A5 top

[Tom Hemeon]

I am building a Gibson A5. Why is an A5 top cut short at the neck end and then a filler piece glued in where the top would have been. Also what is the purpose of the small ears on either side of the filler piece adjacent to the finger board extension block.

[sunburst]

Are you working for Gibson?

Those features that you are asking about are vestiges from Orville Gibson's early designs. He made the back, sides and neck from a glued-up piece of wood (though he thought that it would be best if the whole thing was carved from a solid piece of wood). That meant that, in order for the fingerboard surface of the neck to be high enough for the fingerboard to extend out onto the top surface, the top had to be fitted into a notch.

As construction, in stages, moved toward more production-friendly multi-piece designs, that feature was kept, and with a dovetail neck joint, there needed to be something to fill the gaps to each side.

[fscotte]

If youre elevating the fingerboard, youll need to find a way to make the neck area strong enough to support it. Others have tried different methods, but I find the traditional Loar method to be aesthetically pleasing, and strong as well.

That whole area there is called the riser block, and the top is cut short to allow the maple riser block insert. You wouldnt want to use spruce for the riser block.

[Tom Hemeon]

Thanks John
No, I am using the Georgia Luthier Supply A5 Style Mandolin full size drawings which appear to match the Gibson A5 pics that I scaled.

[jim simpson]

In this illustration, you can see the uncarved riser block and fingerboard extension.

[fscotte]

There's a significant amount of stress on that riser block.