bending flat sawn guitar sides

[Dan of SC]

I bought a board of walnut from the local woodworkers guild to build a guitar in an effort to save some money. I found the best section of it to use for the neck, but the side are flat sawn. When bending them they want to cup pretty bad. Anyone have any advice on how to deal with this? Thanks, Danny Gray

[printer2]

Did you bend them on a hot pipe or in a bender? If the bender what did you have for backing slats? Did you let the sides cool down in the bender? How thick are the sides? I am guessing those are things others will want to know to answer your question. I bent some flat sawn pine and did not have a problem. I have some flat sawn walnut that I want to bend soon so I am more than just a little interested in the answer you get.

[LouieAtienza]

Try to bend them dry if using a pipe...

[Dan Bombliss]

I don't know that I would every to to bend anything dry. When the wood gets warm, it becomes very bridle. Finding a good balance between the proper thickness, and the proper amount of moisture takes practice. Generally if you're fighting really bad cupping, it would be possibly too thin of sides, or too much moisture. Some woods are pickier than others, and there is a slight bit of side cupping that you can live with. Side braces can help remove mild cupping, and if it's mild enough, it can sand out at the end. Although it doesn't take too much cupping, to be too much to be able to sand out.

The sides should sort of feel like spring steel when you hold each end and try to "bounce" them.

[LouieAtienza]

Originally Posted by Dan Bombliss

I don't know that I would every to to bend anything dry. When the wood gets warm, it becomes very bridle. Finding a good balance between the proper thickness, and the proper amount of moisture takes practice. Generally if you're fighting really bad cupping, it would be possibly too thin of sides, or too much moisture. Some woods are pickier than others, and there is a slight bit of side cupping that you can live with. Side braces can help remove mild cupping, and if it's mild enough, it can sand out at the end. Although it doesn't take too much cupping, to be too much to be able to sand out.

The sides should sort of feel like spring steel when you hold each end and try to "bounce" them.

It's not like the wood is completely dry, it still has about 5 to 8% moisture content, which for me is enough for most woods save for the waist and maybe upper bout. Even then I try to use as little as I can get away with, applying some moisture with a damp rag or sponge.

[arie]

talking about bending, i recall seeing charlie hoffman pulling eir out of a trough of water completely limp, slapping it on to his overholtzer mold and setting it. have to try that some time -what could be easier.

i bend "semi-dry" over an electric bending iron with a spray bottle of di water used for local spritzing. i do thicker binding this way as well. purfling i'll do dry.

cupping can be managed by using a bending slat on your iron or pipe. if you're getting cupping on a machine you've got other problems.

as always if you're unsure bend up a sample. i prototype stuff all the time.

[printer2]

Originally Posted by arie

cupping can be managed by using a bending slat on your iron or pipe. if you're getting cupping on a machine you've got other problems.

It is always the other problems that worry me, especially when I don't know what the problem is till after it shows up.

Just to warm myself up I did some cherry sides on the pipe for a little guitar. I am guessing user error as I got the first side not bad but introduced a twist in the second side.



It was a pain to work out and I still have a little more distortion than I like but I will probably live with it.

[alohachris]

Aloha Danny,

There's no difference between bending quartersawn or flat-cut sides, though one is easier than the other. General bending procedures apply.

Basic Side-Bending Techniques:

- First, take your time - no rushing/no distractions - listen to & feel the wood you're bending. Start at the waist, rocking the side back & forth to heat the area, not only the point. Then move on to the next tight radius (upper bout). Then bend the lower bout.
- Make sure your sides are not too thick (especially at the waist which some luthiers thin more). Depending on the piece of wood, my sides are typically between 2 & 2.4 mm (0.078 "- 0.09") thick.
- Soak the walnut (use quartered - cheap & plentiful) in a tub for 5 minutes or spritz it.
- Make sure your pipe (or whatever it is) is hot enough so that you can "throw" some water at the pipe & it will kick off. Keep a wet sponge or spray bottle nearby to avoid scorching the wood. Make sure the pipe is hot enough (a key) & don't force the wood to shape.
- Once the sides are exact or very close to your external mold's shape, clamp them in & allow to dry overnight. The mold makes it easier to hold the shape.
- If one side is way off, then spritz & bend it back to flat & do it over again.
- TIP: If bending by hand, after you bend a section to shape (like a waist or cut-away), hold it in your hands in shape & allow it to cool for few seconds.
- Quartersawn woods hold the bending shape much better & bend more easily than flat-sawn woods - which like to cup. I had a flexible very thin aluminum, 24" long & 6" wide tool w/ handles on both ends that was helpful w/ bending problem sides. Not sure if LMI has it anymore. But it did help by keeping in the heat on the outside & also supporting the wood there to hold shape. I used it w/ figured sides.

RE: Using Flat-cut vs. Quartersawn woods for Guitar Backs & Sides.
Beginning w/ the increased scarcity of Brazilian Rosewood (& now just about all tropical hardwoods used by luthiers), it's become more & more acceptable for acoustic guitar makers to use flat-sawn timbers for instrument back & sides. All kinds of justifications are made in the name of using it. All kinds of positive experiences using it can be cited. Sure, flat-sawn woods can look a lot more interesting than quartersawn (some amazingly so) & that attracts player/customers who may not know the differences between how QS & Flat-sawn woods behave.

But unless an instrument with solid flat-sawn backs and/or sides is kept in a humidified vault in a near season-less environment all its life (the collector's world - not real musicians), the chances of it functioning & looking the same after 10 years are pretty slim. Chances of it thriving past 20 y.o. intact are even slimmer.

