I finally figured out a way to trim the fin tabs more quickly:
I did wetsand the epoxy surface, but the interlayer adhesion likely can’t be remedied by this alone, not without cloth atop.
There was a puddle under the fin this morning. The fin hangs down where i store the board, and continues to drip from its tip.
This filament might be a loser in the longevity department, buts ability to flex rotationally seems superior to the other PLA fins you sent.
The red gullwhale fin had to be removed from my LB board before surfing today. I put my palm up against the tip and pushed it as hard as I figure water pressure could on a hard frontside bottom turn, and the crack at the base opened up and out came several more drops of mother pacific, and one of the cracks on the tip lengthened audibly and my palm came away wet.
Not sure it can be trusted. To get the gap the widest requires rotationally flexing the fin. The gaps do not open up twisting it in the other direction, and not very much when pushing down on the fin tab, as if the tip was being pushed back from impact with sand.
I doubt the impact with cobblestone caused the crack at base of fin nor contributed to it. The time I ran it into the sand was session #2, and the cobble impact with no forward speed was session #4. I think it cracked when up and riding and twisting rotationally under load on session #4, and if so, I did not feel it happen.
The harftub7s13 felt fine in today’s conditions, but I wanted the gullwhale.
Epoxy is curing on it, as I type.
MUUUAAHAHAHAHA!
My evil plan is working, the fin self destructs after a couple of sessions!
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As I said earlier, looking back at the 3 month old design, it is poorly designed. I learned a lot since then and the fins on the way to you should be much better. And in addition, the type of filament is just not holding up to what the manufacturers promise. If I had printed the fin from PLA, it would hold up much better even with the design faults inside of it.
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I’m sorry the fin has such poor durability, but the shape persists in code and a new and much better one is on the way to you. Maybe you can turn that one into a sturdy fin by laminating it with carbon cloth and resin. But it may be better or worse with added thickness.
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I am rendering a GullWhale-7-S-11mm with double-screw-plate thingies. It will also help to reinforce the strength for roll pin use.
Things just got a whole lot better.
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I think I reached a breakthrough, but the latest (as usually already outdated) lot of fins for wrcsixeight shall get posted tomorrow regardless.
All three are Silpoxy type GullWhale fins, stiff in all directions and likely sturdy, but the proof is in the pudding. Not many have been surfed much yet, and surprises have been a dime a dozen on this journey.
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I designed some protectors for shipping and while being thrown around when rummaging around the boot / trunk / van. That does not get around the softening / melting problem, though. They are prototypes, each one a bit better than the last.
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The fins only differ in thickness: 10mm, 11mm, 12mm.
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The 12mm version is not quite finished, it needs some removal of extra parts around the base. It will help wrcsixeight understand where exactly to drill the holes for the screws.
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If you can, try the fins without further surface sanding or polishing, because I would like to know if any additional smoothing actually helps the performance. I understand that it is an issue with the kelp / seagrass areas, but polishing the fins is an enormous extra amount of manual labour, so I would like to know if it is really helping performance, or not. Maybe try to surf them first when not so much seaweed is around. Then you can polish them to your liking and compare if the ‘CLEAR WATER’ performance actually improves along with the seaweed release properties.
Now to the more ‘cutting edge’ stuff…
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I tried to print a GullWhale fin from carbon-laced filament the other day, the result was a disaster.
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Then I tried again, after tweaking, drawing on many parts of my recently gained knowledge, and almost all the extra mods and ancillary parts to the printer that got added over the past 18 months.
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The result was a failure due to layer shift after more than 80% of the print was done. I left it to complete the print, just to see what happens next.
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It turns out that fin is likely spectacular. Nearly as stiff as a fibreglass fin laterally, but flexing nicely rotationally.
