Current Build - Falcate Braced Multiscale OM cutaway

[kiwigeo]

LOL...all you sharp eyed Suzies picked up in the clamp overkill...but you missed the fact I forgot to drill the truss rod adjuster hole in the UTB.

I don't drill a hole through the UTB any more. I reckon it weakens things too much.

Regards

You have a point but since the UTB has CF reinforcing on top I think it's less of an issue.

[johnparchem]

LOL...all you sharp eyed Suzies picked up in the clamp overkill...but you missed the fact I forgot to drill the truss rod adjuster hole in the UTB.

I don't drill a hole through the UTB any more. I reckon it weakens things too much.

Regards

Really? I though the whole concept of I beams is that the stuff in the center does not matter as much an the top and bottom. I know building code wise there is no issue in putting a pipe through a joist as long as it is a hole in the beam not a notch. I would think that there is not a whole lot of difference in the strength of the UTB with a hole up from the edge of the brace and one without the hole even before gluing it down on the top.

[Dave M]

Martin we've talked about this before. That bending of the cutaway is still giving you grief. It is also getting expensive. If you've had to throw away three sides...

I have to admit to giving in, I have started a steel string build without a cutaway - the friend who may buy it (if it is good enough) reckons he can live without one. We are definitely missing something are'nt we. These other buggers seem to be able to do this. Mind they don't tell us how many sides they throw away!

Anyway I wondered about the width of your falcate braces? Is it just a trick of the photography or are they a bit wider than normal?
I have found the only way I can do the tight curves is to use four laminations rather than three using spruce. Even then they are''nt that pretty.

Nice clean job by the way. That epoxy does like to get everywhere.

Dave

[kiwigeo]

Hi Dave,

Thanks for the positive comments...always good to receive a compliment from one of my favourite builders.

Cutaways....I don't actually build alot of guitars with cutaways so this was a bit of a learning experience. I did it by hand on the iron while most others use a blanket and form.

The falcate braces.....the pieces of KBP were thinned to around 2mm so final glued up thickness of the braces is around 6mm. The KBP bends a whole lot easier than spruce....I only have to do a quick session on the bending iron with the shorter secondary braces prior to gluing up. There's a bit of spring back when the primary braces come off the gluing jig but its easy enough to bend the end of the brace into correct position while its in the go bar deck being glued in.

The epoxy..yeah it gets everywhere. The trick is to just brush on enough resin to do the job. Too much and the CF tow starts floating....too little and the brace will come lose once the clamps are off.

Martin we've talked about this before. That bending of the cutaway is still giving you grief. It is also getting expensive. If you've had to throw away three sides...

I have to admit to giving in, I have started a steel string build without a cutaway - the friend who may buy it (if it is good enough) reckons he can live without one. We are definitely missing something are'nt we. These other buggers seem to be able to do this. Mind they don't tell us how many sides they throw away!

Anyway I wondered about the width of your falcate braces? Is it just a trick of the photography or are they a bit wider than normal?
I have found the only way I can do the tight curves is to use four laminations rather than three using spruce. Even then they are''nt that pretty.

Nice clean job by the way. That epoxy does like to get everywhere.

Dave

[kiwigeo]

Today was spent profiling the top linings, cutting insets for UTB and fitting the back. The most important part of the top fitting is getting the profile of the upper bout correct.....critical as the neck geometry and string height at the saddle is dependent on the latter.

Pieces of kerfed lining are superglued under the top to temporarily hold the top in correct alignment until glue up. A straight edge is placed along upper bout to check upper bout profile......the straight edge should be around 2.5mm above saddle position...which is exactly what it was!!

[kiwigeo]

Bracing pockets cut, lower back brace scalloped and the back glued up......and no smart arse comments about the number of clamps!!

[kiwigeo]

Back rough trimmed on the router table followed by some tidying up inside the box...you never know who might be peering through the soundhole!

[kiwigeo]

Today's tasks.....fine tuning the arching on the upper bout to get straight edge clearance over saddle at 2.5mm. Made up the bridge gluing caul, got the top glue in (hide glue) and then trimmed the top on the router table. This is the point in a build where one starts to see a guitar.

[kiwigeo]

Rough results from initial tap test:

T(1,1)1 - 95Hz
T(1,1)2 - 175Hz
T(1,1)3 - 210Hz The back appears to be coupling with top.....

Initial plan is to thin periphery of lower bout which should drop top resonances by up to 5Hz. The back - will consider stiffening up the main back brace to bring the frequency up to around 226Hz.

[blackalex1952]

Are you worried that the 175 might be a little low? Should sound nice for a four string!

[Dave M]

Crickey Martin you are cracking on with that!

The view through the soundhole should impress anybody.

Do keep reporting the frequencies, I should be following in your footsteps soon so all info is useful

[johnparchem]

Rough results from initial tap test:

T(1,1)1 - 95Hz
T(1,1)2 - 175Hz
T(1,1)3 - 210Hz The back appears to be coupling with top.....

Initial plan is to thin periphery of lower bout which should drop top resonances by up to 5Hz. The back - will consider stiffening up the main back brace to bring the frequency up to around 226Hz.

I am a little confused that you want to drop from 175 Hz to 170 Hz. I think that would take you close to 160 Hz strung up. If the 175 Hz was a typo at this point I would leave the top alone even if it was in the 185 Hz to 190 Hz range.

