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FangyFin MkII Theory for insomniacs

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Created by fangman > 9 months ago, 20 Feb 2017
nebbian
WA, 6125 posts
13 Oct 2017 8:58AM
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Stretchy said..
Ross, taking the aluminium skin concept further, could you press 2 halves of the fin into a female mold from say 4mm ally plate, then weld the 2 halves together and fill with foam? Not sure how you would deal with the box end...


I have a friend who built a bike frame in a similar manner. He made male and female moulds for each section out of MDF (CNC milled) and squashed them together with a massive press. It worked fine.

Welding the two parts together would be tricky due to the warping factors. You also would struggle to get the fillet looking correct.

But it is possible, and I daresay would be easier on a fin than a complete bike frame.

fangman
WA, 772 posts
13 Oct 2017 11:58AM
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Fred has the patterns in their boxes, the core boxes already joined together and a new pouring funnel, all packed and off to the foundry for the 20 and 24 cm versions.




fangman
WA, 772 posts
17 Oct 2017 1:18PM
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More fillets than the butchers.
Apologies for some of the photos - I was trying to show up the surface differences, but couldn't get all the fins just right in the one shot.

Left to Right:
28cm ex foundry: 24 cm proto: 24 cm cut down to 20cm: 20cm test cast: 20cm cut down to 18cm.


The 28 (far left) has no finishing. The 24 (next one across) - it is interesting to note the effect of a few hundred kms of weed sailing. The leading edge appears to be 'self polishing' with an oxide layer only starting to build up behind the leading edge. It is still very smooth on its leading edge, however the weed here feels pretty 'snotty' at the moment and not particularly abrasive. Time will tell how the aluminium holds up, but at the moment the only noticeable change is the oxide layer.


The middle fin has not been used in the weed and has a even coat of oxide.



The two 20cm variants have had an initial polish but as you can see have some way to go.



I haven't posted any Deck pics for John for a week or two either - so these are for him too.

fangman
WA, 772 posts
18 Oct 2017 7:51PM
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With the real McCoy hollow fins due in November, I am selling these trial castings. Please note: they are NOT hollow - they are the solid trial casting versions.

www.seabreeze.com.au/Classifieds/Windsurfing-Accessories/~vg53t/2017-Fangyfin-24-And-28.aspx?_page=1&search=kUAz4ywlWw9x4uvKNrfOmw%3D%3D




fangman
WA, 772 posts
20 Oct 2017 5:38PM
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For the hardened insomniacs amongst you, this research paper was found by Yoyo. ( I just pinched the link from Decrepits' thread.)

www.sname.org/HigherLogic/System/DownloadDocumentFile.ashx?DocumentFileKey=6b7de6c7-1e9c-4fd1-b1db-7e62c333758f

It's a great paper on propeller fillets. Thank you Yoyo!

fangman
WA, 772 posts
21 Oct 2017 3:35PM
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Wanted: Crash test dummy with Tuttlebox board to take on the weed here using a hollow 20cm fin.
I tried to take some close ups of the fillet, but mostly just ended up showing that I have a lot more finishing to do. It looks sooo much better without my glasses on



















Stretchy
WA, 379 posts
21 Oct 2017 3:48PM
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Beautiful Ross . Great to see a result from your perseverance. Innovation is actively promoted where I work and I reckon this is a brilliant example of seeing something through from whoa to go.
what happens with the box end, will it be dipped in goop to give it a wee bit of give?

fangman
WA, 772 posts
21 Oct 2017 4:34PM
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Thanks Stretch - ( I thought the first reply was going to be John saying the grout needs cleaning )
If I understand you correctly, the box portion of the aluminium can be a relatively loose fit in the box. This is because in this design the fillet becomes the 'fitted' surface and is responsible for some of the lateral load bearing.
The fit of the underside of the fin to the board requires fine tuning for each fin/board. I have found that with slow and careful adjustment of the front of the fin, it will sit tight against the board and keep the weed out with no need for a flexible layer. To cope with a little negative rocker on different boards in your collection, the best solution I have found so far is a really thin layer of window silastic. ( finger dipped in detergent to make it smooth and thin). Lots of negative rocker might require 'Delta like' adhesive backed rubber strip approach, or a repair to the board to fill the hollow

morts
WA, 106 posts
21 Oct 2017 5:52PM
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They are looking bloody good Fangy, nice work!

