Figuring neck angle with a spanish heel

I am thinking of building a tenor with a Spanish heel which I've never done before. I'd like to have a 15' induced arch on the top. I figure that I will need to add in a bit of neck angle to account for the radiused top. I just wondered how other builders account for the arched top when figuring the neck angle. My drawings say a one degree angle will suffice but I wasn't sure how much compression to expect from the strings that may affect it. Also, does anyone do any sort of raised extension to bridge the space between the fretboard and body?

Hi Thistle,
Are you going to do an arch, or a dome? My first half dozen "ukes were built with a spanish heel and a 25' longitudinal arch. The first few I radiused the upper top brace before installing it and then just sanded a small flat spot on the soundboard where the fret board extension goes. It's really a very small amount to sand. Lately I have been leaving the upper top brace flat (not radiused) and then press it in to the top on a radiused work board on the go bar deck. Doing it this way has required no adjustment to the sound board or fret board extension, so far. Using an arch, I haven't found the need for adjusting neck angle beyond zero, because the arch stays straight.Estimating string compression and amount that the belly rises before it's built is beyond my comprehension at this point.

I don't know if either one these is the best method, but it's worked for me. Hopefully one of the pros will chime in with their experience.

good luck,
Steve

I'm not sure what you mean by and arch or a dome, but the braces will have a 15' radius to them prior to gluing them. I call it an induced arch. Too many luthier terms for the same thing.

TimBuck just posted a thread about neck angle. May it will help. http://www.ukuleleunderground.com/forum/showthread.php?29257-Simple-device-to-set-neck-angle

Thistle,
An arch would be as if you cut a tube in half, and a dome would be like taking a slice off of a sphere. I have never done a domed top, but as I understand it, it requires adjustment to the neck angle whether it's done on a solera or a dish.

Saddle height, nut slot height, fretboard thickness, fret thickness, action and probably a few more variables play into neck angle. For me, I haven't found it necessary to add angle *because of the arch*.

Here's a couple of pics from my very first scratch built 'uke. I built it to the Hana Lima book and plan. I added the arched top because it just makes sense to me, structurally. I had to figure it out on my own, though, so please keep that in mind before cutting anything. I removed a little off of the top of the heel to accept the top so that the top was flush at the edges of the neck. Once glued on I sanded the little two inch wide area of the top that stuck up above the neck so it was flush with the neck, just a few thousanths. The fingerboard met the top perfectly.

The other pic is of the lesson I learned about adding an angle to the neck. The saddle is nearly a half inch above the bridge. Hope this helps,

Steve