[Nick]

Hmmm not sure about all this T(1,1) type talk (still haven't read 'the books' yet ) but it sure is looking good

[kiwigeo]

Rough results from initial tap test:

T(1,1)1 - 95Hz
T(1,1)2 - 175Hz
T(1,1)3 - 210Hz The back appears to be coupling with top.....

Initial plan is to thin periphery of lower bout which should drop top resonances by up to 5Hz. The back - will consider stiffening up the main back brace to bring the frequency up to around 226Hz.

I am a little confused that you want to drop from 175 Hz to 170 Hz. I think that would take you close to 160 Hz strung up. If the 175 Hz was a typo at this point I would leave the top alone even if it was in the 185 Hz to 190 Hz range.

Hi John,

I was using Trevor's recommended frequencies of 170 or 180Hz for a medium bodied steel string. I'll hold off thinning the top until I think about it some more and confer with Trevor and others.

Yesterdays session was only a rough run so will do a few runs today and post up results.

[kiwigeo]

Hmmm not sure about all this T(1,1) type talk (still haven't read 'the books' yet ) but it sure is looking good

Sorry Nick

T(1,1)1 - air resonance
T(1,1)2 main top
T(1,1)3 - main back

Christmas is coming up...time to start leaving photocopies of the front of The Books lying around the house.

[Trevor Gore]

That T(1,1)2 seems low already, as the others have mentioned. Do you still have that bridge caul attached inside?

[Nick]

Hmmm not sure about all this T(1,1) type talk (still haven't read 'the books' yet ) but it sure is looking good

Sorry Nick

T(1,1)1 - air resonance
T(1,1)2 main top
T(1,1)3 - main back

Christmas is coming up...time to start leaving photocopies of the front of The Books lying around the house.

I've got the books, I actually got them pretty much when they first came out, fortunately when I was single, now I'm married the odds of being able to afford them have lengthened! But much to my shame , I just haven't sat down with them yet and become familiar with their contents.

[Wayde Christie]

IMG_1422.jpg (87.07 KiB) Viewed 18073 times

Colossal 'duh' moment for me here.

I've been looking for a sandpaper disc big enough to fit my radius dish for a while.

Why didn't I just use a bunch of straight adhesive strips like this?

Cos I'm not real smart

[kiwigeo]

IMG_1422.jpg

Colossal 'duh' moment for me here.

I've been looking for a sandpaper disc big enough to fit my radius dish for a while.

Why didn't I just use a bunch of straight adhesive strips like this?

Cos I'm not real smart

Don't be hard on your self mate. This work around works but the downside is the shitloads of double sided tape you go through.

[blackalex1952]

Wade, you can buy large sheets of high quality sandpaper from floor sanding suppliers, in all sorts of sizes.

[blackalex1952]

Here is a summary of "ideal" resonances and the parameters that can be changed and which ones influence each other.
See Alan Lloyd's website for more:https://alanlloydguitars.wordpress.com/ ... acoustics/

[kiwigeo]

Ok here are results of Tap testing - VA plots and Chladni Patterns:

1. Tapping Top with Soundhole Unblocked. Mic at soundhole.

T(1,1)1 - 95.4Hz
T(1,1)2 - 175.3Hz
T(1,1)3 - 204.9Hz

2. Tapping Top with Soundhole Blocked. Mic over saddle area.

T(1,1)2 - 170Hz

Top SH Blocked (2).png (9.21 KiB) Viewed 18048 times

3. Tapping back (Soundhole unblocked) with mic on back

T(1,1)3 - 210Hz

[blackalex1952]

Assuming from the photo that this is without the bridge and side mass? If so, I would be experimenting with double sided tape and mass added to the bridge area and sides before modifying braces...Then make a bridge of the weight that works, temporarily glue with weak hide glue or gelatin if I wanted to string it up with the neck on to see what's going on....I'm no expert, but currently messing with VA and tea leaves myself...

[kiwigeo]

Assuming from the photo that this is without the bridge and side mass? If so, I would be experimenting with double sided tape and mass added to the bridge area and sides before modifying braces...Then make a bridge of the weight that works, temporarily glue with weak hide glue or gelatin if I wanted to string it up with the neck on to see what's going on....I'm no expert, but currently messing with VA and tea leaves myself...

Guitar is in the raw..ie no binding no bridge.

Modifying braces is not an option as top braces have CF on top of them. Adding side weights will drop main top resonance....I want to go the other way.

[blackalex1952]

I have a suggestion, it might not be so important, but why don't we all use some kind of standard for the x and y axis with our frequency graphs when comparing the basic resonances? For example, I suggest 50Hz to 1000Hz for the x axis, and the y could also be set up in a standard way so that the peaks are quite clearly defined. That would make visual comparison easier, perhaps? I wouldn't get into a debate around the subject, only to say that we could establish a "convention"...Perhaps Trevor Gore could chime in here?
I have been copying my frequency graphs from Visual Analyser using "snipping tool" (free) and I can size the images so that I can see two of them on my desktop simultaneously for comparison...eg with and without side mass or with and without bridge mass. The reason I use snipping tool is because, on my computer, the screenshot function in VA simply won't work...neither will the presets. Must be the version of windows that I have. I've tried different versions of VA.