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And, buoyed by the feel of the stiffness vs flex in hand, perfect apart from the layer shift, I knuckled down to find the reason for the layer shift. Something triggered my memory that I had seen this before, although it had happened early in several repeat prints, not near the end as this one. I had recorded video when it happened for the third of fourth time, and managed to dig it up. The first time I watched the video (when the problem first occurred weeks ago), I did not understand what I was seeing, but with the motivation of the (messed up) perfect fin in hand, I tried a bit harder, and managed to figure it out.
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The layer shift was not due to the print bed being bent by the warping print, but because for some reason Slic3r decided to tell the hot tend to move out of the printable area during some nonsensical non-print move. The stepper motor misses a few steps when the extruder cannot physically move to the programmed location, and then the printer believes that the nozzle is somewhere that it is not. So a very ‘clean’ layer shift, in an otherwise perfect print, will be the result.
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Now that I know how to search the .gcode files for the offending code, I do not waste filament and print time with a defective gcode file.
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Another side show in the drama was that the carbon filament had worn down the hobbed pulley quickly, or at least worsened it’s demise. I had not seen this failure mode before. I suppose I need to get a hardened hobbed pulley. I installed a hardened nozzle a long time ago, just in case…
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And to top it all off, the PINDA probe cable is failing again, this time at the RAMBo end. I have been nursing it along, and managed to print replacement RAMBo covers for when it finally fails. I modified the cover so that I can install a proper cable gland with strain relief when I have to.
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I manage to coax the printer through the bed calibration phase despite of the failing PINDA cable, and am hoping for a result tomorrow…
I Am giddy with gullwhale goodness.
Feels so good to have more than one, with more on the way.
The harftub7s13 has been in my board for many extremely fun sessions while waiting for the GW fin to stop weeping that which it absorbed surfing and wetsanding. The harftub7s13 fin is a machine, a confidence inspiring machine, and I was having strangers in the water, on the beach, and in the parking lot complementing my rides yesterday, and today I had perhaps even more fun on it.
But the red GW fin is reinforced with some carbon and some 1.43ox cloth because of that pesky interlayer adhesion issue, and is basically ready to get wet again. It is a bit stiffer rotationally than before, and I will be getting the latest Gullwhale 7 s 11mm arrival to fit Soon, when the wind is up, midday, unless it is glassy again all day, like today.
Mr Mik,
Nice to see such progress with your 3D printing and I have a quick question about your ‘carbon laced’ filament and apologies if you already are aware but is it a carbon laced nylon per chance? Again, as you probably know the nylons are very hydroscopic and will fail printing if not adequately dried before printing. I have heard of a trip to the oven for 6 - 8 hours at around 100C or better yet, and something I use is the PrintDry filament dryer http://www.printdry.com/product/filament-dryer . It has improved print quality for every filament type I’ve used and is a must if you are using a carbon reinforced nylon. The C-reinforced nylon I’ve used has created the strongest parts I’ve printed https://www.matterhackers.com/store/3d-printer-filament/nylonx-carbon-fiber-nylon-filament-1.75mm expensive but for the prototypes I’ve been experimenting with ( also fin related BTW) it creates some amazingly strong prints.
Again nice work on all things re: your fin design and best of luck.
As an aside I use Simplify 3D but cannot comment on it versus Slic3r as a slicer.
After reading your post again and a bit more thoroughly I see you have the filament printing very nicely other than that nasty layer shift. Confident you will figure that out and am looking forward to your next post and print results.
Yes, polyamide (Nylon) with carbon fibres. esun ePA-CF.
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It’s amazing how much difference the water content makes.
I printed an attachment for a food dehydrator and dried the filament at 80C for 8-10hrs overnight. Also dried 20 desiccant bags the day before, and the filament is in a closed box during printing, with the dried desiccant, being fed to the extruder through a PTFE tube.
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The layer shift is sorted. To find the faulty .gcode files: Search for “x252” in this case.
