I've been printing parts and using them to make moulds for about 2 years, must have done about 10 different wings. still a lot of work, but good results
Basic methods description is here:
http://kitefoil.forumactif.org/t2070-wi ... nt-plastic
Another thought about your vac bag of carbon over the wing shape.mcfly777 wrote:
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Thanks. This is an interesting idea. I can just have the CAD include a slit so I don't have to manually cut it.Blackrat wrote:once the wing has been sanded and it ready to be wrapped , cut a slit using a jigsaw etc from about 60-70mm from each end along the maximum thickness of the chord. using biax carbon or 0-90 weave placed on the bias (which is a pain to work with) pull a piece about 50mm wide thru the slit so that each side is equal and fold on the core . an there is your shearweb , id recommend 3-4 layers of 200gsm minimum
take pics of progress
Thanks Plummet. I am printing a scaled down version (97%) so that I can account for the extra thickness that the carbon will have. Not sure it's enough, but trial and error.plummet wrote:Another thought about your vac bag of carbon over the wing shape.mcfly777 wrote:
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Its hard for the bag to push the carbon through sharp radius bends. You may get bridging of the carbon around your fuse joint which is quite sharp and pointy. You may need to merge that point for a smoother larger radius. You will need to make the radius for the fuse bigger than the actual fuse radius and anticipate the how much thickness the carbon will be and choose a bigger radius on your 3d printed part so when carboned the radius is correct.
The same is true for the counter sunk holes as well.
You could even consider getting a tube or bar the correct radius of the fuse, waxing and using that when you vag bag to help the carbon form to the correct shape.
You're right. I should scale it down more. Final thickness right now is 13.8mmplummet wrote:Whats the thickness of your wing? 10mm to 12mm? Carbon thickness will be about 1mm for a couple of layers top and bottom. maybe slightly more. So your carbon layer will represent 10% thickness not 3%.
Note the radius around the fuse will have to be scaled up. maybe 110%?
Yes this is what i'm doing now. But I'm printing the sections on their leading edges so that the layers are oriented in such a way that they are not stressed by the weight.skyte wrote:Great project!
Have you considered printing the wing sections on their ends? That way, you might have to print more sections depending on how high your printer can print (most cheap ones do about 100mm height?) but you will get a better surface accuracy for your foil sections. You will also avoid that nasty rough surface on the bottom due to the support material.
Indeed I've been thinking about a CNC. If my current method works, it's fine. I don't want to build a tool just for one use.I'm in the process of designing a foil too... I built a CNC router recently so I intend to shape the core from bamboo and then just glass it. The bamboo is really strong... I can jump on a 12mm piece of bamboo that is roughly wing-sized without breaking it so I'm hoping to use this method for fine tuning a design and then make it stronger if they break when I get a design that works!
I'm using the Eppler 817 since it's what i've seen others doing. In my software it gives me great lift/drag ratios but as I'm not proficient in the field it's hard to argue for one versus another.I wanted to get your opinions on which foil section to use and what angle of attack to set the main wing at... Seems many people are going for the Eppler 817, a similar NACA or there's one this guy came up with... http://www.tspeer.com/Hydrofoils/h105/h105.htm
When I look at the Cabrinha foil, it seems totally diferent; being much flatter on the bottom surface.
I have come to the comclusion that the F I J T I approach is best in this case and will probably go with the Eppler to begin with. I 3d printed a 1/4 scale model and tried holding it in the river to see what happened... didn't really learn anything from it other than if I tipped it backwards it produced loads of lift and shot forwards! Maybe 2 lollipop sticks would have done the same!
Angle of Attack... it seems that when riding a foil, the AOA changes loads anyway. Not just from the rider pitching the board forwards and backwards but from the flow of water beneath a choppy surface. Is it best to use zero AOA and see whether you have to ride nose up / nose down or is it best to apply a little bit of AOA to the main wing?
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