Dear Mr. Sidecar

Jethrow

Jethrow

Super Anarchist
1,893
633
Pittwater, Sydney, Australia
Hell-Bent said:
If your electronics go out and you don't have power to inflate the sails, you've got a problem
Click to expand...
They come with this manual option too... :cool:
1665439431737.png
 
Sidecar

Sidecar

…………………………
3,241
1,630
Tasmania
Sidecar said:
So ~ 40% reduction of induced drag…..
View attachment 543778
Click to expand...
Speaking of ground effect.

Sidecar has a single inverted airfoil wing. Done for drag reduction, weight to windward storage, secure footing/trafficking (a proper deck to walk around on) and spray deflection/dryness, I was also aware of maybe potential downforce, especially as it was so close to the water.

Other potentially assisting factors are, that if you took slices through the aka at (AWA) 30 degrees, the sections are no longer symmetrical, but asymmetric (~ 18% thickness @ ~ 37% chord length), due to platform taper, and an AoA of ~4 degrees at outboard end due to differential aka wing droop/dihedral. Aka wing area is pretty much the same as half a Cessna 152 with nearly triple the average chord thickness. The section asymmetry increases with AWA, up to a point where it becomes useless.

Assuming 0.3 CL at 0 degrees AoA and 40% ground effect, you come up with some fag packet theoretical numbers:

16 knots TWS, ~ 30kg downforce @ 3.00m righting arm. As per video, Peanuts.
40 knots TWS, ~ 90kg downforce. Ie an extra crewman sitting @ 3.00 m righting arm.
100 knots TWS, ~ 450 kg downforce. Righting arm academic on a boat which weights just under a tonne.

No way for me to measure or calibrate, but Sidecar sits steady on her mooring as well or better than much heavier and bigger boats in the Sound and on the trailer next to the house and oriented towards the wind, the chocks which partially support the ama have never fallen out, no matter how lightly they were put in (to see what would happen). And it can get pretty windy down here, especially in the gusts.
 
MultiThom

MultiThom

Super Anarchist
1,795
430
Benicia, CA
Sidecar said:
Speaking of ground effect.

Sidecar has a single inverted airfoil wing. Done for drag reduction, weight to windward storage, secure footing/trafficking (a proper deck to walk around on) and spray deflection/dryness, I was also aware of maybe potential downforce, especially as it was so close to the water.

Other potentially assisting factors are, that if you took slices through the aka at (AWA) 30 degrees, the sections are no longer symmetrical, but asymmetric (~ 18% thickness @ ~ 37% chord length), due to platform taper, and an AoA of ~4 degrees at outboard end due to differential aka wing droop/dihedral. Aka wing area is pretty much the same as half a Cessna 152 with nearly triple the average chord thickness. The section asymmetry increases with AWA, up to a point where it becomes useless.

Assuming 0.3 CL at 0 degrees AoA and 40% ground effect, you come up with some fag packet theoretical numbers:

16 knots TWS, ~ 30kg downforce @ 3.00m righting arm. As per video, Peanuts.
40 knots TWS, ~ 90kg downforce. Ie an extra crewman sitting @ 3.00 m righting arm.
100 knots TWS, ~ 450 kg downforce. Righting arm academic on a boat which weights just under a tonne.

No way for me to measure or calibrate, but Sidecar sits steady on her mooring as well or better than much heavier and bigger boats in the Sound and on the trailer next to the house and oriented towards the wind, the chocks which partially support the ama have never fallen out, no matter how lightly they were put in (to see what would happen). And it can get pretty windy down here, especially in the gusts.
Click to expand...

Nice that you calculated that it doesn't matter.
 
MultiThom

MultiThom

Super Anarchist
1,795
430
Benicia, CA
Hell-Bent said:
So you don't believe in light boats? Only in heavy, slow boats that can use only gravity to stay steady when other external forces like wind are acting on them?
Click to expand...
I have a boat that weighs half what yours does. It is also sailed routinely in very large winds (but not big waves). But it is a day sailor so yah, I do trust gravity as well as viscosity of the water to keep it sucked down and not airborne. I was only tongue in cheek for admonishing Sidecar for doing calculations--he was just preening that he knew how to do it regardless of its uselessness. Like me, he is likely just bored and nothing better to do. IN case you are questioning the winds I sail in, the screenshot is from my last sail. The windspeed wasn't the issue, it was the big shifts.

Screenshot 2022-10-01 15.42.03.png
 
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Sidecar

Sidecar

…………………………
3,241
1,630
Tasmania
MultiThom said:
I was only tongue in cheek for admonishing Sidecar for doing calculations--he was just preening that he knew how to do it regardless of its uselessness. Like me, he is likely just bored and nothing better to do.
Click to expand...
If I had the more conventional ama arrangement, those numbers could easily be mirrored, in which case, my boat would flip. It may not interest you, but others on this thread have seen multihulls tethered like kites, flailing in a storm, due to gravity no doubt.

Even the “peanuts” down lift is an indication that the wing is doing something positive, not negative for the overall performance of the boat, as is the case for the conventional aka and netting arrangement.

Happy to take every small positive I can find…. And you preen yourself about sailing routinely in very large winds, where the “peanuts” positive would be larger.
 
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M

munt

Super Anarchist
1,326
324
The belt
Wow, that's an amazing vid. A similar event occurred with a docked R33. Seems like in a tornado all bets are off and any object is liable to get launched (including cattle). The bigger, more important questions is, how does one participate in the "Preening" contest. I have virtually no special skills or knowledge but I'm determined to get involved!
 
M

munt

Super Anarchist
1,326
324
The belt
Any quantum physicists want to explain gravity in a way that a cro-magnon such as myself could comprehend. My math ability is "single digit addition" max!
 
Hell-Bent

Hell-Bent

Member
94
52
Vancouver, BC, Canada
That's what you get when you distill a fast sailboat down to the very bare minimum.

ProaSailor, I didn't embed the video because I was posting from the mobile site and it wouldn't embed a video link from the YouTube app, not because I couldn't be bothered...
 
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