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When the filament was new, I don’t think I dried it, because it was in a sealed bag with desiccant. I printed “2 towers” (my test for finding optimum temperature and to strength test) and found the towers were no stronger than PLA towers. But yesterday, I printed 2-Towers and I cannot easily snap them by hand! Maybe I can snap them, but I would have to wear gloves in case they break with sharp corners. They are so much stronger than the previous print from the same material.
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If I continue to use this type of filament, then I will buy a dedicated dryer / feeder box of some sort. Otherwise the results will be too unreliable, with the possibility of sudden catastrophic failure while surfing.
I think I will use a new filament testing method from now: 2-Crossbars.
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That will allow rotational flex testing as well as nozzletemp tuning and snapping off.
Yeah I hear you on the strength of the carbon nylon filament - glad you got good results. I tried a .6mm (hardened of course) nozzle on a couple prints to add strength but never got it to work for crap… Can’t remember the temps I’m using but I thinks it’ 245C and a 70C bed temp - no enclosure - no fan. I did get some super strong prints but have switched to Poly Carbonate PC Max with really strong results as well but much more temperamental with a chamber needed to successfully print. Still have the NylocC in the back of my mind though and will print again with same after I return from a surf trip to Nicaragua.
The three Silpoxy-GullWhale fins are on the way now.
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The second attempt to print a GullWhale fin using ePA-CF (PA = polyamide = Nylon, carbon fibres) was a great success, but the whole PA fin printing idea might be a rip-roaring failure.
The obvious problem that I failed to recognise until now is that PA remains PA after printing. It does not magically change it’s properties just because it has been melted and cooled in a new shape once more.
So it remains hygroscopic, and slowly but surely absorbs water out of the atmosphere until it reaches it’s preferred water content. And then it is too floppy again!
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The incredible lateral stiffness of the fin print with layer shift shown above has disappeared 2 days after it was printed, and the rotational flex has become more marked.
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Maybe carbon rod insertion and / or resin infusion will result in a good flex pattern, but I just don’t know at this stage. My hopes for a fin that needs little post-processing after 3D-printing have thus been thwarted again.
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Never mind, I can now print a replica of the red self-destructing GullWhale fin from December 2017, using PA-CF, and it will hopefully be much more durable than the red fin, but similar in properties. But it might be temperamental when very dry weather changes it’s properties between surf session, or even when kept in a hot and dry car in the sun. But at least it will not melt or deform like the PLA/epoxy fins.
Worst case scenario could be a fin that changes properties during a surf session, as it absorbs water.
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I hope we soon find out if the GullWhale fin performs similarly well when it does not have pronounced rotational flex. If it does not, then maybe I’ll have to go back to the HARFTUB-7-S fin and re-make them with rotational flex.
The self destructing reddish gullwhale did have a little help in that destruction, but My reinforcements lasted through a very fun surf session yesterday and I did hit bottom twice, but not with too much force.
After fitting the rebuilt red GW fin into the board, i noticed The rotational flex was reduced a good amount with the carbon roving and 1.43ox cloth on each side. I put the fin about 5/8" farther back in the box than previous surfs on it, and it still feels wonderful, but I would have moved it forward 3/8 inches after the third wave had I a screwdriver handy. Was so used to harftub7s13 that I cannot say for sure that the reinforced GW fin makes the board feel slightly stiffer and less forgiving. I had an absolute blast. The fin is a rocket in my LB. I kept getting stuck on my backfoot when cross stepping forward as accelleration was more than expected.
A few hours after surfing yesterday, i was running an errand, and getting out of my vehicle it felt like i was stabbed in the side with a large wide knife. Did not surf today because of it and tomorrow is supposed to be an onshore windfest.
I did get the harftub 7s 14mm and 7s 12mm to fit nice and tightly, using two screws and plates fore and aft. Not having to slide the roll pin in the channel allows for a much easier fitting, with less wear and tear on the box and channel for a tigher fit in the box with less wobble from the base. My fin box in the center is so worn from repeated test fitting that to get the perfect fit requires I thicken that portion of the fin. I have not achieved the perfect fit yet, but the dual tab screw/plate will make that process easier. I think I am done with rollpins on any fin that has enough room to put a screw and plate in both front and rear, in my board anyway.
