Official Luthiers Forum!

Hi all,

This is my first post, so please play nicely! To set the scene, I'm new to the game of luthiery, this project is my 4th and most demanding and troublesome. 1,2 & 3, although not without fault, in my opinion sound and feel much better than they really should! On to the matter at hand:

I've had a bit of bother with some flamed sycamore. My first attempt was a complete shambles. I tried to bend figured timber with the same principles which had worked so nicely before with EIR & walnut I quickly learned that thickness, or lack thereof, is paramount and that water/steam needs to be used sparingly with figured timbers. Both lessons I could have easily avoided if I'd just been patient, researched and checked the various advice before plunging head first. Stupid. On the plus side by the time I'd bludgeoned my way through my last bout, I felt I had the measure of it.

My second attempt, however, has me confounded. On the first side, I started the bend at the upper bout and worked successfully, and slowly, past the waist and into the lower bout. Almost instantly I realised something wasn't right. A ridge (and it's hollow on the reverse face) had appeared in the side running along the grain. Baffled, I started on the other side, but this time starting from the lower bout. Exactly the same problem. Pictures might help here:


This is the face that was in direct contact with the bending iron.


The reverse/outside face showing the hollow created. Way beyond sanding-out-able.


Here you can see the burnished ridge line which follows what appears to be a fault in the grain (just visible).

I can’t, for the life of me, fathom why this has happened. I speculate that the timber, with this perhaps softer grain ‘fault’, (I say softer because the grain lines appear to be noticeably further apart in this area) heated at a different rate to the timber surrounding it causing it to distort irreparably.

Perhaps the iron was too hot? The discolouration along the ridge might suggest this conclusion, but on the first side I had successfully bent the upper bout and waist before discovering this defect in the lower bout.

I was bending dry, with only the occasional spritz at the waist, as I discovered before that wet figured timber isn’t best buddies with a hot bending iron. The sides had been thinned to a uniform 2mm. Too thick? What’s to be learned? Does some timber simply refuse to be bent? Would a heating blanket/mold method be more successful?

All is not lost as I may be able to salvage enough of the sycamore side to furnish a thinline archtop guitar I have planned

I have, in the mean time, continued to progress no.4 with a fresh set of walnut back and sides. mmmm, walnut.

If anyone has any input, I'd be glad to hear it!

Sanchopanza

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Hmm, is that quartersawn? Usually that bends nice and evenly, unless it's a tropical wood with interlocked grain, which tends to ripple with each direction reversal.

Flatsawn woods always like to cup.

For the scorching, put a paper towel over the bending iron and spritz it with water to keep it from burning up. Also steams the wood and makes it bend much more easily... although I haven't tried bending full width sides with curl like that yet, so it is possible they won't like the water, in which case I guess you'll just have to try and keep the scorching shallow enough to sand out.

And for the cupping, you can take a block of 2x4 or whatever and press the side onto the iron, to force it all to make contact and bend, rather than just the peak of the ripple (which only makes things worse as you keep going). It's kind of tricky manipulating the block while pushing down in two places to bend the wood as well, but it worked great on some flatsawn spalted maple sides I did recently. Give it a try and see if you can save that one. If nothing else, it'll be good practice for the future.

Hi Dennis, thanks for your reply. It looks nicely quartered, and it's not so much cupping which you might expect from flatsawn, it's more pronounced and localised. I didn't have any problem with scorching, but I like the method you suggest with the paper towel. I'll try and remember that for next time. I tried 'forcing' the whole side to be in contact with the iron, but it didn't seem to rectify the situation.

Has this happened to anyone else?? Or is it just me?

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I'm afraid I'm no help, but just wanted to chime in and say that I've been to your site and you have some very nice work there... I loved your first guitar, well done!
Wished my 1st was half as good...

Cheers
Miguel.

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member of the guild of professional dilettantes

Thanks For the kind words Miguel. I spent hours agonising over that design!

