Build thread - Blackwood & Bunya Dreadnought
Re: Build thread - Blackwood & Bunya Dreadnought
My first journey into side bending is a partial failure. I was worried about breaking it, I burned it instead.
Attempt #1 was stained in blues and greens. I used boiled tap water, apparently that is not enough.
This pic is of attempt #2, I could not find distilled water anywhere, so I used mineral free water. Big difference with only a small amount of water/mineral staining in comparison, however the second time I had the wrong probe hooked up and before I realized my mistake I'd over baked the waist.
After lunch it seems I'll be cutting more Blackwood.
The second attempt I tensioned the screw adjustments a lot tighter and the metal sheet didn't buckle like it is in this first pic.
Attempt #1 was stained in blues and greens. I used boiled tap water, apparently that is not enough.
This pic is of attempt #2, I could not find distilled water anywhere, so I used mineral free water. Big difference with only a small amount of water/mineral staining in comparison, however the second time I had the wrong probe hooked up and before I realized my mistake I'd over baked the waist.
After lunch it seems I'll be cutting more Blackwood.
The second attempt I tensioned the screw adjustments a lot tighter and the metal sheet didn't buckle like it is in this first pic.
Re: Build thread - Blackwood & Bunya Dreadnought
A wash with oxalic acid will often get rid of the worst of the staining.demonx wrote:My first journey into side bending is a partial failure. I was worried about breaking it, I burned it instead.
Attempt #1 was stained in blues and greens. I used boiled tap water, apparently that is not enough.
Martin
Re: Build thread - Blackwood & Bunya Dreadnought
I had the same problem with burning the first time I used the blanket too. I wound the temp right down and found that mine easily bent at 200F, I know the recommendations on here are 280F but it started smoking at that temperature for me.
Col
Col
Re: Build thread - Blackwood & Bunya Dreadnought
All the instructions I've read and videos have said 320F and bake at 260f !!! Are we using the same bender & controller?
I've been doing some test runs using sides I've cut up to practice. The blackwood wasn't meant to be a test run, but it quickly became firewood!
I've solved the burning issue, fingers crossed it doesn't happen again. First time I burned was because I had the probes too far out. Second time was because I had the wrong probe plugged in.
I've "mostly" solved the water discolouration, it is still occurring but not as bad as it was. The third bend I did had zero burn and a little water marking.
The issue I'm trying to eliminate now is I've been getting a warp/buckling either side of the waste. I've just done a practice side with a bit less water and I made sure to let it bake at 260 for 15 minutes and I'll let it cool down a lot longer before I remove it. Actually I'll just leave it in overnight as I'm not going back out there again tonight!
Hopefully that solves the warping. If not then I'm out of ideas
I've been doing some test runs using sides I've cut up to practice. The blackwood wasn't meant to be a test run, but it quickly became firewood!
I've solved the burning issue, fingers crossed it doesn't happen again. First time I burned was because I had the probes too far out. Second time was because I had the wrong probe plugged in.
I've "mostly" solved the water discolouration, it is still occurring but not as bad as it was. The third bend I did had zero burn and a little water marking.
The issue I'm trying to eliminate now is I've been getting a warp/buckling either side of the waste. I've just done a practice side with a bit less water and I made sure to let it bake at 260 for 15 minutes and I'll let it cool down a lot longer before I remove it. Actually I'll just leave it in overnight as I'm not going back out there again tonight!
Hopefully that solves the warping. If not then I'm out of ideas
Re: Build thread - Blackwood & Bunya Dreadnought
I used distilled water from Supercheap.
After bending the sides I immediately put them into moulds and left them there until needed
Alan
After bending the sides I immediately put them into moulds and left them there until needed
Alan
Re: Build thread - Blackwood & Bunya Dreadnought
I am using an LMI blanket and the same controller as you. I just bent some uke sides at around 80 thou thick, with a tighter radius then you, and started winding down the waste at 120F and finished when it was at 210F, no problem. i read the same recommendations as you, and it just burnt the wood. I have practiced on lots of different woods with the same results, the only one I can't get to bend, no matter what is qld maple.demonx wrote:All the instructions I've read and videos have said 320F and bake at 260f !!! Are we using the same bender & controller?
