Classical Build (s) - Hopefully falcate!

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seeaxe
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Re: Classical Build (s) - Hopefully falcate!

Post by seeaxe » Wed Apr 29, 2020 7:53 pm

Ah well, a bit to late to test pre bracing. I did notice my 2.3mm top sounded very dull when I cut it out, from a knuckle on no particular node type tap and now it rings, so the bracing must be doing something. Sounds kinda ok.
neck all done.jpg
top bracing nearly done.jpg
Will report back in a few days....
Richard

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Re: Classical Build (s) - Hopefully falcate!

Post by seeaxe » Thu Apr 30, 2020 6:43 am

Out of interest i weighed the various bits this morning.

My soundboard weighs 196g. There's some to trim off round the edges but id expect that to not be more than 10 grams. Its Lutz with a thickness is 2.3mm, 10mm high by 5mm wide tapered braces.

Does anyone else weigh theirs and if so what sort of weights do you end up with??

The whole shebang should be about 2kg when its done, not counting any side mass i might need to add
Richard

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Re: Classical Build (s) - Hopefully falcate!

Post by kiwigeo » Thu Apr 30, 2020 8:28 am

I only weigh the plates prior to initial tap testing to derive density values.

I tap at all phases of a build. Tap testing with a mic and software is a great system but at the same time I like keeping a running handle on how the top sounds to the ear through the build process.

seeaxe wrote:
Thu Apr 30, 2020 6:43 am

Does anyone else weigh theirs and if so what sort of weights do you end up with??

The whole shebang should be about 2kg when its done, not counting any side mass i might need to add
Martin

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Re: Classical Build (s) - Hopefully falcate!

Post by seeaxe » Mon May 04, 2020 12:42 pm

Box is now closed and have done the initial tap tests.

I have a pretty clear and consistent T(1,1)2 at 180 Hz however there is no bridge on yet so no stiffness from that. I did try to model the bridge with 20g worth of coins stuck on the top but measured no clear difference.

The back at 250Hz, which is miles away from the top and much too stiff but I left the central brace unscalloped so there's room to move that.

I'm happy enough with this to move on.
Top
3rd try 4 may.JPG
3rd try 4 may.JPG (47.92 KiB) Viewed 3760 times
Back
Back 4 May.JPG
Back 4 May.JPG (48.76 KiB) Viewed 3760 times
Richard

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Re: Classical Build (s) - Hopefully falcate!

Post by seeaxe » Mon May 04, 2020 1:28 pm

This is the stage at which I should do any thinning of the top, If I am going to.

As I see it, with the top at 180hz now, prior to the bridge going on, the (T1,1)2 will only drop with the added mass of around 20g at the moment, unless I can get the bridge down a bit. Its rosewood so I doubt it though.

Going by the approx 1 hz per gram guide at Fig 4.6-3, that's a big drop and puts my top down around 160, well below target. Will the stiffening effect of the bridge increase teh frequency?? Don't know but the books seem to discount that. Plus there are no bindings on and they stiffen things up a bit as I understand.

Anyhoo it seems to me that I would be unwise to do any thinning.
Richard

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Re: Classical Build (s) - Hopefully falcate!

Post by kiwigeo » Mon May 04, 2020 5:08 pm

Richard are you tap testing with the sound hole blocked? I cant see any T(1,1)1 peak on that first plot.
I'd re-tap with sound hole open and if no change in T(1,1)2 then I would consider not doing any thinning of top perimeter.
Martin

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Re: Classical Build (s) - Hopefully falcate!

Post by seeaxe » Tue May 05, 2020 5:49 am

I noticed that too. There's a very small peak around 80 that I think is T1,1. But it's very weak compared to the top and back. My bolt on neck arrangement leaves an air gap which might be affecting it so I tried with the neck bolted on. Didn't seem to make a huge difference. Neither did modelling with a "bridge" of 2 X 2nzd coins.....perhaps I need to use Aussie currency for it to work :D

I need to look at that tutorial Dave M was talking about and redo the tests. They did seem a lot clearer this time though. I think in the past I haven't been waiting long enough for the buffers to fill. All the main peaks appear on the first tap.

Thanks for the help. It's much appreciated.
Richard

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Re: Classical Build (s) - Hopefully falcate!

Post by kiwigeo » Tue May 05, 2020 11:13 am

seeaxe wrote:
Tue May 05, 2020 5:49 am


I need to look at that tutorial Dave M was talking about and redo the tests. They did seem a lot clearer this time though. I think in the past I haven't been waiting long enough for the buffers to fill. All the main peaks appear on the first tap.

Thanks for the help. It's much appreciated.
I can see a tiny peak at 100Hz on both top and back plot.....I suspect this might be your T(1,1)1. Where are you tapping and where are you holding the mike?
Martin

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Re: Classical Build (s) - Hopefully falcate!

