I thought I had pushed the fair go rule far enough hijacking Macroscien's thread, so I will start afresh. This is the first Fangy fin in Aluminium complete to a smooth finish. 55 degree rake to handle thick weed and burgs. I now need to try it out against some weed and see how the leading edge fares. If it's looking promising and holding up better than G10, the Mk II will be cast and I will see how that behaves...stay tuned :-)
The Mark I above ready for crash testing. The Mark II below will follow if all goes according to plan.
Imagine that thing annealed and anodized! Looks amazing as it is. Keen to hear how it goes.
I like the cutout of the MkII. Keen to hear how they go... a video would be even better :)
Looks great.
From memory Dunkerbeck experimented with Aluminium fins (pointers though) at some stage but all failed unfortunately (fatigue failure?).
Pretty sure there's a video floating around but cant find it just yet.
Hopefully you have a better outcome.
Select to expand quoteThe Windsurfing Shed said..
Looks great.
From memory Dunkerbeck experimented with Aluminium fins (pointers though) at some stage but all failed unfortunately (fatigue failure?)...
I am hoping that the thickness off the base and the short overall height, will guard against fatigue. The Mark II are thicker again and filleted to try and distribute the stress more evenly across the base area. But time will tell if I got that right...
Select to expand quoteThe Windsurfing Shed said..
Looks great.
From memory Dunkerbeck experimented with Aluminium fins (pointers though) at some stage but all failed unfortunately (fatigue failure?).
Pretty sure there's a video floating around but cant find it just yet.
Hopefully you have a better outcome.
maybe with a pointer it could have been a flex issue , weed fins are thicker and don't need flex , I think fangy is on the money with the flange around the base and maybe solve a few cavitation issues at high speed and chop
Select to expand quotefangman said..The Windsurfing Shed said..
Looks great.
From memory Dunkerbeck experimented with Aluminium fins (pointers though) at some stage but all failed unfortunately (fatigue failure?)...
I am hoping that the thickness off the base and the short overall height, will guard against fatigue. The Mark II are thicker again and filleted to try and distribute the stress more evenly across the base area. But time will tell if I got that right...
Mal Wright built some aluminium slalom and speeds fins way back in the late 80's or very early '90's. As I understand it, Ian Fox has one or two, and I have a couple in my speedsailing museum, a 20cm deep US box assy speed fin (first fin I did 40 knots on! 
) and a symmetrical slalom pointer at about 32cm deep. They were actually machined with a CNC machine and hand finished to remove the machining marks. AFAIK, he didn't have any failures with them. I think modern CNC machinery could do a far better job of them, Mal had the TM series fin moulds machined from aluminium blocks in the early 2000's and they only required very fine surface finishing before use. G10 fins are made with CNC machining, and it is my understanding that they usually require very little final finishing.
I'm not sure which one this is, but it is an early one. I think it is the TM-26 Alpha fin, but it could be the TM-V6 assy speed.
But sand castings can also be made with quite a fine finish from my experience with casting skateboard (WindWheeler) trucks.
I really wanted to CNC my fin, but the quotes I got in Australia ( from the few that actually bothered to get back to me) the cost for set up and mill was uber expensive. So sand casting was the only way I could afford to do it. I suppose if you are making stacks it becomes a different story.
great ally mold sailquick and ahead of its time late 80's but it looks to good to be true 
Select to expand quotefangman said..
I really wanted to CNC my fin, but the quotes I got in Australia ( from the few that actually bothered to get back to me) the cost for set up and mill was uber expensive. So sand casting was the only way I could afford to do it. I suppose if you are making stacks it becomes a different story.
Yes, that is quite understandable and makes great sense. I love ya work! 
sorry daffy but I was mainly looking at the pic of the mold , perfect fin in the mold with no spillage 
Yes Keef, Mal and Tom had it down to a fine art in the end. There were a few rejects on the way there though!
This one was easier to get right as some excess resin could exit at the root end. I'm stuffed if I know how they managed it so well with the other moulds that included the whole head and were virtually closed. http://www.intellimass.com/TM45/TM45_Mould.htm
Hey Fang, you should be making alloy dentures
Jokes aside great work mate, good onya
Peter Clifford in FNQ used to make and market aluminium fins moons ago, I think they were hollow and I don't remember ever seeing any break. He's still using alloy fins, just saying
Select to expand quotefangman said..The Windsurfing Shed said..
Looks great.
From memory Dunkerbeck experimented with Aluminium fins (pointers though) at some stage but all failed unfortunately (fatigue failure?)...
I am hoping that the thickness off the base and the short overall height, will guard against fatigue. The Mark II are thicker again and filleted to try and distribute the stress more evenly across the base area. But time will tell if I got that right...
Fangy, I think you need to look into heat treatment for strength & hardness.
What grade / alloy is it?
