My Side Port Binding Process (LONG)

[Eric Knapp]

Hi, All.

Here's my process for binding side ports. It's just how I am doing it after 5 trials. The next time will be on my current guitar builds. I'll probably change it over time but this is what's working for me now. I am a former teacher so I am going to show too much detail. I can't help it! Sorry about that.

It's starts with this form I made. It's 6 layers of 3/4" plywood that is a tapered ellipse. I don't know what the mathematical name for it would be. Elliptical cone maybe?

It has about a 2º taper. I did the taper and shaping on my disk sander.

Then I trace the ellipse on the side. The pencil line doesn't need to be precise at this point.

Next is drilling a hole and cutting out the ellipse well within the line.

(Continued in the comments.)

[Eric Knapp]

Once I have the hole I will use a file to shape it a little.

I shape it with a file until the form fits into the hole to about here.

Then I put self-adhesive sandpaper on the form.

Here I'm starting to use the form to shape the hole. It's like a perfectly shaped rasp.

As I work the sandpaper on the hole the form fits farther into the hole. I move the sandpaper and keep shaping.

(Continued)

[Eric Knapp]

I keep shaping the hole all around until the form fits like this without the sandpaper.

I now have a very nicely shaped elliptical hole with smooth sides that are tapered to match the form.

Now that the port is ready for binding I'll start making that. For these trials I started with a nice piece of curly maple from my stack.

I cut thin strips on the bandsaw. I believe that sawn veneer bends better than sliced. There are no micro-cracks from a slicing process. I cut the strips to about 1.5 mm (0.060").

I got a nice set of pieces from this stick.

(Continues)

[Eric Knapp]

Then I use the ole painter's tape and CA glue trick to attach them to a thin batten board.

Then it's off to the drum sander for thinning. I first get one side clear of saw marks. Then flip them for final thinning to size.

I have tried several thicknesses. I found that anything between 0.5 mm and 0.7 mm (0.020" and 0.028") will bend well. I tried thicker pieces with limited success. Every trial in my target range bent well.

All sanded and ready for bending.

The next step is to spray some Super-Soft on them and put them in a plastic bag. The directions on the bottle are for flattening veneer sheets. I figured putting them in between paper and board and clamping them was not necessary and that is correct for what I'm doing. I just soak them, put them in a plastic bag, and let them stay there overnight.

(Continues)

[Eric Knapp]

Now we have the actual bending. I think a video would be much better than trying to explain what I do. In the video I'm using a heat gun on it's low setting. The high setting will burn the wood. The low setting provides plenty of heat.

https://youtu.be/OAT0_M44UhU

I do this for a good set of strips. I also bend some black veneer strips. I don't bother using Super-Soft on these, they bend easily.

I let them sit taped up until they are fully dry. I think I left them overnight this time. They retain their bends well.

Then I glue them together in this order.

I use the form again for the gluing. I put the laminations on the form and wrap them tightly with 3M auto-body tape. This is stretchy and compresses the binding well. I don't have a vacuum system and I'm not sure it would work well at this size. It might be better, I really don't know.

Here's the laminated binding after the glue sets and I take it off the form.

(Continues)

[Eric Knapp]

The trickiest part of the process is cutting and shaping the scarf joint. I do this with the form in the side port hole. It's a cut-and-try procedure and is fussy. However, since the port hole is tapered there is some leeway and getting close seems to be good enough. Then I use the form as a wedge clamp to glue the binding to the port. The joint should be very good as the form was used for all steps. I'm getting a nice bead of squeeze out all around.

I made the strips about 7/8" wide as that was the width of the stick I had. It should work down to even 1/2".

Then I pull the form out after the glue sets and start trimming the excess.

Once I flush the binding I shape it with a slight round over. I do this with sandpaper. Adding some oil to the trial lets me see if I have success.


(Continues, just one more time!)

[Eric Knapp]

Here are some glamour shots of the final shaped binding.

Since this was all an experiment I am very open to suggestions on improvements to this process.

Thanks for giving this a look.

-Eric


(All done!)

[Barry Daniels]

Wow! Great process Eric. I don't have anything to add.

[Eric Knapp]

Wow! Great process Eric. I don't have anything to add.

Thanks, Barry. That means a lot.

-Eric

[Barry Daniels]

The tapered plug for shaping, laminating and gluing is genius.

Thanks for the tutorial. I know how much work that can be.

[Karl Wicklund]

First off, that looks great.
Second, I echo Barry, that’s a great process.
Third, that is a well-produced tutorial. Clear and thorough.
Thank you!

[Christ Kacoyannakis]

Fantastic tutorial. I am thinking of using elliptical soundports on both the bass side upper bout and the side of my next archtop, so this is extremely helpful. I am trying to figure out which side to put the side port seam of the binding, towards the top of the guitar or the back. Initially I was thinking top, but then I reasoned that when the player looks down, it will be right there, so maybe back. I think if one were to use darker binding the seam would be even less noticeable, but yours looks very nicely done. Thanks for your educational efforts.

[Darrel Friesen]

Great work Eric. There's more than one way to skin a cat.

[Bryan Bear]

Great tutorial thanks! Nice clean work too!

[Eric Knapp]

The tapered plug for shaping, laminating and gluing is genius.

Thanks, Barry. I don't know where I got the idea but I suspect it has been done like this before.

Thanks for the tutorial. I know how much work that can be.

I used to this for a living for my students. I had to explain complicated computer programming concepts to confused young adults. This one was really fun to do.

-Eric

[Eric Knapp]

First off, that looks great.
Second, I echo Barry, that’s a great process.
Third, that is a well-produced tutorial. Clear and thorough.
Thank you!

Thanks, Karl. A compliment from a fellow teacher is a treat.

-Eric

[Eric Knapp]

Fantastic tutorial. I am thinking of using elliptical soundports on both the bass side upper bout and the side of my next archtop, so this is extremely helpful. I am trying to figure out which side to put the side port seam of the binding, towards the top of the guitar or the back. Initially I was thinking top, but then I reasoned that when the player looks down, it will be right there, so maybe back. I think if one were to use darker binding the seam would be even less noticeable, but yours looks very nicely done. Thanks for your educational efforts.

Thank you, Christ. I am still debating which side gets the scarf joint. That's why I did trials on a trial side so I could hold it like a guitar and see which way I liked better. I'm undecided. I also did this with a light wood on purpose. I always do trials of new things in light woods. When learning to do hand-cut dovetails I worked with pine. If you can make nice dovetails in pine then hardwoods are almost easy. Once I decide on what wood I'm using for the bindings on my current guitars I plan on using the same on the ports. Or at least something similar.

-Eric

[Eric Knapp]

Great work Eric. There's more than one way to skin a cat.

Thanks, Darrel!

[Eric Knapp]

Great tutorial thanks! Nice clean work too!

Thanks for both comments, Bryan!

[Dave Rickard]

Super nice, Thanks for the tutorial