Regarding Figure 2 in the hydro bug post, the cross section view of the hydrofoil feet are not meant to represent what the feet do when stressed, but different options in terms of design -i.e. the feet are rigid and do not deform - this is important.
Thanks,
Kevin
It does help.
Particularly since I’m not an Engineer and my approach is obviously naïve. But language and terminology are important – and being able to mesh my analysis with those of engineering is always a plus.
Once again, you’ve provided enough information to slow me down, I’m getting there though, or I’d like to think I am.
Thanks,
Kevin
Thanks for your reply MTB, plenty there to think about, back later.
One question: Does your example of an aircraft having less drag as it acelerates past lift off speed apply if the aircraft lifts off and flies using a constant angle of attack. . . . in other words, is the increased drag at lift off speed due to the use of a high angle of attack during takeoff ? I can’t see any other reason why higher drag will occur at lower speeds in aircraft.
The answer is relevant to my own lifting foil designs because they operate at more or less constant (and low) angles of attack.
Regards,
Roy
Hello Kevin,
Your drawing looks like two inline tunnel fins with pieces cut out. … why not just complete the circle. . . more lift and less drag that way.
Looks great!
What was the total surface that you planned to use? If that’s proprietary, I’ll understand, I’ll get there on my own at some point.
Thanks,
Kevin
They do.
Thanks,
Bunkum
Is this a human hydrofoil?
Yes I see what you mean, however they don’t make an enclosed tunnel at any point in the water flow path. . . one of the advantages of an enclosed tunnel (of any shape applies also to Spuuut’s flattened tunnel) is that it reduces pressure differences inside the tunnel, this means less drag . . . that’s what I meant.
Of course the major disadvantage of any simple circular section tunnel is that it gets labelled as a coffee tin. . . too simple, not complicated enough !
Yours sincerely,
Lord Bunkum Shmungkum III
Hi Roy,
1/ If the presure is reduced, that would mean the speed of the water is increased. Isnt that Boyles Law from high school?
Would’nt it then have equal or greater drag, than an unrestricted flow, because of increased drag from friction , cavitation, turbulence, greater effect at the stagnation point?
2/ Why write 'copyright R.Stewart 2006 ’ in post 53 when you’ve stated that you dont recognise others copyrights?
I cant folllow your logic Roy on these 2 points.
I’m probably wrong on both but can you clear those up for me?
Maybe the tunnel thing is too complex for me too. ( Really!)
Regards, Brett.
And I cant believe you’ve just tagged yourself as Lord B.S. III
Yes I see what you mean, however they don’t make an enclosed tunnel at any point in the water flow path. . . one of the advantages of an enclosed tunnel (of any shape applies also to Spuuut’s flattened tunnel) is that it reduces pressure differences inside the tunnel, this means less drag . . . that’s what I meant.
Of course the major disadvantage of any simple circular section tunnel is that it gets labelled as a coffee tin. . . too simple, not complicated enough !
Yours sincerely,
Lord Bunkum Shmungkum III
Hi Roy,
1/ If the presure is reduced, that would mean the speed of the water is increased. Isnt that Boyles Law from high school?
Would’nt it then have equal or greater drag, than an unrestricted flow, because of increased drag from friction , cavitation, turbulence, greater effect at the stagnation point?
2/ Why write 'copyright R.Stewart 2006 ’ in post 53 when you’ve stated that you dont recognise others copyrights?
I cant folllow your logic Roy on these 2 points.
I’m probably wrong on both but can you clear those up for me?
Maybe the tunnel thing is too complex for me too. ( Really!)
Regards, Brett.
((And I cant believe you’ve just tagged yourself as Lord B.S. III .))
Quote:Hi Spuuut, Actually, I didn’t say that pressure would be reduced, I said that pressure differences would be reduced. . . . which is a different thing altogether. . . . according to annular wing theory, the enclosed tunnel has a more even pressure distribution. . . this means that there is less friction between pressure layers, and less speed differences between layers, this adds up to less drag.
Hi Roy,
Why write 'copyright R.Stewart 2006 ’ in post 53 when you’ve stated that you dont recognise others copyrights?
Quote:I didn’t say that I don’t recognise Copyright, I said that I don’t believe in Patents… . . . . . . . . . . . . . . . . . … Patents and Copyrights are a little different. . . . . … . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . my material can be copyrighted, but the ideas can still be used by others. … . . . . … . . . . . . … . … Slight but important difference ! Thanks for keeping me on my toes Roy
All this gabble about big drag reductions and higher speeds, flying about without touching water, etc., etc…
So what’s your fastest documented surfing speed to date?
Dear Norm,
Probably about the same as Spuuut, and 3mph slower than my son James.
Regards
Roy
If there is anyone who would like to actually manufacture, advertise and distribute foils for surfcraft, (bodyboards ,surfboards and mals inc.), please let me know. I have been making them for 2 years and I never thought anyone else would be interested at all. But with nearly 5000 views on this topic in just a few weeks, I think that shows there’s more than a casual interest here, there’s a business opportunity ! I’m ready to do this on my own, but it doesnt hurt to see if anyone else is keen.
Regards, Brett Curtis. surffoils@gmail.com spuuut@gmail.com Aust mobile (cell) 0425242883
Sure Roy. “When in doubt, dodge.” You don’t have a clue.
GILBERT RULES!
plywood and paint
and a pair of fins
cad cam eperiential reality
hmmmm?
amc …
just a kid
is the genisis of …
and the painted ponys go up and down,
will they ever surf as many waves as gilbert
go gilbert ,your wave.
My gps machine now lives in the cupboard, because the figures didnt make the surf any more enjoyable but they did shit me when I'd had a great surf and the numbers didnt reflect the way I felt. I dont think you can record stoke.30.3 kph was my highest reading from 6 months ago
That’s cool. I can respect that. But Roy has been a real twit when it comes to boasting about his alleged surfing velocities.
30.3 kph is 18.8 mph. Bodyboards without hydrofoils have gone faster!