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  1. #1
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    Default Carbon Fibre violin ( Build 2 )

    so my first ever violin got good reports back from the professional players its time to start on my second one , once again from scratch , but a little bit wiser

    Once again it starts with a plan , whats changed (since the last violin )
    To make the moulds using a cnc machine , not hand carved out of wax
    Use a non stick mould material , "polypropylene sheet" should work well
    Polish those moulds so a finished product comes off them with out any mould release
    use the cnc machine to draw perf lines , was thinking of finishing the first one in a perlex resin
    and cut out the peace's using the cnc
    and put a scroll on it

    any one who missed my 1st Carbon fibre violin ,its here > https://www.woodworkforums.com/f98/vi...cratch-110427/


    so first up is to draw a violin in Turbo CAD ( not that easy )
    here is where im at ( pic below ) , have the shape drawn out added the curves and are now laying the mesh over the curves

    yer like my first one , this will take a while

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  3. #2
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    Default

    I can imagine drawing it all up on computer would be a challenge. Are you using recognised profiles, eg The Messiah or drawing cycloid curves from scratch?
    "We must never become callous. When we experience the conflicts ever more deeply we are living in truth. The quiet conscience is an invention of the devil." - Albert Schweizer

    My blog. http://theupanddownblog.blogspot.com

  4. #3
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    im using sine waves ,
    the cycloid curves have about 10 variables ,a sinewave has 2 , width and height
    sine waves were not invented until 1880's so thats why the masters did not use them (back before the 1880's , sound didnt travel in a sine wave ), they used cycloid curves and tinkerd around to get the best sound , they were pretty dam close to a sine wave back in the 1700,s
    out of the 4 plates that i made making the 1st violin , 3 different cycloids and a sine , the harmonics of the sine were a lot cleaner ( violin plate and ribs (no back ) bolted down with a resonator on the bridge point ) all the main harmonics were there , with out the low level (mash)
    the shape of the violin is also from my own drawings , believe it or not , all from one single measurement , the bridge width ,

    end up same length as a "strad" , same width upper bout , 4mm thinner at the lower bout , and the wings are 10mm closer than a "strad" ,

    strads lower bout's seam to be stretched to make the bottom of the violin a lot flatter , ive been mucking around with my drawings , using a different ratio for circle size , and have pretty well hit "strads" shape ,using the spacings of the frets as the ratio's for the circles , "the 17.817 " ,
    the voice recognition soft ware i have shows a main acoustic harmonic 8 notes(semi's) of the one played , and a few more that are in the same position for all the notes ,( 3 original strad violins recordings donated by a bloke who thinks we are on to something )
    so using those ratio's i ended up with 1/2mm of a strad template all around , but there is a lot of "whats the reason for that " best fit sizes in there , where the one im making there is a reason for every circle diameter and placement

  5. #4
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    Default

    What's it like working with a mould for this sort of thing? I made a neck through bass with carbon fibre for body wings recently, but that was done by laying the fibre over a foam core, bit of effort in that one.
    How did the last one sound too? I'd imagine the brightness of the carbon fibre would suit a violin's tone fairly well

  6. #5
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    the moulds make the finish a lot nicer , laying carbon over a core and wetting it down , even if you vacuum bag it , it never sits real flat , with a mould the side you see is against the mould , so you put down your 3 layers of clear , lay your fabric layers down and then vacuum them tight , then add the resin ( infusion method ) , if your moulds are perfect , all it needs is a buff

    i found my first ever "plate's" were better at being used for brass bells , so i started mucking around with different materials ,in different layers and graduations , to get the tap tones to sound like timber , got it pretty well smack on , after about 20 plates

    with the 1st violin the 4 players who all played it on the same day loved it , and said "nice and loud with warmth , and quick off the bow in response to bow movement" , the finger board is a bit high at the bridge end so playing the high notes gets you buzzing , when i said i could slash its neck and reposition the angle of the finger board , they all gasped and said NO , leave it as it is , almost refused to give it back until i said i wouldnt slash its neck , ill keep it the way it is as my 1st

