The Acoustic Guitar Forum

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

Reply
 
Thread Tools
  #31  
Old 12-21-2017, 10:46 PM
Kieran Kieran is offline
Registered User
 
Join Date: Sep 2017
Posts: 46
Default

Apologies on the duplication but I posted this in the wrong thread.

I little progress to report, I have eventually decided on a flying brace over the bridge plate. Because the guitar body is so small and I have thinned the cedar top under 2mm I feel this brace pattern will be more suitable than more traditional patterns.



I have decided to scrap the plywood sides and laminated back I was going to use and I have bought a walnut back and side set.





Although the build is coming along slowly I am pleased with progress and thought what the hell, might as well put a solid wood back and sides on the little beast.

My question is this: the figuring/grain is not exactly the most stunning on this set, what are the likely advantages of either using the heart wood or the sap wood down the centre of the back? What would be the structural and or tonal differences between using the tightly spaced sap wood grain over the wider heart wood?





I also splashed out on a new ovangkol finger board



Thanks for following
Reply With Quote
  #32  
Old 12-22-2017, 07:06 AM
printer2 printer2 is offline
Registered User
 
Join Date: Dec 2012
Posts: 3,325
Default

The sapwood side of the boards will have a better chance of not cracking with humidity changes. It is cut more on quarter.
__________________
Fred
Reply With Quote
  #33  
Old 12-22-2017, 07:18 AM
Truckjohn Truckjohn is offline
Registered User
 
Join Date: Feb 2016
Posts: 1,202
Default

The back set is well quartersawn on the sap and moves to flat sawn in the middle. Jointing the back at the sap wood will give you a more well behaved back with humidity swings.

On the top bracing.
1. Replace the finger braces with new ones that butt the X-brace tightly. This is especially critical on a thin top. If you don't - you will end up with funny humps and dips.

2. Instead of the flying brace from the X down the center of the bridge - if you are really worried - consider a brace running straight across the back of the bridge plate that joins the X tightly.

Most likely you won't need either the flying brace or the PMTE across the back of the bridge plate. I would start off with 1 conventional tone bar. This is a very small guitar. If you want it to have some bass - it has to be built pretty lightly.

Another opinion. I personally do not like to see scalloping on any braces between the bridge and the neck. You need a stiff upper bout structure so it doesn't do bad things across the soundhole. It's such a small guitar that it will probably be oK... Just keep an eye out for the neck angle shifting over time.

Last edited by Truckjohn; 12-22-2017 at 07:25 AM.
Reply With Quote
  #34  
Old 12-22-2017, 09:42 AM
Kieran Kieran is offline
Registered User
 
Join Date: Sep 2017
Posts: 46
Default

Quote:
Originally Posted by printer2 View Post
The sapwood side of the boards will have a better chance of not cracking with humidity changes. It is cut more on quarter.


Thanks printer, kind of what I was thinking and what Louie kindly suggested when I posted this on the wrong thread.
Reply With Quote
  #35  
Old 12-22-2017, 09:52 AM
Kieran Kieran is offline
Registered User
 
Join Date: Sep 2017
Posts: 46
Default

Quote:
Originally Posted by Truckjohn View Post
The back set is well quartersawn on the sap and moves to flat sawn in the middle. Jointing the back at the sap wood will give you a more well behaved back with humidity swings.

On the top bracing.
1. Replace the finger braces with new ones that butt the X-brace tightly. This is especially critical on a thin top. If you don't - you will end up with funny humps and dips.

2. Instead of the flying brace from the X down the center of the bridge - if you are really worried - consider a brace running straight across the back of the bridge plate that joins the X tightly.

Most likely you won't need either the flying brace or the PMTE across the back of the bridge plate. I would start off with 1 conventional tone bar. This is a very small guitar. If you want it to have some bass - it has to be built pretty lightly.

Another opinion. I personally do not like to see scalloping on any braces between the bridge and the neck. You need a stiff upper bout structure so it doesn't do bad things across the soundhole. It's such a small guitar that it will probably be oK... Just keep an eye out for the neck angle shifting over time.


Cheers for the detailed input John, always appreciated.
I spent ages considering the additional braces and struggled to make my mind up. The single tone bar just seems a bit odd on this tiny body, the distances between the x brace tails and the tail block just didn't seem to lend itself to this traditional bracing, I can't tell you why, it just doesn't feel right. I do however like the idea of the straight brace below the bridge, there are a few examples of parlour guitars over in the custom area using this. I haven't glued down those extra braces yet, so, I shall make some new ones and post a few pics.
Also, do you think I could put a tiny notch into the x brace tails to accept the new straight brace under the bridge plate or will this introduce unnecessary weakness?

Thanks again

Ps what's PMTE?
Reply With Quote
  #36  
Old 12-22-2017, 11:05 AM
Rodger Knox's Avatar
Rodger Knox Rodger Knox is offline
AGF Sponsor
 
Join Date: Jul 2013
Location: Baltimore, Md.
Posts: 1,996
Default

Quote:
Originally Posted by Kieran View Post
Ps what's PMTE?
That's a Proulx Magic Tone Enhancer. It's a small brace(about 0.10" wide and about 3/8"tall), frequently rosewood, along the back of the bridge plate and connecting to the X brace. Mario Proulx wasn't the first to use it, but he advocated it many years ago on the MIMF, and the name stuck.
__________________
Rodger Knox, PE
'56 Gibson J-50
et al

http://www.rodgerknoxguitars.com

Last edited by Rodger Knox; 12-23-2017 at 02:48 PM. Reason: corrected spelling
Reply With Quote
  #37  
Old 12-22-2017, 11:14 AM
Kieran Kieran is offline
Registered User
 
Join Date: Sep 2017
Posts: 46
Default

Quote:
Originally Posted by Rodger Knox View Post
That's a Prolux Magic Tone Enhancer. It's a small brace(about 0.10" wide and about 3/8"tall), frequently rosewood, along the back of the bridge plate and connecting to the X brace. Mario Prolux wasn't the first to use it, but he advocated it many years ago on the MIMF, and the name stuck.


