The Acoustic Guitar Forum

Go Back   The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > Build and Repair

Reply
 
Thread Tools
  #181  
Old 05-31-2015, 04:12 PM
Viking Viking is offline
Registered User
 
Join Date: Mar 2013
Location: Colorado Springs, CO
Posts: 234
Default

Quote:
Originally Posted by dekutree64 View Post
I thicknessed by "oops, I think I overdid it" Flexing by hand to feel the stiffness, but not checking often enough.
lol.

Quote:
Originally Posted by dekutree64 View Post
I'm breaking all the rules on this one. OM-ish steel string, with .070" Indian rosewood top. I tried bolt-on necks on my first couple guitars, but Spanish heel style is so much more elegant, easy, and lightweight, I've decided to take my chances on future neck reset problems. I'm usually too lazy to do back binding anyway, which conveniently makes heel slip resets easier.

Here's the build thread for it http://www.luthiersforum.com/forum/v...=10130&t=37136 which is very old since I only did the rosette at first, and then decided to build some other stuff to gain more experience before bracing it. And I haven't gotten around to updating the thread again since resuming work on it last winter... but that bracing photo I posted is the current state. I can't do any more on it for a while due to high humidity.

I have build threads for the harp guitar and some others on that same forum. Just scroll through the list for threads started by DennisK, most of them are near the top.
I wondered what the top wood was. Too dark to be redwood. I'll have to sign up for that forum, can't see any of your images.
__________________
-- Nick
Reply With Quote
  #182  
Old 05-31-2015, 08:15 PM
charles Tauber charles Tauber is offline
Registered User
 
Join Date: Feb 2011
Posts: 6,604
Default

Quote:
Originally Posted by Viking View Post
I had to look up the math to calculate the displacement of the arc given a fixed segment of a specific radius. It's been a while since I took geometry. Here's the equation for anyone following along.

Radius = (height / 2) + (width^2/(8 * height))
"Back in the day", people didn't seem so picky about what radius was being used.

I was taught to use a radius that has a 3/16" drop in a 16" span. I still use that for back braces. Over the years, I've probably calculated what radius that is, but I've forgotten. Since I don't use radiused dishes, the actual radius isn't terribly relevant to me. It's pretty easy to work with.

I'm not saying it's better, just that it is a different approach.
Reply With Quote
  #183  
Old 05-31-2015, 08:56 PM
Viking Viking is offline
Registered User
 
Join Date: Mar 2013
Location: Colorado Springs, CO
Posts: 234
Default

Quote:
Originally Posted by charles Tauber View Post
"Back in the day", people didn't seem so picky about what radius was being used.

I was taught to use a radius that has a 3/16" drop in a 16" span. I still use that for back braces. Over the years, I've probably calculated what radius that is, but I've forgotten. Since I don't use radiused dishes, the actual radius isn't terribly relevant to me. It's pretty easy to work with.

I'm not saying it's better, just that it is a different approach.
That's a 14.16 foot radius.

Here is a handy calculator that will crunch the numbers if anyone wants it.

http://www.mathopenref.com/arcradius.html

And yeah, precision in some regards isn't required to make a good sounding instrument. My brain wants to know and be intentional with things that I can be intentional with though.
__________________
-- Nick
Reply With Quote
  #184  
Old 05-31-2015, 09:42 PM
TEK TEK is offline
Registered User
 
Join Date: Aug 2012
Location: Missouri
Posts: 610
Default

Quote:
Originally Posted by Viking View Post
That's a 14.16 foot radius.

Here is a handy calculator that will crunch the numbers if anyone wants it.

http://www.mathopenref.com/arcradius.html

And yeah, precision in some regards isn't required to make a good sounding instrument. My brain wants to know and be intentional with things that I can be intentional with though.
All the math makes me dizzy so I used a 15 foot long piece of string tied to a wall and stretched it out and marked my board by tying a pencil to the other end and marking my arch. Yes I live in Missouri
Reply With Quote
  #185  
Old 06-01-2015, 11:57 AM
Viking Viking is offline
Registered User
 
Join Date: Mar 2013
Location: Colorado Springs, CO
Posts: 234
Default

Quote:
Originally Posted by TEK View Post
All the math makes me dizzy so I used a 15 foot long piece of string tied to a wall and stretched it out and marked my board by tying a pencil to the other end and marking my arch. Yes I live in Missouri
Nothing wrong with that! lol
__________________
-- Nick
Reply With Quote
  #186  
Old 06-20-2015, 07:32 PM
Viking Viking is offline
Registered User
 
Join Date: Mar 2013
Location: Colorado Springs, CO
Posts: 234
Default

It's been a very satisfying couple of weeks since my last post. I built the brace radiusing jig that Charles suggested, with a couple modifications. It worked well. Then I completed the back of the guitar. Ready to move on to thicknessing the sides and building a side bending jig.

