.com/pages/2025-iqfoil-intro



To me there is a red flag. If this 2018 "Cool Concept" did not take off by storm by now, there must be a good reason.

I can only speculate: Maybe like it Aviation Concorde predecessor: "some wheel" somewhere disintegrated and catastrophically raptured "some fuel tank".

BTW: Starboard has further (intentionally or unintentionally) improved for slogging later generation of Foil Race Boards in 2022 but I am not going to upgrade board each year.





Comparing to mine 2021 SB Race 100, Starboard added, on top of one layer of cut outs, a second "oval like" layer.




I guess, with unlimited amount of money, someone could test unlimited amount of options.
BUT, Please, I have already spent a lot of money, time and effort to bring you to this point with my postings.

Hydrosurf said..
You might be able to to repair the go board, or build your own.

This^^^


the board is currently “destroyed beyond repair.” If you have the materials /time/some understanding of how to do it, and the board serves your purpose better than another one would, then destroyed beyond repair is exactly the required excuse to try and fix it, and improve it too.

why not rebuild it back to something better by adding a foil box and giving it the required re enforcement for foiling?

Going back to the Main Topic of : "Twin foil modification from Starboard Race Q & A"

I have no business association /relation, apart from just being a "regular customer", with North Beach Windsurfing Florida.
BTW: I am still with many of you, my Aussie Beverens, on the Pacific Coast (just on the other side).
I don't get any commissions nor special discounts from North Beach Windsurfing Florida.

However, when I see a deal, I am always willing to share the "good news".

So if you are looking for "legacy" Silver Fuse 115++ (don't mix with newer "Evolution"), it is going to cost you about $349 USD here is the link:
www.nbwindsurfing.com/shop/Foils/Starboard-Foils/p/Starboard-Foils-Fuselage-Plus-and-Plus-Plus-x44396313.htm

HOWEVER:
North Beach Windsurfing Florida had a flooding event in the past which mostly damaged they boxes, packaging, etc.
They are still offering a really "sweet deal" that is sort of hidden from the view. I don't know why they do it. It is not in their interest to hide it.

So you have several options, the default one is "95cm Plus" BUT none default one is "115cm Plus Plus (B condition)".
I actually purchased one set few days ago with 115++. It is on its way being shipped.

You can chose Carbon or Alu Masts 85 or 95
You can chose 800cm front foil while 650cm front foil is already out of stock

What does it mean ?
You can get the cheapest option, complete foil set with 115++ fuse for adding second foil (if you want to) for $699 USD ?! Say What ?!!

Hey, as you celebrate Down Under Christmas twice. I still remember they did it in Blue Mountains near my beloved Sydney NSW (I lived in Lindfield on North Shore).
I might have just provided an idea for Christmas Present :)

Link:
www.nbwindsurfing.com/shop/Foils/Starboard-Foils/p/Starboard-Foils-Plus-800-Foil-Kit---A-condition-x99006790.htm

Screenshot:

Someone is going to be: Happy, Happy, Happy ! (Like in the song).

Happy Foiling to Everyone !

FormuIa said..
I can think of a number of reasons why efficient displacement boards haven't become popular:
- they're technical to ride, as mentioned earlier by Benjamin Tillier
- "nobody" uses WF in conditions below 7 kt average wind where those boards would outperform regular boards. 7 kt and above is doable with existing traditional gear with excellent pumping technique
- there's an everlasting tendency to use the smallest possible equipment and, as a result, the focus of majority is on 10+ kt wind (see how formula windsurf and formula foil ended...)
- kitefoil is much more efficient and faster below 7 kt
- most of the people simply prefer other sports in such conditions ...

I also use a 1000 SB race wing and the largest 9-10 m2 sails 95 % of the time, but this equipment is practically dead; everyone focuses on smaller/slalom gear or wing/kite. Doesn't mean the gear isn't good or that a displacement hull wouldn't be a hit in those rare conditions - it might just be a simple market size, profit-driven thing.

Even the Elix company itself cannot market the board properly; for starters, they should show a comparison in ultra-light conditions between the Condor board and another planing WF board to see the planing, ease of pumping difference, and speed ...

