cleaned the bead blasted FF28 with hot soapy water, then brake cleaner, the hot soapy water, then brake cleaner. Dumped it in the anodise tank. This time tried Waricle's idea of using welder to supply the DC. On startup the voltage was about 2v @ 30 amp and the voltage slowly climbed and the amps dropped over the next 15 min to about 6v and 22amps. (the knob didn't seemed to do anything but that probably means I haven't read the manual)

After 15mins welder switched off so I switched to the batteries as was the plan...I originally thought welder had overheated. Oddly, I only got 7amps now on batteries when previously I got 65amps. Slowly, after draining both batteries current got back to about 50amps (at 10+volts at the electrodes) and all the jumper cables started melting again. Turns out the welder shut off because of one of those protection thingo's in a 4 way I'd plugged into. Plugged the welder directly into a 15amp supply so any shut off would be welder, not supply.

The new coolant system was working well and keeping temps steady but I then ran out of ice and temp started climbing. Batteries died so switched back to the welder just as temps hit 39degC. The welder could supply about 6V at 22Amps, chiller looked liked it could maintain/decrease temp at this load and welder seemed happy so left it run a few hrs. Had to change the coolant water every 30mins to fresh tap water (25DegC) to maintain control of the temps. There is 2.3m of 10mm, 1mm WT Al tube in the tank and ran the 12V pump sub optimally by mistake at 10.3v...so increasing and flow and more ice on hand should allow much better handle on temp control at high power in future.

Pulled the fin after 4hrs, rubbed all the black goo off and chucked it in the dye tank. Dye uptake is nowhere near as expected for a commercial dye so will leave over night and if still nothing tomorrow water will throw in turmeric bath as know this works.

Regardless of outcome next step will be to try and anodise standard Al to get ready for cnc'd version.

Flex I don't think you need a compressible material, I use a relatively hard plastic with my FF and it works well. It's mainly to protect the board

Stroppo put us onto a workable solution.

Tube of marine Sikaflex PU.

All you do is apply a release agent to your board around the fin box slightly larger than where the fin will contact.

Put some of the sikaflex on the bottom of your fin where it will contact the board.

Pull the fin down to "almost" the full setting (ie leave about 1.5-3mm) let it cure.

Remove fin (to make sure it has released from board)
Replace fin, Tighten it down, the Sikaflex should bulge out a bit, trim accordingly You may wiish to have some plastic tape applied tp your board first as a cutting surface.

Job done, if it eventually dies just repeat.

If the fin is used on multiple boards with different rocker lines around fin area and this creates an issue, just do it in the front and rear portions of the fin or just set it to the one with the bendiest rocker.

Word of warning unless you are going to use a lot of this then only get the squeeze tube as the stuff has a shortish shelf life once opened.

Just thought I had better post a photo of what I am babbling on about finish wise. This is a slow and low 'clear' anodised fin. The fin surface was finished to #120 grit prior to anodising. Post anodising, lots of the scratches have filled in.Yay! I gave it a rub with #400, but it's bloody hard so I am not sure I made much diff in overall smoothness. The dark grey is contamination of the anodised layer with the silicon. (used in casting alloys to help them flow). The spots, I think, are spots of higher magnesium and perhaps silicone as well. To touch it feels very smooth, defo much more so than it appears. The spotted gun metal finish is starting to really grow on me now and I am keen to see how they fare in the wild.

could waffle on about stuff discovered today but end result was Dylon Ocean Blue dye just doesn't work in the slightest despite overnight soaking. Turmeric and RIT Fuchsia (even after dye left for 6+ months) work well. Turmeric suffers that you need to keep agitating it. Current aim is to master standard anodising to prepare to the CNC fin as seems little point to attempt a cast Ano unless can do normal ano first.

