MikeC
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Posts posted by MikeC
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I agree completely!
Having been here on MN for a long time I've gotten used to thinking in millimeters but this caliper is measured in 64ths and it's the only one I've got. Eventually I will get one that is in millimeters but for now this one works ok just for making a visual thickness map. I found a conversion chart. One 64th is 0.4 millimeter. With this caliper and two pair of cheap reading glasses I was able to measure to within a half of a 64th so accuracy in measuring was about 0.2 millimeter, not bad. Actually no fractions are needed, just whole numbers, only using the numerator part since the denominator is always 64. The measurements in this plot range from a low of 5.5 in the thinnest part to a high of 10 on the endblock platform. While excel is not the ideal software for this purpose it at least helps to visualize the thickness pattern. I thought this plate was finished but now realize it needs more thinning.
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I decided to map the thickness using graph paper and a grid on the back plate. I can see areas that still need thinning. Excel doesn't really do a very good job of making a contour map. It's not very granular. My caliper is in 64ths of an inch.
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3 hours ago, Bodacious Cowboy said:What's the density of your maple?
That's a good question. I haven't learned how to measure density yet. How is that done?
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How common is it to have to plane the neck surface after it's finished?
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I've watched all of Davide's videos multiple times. They are a valuable resource! I think I could have done better in the recurve perhaps but I can't match his machine like precision and with experience I've gotten from the back plate, the belly plate should turn out better. Regarding the end block areas, when looking at CT scans and the Strad3D videos that area of the plate is very flat across the end block area and even beyond a little ways. I think one mistake beginners make as I did on my first VSO is making a scoop in that area i.e. not having it flat enough. I'll try to post some pictures later to illustrate.
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Watch all of Davide Sora's videos.
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Thank you for the feedback Andreas. I'm learning a lot in making the back plate. Hopefully that knowledge will transfer over to the belly plate.
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After some more thinning.. the back plate weight is 125 grams which I think is still a little heavy. Audacity plot has peaks at 121hz , 370hz and 694hz
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well it's now at 125 grams
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2 hours ago, David Beard said:Do you twist the neck and sides assemby around them for alignment, before settling the outline. Then allow the outline to at least partially follow the resulting assymetries of the corners and sides?
That is their functional purpose.
No, in this build I'm not doing the old baroque method where the neck is already attached to the ribs. By functional I mean that I use the pins to quickly position the plate on the ribs for gluing. By using the pins I know the plate will be positioned correctly on the end blocks then that makes the rest much easier. Without the pins the glue up process would be more difficult and with hide glue you have limited working time. Maybe on the next build I'll go for baroque.
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I guess if I cut Fs in the back the violin would play in stereo?
Actually thinking about it this morning it may be a bit thick still near the edges. When I get time tonight I'll examine the CT scans and compare to my arching and thickness around the edges. I think my arches may still be a bit full in the recurve area so may still need some thinning there.
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6 hours ago, Don Noon said:If you're making a Titian model (approx. 353 x 206mm), then 135.9g might be good... if you're making a solid-body electric version.
If it was me, I would not go over 100g for that size. Maybe a little higher for extremely dense wood.
that made me laugh. Maybe a solid body next...
It's strange, I think the grads are about right, a little over 4mm in the center tapering to about 2.5mm in the upper and lower bouts. I could go thinner but I thought it was about right so I'm not sure where all the extra weight is. Could it be that the maple is unusually dense? Or am I just unsually dense?
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I put them just inside the purfling since I do the purfling before I put the plat on the ribs. If I were to put the plate on first and then the purfling I would have the purfling go half way through them Strad style. For me they are functional not decorative... or maybe a bit of both.
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So the plate weight is 135.9 grams. That's a bit on the heavy side isn't it?
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Well since I'm using a Strad mould and have templates from the Titian poster I was thinking of going kind of thin and Strad like. Although I like some of the roughness of DelGesu so I may leave some visible tool marks here and there.
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I have to pick up a few things at the store tonight. A gram scale is on the list. I'm building from a copy of Strad's PG mould but don't remember the exact measurement off hand. Ribs may not be tight to the mould but they are close. What do you mean by compliant or resistant?
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39 minutes ago, Don Noon said:Fingers aren't the best thing for plate tapping, as there's a heavy hand and arm attached to the finger, and the plate moves around a lot. It's plenty good enough for just getting plate mode frequencies, though.
I use a 5g "hammer" with a vinyl cabinet bumper on the end for tapping. It's overkill for plate frequencies, but I have it for damping measurements, where the test piece has to be held at a consistent distance from the microphone. The amplitude variations (see how much Davide's plates move relative to the microphone) don't matter for frequency, but totally mess up damping calculations. Since I have the hammer, I use it for plate frequencies as well.
For now I'm low tech so fingers will have to do. I don't think I'll get more involved than simple mode testing. For M5 385hz is a bit on the high side isn't it? I wonder should I try to lower it by thinning the plate some more.
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2 hours ago, jowl said:have a look at Sora's video: https://www.youtube.com/playlist?list=PLaxadm6POX7Hy2CxMIMU5wcOOBxxNsq5r
Thanks for the link. That's one of his videos that I have not watched until now since I've just now got that stage of the build. There's a lot of good info on modes in that video.
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Thanks Jim, I agree, from a normal viewing distance without my reading glasses the joints are invisible and the purfling miters don't look all that bad. :). Next step is gluing the back to the ribs and then start working on the belly plate.
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Hi Jacob, Crotch of a tree is where a limb grows out from the trunk. There can be some figured wood in that area.
Personally I would not stain the spruce. I don't like dark stains and prefer the natural beauty of the wood to show.
Guitars look good with rosewood backs and blond spruce tops, I think a fiddle like that would look good too. I'm not sure about purfling though, the black strips would not show up well on walnut since it's such a dark wood.
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Wow those are really thin in the upper and lower bouts. What is that about 1mm ?
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Holding on the nodes about where I think they are and tapping with my finger. Mic directly in front of the plate. I get various results depending on where I hold it. Mode5 seems to be about 385hz. I'm new to this so just trying to figure it out and hopefully get my plates in the ballpark of what's reasonable.
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Who says it's hard to inlay purfling! Three scarf joints later...
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Well here's the wonky purfling miter and the black mastic repair. Actually I mixed casein glue with powdered artists charcoal drawing stick for the filler.
Before and after. Still not great but anyone with over 40 eyesight won't notice.
MikeC's bench
in Contemporary Maker's Gallery
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Cowboy, I have a feeling this may be some rather dense maple. This weekend I'm going to measure the density using scraps left over from cutting out the back.
Catnip that's a brilliant idea! I should have thought of multiplying by 0.4 in the spreadsheet. I'll do that tonight and see what it is in millimeters.