3d printing, fluid dynamics, weed fins. It's all here!
https://www.seabreeze.com.au/forums/Windsurfing/Gps/FangyFin-MkII-Theory-for-insomniacs
—
3d printing, fluid dynamics, weed fins. It's all here!
https://www.seabreeze.com.au/forums/Windsurfing/Gps/FangyFin-MkII-Theory-for-insomniacs
Interesting
Futher down the rabbit hole
Empirical testing of 3D printed parts:
https://youtu.be/scUEEQyC0GI
This video is using a 15 hp motor
By comparison to windsurfing forces
Calculation compiled by Sideskirt ( Seabreeze.com )
w=Cf*q*A
w- wind force
Cf - aerodinamic coeficient for force
q- stagnation pressure (not completely sure if it's correct translation)
A- area
A=6m2
q(18,5;37,4;55,6 km/h) = 0.185;0,374;0,556kN/m2 --> For 10;20;30 knots
Cf= 1.3 for perpendicular surface let's put it 1.15 because it is not perpendicular to all areas
P - power = w*v
for approximate power generated in your 6.0 sail, if my calculations are correct
10knots=> P=1,221kW ==> 1,67Hp
20knots=>P=2,58kW ==> 3,52Hp
30knots=>P=3,84kW ==> 5,24Hp
So.... I think it is feasible to 3D print fins
It's feasible but it will take a fair amount of hand finishing according to the rabbit hole above.
These guys do surf fins: http://westkustsurf.nl/?page_id=19153
more Sunday rabbit hole. https://www.youtube.com/watch?v=hCTQ_wgjb7M How to convert fin boxes and change rocker lines.
I think 3D print at 90 -95% of finished size and lay up CF or glass over and sand for finish size and surface finish
https://youtu.be/UtRxfi8trNs
Maybe we can play with this idea soon and do some empirical / destructive testing on the water
Unrelated but related.
https://www.indiegogo.com/projects/protocycler-free-sustainable-3d-printer-filament#/
Alan
Now my equipment will be garbage in every sense of the word.
Langdon, one of the issues of using "alternative" materials for fins is not only the "will it break" test but it's flex and twist characteristics. That's why G-10 and carbon are favored for larger fins. K4 already make plastic freestyle and wave fins but anything bigger requires something stiffer. They already tried plastic and molded glass 25-30 years ago. If you get the twist wrong, it's spin out city. CNC G10 fins are already pretty good and require less hand work. I think that you can proto pretty easily in 3d but if you are doing more than a handful, you need something that requires less human intervention. My opinion only.
Something tells me that a 6.0 doesn't generate that much power. A very good to pro level cyclist (which I am not) can only turn out 300-400 watts steady/. Most rec cyclists maybe 200-250. Pros' peak wattage is maybe 1200 w. Google says that 5 hp equals 3700ish watts.
My line of thought was creating less expensive windsurfing gear and learn some new things in the procss. ( sometimes I have to learn things the hardway... ok most of the time)
A blank piece of G10 the size of fin is very expensive.
Our shop rate for CNC's are $45 - $100 per hour
I would estimate that it would take 2 -3 hours of waterline passes to machine a fin ( 45 cm long pointer )
This being said... we make product everyday that retails for over 10 times as much as we sold it to the customer for. ( there are too many hands in the supply chain )
It is always good to develop new ways to make things. You would not believe how many manufacturing companies want to make things fhe same way because thats just how they have been doing it
I agree with you on the HP requirements are a little high
But I am curious if Peelskid was pulling me with a ski rope on my AHD and we had a load cell between me and his boat how much force would it take to bring me from schlooging to planning
Doing some more reading and it seems I'm conflating power with work.
Smarter people than me: https://groups.google.com/d/msg/rec.windsurfing/59GCe-oLq7U/qM0DmEGlt7EJ
I last took physics when the Original Windsurfer was state of the art and footstraps had not been invented.
Sadly, a lot of our gear comes from places where wages are a lot less than they are here. Decent fins new go for $100-200 depending on size and quality of the foil. They are almost always manufactured west of Hawaii. Don't go on alibaba.com, it's a bit depressing.
I was looking for a simple equation providing the power produced by a sail. Unfortunately, it is a rabbit hole within a rabbit hole.
https://en.wikipedia.org/wiki/Forces_on_sails
I believe that Power is proportional to velocity cubed, but the velocity is a complicated function of wind speed (apparent wind.)
But all is not lost - here is the greatest breakthough in fins in recent years:
https://www.youtube.com/watch?v=3yJosBzdc4Y
What happens in a black hole stays in a black hole.
Langdon, get your cnc groove on: https://www.seabreeze.com.au/forums/Windsurfing/Gps/FangyFin-DIY-help--hints-and-show-us-ya-fin-page