Did some coupons today out of 10mm dia Al offcuts from the chiller, they took way more amps at full 12+Volts than I was expecting...10+ amps. Their surface area is almost exactly 10 times smaller than a FF18V4. 12V is supposedly the min recommended anodise voltage so need to try two batteries in series as the current load at high amps with a fin makes a large voltage drop across jumper cables and drops the supplied voltage at electrodes to around 10V best case if using just one 12V bat. My welder can not deliver a high enough voltage but Fangman's fancy adjustable power supply that can keep a higher voltage but fiddle with amps to control heating is the better approach. Since I can't control current with a couple of batteries I will try the fast and furious approach.

initially soaked coupons in the Dylon blue dye but similar to the FF28 zero uptake after 30 mins so dropped them in the RIT dye (that had sat around for 6+ months). After 30 mins in dye they looked perfect and little difference between sanded and raw..(top two cm where the holes/wires are was unsanded) After 4+ hrs the colour was deeper but had some discolouration in tiny section on both coupons..so dye time optional between these two. One coupon had NaOH treatment (one with extra drill hole), the other had nothing and little difference between them. I purposely tilted the coupons in the ano tank to see if any variation due to current effects. Next attempt will be to try normal Al with same surface area as a FF18V4 = 98999mm^2 to try and get uniform anodised surface. If can't do that then will farm out ano for the CNC fin.

For the surface area of a FF18V4 this should make the current draw at 24-26V around 117amps and the supplied voltage at electrodes around 4.3V less. This continuous current is going to melt standard jumper cables so will need to double them as bare min. 117 amps at 22V is 2.5KW heating which is going to boil 11 litres of acid from zero deg C in less than 30 min. Can't go above around 40degC acid temp to so will get 10 min plus what ever chiller is capable of. The chiller roughly seems to extract about 140W using 10degC temp difference so best case might get 300W chilling using near zero degC water giving 2.2KW overall heating. This gains a whole 2 min. extra or 12min total. It seems pointless other than the fact I need it to initially chill the acid. If I start at 25degC acid temp I will get tops 4.5min before acid overheats. Batteries at this load should deplete within 10 min assuming something else doesn't melt. Supposedly there is the law of 900 where time to anodise = 900/amps * square feet to be anodised *1.2. For the FF8V4 this is 9.2 mins which is right at the limit for batteries and chiller. The FF28 should have higher currents and problems so seems like will have to do it in two stages..the way this is all going it seems the CNC and farm out anodise is going to be the preferred solution and all this is just light entertainment.

Photos
#1 is anodised coupons after 30 mins in RIT Fuchsia dye (and 30+ mins in Dylon Blue no effect). Right coupon has NaOh bath
#2 is around 4 hrs, left has the NaOH bath
#3 Dylon dyes..they 'look' great but no effect
#4 RIT Fuchsia after long time sitting around
#5 FF28 after a few hrs in turmeric, too patchy so resanded
#6 FF28 after heavy 400 grit sanding..still plenty of turmeric

Love the fuschia colour!

Wow I blinked & lots of stuff happening does this mean there will be an option to order colour coded fins to match our gear, or will it be different sizes like the coat hangers when buying shirts so easy to work out what size in a hurry when rigging?

Or will I just be able to tell how deep the razor scratches are by the colour of the surface

YP1 said..
Or will I just be able to tell how deep the razor scratches are by the colour of the surface

It will be interesting to see how tough the anodised surface is in real world use. It's certainly requires more elbow grease when sanding than the raw surface. I have been chucking a few fins in the backyard pool to see if any of the usual AlO develops. So far nothing, but my pool isn't that salty. If I get inspired I will grab some salt and make a bucket and try it with that...of course by the time I do that, Flex will have made a self cleaning ultrasonic nuclear powered swimming pool complete with its own viewing submersible and be working on how launch it, and then crash it into the moon to test the surface hardness.

Flex2 said:

"... The growing process seems relatively straightforward, put salt or baking soda on aluminium and cook at 500degC.... Certainly will chuck some salted Al in the Pizza oven soon......."