Post by seeaxe » Tue May 05, 2020 12:41 pm

Hi Martin
Im tapping at the bridge position and the mike is about 250mm above that. If I move the guitar so the mike is over the soundhole it increases the T1,1, which although fairly small graphwise appears consistently at 85Hz.

All the other frequencies plotted exactly the same today with the neck firmly bolted on (was a bit loose yesterday)
I have the
T(1,1)2 at 181
The back at 258
and something else, not entirely sure what at 300 and 368.
5 May Top neck on.JPG
5 May Top neck on.JPG (51.53 KiB) Viewed 3707 times
mike over soundhole
5 May mike over soundhole.JPG
5 May mike over soundhole.JPG (48.39 KiB) Viewed 3707 times
Richard

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Re: Classical Build (s) - Hopefully falcate!

Post by kiwigeo » Tue May 05, 2020 1:01 pm

I usually have the mike over the sound hole (about 2-300mm away from same) and tap on the bridge area. I think if you do same you'll get a nice sharper T(1,1)1 peak.
Martin

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Re: Classical Build (s) - Hopefully falcate!

Post by seeaxe » Sat May 09, 2020 6:20 pm

A bit of an update. Now have all the bindings on and am in the process of final sanding and prepping for lacquer. As usual I had a few stuff ups on the binding but nothing fatal, to err is human and all that. Overall, Im happy with the ways it went, one my better binding jobs and the clean up was way less work than usual cos I spent a lot more time than I usually do cleaning up the box before I cut the ledges. Tim S's excellent satin box binding and the perfect rebate bearing meant relatively little scraping and sanding. I'm nearly there with the 220 grit, so a couple of grits to go and I'm done with the body, except for a bit of faffing with the back brace, once I have rechecked frequencies.

Anyway here are some pictures.
open back.jpg
early mock up top on.jpg
ready to cut binding rebates.jpg
binding around neck pocket.jpg
back binding and neck pocket.jpg
A bit more work on the neck to do, not entirely happy with the profile yet. I have checked the set up though and sorted that. Fingers crossed of course.

Cheers
Richard

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Re: Classical Build (s) - Hopefully falcate!

Post by kiwigeo » Sat May 09, 2020 7:51 pm

Looking good there Richard. That blackheart sassy is a really nice looking wood.
Martin

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Re: Classical Build (s) - Hopefully falcate!

Post by Semmens Guitars » Sun May 10, 2020 10:01 pm

Nice work on that rosette!! The guitar looks great too!

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Re: Classical Build (s) - Hopefully falcate!

Post by seeaxe » Mon May 11, 2020 7:19 am

Thanks for the comments, it will look even better when its finished.

I tap tested the body again today after final sanding as I was worried I would drop the top frequency doing that. It hasn't changed much if at all which is good. I'm going to leave faffing with the back until I have it finished and the bridge on so I know where I need to be relative to the top.
Top as played after sanding 11 May.JPG
Onwards and upwards
Richard

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Re: Classical Build (s) - Hopefully falcate!

Post by seeaxe » Tue May 19, 2020 6:37 pm

I'm now French polishing the top. Going Ok

For anyone doubting how good an FP finish is relative to other options....

I mixed up a fresh batch, whats called a "2lb cut" which in fact was 112grams of shellac (powdered in my case) with 500mls of alchohol. I made a bit of a mess of this as I tried to do it in too small a container. There's a lot of shellac to dissolve and it takes a while. Afterwards I strained it through cotton t-shirt material and decided I would use a kitchen measuring jug to do that. Even then it kinda went everywhere. Not too worry I thought, it will come off pretty easily. I wiped the jug out with a cloth and took it inside to wash.

By the time I got to the kitchen there was a thick white film over most of the jug and after 2 washes with neat alcohol and 2 washes with literally boiling water and detergent and there's plenty of FP still on the jug!! Scrubbing with a scotchbrite pad doesn't do much to it.

I'm impressed.
Richard

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Re: Classical Build (s) - Hopefully falcate!

Post by kiwigeo » Tue May 19, 2020 7:16 pm

seeaxe wrote:
Tue May 19, 2020 6:37 pm
Afterwards I strained it through cotton t-shirt material and decided I would use a kitchen measuring jug to do that. Even then it kinda went everywhere. Not too worry I thought, it will come off pretty easily. I wiped the jug out with a cloth and took it inside to wash.
Get a pack of those paper funnel with the built in strainer they sell at paint shops. If the measuring jug was plastic then it'll discolour..use glass wherever possible. I use flakes and it usually takes a couple of days for the flakes to fully dissolve.