Here is the completed brace radiusing jig. The end caps are made of a cross piece with a shelf for the braces to rest on. They are adjustable to accommodate braces of different initial height. Another interesting feature is that the radiused guides that the plane rides on are removable, so I can cut different guides with a different radius and re-use the jig.


Loaded with braces and the plane in place.


Radiused braces.


Cutting the back x brace lap joint.


Gluing braces in place.






Braces glued. And the center reinforcing strip dry fit into place.


Shaping the braces.


Shavings everywhere. Love the smell of spruce being cut.




Gluing the x brace patch.


Shaping the patch. I used a small piece of walnut for a nice contrast.


The finished back. Center reinforcing strip glued in place, and all has been sanded.




For the side bending machine, I'm going to be building one of these....

http://www.lint.org/index.php/articl...ending-machine
__________________
-- Nick

Last edited by Viking; 06-20-2015 at 07:48 PM.
Reply With Quote
  #187  
Old 07-05-2015, 05:46 PM
Viking Viking is offline
Registered User
 
Join Date: Mar 2013
Location: Colorado Springs, CO
Posts: 234
Default

Finished the side bending machine. Light bulb style. 2 150 watt bulbs and 1 200 watt bulb.

Form building with my newly constructed router table. I built that too since I last posted here. It was handy for several tasks I've had to do over the last couple weeks.


The form with the aluminum bars in place.


The completed bending machine.


The first side cooling in the machine. Crazy how hot that thing got from just a couple light bulbs. It was hot to the touch through a pair of leather gloves. I had thicknessed the sides to just under .1 inches.


Took a bit longer than I expected, but no matter. Feels like a colossal hurdle has been passed, having successfully bent a piece of wood. Now I just have to thickness and bend the other one. After that, on to building the mold that will be the side's home during block and kerfed lining installation.

I'd like to hear some commentary on the way I went about bending the wood. I would spritz a little water on, then wait a couple minutes for it to heat up and begin to evaporate, the steam being what I believe is heating and allowing the wood fibers to relax. Then I would crank down the nuts on the eye bolts a couple turns. Once the wood was dry, I would crank another time or two, and then slightly re-wet. Should I wet the wood multiple times? Or just once at the beginning? This was successful, but I wonder if I used too much water. I suppose it doesn't much matter as long as it worked.

Sigh. Dreams are 1 small step closer.
__________________
-- Nick
Reply With Quote
  #188  
Old 07-05-2015, 09:01 PM
printer2 printer2 is offline
Registered User
 
Join Date: Dec 2012
Posts: 3,787
Default

Well since sides are usually in the vicinity of 0.085" I think you figured out a system that works if you can bend 0.100".
Reply With Quote
  #189  
Old 07-05-2015, 09:05 PM
Sam VanLaningham Sam VanLaningham is offline
Registered User
 
Join Date: Nov 2012
Location: Bend, Oregon
Posts: 1,236
Default

Looking solid Viking! Nice work.

Sam
Reply With Quote
  #190  
Old 07-05-2015, 09:16 PM
charles Tauber charles Tauber is offline
Registered User
 
Join Date: Feb 2011
Posts: 6,604
Default

Quote:
Originally Posted by Viking View Post
I'd like to hear some commentary on the way I went about bending the wood. I would spritz a little water on, then wait a couple minutes for it to heat up and begin to evaporate, the steam being what I believe is heating and allowing the wood fibers to relax. Then I would crank down the nuts on the eye bolts a couple turns. Once the wood was dry, I would crank another time or two, and then slightly re-wet. Should I wet the wood multiple times? Or just once at the beginning? This was successful, but I wonder if I used too much water. I suppose it doesn't much matter as long as it worked.
Over the last three decades, it's been fascinating to see the number of variations that have emerged from the one basic design of light-bulb-heated side bender designed by Charles Fox. Most of them work, some better than others.

As you may be aware, most benders of this general design sandwich the wood between two metal slats - usually spring steel - rather than have bare wood against the bender. The primary reasons for the slats is to retain heat, support the wood while bending - reducing side cracking in difficult woods - and keep moisture in during the being process. With the wood sandwiched, it is generally inaccessible during the bending so that one can't add water while bending. Instead, the sides are spritzed with water prior to bending, then bent.

Most of the benders of this general design also have spring loaded "batons" that are used to actually bend the sides as they are drawn from the waist to the ends of the side, usually in a single, smooth motion. Think rolling pin type motion. With the pre-heated bender, the actual side bending only takes a minute or two. It's then left to "cook" for 15 minutes or so, before turning the bender off to cool. (Or the sides can be removed while still hot and then placed in a form to maintain their shape while they cool.)

The half forms between which the 1/2" rods run have the bends in the waist and ends exaggerated a little to decrease spring back. Ideally, the holes in the half forms are drilled so that the circumference of the rods are tangent with the curve of the half form. That prevents kinks in the sides and ensures that the bend follows the desired curvature of the half forms.

