First try at building

[rogthefrog]

Originally Posted by emmsone

If all goes to plan i'm planning to bend the sides for my build today or tomorrow so i'm in the bending mindset right about now. Are you bending on a bending iron?
If you are, one tip I was given was to place something between the iron and the sides, brown paper is ideal. It has enough moisture in to conduct the heat without burning, but if it does get to hot and burn, it burns before the sides do. You don't have to do this, but if the wood is lighter in colour or you are nervous this is handy. If the wood is struggling you can replace the brown paper with a wet rag, this adds a small amount of steam to the process and can help, but this option is a backup for when the more 'normal' efforts aren't quite going to plan

The second tip and one that is much more important, is when you wet the sides, and when you re-wet them with spray, use HOT water, not boiling hot, but plenty hot. If you are heating the wood up with the iron and then it dries out if you then re-spray it with cold water, you are actually cooling the wood down, the iron then needs to re-heat the wood and heat the water up to temperature before the wood will be pliable again.
On the tighter sections, it can be handy to put a backing board on the outside of the wood while bending, it keeps it from cracking and blowing out
Also, don't hold the wood in one place while you bend it, kinda rock it from side to side around the iron, also keeps it from burning.

My iron goes up to 300C, I ran it at about 260-280C for my last bending efforts, (walnut sides at 260C and bloodwood bindings at 280C+)

Other then that, if you have practice sides, have at it. Once you start and as soon as you get the feel of it (and there is a definite point where you can 'feel' it working) it becomes fairly obvious and self explanatory, but until you have had a go, its hard to fully explain.

Hope that helps

David

Great stuff, thanks. I hadn't thought of using hot water instead of cold, but it makes a ton of sense.

My bending iron is something I made with a length of steel pipe and an electric charcoal starter on a dimmer switch so I can control the temperature. I also have a movable cap at the end of the pipe so I can also control how much heat stays in the pipe.

I did my very first bends a moment ago, using offcuts from the sides, same wood and thickness as the real thing. Much to my surprise, they went well. Of course they're not as wide as real sides, so it'll be different, but if I can do a spiral without cracks or scorching, it's a good sign.

[rogthefrog]

Emboldened by the spiral bend, I made a few concave and convex cauls to hold the sides against the mold with turnbuckles, and bent the first side. No breaks, no cracks, only some superficial splintering at the waist on the inside. It's clamped and drying in the mold now. Hopefully it turns out OK and I can bend the other side. I'll bend my practice sides and likely laminate them if they turn out OK.

[emmsone]

Excellent. As I said once you get the 'feel' of it, as long as the wood isn't something out of the ordinary or something known to be hard to work with, its not as challenging as it might seem

David

[rogthefrog]

Originally Posted by emmsone

Excellent. As I said once you get the 'feel' of it, as long as the wood isn't something out of the ordinary or something known to be hard to work with, its not as challenging as it might seem

David

It's fun. I kind of want to bend the other sides I have for future builds. But one thing at a time.

[emmsone]

Originally Posted by rogthefrog

It's fun. I kind of want to bend the other sides I have for future builds. But one thing at a time.

HAHA.
Just don't make the mistake I just made of bending the sides into a left handed guitar by accident. Its an absolute and complete nightmare to fix

[Pat Foster]

Originally Posted by charles Tauber

<snip>
Also, using go bars whose length is such that they aren't bent as much reduces the sideways tendencies of the clamping.

I would respectfully disagree with this, a common misconception. Bars that are placed so that their points of contact describe a vertical line perpendicular to two parallel planes have no lateral forces and aren't affected by an increase in bending.

Additionally, once past a certain amount of bending there is no appreciable increase in force with increased compression. Try it on a bathroom scale.

Back to regular programming.

Pat

[charles Tauber]

Originally Posted by Pat Foster

I would respectfully disagree with this, a common misconception. Bars that are placed so that their points of contact describe a vertical line perpendicular to two parallel planes have no lateral forces and aren't affected by an increase in bending.

True enough.

However, if you look at the photo in question, you'll see that the two ends of each bar are not vertically aligned one above the other. A simple statics analysis will show that when offset, as they are, they create equal and opposite forces plus a moment. That moment is what causes the tendency of slick surfaces to slide laterally.

