Classical Build (s) - Hopefully falcate!

[kiwigeo]

As drawn the secondaries run just under the transition section of the bridge. To get the bridges really light I end up with super thin wings, so they wont have much torsional stiffness. Is there a particular reason to not put them under the main part of the bridge?, other than spacing?

Cheers

If you look at Trevor's books his secondary braces pass under the bridge wings....the wings on a classical are usually a bit thinner than on a steel string so more reason to have a brace running underneath.

[seeaxe]

Not quite following that logic Martin sorry.. I must be missing something

The bridge is transferring the input from the strings to the wider soundboard. Its ability to do that relates to its stiffness of the bridge at any point. Its much stiffer in the main section than in the wings so thats why I put the sec brace closer to the centre. I would have thought that if I move the brace away to the middle of the (thin and flexible) wings that will de-couple it from the bridge displacements, relative to the main body.

[WJ Guitars]

I have also used spruce to make Falcate Bracing and had no issues. Refer to photo attachment.

Regards
Wayne
https://wjguitars.wixsite.com/mysite-1

[Dave M]

I always struggle bending spruce so use 4 laminations. Particularly the secondaries. It works fine

[kiwigeo]

I don't have the books handy right now. With a steel string you generally run the cross brace (on a conv braced instrument) or secondary falcate brace under the bridge wing. On a falcate braced SS Trevor recommends that the inboard end of the tertiary brace overlaps the end of the bridge wing. Less tension on a classical but Ive always applied the same guidelines on my falcate classicals.

Not quite following that logic Martin sorry.. I must be missing something

The bridge is transferring the input from the strings to the wider soundboard. Its ability to do that relates to its stiffness of the bridge at any point. Its much stiffer in the main section than in the wings so thats why I put the sec brace closer to the centre. I would have thought that if I move the brace away to the middle of the (thin and flexible) wings that will de-couple it from the bridge displacements, relative to the main body.

[seeaxe]

Thanks again Martin.
I checked my layout against Trevor's plans for the SS falcate and the primaries came out nearly the same just rotated a fraggle. My secondaries don't bend as sharply though so i might adjust that. Otherwise i was pretty happy that there was fairly good agreement. If i had thought to do it i could probably have just used the ss plan to make a template. Is that what others did??

[kiwigeo]

None of my falcate builds have been strictly to the plans in Trevors books. The last build was a multiscale so I had to work out brace layout according to the guidelines in Trevor's books. The braces were also assymetrical so making them was twice as much work as for a conventionally scaled instrument

Thanks again Martin.
I checked my layout against Trevor's plans for the SS falcate and the primaries came out nearly the same just rotated a fraggle. My secondaries don't bend as sharply though so i might adjust that. Otherwise i was pretty happy that there was fairly good agreement. If i had thought to do it i could probably have just used the ss plan to make a template. Is that what others did??

[Dave M]

Richard yes I essentially used the SS layout with a little tweaking for the different body shape.

Dave M

[seeaxe]

Thanks guys, Ill adjust a bit then press on.
Cheers

[seeaxe]

Forgot to ask...did you guys put that little diagonal brace that is on the plans near the bottom of the soundboard on your classicals???

[kiwigeo]

Yes....I include this brace to reinforce the top joint. On my non falcate builds I'd usually put a small patch or two along the seam in same location.

Forgot to ask...did you guys put that little diagonal brace that is on the plans near the bottom of the soundboard on your classicals???

[seeaxe]

Today was brace day... The primaries are easy but the secondary braces gave me a lot of grief even using 4 plies. The only way I could get the spruce to bend was to wet it. I've put that in the mould to dry out over night and I will attempt to glue it tomorrow. Might start again though, as its not perfect.

Progress Pics

[WJ Guitars]

Great to see you keeping up the various challenges as you progress.

I used 'Adirondack Spruce' for my braces. The secondary braces were a little more difficult to bend. I did break one laminate. I then had to be more careful and patience when using the bending iron for the secondary brace bends. I was able to only require 3 laminates per brace.

My build is a Steel String version and I have now finished the guitar last week and I am very happy with the result. I will post it in the 'Gallery' soon.

I'm certain you will succeed! It will be worth the effort.

Wayne
https://wjguitars.wixsite.com/mysite-1

[Dave M]

Yup lots of those misshapen and broken plies. As Wayne says real care on the iron and one does get better. I still do 4 plies and sometimes you hit a spruce that simply won't go. Try a completely different batch.

Cheers Dave

[seeaxe]

Cheers Dave, problem is I only have one batch... But all is well as I bent them no trouble this morning, with a lot of wetting. Ill glue those up tomorrow. Had a big glue up session to day and not much else got done on my guitar. My sons electric is coming along though!!

[seeaxe]

Last brace glued up today so tomorrow top bracing is all done.

