Bending the Sides

Last night I went over to my buddy Dave's shop to bend the sides of the guitar. This is the process that I've been asked about the most by people when I talk about building an acoustic guitar. Basically you get the boards wet, heat up a pipe, and bend the wood around the pipe in a series of heating and cooling.

I used this pipe, below. Dave welded a cap on the end and I drilled an exhaust hole out the bottom-front. Then I simply shot the propane flame into the back of the pipe (held by a vise) to heat it up.

I decided to test this process out on a piece of scrap rosewood to get the feel for the bending process.

The hot pipe drys the wood out quickly so I have to hit the wood often with a water spray bottle. We noticed the sweet smell of rosewood billowing in the shop after a while.

You pretty much just have to rub the wood on the steel for a while and then you will feel the wood relax. Then you apply some pressure and hold the bend while you lift the wood off the iron. When the air cools the wood it retains it's shape.
There is a lot of checking the bends to a pattern I've drawn on a board. Then I would mark the spot of my next bend by grabbing the wood in that location and bending some more.

Notice how the wood looks lighter where the iron is touching the wood – it's drying the water quickly.


Finishing up the large round bend at the back of the guitar.

Again checking it to the (actual) template.
Both sides done.

I took these home and laid them on the back of the guitar (just to get a visual). Wow.

After these photos were snapped I decided to clamp the sides to a board in the exact shape of the template – hoping that this will keep them from re-adjusting shape before I'm ready to assemble the box. I absolutely love the look of this rosewood body and am very motivated to keep this project moving along.

Addition: I showed up at the shop at 7:30 and left at 10:30. So I'm guessing both sides and the test piece each took about 45 minutes each to bend. We did have some set-up time and some BS time. Our buddy Chris showed up too and he watched the shaping of the last board. Was nice to catch-up with him.

– Dave thanks so much for the use of your shop and for doing the welding of the pipe. You've been a big help!

More Gluing and Carving of Braces

Carving up the X braces. Still need to sand these down a bit but pretty much completed the soundboard.

Gluing up the back braces.

Rounding the back braces while the glue drys.

Much of the carving was done with this little plane that Creig loaned me. I may forget to give this plane back to him – it's very useful for this type of work.

All carved but not sanded.
Another angle of all carved but not sanded

A lot of sanding tonight then, maybe bending the sides.

Back Bracing and More

Cut out the back of the guitar. The side you see will be inside the guitar when assembled.

Laying out the braces and gluing the center graph down. The graph is sitka spruce, just like all of the bracing. But each of the grafts came from the left-over material from the soundboard.

Wanted something heavy to weight it all down while the glue dried – my power amp does the trick.

sanding the braces to allow for the slight curve of the back.

Gluing the first brace down. Forgot to shape the grafts before doing this – UHHHG. Oh well it will just be a little more difficult now.

Taking material off the X bracing on the sound board. Completed this step and then...
Chisels are sharp! I was using my finger as a guide but when my finger stopped the chisel didn't. Always have both hands on the chisel they say... and I do, but I managed to put a small cut on my finger anyhow – time to quit for the night.
It's OK. Blood makes guitars sound better.

Brace all over the Place – soundboard

Gluing down the upper face brace.

Couple comments about humidity on the last post. Not being too dry or too humid is really important when bracing – I've read that 40% is about where you want to be. You also want to make sure you wood has had time to climatize prior to bracing. Here is the temp/humid gauge I picked up at Walmart. It sure is hot in my basement – for Michigan that is...

Also glued down the lower face braces (below lower left) and I spent some time shaping all three.

Better look at the upper face brace / trans brace / and sound-hole braces. I just realized I need to make a little groove in the center of the trans' brace to make room for truss rod adjustments. I'll do that tomorrow.

Lower face braces, carved but not sanded (below).

Finger and lower trans braces sanded. Ohhhhhhhhh.
Cutting out the slots for the X braces. there is one already cut above the one I'm cutting.

Gluing up the X braces. It's important that the X braces contact the bridge patch and the sound-hole braces. They fit perfect!
This will set over-night and I will finish by shaping the X braces tomorrow night. Then I will move on to bracing the back.

In an older post I stated that I would take a photo of my past projects when I finally got up to the cabin to see them... well I went to the cabin this weekend (that's why there was no posts). But I did get some photos of a roll-top bread box and a gumball machine both completed as a freshman in high school. You can see them here at the bottom of the page on this: Old Post

Bracing

Gluing on the upper trans graft and the bridge patch.

Gluing the finger braces and the sound hole braces. I did place about 4 more clamps on this after the photo was taken.


Ready for carving. Each finger and sound hole brace needs to be thinned down and shaped like a pyramid or parabolic from the board up.

Rough carved shapes.
sanded down – much closer to the finished shape.
Done shaping the small braces. Five more to go, but because the these will put a slight curve on the soundboard I'm going to wait to glue them up 'til later this week.Getting there slowly!

Measure Twice, Draw once (then sand it off and do again)

So it's a little too humid in the basement to start carving the braces, so I didn't get much done this last weekend (was up to 70%). I've got a de-humidifier on down there now and will hopefully be ready to start gluing on the braces tonight. I drew out the bracing pattern on the soundboard, and realized after everything was drawn the most critical position (the bridge) was in the wrong location... As shown in the below photos. I did sand it off and redo all the marks. I also did a final thicknessing of the soundboard and am happy with the way it sounds when tapped. That board resonates like crazy – wonder what the bracing will do to the sound...





I also made the bridge patch (the small peice of hardwood that attaches under the soundboard at the bridge location). I did have some trouble thicknessing it to 3/32 of an inch. It got caught in my sander... Will hopefully get that the upper graft and maybe the finger braces glued on tonight.

Sound hole Rosette Final and Bracing Rough Cut

Cutting the groove for the Petoskey stone inlay.
I can't even express how worried I was at doing this process. I don't know why but I expected something to not work out. The precision needed for this was exact. I measured 3 times for each cut and practiced a bunch of times. Before committing to the actual board – you can see practice cuts in the upper left of the photo below.

First cut: outer part of the ring.


Second cut: Inner part of the ring.

Third cut: decided to do a third to loosen up the material in the middle of the other two cuts.

Chiseled out the remaining wood.

Placing the binding in and preparing to do a dry fit.


Starting to glue each piece in the groove – I was surprised at how accurately I shaped and thinned each piece – they fit perfect!


Final piece inserted. I broke this piece but didn't care because it will be covered by the fretboard when the instrument is assembled.

I started sanding, but that didn't work so well. I discovered that filing was the way to go. Then I finish it off by sanding at 80 grit with an orbital. I took off a lot of material as you can see on the soundboard.

Cutting the sound hole.
Now it's starting to look like a guitar.

I also rough cut all the bracing material for the sound board. (below)


I had also finished up that box joint Jig I posted about earlier – it turned out pretty nice.


I realize I haven't been posting a lot lately, but I think I'm over a pretty big hump and should be moving along once again. Lisa has a new job and has to go to bed around 6pm to 7pm which affects the amount of time I can be running power equipment. And since I get out of work around 5-6pm that leaves a small window during the week, but I'll find a way to get this moving.