Side bending question

[Alastair]

Hi all,

Wondering if the members have come across this before, and whether anyone has an explanation?

I was bending Northern Silky Oak sides for the current build. I had thinned them down to 2mm before starting.
Soaked the sides in a hot bath for about 30 min before bending, and probably did not have the pipe as hot as it should have been. The sides bent slowly, but with no tendency to fold or crack. However, they seemed to suffer strongly from spring back, and after I had repeatedly tried to push the bend further, only to have it go back after a few minutes, I gave up, intending to have another bash later, after they had dried out.
Lo and behold, when I came into my sun-warmed shed next morning, they had NOT sprung back; they had in fact increased the bend as they dried, even to the extent I’ll have to do a bit of straightening to get back to the template.


Any ideas?

regards

Alastair

[Craig]

That's rather strange ,( but incredibly handy ! ) Seems the wood couldn't wait to be made into a guitar !.

I read of a similar thing happening to Waddy Thomson a few weeks ago on the OLF Forum with his Sycamore.

http://www.luthiersforum.com/forum/view ... 01&t=33973

Crikey !, I'm off to check on my Silky Oak Stash !!


Umm, too late I'm afraid . All self bent , complete with venetian cutaway

[Alastair]

Hi Craig,

That link has it exactly, even to the amount of "spring forward"

Good to know I'm not losing my mind .

And a good choice

Now as long as the kitchen I built out of the same stuff doesn't get the same idea


regards

Alastair

[kiwigeo]

Now as long as the kitchen I built out of the same stuff doesn't get the same idea

Cool......a wrap around kitchen.

[Bruce McC]

Hi Alastair

A general question on side bending if you don't mind, as I have limited experience
with side bending and have only used a Fox type bender. Do you soak the sides in a
hot water bath because you are using a hot pipe or only when bending "difficult" timbers?

[kiwigeo]

Do you soak the sides in a
hot water bath because you are using a hot pipe or only when bending "difficult" timbers?

Depends on the wood. Most of my bending is with Indian Rosewood which bends relatively easily and the only water I put on the wood is via spray bottle.

[Nick]

When I first had a go (Mahogany sides over a pipe with blow torch up the guts, back in the dim dark ages) I was under the understanding that a good soaking was required. Over time I've found I've used less & less water on each sucessive set to the point now of just spritizing & bending over an iron & I only want to create steam at the point of contact between the wood & the iron. Curly Maple in particular cracks along the figuring if it's too wet.

[Alastair]

Hi Alastair

A general question on side bending if you don't mind, as I have limited experience
with side bending and have only used a Fox type bender. Do you soak the sides in a
hot water bath because you are using a hot pipe or only when bending "difficult" timbers?

Hi Afshar

Mine is about as limited.

Main reason for soaking was that in my first build, I had problems with scorching with only spraying, and found Silky Oak bent better when well wetted.
That said, this was perhaps too much of a good thing, as even after extended bending, the 'outside " surface was still dampish. However I would have thought that would cause more spring-back rather than spring-forward?

Don't get me wrong, I'm not complaining about the result. It was just that it was unexpected

Here are the sides after drying:

Off the pipe, the ends of the lower bout were at 45deg to the centreline

regards

Alastair

[kiwigeo]

Looks like lower bout on side nearest to camera has a sharp bend in it.....or maybe thats just the camera angle. You could try reworking it on the bender. The sides will often not quite cross the centre line at 90 degrees but dont forget you'll have a tail block in there to anchor the butt end of the sides to and then youll have supports on outside of the sides...Im assuming youre building spanish method here.

In summary I wouldnt worry about the butt ends of the sides but id probably work on the sharp bend in the side nearest camera....bearing in mind that Im completely anal when it comes to things like this.

[Alastair]

Hi Martin,

A combination of both;

There IS a sharper bend there, but it's nowhere near as obvious as it appears to be in the pic. I'll have no problem just relaxing it out when I get to refining the sides to the outline before glueing.

Building Spanish method, but without an outside mould. I'll get the sides close, and then clamp down like this:

but with more bars for the guitar, and tweak the sides to the template line. Using tentellones, so no glueing rush.

[Bruce McC]

Martin, Nick and Alastair.

Thanks for your responses.
Nice clean looking silky oak Alastair, is that a parlour size guitar your making?

[WaddyT]

Lo and behold, when I came into my sun-warmed shed next morning, they had NOT sprung back; they had in fact increased the bend as they dried, even to the extent I’ll have to do a bit of straightening to get back to the template.

Alastair

Interesting! I had a similar experience with my Sycamore bending. I did not soak the sides, but I did use a damp/wet paper towel over the iron to reduce scorching of the light colored wood. Bent them, set them on a form for a brief while, then set them off the form on my drill press table. Here are the results.

[Alastair]

Hi Waddy,

Would seem to be uncommon, but not impossible.
What I find interesting is the similarity of your sycamore to quartersawn Aus. Northern Siliky Oak!!

regards

Alastair

[Alastair]

Martin, Nick and Alastair.

Thanks for your responses.
Nice clean looking silky oak Alastair, is that a parlour size guitar your making?

Hi Bruce,

No, it was a soprano uke I built earlier this year, as a pilot build for this one. Finished build is in the gallery.

regards

Alastair

[woodrat]

Hi Waddy,

Would seem to be uncommon, but not impossible.
What I find interesting is the similarity of your sycamore to quartersawn Aus. Northern Siliky Oak!!

regards

Alastair

Hi Alistair, they both display prominent medullary rays on the quartersawn face. Both also are referred to as Lacewood in different places too. I think that Sycamore is either the same as London Plane or a close relative. ie. what they call plane in America...(?)
I am wondering if the medullary ray has something to do with it as a prominent ray is in them both and they are exhibiting a similar behavior when being bent.

John

[charangohabsburg]

I think that Sycamore is either the same as London Plane or a close relative. ie. what they call plane in America...(?)

Hi John,
This is what I found out after spending some time on wood names research:

Plane, Sycamore and Maple:
Platanus occidentalis, Platanus spp.: Sycamore (USA), Plane (GB), American plane, Occidental plane, Buttonwood
Acer pseudoplatanus, Acer montano: Sycamore (England), Plane (Scotland), Maple
Platanus orientalis: Oriental Plane

Maple:
Acer saccharinum: Soft Maple, Silver Maple, Swamp Maple
Acer saccharum: Hard Maple, Sugar Mapl – Birdseye Maple is an A.saccharum
Acer macrophyllum: Bigleaf Maple

Source:
My own "dictionary" of common and scientific wood names, the "Babylonadas", respectively the sources I mention there.
Corrections are welcome!

[ProfChris]

London Plane is Platanus x hispanica (or platanus x acerfolia) according to the UK Woodland Trust.

For the UK add in field maple, acer campestre.

I'd bet there are quite a few more - the Woodland Trust offers me Norway Maple (Acer platanoides) to complete the UK list, but I can't believe the rest of Europe doesn't have more species.

Sycamore and London plane are very different trees - I climbed lots of the former as a child, but only a few London Planes, and both bark and leaves are dissimilar.

[charangohabsburg]

Thanks ProfChris. Being obviously well known tree names they will find their place in my list.