Are you sure it's due to trailing edge finish? I mean, draggy noise/behavior, like foil scraping the water instead of cutting, could also be due to surface imperfections. Bubbles adhere at the surface. At higher speeds these bubbles can implode and affect the wing's lift (ventilation effect). However, if the foil is whistling, it's usually due to the trailing edge finish. Here's a picture that I've got from this post https://windfoilzone.com/why-is-my-hydrofoil-whistling/ that shows the vibration amplitude according to the trailing edge finish.Cefirmeza wrote: ↑Wed Jun 01, 2022 10:31 pmI am experiencing turbulence and draggy noise when riding at low speeds. Already sanded both mast and back wing trailing edges both sides at 30 degrees and still there. I did more than 20 pre session sanding and now it is quite sharp. What would happen if I sand them square tips at 90 degrees?
You mean TRAILING EDGE !!!rnelias wrote: ↑Thu Jun 02, 2022 1:50 pmAre you sure it's due to leading edge finish? I mean, draggy noise/behavior, like foil scraping the water instead of cutting, could also be due to surface imperfections. Bubbles adhere at the surface. At higher speeds these bubbles can implode and affect the wing's lift (ventilation effect). However, if the foil is whistling, it's usually due to the leading edge finish. Here's a picture that I've got from this post https://windfoilzone.com/why-is-my-hydrofoil-whistling/ that shows the vibration amplitude according to the leading edge finish.Cefirmeza wrote: ↑Wed Jun 01, 2022 10:31 pmI am experiencing turbulence and draggy noise when riding at low speeds. Already sanded both mast and back wing trailing edges both sides at 30 degrees and still there. I did more than 20 pre session sanding and now it is quite sharp. What would happen if I sand them square tips at 90 degrees?
a4ab0b_599a31cada8f4b81970f47496a975695_mv2_d_1724_1588_s_2.png
from this picture, the worst case scenario would be sanding it at 90 degrees
rnelias wrote: ↑Thu Jun 02, 2022 1:50 pmAre you sure it's due to trailing edge finish? I mean, draggy noise/behavior, like foil scraping the water instead of cutting, could also be due to surface imperfections. Bubbles adhere at the surface. At higher speeds these bubbles can implode and affect the wing's lift (ventilation effect). However, if the foil is whistling, it's usually due to the trailing edge finish. Here's a picture that I've got from this post https://windfoilzone.com/why-is-my-hydrofoil-whistling/ that shows the vibration amplitude according to the trailing edge finish.Cefirmeza wrote: ↑Wed Jun 01, 2022 10:31 pmI am experiencing turbulence and draggy noise when riding at low speeds. Already sanded both mast and back wing trailing edges both sides at 30 degrees and still there. I did more than 20 pre session sanding and now it is quite sharp. What would happen if I sand them square tips at 90 degrees?
a4ab0b_599a31cada8f4b81970f47496a975695_mv2_d_1724_1588_s_2.png
from this picture, the worst case scenario would be sanding it at 90 degrees
Yep... these configurations would give higher vibration amplitude (noise usually comes from short and high frequency vibrations though). This diagram came from “Principles of Yacht Design” book by Lars Larsson and Rolf E. Eliasson. There's a session devoted to Keel and rudder design. I have this book and the paragraph regarding this Figure is bellow:Trent hink wrote: ↑Fri Jun 03, 2022 9:28 pmI'm not the sharpest crayon in the box, but based on my interpretation of the chart you posted, it seems like #2 and #3 are the worst case scenarios?
When I built the rudder for my outrigger sailing canoe, the information I gathered (from boat building forums) suggested that sanding the trailing edge down square to about 1-3 mm wide was the best way to go.
Granted, most sailboats go much slower than most hydrofoils,
and usually the tolerances are not nearly as close, so for sure it is not quite the same thing....
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