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  #61  
Old 08-17-2016, 10:19 AM
charles Tauber charles Tauber is offline
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Originally Posted by emmsone View Post
Thanks Charles,
I'll investigate if i can make something approximating your idea tomorrow. My first thought was to steam it, or heat it in some way with some water to be able to bend/push it back into shape because the lump seems pretty solid right now but obviously this is going to undo the gluing of the linings and the top thats just been glued on so is not really a useable option.
It isn't a viable option if the split is along the juncture of the side and linings. Otherwise, it should be a viable option, fitting the repair "patch" between the linings.

Out of curiosity, what method had you planned on using to glue the back on?

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Interestingly I was planning on gluing the side support braces on at this point as I had thought they would be mostly for side rigidity for sound purposes, i didnt realise how structurally handy they could have been had i done that before gluing the top on.
I've never made a guitar with side support braces. I don't consider them necessary, though I understand why people might wish to install them. I've never had a finished guitar I've made had a side split. I'm aware that it does happen, as I've repaired many of them on other instruments.

If one is going to use them, the time to install them is, generally, before affixing top and back.
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  #62  
Old 08-17-2016, 11:14 AM
emmsone emmsone is offline
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Thanks again Charles
I haven't actually come up with a specific method yet but I already know that i can't use the same technique as the back has a radius.
I had thought i could basically invert what i did to glue the top and use the same flexible board i had under the guitar (contouring to the back curve) while i was clamping the top and place that on top of the back and clamp to a thicker board under the guitar.
I was thinking about possibly using spool clamps, but a) i dont have any b) they are expensive to buy and will probably take ages to make and c) i'm actually not convinced these will work well unless the back is trimmed basically almost flush before you even glue it on and i'm not sure i can trim it close enough accurately enough in advance to use this method

Dave
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  #63  
Old 08-17-2016, 08:34 PM
dekutree64 dekutree64 is offline
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Ouch! Sorry to hear about the side crunch. But as Charles says, these things can usually be fixed. Glue is wonderful stuff

Side braces aren't always beneficial. If you do it the easy way (gluing linings first and then adding side braces between them), it leaves a weak point right along the edge of the linings. So you may have just gotten a split there instead of buckling in the middle.

To eliminate the weak point, I glue full height side braces first, and then short lining strips between them. This would almost certainly have saved you. But aside from being more work, there's another catch: Full height side braces must be glued in low humidity. Otherwise when the sides shrink in low humidity later, the braces can pop areas of the soundboard and back joints because their length remains unchanged.

Unbraced sides have the advantage that they can freely expand and contract with humidity, so they're less prone to going concave or convex as the weather changes.

As for how to clamp the back, I use spool clamps, and they are very easy to make if you have a local hardware store that sells long bolts or threaded rod, wing nuts, large dowels, and a roll of cork. Still not super cheap, but much cheaper than buying them pre-made. You can get away with as few as 30 but 35-40 is better.

What I really like about spool clamps is that you can clamp the back on and then tap on the box to get an idea what it will sound like after it's closed up. It will usually be higher pitched and ring longer after it's glued and clamps taken off, because the mass of the clamps makes the frequency lower, and the contact with the edges of the soundboard damps the vibration a bit. But you can still shave braces and re-check with the spool clamps to hear how it changes and help decide when to stop shaving. If you can bring it home where you don't have to pay for shop time, that would be good. You only need a chisel and the spool clamps to work on it, and final voicing is something that shouldn't be rushed.

To deal with the back overhang, set the body on the braced back and trace around it with a pencil. Then use a chisel and block plane to carve the edge of the back close to the line.
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  #64  
Old 08-22-2016, 01:17 PM
emmsone emmsone is offline
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So here is my attempt to fix the buckled side.
What i did was after sanding the outside edge of a block to fit as a caul and clamp that against small block on the inside edge. Before the clamping I added some water to the area needing to be modified a small amount at a time and then used a heat gun on the area and tried to get the clamp on as soon as possible after taking the heat away.
I left the clamp on about 15-20 minutes the first time, and then repeated the process and left the clamp on overnight, i'll see how its done tomorrow. The first attempt took it pretty close to "normal" still not perfect but at least not obvious. Even after the overnight clamping, its unlikely to be absolutely perfect, but it should be much improved and hopefully "good enough"