Formula,
You do worry me. I think you need some "cheering up".
Remember: "every day is a gift" and we have been making progress in technology for decades.
Back in the early 1980s, I had to pull up a centerboard up (approaching shallow water) because rotational one was not yet available.
Then from Original Windsurfer came Windglider, that was already more stable and joyous to ride.
Then came cambered sails. Wow, that was progress in stability.
In my video from late 1990s -2000 in Sydney on Botany Bay & Barrenjoey, you can see what a tremendous quantum leap in happiness I am making going from old heavy Mistral Maui, crappy sail, metal on piece mast, crappy boom to..... Rick Murray (KA-4) rig: Fiberspar carbon mast, Fiberspar carbon race boom, Gaastra Total Flow F1 sail 8.8m - wow, that was a progress !

Now, lets jump to about decade ago circa 2016 when we started to see people adding hydrofoils to windsurfing gear and other sports (like kiteboarding).
Then came wing foiling.
Now you have people with hydrofoils also : wake boarding, foil surfing, pump foiling, SUP / down wind foiling, para wing foiling, E-foiling, e-foil assist (for other sports), etc. etc.

Technology gives us options to enjoy TOW (time on the water) more and more !

Having Forums like Seabreeze allows people to share what and how it works for them in their specific conditions.

There is so much to celebrate.

Industry obviously wants to make a profit (as you pointed out), It is obvious that they will focus on Mainstream because "these are Economies of scale" (volume drives lower cost per unit).

I will wrap up with an old Wisdom: "We have no influence over what cards the live gives us (and what kind of wind at your location) but it is all about how you use/play/customize them (and boards, sails & foils) ".

Here is how I used windsurf board sometimes in an "alternative way" back in 1980 being towed behind a sailboat.

"The more ways, the merrier" !

FormuIa said..
It's a simple fact that for those of us who enjoy windfoiling under 10 knots, the gear is disappearing.

Board is the easiest to solve, it can be custom-made or even made at home. Brands have phased-out 1 m wide course-race boards.
Sail, not so much. Once 9-10 m2 course-race foil sails such as Severne HGO are gone, what is left? Patrik foil sail that requires a dedicated, expensive mast? Even 550 Severne mast is now hard to get.
Foil can technically be solved using high-aspect, downwind-style wings, provided you can get a long fuse.

I can't be cheered up by the fact that when I got my FW gear upgraded to steroids with foils and increased TOW twofold, the new gear has now disappeared. That's why I'm buying and hoarding a few large sails to have a backup plan and spare.

There might be a Solution to bring back Large Sails and other Ultra Light Wind gear (from going extinct).
The answer might be in Health / Longevity Industry.
People are often obsessed on a Quest of finding an “elixir of youth”.
BTW: I might have found one but it can be:
1. Windsurfing/Windfoiling – long sessions
2. Swimming - long sessions
3. Combination of both above
“Association” is not necessarily the “Causation”.
You may ask why and how?
We used to talk in Telecom Industry about KPIs.
Meaning: Key Performance Indicators:
In Health, there is an obsession about VO2max. I was lucky enough living in Australia and in 1999 I had real V02max test done with the mask on your face and real oxygen consumption tested.
People will freak out: my VO2max was at 45 ml/kg/min, yes 27 years ago, and now it is at 44 ml/kg/min, and I can train to get it higher if I want to (I did last year).
Second KPI is Max HR (Heart Rate). I had it measured in Australia back in 1999 and my HR Max was 191 BPM.
Normal Aging is that every year you lose 1 BPM for Max HR. There is even a formula Max HR =220 minus your actual age.
Now I can get my heart to 180 BPM (more regularly to 178 BPM).
What does it mean ?
I either only aged (from this KPI) 11 years biologically in chronological 27 years.
My biological age suppose to be 40 (according to formula) but my chronological age is 56 year young.
If you are interested in the details, I posted it in my "effortless 1 mile butterfly swim" video at the timestamp around 10 min in the video.

Thanks to Marek's suggestion, I have successfully built and tested "Franken-Foil".
Sailed it in 8-10kts, wavy, 8.0 Ezzy Cross. Much better lift, slower speed but pretty good (16kts on apple watch). It felt almost no different although the lift is slightly further back.
I'm running 900 up front with a 800 in the back.
Local machine shop cnc'd the fuse for me and I chopped the back part of the 800 wing to maintain a gap to the foil mast.
I have to tune my mast rake a bit more forward. I was at -1.5 degrees and now with a shim I'm at -3.5 degrees which is too much.
Lots of fun experimenting - thanks Marek!

Well done. 👍