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http://lovanen.tumblr.com/

I don't have enough experience to know for sure, but I'd like to ask about your bending iron setup. Is it homemade or store bought? I'm wondering if it's not evenly heating your wood, or if that could even be a reasonable explanation? It looks like the ridges created are a bit scorched, and I'd think maybe those areas could have shrunk just a little, or been burnished, inducing the peaks on the outside?

From your photos, it appears that it's clearly associated with the darker streaks running through your sides. On the inside of your bend, your straight edge is resting on the dark streaks. On the outside, they are cupping away (below) your straight edge. Now, why this is happening I can't say for sure, but the darker wood is definitely reacting differently.

I can offer suggestions, but it's hard to say whether they will help, so experiment if you have some scraps on hand. Try a backing strip of aluminum or heavy canvas, with or without a VERY light spritz of water on the side touching the iron, and get your iron hot enough so the water drops dance and flash off to vapor almost instantly when you spritz the iron. If you spritz the wood, do it lightly. Just enough to make some steam when it hits the iron. Too much water can make the problem worse. Go slowly and don't worry too much about light scorching--it will sand off (obviously, there is a difference between light scorching and charred wood, so check often as you go along). I hope you can solve the problem, because it looks like some beautiful wood.

Looks to me like the dark streak cooked faster and shrunk.

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Old growth, shmold growth!

Looks to me like the dark streak cooked faster and shrunk.

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Old growth, shmold growth!

what are the thickness of the side ? How much water did you use ? Also did you use a slot on top to help ? Cupping will happen and you do have some room for sanding later. I often bend at about .095 then that lets me .020 to thin out before finish. If I Have to "finish fill " areas later I will , It is all about working with the wood and learning what you can do , and what you have to work with.
Wood is not homogenous always across the grain so you have to learn to work with it and read the wood. I will also say that 80% of wood bending is wood selection. Not all thin wood will make a guitar. There are many hidden things one has to learn to look for. Then there is process. Learning the process of bending isn't that hard but it does take patience.
I do use Super soft on wood that may be problematic. Water and heat can also play a part. Some wood prefer more heat and less water , some more water and less heat . Sycamore is usually an easy bending wood but you have to be careful of the sap wood , and water. Try a little less water and more heat.
Experiment , it is one way to find out what does and doesn't work.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Hi John,

I had the sides down to 2mm (about 0.08) as I had trouble with the waist previously. Like I said, once I got the hang of bending dry with only the occasional light spritz (twice, once in the upper bout and once at the waist) I found that the actual bending of the sycamore went quite smoothly. I had a big grin on my face until I reached the lower bout and discovered this bizarre distortion.

I hear what you're saying about the selection of the timber being so very important. I think this is something which I have to take forward. I live in a remote part of the UK and we have ZERO local luthier suppliers and so for the time being I have to trust to my supplier (at the opposite end of the UK) in his selection of timber. I saving up for a big trip up north to come back with a car full of potential guitars.

The other thing you mention is a "slot" (presumably spring steel slat?), the only source I can find online is Stewmac, and with the hefty shipping charges to the UK, I'm waiting until I can order a few things together to ease the pain. A few people here seem to swear by the backing slat, I can imagine the benefits. At the minute, I just use an offcut of 2 x 1 ash held perpendicular to the side in my right hand to even up the bending pressure. Works a treat with walnut!!

I have no idea what Super Soft is.

Reading the timber... this will come in time and experience I'm sure. I'll admit I didn't give the side more than a cursory looking over before I started bending. This is definitely going in the notepad in big BOLD TYPE!!

Anyway, thanks for all your input, it's invaluable. I'll try and put up some finished photos of this guitar as and when I'm done with it. I'm closing up the box tomorrow, before an untimely Xmas break

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Hi
Supersoft = veneer softener, searching the forum will throw up lots of results.
http://www.veneersupplies.com/products/Super-Soft-2-Veneer-Softener-Conditioner.html
I'm in UK (on the dark side - Scotland) and have some to spare in the classifieds.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.