Annealing will soften it, this is done by heat treatment also but different temperature - 400 deg C & air cool.
Something like 180 deg C for 8 hrs might harden it up depending on the alloy.
Aging is probably the best for a tough exterior oxide surface, this can also be done artificially with heat treatment.
Firie - I will leave the alloy fangs to Wazzatoothfairy.
Aus 808- thank you for the help (again:-). I didnt specify any alloy this time, I wasn't even sure whether it could even be done and it was hard to find a foundry that would do such a small job.. If the first fin works ok, I will have to look at the costs to use a better alloy and heat treat. Thanks again for the info.
Nigel: All my Rake 30 ° have cut outs. The first who made 50knots topspeed was Martin van Meurs. the second was Thomas Döblin with the
22cm Rake 30". Cut out and doubleasymm. The concaves are diagonal. Wolfgang
Christian Bornemann and Franz Grabner ( Austria) made with the new B+F in Rake 30° a good speed. No Cut out and no concaves.and 8mm thin
or thick. For Lüderitz is the left side 3mm thinner. I worked now in such a fin diagonal concaves in, must she work a little thicker,good 9mm. And no
joke,she is 2knots faster.She is tested by Klaus Küppenbender. He was 15 years ago one of the fastes speeder in Germany. The next fin is
rake 30° assym. diagonal concaves and the cut out. Wolfgang
Select to expand quotesailquik said..
G10 fins are made with CNC machining, and it is my understanding that they usually require very little final finishing.
A fin developer in the US told me that most G10 fins made in China actually need quite a bit of finishing work, since the CNC machines are a big factor in the cost of the fins. Run them at rougher solution, and you can get more fins out of the same machine. Hand polishing is comparatively cheap, at least in China. That may explain some of the variability in G10 fin performance.
But it does not apply to all G10 fins - some are made on machines that run slower (more paths at higher resolution), and also use higher quality G10.
Select to expand quotefangman said..
The Mark II below will follow if all goes according to plan.
That's a real beauty!
so good to read a thread that is not about GPS units.
Fangy that first one looks a lot like a shark fin. As far as hyrodynamics goes, anything that follows nature has to be on the right track.
...and if it doesn't work you can always strap it to your back and go swimming at Cottesloe to scare the life out of the other swimmers
I worked in 1980 some fins in Titanaluminium. I got it from Austria. They were the fastest fins I ever worked, I saw the fins in Aluminium from Dunkerbeck
to thin and the stiffness was not so good.To much work,and when I read here something over vibration in this forum,a good idea but I am 75 years
and I hope that a fin from me make the fastes run. 100% carbon,cut out, concaves and asymm. Wolfgang
My handmade Aluminum 21/25. Seems to work fine. Have had 35+knots in less than ideal conditions. Wears well through the mud compared to G10 or carbon
Next step will be 3D Printing new fins. Everybody then could order most crazzy shape and have printed in single edition at reasonable prices.
Actually the most critical parts of rocket engines are being 3D printed and perform better then everything else. Obviously I think about printing in metals or alloys ( using lasers) , not flimsy staff from hot glue gun printers.
3D printing whole boards should be even easier.
Dan133: It seems to be a fin for one way, the most worked leewards flat like now. They used right and left fins. But a concave is faster. Concaves
on both sides from base to tip do not work. Only diagonal 60% concave from the base and on the other side 40% concave from the tip. that works
tour and retour, no spin outs. Air bubbles from the bottum comes to the fin ,we go in an angle of good 10° leewards , so water and bubbles goes in
this angle from leewards to the other side through the cut out and jump horizontal out. Bubbles cannot go down at the end of the fin. Wolfgang
I carved it out of 10mm 5005 aluminum.(I used an angle grinder) Grain running the length of the fin. Mike(Te hau) boxed it for me, Heres the construction. www.seabreeze.com.au/forums/Windsurfing/Gps/Construction-of-my-own-eyeometrical-speed-fin/
I Like working with the material. Make all sorts of things.
Select to expand quoteFangy said..
I thought I had pushed the fair go rule far enough hijacking Macroscien's thread, so I will start afresh. This is the first Fangy fin in Aluminium complete to a smooth finish. Select to expand quoteLessacher said..
Dan133: It seems to be a fin for one way, the most worked leewards flat like now. They used right and left fins. But a concave is faster. Concaves
on both sides from base to tip do not work. Only diagonal 60% concave from the base and on the other side 40% concave from the tip. that works
tour and retour, no spin outs. Air bubbles from the bottum comes to the fin ,we go in an angle of good 10° leewards , so water and bubbles goes in
this angle from leewards to the other side through the cut out and jump horizontal out. Bubbles cannot go down at the end of the fin. Wolfgang
Don't think you should worry too much about thread hijacking Fangy, seems par for the course here