By careful you don't end up with a fin that looks like a pizza, the casting alloy is one of the highest silicon and magnesium content alloys and so your temperature margin could be very small. From the Aluminium Guide -"Adding other elements to aluminum, including alloying, lowers its melting temperature, more precisely - starts its melting. So, some casting aluminium alloys with a high content of silicon and magnesium melting start temperature is reduced to almost 500 C."

fangman said..

Flex2 said:

"... The growing process seems relatively straightforward, put salt or baking soda on aluminium and cook at 500degC.... Certainly will chuck some salted Al in the Pizza oven soon......."

By careful you don't end up with a fin that looks like a pizza, the casting alloy is one of the highest silicon and magnesium content alloys and so your temperature margin could be very small. From the Aluminium Guide -"Adding other elements to aluminum, including alloying, lowers its melting temperature, more precisely - starts its melting. So, some casting aluminium alloys with a high content of silicon and magnesium melting start temperature is reduced to almost 500 C."

Just testing with coupons, don't think will actually cook a cast Fangy...just chucked this delicious snack in the oven before the proper tribal dinner...supposed to take 15-30 mins cooking. from left to right detergent, salt, baking soda (not baking powder). Supposedly the baking soda gives best results. Was a bit keen and don't think Pizza oven was quite hot enough as running around 400degC. The detergent bit slid straight off though, think need to shave some dishwasher tabs up..will have another try after dinner..anyone for after dinner mints?

Bit of an update.....weird/very unexpected results...

I upgraded my cheap arse jumper cables to proper 200+Amp wires, shortened them to min length and wired my two batteries in series to give 24V. Cut some Aluminium I had lying around to the exact surface area of the FF18V4 which I have both in cast and soon hopefully to be CNC format. Bought a few bags of ice and started chilling as much water as I could to pre chill acid...was about to hook it up when a pile of life stuff happened all at once which required attention/sorting out as priority. (not sure why but everything always seems to go wrong at the same time despite being completely unrelated)

Ultimately this gave me some time to think through what I was about to do and I started getting cold feet. The first issue was the sheet was roughly 1/3 the tank size and to cut down on Al wire used I'd put it near the top of tank. (see photo) Trouble is, having the sheet at the top will mean heating the acid at the top 3 times quicker than previous calculation so will get just over 1 minute before my 0 degC acid becomes about 40degC. I could run longer Al wires so the sheet is at bottom but this then introduces the issue that the whole sheet can move by convention currents (sheet is only 0.5mm thick) and short circuit to lead sheet.

The next issue is running my batteries in near short circuit condition at 120amps continuous may not do them any good. That is the least of the worries though...this is essentially a 1.2KW+ hydrogen + O2 generator and to start the anodising I have to connect jumper cables that will deliver a 120amp+ spark. The first spark should not ignite the H2 O2 since the spark comes before gas but it will no doubt weld the clamps to the aluminium. The issue is the disconnection. If I need to disconnect then best case there will be massive sparks and will ignite the H2 O2, worse case the clamps are welded and trying to free them will almost certainly result in shorting the battery connections and more sparks. Hmmm, what could possibly go wrong?

All this is probably fine if I could somehow do it remotely. I do have some 1000V, 1000amp contactors lying around which is fine for the initial start but they will definitely weld in the closed (on) position if trying to disconnect under 120amps DC so they are essentially useless. (switching DC under load is hard) That means I have to do it manually in a H2 O2 atmosphere right next to (hot to maybe boiling) sulphuric acid with connections that are probably welded.

So I started thinking Fangman's slow and steady approach is probably wiser and started looking into power supplies...There is some nice DIY kits capable of 50V at 8amps but the cost of parts was approaching $200, will takes weeks to arrive and then still have to build etc....thinking ahead I need 2 of these for hard anodise system.. not really worth the investment.

Luckily one of the 'life' issues I needed to attend was my hot water system failed and that meant I had to move some cheap arse Ebay solar panels I had bought 15 years ago so the plumber could gain access. It suddenly dawned on me this was (maybe) a far better solution for an adjustable DC power supply. Need more voltage, just stack panels in series, more current, stack them in parallel, adjust power on/off with a blanket etc covering panel.