John340
QLD, 1856 posts
21 Oct 2017 10:58PM
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fangman said..
Thanks Stretch - ( I thought the first reply was going to be John saying the grout needs cleaning )
If I understand you correctly, the box portion of the aluminium can be a relatively loose fit in the box. This is because in this design the fillet becomes the 'fitted' surface and is responsible for some of the lateral load bearing.
The fit of the underside of the fin to the board requires fine tuning for each fin/board. I have found that with slow and careful adjustment of the front of the fin, it will sit tight against the board and keep the weed out with no need for a flexible layer. To cope with a little negative rocker on different boards in your collection, the best solution I have found so far is a really thin layer of window silastic. ( finger dipped in detergent to make it smooth and thin). Lots of negative rocker might require 'Delta like' adhesive backed rubber strip approach, or a repair to the board to fill the hollow


The fin and grout look great

Jonski
WA, 40 posts
21 Oct 2017 9:21PM
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fangman said..
Wanted: Crash test dummy with Tuttlebox board to take on the weed here using a hollow 20cm fin.
I tried to take some close ups of the fillet, but mostly just ended up showing that I have a lot more finishing to do. It looks sooo much better without my glasses on




















Hmm "crash test" maybe this would be a job for me

fangman
WA, 772 posts
22 Oct 2017 12:24AM
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Jonski said..



Hmm "crash test" maybe this would be a job for me


Agreed. If they survive a session with you I will sell them to the Army as tank armour.

fangman
WA, 772 posts
25 Oct 2017 10:07AM
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I have sent emails out to all those who expressed an interest back at the dawn of time. If you didn't get it, please get in touch. The first production run is already sold out, but if you are interested in the second run, here is the price list.
Please note, due to me running out of money, the 28 will not be available until I have built up some reserves to pay for the bigger hollow box pattern. I have a number of solid 28's if you want to drill them out manually, but be warned this is a big job!



I will endeavour to get some demo's sent to the East Coast once my exams are done and dusted and I have a bit more time on my hands :-)





fangman
WA, 772 posts
27 Oct 2017 12:02PM
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Crash testing complete. Here is the result of the FangyFin vs plank of wood at 34 knots contest.




The fin suffered a very small dent to the leading edge, but otherwise unscathed. The plank was cleaved. So it looks like I will have to add "Need a logger splitter?" to the advert. :-)




The first consignment arrived today, and Fred is pouring more next week so I should have spares by late next week or early the week after. PM me if you are interested in high speed timber work :-)

keef
NSW, 1992 posts
27 Oct 2017 2:48PM
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you can see the shape of the foil fangy

fangman
WA, 772 posts
27 Oct 2017 1:06PM
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keef said..
you can see the shape of the foil fangy


haha :-) You might be able to Keef - I am still seeing stars!

decrepit
WA, 8704 posts
27 Oct 2017 3:41PM
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I'm just glad you hit it end grain! Side on could have been a lot more painful

choco
SA, 3339 posts
30 Oct 2017 4:12PM
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Have you tried using them unpolished left with the original out of the mold finish?

fangman
WA, 772 posts
30 Oct 2017 5:32PM
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choco said..
Have you tried using them unpolished left with the original out of the mold finish?


No choco not yet. But having spent the last few days grinding and polishing fins, I am liking the idea more and more by the minute! :-)

fangman
WA, 772 posts
31 Oct 2017 12:44PM
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Quick update: I just sold my boat , so I given Fred the go-ahead to make core box pattern for the 28 . It will take him a few days, so all going well, next weeks pour will be hollow versions of all three sizes.

WazzaYotty
QLD, 294 posts
31 Oct 2017 3:12PM
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fangman said..
Quick update: I just sold my boat ,


....drinks on at Fangy's.......

ka43
NSW, 2747 posts
31 Oct 2017 5:28PM
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Awesome job Fangy!!! That's some major undertaking (maybe "undertaking" is the wrong word after your plank splitting exercise) and work right there.
What rake are they and are you looking at doing anything smaller than 20??

fangman
WA, 772 posts
31 Oct 2017 5:38PM
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ka43 said..
Awesome job Fangy!!! That's some major undertaking (maybe "undertaking" is the wrong word after your plank splitting exercise) and work right there.
What rake are they and are you looking at doing anything smaller than 20??




