Steam-bending red deal~~question

boatbuilder

Hi,

I have a project in mind that would involve a 70mm x 10mm length of red deal being bent at one end by 180 degrees in an 8 inch radius.

Anyone have any thoughts on this? I've considered laminating two 5mm strips glued together with PU glue, but even then it could be tricky to get it to bend nicely without breaking. Ideally I need some technique that is easily repeatable and fairly fast to do.

recipio

No experience of steam bending but I've done plenty of laminating.I take it your dimensions are 70mm wide x 10 mm thick x about 410 mm long which will give you a 16 inch long semicircle, 8 inch radius, when bent.?
Its a tight radius and I'd guess 10mm is too thick, but you will probably make it at 5mm. Allow extra length for trimming. You will need to make a former to glue it around.Its not too difficult, bandsaw a piece of MDF or ply ( you will need to glue up layers to 80 mm wide ) to your radius. Refine the cut surface on a sanding disk or drum machine if you have one.If using 5mm to finish at 70 wide I'd use 80mm as the layers always slide a bit and need trimming when set.
Screw the entire former to base, get at least 10 'g' clamps and start laminating ! Ordinary PVA glue is fine but its best left overnight.
Red deal is not ideal ! - it tends to split at the knots. Ash or beech would be better but all bending is a bit of trial and error. Expect about 3% springback when the clamps come off but laminating gives a very strong result.

dubtom

I've been steam bending lately using a pvc 4'' pipe and a vax steamer. With wood thicknesses of 10mm or so I've had no problems, over that,and my intention was to bend ¼'' wood in a 42' radius, that's an 11'' circle basically. Anyway,I failed, basically because I used a wood, not sure what type,but it had too few grain,as red deal would. It is done though,in my case the end product was to be a banjo rim,which are usually steam bent in ¼'' thicknesses and then 3 glued together to achieve the finished rim before turning. Any checks or knot in the wood will make it more liable to snap, which is another reason mine failed I guess. From what I've read on the subject, the desired steamer should be totally enclosed,pressurizing the steam into the wood, after 45 minutes or so the end result should bend like rubber, my thin wood did,thicker wood not so much. In saying all that though,I tried to achieve a full 360, 180 may be an easier.
Sorry for babbling on, it's a pet subject of mine lately.:o

boatbuilder

Thanks for the reponses.
I have been doing some experiments actually, with a mind to going into larger scale production of a certain product....I made up a steam box from plywood and used a wagner wallpaper steamer to provide the steam. I tried bending some ash and broke about a quarter of the pieces, I think mainly due to weaknesses in the grain. The springback from the steaming is different on each piece of wood as well.
Ash is too expensive to make mistakes like that so thats why I was wondering about read deal and also laminating instead of steaming.

slowburner

How thick was the ash?

boatbuilder

It was about 8mm thick x 70mm wide. I think I may have steamed it for too long....over an hour.

slowburner

Strange that you had 25% failures. Maybe the grain was wild or knotty? I'd expect maybe 10% failure with straight grained ash at 8-10mm thickness.
Wouldn't expect quarter as much success with red deal even if it was clear and straight - which I don't think I have ever seen.
May the Gods of steam smile on you!

recipio

Apologies, on re-reading your post you want to bend one end only, like a hockey stick ?
Whatever method you choose you will need to make a former and I think mdf would disintigrate if using steam.Solid wood is best.
Air dried wood is preferable to kiln dried as the lignin in the wood cells is not hardened as much. Overall laminating is more controllable, assuming you don't mind the look of the laminations.

dubtom

Apart from wood type, I'm thinking that a lot of my failures are actually linked to the method of steaming itself. As I said earlier,the proper method, by those that do it constantly, is in an enclosed metal chamber, with pressure inside reaching 60lbs a square inch. With my pvc pipe,I have constant steam leak,probably lucky to reach 5lb pressure, which I suppose doesn't give the wood enough steam to soak in to the core,unless of course it's really thin.
I would imagine your plywood soaks up the steam as much as my pvc leaks it.
I intend to make a proper metal box when I get time, it doesn't seem to complicated, metal tube,enclosed one end,door of some sort on the other, release valve just in case,a rubber tube connected to the steam source.

fergal.b

Try soaking it in water for a few days and then steam it, on my boats even when I am bending I keep the wood raped in hot wet towels.
Here are a few old videos from HANDS you might like building the shannon one boat, at the end of the first video it shows how they bend their wood.
http://www.youtube.com/watch?v=XthOkO-wsK4&feature=player_embedded
http://www.youtube.com/watch?v=XELPt_x08Os&NR=1
http://www.youtube.com/watch?v=dPNePCOZSZo&feature=related

dubtom

Actually I've just been reading about a guy who just soaks his wood for 3 or 4 days and then bends it cold. Seems to work as well, the same rules apply for straight grain and no knots.

boatbuilder

dubtom wrote: »

A
I would imagine your plywood soaks up the steam as much as my pvc leaks it.
I intend to make a proper metal box when I get time, it doesn't seem to complicated, metal tube,enclosed one end,door of some sort on the other, release valve just in case,a rubber tube connected to the steam source.

I suppose I could line the box with tin foil

boatbuilder

I tried aother couple of bends today and both were a success. I think I oversteamed the first pieces. I also paid more attention to grain direction and pattern. Had a very slight bit of "checking" on one piece, but nothing that won't sand out.

slowburner

Any thoughts on what a 10" concrete pipe would be like as steam chest? My old wavin pipe chest has retired - I used to keep it on the roof of the workshack but it blew down and shattered :eek:

dubtom

slowburner wrote: »

Any thoughts on what a 10" concrete pipe would be like as steam chest? My old wavin pipe chest has retired - I used to keep it on the roof of the workshack but it blew down and shattered :eek:

How would you enclose one or both ends, I'd imagine it would be really heavy.

boatbuilder

I'd say it would take more time to get up to a decent temperature.

boatbuilder

Just an update on this..... today I managed to bend the 12mm thick red deal into the 8 inch radius.
Heres how I did it....I rip-sawed the "bending part" of the wood into three equal thin sections on the bandsaw...the blade took off maybe 2mm on each pass so each of the three laminates ended up about 2.6mm thick.
After cutting, I steamed it for half an hour and it bent really easily aroung the form. Not dancing a jig just yet, as it may have been a fluke! Knots are gonna be the biggest problem. Should be plenty strong when its all glued up with PU glue. I'm also thinking that some of the "knot problem" may be alleviated by using a metal backing strap to support the wood while its being bent.

boatbuilder wrote: »

Hi,

I have a project in mind that would involve a 70mm x 10mm length of red deal being bent at one end by 180 degrees in an 8 inch radius.

Anyone have any thoughts on this? I've considered laminating two 5mm strips glued together with PU glue, but even then it could be tricky to get it to bend nicely without breaking. Ideally I need some technique that is easily repeatable and fairly fast to do.