Open circuit voltage of 1 panel was 20V and I think when I purchased they claimed 100W, which means about 80W in Perth sun. Hooked it up on ano tank with the dummy FF28 sheet and got 8V at 5 amps so about 1/2 the claimed power. Need more than 12V ideally for ano so tow should do the trick. I hooked 2 panels in series and got about 15.5V at 6.5amps delivered. Seemed nice..there was a satisfying buzzing anodise sound and nice bubbles.

After 10 mins came to check and all was well but in the space of a few seconds doing nothing the voltage climbed to 33V, current dropped to 3.7amp and the noise stopped. Within 30 secs the voltage dropped back to 17V or so and current back to 6amps or so and the noise resumed. What the?

For the next 20 mins or so looked steady state and from the rule of 900 at 6.5-7 amps figured standard ano time was in the order of 2-3 hrs. (i.e. 900/7amps * square foot area to be anodised X 1.2 = time in minutes) 1.2 is min current density. A FF18V4 = 1.06 square ft surface area. Had offsite task to do so did that and was away for no more than 80 min. There were zero clouds in the sky and I'd chucked the panels on the roof so no interruption.

Came back and found all the Al wire eaten away and the system running open circuit. weird, I'd run system at 50+amps 10V with just 2 or 3 Al wires and never eaten. Here was 6 amps at just 5-7 volts higher and 9 Al wires were eroded away. I chucked the sample in the dye but as expected no uptake after 4hrs, meaning no anodise layer. The dye for sure is great way of confirming a successful anodising.

Need to try again and witness what is happening and see where it went pear shaped.

Despite cleaning this 6061 sheet with caustic soda for nearly 30 mins, with 2 caustic bath changes and 3 hot soapy scrubs there was still an amazing amount of 'black goo' coming out in the acid tank.

Photo#1 the sheet of Al wired to accept lots of amps and cleaned in NaOH bath for crazy amount of time
Photo#2 solar panel setup (put panels on roof to avoid shadows etc)
Photo#3 acid tank with all Al wire eaten
Photo#4 in water bath showing Al wires all eaten
Photo#5 still a pile of black goo after anodising a very very thoroughly cleaned piece of 6061 sheet (shot is bottom of acid tank after drain acid)


PS re: the Carbon nano tube experiment in pizza oven, I downloaded the actual paper and turns out I did three things wrong. First, need to clean the surface of the Al...they seem to use Methanol and NaOH, Second, the coating of NaCl or Baking soda needs to be extremely thin and water based (not chuck it on like I did), just need a few Na atoms as catalyst, third, to grow the nano tubes they need an environment of CO2 + C2H2...the pizza oven is probably Co2 rich but need to add C2H2 (acetylene) which is of course highly flammable...easy enough to make/buy but need to make a little oven to put in the oven to control the environment...Seems a second best approach is to coat the Al in carbon nano tubes....easy enough to buy but many companies making this stuff seem to offer small (10g) samples for free so have requested a 'free' sample...lets see

Another day, and more interesting stranger stuff from 2022's toy of the year (even though only emulating such a thing, not actually playing with it).

Flipped the FF18V4 sized sample 90deg (because was tight fit in tank), NaOH bath forever and whilst doing that chill'd the acid. Probably a mistake putting another variable in the mix but was interested in how cold I could get acid. Only had the infrared thermometer which is misleading as it only reads surface temps and with vapour can get all sorts of weird results...i.e. chilled water was 1degC, upon circulating through 25degC acid, chill water went to -4.5degC, Acid went from 25 degC to 10 degC in a few minutes..just not possible so the infrared thermo is not a good indicator...need to put a stainless thermometer inside the acid to get reliable reading. Take away: the acid however was definitely cooler on starting..just not real sure on how much cooler.