Thanks Rodger,
From those discussions, would you consider it a good possibility for this type of small body build?
Reply With Quote
  #38  
Old 12-23-2017, 11:56 AM
Rodger Knox's Avatar
Rodger Knox Rodger Knox is offline
AGF Sponsor
 
Join Date: Jul 2013
Location: Baltimore, Md.
Posts: 1,996
Default

Mario is known for building bluegrass drednaughts, but I've used it in smaller guitars. I taper the back of my bridges, and the PMTE adds a bit of mass and stiffness just behind the bridge. My bridgeplate extends about 1/8" beyond the back of the bridge. It's all part of a system.

There's a lot of talk about top stiffness as if it's a single number, but it's the distribution of stiffness/mass throughout the top that dictates how it vibrates. It's a puzzle, you have to decide which pieces to use and how to fit them together.
__________________
Rodger Knox, PE
'56 Gibson J-50
et al

http://www.rodgerknoxguitars.com
Reply With Quote
  #39  
Old 12-23-2017, 02:41 PM
LouieAtienza LouieAtienza is offline
Registered User
 
Join Date: Feb 2013
Posts: 4,310
Default

I believe Mario is in a way northern part of Canada... But I'm pretty sure his last name is Proulx.
Reply With Quote
  #40  
Old 12-23-2017, 02:50 PM
Rodger Knox's Avatar
Rodger Knox Rodger Knox is offline
AGF Sponsor
 
Join Date: Jul 2013
Location: Baltimore, Md.
Posts: 1,996
Default

Quote:
Originally Posted by LouieAtienza View Post
I believe Mario is in a way northern part of Canada... But I'm pretty sure his last name is Proulx.
Thanks, Louie. I've corrected the spelling. Sorry about that.
__________________
Rodger Knox, PE
'56 Gibson J-50
et al

http://www.rodgerknoxguitars.com
Reply With Quote
  #41  
Old 12-23-2017, 03:35 PM
Kieran Kieran is offline
Registered User
 
Join Date: Sep 2017
Posts: 46
Default

Quote:
Originally Posted by Rodger Knox View Post
Mario is known for building bluegrass drednaughts, but I've used it in smaller guitars. I taper the back of my bridges, and the PMTE adds a bit of mass and stiffness just behind the bridge. My bridgeplate extends about 1/8" beyond the back of the bridge. It's all part of a system.



There's a lot of talk about top stiffness as if it's a single number, but it's the distribution of stiffness/mass throughout the top that dictates how it vibrates. It's a puzzle, you have to decide which pieces to use and how to fit them together.


Thanks Rodger,
I am going to have another think about the bridge plate and lower bout bracing over the coming days. I really appreciate the feedback.
Reply With Quote
  #42  
Old 01-07-2018, 10:40 AM
Kieran Kieran is offline
Registered User
 
Join Date: Sep 2017
Posts: 46
Default Small body first build

Happy new year folks.

The soundboard bracing is finished. I decided to keep it light and focus on the main top resonate mode, hopefully creating some nice bass from this really small box. The tap tones are really pleasing so far, it sounds bright but with a really pretty balanced sound.



I have thicknessed the new walnut back and decided on an x brace. The walnut is looking good, lovely silking and a lush deep woody ring, it should compliment the cedar top beautifully.



Also, I would appreciate any advice regarding the idea of making a new neck from this flat sawn walnut that I have. I was thinking of cutting out two profiles of the neck, headstock and heel from this board then laminating them together with a mahogany centre strip. The board is 35mm 1 3/8 thick. Or would I be better off using it to do a more traditional scarf joint arrangement?

Cheers
Reply With Quote
  #43  
Old 01-07-2018, 11:11 AM
LouieAtienza LouieAtienza is offline
Registered User
 
Join Date: Feb 2013
Posts: 4,310
Default

Looks good, Kieran. Absolutely nothing wrong building a neck that way. I try to arrange it so that the growth rings at the ends point away from each other.
Reply With Quote
  #44  
Old 01-07-2018, 11:36 AM
Kieran Kieran is offline
Registered User
 
Join Date: Sep 2017
Posts: 46
Default

Quote:
Originally Posted by LouieAtienza View Post
Looks good, Kieran. Absolutely nothing wrong building a neck that way. I try to arrange it so that the growth rings at the ends point away from each other.


Thanks Louie, so with the heart wood in the centre at the mahogany centre strip? If I understand that correctly it would makes sense.

Appreciate the input.
Reply With Quote
  #45  
Old 01-07-2018, 02:21 PM
Kieran Kieran is offline
Registered User
 
Join Date: Sep 2017
Posts: 46
Default

Also, what are people's thoughts on adding cross grain braces to form an asterisk? Overkill or prudent?

Thanks

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 12:10 PM.


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