15" Dreadnought in EIR/ Sitka Spruce by Portland Guitar

[Portland Guitar]

We’re starting a custom build for ZacInSC, the idea behind the guitar is that it is very plain from the outside but carries a full, rich sound. As such, it will have no rosette or purfling, only binding. The body shape, instead of a standard slope shoulder dreadnought, one with a lower bout of 15” is to be created. It will then follow the dreadnought proportions. This is because the dreadnought is a little harder to play but the body shape has a great sound.

The current forms have been used for fifteen years. The creation of the new forms takes a little planning to get right. The goal is to use the CNC to create them so that any shape or size can be made easily. As well, this makes it possible for us to easily create and sell a form to anyone who want one.

While remaking forms, it seemed like a good time to remake more types of forms. The one we use to get the curvature of the back and top have been used for a long time as well, they were created by hand sanding until it felt appropriate. The opportunity to make a precise form at the same time was too good to pass up.


As it pops out of the CNC here is what the side form looks like.



Each piece will be cut out and cleaned up.
Here are the sides.



We need a positive and negative of the shape to make the guitar. The positive is used when we’re bending the sides to make the right curvature. The negative is used to hold the sides to the form.
The negative



Strips of wiggle wood are cut out then screwed to the sides of the negative.





The side forms are complete as they will be at this point. The next step was making the bowl forms for the the top and back. This was designed and then created with the CNC

Here is the bowl after it is complete with a top to be fitted into it.



For the top, the back half is a bowl while the front is a cone. These next pictures show that this is the curvature of that form.



Since there is a gap undeath the pencil it is curved.



Since it is flat, there is no curvature.

These two necessities are completed. It’s time to move on to the good stuff of the build.

The wood selection is east Indian rosewood and Sitka spruce. We think this is going to make an incredible combination with the body shape.





This is everything for the start. The next steps are to get the sides of the form to be the same curvature as the bowl. This will take quite a bit of hand sanding to accomplish. Then it's onto the meat of the build!

[ZacInSC]

Can’t wait

[Portland Guitar]

It's going to sound amazing. I do daily updates about this guitar to my stories on facebook
instagram
I'll post most of the pictures here as well in weekly updates, but there's more that I don't that show up in stories.

[Portland Guitar]

It’s been a busy week. The body is ready to be glued together and the first sounds are imminent. The frame was put together in a few days and while that was happening the braces, top and back were completed.
Some work is loud, and some is quiet. Our shop is in a residential neighborhood, so we have to be careful about sound sometimes. Jay likes to work in the early morning, before I’m awake which is why the picture story jumps. Alas, I cannot be everywhere at once.
First an overview of the process to get the body together.
We need braces, top, back, sides, curfing, heel and tail blocks. The top, back, braces, heel block are fabricated on the CNC, while the sides and curfing are bent. After the parts are made, they are glued together in the appropriate places.
To make our brace board we laminate a layer of carbon fiber over two pieces of spruce. Here they are being clamped together to form a uniform surface without air bubbles or other imperfections.



The braces are routed out of a single board. Here are the wood side of all the braces used.

Since the braces are created, it’s time to make a top and back. The two pieces are joined and then run through the drum sander a few times to get to the right size.

Here is the CNC creating the inner soundboard pockets and channels.

the braces are glued in once the back and top are out of the CNC and cleaned up.


The braces are clamped in

A go box was used to perform this task. Jay created a bowl bow in the shape of the curvature that the top and back are designed to be in.
 

The complete set.

[ZacInSC]

So is the top pre-stressed with weights the way your precious bracing system was done? I asked on the FB page as well, so feel free to answer only once.

[Portland Guitar]

I answered on facebook. In short we don't need to because we have better control and testing now.

The top and back are done. The next is to get the frame together. We need curfing and the sides so first we bend them into the form.



This is done for both sides and 8 pieces of walnut curfing. We are calling it curfing put it is one piece of wood. Jay thought this streamlined the process and it works just as well.

To cut the bent sides to the final shape, two washers are used as spacers on the outside of the rim. The line is drawn on both sides.



Cut on the band saw



The curfing is glued into the sides



Clamped down



Once this dries the ends are cut to shape then both sides of the form are joined together.



The inside is cleaned up



A tail block and heel block must be made. The heel block is made on the CNC while the tail block is a simple piece of wood. Here a bevel is put on the edge.



In place



Glued into place



We’re adding extra mass on the sides in the form of two pieces of maple. There is a wood screw in the center so we can add weights if desired.
Once this dries the frame is complete and the setup for gluing the top and back on begins.

Here the braces are cut to conform to the shape of the sides.



It fits




That’s everything for now. I’m very exited to hear this guitar. Next update will have sound samples!

[Nahil.R]

Originally Posted by Portland Guitar

I answered on facebook. In short we don't need to because we have better control and testing now.

The top and back are done. The next is to get the frame together. We need curfing and the sides so first we bend them into the form.



This is done for both sides and 8 pieces of walnut curfing. We are calling it curfing put it is one piece of wood. Jay thought this streamlined the process and it works just as well.

To cut the bent sides to the final shape, two washers are used as spacers on the outside of the rim. The line is drawn on both sides.



Cut on the band saw



The curfing is glued into the sides



Clamped down



Once this dries the ends are cut to shape then both sides of the form are joined together.



The inside is cleaned up



A tail block and heel block must be made. The heel block is made on the CNC while the tail block is a simple piece of wood. Here a bevel is put on the edge.



In place



Glued into place



We’re adding extra mass on the sides in the form of two pieces of maple. There is a wood screw in the center so we can add weights if desired.
Once this dries the frame is complete and the setup for gluing the top and back on begins.

Here the braces are cut to conform to the shape of the sides.



It fits




That’s everything for now. I’m very exited to hear this guitar. Next update will have sound samples!

That is very interesting. If I am not mistaken it looks as though your top and back are not in direct contact with the tailblock, is that correct?

If so I would love to know what advantages you find by doing it that way? (decoupling a bit maybe?)

Thanks for sharing.

Nahil.

[Portland Guitar]

The reasoning is close to this: Giving the top and back a little extra space at the tail won't make or break gluing the top and back on and the effect on the sound is too minimal to measure. As well it's easier to glue the tail block in rather than cut our the curfing and then glue it in.

[Nahil.R]

Originally Posted by Portland Guitar

The reasoning is close to this: Giving the top and back a little extra space at the tail won't make or break gluing the top and back on and the effect on the sound is too minimal to measure. As well it's easier to glue the tail block in rather than cut our the curfing and then glue it in.

Ah I see. Thanks.

[Portland Guitar]

Here is the finished guitar