Made up a spreadsheet last night to work out brace height but cannot reproduce Trevors numbers of 15 to 18Nm2. Im getting nearly ten times this so need to check through my numbers.

Anyone care to share how they are representing the CF in rhat calculation? I have it as another element at top and bottom of the brace. Minimal height but significant width.

I recall some discussion on the forum so will do a search later when im at my pc.

Making progress.

[kiwigeo]

Brace height will affect overall stiffness more than width. I haven't bothered to do any calculations to work out brace height. I run with Trevor's figures on his plans. I actually measure stiffness of the bracing stock before making up braces and if its a bit low side I increase the height by a few mms.

Anyone care to share how they are representing the CF in rhat calculation? I have it as another element at top and bottom of the brace. Minimal height but significant width.

[seeaxe]

Thanks again Martin.

I may be overthinking all this but.... as far as I am aware there is no classical falcate plan in the books. At least in the edition I have. So I can't follow Trevor's plans, for a classical.

As for not doing calcs for brace height, I guess I'm not going to be doing any either. The primary brace on Trevors SS falcate plan is 7mm high. As you're probably aware, adding a couple of mms to that will more than double the stiffness.

Likewise the tap method tells me my top should be 1.75mm thick. Book says 2.2 minimum as a general rule. Ill be sticking on the higher side of that to begin with.

Seems like I need to follow the general guidance and rely on being able to take material away to make things less stiff rather than build too light and not be able to increase stiffness. The real test will be the resonances/spectra, when I finally get there.

Anyway, enough number crunching. Back to the build log

I finished the last falcate brace so now can get on with the soundboard. I glued that up last night and put it through the sander this morning. Lutz spruce with two very prominent "go faster" stripes. Looks nice, or at least, I like it.

Routed out the rosette channel and put the first and main ring in using the block I made before. One "stick" about 200 long will do two rosettes.

[Mark McLean]

Richard, this is looking great. Lockdown has been a very productive time for you. This doesn’t get counted in GDP figures but I think many of us are doing important things right now!

[seeaxe]

GDP...guitar and dust production.. plenty of the latter in my shop Not for the first time does it occur to me that we scour the planet for the most expensive wood we can find then cut saw chisel and sand a good deal of it into a pile on the floor and then chuck it out.

Anyhoo enough philosopherising, on with the job.

Oops.

15 mins with the dremel fixed that though and overall I am very happy with how the rosette has turned out. It definitely looks hand made which was the whole point of the exercise. I really enjoyed making it and I have enough "block" to do another one of the central bit, just need to make more outer which I would do a little differently anyway - less black more brown.

The back is braced and fitted to the sides. I have left the central brace unmolested for now. Easier to take material off than put it back as Trevor says.

With this done I can turn my attention to the all important top bracing.

Question for the day.... bridge patch for classical top. I'm sure i have read a description in the books of how this is done but I'm blowed if I can find it. Does anyone recall where it is? Meantime I'll keep looking.

Cheers

[kiwigeo]

No bridge patch for a classical Richard. There's piles of CF in the Gore style classical bridge.

[seeaxe]

I have nearly finished my first falcate braced top. Just have the CF to go on the top of the primary braces. Not as hard as i had expected but not the prettiest to look at. Bits of CF peek out from underneath the odd brace and i managed to put lots of epoxy in places that didn't need it.

Question...when i was putting the CF tow down on curves say for secondary braces it doesnt want to bend in plane and "sits up" . Under the brace this gets squashed but it will be visible on top. Any way of getting around this? (Too late for this build but ill probably go on to the next one soon)

Have also glued my fretboard on today and rough shaped the neck. Just need a couple more weeks in lockdown.....

[kiwigeo]

Question...when i was putting the CF tow down on curves say for secondary braces it doesnt want to bend in plane and "sits up" . Under the brace this gets squashed but it will be visible on top. Any way of getting around this? (Too late for this build but ill probably go on to the next one soon)

It's something you get better at with each job. I try and not put too much epoxy down so the tow "floats". I lay the tow into the epoxy guiding it with a small paint brush which I form into a point. When I lay the brace down any obvious two poking out can be coaxked under the brace with the paint brush before applying the go bars to the brace.

[seeaxe]

So bracing all done now. Neck finished. Back is done. Next job will be to start closing up the box.

Is there any point in tap testing the top or back before they go on?

Cheers

[kiwigeo]

I usually do a tap test on my braced up tops and backs more to get a feel for the sound of same rather than to gather peak data....the shape of the plates has changed since the initial free plate tap testing. One thing I do is tap test after Ive cut out the back and front on the band saw so I can get an idea of how the bracing changes the free plate tap test results.

So bracing all done now. Neck finished. Back is done. Next job will be to start closing up the box.

Is there any point in tap testing the top or back before they go on?

Cheers