While waiting for the clamping to take effect the first time I made some headstock routing templates. Two are my own design, and the same shape but one is slotted, one is flat. The third is the "traditional" slot head design that came with the plans I bought. I really like my own slot head design, but i'm leaning towards my standard flat one for this guitar. Ive left the edges of the template deliberately slightly oversized so I can have a very slightly wider neck at the nut if I decide not to go for the typical 43mm and just carve down the small difference with a file/sander/sandpaper if I go with the 43mm

clamping the side "straight" seen from the outside with a shaped caul
Untitled by David Emm, on Flickr

the inside used a straight caul as it was just to give a vertical surface to clamp against from the other side
Untitled by David Emm, on Flickr

Headstock templates
Untitled by David Emm, on Flickr
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  #65  
Old 08-24-2016, 01:01 PM
emmsone emmsone is offline
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So i took a video of my "tap tone" hoping that someone will able to inform me just how shockingly bad and cardboard box-esque (my expected reply) this sounds. Hopefully my iphone has picked up enough detail to inform the informed listener what the situation is really like and how to sort it out? where i need to remove material and how? off the sides of the braces? off the tops of the braces? Since the last images of the internals, the only difference is that I have carved the ends down to pretty much as thin as I can get, they are now barely 1mm thick at their ends.



Before taking this video I trimmed the soundboard flush with the sides and then decided to make a bridge template/tester. The bridge blank I bought is too narrow for the design on the plan I have. I tried to modify it and I kinda like the resulting shape, but I end up with string holes too close to the edge which i don't like. I'm not sure about moving the holes closer to the saddle line, there is currently a 14mm gap to from the centre of the holes to the centre of the saddle line and the string holes are parallel to the saddle line, I guess i could move a the holes few millimetres closer, and i'm thinking about moving the holes parallel to the horizontal front edge of the bridge but I don't know if that will give me issues down the line, the holes are obviously where they are on the original plan for a reason.

Untitled by David Emm, on Flickr
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  #66  
Old 08-25-2016, 02:51 PM
emmsone emmsone is offline
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i'm still hoping the video I posted in my previous post is good enough quality that someone can offer me some required direction on the guitars voicing.


On a side note, I had decided to build some spool clamps instead of buy them, but when the cost for just 30 bolts is upwards of 120 bucks, that plan is out the window, when i clamp the back on I may now have to just use regular clamps and about a million chunks of wood cut up to be protective cauls
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  #67  
Old 08-25-2016, 09:05 PM
charles Tauber charles Tauber is offline
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Quote:
Originally Posted by emmsone View Post
i'm still hoping the video I posted in my previous post is good enough quality that someone can offer me some required direction on the guitars voicing.
I did listen to/watch your video. All I can really say about it is that it sounds "resonant". That's good.

Different people have different approaches to "voicing". There isn't a unified, single approach. Some tune to a specific pitch, others to a certain deflection, others to what response graphs tell them, and so on.

The top changes tone when attached to the sides. The top and side assembly changes when the back is put on.

(As an aside, if building with an outside mold, I glue the back on first, then the top.)

What you can do is to place the assembly down on a table (or your lap) and use your thumbs to flex various parts of the top. The perimeter should be "loose" enough to allow the central portion of the top to move as a unit when the bridge area is pressed with the thumbs. If it isn't sufficiently "loose", you can trim interior bracing and/or thin the top around the perimeter of the lower bout.

Quote:
On a side note, I had decided to build some spool clamps instead of buy them, but when the cost for just 30 bolts is upwards of 120 bucks, that plan is out the window, when i clamp the back on I may now have to just use regular clamps and about a million chunks of wood cut up to be protective cauls
In guitar making, there is no "right" way, only what you can come up with, how much ingenuity you have. For example, instead of bolts, use threaded rod, cut to lengths. That should be much cheaper.

