elmo said..
Fangy,
how is the accuracy on the printer?

I spoke to a printing company about achievable tolerances looking to make fin molds and they advised that they weren't able to get near a 0.1mm tolerance is this still the case?

0.1mm tolerance is possible, for small items. I've been working on a set of lego-style playing pieces that require 0.02mm tolerance max to achieve good interlock, and they work quite well.

The issue with larger pieces is that although your print head deposits the plastic in exactly the right place, the plastic then sits there and slowly cools down. As it cools, it shrinks. And so grabs the piece of plastic next to it and pulls. You end up with all these small pieces of plastic pulling on the one next to them... which causes the whole print to slowly warp, throwing your tolerance right out of the window.

You can alleviate this somewhat by using an enclosed chamber (which keeps the temperature more stable, and hotter), as well as using a cooling fan right on the nozzle (which cools the plastic quickly). Different plastics also shrink at different amounts. There's a bit of science, a bit more art, and a whole lot of experimentation that has to be done before you can attempt a larger print such as this one.

Here's a photo showing the core box being printed, you can see the black cooling duct just to the left of the nozzle, this blows cooler air at the print. Each type of plastic requires different cooling strategies.


If you want to get a glimpse of the lengths of backyard bodgery that I went to, just to get a reliable printer, then check out this link:www.thingiverse.com/thing:2040390

All dressed up and nowhere to go. The prints and core boxes are completely finished. The foundry I hope to use, comes back from holidays tomorrow, so hopefully I will have some good news by next week and the prints will have a party to go to.

Side-by-side:20 CM + 24CM (the 20CM has just over 200sq.cm, the 24 approx 350sq.cm) and partial 28 CM

20CM, 24 CM AND 28CM (The 28 has a slighty thicker lip to allow for more board rocker forward )



24 CM AND 28CM - SIDE BY SIDE COMPARISON (the 28 has just over 500sq.cm surface area)

John340 said..
Nice deck

That's unbelievable John! I was just about to add at the bottom of the post,
"and dont even think of telling me I have lawn beetle or termites John" and you beat me to it.

They look awesome Hopefully it's all smooth sailing from here on in!

Fangy, slugger and Swindy gave the proto types are good work out at Boombas today. They were certainly going very well.
www.gpsteamchallenge.com.au/sailor_session/show?date=2017-07-27&team=2
Some very nice PBs in there too.

rogerswin said..

decrepit said..
Fangy, slugger and Swindy gave the proto types are good work out at Boombas today. They were certainly going very well.
www.gpsteamchallenge.com.au/sailor_session/show?date=2017-07-27&team=2
Some very nice PBs in there too.

so good that I have claimed the 24 proto as my own until I get one of the new ones. I am even using a security head screw to bolt it in my board so fangy cant pinch it back.

That worries me a bit Swindy, if you are using the bolt I think you are, what bolt are you going to use to keep your head on?

Are you ready for the next twist in the tale? The only guy I could find in Aust who could do the fins at a reasonable price has been called up for Jury Duty and is out of action for the time being...

All the commercial level casting workshops I tried, either didn't return my calls, or were sympathetic, but simply could not do a small run at a competitive price. After chatting to Decrepit about being really torn between making the fins and my personal goal of doing the whole thing in Australia, I have resigned myself to the manufacture of the fins overseas. This is a really big ethical compromise for me, and if any one who has ordered a fin, feels it is too much of a compromise for them, and wants to cancel their order, I fully understand and just pm me.

Just to add insult to ethical injury, in just one afternoon, I had received expressions of interest from 12 Casting factories in China and solid quotes from 6 of them, as opposed to the three months I spent trying to find any one to do the job here.

Standby for the next ridiculous episode.

fangman said..
Are you ready for the next twist in the tale? The only guy I could find in Aust who could do the fins at a reasonable price has been called up for Jury Duty and is out of action for the time being...

All the commercial level casting workshops I tried, either didn't return my calls, or were sympathetic, but simply could not do a small run at a competitive price. After chatting to Decrepit about being really torn between making the fins and my personal goal of doing the whole thing in Australia, I have resigned myself to the manufacture of the fins overseas. This is a really big ethical compromise for me, and if any one who has ordered a fin, feels it is too much of a compromise for them, and wants to cancel their order, I fully understand and just pm me.

Just to add insult to ethical injury, in just one afternoon, I had received expressions of interest from 12 Casting factories in China and solid quotes from 6 of them, as opposed to the three months I spent trying to find any one to do the job here.

Standby for the next ridiculous episode.

Fangy, is this a pilot for a Netflicks series?

Stu - all I can think of is Benny Hill, but this whole thing is certainly ridiculous enough.
John - if this is a script for Netflix, it's rubbish, dont watch it.
Nebs - postal tracking, pfffft...as if anything could go wrong!

