fangman said..

choco said..
3dprint.com/132723/3d-surfboard-fins/

Hey Choco, do you know what material they used to print with? I looked at Ultem, which was the strongest I could find. Apart from being very pricey to print, it wasn't quite strong enough for a windsurfing fin.

Not sure but found this www.shapeways.com/materials/aluminum

I finally have some Fangy MkII's about to hit the water. I tried the first one last weeked. My initial impressions of the MkII are very encouraging for me. Firstly, the lift is prodigious compared to the MkI( which is closer in shape to a conventional Delta) The penalty I suspect is, the drag is far greater. More testing will paint a better picture of the fins behaviour at speed, but the two stand out features I have noticed so far; the fin produces turbo whistle. There must be some funky harmonics going on, because once you pass the high twenties there is a low pitched whistle that increases with speed. Built in speed genie!

Secondly there is a noticeable vertical thrust. On my max speed run, the Barge was lifted clear of the water to close to where the fin leading edge began. Given my weight and the Barge as well, this is no mean feat. How much of this is down to the fillet (flange at fin base) and how much from the span wise taper on the chunky foil I don't know. I am keen to see the result at higher speed - is it self levelling or will the leading edge cavitate? Stay tuned.

The fin was sooo much better in the chop than the MkI that I was totally relaxed in the moguls at the river mouth. Normally chop and Delta shape, means lots of concentration and effort to avoid spin out. Speaking of spin out, I tried everything I could to get it to let go, but it held on happily. I have a feeling the board was a little stiffer when gybing, and harder to throw over, but it stayed planing out the other side for longer and was more forgiving with dunderklumpen weight transfer.

Fangy MkII: how good does my grass look :-)








Close up of the pitting from casting. From what I can find out, pit indentations have no effect on drag, but it would be aesthetically nicer if in future if they can be avoided at the casting stage.




FangyMk I for comparison

Well done Fang, you must be happy as so far

The whistle is from the trailing edge vorticies. you need to square up the trailing edge. or square then bevel 1 side frank Bethwaite style.

An anti singing edge. A standard detail for foils in marine use. A small edge at 60 degrees, say 0.5 or 1mm wide should fix it.

Froude said..
An anti singing edge. A standard detail for foils in marine use. A small edge at 60 degrees, say 0.5 or 1mm wide should fix it.

Thanks for taking the time and finding a diagram Froude, that's clear even to me:-)

Took Fangy's fin for a spin today and was pleasantly surprised. I actually thought the fin may have difficulties getting a purchase with the smooth finish. Not so. From the moment I took off the fin gave all the lift the 107 needed and was balanced well with a 6.4m. Conditions were a bit gusty, but the extra volume the board provided came in handy.
I was reluctant to send the fin through the weedbergs as I wasn't sure how the fin would release the weed. Wrong again, towards the end I was sending it straight at the shallower bergs and had no issue whatsoever. I did check how the fin was standing up to the punishment but it showed no marks at all.
The thing that really struck me was how comfortable the whole rig was overall. It was just crossing my mind to try for a decent hour, then Mother nature heard my thoughts, and the rest is academic.
One thing that I will mention is the leading edge, it's blunt. But smooth, and I think this may contribute to how it travels across the weed bed without so much as a tug to let you know you shouldn't be there. Next stop Albany, I think there might be some envious locals looking for less unplanned excursions around the handlebars. Well done Fangy..and No! you can't have it back!

fangman said..

pepe47 said..
Took Fangy's fin for a spin today and was pleasantly surprised. I actually thought the fin may have difficulties getting a purchase with the smooth finish. Not so. From the moment I took off the fin gave all the lift the 107 needed and was balanced well with a 6.4m. Conditions were a bit gusty, but the extra volume the board provided came in handy.
I was reluctant to send the fin through the weedbergs as I wasn't sure how the fin would release the weed. Wrong again, towards the end I was sending it straight at the shallower bergs and had no issue whatsoever. I did check how the fin was standing up to the punishment but it showed no marks at all.
The thing that really struck me was how comfortable the whole rig was overall. It was just crossing my mind to try for a decent hour, then Mother nature heard my thoughts, and the rest is academic.
One thing that I will mention is the leading edge, it's blunt. But smooth, and I think this may contribute to how it travels across the weed bed without so much as a tug to let you know you shouldn't be there. Next stop Albany, I think there might be some envious locals looking for less unplanned excursions around the handlebars. Well done Fangy..and No! you can't have it back!

Thank you Pepe! Please test it to your hearts content, preferably to its top end speed too. For those that see the fin, it will be blindingly obvious that Pepe and not me, did the re-boxing, its Pepe signature perfection. Anyone lurking down Liptons is welcome to try it out. Two proviso 's:
1) you must be wearing a back brace before attempting to lift it.
2) you may have to wrestle Pepe

Now to work on getting the weight down...

3D Metal printing hollow core or stop using cast iron

My little experiment with Silicone carbide coating and fibre impregnation is looking very successful as well hopefully give some more grinding soon