  7. #6
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    just an up date
    drawing a violin in cad is not easy , went over board and accuracy is well over 1/100th mm ,
    finally finished the Z point heights for the plates , 7000 points to set a hight , what a mission

    set the top and bottom plates up with a pitch and marked the inside rib line to make the rib mould

    ready to CNC the moulds out of MDF first ( test ) then HDPE plastic , once ive got my plans perfected ( sound tested ) ill make aluminium moulds

    this batch will be 5 violins , with different plate heights , just to see how much sound difference plate height makes

    cheers ken

  8. #7
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    Default Non stick alloy

    Very interesting Sniff is it your CNC machine? Also wondering how you will finish the surface of the "female" aluminium molds?

    Steve

  9. #8
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    Quote Originally Posted by kamusur View Post
    Very interesting Sniff is it your CNC machine? Also wondering how you will finish the surface of the "female" aluminium molds?

    Steve
    yes still setting it up ( cnc machine)

    haven't got that far yet but expect a lot of elbow grease
    the first moulds will be "High Density Polyproperlene " HDPE , ive tryed some resin on it and as long as its finished finer than 400grit , it releases easy , with out any mould release ( resin wont bond to coke bottle plastic , polyproperlene)

    with aluminium you will need mould release , a spray on PVA based or wax , i dont trust wax with the resin i use , it eats it

  10. #9
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    Default CF Violin

    Thanks for the answers Sniff. Not sure what resin you are using but have you considered trying a different form of wax, what sort of resin are you using by the way?

    Steve

  11. #10
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    ATL composites , infusion resin , "Warm temp cure " hardener , the hardener is corrosive as hell

    ALT make West Sysytem , i use west system as clear coats

    blue PVA based mould release works fine , but with the HDPE moulds i wont need wax or mould release

    i found wax to be a hindrance in clear coating the moulds before laying up , the first coat beads ( not good ) off the spray gun , blue PVA mould release is a lot better

  12. #11
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    Default Mold release

    My first thought was to try something that probably wasn't Napthalenic based (the wax that is) at least Parrifinic or something organic instead like a Bees' wax that wouldn't react with the resin or be dissolved by it.

    Yes any polyester resin that uses a Ketone or Benzoic Peroxide as a hardener can give off more heat even by way of overdoing the catalyst (yep a hot mix or even hotter mix lol) than say an epoxy with equal part cat and base and i remember a work colleague way back was using it as a filler for damaged horses feet without realising how hot the hooves got, but he swapped to an epoxy and said it never got as warm when it was gelling.

    Sorry to hear about the 'beading' Sniff. Most of my resin spraying experience involved polyester because it was about a 1/5 of the price of any epoxy (shrinkage was not considered a worry) available and i never had a problem with beading or mold release (wax) dissolving luckily lol.

    Steve
    Last edited by kamusur; 29th December 2011 at 05:42 PM. Reason: Spelling

  13. #12
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    hardness is my concern , polyesters just arnt up to producing tone quality composites
    this mix is a 75% / 25% by weight , not volume , and accuracy is a must 5% out and its stuffed , i just use 0.1gram scales , 75g of resin to finish weight of 100g with hardener

    yer this stuff gets real hot in large thickness's , at 1 inch deep it starts to smoke and the clear colour go's black , i have to chill the resin ,and hold in ice bucket to infuse it ( 1 hour ) or it will "cook " and go off in 15min

    30c back ground temp

  14. #13
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    Default 2012 almost

    Keep up the good work Sniff and don't forget to keep us posted with pictures.


    Steve

  15. #14
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    Default

    this is looking great sniff im excited to see how it turns out
    also have you though about maybe making an electric 5-string violin? just an idea
    tools?: check
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    finding out you did your build backwards?: priceless

  16. #15
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    yes ,5 stings an easy modification , been working on some CAD drawings of wide necks with the 5th string extending to where the scroll should be , just working out the stress so the neck doesn't twist , a real weird neck

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