Contact   Imprint   Advertising   Guidelines

Search found 918 matches

Go to advanced search

by JS
Tue Nov 11, 2014 11:27 pm
Forum: Hydrofoil
Topic: Hydrofoil evolution challenge #2: surface piercing foil
Replies: 86
Views: 17896

Re: Hydrofoil evolution challenge #2: surface piercing foil

A kite that's "way too big for the wind speed", as per my example, will fly at a significant downwind angle when depowered for survival. Only at very small angles of attack. Yes, that's what "way too big for wind speed...survival" refers to. Based on the Peter Lynn graph you attached, even just dep...
by JS
Tue Nov 11, 2014 12:07 am
Forum: Hydrofoil
Topic: Hydrofoil evolution challenge #2: surface piercing foil
Replies: 86
Views: 17896

Re: Hydrofoil evolution challenge #2: surface piercing foil

To illustrate, riding really fast on a current generation foil board is like flying a kite that's way too big for the wind speed. In both cases you can compensate by reducing the AoA (depowering), but that results in a drastically reduced L/D ratio, which limits performance... But that's not right,...
by JS
Mon Nov 10, 2014 8:34 pm
Forum: Hydrofoil
Topic: Hydrofoil evolution challenge #2: surface piercing foil
Replies: 86
Views: 17896

Re: Hydrofoil evolution challenge #2: surface piercing foil

Photos from many years ago TT S P F KBHFs... Interesting pictures. I notice that the collective lifting surfaces are huge compared to current generation foil boards, and I believe the heavily-dihedral geometry, likely derived from foil boats, is less than ideal for foil boards. (Seems analogous to ...
by JS
Mon Nov 10, 2014 7:57 pm
Forum: Hydrofoil
Topic: Hydrofoil evolution challenge #2: surface piercing foil
Replies: 86
Views: 17896

Re: Hydrofoil evolution challenge #2: surface piercing foil

If the CG is moved forward or rearward on a glider, you can reestablish the almost identical same speed and glide angle by trimming the elevator, yes. BUT, you have the same AOA, and not a different one :naughty: If the speed is almost identical, it means it’s not identical. If the speed is not ide...
by JS
Mon Nov 10, 2014 7:22 pm
Forum: Hydrofoil
Topic: Hydrofoil evolution challenge #2: surface piercing foil
Replies: 86
Views: 17896

Re: Hydrofoil evolution challenge #2: surface piercing foil

The two causes of AoA changes can be induced by the following means: SPEED: by pitching the board upward or downward Yes, and this is done by changing front to back weight distribution, changing A o A, like I said in my "on topic" reply concerning how to control a SPF, when you said not. J S quotes...
by JS
Mon Nov 10, 2014 11:08 am
Forum: Hydrofoil
Topic: Hydrofoil evolution challenge #2: surface piercing foil
Replies: 86
Views: 17896

Re: Hydrofoil evolution challenge #2: surface piercing foil

This pervasive AoA matter (which isn't actually the topic of this thread) is summarized by this, quoted from the beginning of the second page: For a fixed, submerged hydrofoil, AoA only changes due to speed (faster: lesser AoA) and rider's effective* weight (heavier rider: greater AoA). *I mean effe...
by JS
Mon Nov 10, 2014 10:36 am
Forum: Hydrofoil
Topic: Hydrofoil evolution challenge #2: surface piercing foil
Replies: 86
Views: 17896

Re: Hydrofoil evolution challenge #2: surface piercing foil

Maybe you're thinking too much in terms of gliders? At first I took this merely as rhetoric, but since you've repeated it, if it were grammatically structured as a question, the answer would be no. Gliders didn't cross my mind because they have variable control surfaces whereas foil boards do not, ...
by JS
Mon Nov 10, 2014 7:16 am
Forum: Hydrofoil
Topic: Hydrofoil evolution challenge #2: surface piercing foil
Replies: 86
Views: 17896

Re: Hydrofoil evolution challenge #2: surface piercing foil

So, my questions is: “Is the challenge #2 to get some kind of ‘hull’ up and out of the water, so it can ‘skip’ really fast on the waves”? Sort of. That's not a bad analogy. Even though a nicely-shaped skipping stone might get vastly more lift for skipping if it penetrated below the surface on each ...
by JS
Mon Nov 10, 2014 5:27 am
Forum: Hydrofoil
Topic: Hydrofoil evolution challenge #2: surface piercing foil
Replies: 86
Views: 17896

Re: Hydrofoil evolution challenge #2: surface piercing foil

And please address this, again from wiki; "Fully submerged hydrofoils are less subject to the effects of wave action, and are therefore more stable at sea and are more comfortable for the crew and passengers. This type of configuration, however, is not self-stabilizing. The angle of attack on the h...
by JS
Mon Nov 10, 2014 4:55 am
Forum: Hydrofoil
Topic: Hydrofoil evolution challenge #1: retractable foil
Replies: 10
Views: 3356

Re: Hydrofoil evolution challenge #1: retractable foil

zfennell wrote:perhaps retractable flaps as seen on commercial airliners would meet the criteria for this exercise?
Hadn't thought of that...variable chord. Interesting idea.

Or variable profile (thickness) foils, which get thinner as speed increases...

Go to advanced search