One of the methods I use I learned 30 plus years ago from Grit Laskin. You've put a lot of time into making an outside mold: use it for everything you can. (Such as the clamping cauls to fix your cracked sides.) I'll post some photos of it when I have a chance.
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  #68  
Old 08-26-2016, 02:31 AM
emmsone emmsone is offline
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Originally Posted by charles Tauber View Post
I did listen to/watch your video. All I can really say about it is that it sounds "resonant". That's good.
Thanks Charles.
It does seem to have resonance but the sound seems very "tight" to me and i'm not sure if this is a bad thing, my guess would be that this isn't ideal, but i don't know the answer.

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Originally Posted by charles Tauber View Post
The top changes tone when attached to the sides. The top and side assembly changes when the back is put on.
Yea I noticed this, if i hold the sides while i tap the top, the tone changes and sounds quite dull, a much bigger change than i would have expected.
(As a side point which is just something my brain thinks about, seeing as the guitar would usually be in contact with the guitar player, often on the sides if played sat down, would it not make more sense to make sure the top resonates freely when the sides are being touched? does anybody do this?)

Quote:
Originally Posted by charles Tauber View Post
What you can do is to place the assembly down on a table (or your lap) and use your thumbs to flex various parts of the top. The perimeter should be "loose" enough to allow the central portion of the top to move as a unit when the bridge area is pressed with the thumbs. If it isn't sufficiently "loose", you can trim interior bracing and/or thin the top around the perimeter of the lower bout.
I like this idea, I may have to do this and see how it does, this also might let me "see" better if my thoughts of the top being (too) "tight" are correct or not


Quote:
Originally Posted by charles Tauber View Post
One of the methods I use I learned 30 plus years ago from Grit Laskin. You've put a lot of time into making an outside mold: use it for everything you can. (Such as the clamping cauls to fix your cracked sides.) I'll post some photos of it when I have a chance.
I would like to have been able to use my mould more, but because my original side bending was not a 100% perfect fit, the trickle down effect means that original mistake plus doing a bit of work outside the mould means it doesn't fit any more. Especially the waist bend, which is why i had to hand shape a caul to fit for fixing the side buckle.

If/When i build another guitar, i might have to do something about the mould, I'll need to re-check its dimensions and see if I had made a mistake there and therefore if I can use it again. It may have been my build technique and the mistakes I just mentioned, but the mould seems to have been a lot less helpful than it should have been. It is also SUPER heavy which made moving it or doing anything with the guitar in it very tricky. I definitely picked the wrong material.
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  #69  
Old 08-26-2016, 06:28 AM
charles Tauber charles Tauber is offline
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Quote:
Originally Posted by emmsone View Post
... the mould seems to have been a lot less helpful than it should have been. It is also SUPER heavy which made moving it or doing anything with the guitar in it very tricky. I definitely picked the wrong material.
Being heavy can be a good thing, using it to prevent the body from moving when working on the body in the mold, during operations like planing or sanding the linings and end blocks.

Here is a video that shows one method that I use for clamping tops and backs to the sides when using an outside mold:

https://www.youtube.com/watch?v=KSXmP_eD8c4

Note the thud-like sound of the body at the end of the video. That is the sound - at least on my guitars - of a too-tight (stiff) top and back. The next step, for this particular instrument, not shown in the video, is to selectively thin the top and back. The zircote back was too thick, generally, as well as too thick around the edges. The top just needed thinning around the edges of the lower bout. After having done that, it sounds like it'll be a winner. There are other methods for obtaining a desired balance of weight and stiffness, but that is one that I use.

I initially learned to build steel string guitars face-down on a slotted work board in the Spanish construction method. In that construction, the top is laid face-down on the board and the sides attached above it, simplifying gluing of the top to sides. The back can be clamped on using large rubber bands that attach to the slots in the work board, or to screws sticking out from the perimeter of the board.

I still use the method - and parts thereof - for various things. In some ways, it can be much more flexible than using an outside mold, particularly if one is new to guitar making.
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  #70  
Old 08-26-2016, 07:39 AM
printer2 printer2 is offline
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Hope no one minds my asking Charles, checked out your planing the back vid. What angle is that plane?
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  #71  
Old 08-26-2016, 09:29 AM
charles Tauber charles Tauber is offline
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Hope no one minds my asking Charles, checked out your planing the back vid. What angle is that plane?
The blade is honed at 30 degrees, the bedding angle is 12 degrees, a low angle jack plane. This is the plane: https://www.lie-nielsen.com/product/...lane?node=4065.

