Pair of Mandolins in Engelmann / River Oak - Osmo finish

[Bob_H]

Good afternoon all

I'm working on a pair of flat top (3m induced curve), h-braced mandolins in River Oak and Engelmann Spruce.

I have the tops braced and attached to the ribs, and the back braced. Working on the neck is coming up.

I am looking at finishing at least one with Osmo Polyx-oil. I know that some forum members have used it to finish steel string acoustics, and had a few questions:

1. Would there be any benefit in pore filling under Osmo? If so, what would be most appropriate? Epoxy? I have read some expressed reservations about filling under Osmo, but would appreciate any additional input.

2. Any observations, or suggestions, in regard to applying Osmo?

[kiwigeo]

I tried to attach some images of the project, but received the following error "Sorry, the board attachment quota has been reached."

Try again Bob..and let me know if you have further problems.

[Bob_H]

I tried to attach some images of the project, but received the following error "Sorry, the board attachment quota has been reached."

Try again Bob..and let me know if you have further problems.

Thanks Martin - original post amended successfully

[kiwigeo]

Flash looking Stewmac clamps Bob. Did you come into an inheritance recently?

[Bob_H]

Flash looking Stewmac clamps Bob. Did you come into an inheritance recently?

I must admit to giving in to temptation after two frustrating failures at building my own spool clamps. They are very useful in applying pressure evenly around the body of the instrument while it is held in the building form.

[WilliamDavidReynolds]

IMG_3826.jpeg

Those go bars look like the ones I found, there is a place called Tractor Supply in USA which sells these 3/8” fiberglass dowels, I did some testing with them before building the new Gobar station, a drop ceiling reinforced and new work bench so I can work on two back and top at same time. The testing I did was to reduce the arch as much as possible as in my tests I found that them being as straight as possible without falling, and super torqued to the point where they would create lateral forces if not perfectly plumb, but still making bracing wanna flip over,, every height I checked using a floor scale was 25 pounds each. I checked every height with up to six bars and they all consistently pushed/clamped at 25 pounds, so six was 150ish,, with in a few pounds and never less.

Where did you source yours?

Those mandolins look great too!

[Bob_H]

IMG_3826.jpeg

Those go bars look like the ones I found, there is a place called Tractor Supply in USA which sells these 3/8” fiberglass dowels, I did some testing with them before building the new Gobar station, a drop ceiling reinforced and new work bench so I can work on two back and top at same time. The testing I did was to reduce the arch as much as possible as in my tests I found that them being as straight as possible without falling, and super torqued to the point where they would create lateral forces if not perfectly plumb, but still making bracing wanna flip over,, every height I checked using a floor scale was 25 pounds each. I checked every height with up to six bars and they all consistently pushed/clamped at 25 pounds, so six was 150ish,, with in a few pounds and never less.

Where did you source yours?

Those mandolins look great too!

Thanks:) I can't recall where I purchased the go bars, but I remember it was on-line, Australian and specialised in kite-making. You took a much more scientific approach than I did, but I'm happy with the outcome. I usually use a floating base in the go bar deck, often a radius dish, and just jack up the height with magazines until I get the tension I need. I have to be careful sometimes to balance the bars to counteract lateral forces, and to stop pieces moving around!

[kiwigeo]

I bought a set of fancy fibreglass rods from LMI but have never used them....I use lengths of 8-10mm diameter hoop pine as my go bars.

[WilliamDavidReynolds]

I bought a set of fancy fibreglass rods from LMI but have never used them....I use lengths of 8-10mm diameter hoop pine as my go bars.

I just realized after reading your comment the last time I was at hardware store and bought some 1/4” oak to pull a hole so I can redrill the same hole 1/8” back,, I remember the rods being a dollar. I might have to go buy 30 of those