Flat-sawn guitars under all that pressure (250 lb's per square inch) - no matter how well cured or made - tend to deform (I've repaired a few concaved, flat-sawn backs that became basically two sagging, reverse-cupped pieces "connected" by a centerline), warp & crack over time. They do not handle seasonal change or indoor heating very well. They do not travel well. That makes them less useful to real musicians & giggers, IMO. The vast majority of guitars using flat-sawn timbers won't make it to "classic" status.

Therefore, I'd recommend against using any woods that are well off the quarter for a musical instrument. Luthiers from the past always used quartersawn woods for their best instruments. So, why should we lower the standards arrived at over centuries of instrument building - for appearances sake? If you want your Walnut guitar (QS Walnut is easy to bend & holds its shape well) to be durable & in-use for many, many decades, then only use quarter-sawn backs & sides.

FWIW, I would rather make a four-piece back using quartered lumber than a two-piece flat-sawn back - something I did recently w/ a Madagasgar RW set.

Something to think about.

All the best, Danny!

alohachris

PS: I've been a regular gigger for 56 years - my self-made, quarter-sawn guitars travelled well being played in over 60 countries - no cracks! I've also made 221 guitars in my life. As a full & part-time luthier building in humid Hawaii, I've had to pay strict attention to the woods I combine & use, plus my shop humidity levels, to enable me to ship instruments made here to dry places, played in very dry, indoor-heated spaces, or travelling a lot through different climates. I only use quartersawn woods because of that experience & also because of the tradition.-alohachris-

[arie]

Originally Posted by printer2

It is always the other problems that worry me, especially when I don't know what the problem is till after it shows up.

Just to warm myself up I did some cherry sides on the pipe for a little guitar. I am guessing user error as I got the first side not bad but introduced a twist in the second side.



It was a pain to work out and I still have a little more distortion than I like but I will probably live with it.

since your first side is better then your second what changed? were you rushing? i make little guitars and honestly the waist and the upper bout are a pain. the radii are quite tight compared to a big old dred.

imo it comes down to these:
-thickness
-temperature
-support
-technique

also i read that supersoft or downey fabric softener can help with pesky wood. haven't tried it and don't know the particulars, but you could check it out.

[printer2]

Originally Posted by arie

since your first side is better then your second what changed? were you rushing? i make little guitars and honestly the waist and the upper bout are a pain. the radii are quite tight compared to a big old dred.

imo it comes down to these:
-thickness
-temperature
-support
-technique

also i read that supersoft or downey fabric softener can help with pesky wood. haven't tried it and don't know the particulars, but you could check it out.

Like I said, user error/technique. Not paying enough attention and putting a little twist in the side, going back to fix it, now that area is out a bit, try tweaking this, now that is out... Yeah it is a pretty tight radius, could have thinned it more. Tried some of the fabric softener on the cocobolo I bent. Not sure if it helped any. Looked at getting some supersoft but getting a bottle across the border was about $50.

So, why should we lower the standards arrived at over centuries of instrument building - for appearances sake?

In my case more because it is a cheap way to get better at building. Mistakes don't hurt as much.

[LouieAtienza]

Originally Posted by printer2

In my case more because it is a cheap way to get better at building. Mistakes don't hurt as much.

Having sides that are just passable because you have to grind half the thickness away to true the sides hurts just as much!

The point being, quartered walnut is pretty common. Not only does it bend easier and truer, hand working quartered wood is so much easier, a pleasure really. I find I have to leave flatsawn sides a little thicker to help it stay true better and leave enough room for trueing. Of course this makes bending more difficult. Heck even quartered wood can have run out, and that can rear it's ugly head in a tight bend. Figured wood would be one example. Backing the wood with metal helps. Walnut is usually relatively easy to bend.

[printer2]

Originally Posted by LouieAtienza

Having sides that are just passable because you have to grind half the thickness away to true the sides hurts just as much!

The point being, quartered walnut is pretty common. Not only does it bend easier and truer, hand working quartered wood is so much easier, a pleasure really. I find I have to leave flatsawn sides a little thicker to help it stay true better and leave enough room for trueing. Of course this makes bending more difficult. Heck even quartered wood can have run out, and that can rear it's ugly head in a tight bend. Figured wood would be one example. Backing the wood with metal helps. Walnut is usually relatively easy to bend.

Locally we only have one lumberyard that carries more than oak and maple that the big box stores do. I would be right on it if I found quartered wood. I actually picked up some oak that was quartered and it is probably the next thing I use after I finish off the cherry and walnut I have. But unless I buy a number of sets adding $50 for shipping adds to the price of one set. I have bought a few sets but until I work out how I want to build my guitars these are really just prototypes and if they do not survive more than a year or two they would have served their purpose.

[printer2]

Well just bent the walnut sides and went well. Easier than the cherry but then again they are for a larger guitar. Don't know if it is something I should advise, let's say it is something I tried and seemed to help. Towards the end I had a thought and while bending I would give the side on the pipe a quick spray of water. Not a lot but enough to make it look wet.

I think the water initially helps to conduct the heat to the side. But then I thought of wood that looses moisture on one side and not the other, the wood would bend or cup. So what if rather than only spraying the side next to the pipe but you give the other side a quick shot? I tried it on the cherry, the sides actually were quartered, could not find a piece wide enough for the back though. What I noticed was that when the water started to evaporate off the outside surface the wood was about the right temperature to bend.

Tried it on the walnut and it worked well. I actually had to make sure I did not over bend the side as it took little pressure to get the wood to move. Next set I will probably do with a blanket to see how it will turn out. But seeing I did three sets today I am not in a hurry to start another guitar.