Shortening the bars reduces the likelihood of displacing the two ends vertically since that displacement is being used to reduce the amount of bending required to fit the bar between its two fixed planes.

[rogthefrog]

Originally Posted by charles Tauber

True enough.

However, if you look at the photo in question, you'll see that the two ends of each bar are not vertically aligned one above the other. A simple statics analysis will show that when offset, as they are, they create equal and opposite forces plus a moment. That moment is what causes the tendency of slick surfaces to slide laterally.

Shortening the bars reduces the likelihood of displacing the two ends vertically since that displacement is being used to reduce the amount of bending required to fit the bar between its two fixed planes.

Wouldn't two bars bent in opposite directions, one at each end, best address the sliding problem? Like this:

( | | )

The first side came out of the mold the way I wanted it (yay), so I bent the other one and it's now drying in the same mold.

Because bending is so much fun and I have a spare set of sides, I'll bend those into the same shape this weekend and see if they agree to be laminated into the real sides.

[rogthefrog]

Originally Posted by emmsone

HAHA.
Just don't make the mistake I just made of bending the sides into a left handed guitar by accident. Its an absolute and complete nightmare to fix

Wait, how does that work? Did you put the cutaway on the wrong side? Otherwise I don't think the sides care what handedness the guitar is.

[TEK]

They do if you have pre cut the profile of the sides before you bent them.
Once cut there will be a top and a bottom to the sides and they will have to be bent in opposite directions.
Travis

[charles Tauber]

Originally Posted by rogthefrog

Wouldn't two bars bent in opposite directions, one at each end, best address the sliding problem? Like this:

( | | )

That's one option, yes.

Easier to manage if you keep the ends vertically aligned, as Pat suggested. One way to accomplish that is to make the bars shorter so that they don't have to bent as far resulting in less tendency to offset them.

[Shuksan]

Originally Posted by rogthefrog

Wait, how does that work? Did you put the cutaway on the wrong side? Otherwise I don't think the sides care what handedness the guitar is.

If you rough cut the profile of the sides before bending, then the top and back edges of the sides have been determined and it matters which side gets the cutaway.

[rogthefrog]

The second side bent as successfully as the first, and they're both hanging out in the mold.

I never liked the way the second reinforcement strip on the back turned out, so I chiseled it off (again) and replaced it with an offcut from one of my practice sides. I think it's cherry but it could be any number of mahogany-like woods (khaya etc).

That strip also had notches cut out for a bracing layout I wasn't super excited about, so this will also allow me to do something simpler (one X-brace and standard transverse braces). Once the strip has dried I'll put on the X-brace, which is already radiused.

I'm not sure I'll be able to salvage the Spanish cedar neck for this build. It's the first thing I ever worked on, and some of the sanding and cutting I've done is too deep. I'm also allergic to the dust. I'll persevere, but just in case I started laminating a replacement neck out of maple and walnut.

[LouieAtienza]

Originally Posted by rogthefrog

Wait, how does that work? Did you put the cutaway on the wrong side? Otherwise I don't think the sides care what handedness the guitar is.

The way the grain is oriented may matter... say one edge of the side matches up better with the back, or maybe the sides have some sap wood. I also flex the side woods first; some of them may bend easier at one end than the other, and I'll use that end for the waist and upper bout if possible.

I bent one walnut side the wrong way (same as the other side), and to my surprise I was able to re-bend it the correct way. I don't think that could happen with denser brittle wood!

[rogthefrog]

Upper and lower transverse braces for the back are glued on and drying. I'll add a couple of finger braces under the arms of the X brace, then it's carving time. I took Charles's advice and trimmed my go bars so they don't bend as much. That made it easier to keep braces in one place, and less dangerous if a bar gets loose. So thanks for that (and so many other things), Charles.

I did the back first to learn the mechanics of profiling, laying out, gluing and carving braces before I do it on the more crucial top. The back looks pretty terrible, especially inside, and the thickness isn't uniform, but that's what learning is about.

I do find that each piece or cut I make is visibly better than the last, so that's encouraging.