Sarah's Mandolin

[Norris]

That's looking fantastic

[Prostheta]

I know....that's an incredibly attractive little project you've got going on Scott.

[ScottR]

Thanks guys!

Something about the F-5, the elegance and balance of the design I suppose, has always attracted my eye.

SR

[ScottR]

As I said at the beginning of this thread I know diddly squat about mandolins. While that is no longer exactly true, there is one piece of information that I've been missing: how is the bridge attached? The two sources I've been using actually say nothing on the subject.....like it is common knowledge, or a given or something. Googling it leads me to believe that only string tension holds it in place and you actually move the entire bridge to intonate. Which would mean you would need to intonate at every string change,,,,,,although I suppose you could avoid that by replacing one string at a time.

Matt, didn't you say you have three mandolins? Are your bridges only held in place by string tension?

SR

[mattharris75]

Yep, floating bridge. String tension only.  Replace one string at a time so you don't have to re-set the bridge.

[ScottR]

Well those little instruments are a wonder aren't they?

Thanks Matt.

Do you have to take care not to move them accidentally, or does then tension hold them firmly enough that it takes a concentrated effort to move them?

SR

[psikoT]

11 minutes ago, ScottR said:

Do you have to take care not to move them accidentally, or does then tension hold them firmly enough that it takes a concentrated effort to move them?

No idea about mandolins, but strings tension keeps the bridge firmly in place in my cigarbox guitar, with only four strings.

EDIT.- Also in my violin!

[ScottR]

On 5/10/2016 at 1:20 PM, psikoT said:

No idea about mandolins, but strings tension keeps the bridge firmly in place in my cigarbox guitar, with only four strings.

EDIT.- Also in my violin!

Violins have floating bridges too? I should not be surprised as there are a number of construction similarities between the mandolin and violin. I had seen the term floating bridge, but I guess I thought it references the way the saddle portion of the bridge rest on the height adjustment posts. That is definitely held in place with string tension......but I had no idea the entire bridge was.

SR

[Prostheta]

That's one of two things I keep reminding myself; that to a beginner, nothing is obvious. The second is that everybody at some point - no matter how successful they are now - was a beginner at one point also.

[ScottR]

Those are very good points Carl. Everyone in a position of teaching or training another person a skill needs to remind themselves of that maybe once a day. I tried to find a way to re-state that but couldn't find anything better. I've got some guys around here I need to have start repeating that to themselves........

SR

[psikoT]

12 hours ago, ScottR said:

Violin's have floating bridges too? I should not be surprised as there are a number of construction similarities between the mandolin and violin. I had seen the term floating bridge, but I guess I thought it references the way the saddle portion of the bridge rest on the height adjustment posts. That is definitely held in place with string tension......but I had no idea the entire bridge was.

SR

 

I don't know about floating bridges (I thought that term was only referred to tremolos) but I find this:

quite similar to this:

And I thought your question was basically if the bridge has to be glued to the body, in order to prevent lateral movement... sorry if I misunderstood, I'm just an observer here. Just wanted to point that string tension indeed hold in place the bridge, there are some kgs of pressure there.

[Prostheta]

I suppose that you could glue it if you really wanted, however whether it was or not, any pressure that would tip it either direction wouldn't be stopped by a little bit of glue. The wood would fail pretty sharpish. It's just an exercise in producing a good set of mating faces for maximum coupling.

[ScottR]

5 hours ago, psikoT said:

And I thought your question was basically if the bridge has to be glued to the body, in order to prevent lateral movement... sorry if I misunderstood, I'm just an observer here. Just wanted to point that string tension indeed hold in place the bridge, there are some kgs of pressure there.

That was indeed my question, except I would think movement toward or away from the nut would be more likely than side to side. Your answer was both on point and helped me understand more about the bridges, so thanks for that.

SR

[ScottR]

5 hours ago, Prostheta said:

It's just an exercise in producing a good set of mating faces for maximum coupling.

I believe I've got that part in good shape, certainly better than the pic PsikoT posted. I'll give it a couple of tweaks after it's lacquered to insure it's still a good mate.

SR

[psikoT]

1 hour ago, ScottR said:

I believe I've got that part in good shape, certainly better than the pic PsikoT posted. I'll give it a couple of tweaks after it's lacquered to insure it's still a good mate.

I also wanted to ask about that, but I forgot... Is that separation at the edges a product of the string pressure?

[Prostheta]

If there's any potential movement then the bridge hasn't been set in balance properly. 

[ScottR]

46 minutes ago, psikoT said:

I also wanted to ask about that, but I forgot... Is that separation at the edges a product of the string pressure?

If it is, it means the arch top has been carved too thin and is failing under the string pressure....and that instrument is junk. What it probably is- is a bridge that has not been fitted to the top properly. It needs another round of sandpaper laid on the top in that position and sanded gently until it is a perfect match for the curvature of the top in that location.

SR

[mattharris75]

All mandolin family (and violin family too for that matter) instruments are considered to be 'floating bridge' instruments. 

An 'average' mandolin is going to have 50 or so pounds of downward pressure on the bridge, so that sucker's not going anywhere!

There are a lot of factors, the biggest being string tension and break angle over the bridge, but if you want to calculate the exact amount of downward pressure there  are calculators out there to do it. I know luthier Andrew Mowry has one online. 

And, not only do violins and mandolins have a lot of construction similarities, but they have the exact same tuning, GDAE. For two instruments with the same range they actually complement each other really well, in my opinion. 

[Andyjr1515]

Just to finish the list...traditional arch top jazz guitars are also often floating bridge.  I'm pretty sure the Hofner 'Beatles' violin bass is also floating.

Ive worked on floating bridges a number of times and, in terms of intonation, they have their advantages against a fixed saddle type of arrangement.  If the intonation is out a bit, you just slacken the strings off a bit and give the bridge a nudge forwards or backwards a bit.  Darn sight easier than filing compensation angles on a bone saddle!

[mattharris75]

And don't forget about banjos! (although some folks would like to)

[Andyjr1515]

1 hour ago, mattharris75 said:

And don't forget about banjos! (although some folks would like to)

I've paid a lot of therapy fees to help me forget about banjos....and NOW I'VE REMEMBERED THEM AGAIN!!!!!!

 

[Prostheta]

12 hours ago, mattharris75 said:

And don't forget about banjos! (although some folks would like to)

Yeah cheers Matt. I spat coffee all over my monitor now thanks to your PTSD trigger.

[SIMpleONe89]

What's wrong with banjos?

[Prostheta]

Just. Stop. It.

Name three things that are right with banjos. 

[Aakoo]

I find this topic very inspiring. I think I might have to do an mandolin next winter!

Lovely work, and more pics please!