Col
Re: Build thread - Blackwood & Bunya Dreadnought
I'll have a mess around with that on Monday and see what the hundred less degrees does with some blackwood
Re: Build thread - Blackwood & Bunya Dreadnought
I pulled the last side out of the bender this morning and it was more warped (only behind the waste) than all the others, so that rules out the bake & cool time.
Next one which I'll do tomorrow I'll try the lower temps as suggested above.
Next one which I'll do tomorrow I'll try the lower temps as suggested above.
- rocket
- Blackwood
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Re: Build thread - Blackwood & Bunya Dreadnought
i don't know if i have more ass than class but i use a home made bender, a LMI blanket no controller, turn it on for a minute or so, turn off for a while and back on , just go by feeling how hot it is, don't rush to bend the stuff, let the heat penetrate the timber . and bend gradually, this is the most sophisticated method i've used so far, before this i've used, hot pipe, heat gun,halogen globes to heat bender, i find the silicone blanket the best heating method so far, bent blackwood,purple heart,Qld maple, curly maple, no problem, i just spray a little tap water on the sides wrap in brown paper then alfoil then whack it in the elcheapo home made bender.colburge wrote:I am using an LMI blanket and the same controller as you. I just bent some uke sides at around 80 thou thick, with a tighter radius then you, and started winding down the waste at 120F and finished when it was at 210F, no problem. i read the same recommendations as you, and it just burnt the wood. I have practiced on lots of different woods with the same results, the only one I can't get to bend, no matter what is qld maple.demonx wrote:All the instructions I've read and videos have said 320F and bake at 260f !!! Are we using the same bender & controller?
Col
Must be more ass than class i think!! Cheers,,
Rod.
Like I said before the crash, " Hit the bloody thing, it won't hit ya back
www.octiganguitars.com
www.octiganguitars.com
Re: Build thread - Blackwood & Bunya Dreadnought
Nice arse on that guitar Rod
I'm using a blanket without controller. I get up to close to 300deg for blackwood but I'm using a slat/wood/slat/sprign steel slat sandwich. The metal is probably absorbing a fair bit of the heat. I wrap wood in brown paper and then aluminium foil after spritzing it with a little bit of distilled water.
I didnt realise that the waist caul assembly on that LMI machine is fixed to the assembly on one side only.....surely this must result in uneven pressure across the waist when its clamped down?
I'm using a blanket without controller. I get up to close to 300deg for blackwood but I'm using a slat/wood/slat/sprign steel slat sandwich. The metal is probably absorbing a fair bit of the heat. I wrap wood in brown paper and then aluminium foil after spritzing it with a little bit of distilled water.
I didnt realise that the waist caul assembly on that LMI machine is fixed to the assembly on one side only.....surely this must result in uneven pressure across the waist when its clamped down?
Martin
Re: Build thread - Blackwood & Bunya Dreadnought
It's quite rigid and allows you to pull the sandwich straight out the side.kiwigeo wrote: I didnt realise that the waist caul assembly on that LMI machine is fixed to the assembly on one side only.....surely this must result in uneven pressure across the waist when its clamped down?
The attached image is the latest (the one I did last night) - you can see where the water marks are in ripples (inside the low spots) where it has buckled behind the waist.
This is my current obstacle as it's happening to every side and I don't know why.
Re: Build thread - Blackwood & Bunya Dreadnought
I missed this post until nowkiwigeo wrote: A wash with oxalic acid will often get rid of the worst of the staining.
Where abouts do you buy the oxalic acid? I've never heard of it.
Re: Build thread - Blackwood & Bunya Dreadnought
Bunnings or Mitre 10 should have it. I actually used an Intergrain product that I had sitting around my garage...used for preparing wood surface prior to treatment with their other products.demonx wrote:I missed this post until nowkiwigeo wrote: A wash with oxalic acid will often get rid of the worst of the staining.
Where abouts do you buy the oxalic acid? I've never heard of it.
Martin
Re: Build thread - Blackwood & Bunya Dreadnought
http://www.bunnings.com.au/cleaner-bric ... r_p0960276demonx wrote:I missed this post until nowkiwigeo wrote: A wash with oxalic acid will often get rid of the worst of the staining.
Where abouts do you buy the oxalic acid? I've never heard of it.
