Bend before or after profile?

[kencierp]

No -- I do not use "fudge factors" this is the Martin pattern length and all. The offset is the length of the perpendicular line from the determined height at the neck and tail blocks. Then connect those two points, from there add the rise at the waist curve. Now re-draw the actual cut lines from the offsets to the waist curve rise. Look close at the completed pattern. You can should add about 1" or so material to trim off once the side is in the mold.

[hummingbird]

Ah yes I see I see

[kencierp]

Excellent -- I hope this was helpful

[hummingbird]

Yes very much so thank you

[Darryl Young]

The easiest way I know to determine the side profile is this (not my idea BTW). To use this process, you need a mold for the body shape you will be using and you need a radius dish with the radius you will use for the back of your guitar.

Tape paper to the inside of the body mold. Place the mold on the radius dish you will use for the back of the guitar. Place a washer on the inside of the mold up against the paper. Take a pencil and place it inside the washer on the bottom edge of the hole. Now use the pencil to roll the washer around the inside of the mold while keeping the pencil against the bottom of the hole in the washer and keeping the washer flat against the mold.

As the washer moves around the shape of the guitar body (inside of the mold), the washer will rise and fall with the contour of the radius dish. In the end you will have the perfect shape of the profile traced out on the paper taped on the inside of the mold. When the paper is removed and laid out flat, you can determine the length of the side and you will have the profile needed for the back of the instrument.

Now that you have the length of the side, draw a horizontal line equal to this length. At one end of this line draw a perpendicular line whose length should equal the height you want the sides at the neck. At the other end of the horizontal line, draw another perpendicular line whose length should equal the height you want the sides at the tail of the guitar. Now connect the other end of the two perpendicular lines with the profile you created earlier and you have a perfect profile for that body shape with the correct length and the correct height.

[tippie53]

Martin uses a fixed mold and spreader combination and while the rough blank is pre shaped , it is final shaped once in a mold using a radius disk. The backs are then trued in this fixture . The top does have a 1 1/2 degree angle incorporated into the side set . The different templates you see will get you close but for precise location the mold and disk are what Martin do use.
Having the sides pre contoured will help reduce the amount of work you need to do and make getting things more precise easier .
The key here is to find what works for you . Establishing that geometry will help you control that 14th fret hump.

[hummingbird]

Thanks alot John. Darryl, that is an excellent idea. Thanks everyone, now I have the confidence I need to preceed.

[Tom West]

Bend sides without trimming. Glue blocks to sides. Shape back side with block plane and then the sanding dish. Do the top with the dish,install linings and back to dish for clean up of top and bottom.
Tom