Bass Bar Blues (I've got them)


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Ok, I officially hate fitting bass bars. I'm having a heck of a time getting this done right and could use some advice here.

I trimmed a piece of spruce to the requisite 5.5mm at 270mm in length. I then did all my measurements and marked clearly where it should go. I then clamped it into place (untrimmed yet) and used a washer and pencil to trace the arc. I then trimmed the bar to the arc marking and then reclamped it to the plate. Now, I took some small blocks of lining and lightly glued them side-to-side around the bass bar in six places in order to keep the lateral placement exact while I chalk fitted it.

So far so good. Now, the chalk fitting was hard for me. Perhaps it is because the top is so dramatically arched, or more likely, it may be because I'm a rank amateur at this. Anyway, I toiled over the next two hours putting the bass bar on the chalk, scooting it length wise a bit, and then flipping it over to trim off the chalk marks with my knife. It seemed that each time I got close to a decent fit, it would fine-tune it a bit only to find that I was way off again. I tried using planes, sanding blocks, scrapers, and knives to get the fit right and never really got a perfect fit. There was always a few paper-thick gaps here and there. Often, I would get a perfect fit on the inside edge, but see lots of gaps on the other side. I felt like it was getting rounded, but could never locate the problem. Anyway, after getting it this far several times, I decided say it was "good enough" and begin gluing.

Well, naturally, I had tons of problems gluing as it would tend to slide down with pressure applied from the clamps. I finally got it to stay, but those gaps looked even worse. So, rather than let the glue set and always wonder if I did it well enough, I pulled off the bar, cleaned it and decided to seek better advice.

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If there's one single trick to fitting bass bars, it's to never cut without being absolutely sure that you are cutting only a place that touches. If I see a consistent problem in one place, I'll put a pencil mark on that point on the underside, to make sure that even if I see chalk there, I won't cut there. Keeping the chalk minimal helps avoid mis-marks. The best chalk for the job is Christian chalk-talk white chalk--Google it. Thought it used to be a widespread item in art stores, there are only one or two sources for these 1x1x3" very soft chalk sticks. Unlike other sticks, this chalk has no oils and no fillers. You can easily saw it into quarters--long thin sticks.

Once you cut one spot too deeply, you have to trim the most of the whole rest of the bar down that much, just to get back to where you were when you made the mistake so DON'T MAKE MISTAKES!!!!

It may look like I'm working really slowly because I'll only cut a tiny spot at a time, and sometimes check twice to make sure I'm not misreading something, but I can fit a bar in a new violin in about 15 minutes. The key is never, ever cutting wrong, not working quickly.

You will get more precision with a small finger plane--I use the smallest flat Ibex--with the blade sharpened for the minimal clearance underneath, and the mouth shimmed up small.

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After doing many bass bars, I kind of enjoy doing them. As Michael said, don't remove the wrong wood. It compounds the difficulty if you have to go back and re-trim the whole bar. For your alignment cleats- I only use about 4, on the "downhill side" only. Did you remove the cleats before gluing? If you did, that would explain the bar sliding during gluing. Leave the temporary cleats in place until the bar is glued and clamped in place. Remove them during the wet glue cleanup step. What kind of clamps are you using to glue the bar?

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I use nine clamps, evenly spaced. Notice the lines on the bar where every clamp is--these give me measuring marks to know where to cut and where not when I flip the bar over. There's a strip of heavy matte board under to spread the pressure a bit and keep the clamps from denting the top (the barely-visible red spring clamp at each end holds this). Notice how the clamps alternate sides, so that the weight of them all on one side doesn't distort the top, since it's vulnerable while wet. That's also why I try to scrape off glue squeeze out rather than washing it with a lot of water, getting the whole top wet. If you work as dry as possible, you'll have much less problem with tops warping, especially at the ends of the bar.

barclamped.jpg

I also clip down the upper wing so that it doesn't move under pressure, which makes fitting easier:

wingclampinuse.jpg

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I've developed a slightly different way of fitting a bass bar which may work for you. I fit a notched 'tower' at each end of the bar and the ends of the bar are pointed to fit in the notch. This does not allow the bar to go anywhere but one place. Makes fitting and gluing the bar more predictable and quicker (for me)

(sorry for the poor photo quality)

Oded

post-95-0-76813900-1294674639_thumb.jpg

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Guest EdwardPA

Hello Michael

That's a very efficient setup you have there. I remember a while back when you first posted that image and I have been wanting to make an aluminum plate like yours. Can you tell me what thickness aluminum you used for the plate.

Thanks and regards

Ed

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Did you use some sort of frame to immobilize the rim of the top? Michael's first picture shows the outside edge clamped in an aluminum frame. You can also make one out of plywood. Without something like this, the whole top can flex and bend, so the surface that you're trying to fit the bar to keeps changing.

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I haven't made my own frames. That one was sawn out by someone at B&F, a long time ago, and it's two layers of 2mm sheet aluminum sawed out on a bandsaw (with access cuts for the center hole at different spots) and glued together. I now have some newer ones that Andres got--he had a batch CNCed out by someone on the web.

It's possible to fit a bar without a frame, but it's like hitting a moving target, since the fit depends on the flex of the top at any instant, as Brad says. You could possibly make one out of 1/4" tempered masonite, and some people use 1/2" plywood. I wonder how six or so layers of Formica band sawed out individually and then glued up in a stack would work. . . there are a lot of possibilities.