In the video, a LN 4-1/2 smoothing plane is partially in view to the left (as viewed). It is also honed at 30 degrees, though has a 50 degree bedding angle. Both work just fine on the zircote I'm planing: I used the 4-1/2 for the sides, as I was too lazy to sharpen the low angle jack plane again and the 4-1/2 was already sharpened. (My thickness sander just hates zircote. Zircote doesn't much like my thickness sander either - it just burns. Hence, hand planing.)

For most woods, I find the choice of angles is less important than to have the plane well setup, well sharpened and the throat set appropriately.
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  #72  
Old 08-26-2016, 11:48 AM
emmsone emmsone is offline
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After reading what Charles said in his previous reply and having re-read some other bits and pieces in my build book, I went back again today and took a little more wood off the sides of the lower legs of the X braces and the 2 long lower braces, essentially making them all more triangular and thinner but the same height. This has "lowered" the pitch of the tap tone slightly, and perhaps now it sounds a bit less "too tight" (but still pretty tight) and it still resonates fairly well, but even with that material removal the top deflection is still practically zero. I was having to push fairly hard to get any if at all. I now realise to fix this I should have lowered the bracing height and left the bracing the same width. I hope its not too late and I haven't removed too much that any further lowering the brace height to allow additional deflection will just kill it.

You can see the lack of deflection and "new" tap tone in this new video



the pictures below show the current state and shape of the bracing as in todays video.
It was previously mentioned that I could/should install some additional bracing around the soundhole. I had/have forgotten about that until I was writing this right now.

Untitled by David Emm, on Flickr

Untitled by David Emm, on Flickr

Untitled by David Emm, on Flickr
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  #73  
Old 08-26-2016, 04:03 PM
Quickstep192 Quickstep192 is offline
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Although know your pictures are intended to show you progress with your braces, it also looks like you resolved the problem with the sides. Am I seeing that correctly?
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  #74  
Old 08-27-2016, 05:36 AM
dekutree64 dekutree64 is offline
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Quote:
Yea I noticed this, if i hold the sides while i tap the top, the tone changes and sounds quite dull, a much bigger change than i would have expected.
(As a side point which is just something my brain thinks about, seeing as the guitar would usually be in contact with the guitar player, often on the sides if played sat down, would it not make more sense to make sure the top resonates freely when the sides are being touched? does anybody do this?)
Don't worry about it. It's not so picky after the back is on.
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Originally Posted by emmsone View Post
I now realise to fix this I should have lowered the bracing height and left the bracing the same width. I hope its not too late and I haven't removed too much that any further lowering the brace height to allow additional deflection will just kill it.
Triangular braces are almost always a good thing. Short fat braces are heavier for the same stiffness, and in most cases lighter is better. If it still feels really stiff, then it's unlikely that you've gone too far yet.

However, it is good that you haven't triangulated the scooped part of the X intersection, since that's already low. Triangular profile would save weight for the same stiffness there as well, but it would need to be taller to start with.

The current tap tone sounds pretty good, but probably can go a bit further. I'd recommend leaving everything around and above the X intersection alone (aside from adding the soundhole braces), and taking a lot of material off the lower half of the lower tone bar, where it comes close to the tail block. The other tone bar and lower X legs can probably come down a little bit, but don't overdo it. I think you're out of cardboard box territory already, and you can shave those through the soundhole with a finger plane after the box is closed and you can hear the real tap tone (or even after you have strings on it). The brace ends are the main thing you lose access to after closing the box. Also the bridge plate, which still looks rather meaty to me.
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  #75  
Old 08-27-2016, 07:16 AM
redir redir is offline
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FWIW I almost always thin out the perimeter of the top along the lower bout to loosen it up. I don't think tapping an unfinished box is very meaning full. It's hardly meaningful to tap a finished box. What it will tell you however is if it is acoustically dead or has a nice ring to it. If it's thuddy then it's most likely over braced.

What is the purpose of the design of your X-Brace? In particular the scalloped out section at the X junction. I've never seen that before. As was mentioned before and before it's too late you will really want to add some sound hole braces.

Also I like that lining. I'm not one who really cares about the inside of a guitar but those linings look cool.
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