What sort of shellac are you using. Make sure it's fresh...the stuff has a shelf life.

French Polishing is all about patience :)
Martin

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Re: Classical Build (s) - Hopefully falcate!

Post by seeaxe » Tue May 19, 2020 11:34 pm

Fresh pack of ground blonde shellac.
Richard

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Re: Classical Build (s) - Hopefully falcate!

Post by kiwigeo » Wed May 20, 2020 4:48 pm

Glass container? What's the meths you're using?

seeaxe wrote:
Tue May 19, 2020 11:34 pm
Fresh pack of ground blonde shellac.
Martin

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Re: Classical Build (s) - Hopefully falcate!

Post by seeaxe » Wed May 20, 2020 8:57 pm

I mixed and store the cut in a glass jar. When using it i put some in a small plastic (PE??) bottle with a tip so i can apply it accurately to the fad. I'm using "shellac reducer" which is methanol I believe.
Its all going well at present, so I'm happy.
Richard

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Re: Classical Build (s) - Hopefully falcate!

Post by johnparchem » Wed May 20, 2020 11:15 pm

The guitar looks good. I also wonder about the consistent lack of T(1,1)1 on your plots. I just wonder in you setup something is filtering out the lower frequencies. It should be showing up very clear. You can hum into the box around the frequency you think it is an hear where it resonates. I have found that the top resonance goes up almost 10 Hz when I put a bridge on a classical with no lower transverse brace not down. On my steep strings guitars the T1(1,1)2 goes down. I am guessing with the thinner top and no lower transverse brace there is a real lack of cross stiffness that the bridge corrects.

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Re: Classical Build (s) - Hopefully falcate!

Post by kiwigeo » Thu May 21, 2020 7:54 am

I believe Richard has his mike over the bridge. I think holding it over the sound hole will result in a better T(1,1)1 response.
johnparchem wrote:
Wed May 20, 2020 11:15 pm
The guitar looks good. I also wonder about the consistent lack of T(1,1)1 on your plots. I just wonder in you setup something is filtering out the lower frequencies. It should be showing up very clear. You can hum into the box around the frequency you think it is an hear where it resonates. I have found that the top resonance goes up almost 10 Hz when I put a bridge on a classical with no lower transverse brace not down. On my steep strings guitars the T1(1,1)2 goes down. I am guessing with the thinner top and no lower transverse brace there is a real lack of cross stiffness that the bridge corrects.
Martin

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Re: Classical Build (s) - Hopefully falcate!

Post by kiwigeo » Thu May 21, 2020 7:55 am

Do you have specs for that "shellac reducer"?
seeaxe wrote:
Wed May 20, 2020 8:57 pm
I mixed and store the cut in a glass jar. When using it i put some in a small plastic (PE??) bottle with a tip so i can apply it accurately to the fad. I'm using "shellac reducer" which is methanol I believe.
Its all going well at present, so I'm happy.
Martin

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Re: Classical Build (s) - Hopefully falcate!

Post by seeaxe » Thu May 21, 2020 7:16 pm

kiwigeo wrote:
Thu May 21, 2020 7:54 am
I believe Richard has his mike over the bridge. I think holding it over the sound hole will result in a better T(1,1)1 response.
johnparchem wrote:
Wed May 20, 2020 11:15 pm
The guitar looks good. I also wonder about the consistent lack of T(1,1)1 on your plots. I just wonder in you setup something is filtering out the lower frequencies. It should be showing up very clear. You can hum into the box around the frequency you think it is an hear where it resonates. I have found that the top resonance goes up almost 10 Hz when I put a bridge on a classical with no lower transverse brace not down. On my steep strings guitars the T1(1,1)2 goes down. I am guessing with the thinner top and no lower transverse brace there is a real lack of cross stiffness that the bridge corrects.
I did the last tests with the mike over the sound hole - it improved the peak.

I'm hoping to gain a few Hz for T1,1,2 when the bridge goes on. Too low at the moment.

FP is going OK
Fp starting on the top.jpg
This is what I'm using.
20200521_210633.jpg
Richard

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Re: Classical Build (s) - Hopefully falcate!

Post by johnparchem » Thu May 21, 2020 10:46 pm

Careful with the methanol it is very toxic, even the fumes. In the US cheap denatured alcohol is about half methanol. I avoid it for pure ethanol as I do not want to wear a mask through all the time it takes to French Polish.
Methanol is highly flammable and toxic. Direct ingestion of more than 10mL can cause permanent blindness by destruction of the optic nerve, poisoning of the central nervous system, coma and possibly death. These hazards are also true if methanol vapors are inhaled.

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Re: Classical Build (s) - Hopefully falcate!

Post by seeaxe » Fri May 22, 2020 5:57 am

Thanks for that.
Richard

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