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I too was looking for this photo...Michael I can't visualize the piece of matte board that you are using with the red spring clamp...do you mean the board lays on top of the bar or the underneath the top to protect it from the clamps?...can you please explain this alittle more...I plan to make a bassbar fixture and I like the perimeter plate that you made...Thanks

-Ernie

Michael...nevermind I think I understand what you mean now...the matte board is placed under the plate to protect the top from being dented right?...Still working on my first cup-o-joe...ho hum... :rolleyes:

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You will get more precision with a small finger plane--I use the smallest flat Ibex--with the blade sharpened for the minimal clearance underneath, and the mouth shimmed up small.

Michael, Do you only use the small flat Ibex for this work? No knives or files?

I've developed a slightly different way of fitting a bass bar which may work for you. I fit a notched 'tower' at each end of the bar and the ends of the bar are pointed to fit in the notch. This does not allow the bar to go anywhere but one place. Makes fitting and gluing the bar more predictable and quicker (for me)

Oded

Oded, very interesting idea. Do you fit a notched post at both end or only one? If only one, how do you stabilize the bar laterally? If you use two posts at either end, then I'm curious how you move the bar in order to pick up the chalk.

That brings me to my next question for everyone: If you have to move the part being fitted in order to pick up chalk, how is it possible have a perfect fit in only one position?

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I have a notched post at both ends. I also recess the underside of the pointy part so it has no contact with the top (not need to fit it) At first I have it a bit loose, then, as I get close to a final fit I insert some card stock between the point and the notch to make it a tight fit. To get a chalk imprint I tap all along the the top of the bar. One reason I like this method is that I have an uninterrupted view of the entire length of the bar. It takes a bit longer to fit the notched posts but in the end it saves much time and hassle. I save the posts and with small modifications can reuse them.

Oded

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or the underneath the top to protect it from the clamps?..

On new building the bass bar should be over sized/ so no padding is needed there.

1/ It's a strip about 1" wide, running the length of the top, between outside of the top and the clamps.

2/ Say what??????? Or are you talking about the height, where the tops of the clamps go?

As Oded says, it doesn't take much to get a print. I doubt I move the bar more than 2mm, but if there's a step in the top--the edge of a patch or something, use your head and don't believe what you see at that spot. Fitting the bar is more head than hands, I think.

Yes, I use only a tiny plane adjusted to remove almost nothing, except for the beginning, where I can get pretty close fast, with a knife. Files tend to take off too broad of an area to be useful.

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1/ It's a strip about 1" wide, running the length of the top, between outside of the top and the clamps.

2/ Say what??????? Or are you talking about the height, where the tops of the clamps go?

Michael /sorry for the hasty post! For a guy like you this has to be a lot like hearding turtles!thanks for your expert input and vigalance.I've only had one semester of formal training.

1)yes I'm aware that the strip goes on the out side of the plate.I use a thin piece of wood >1mm thick.

2) Yes I was refering to the starting height of the bass bar /I was taught to use 15 -18 mm as a width/ after fitting/ also to campher the top edges for "clothpin" type clamps)

I was also taught to wipe any remaining chalk after trimming and before re marking with chalk . Also to use a small fine flat file and just float it once.... or maybee twice down the lenght of the bar / as a last touch before glueing

I'm interested in sprung bars/ pro vs con. I was taught to do sprung with out the yoke as a way of countering the tension of the strings/ so I'm looking for any disscution on this issue.not much in a web search.Anyone feeling up to it. Just curious! thanks

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I made this jig, (from this design picture #4 http://www.thestrad.com/pdfs/StradArticle_%201577-2010-6-25.pdf ) a few years ago and I couldn't believe how much easier it made installing a bass bar.

I've since made one for viola and cello and they work beautifully. I also like the fact that there are no cleats and cleat remnants to deal with after glueing.

It is well worth the time it took to make. After a little practice I can fit a bass bar in under ten minutes. Thanks Sharon Que!

(I REALLY like this jig!)

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I made this jig, (from this design picture #4 http://www.thestrad.com/pdfs/StradArticle_%201577-2010-6-25.pdf ) a few years ago and I couldn't believe how much easier it made installing a bass bar.

I've since made one for viola and cello and they work beautifully. I also like the fact that there are no cleats and cleat remnants to deal with after glueing.

It is well worth the time it took to make. After a little practice I can fit a bass bar in under ten minutes. Thanks Sharon Que!

(I REALLY like this jig!)

Cool...I was going to ask others to post pictures of their jigs/fixtures used to glue in bassbars...I like this one...care to post a picture of yours?...I have'nt built one yet...some other examples would be helpful.

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I spring the bar according to the player. If it's for someone who pushes, I give him something to push against, if not, then not. Very few players are really heavy pushers; usually I have a bit of spring, not too much. Maybe 1mm.

Thanks/ Michael/ for your insight.

arglebargle / I can't open the site for some reason would you please describe it If/ you could be so kind?

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Cool...I was going to ask others to post pictures of their jigs/fixtures used to glue in bassbars...I like this one...care to post a picture of yours?...I have'nt built one yet...some other examples would be helpful.

Yeah, it's a great design.

Mine honestly looks pretty much just like the one pictured. I put a little more curve on the support posts toallow the bar to move more when establishing the bar position. Other then that, if it ain't broke...

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It seems in this business, you spend more time building jigs than anything else. :)I might give it a shot though if it makes things easier. Is the clear plastic necessary, or could I use a hardwood?

I ordered the 8mm flat soled Ibex and hope it will make the difference. No more knives!

Just for grins, what would the difference in sound be if you had a bar that was perfectly fit vs. one that was about 80% (say with a small paper-sized gap about 2" long on the f-hole side)

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