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Preparing the Back for attachment

Sanding the rim
First of all, I taped the sand paper to the board and began sanding the side rims.
I read this method from the Cumpiano book.
When I worked on the upper bout, I realised that the Spanish foot section will disrupt sanding as the foot area is taller than the surrounding side rim.

At first, I wanted to make a radius bar, in order to sand the upper bout, but decided against doing it because it was too much work and the benefits wasn't alot.
In the end, I found a simpler way: attached 2 board on each side of the foot and paste the sand paper on the raised board.
The raised board is clamped to the main board using C-clamp.

Sanding the rim. One end is for upper bout with a raised side, the other end is for lower bout.

The raised side are held by a C-clamp.

Sand till no gaps in between.

Back struts
After finished sanding the rim, I proceed to work on the back struts.
Nothing special except for marking the position of the back struts to the rims.
The rest is just standard trimming and cutting process.

Back struts cut.

Taping the struts to the back.

Fitting to the rim

Sides marked (tape) and struts trimmed to fit the side rim.

Back fitted.

Shaping the struts
For shaping the struts, I did not use any predefined radius, but rather draw a free curve joined using french curves ruler on a vanguard sheet.
Then I cut out the curved sheet and draw a center line on the struts for transfering the curve to the struts, aligned on the center line.
To keep the gluing edge square and flat, I use a shooting board method.
I learn this method from a Erik Schmidt who was also a first time builder but with great organisation and great woodworking skill.
You can read the forum thread of his build here

I did not make a shooting board but simply raised the struts height using a cut out MDF and plane the curve accordingly.
(It was the same MDF which I had intended to make for the radius bar :) )
It was a simple and effective way compare to free hand method which I used the last time I did the back struts.
Keeping the gluing surface square is important for optimum gluing strength.

Shaping the struts using a shooter board method.

Another view

Yet another view

After the curve is done, I proceed to scallaping the struts to reduce the weight of the struts while keeping the strength (height constant).
My idea is to keep the end square and anything in between to have a curve cross-section.
I intend to keep the struts at full height and no tapering at the ends.
That is the main reason why I keep a curve cross-section in the middle and square at the ends.

Here is how it looks in final state. I think the curve can still be improved on.

View from the end.

All three struts done. The lower bout strut is thicker as it is the longest.

Another view.

I did some further work on the back struts.
I re-read the Rommanillos book on Torres and the back struts height was about 17mm.
Mine was over 20mm.
So I decided to reduce the height of the back structs.
Again the shoot board method was used but this time round I make the curvature less sharp more round instead.

Middle strut profile

Side view of 3 struts

Oblique view

Gluing the back lining
Finally the last task of the day is to glue the back lining.
I did consider to use laminated solid linings as I had 2 pieces of basswood about 90cm long.
But in the end I decided to just use the lining which I bought from lmii to save time.
I was lucky that I have bought clips previously from Daiso.
Surprisingly the quantity of the clips was perfect: 4 boxes of 8 clips each: just nice for the entire back lining.
The process was similar to the front lining except that now the back struts were there when I glue.
I had to position and match the lining according to the marking on the tape which I had done earlier.
All in all, it was a familiar process.

The lining glued.

I also glued the lining under the brace.
By accident I discover the height of the brace is about the same as the height of the lining.
So it kind of make it neat and tidy.
Maybe next time I will make a brace pocket holder for the line at this part.

Gluing the lining under the brace

Gluing done

Brace fits just nice

Glue the back crack

I finally thought of a way to glue the crack at the back: Clamp 2 pieces of wood sandwiching the back on each side of the crack and use 2 F-clamp to draw the 2 pieces of back towards each other.
Look at the pic for a better explanation.

The gap looks closed and hopefully the CA glue will do the job.
However, I was worried about the CA coloring the Maple back insert between the 2 back pieces.
Well just have to wait and see.

Here is the back after the gluing. The darkened part hopefully can be sand away.

Reinforcement for sound port
I also bend some basswood for a sound port reinforcement.
First I thickness it using my Stanley #4 (it's been a long time since I used it as I use block plane more)
The result wasn't too good but can be smoothen using a file.
Nonetheless I proceed to use a heat pipe to bend the piece and periodically checking the curvature with the guitar.
It was quite easy to bend especially with the water.
This is the first time I bend a straight piece from scratch the experience was very satifying.
The result was quite good.

The bent piece.

Cut and plane to side. However the back still needs to be smoothen.

I had glued the reinforcement piece to the back of the sides inside the body.
It will be ready for cutting of the sound port in the next session.
However, I still have yet to finalize the sound port design...

Clamping the reinforcement

Inside view

Consideration for gluing the back on
I had 2 options:
1) Glue the struts to the back and the back to the body
2) Glue the struts to the rims, and the back to the body.

Both of the way required different sets of tools.
1) I had to make some cam clamp or have clamps with enough throat length to reach the center of the struts.
2) I need to build some supports underneath the brace. This method is from Romanillos way of gluing the back.

You can read the Romanillos method of build from another great first time builder
Waddy, who is also another fellow OLFer.
Or his Photobucket Album

After some serious decision I decide to adopt the 1st method.
I got hold of some more new F-clamp with a longer throat.
The clamping was a familiar procedure.

Clamping middle and lower bout brace

Clamping the upper bout brace

After gluing the brace, I began to fit the back but it just wouldn't fit into the slots.
I had to adjust the lining (chisel away and glue new ones) in order to fit the back.

Back enclosed (not yet glued)

Fitted back inside view

I had also started making the caul.
Trying to get it fit the brace and curvature of the doming.


Binding attachment for the B&D RTX
To cut the binding, I needed 2 more tool: one is a attachment holder for the B&D RTX and the other is a gramil scriber.
I have began building the attachment out of MDF, basing the design on the Stewmac version of the dremel attachment.
There is a second part of the attachment which will allow the adjustment of height.
I intend to use spring and adjustment control using screws.
Again the base will be made of MDF.
There will be an edge guide to cater for binding purposes with screw adjustment: something similar to the Stewmac version which is a very refined made tool (but expensive)
The main holder for RTX body is not fixed, to allow for adjustment for tool squareness to the front panel.
However, I think the front part is abit too bulky and may reduce the footprint of the frontal portion.
This attachment can also be attached to my drill stand for using it as a bridge hole mini drill press.
Hopefully I am able to complete the whole attachment by the next session.

The B&D RTX Attachment holder 1/2 done: top view

Back oblique view

Front oblique view