The Ultimate Bluegrass Mandolin Construction Manual
Reader's Questions & Comments
I have received some interesting questions and comments from readers regarding various aspects of the book, and I thought other readers might benefit from my responses.
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Q: Are your drawings of the F5 f-holes the same size, shape, and location as those on a real Loar-signed mandolin?
A: The measurements for our drawings were taken directly from original Loar-signed F5 mandolins. And, a good many of the drawings were based on Loar's personal F5. As to soundhole shape, here is our soundboard drawing, cut to shape, with the f-hole cut out, and the drawing laid on top of Loar's F5 mandolin. Other than minor dings along the edges of the instrument's f-hole, the Drawing and the F5 match precisely. (Of the four sets of f-holes on page 84 of The Ultimate Bluegrass Mandolin Construction Manual, the bottom left set was drawn from Monroe's F5 mandolin.) (Likewise, a cutout of the body shape from our Drawings, when laid on the backboard of an original F5, matches perfectly to the body shape of the F5 mandolin.)
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Q: Didn't the original F5 mandolins use a 13-7/8" scale length?
A: While some builders are using 13-7/8" today, the original F5s (as well as Gibson's A- and other F- models) used a 13-15/16" scale. Here's a reproduction of the original F5 promotional piece with a reference to the advertised string scale. In addition, measurements of the original string scale verify this. (As a courtesy to luthiers who want to use other scales, we also provide fret interval measurements for the 13-7/8" scale in Drawing #2.)
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Q: I've never heard of gauze being used inside a mandolin's f-hole. Is this your invention?
A: I'd love to take the credit for it, but gauzing is a tradition that began way before my time. Here's a photo (left) of the inside of Monroe's F5 when it was in for repair following the 1986 "vandal" catastrophe. And, here's a photo of an L5 guitar soundboard (right) - both instruments have gauze around the f-holes. It's interesting to note that as badly damaged as Monroe's soundboard was, the two f-holes survived the damage and were basically intact, much of which I attribute to the presence of the gauze. (We use gauze on all of our mandolin kits, and Gibson still uses gauze in their mandolins, today.)
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Q: I read somewhere that the tone bars in F5s are symmetrically positioned and both bars are the same size. Your drawings show them as not being symmetrically positioned and that they are different sizes. Which is right?
A: Going back to Mr Bill's mandolin might be the best illustration of tone bar positioning. Note that the treble bar (lowest one in this photo) is positioned more closely to the centerline than the bass bar, and that the treble bar is narrower than the bass bar. And, I've found these tone bars to be in slightly different positions on various Loar-signed F5 mandolins.
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Q: I thought it was better to use braces with vertical grain than grain at an angle like the tone bars you show in your drawings.
A: Angled grain is the correct orientation for brace and tone bar stock, and angled grain has been used by builders of all types of string instruments since the craft began. Even piano makers use angled grain for the braces on their piano soundboards. Here is an array of photos that might be helpful to appreciate the angled stock used by various manufacturers. From left to right, top to bottom, are: Monroe's F5, Martin (cutaway intersection of two braces), Gibson, and Ovation bracings.
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Q: You said [in the section on bending the ribs] that maple has a lot of sap and that's why it bends easier. But, dried wood doesn't have any sap.
A: Yes, you are absolutely correct that dried wood doesn't have sap, and I don't mean to suggest that sap, in its liquid form, is in dried wood. When the raw lumber is dried, the sap turns into crystalline glucose. This is similar to, but certainly not the same, as what happens when honey hardens and then liquefies again when heated. When maple is heated - and especially when it is steamed - the crystalline glucose softens again, becomes syrup-like, and greatly aids heat dissipation, cell softening, and results in easier bending. After we steam bend about 10 or 15 sets of mandolin ribs, our shop begins to smell like a candy factory! A similar thing happens in rosewood. We often say that "rosewood has a lot of oil content," but that doesn't mean to suggest that you can squeeze oil out of the wood. The hardened oil and resins become very evident when the wood is heated or steamed and often yields a cakey-like substance on the surface which can be scraped off with a razor blade or removed with lacquer thinner or acetone.
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Q: I've been told the rim stock should be .100" and not 125" as indicated in your book.
A: There's actually more to it than that. A little known detail on the original F5s is that the ribs (rim) were sanded to an arch on the outside and were not flat as most builders do today. When properly executed, the rib will actually be thinner at the top and bottom (measuring about .100" at top and bottom) and about .125" in the center. This sanding has to be done prior to cutting for the binding notch so that the binding is not sanded too thin once it is installed. (I debated mentioning this in the book and felt that shaping the ribs this way would be very difficult to accomplish for most first time builders.)
The difference in height between the crown and either edge of the ribs is about .020" (and varies slightly all along the rib. On rib sets I provide, I prepare them to .120" thick so they can be used either flat or sanded to the arch (.100" at the edge and .120" in the center area) and still be sufficient for gluing to the soundboard and backboard. We're now showing this detail in our ProSeries F5 Mandolin and ProSeries H5 Mandola drawing sets.
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