I've Got The First Time Bending Blues

Even if it ain't broke you can still fix it.
tippie53
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Re: I've Got The First Time Bending Blues

Post by tippie53 »

make a waist caul use a large dowel don't just press with press screw that will create pressure points
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
Dobroguy
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Joined: Tue Jan 30, 2018 8:11 pm
Location: Anola, MB

Re: I've Got The First Time Bending Blues

Post by Dobroguy »

Thanks for your comments John. I watched your video on bending figured maple sides a few times before attempting my bend. I did use a waist caul and I also have the controller and other components from you.

My problem occurred when I tried to tighten the wing nut at the end of an eye bolt holding down the lower bout clamp piece and it kept slipping off repeatedly. The more I put it back in place & tightened it the more it kept slipping out of the slot in the block. I spent too much time trying to fasten it down and didn't realize the controller was set to full with the temp climbing higher & higher. I woke up when I smelt wood burning. Does that qualify me as being "woke"?

Anyway, I made new hold down pieces without a slot for the eye bolt. However, I intend to replace the eye bolt system with springs. That way I can avoid fiddling with eye bolts & wing nuts. As I said previously this was entirely my fault due to inexperience even though I attempted to do everything right.
bentHook.JPG
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Dobroguy
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Re: I've Got The First Time Bending Blues

Post by Dobroguy »

John, please clarify which of the following is correct, or does it matter?

In your updated bending video the sandwich layers from the bottom up are:
slat / wet paper / wood / wet paper / blanket / slat on top

In your reply yesterday to this thread the layers are:
slat / wet paper / wood / wet paper / slat / blanket on top.

Thanks for your help.
tippie53
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Re: I've Got The First Time Bending Blues

Post by tippie53 »

we are here to help
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
Morecowbell
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Location: Fishers, IN

Re: I've Got The First Time Bending Blues

Post by Morecowbell »

DG - Here's my setup in case it might be helpful. My center caul is much larger than necessary but you get the idea. The springs on the hold downs are a big help. If springs are not readily available bungee cords might work?

This was my first bend and I used aluminum flashing which worked, but I have spring steel on the way from John. IIRC my sandwich went like this, from the top down to the form: flashing/blanket/flashing/paper/wood/paper/flashing.

I used butcher paper and tap water. As John mentions ammonia is a traditional plasticizer for wood bending - I haven't tried it yet but I also haven't bent figured maple sides yet.

One other thing that I found helpful was having some additional depth on the form, say 1"-2" past the centerline of the body, so that the ends of the side have some space to lay flat past that point.


20200307_181911.jpg
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"Facts seldom sway an opinion." - John Hall
"The difference between theory and practice is that in theory there is no difference." - Van de Snepscheut
Stray Feathers
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Re: I've Got The First Time Bending Blues

Post by Stray Feathers »

I looked long and hard for springs when I built mine, and then later discovered that local auto parts stores carry an assortment so you can play with them to figure out what might work.

And for the record, here is my bender. There are extra springs because i use it also to bend ukulele sides, with a sort of plinth to raise the smaller uke form so the cauls can fit over it. I tried several different "layer" configurations but now use a spring steel slat on top, then the blanket, then a third slat (just flashing) between the blanket and wood (I sometimes get light scorch lines from the heating elements in the blanket) and dampened kitchen parchment on both faces of the wood, and another spring slat on the bottom. Bruce W.
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Dobroguy
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Re: I've Got The First Time Bending Blues

Post by Dobroguy »

Thanks for the help & inspiration everyone. Here's where I'm at now:
I will add some ammonia to the spray bottle.
I do have a full width caul for the waist bend.
I also have some wood crosspieces under the body centerline at each end for extra side support.
I will definitely use springs to hold the end clamp blocks in place. It was a bad mistake for me to use the fiddly eye bolts in the first attempt. It is too cold here today for me to venture into the city looking for springs but next week should be good.

Here's a shot of my set up. The jig is clamped in a swivel vise for easy access to both ends.
bending.setup.JPG
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MaineGeezer
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Re: I've Got The First Time Bending Blues

Post by MaineGeezer »

Just for reference, if you can't find springs locally, try https://www.mcmaster.com/ . They have springs...and everything else.
Don't believe everything you know.
Anything is possible if you don't know what you are talking about.
When things are bad, try not to make them any worse, because it is quite likely they are bad enough already. - French Foreign Legion
Dobroguy
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Location: Anola, MB

Re: I've Got The First Time Bending Blues

Post by Dobroguy »

Unfortunately, McMaster Carr won't ship to me as I am in Canada. I found that out when I tried to order the pulleys & V Belt I needed when I built my thickness sander.
Stray Feathers
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Re: I've Got The First Time Bending Blues

Post by Stray Feathers »

I have seen the springs at Lordco and Bumper to Bumper in the small town where I live - in Canada - and also some pulleys etc. I've also found Home Hardware pretty good if you search their web site.
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