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=1Now 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”
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Here is Q & A:
From people asking directly:
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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.
