need help with bending problem on first build (Full Version)

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suniram -> need help with bending problem on first build (Aug. 10 2012 13:15:43)

Hi All,

i am having serious problems to get the waist bent on my cypress sides. i am using a bending iron .

i got the first one completed yesterday, and its quite good now, but after a very long struggle and with a little crack (similar to the one in the fotos)

now i am trying the second side, but no chance. i first tried it very slowly with little pressure but as it would not work at all i applied more and more pressure. but this thing doesnt want to move. and now again some cracks are starting to appear (see fotos). i really dont know what i am doing wrong. too much water, too less? too much pressure, too much heat? no idea...

what can i do? please help !! :)) i am getting desperate

best regards
Marinus





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Flamingrae -> RE: need help with bending problem on first build (Aug. 10 2012 13:40:43)

quote:

what can i do? please help !! :)) i am getting desperate


Fret not - (at this stage!!)

1/ how thin are your ribs, if they are about 1.8 to 2mm you should not have much trouble.
2/ if you use a bit of water this can help.
3/ I use a piece of paper between the rib and bending iron to stop scorching.
4/ maybe try to let the rib heat up a bit more before try to bend
Where you are now,
the cracks - you'll have to glue at some stage and you might have to do a bit of glueing - then bending and maybe a bit of clamping to a former. When you are bending you can use a piece of metal shim on the outside to stop the wood splitting further.
I'm sure there are other ways that some of the others can offer too.



suniram -> RE: need help with bending problem on first build (Aug. 10 2012 15:44:17)

thanks a lot,

i got it almost to shape now and have it clamped to a jig. but i am sure there will be a lot of spring back... so probably i will have get back to it.. :(

but i am really wondering why this goes so hard. before i started with the cypress side i practised with some waste-ribs which i got from madinter (not sure which wood it really is as they didnt specify it, but i think it might be sapele) and had no problems at all with them..

maybe i applied to much heat. anders said in another threat that if cypress gets to hot it gets stiff and wont move further (did i get that right?). no idea

it would be interesting to know how much time you guys need to bend a waist. in the dvd "el guitarrero" anders seems to put the wood into the bending machine and in a few minutes press it into shape.
i just have no idea which pressure must/may be applied



Andy Culpepper -> RE: need help with bending problem on first build (Aug. 10 2012 21:26:24)

If that were happening I would just go ahead and thin that area down some more.
It's easy to tell if you've applied too much heat to cypress: it will scorch, sometimes quite deeply.
Anything up to that point is not too much. In the 350-400 degree range on the bending iron will get the job done, and applying some water is a must IMO. It will scorch at 450+

Getting a good hand bend is a combination of factors: stiffness, temperature, pressure, moisture, time.
With experience you will just be able to feel all of those things.

When using a bending machine you can press the side into a bend in a matter of a minute or so. However I found that I would still have to fire up the bending iron the next day and adjust the bend for springback, so now I just bend by hand and probably actually save time.



suniram -> RE: need help with bending problem on first build (Aug. 11 2012 9:31:46)

Thank you Andy,

I redid both sides today and it went much better. I applied a bit less heat, but a lot more pressure.

I think that my error actually was to be too scared to apply enough pressure. Therefore nothing seemed to move. The cracks might have appeared when I finally, getting desperate, applied the right pressure but while having the wood either too hot or to cool....dont know.
I glued the cracks a bit and its perfectly ok now.

Anyway this was kind of a horrible experience, probably also because of the the nice temperatures we are having here in Madrid right now. In my workshop (=bedroom=livingroom) the temperature at 8 AM is about 32° Celsius, in the afternoon rising to 35°. So the sweat dropping from my face was almost enough to get the wood moistened... :))

Thanks a lot for your advices

best regards



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