I adjusted the layer height to 0.3mm (instead of 0.2mm) and the printing time is down to 14h17min (from 20h10min).
The surface is a bit rougher than the 0.2mm print, but that probably makes little practical difference when I have to hand-sand a bit anyway.
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Now printing the same fin but with BLEF and 0.3mm layers and external perimeter print speed reduced from 30mm/s to 20mm/s. Maybe that will smooth the surfaces.
Wow man you went hard core on this…
I’m blown away with your effort iterations, improvements and attention to detail. well done.
Some majorly advanced printing happening here.
My printer screws up about 20% of what I try to build, usually if it doesn’t wanna build it, I don’t argue and find some other way. You stuck through it and learned ton during the process. appreciate you sharing I’ll take some of your findings and give fin builds another go.
With your new skill sets I’m super curious about what comes out of your printer next?
massive-swells wrote:“With your new skill sets I’m super curious about what comes out of your printer next?”
Thanks, and regarding the next project: During the week, when I’m not home long enough to print a fin, there are quicker projects lined up.
The family has put in a few orders, for a milk carton holder for grandma (put in the milk carton, then use the handle so it does not get dropped, I need to design it first) and a chess set that one of the little ones has designed in OpenScad.
And then there is the eternal Reprap stuff: Must build stuff to make the printer better. Next up: Easily removed and easily replaced covers for manual access holes to the enclosure. So I can stick two hand in and do stuff like change filaments or whatever, without opening the lid, so that the print does not warp/contract/misbehave due to sudden temperature changes. Then I can print multi-color fins, and use up the growing number of spools that don’t have quite enough filament left on it for a fin.
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And then, the printer will be one of the many tools that I use for purposes that they were not intended for!
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I’m itching to get this fin making problem out of my system, because another and possibly much more important project is bouncing around my mind.
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It’s all one big learning curve. Without much of what I learned during this fin making adventure, much through the helpful ideas of others, I would not even perceive that a solution to the new problem might be possible.
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That new problem is infra-sound. It is dawning on me (thanks to Thrailkill’s comment somewhere on Swaylocks about humming fins, and Hans’ comment that stiffening the fin increases the resonance frequency), that low frequency vibrations are probably involved in much of the drag caused by surfboard fins. Active resonance prevention could be an option that may allow flexible fins to be used. But that’s just something that just came to mind while typing this, possibly useless or not worth the effort.
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The thing I want to develop next is an infra-sound cancelling device that uses something like a smart-phone and a home theatre system to cancel infra-sound in a small space, like a bedroom. Like active noise cancelling headphones, but aiming at frequencies between 7Hz and 30Hz or so. I imagine that an infrasound sensor reports to an Android phone via Bluetooth. The Infra-sound cancelling app then calculates the appropriate opposite sound signal, and sends it to a high-end home theatre system with a very capable sub-woofer, via Bluetooth or WiFi or whatever they will invent in the next week. In response to the measurements received from the infra-sound sensor, the app adjusts the phase and amplitude of the sub-woofer output, until it is quiet in the area of the sensor. A month ago I would have thought this is nonsense, but now I know better. Do a search for infra-sound and it will blow your mind how important it is.
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The infra sound problem that is motivating me at the moment is the noise created by wind turbines. I’m not sensitive to the infra-sound myself as far as I know, but many people say that they are, and that they suffer adverse health effects. I met a dear old friend recently, after years without contact, telling me about severe health problems experienced due to the friends exposure to wind-turbine infra sound. I googled it a bit, and the number of scientific articles about infra-sound, it’s measurement, prevention, cancellation, etc etc etc is staggering. They use it to detect nuclear bomb test somewhere else on the planet, and all sorts of stuff. Look it up, it will be an interesting ride, I promise. A few teasers: http://onlinelibrary.wiley.com/doi/10.1029/2012JC008257/pdf
https://link.springer.com/chapter/10.1007/978-1-4020-9508-5_7
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Infra-sound for surf forecasting, or adapto-floppo-fin-optimisation, and as a public health problem due to the proliferation of infra-sound from wind turbines. Their blades are of course designed along the principles used for the Wavegrinder fins, and some are proposing BLEF turbine wings to improve low-wind speed performance and other aspects of wind turbine performance.
https://www.youtube.com/watch?v=OpLzI27febM
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So I figure I’ll be dusting off the soldering iron (once I can print fins at a reasonable quality at will), and then start building this infra-sound detector: http://www.siliconchip.com.au/Issue/2013/March/Infrasound+Detector+For+Low+Frequency+Measurements
Maybe I’ll adapt it so it fits into a fin, to measure how and when it’s loosing energy to low frequency vibrations. With the fin printing technology now available, one could easily print a fin that fits a small removable measuring device, whatever it is. The smart fin sensors for example could be installed into a fin of your choice.