Martin
Re: Build thread - Blackwood & Bunya Dreadnought
If you have a Masters, they sell it too, in a smaller size. If you don't have one of those, look at your local for any deck cleaning product and check the ingredients for oxalic.kiwigeo wrote:http://www.bunnings.com.au/cleaner-bric ... r_p0960276demonx wrote:I missed this post until nowkiwigeo wrote: A wash with oxalic acid will often get rid of the worst of the staining.
Where abouts do you buy the oxalic acid? I've never heard of it.
Col
Re: Build thread - Blackwood & Bunya Dreadnought
Thanks guys. I'll have to look into that next week.
I've just bent another blackwood side, this time at around 210F. If I don't go back to the workshop tonight I'll post a pic or results tomorrow.
It seemed to bend "nearly" as easily. I also used a touch less water. Fingers crossed it removes the ripples.
I've just bent another blackwood side, this time at around 210F. If I don't go back to the workshop tonight I'll post a pic or results tomorrow.
It seemed to bend "nearly" as easily. I also used a touch less water. Fingers crossed it removes the ripples.
Re: Build thread - Blackwood & Bunya Dreadnought
Test piece at 210F.
Still getting the ripples as you can see by the attached pic with the straight edge on it.
For now I'm out of ideas.
Still getting the ripples as you can see by the attached pic with the straight edge on it.
For now I'm out of ideas.
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- Trevor Gore
- Blackwood
- Posts: 1605
- Joined: Mon Jun 20, 2011 8:11 pm
Re: Build thread - Blackwood & Bunya Dreadnought
Quarter sawn bends a lot flatter. What you have looks pretty "slabby".demonx wrote:Still getting the ripples as you can see by the attached pic with the straight edge on it.
For now I'm out of ideas...
Fine classical and steel string guitars
Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.
Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.
Re: Build thread - Blackwood & Bunya Dreadnought
For practice pieces I've been cutting pieces off inch board, so no, it's not quarter sawn.Trevor Gore wrote:demonx wrote: Quarter sawn bends a lot flatter. What you have looks pretty "slabby".
Surely flat sawn should bend flat though and there's more than flat vs quarter to this rippling problem
Re: Build thread - Blackwood & Bunya Dreadnought
Could this be something to do with the way the bender is made combined with uneven clamping pressure across the wood being bent? There are 3 vertical components (2 sides and a middle bit). Do the ripples coincide with these?
Ripples could occur if the sides were constrained in their ability to move/swell/expand laterally but were relatively free to move vertically.
Miguel
Ripples could occur if the sides were constrained in their ability to move/swell/expand laterally but were relatively free to move vertically.
Miguel
Re: Build thread - Blackwood & Bunya Dreadnought
On all the pieces the ripples have been behind the waist, not in the area where the wasit screws down. Where the waist screws down has been flat every time.
On the last piece where I tried the lower temp it also had ripples on the widest part of the body, which is the only time it's happened there.
The rest of the areas have been pretty smooth. I wish LMI had a trouble shooting chart for the bender so you could look up your problem and solve it.
On the last piece where I tried the lower temp it also had ripples on the widest part of the body, which is the only time it's happened there.
The rest of the areas have been pretty smooth. I wish LMI had a trouble shooting chart for the bender so you could look up your problem and solve it.
Re: Build thread - Blackwood & Bunya Dreadnought
As Trevor said, flatsawn will do this, especially if you use lots of water
Re: Build thread - Blackwood & Bunya Dreadnought
I've cut the water back to being next to none.jeffhigh wrote:As Trevor said, flatsawn will do this, especially if you use lots of water
Guess I'll have to hunt down some cheap quarter sawn timber to experiment.
Re: Build thread - Blackwood & Bunya Dreadnought
For cleaning "water stains" off blackwood after bending, I used Cabot's Deck Clean. It contains oxalic acid and is available is a smaller 1l container for around $12.65 at Bunnings. It worked pretty well on my blackwood sides.
I did my first trial bends on some timber (silky oak I think) that was flat sawn and it cupped a lot accross the grain. After trying again on some quarter sawn timber of the same species, it came out flat.
I did my first trial bends on some timber (silky oak I think) that was flat sawn and it cupped a lot accross the grain. After trying again on some quarter sawn timber of the same species, it came out flat.
Richard
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