Bending

[Ragamuffin]

Ok, I'm sure threads like this have gone around before, but I could not find anything doing a search so I'm reaching out. #I have been practicing my bending technique on a hot pipe with marginal success. #Some times it seem to go pretty well, and other times not. #I'd love to know how thick others are dimensioning their rims prior to bending, and what tricks you all have learned in getting highly figured wood to bend without splitting or breaking. #I have tried various soaking times in hot water and use an aluminum strap, but I just don't feel like I'm getting the groove. #Any help would be greatly appreciated.

Regards,

Steve Ragsdale

[sunburst]

Most people are using sides anywhere from .060 inches to .090 inches. (about 1.5 mm to 2.3mm)
Some wood is too figured to bend. Selecting the wood is important. The grain needs to run fairly straight down the length of the wood so that it doesn't break as easily. The thickness should be very even, and the surface should be pretty smooth.

Soaking curly maple for too long can make it easier to break.

Your aluminum strap can help. The right temperature for the pipe is important too.

Different people find that different things work for them, but here's what I'm doing these days;

I heat my pipe a little hotter than I think most people do. If I stay too long in one place on my side, it will scorch.

I keep a wrung-out wet sponge on the bench, and occasionally dampen the wood. I don't soak the sides at all.

Lately I've quit using a bending strap. I found that I don't need it if I just slow down. I have to keep moving, because, like I said, my pipe is hot and will scorch the wood.
What works for me is to bend the wood the amount that I can easily, not pushing too hard, and if it isn't enough, let it cool a while, and bend it some more.
I can go back to a tight bend several times and it will bend a little more each time. I'm sometimes surprised how tight I can get some pretty darned curly maple to bend.

Practrice does help, so keep doing that.

I used to make the parts of the sides where the tight bends are thinner than the rest, but I've quit doing that. I sand them to .070 or .080 in. the whole length, and bend them slowly.

Good luck, keep at it, have fun!

[onthefiddle]

One common mistake, if you're using a bending strap, is not pulling hard enough. The strap is there to support the rib as you're bending - preventing cracks, but if you're too nervous about it then the strap can't do it's job.

Wrap a damp cloth around the bending iron, then use a strap - pulling hard - to get the rib close to the final shape. The cloth will dry out quite fast, but you should have the rib basically in shape by then. Then dispense with the strap and the cloth, and make final adjustments more gently on the dry iron.

The way I was taught to find whether the iron is up to temperature is to put a little drop of water on it - if it sizzles then it's too cool, it should form into a little bead and then bounce off.

Aim to get a rib to sit perfectly without springing it into place, dry bending is certainly advantageous - as it results in a much more stable rib that will just sit there perfectly in shape, though I wouldn't recommend it exclusively if you're just starting out.

I agree with John regarding soaking ribs - they're more likely to crack, and if they're highly flamed then they can go very wavy.

To echo John - practice makes perfect!http://www.mandolincafe.net/iB_html/non-cgi/emoticons/smile.gif

Good luck!

Jon

P.S. One final tip - the heat is helping you to bend the wood, but the iron is heating the inside of the curve more than the outside - while the fibres of the outside face of the rib are being stressed more by the act of bending than the inside (you'll notice that the ribs are cracking on the outer face of the bends). When dry bending try heating the outside face of the rib against the iron before bending the rib more.

P.P.S(!) One absolute and final tip (for the moment) - aluminium isn't such a good material for a bending strap, as it tends to deform and crease, the rib isn't supported where the strap isn't touching it, so can crack. Try making one up out of spring steel, with D shaped wire handles to feed the rib through. Alternatively you could use a leather strap (an old belt as long as it's wide enough).

[Ragamuffin]

I thank you both kindly for your input. I will put your advice to practice.

Fond regards,

Ragman

[Ragamuffin]

John,

This is making sense to me now. Some of my problem has been that I have been following Siminoff's guidance to thickness sides to .125...very near impossible to bend. When I thin things down a bit it is indeed much easier. I'm going to give a go at .80 and see how that works for me. Thanks again for your input.

Steve Ragsdale

[topcat]

Steve,
I bent my first set of sides just a year ago and went through the same agony. How thick, how hot, how wet and after a week of attempts and cracked scroll areas got it nailed.

Thickness to 1.8-2mm finished to 180 grit (easier cleanup of glue later as well as no risk of cracks following coarser machine marks).
Don't soak figured maple - it just comes apart at every ripple. Get a little hand spray bottle, the sort for misting plants are cheap an superb and spritz the wood immediately before you bend. Only spray the area you are going to bend at that time. The spray bottle works for testing how hot the bending iron is water should dance on it as Jon described above.
A bending strap - ideally very thin stainless steel like what Stewmac sells.
Leather gloves (clean) so you don't burn yourself and you can get a ggood grip of the steel strap against the wood - any gaps when bending willl result in cracking.

Then 30 seconds of madness - spray the wood at the area , grap the strap and push like hell against the iron. Thumb and pointer pushing down on the strap over the iron to get it started then grabbing the straps and wood slightly further out once it gets going. This is essential for the small radius of the scroll. I kept cracking this area all because I was not using enough force and trying to do it in stages. I do the scroll then the waist then all the rest of the long piece as 3 distinct operations. Once you get you first finished lift it off the iron holding the set (radius) as still as possible for about 30 -40 seconds. This will set it enough to move to the next area.

Bravery is the word- if you are not committed you won't get that first scroll in one go. I got so frustrated when testing as I was pussyfooting my way trying to make tighter radius then going again to the finished radius and it would crack. I was spendin the best part of an hour, the sweat pouring off me as I worked nervously around. Then once I went for it it was under a minute for the scroll - less than that for the waist and bout 2 -3 minutes working my way around to the lower point. Then bung the shape into your form immediately and clamp it for 24 hours. Make sure your inner and outer shapes of your form are a good match - if the inside of the scroll is not properly supported or there is a sharp point on the inside it will crack. This happened with the first success off the iron as soon as you move away from an area it start to uncoil a certain amount so if its left the radius may have opened too much to be pulled back by the form.
If your form is in 4 outer pieces you can just do the scroll and waist then clamp it and take a break. I did this because the process was so nerve wracking when I got to that point I reckoned the rest of the large radius of the body could be left to another day.

I tried to do it with and without the leather gloves. It is quite clumsy with the gloves but I couldn't get the proper contact of the wood with the iron. If it's not touching the iron it won't bend it just cracks. Actually as the wood goes around the radius the U area between my thumb and pointer was used to hold the contact agianst the iron. I also kept rotating the wood around so that I was always eyeballing the new contact area with the iron.


I found the more you bend the wood the less chance you have of coming back and tightening the radius.

I used about 4 lengths of side wood before I got it nailed. I have used what was left of these sides to bend the 2 smaller pieces so these beautifully figured pieces of wood didn't go to waste.

Good Luck- be brave.

Terry Cromer

[Ragamuffin]

Terry,

Many thanks for sharing your experience so thoroughly.

Regards,

Steve Ragsdale

[mandomaniac]

Then there is always 21st century bending.....:laugh:
If you get tired of the frustrations inherent in the hot pipe ...check out my add in the classifieds (search heat blanket bending system) as well as search for Heat Bending Pictorial in this section (from beginning).
Not to say many folks are happy with the hot pipe approach...just more than one way to skin a mando.
Tom