Hooked 2 solar panels in series like yesterday (open circuit 37+V) but got less than 8V at 6amps in the ano tank on super cleaned FF18V4 sized sample. eh? (yesterday got 15+V). Day was exactly the same as last with no clouds...didn't measure the incident radiation yesterday but today it was 577W/m^2 at start and around 600 at end. Pretty sure near identical conditions though. Same acid, same panels, same everything except a few deg cooler acid

The measured voltage was on solar panel side which eliminated dodgy connections to the anode/cathode. You would expect a dodgy connection to show as high voltage on input and no/less current. The actual measurement was good current and low voltage. Since good/same/max current of solar panels at 7amps this implies good electrical connection. Briefly checked open circuit voltage and was 37V. I'd also woven the Al wire through sample so 'should' have been much better conductivity. Wriggled/played with the connections to anode and cathode but voltage stayed 8V and dropped over the next hr to around 7V.. 6.5-7 amps throughout

Wriggled the sample slightly at 1hr 20 min and bammm..voltage now 18V and way more ano action, sound/bubbles etc. Amps throughout remained as before at around 7amps. The sound gives the impression that its eating stuff...Please correct me if I'm wrong but a better electrical connection from panels to cathode/anode should yield a higher current and lower voltage...not steady current and higher voltage. 20 mins later doing nothing then whole system did the same jump as yesterday to 33V for 30 secs No noise/low current and back to 18V. 20 Min later from this event noticed all but one of 4 Al wires had been eaten so stopped and pulled sample, rinsed and chucked in dye. Had reasonable dye uptake meaning ok ano but nothing special

Washed dye off the FF18V4 impersonator in 1 second in ultra low concentration NaOh bath...However, the remaining Al wire that had not been eaten had superb dye pen even after this caustic bath. Since this was remaining wire holding this implies need the amp density to give good anodisation.

Conclusions from todays efforts:-
0. Need to achieve conditions of whatever the remaining drive wire had. This is way higher than 6amps for a Fangy sized Al
1. Completely illogical voltages as you would expect dodgy connections to give higher voltages measured, not lower.
2. High(er) current density gives/seems to give best ano result
3. Highly suspect lead is 'another cause' of black goo. It settles quickly at bottom of tank
4. Possible: Once above 10-12V most of the Al wires dissolve, have never dissolved at low voltage (<10.5v) and high currents.


Based on that:
A.Will switch to Al cathodes and see if any goo comes from Anodising Al with 6061 Al as anode and cathode
B. Will run 2 (or more) panels in parallel for more current less voltage
C. Will keep acid at around room temp (25 degC )

Photo #1 3 of 4 drive wires eroded. Main wire closest to source power not effected (zero erosion)
Photo #2 Dye uptake in sample but was far less than optimal anodise conditions..did not seal anodised layer
Photo #3 Washed in dilute caustic bath for less than 1 sec....near perfect dye remains in remaining drive wire
Photo #4 The 'black goo' is very heavy and very lead like....so it is lead?

So another thought. If it is a true current source, the varying the resistance won't affect the current much but will affect the voltage. So here's an experiment, chuck a variable resistance in series, and see what happens. I predict the voltage will vary more than the current.
If that's not the case, then has it something to do with those disappearing wires?

Strange the one closest to the supply line is hardly affected?

Another question Flex, how do clamp meters work with DC?
You need AC for induction to occur?
This must be a new thing, in my day I never came across a DC clamp, I guess it must be sensing the magnetic field?

decrepit said..
Another question Flex, how do clamp meters work with DC?
You need AC for induction to occur?
This must be a new thing, in my day I never came across a DC clamp, I guess it must be sensing the magnetic field?

hmmmm. DC clamp meters been around since before I was born...1965 to be precise. Gotta be one of the next best tools in the shed after a standard multimeter that can do volts/ohms etc. My unit I've had for nearly 20 years (got from Jaycar) but super handy for huge amount of stuff. Below 0.1 amps I would say it was useless but for higher currents its great (car alternators/batteries, solar stuff, anodising etc). Oddly, DC clamp meters are harder to source nowadays versus the AC versions.