Thankyou
The rake is variable. It starts at the board at approx 50degrees and sweeps aft as a shallow ellipse: The longer the fin, the more sweep. The 24cm averages just under 55 degrees over its length. The 20cm is slightly less and the 28 slightly more. The intent was to provide a smallish fin that could handle bigger sails, that is provide as much lift as efficiently as possible, and as a result not be overly concerned with drag or trying to produce a speed fin. The amount of lift the 20 provides is about as low as I can go and keep true to the intent. In my hands and barge-arse weight, it needs to doing planing speeds before it really starts to bite, whereas the 24 bites as soon as its starts moving.
The surface area of the 20 is about the same as a 55 degree rake Delta 16. I cut the 20 down to 18cm and it seemed to be well behaved. I guess you could cut it down to 16cm, but I haven't done any experiments to find out. But that's as small as I am going for now. Methinks any further development is not going to get approval from the Minister for Excessive Windsurfing Expenditure for quite some time yet....

( Wazzadrunkensailor - drinks are on mate if you can get yourself here )

AUS 808
WA, 221 posts
2 Nov 2017 10:09AM
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decrepit said..

Stretchy said.. Ross, taking the aluminium skin concept further, could you press 2 halves of the fin into a female mold from say 4mm ally plate, then weld the 2 halves together and fill with foam? Not sure how you would deal with the box end...



The person you need to talk to is Swindy, he's the expert welder amongst us.
I have suggested that idea to him, but my idea was stainless not ally.


Funny you should say that Mike.
When living in the Philippines with no windsurfing shops I decided to make a Stainless Steel fin as I was managing a St St fab shop.
1.2mm thick welded & polished, looked magic
Sailed approximately 10 metres before it folded at the base 90 degrees to the board

Carry on Fangy

fangman
WA, 772 posts
2 Nov 2017 12:17PM
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AUS 808 said..

decrepit said..


Stretchy said.. Ross, taking the aluminium skin concept further, could you press 2 halves of the fin into a female mold from say 4mm ally plate, then weld the 2 halves together and fill with foam? Not sure how you would deal with the box end...




The person you need to talk to is Swindy, he's the expert welder amongst us.
I have suggested that idea to him, but my idea was stainless not ally.



Funny you should say that Mike.
When living in the Philippines with no windsurfing shops I decided to make a Stainless Steel fin as I was managing a St St fab shop.
1.2mm thick welded & polished, looked magic
Sailed approximately 10 metres before it folded at the base 90 degrees to the board

Carry on Fangy


I say well done for trying!

"He who makes no mistakes, makes nothing at all"

decrepit
WA, 8704 posts
2 Nov 2017 1:44PM
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AUS 808 said..
Funny you should say that Mike.
When living in the Philippines with no windsurfing shops I decided to make a Stainless Steel fin as I was managing a St St fab shop.
1.2mm thick welded & polished, looked magic
Sailed approximately 10 metres before it folded at the base 90 degrees to the board

Carry on Fangy


Yep, needs to be filled with something to take the compression loads, at the base of the fin they are very high.
End grain palm works very well and is quite light, but if you formed the SS around it, avoiding flames as you welded the seam would be trick.
Blowing foam in under compression would be the easiest, if you could achieve the required density.

ka43
NSW, 2747 posts
2 Nov 2017 5:17PM
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Thanks Ross, will observe with interest!!.

fangman
WA, 772 posts
2 Nov 2017 6:26PM
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What to do with a solid 28cm? I got busy and drilled it out as much as I could internally and then chopped off the top to make it a 22cm. The idea is to push the limits of how much lift I can get out of a short fin (it's too weedy and shallow here to use the 28 cm except on a high tide. )
I can use the 24cm with my 8.5, but the 24 doesn't produce enough lift at the low speeds that occur when I am using the 8.5 and doing uphill work. I will try the cutdown version and hopefully get to compare with the 24 in the same session. Hopefully I will see whether the 28's chunky foil is still enough to counter the tip efficiency losses.

The photo has ( L->R) the 28 - 22 cut down, then Mort's partially prep'd 24cm, then an unfinished 20cm as comparisons.




morts
WA, 106 posts
3 Nov 2017 8:46AM
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mmmm shiny!

Looks really good Ross

fangman
WA, 772 posts
3 Nov 2017 11:48AM
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The core box for the 28cm fin is finished (LHS on photo) . As you can see its a sizeable hollow in the fin. I will be really interested to see the relative buoyancy of this fin once the hollow is sealed off.





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"FangyFin MkII Theory for insomniacs" started by fangman