Bass from Space setup

[Borderfort]

I answered another thread in the EUB forum- but I'm posting my big question here, too, for visibility:

I am setting up an EUB from Planet Violin for a customer.

I placed the soundpost in the usual position, but this thing has an absolutely flat top like a guitar and no bass bar, so the top tended to bend in on the bass side.

The obvious solution I came up with is to relocate the SP under the Centerline of the bridge.

Seems like this would equalise the pressure on the two parts of the pickup under the bridge feet, as well.

Has anyone encountered this on one of these instruments or something similar?

[toman]

A soundpost on an instrument with a flat top sounds to me like a recipe for cracks and sinkage all over the place. The more I think about it, the more my head hurts...

[Borderfort]

I agree.

I wouldn't want one like this, but I have to find a practical solution.

There is a sort of 'shoe' for the pickup and bridge feet. I haven't looked at it carefully, but I doubt it stiffened the top much.

The top is thicker than an arched top- it wasn't bending under the feet at all- the bass side just bent a mm or two- enough to lower the action enough to make it buzz.

I found this about 2:30 AM last night; I'll be back over there later to read the inside for post scuffs and get some measurements.

[arnoldschnitzer]

How about a soundpost under each of the bridge feet?

[Borderfort]

I thought about that. I may suggest it to the owner.
It was just brought in because it arrived with the sound post down and the bridge was obviously high.
I haven't pursued any of the obvious fixes- add internal bracing like a guitar, add at least a soundpost, or add something unique like local stiffening.

I relocated the sound post last night- didn't cure it entirely. The upper wings of the f-holes are still depressed about 3mm, but now at least it's bilateral!

[TheSuzie]

Since it is mostly an electric instrument, how about a block that is about the size of the shoe that goes from under the shoe to the inside of the back. The larger the area, the less chance of everything punching through the back. Semi hollow guitars many times are solid all the way along the center and still retain some flavor of the acoustic style instrument. I vote for a block or blocks, as large as you can slip through the F holes. My feeling is that without the bass bar, that instrument needs to spread the load of the bridge as much as possible. I do have totally hollow archtop guitars that have stood up for many decades but the tops are much smaller and well arched which adds a lot of strength - they dont shift at all when string pressure is applied.

[TheSuzie]

Just wondering if you ever found a satisfactory solution to this setup issue.

Peace,
S