Finishing up the soundboard braces

I apologize for the recent distractions that took us temporarily away from the soundboard.  This will finish up the soundboard braces so we can progress into bending the sides.  So... soundboard braces...

A hair's breadth from you know where...

When finishing things like rosettes and back strips and inlays, you soon find that removing material delicately sucks big time!  I am not one to enjoy hours and hours of work with little results, so I figured I'd find a better way to finish the back strip than waste my time sanding endlessly with a 200 grit hand block (by the way, you don't want a power sander of any shape or size anywhere near your guitar, trust me!).  A small trim router with a good down cut bit, on the other hand, is a totally different story...

I got the idea from some obscure place; it might have been an online forum, it might have been Scott Cayce from the Cayce Company in Hunt Valley where I get my soundboard, back, and side pieces thinned.  Anyway, it's irrelevant - what I wanted to do was alter the base of a small Bosch trim router to make a router sled.  Basically I removed the original plastic base, found some good square red oak stock.  Sized the table saw fence to 1/2" from the blade, and ripped two identical blocks.  I made sure they were the same height with calipers, and chamferred the down-facing edges with a sanding block.  I then marked the bolt holes using the original base as the template.  I drilled the smaller through-hole on the drill press first, then followed it up with the larger recess hole for the bolt heads.  Lastly, I marked the inner curvature of the base where the bit comes through on both blocks and trimmed out the overlap with the band saw.  I forgot to take a picture of the finished product, but you can see it action below.

Once I got the router set up, I could take down most of the excess maple without laboring over a sanding block and without risking damage to the back.  Before you start cutting though, make sure you test out your depth.  You don't want to ruin all your work with a deep gouge in your back.  Go nice and slow with even pressure and gentle back and forth or side to side movements to remove the material evenly.  You'll want to blow the saw dust out of the way as you go so you don't end up with inconsistent cut depths.  Once you've gone over the full length once.  Check your work closely to see if there was anything that you missed.  I set my cutting depth so that I could easily finish off the strip with some minor sanding and scrapping.  As the title alludes, you want to be within a hair's breadth of h-e-double hockey sticks, so that you remove as much excess material as possible before you switch to hand work, but not too close that you commit the mortal sin of profaning your back.

After some finishing work with the cabinet scrapper, your back should look like this and will be reading for filling and back bracing!

Git r glued!

Now that the back strip channel is routed, now it's time for fine tuning (ie. fit check).  Take your back strip and try to slide it into the channel from one end.  See how far it slides in.  Remember to be gentle.  If it doesn't go very far, back it out and try sliding it in from the other end.

You'll most likely find, if you cut it right, that it's just slightly too small.  Rather than try to take another pass with the router, which will end up making your channel way too wide or unparallel, work on lightly sanding the back strip.  The most efficient way to get everything right is to focus on the tight spots.  Instead of sliding the back strip in this time, try to ease it in like you're laying screen piping.  You'll find that there are spots, typically either end, which the back strip fits into perfectly.  Mark the spots that don't fit in or are a little too snug on the back strip.  Carefully remove the back strip and lightly sand in the marked spots.  After a few go-rounds and it's almost there but not quite you can also take a small wedge file and lightly sand the trouble spot on the channel itself.  If you have a steady hand you should be ok, but I wouldn't recommend being too aggressive because it's all too easy to boogger up the clean channel edge and make a cosmetic faux pas.

Before you glue, be sure you can readily insert the back strip in its channel without undue coaxing.  It should be snug but not overly so.  It can also be a little loose, but you might have to go back after the glue is dry and the back strip is sanded to fill small gaps with CA glue mixed with fine sawdust.

So on to gluing... before you glue anything, make sure you have a sturdy thin brace to help evenly distribute the pressure from the fiberglass rods.  You'll also want to make sure your clamping deck is set to the right height for the back and back strip and brace and you have all your rods at the ready.  Take your instrument glue (I prefer LMI's white guitar glue) and run a thin bead down the length of the channel.  With a clean finger, smooth the bead in the channel to spread it out.  You don't want the channel to be filled with glue but you do want to make sure you get glue on the channel walls too.  Once everything's nice and whetted, insert your back strip, preferably with the screen piping method rather than the sliding method (sliding will push all the glue out of the channel).  Once the channel is in, it will be very snug; make sure it's in properly and then you can put on the brace and place the clamping rods.

Let the glue cure for a good 20-30 mins, then removed the rods and brace to allow the glue to finish drying.  You'll want to wait a few hours before you consider working on the back strip further.  In the mean time, relax, destress and have some fun like me...