Advice on my first bending project

[CaptainSawdust]

Hi everyone, wondering if I could ask for some advice from the exceptional craftsmen and women out there.

I'm about to start my 1st ever project involving bending timber. I'm planning on using green oak because I know that it's quite flexible but wondered if I should use steam bending or bent lamination? The stock I need to bend will only be about 3/4" thick.

What would people advise?

Thanks

 

[custard]

If green Oak is what you've got then you only have one option, steaming. Laminating wet wood isn't a great idea as the moisture content will exceed the guidelines for the adhesives you're likely to want to use.

Steam bending a 3/4" section of green Oak is pretty straightforward, but you will get more spring back and drying distortion than you would with lamination. On the other hand with steaming you won't have all the glue line issues that lamination brings.

Really depends what you're making, the radius involved, what finish you expect to use, how precise the component needs to be, how many you're making, etc. It's not the case that one method is always better than the other.

 

[CaptainSawdust]

Thanks Custard. I'm aiming for to make a guitar stand very similar to this one

http://photo.foter.com/photos/pi/243/st ... -stand.jpg

So steam looks to be the way to go. Any advice on how long to leave it in the form to dry? I appreciate there will always be some spring back so I'll need the form to be a slightly tighter curve than i ultimately want.

 

[custard]

How lovely, what a great project.

It looks a lot thinner than 3/4" in those photos. Personally I'd laminate this, but I guess you could try steam bending. The lower of the two components that form the "S" shaped spine would be easier because it's secured at both ends. Spring back on the top most component would be trickier because it's free to waggle around at the top end in any way it wants (which is why I'd laminate). The base unit/feet and other components are all cut from the solid, you'd need perfectly dry wood for these parts or as it dries they will twist and the stand will then rock.

To answer your question, 24 hours in the form is the very minimum, a week is better.

Yeah, thinking again I'd definitely laminate. Glue lines wouldn't be too much of an issue because the edges of the curved components are square, in other words you're not overly exposing the glue lines by cutting a curved profile on the edges. Plus lamination is the best way to get a really strong, rigid, but thinner component. The UF glue you'd use for lamination dries glass hard, so imparts it's own stiffness into a structure. Take the top spine component down to a steam bent 1/2" and it would be awfully whippy, make it 3/4" and it might look clunky and top heavy.

There's a lot of work in this project, don't be driven by the fact you happen to have some green Oak on hand, there's only a few quid of timber needed for this project so material costs are totally negligible compared to your time and effort.

Just my top of head thoughts.

Good luck!

 

[CaptainSawdust]

Wow. Thats really helpful advice. Thank you very much.

I'll hopefully add a couple of build photos in the projects section of the forum as I go.

 

[RobinBHM]

Somebody told me recently that steaming can be done by putting the workpiece in a layflat plastic tube (the stuff that heat seal bags are made from). Apparently the workpiece stays in the tube with steam connected whilst it is bent and clamped.

 

[profchris]

I think the feet are sawn, so it's only the "neck" part which is bent, and that looks around 6mm to me.

I've bent oak for a ukulele at 2mm using a hot pipe (3 inch steel tube with heat gun in the end) and my oak bent really easily. If I were making this I'd bend two 3mm pieces and laminate them. (or if 3mm wouldn't bend, three 2mm pieces).

 

[deema]

If you have enough stuff why not have a go at both? Steaming oak is very easy, allow about 1 hour over 1". I use a bit of plastic pipe with rags stuffed in either end and either a steam wall paper stripper or a domestic steam cleaner as a source. You don't need a steam box unless your bending very thick stuff.

You will need to make a former which can be used for either process. When steaming you need to have some Spring steel to support the outside edge to stop it cracking. I often use the steel straps that come off wood packs or anything similar for this purpose. I make the stuff over length and screw the steel banding to it. Pop it into the steamer for the allocated time and then bend. Once cool either tie the ends together with twine for a week to stop spring back or like Custurd highlighted leave in the former for at least a week (remove the steel back as soon as possible). You need to get it really dry to hold its form. Under the bed, airing cupboard, anywhere there is a constant uniform low humidity environment. Do not place near any direct heat forms.

A last nite, the grain needs to follow th curve, slab cut stuff is best IMO. If the grain rises to the surface, you must make this the inside against the former to stop it splintering when formed. For double curves the rising grain should be in the inside of the tightest curve.

Allow for about 10% Spring back. I.e. Radius required is 10" make the former 9"

 

[yetloh]

I've done quite a bit of steam bending and your green oak is ideal. Although it adds time to the process I would go with a steam bent lamination of just two plies. That way you will get much better grain continuity than with multiple laminates and much less springback than with solid steam bending. Rip your board with a new thin kerf blade (Tuffsaws do a good one) on a carefully set up bandsaw and then plane each face just enough to remove the saw marks. This will minimse wood loss and therefore have minmal effect on grain continuity as long as you keep the two pieces in register when you glue. You will need very well matched formers - a single former with a steel strap is easier for single crves but won't work where you have two curves which bend in opposite directions. Gluing is no problem with green wood as long as you use polyurethane glue and well matched formers will ensure a tight glue line. Good luck with this project, I have had great enjoyment making freeform curved chairs using this method and am very pleased with the results.

Jim