Can you use hardwood for bracing?

[Quinny]

Hi,

I have been buying my brace wood from ALS and therefore have used their available wood - basswood and Bunya pine. Now I am making a concert uke in a Koa body and Aussie Blackwood neck. I thought it might be preferred to use bracing that is similar to the soundboard and heard blackwood is the closest in properties to Koa.

Is it a preference to use a hardwood for bracing? I thought being a similar wood then the vibration might resonate better. On the other hand, will it be too heavy and dampen the vibration and I should stick to a lighter wood like the basswood or Bunya pine?

Any advice is really appreciated.

Thanks

Andrew

[RobDyball]

Well, for science you should really make two instruments with the alternative brace timbers and compare the results...

On the other hand, will it be too heavy and dampen the vibration and I should stick to a lighter wood like the basswood or Bunya pine?

Yes.

I think the theory is that the braces are there to a) stop the very thin soundboard from folding over under the significant string tension, and b) dump the energy of the vibrating string onto the soundboard. The two at at odds with each other: the better reinforced the soundboard, the less efficient the energy dump. Spruce & similar always seems to win in that contest.

But you should definitely make a blackwood braced instrument for science!

[kiwigeo]

I think the theory is that the braces are there to a) stop the very thin soundboard from folding over under the significant string tension, and b) dump the energy of the vibrating string onto the soundboard. The two at at odds with each other: the better reinforced the soundboard, the less efficient the energy dump. Spruce & similar always seems to win in that contest.

But you should definitely make a blackwood braced instrument for science!

My take on bracing...it's there for only one reason....to enable the soundboard to be thin enough to vibrate but not collapse. The pattern and physical properties of the bracing will affect the way the top vibrates but purely due to the fact that in the vicinity of a brace the top is less free to vibrate than areas free of bracing.

When I brace an instrument the mission statement is as follows:
1. Use the minimum amount of bracing necessary to prevent the top collapsing. Robustness of bracing should be be governed by top wood type and thickness.
2. Light and stiff bracing material. Laminated bracing incorporating carbon fibre is the go here.
3. Bracing should divide the active area of the soundboard up into roughly equal areas to promote even vibration of the top. Falcate bracing achieves this.

Re dumping of the string energy into the soundboard via the bracing.....I don't agree. Most of the string energy travels to the soundboard directly via the bridge saddle.

[Quinny]

Thanks for the replies martin and Rob. It appears the principle of compromise applies between stiffening the soundboard versus not making it overly rigid. I can see how 'light and stiff bracing fits the bill, even carbon fibre??

What do you think about using the Blackwood for bracing that I am using for the neck. The plans I have recommend the horizontal upper bout and waist braces at 4.7mm wide and the 3 fan braces at 3.2mm.
Any opinions if Blackwood is too heavy or will be ok?

Andrew

[Allen]

Personally I wouldn't be using Blackwood, though I suppose it's weight is similar to Mahogany which is used quite often in ukuleles.

[curly]

My favourite Brace wood is Silver Quandong . Eleocarpus grandis . Though it is botanically a hardwood (angiosperm ) good old growth stuff weighs in under 400kg a cube so its well in the target density , tap tone is lovely and the moe is good too . It is completely awesome to carve as it doesn't have the varying density early/late wood of a conifer . Old trees are bloody hard to come by though , and the young stuff , perhaps counterintuitively , is a fair bit heavier . Silver Wattle Acacia dealbata would be another good hardwood choice . As with all good brace stock , I'd go riven (split ), not sawn .
Pete

[RobDyball]

Interesting, Pete!
Apparently it's also sought after for arrow shafts.

Anyone got a source on some?

R

[jeffreyyong]

I've been using hardwood for my bracings for more than a decade now and its still holding on strong

[simso]

But thats on your back.

The sides and back are merely a solid chamber, so IMO they could be made from anything and guitars like ovations re-inforce that point.

What about your top, are you running hardwood braces on the top.

Steve