As you said, none of this much matters if you are satisfied with the result you obtained.
Reply With Quote
  #191  
Old 07-05-2015, 09:35 PM
Viking Viking is offline
Registered User
 
Join Date: Mar 2013
Location: Colorado Springs, CO
Posts: 234
Default

Quote:
Originally Posted by printer2 View Post
Well since sides are usually in the vicinity of 0.085" I think you figured out a system that works if you can bend 0.100".
I wondered if mine were just a tad thick. But they seemed much more bendy to my untrained hands than they did at .2 inches thick, so I went with them at just under .1 inches. The thinest was about .95.

Quote:
Originally Posted by Left of Sam View Post
Looking solid Viking! Nice work.

Sam
Thanks Sam.

Quote:
Originally Posted by charles Tauber View Post
Over the last three decades, it's been fascinating to see the number of variations that have emerged from the one basic design of light-bulb-heated side bender designed by Charles Fox. Most of them work, some better than others.

As you may be aware, most benders of this general design sandwich the wood between two metal slats - usually spring steel - rather than have bare wood against the bender. The primary reasons for the slats is to retain heat, support the wood while bending - reducing side cracking in difficult woods - and keep moisture in during the being process. With the wood sandwiched, it is generally inaccessible during the bending so that one can't add water while bending. Instead, the sides are spritzed with water prior to bending, then bent.

Most of the benders of this general design also have spring loaded "batons" that are used to actually bend the sides as they are drawn from the waist to the ends of the side, usually in a single, smooth motion. Think rolling pin type motion. With the pre-heated bender, the actual side bending only takes a minute or two. It's then left to "cook" for 15 minutes or so, before turning the bender off to cool. (Or the sides can be removed while still hot and then placed in a form to maintain their shape while they cool.)

The half forms between which the 1/2" rods run have the bends in the waist and ends exaggerated a little to decrease spring back. Ideally, the holes in the half forms are drilled so that the circumference of the rods are tangent with the curve of the half form. That prevents kinks in the sides and ensures that the bend follows the desired curvature of the half forms.

As you said, none of this much matters if you are satisfied with the result you obtained.
I wondered what the metal slats were for. I actually had bought some metal flashing of the appropriate dimensions, but I couldn't quite see a point to it as I was building the machine and thinking through the process, so I left it out. What you said makes sense though, that it keeps the moisture closer to the wood. I'll see how bending the second side goes without it.

I did take the lower bout caul off after the side cooled, and it sprang back pretty good. So I clamped it back up and turned the lights on again to cook it a bit more. Maybe I'll cook it again this evening and then leave it clamped up till morning. See if that convinces it to stay put.
__________________
-- Nick
Reply With Quote
  #192  
Old 07-05-2015, 10:26 PM
charles Tauber charles Tauber is offline
Registered User
 
Join Date: Feb 2011
Posts: 6,604
Default

Quote:
Originally Posted by Viking View Post
Maybe I'll cook it again this evening and then leave it clamped up till morning. See if that convinces it to stay put.
It won't. It'll considerably reduce the spring back, but won't entirely eliminate it. You then have the choice of bending it by hand over a hot pipe, or similar, to the exact shape or just using a bit of force to bring the ends into the required shape during assembly. The basic shape of the waist, however, needs to be pretty close.
Reply With Quote
  #193  
Old 07-05-2015, 10:48 PM
Viking Viking is offline
Registered User
 
Join Date: Mar 2013
Location: Colorado Springs, CO
Posts: 234
Default

Quote:
Originally Posted by charles Tauber View Post
It won't. It'll considerably reduce the spring back, but won't entirely eliminate it. You then have the choice of bending it by hand over a hot pipe, or similar, to the exact shape or just using a bit of force to bring the ends into the required shape during assembly. The basic shape of the waist, however, needs to be pretty close.
That's where the outside mold becomes useful, right?
__________________
-- Nick
Reply With Quote
  #194  
Old 07-05-2015, 11:58 PM
charles Tauber charles Tauber is offline
Registered User
 
Join Date: Feb 2011
Posts: 6,604
Default

Quote:
Originally Posted by Viking View Post
That's where the outside mold becomes useful, right?
An outside mold is one method.
Reply With Quote
  #195  
Old 07-06-2015, 06:32 PM
stuw stuw is offline
Registered User
 
Join Date: Feb 2013
Posts: 228
Default

Looking really good Nick,

I spritz my sides with home made super soft...

1/2 water

1/2 fabric softner

Especially on figured wood...still not sure if it works better than just water..but I haven't cracked a side since using it...but then I haven't bent that many sides since I started using it....

Oh..and I don't get any static cling on my sides either.....

Stu
__________________
I'm not a luthier...luthier's know what they are doing.
Reply With Quote
Reply

  The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > Build and Repair

Thread Tools



All times are GMT -6. The time now is 01:09 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2000 - 2018, The Acoustic Guitar Forum
vB Ad Management by =RedTyger=