I have spent the past two weeks working through all the quotes from various operations in China. A lot of them had paid close to no attention whatsoever to the design brief, some where for CNC rather than sand cast, some were ridiculously cheap for 10000 units minimum ( I specified 20 of each size) and none of them gave me any confidence in their ability to do the job with the attention to the fine details like porosity on the foil suface. For example, one company proposed this be fixed by using oil paint at $USD4.50 per unit.
I eventually narrowed it down to one company that seemed to tick most of the boxes. The only problem was they wanted to print their own patterns and not use mine. Given how technically difficult this is to achieve, (just ask Nebs!), plus all the time I put into finishing the patterns to a 'perfect finish', I started to feel dubious about the end result. On top of this, I was still having a hard time about the breaking the promise I had made to myself that I would get it all done in Australia.
It got so bad, I decided to procrastinate by studying. The implications of this for the balance of the universe were obviously proundly serious, and so the Gods in charge of this sort of thing acted swiftly... Up pops Fred in my email inbox.
Fred has now finished his jury duty and is keen to start casting fins in his back shed for a reasonable price. Previously, he had spent his working life as a pattern maker and knows a thing or two about casting. Plus, his back shed is not far from Uni.
Needless to say the patterns are on their way on Monday, and Fred will get cracking. Be warned, when Fred gets cracking, its only 'a couple of fins a day' sort of pace, but I can live with that because I know every other box in my mental checklist will be ticked.
If only I had known all I had to do was some study and everything would work out :-)

Light at the end of the tunnel? Maybe it's not even a train coming the other way. Stay tuned, patiently of course...

And just to finish, a little snip of the fin testing in the serious snotbergs at Boombas. If you look closely at the footage, at the 40 second mark, the snot gets pretty thick and the fin lifts the Barge clear of the water altogether. It took me a bit by surprise and so I over-react a bit, but as you will see, its all over and settled down within a second. I am starting to feel confident that the fin will cope with Budgewoi weed too. The footage of Slugger was for me to study how the Fangyfin 24 was affecting the trim of his board as it is a far classier bit of kit than my Barge. (ie. Patrik 115l 70 wide) I am happy with the result

Sorry for the sloppy editing - but I have to get back to studying before the Gods of Fangyfin **ckups realise I am not on the job.

At last

You know when a TV series goes on too long and the plot just gets too ridiculous? I think I am getting close... (BSN101 I am blaming you this time )

The fins were originally cast using a sand investment casting process. Cheap, fast to do small numbers but not that great with complex shapes. Several attempts at making the fins solid were attempted using this technique. Unfortunately none of them were viable. The complex shapes in the box area in particular, proved too difficult to successfully mould in the sand.

The only way to achieve the level of accuracy required is to fabricate casting mould patterns. This will give better quality castings and allow for greater numbers to be poured. The downside is the cost of each mould pattern is expensive and takes time to be fabricated. I cannot afford to have all three mould patterns to be done. I have decided to get the 20 and 24 done now, and the 28 will have to wait until I can afford to do so. ( I have my yacht for sale atm, hopefully when it sells I will be able to use the funds to do the 28 :-)

I hope the cost of a fully finished fin will be still much the same as before, due to the increased per unit cost being offset by the decreased amount of time I have to spend finishing. For the same reason, the ex foundry only versions will be more expensive than previously expected. For those of you who have orders, I will contact you and confirm your interest and preference when the time comes. In the meantime can you please contact the executor of your will and specify who should take ownership of the fin when it finally arrives.

To finish with some good news. A big thank you to Slugger who tried a back to back test with a Delta (which has greater surface area) in thicker weed. Sailing behind him I noticed that the board trim, yaw, and pointing ability were demonstrably better with the FangyFin. I am pretty sure the difference was noticable to Slugger as well.

Stay tuned for the next episode.

sboardcrazy said..
I have my yacht for sale atm, hopefully when it sells I will be able to use the funds to do the 28 :-
you should have enough funds for lots of 28's...

...you haven't seen my yacht

nebbian said.. what's the difference between the patterns you currently have, vs what you need?

Hey Nebs, If the 3D print you did for me is the 'positive' pattern, the one I am getting done is the 'negative' spilt into two halves. So if you get the two halves of the negative, bolt them together and fill them up with aluminium, you get a perfect copy of the original 3D print. The two halves are made of a very durable material that can be used for the lifetime of the project.
Previously, it was much the same process, but the mould was made by imprinting the 3D print into two sand beds. Easy to do, but can only be used once.

Boring Nerdy Bit Alert!
I think I might have got some solid science behind why the fillet is so effective. I started looking at the end wall of turbines as it was the only thing I could think of that had a foil joining a 'flat' surface and where there was extensive research. Turbine efficiency increases of 1 % is big news, so all sorts of experiments have been done to increase lift and decrease drag. I still haven't done enough reading to pontificate with authority, but as far as I can tell, high efficiency turbine blades all have fillets. There seem to be two types. The first is the traditional fillet that I have used. The second is the 'Bulb' that is similar to Keef's design.




The two types of fillets have opposite effects on the horse-shoe vortex, but both decrease drag by either decreasing the passage vortex or decreasing secondary flows. The above picture shows fillets that are wrapped around the base of turbine blades, which are optimised asymmetric 'fins'. I have only researched the FangyFin style fillet so far, and I have a way to go to be totally confident that it is possible to extrapolate turbine data to windsurfing fins, but from what I have read so far, it seems a good explanation as to why the fillet seems to work so well, and for a left-brain thinker like me, an excellent back up to all the subjective experience we have had so far when using a filleted fin.