need help with bending problem on first build

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suniram

Posts: 50
Joined: May 18 2010
From: Germany/Spain

need help with bending problem on fi...

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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http://marinusbenedikt.wixsite.com/marinusbenedikt
http://www.flickr.com/photos/marinus-benedikt/

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 10 2012 13:15:43

Flamingrae

Posts: 220
Joined: May 19 2009

RE: need help with bending problem o... (in reply to suniram)

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.

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 10 2012 13:40:43

suniram

Posts: 50
Joined: May 18 2010
From: Germany/Spain

RE: need help with bending problem o... (in reply to suniram)

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

_____________________________

http://marinusbenedikt.wixsite.com/marinusbenedikt
http://www.flickr.com/photos/marinus-benedikt/

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 10 2012 15:44:17

Andy Culpepper

Posts: 3023
Joined: Mar. 30 2009
From: NY, USA

RE: need help with bending problem o... (in reply to suniram)

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.

_____________________________

Andy Culpepper, luthier
http://www.andyculpepper.com

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 10 2012 21:26:24

suniram

Posts: 50
Joined: May 18 2010
From: Germany/Spain

RE: need help with bending problem o... (in reply to suniram)

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

_____________________________

http://marinusbenedikt.wixsite.com/marinusbenedikt
http://www.flickr.com/photos/marinus-benedikt/

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 11 2012 9:31:46