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As I’m getting close to my current goal of making a fin, I think my fin making days will soon be over. I hope the info gained has been shared well enough to help some others to produce fins in a less resource intensive manner, and to improve and share it further.
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I reckon that the reasons for me shying away from getting barrelled for the last 20+ years are:
- I’m a chicken
- It’s a bloody stupid place to put yourself in
- Once I’ve done it a few times, I might stop surfing.
- I want to Keep Surfin’
Some fin porn to round it of:
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I sanded these through the grades today, it took three hours with a couple of little interruptions.
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Sands so easily under water with a bit of sand paper under the finger tips. No dust. After sanding, I pour the water into a flower pot full of the plaster of Paris remnants that I created earlier on in the fin making process. Over a few days, the water comes out through the plaster, and all the plastic PLA particles stay on top of the plaster in the plant pot.
Beautiful fins. Have you thought of doing a slightly thinner hollow-ish fin skeleton that then gets a wrap of carbon vacced over the entire fin ?
factor in the thickness of an extra resin layer for base width adjustment ?
Surffoils wrote"Beautiful fins. Have you thought of doing a slightly thinner hollow-ish fin skeleton that then gets a wrap of carbon vacced over the entire fin ?
factor in the thickness of an extra resin layer for base width adjustment ?"
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Yes, and no. I have no experience with vacuum bagging, but from what I have seen, I will have to play with that one day.
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However, I think I have considered a problem that might also be present when vacuum bagging like you suggest. The problem is that a fin should be wider than the 9mm standard for fin boxes. The sudden increase in width where the fin joins the fin tab causes acute angles of 90deg and more. While I have not tested it experimentally, I assume that this produces a weak spot in the laminate. And the weak spot happens to be right where the maximum forces accumulate to snap the fin.
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One of the reasons why I decided to use 100% rectilinear infill is that this lets straight lines of deposited filament run from the bottom of the tab to the tip of the fin. The alternative would be to increase the number of perimeters. With enough perimeters, you also end up with a solid fin, but again those acute angles at the maximum stress point.
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See screenshots for illustration. I think vacuum-bagged cloth of any type would also be weaker if it were to be forced to zig-zags around the same angles.
I see, makes sense. Just thinking of ways to invent something new.
Here is the milk carton holder OpenScad code, it printed well and is sturdy and light when printed from PLA.
Excuse some totally irrelevant code comments, they were inadvertently left in when the code was copied from the fin making code.
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$fn=80;
difference(){//to cut off top and bottom flat
union(){//to difference top and bottom flat
minkowski(){ // Minkowski sum three times to round the base edges:
minkowski(){ // Minkowski sum three times to round the base edges:
minkowski(){ // Minkowski sum three times to round the base edges:
difference(){
cube([87.1,87.1,195]);
translate([0.05,0.05,0.05])
cube([87,87,195]);
}
rotate([0,0,0])
cylinder(r=0.25,h=1); }
rotate([0,90,0])
cylinder(r=0.25,h=1); }
rotate([90,0,0])
cylinder(r=0.25,h=1); }
translate([-6,-20,-1])
rotate([0,0,0])
minkowski(){ // Minkowski sum to round the handle edges:
minkowski(){ // Minkowski sum to round the handle edges:
translate([0,0,-1.5])
difference(){// the handle
translate([42,63.75,100])
rotate([90,0,0])
cylinder(r=100,h=1);
translate([42,75.5,100])
rotate([90,0,0])
cylinder(r=96,h=61);
translate([-190,3,-50])
cube([285,285,298]);
}
rotate([0,0,0])
cylinder(r=2,h=1);
rotate([0,90,0])
cylinder(r=15,h=1);
}
}
}//End union to difference top and bottom flat
translate([-10,-10,-2.50001])
cube([300,300,2]);
translate([-10,-10,196.500001])
cube([300,300,2]);
}// End difference to cut off top and bottom flat
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