Small increase to an instrument's scale length?

[Bernie Daniel]

Just a theoretical question.

I am converting an arch top guitar to a mandocello. I took the fretboard off to slim it down to ideal mandocello width. But instead of that I could just buy/or make a NEW fretboard that is the width that I want.

Buy if I did go with a new board, could I also consider moving the bridge back 1 inch and thus create an instrument with a 26" scale instead of 25"? This would put more tension on the C-course strings.

I have calculated the inter-fret distances and they are minimally affected (nut to fret #1 equals 1.403" versus 1.459" respectively).

But I wonder if moving and re-fitting the bridge back as much as 1" would have major impacts to the tone/projection or would be ill-advised as regards the integrity of the top board?

I assume someone must have tried already -- if so what happened? Thanks.

[Audio Artillery]

Are you sure it's a 25" scale? Most acoustics are 25.5". Harmony's archtops are I think 25.25", and that Vega of yours might be Harmony-built (not sure).

Anyways, I have played a Gibson (~24.75") a couple times and now have the one I built (25.5"). I think the extra schmidge of scale length is worth it to tighten the C strings up. I doubt it's worth sourcing a new fretboard over though, especially if you're already 1/2" higher than the "standard" Gibson scale. Also, it's not like a new fretboard just drops onto your neck, you will need to shape it to match, obviously.

The 25.5" scale on mine is workable but I'm still adjusting to the reach. If I had infinite amount of time I would build necks with smaller and smaller scales to find the one that is just stiff enough. The difficulty in playing with the long scale cannot be underestimated, IMHO.

As far as moving your bridge back 1"... as long as you're still on the peak of the top, roughly, it seems ok to me. The parallel bracing probably doesn't care much where the bridge is placed.

[MikeEdgerton]

If his Vega was Harmony built there will most likely be a Harmony model stamp and date stamp inside. I didn't take it for a Harmony guitar but I've been wrong before.

[Bernie Daniel]

Are you sure it's a 25" scale? Most acoustics are 25.5". Harmony's archtops are I think 25.25", and that Vega of yours might be Harmony-built (not sure).

Anyways, I have played a Gibson (~24.75") a couple times and now have the one I built (25.5"). I think the extra schmidge of scale length is worth it to tighten the C strings up. I doubt it's worth sourcing a new fretboard over though, especially if you're already 1/2" higher than the "standard" Gibson scale. Also, it's not like a new fretboard just drops onto your neck, you will need to shape it to match, obviously.

The 25.5" scale on mine is workable but I'm still adjusting to the reach. If I had infinite amount of time I would build necks with smaller and smaller scales to find the one that is just stiff enough. The difficulty in playing with the long scale cannot be underestimated, IMHO.

As far as moving your bridge back 1"... as long as you're still on the peak of the top, roughly, it seems ok to me. The parallel bracing probably doesn't care much where the bridge is placed.

If his Vega was Harmony built there will most likely be a Harmony model stamp and date stamp inside. I didn't take it for a Harmony guitar but I've been wrong before.

Guys, thanks!

Yes, as you both suggest it is a Vega jumbo arch top guitar (17" lower bout) -- I did not see any Harmony markings but the 25" scale may indicate they had a "hand" in it now that you mention it -- had not thought of that. But now that I have the strings and fretboard off I'll look around inside with a mirror -- I have a good one with an LED on it.

I guess by "Harmony stamp" you just mean the purple or black indelible ink number/model code? If it is there it was not obvious -- I have three old Harmony arch tops around here somewhere so I know what they look like -- but I did not notice anything like that. But I'll look deeper.

About the "difficulty"!!!

The Epiphone archtop that I converted earlier this year also has the 25.5" scale and the 1 11/16" guitar nut. Now, even as mandocellos go this is a monster to play -- 6 months on it have really stretched my left hand and I can reach frets and make chord formations that I could not have imagined months ago -- so that is good in one sense.

However, in another you pay a price -- I have a lot more of those little random "stabs" of pain; cramps and stiffness in that hand (generally attributed to old age) now than before. The upside is do an hour on that mandocello and a mandolin feels like a 1/2 size fiddle.

So that is why I am going for a 1.5" nut on this one. So from what you suggest I should be able do the longer 26" scale.

But oddly enough about an hour after I wrote the OP I had a chance to examine and play a friend's plectum banjo with a 26+ inch scale -- so I am going to think long and hard about this scale length again.

I might just end up leaving the scale length alone after all and just slim down the fretboard. The Gibson mandocello design (1.5" @ nut and ~2.0" @ 12th) is much easier to play -- so I think they must have researched it out a lot --way back when.

Thanks again for the advice.

[DerTiefster]

Bernie, Is there some reason you can't check out the effect of string tension by moving the bridge back to the scale you want to have and then just listening to the open strings? Seems like that would be a simple and zero-cost test of the longer scale on the lowest notes available on the mandocello. You don't get a chance to check out any effect on your hands of the greater fret spacing, but that is something you can test on the banjo you mentioned.

[Jake Wildwood]

I'm hoping that while you're doing this mandocello mod you're also reinforcing the neck somehow? Adding a truss/CF rods/etc.?

Mandocello string tension is a lot higher than standard guitar tension at a similar scale, and going to 26" should actually mean using much lighter strings. FYI, 20-22w strings for the A course would tend to be close to snapping tension on a 26" length. Heck, even regular guitar wound Gs have a hard time at 26" -- I mean for longevity's sake. I'd suggest using plain 15-16s at that scale.

[Bernie Daniel]

I'm hoping that while you're doing this mandocello mod you're also reinforcing the neck somehow? Adding a truss/CF rods/etc.?

Mandocello string tension is a lot higher than standard guitar tension at a similar scale, and going to 26" should actually mean using much lighter strings. FYI, 20-22w strings for the A course would tend to be close to snapping tension on a 26" length. Heck, even regular guitar wound Gs have a hard time at 26" -- I mean for longevity's sake. I'd suggest using plain 15-16s at that scale.

Thanks for the comments help always appreciated!

I've done several of these conversions now hopefully improving each time -- here is my last one for your amusement!

I do worry about the increased down force with mandocello arrangement -- I guess roughly twice as much? For example guitar = 200 pounds total string tension vs. mandocello ~ 300 lbs? If you assume a break over angles of 15 degrees this amounts to 40 versus 80 lbs down force on the bridge base? (I really don't know the best way to accurately measure that angle -- maybe 15 degrees is too high?)

This guitar does have a truss but it is the older single action style I am taking it over to an experience guitar shop man this week to have him consider whether it should have the modern style double action truss. This was suggested by Big Joe earlier.

The idea with the longer mandocello scale is to get more tension on the C-course as many mandocellists find them to be "sloppy". I guess the downside is you then have to accept more tension on the other courses as well.

I am leaning now to do exactly the opposite of what I suggested in the OP and that is leave it at 25" scale -- and make a new mandocello fret board with a a treble extension.

Thanks for the thoughts.