The yellow gullwhale is installed and ready to go. These fins have added a bunch of excitement back to longboarding, as I can build speed easier and quicker and turn harder with way more confidence. Late drops paddling at a steep angle near parallel towards shore, is stunning, that the fin holds and projects as it does. My raked fin would either go over with the lip or just stall lose all grip suddenly and without warning, either or, would likely send me swimming.
Another snapped off fin!
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A nasty and unexpected setback (are there any others, ever?), because I thought that the ‘Silpoxy’ version of the fins would be the strongest version.
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At this stage I don’t know if the silk is too weak, or if the random arrangement of fibres is to blame, or both.
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On the up-side, it seems as though the GullWhale-7 shape works well even without significant rotational flex.
I love the gullwhale fin. I’ve had so much fun with it/them in my 9’7" it is a bit ridiculous. Thank you again.
Regarding the strength of the Silk epoxy fin guts, this Wikipedia article, whose data is always a bit suspect, puts the tensile strength of silk well below that of E glass S glass or Carbon fiber.
S glass is 4710 MPa
Kevlar is 3757 MPa
E glass is 3450 MPa
Carbon fiber is 4137 MPa
Spider Silk is 1000 MPa
Basalt fiber is 4840 MPa
Source:
But a citation later says how variable spider silk is in this regard:
Apologies if I have interpreted it wrong and if tensile strength is not really what is required for this application.
If Wikipedia is to be believed and is accurate, and the spider silk you are using is 1000 MPa vs 3000+MPa of other fibers, then the remedy to fin breaking could be as simple as acquiring CF or FG roving.
I have filled the bases of 7 harftubs with mixtures of chopped random orientation CF and FG roving saturated with epoxy. One of these fins, The harftub 65s13mm, has been surfed the most, as it works so well and is reliable, and it has endured many of the same maneuvers which snapped off the Silpoxy gullwhale yesterday, which is basically a hard backside bottom turn intending to kick out up and and over a line of whitewater in order to get the board up and over as I do not wear a leash. Soon as the fin was sideways into the whitewater…SNAP.
I would not give up on the Silpoxy method, but change the fibers used, and attempt to get their alignment more north and south instead of haphazard from the base into the fin.
But add carbon tubes for the win 
or graphene at 130,000Mpa.
I love the gullwhale. The harftub65s13 is awesome too, but The GW is quicker, looser, more fluid, and happy anywhere one stuffs it into the wave.
Can anyone tell me how to make a DXF or DWG file and how that makes any sense?
I’m investigating water jet cutting (from G10) as an option to make the UTFB, but the cutters want these file formats.
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From what little I can understand from the instructions, I need to turn the file into a 2D object first, before exporting a DXF file from OpenScad?
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How could a 2D file represent a complex 3D object like this fin?
A DXF or DWG data file is 2D only. It will only allow a water jet cutter to cut the outline of your fin (side view) out of a sheet of material of your choosing. You would then need to foil the fin by hand.
If you want to create the full form of the fin out of G10 you would need to have it CNC machined one side at a time using a 3D data file (IGES, STEP or STL).
Thanks, that’s what I figured from diagonally googeling the subject.
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Would it be possible to cut a fin shape using 3D water cutting? Or is the technology just not there yet for complex3D objects?
Sorry MrMik, water jet cutting was never intended to be a 3D cutting technology, and by its very nature won’t ever be.
If you wanted to make fibreglass fins of your design you could make a mould using your 3D printed fin and make as many fibreglass copies as you wanted.
Here is a thread from a few years ago where Surffoils explains his methodology, and there are a couple of other threads on that subject as well if you search.
https://www.swaylocks.com/forums/moulding-fcs-fins