| Official Luthiers Forum! http://www.luthiersforum.com/forum/ |
|
| Thoughts on hardwood braces for back http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=24306 |
Page 1 of 1 |
| Author: | Corky Long [ Sat Oct 24, 2009 7:40 am ] |
| Post subject: | Thoughts on hardwood braces for back |
I'm building a "practice" steel string guitar for my kids - and have some very hard dogwood that I"ve been drying for awhile. When planing to cut up some braces for the back I wondered about the effect of using some of the dogwood for the back braces (wouldn't use it for the top, which will be red cedar, btw. I'll use spruce braces for the top) The back and sides of this guitar will be a soft maple. Thanks! |
|
| Author: | Tom West [ Sat Oct 24, 2009 7:56 am ] |
| Post subject: | Re: Thoughts on hardwood braces for back |
Corky: Normally the tap tone of the back is higher than the tap tone of the top.Don't think there is enough weight differential to cause a shift in tap tone and if there is it may be countered by extra stiffness. That being said,lighter guitars tend to sound better IMO. The way to make light guitars is to pay very close attention to the weight of all components during construction. Have fun with the project. Tom |
|
| Author: | Mark Groza [ Sat Oct 24, 2009 9:53 am ] |
| Post subject: | Re: Thoughts on hardwood braces for back |
Corky,Hardwood can be used for backs with no problem, but Dogwood is one of the most dense and heavy hardwoods.It is very strong though.I wood look for something lighter, mabey maple if you have that. |
|
| Author: | Haans [ Sat Oct 24, 2009 11:28 am ] |
| Post subject: | Re: Thoughts on hardwood braces for back |
Don't know about dogwood, but I have been using laminated spruce/BRW, Coco, or African Blackwood/spruce both top and back and it works very well. |
|
| Author: | LPMc [ Sat Oct 24, 2009 11:42 am ] |
| Post subject: | Re: Thoughts on hardwood braces for back |
There are two schools of thought about guitar backs: either they work with the top to increase sound, or they act as reflectors. Lightly built, responsive backs, tuned some number of semitones up from the top can act as the former. Rigid, non-flexible backs act as the latter. If you want the former, dogwood bracing isn't going to help. If the latter, it probably doesn't matter. Another consideration, playing the guitar snugged up next to the body tends to dampen-out the contribution of a responsive back. Classic guitar position - holding the guitar away from the body - allows the back to move. About the top bracing, any reason for using cedar rather than spruce? |
|
| Author: | truckjohn [ Sat Oct 24, 2009 10:27 pm ] |
| Post subject: | Re: Thoughts on hardwood braces for back |
Other than shaving/adjusting... Hardwood bracing can work just fine. It is generally plenty strong, so no worries there... What happens if you decide you want to fool with the tuning of the back and want to shave those Dogwood braces? Last time I fooled with Dogwood... It didn't shave particularly easy. Now consider that you can get 15 lifetime supplies of Spruce free in construction dumpsters.... Go grab an armful of Construction dumpster 2x scrap and use it for back brace wood... Just make sure you pick pieces that have at least 18" between knots for back braces... Good luck John |
|
| Author: | Matt Bouchie [ Sun Oct 25, 2009 4:04 am ] |
| Post subject: | Re: Thoughts on hardwood braces for back |
Filippo Morelli wrote: What "tuning" is going to be done to the back of a guitar? Filippo Alan Carruth had me tune the back of the guitar I made in his class with Chladni patterns. The guitar sounds awesome so I'm assuming it helped. I know he'll have me tune the back on the one I'm making now, as well. I'll let him explain just what we were looking for. I'm hoping to understand it a bit more on the second one. I remember it not being as straightforward as tuning the top, if you can call that straightforward! Matt |
|
| Author: | bluescreek [ Sun Oct 25, 2009 7:48 am ] |
| Post subject: | Re: Thoughts on hardwood braces for back |
Bracing is to be light and strong . Heavier bracing and most hardwood is heavier than the spruces and it is the weight to strength ratio you look at. Mahogany has been used for bracing but for my money , I still will go with spruce as it is stronger and ligher. Mass is the enemy. I agree on the back ,the bracing is less of a factor there than on the top. Build and learn . You never know. |
|
| Author: | truckjohn [ Sun Oct 25, 2009 12:34 pm ] |
| Post subject: | Re: Thoughts on hardwood braces for back |
Many folks don't fool with tuning the backs at all.... but some people like Me can't help but leave well enough alone. If Corky is anything like many of us in this respect, he will read some of Al's posts on back tunings and want to give it a crack.... and then have to fight against shaving a wood that was commonly used for Golf club heads and Mallets and as a substitute for Ebony.... This is the only reason I wouldn't do it... Otherwise, have at it with the full knowledge that it will still Sound like a Guitar... Thanks John |
|
| Author: | Alan Carruth [ Sun Oct 25, 2009 4:18 pm ] |
| Post subject: | Re: Thoughts on hardwood braces for back |
I actually fall between the 'active back' and 'reflector back' schools of thought: I think that the back should be 'active' in the low frequenency range, and a good 'reflector' above that. When I've looked at guitar spectra, I've found that the only back resonant mode that seems to add to theout put is the low 'main back' tap tone. Most of the rest seem more or less to 'steal' energy from the top, which is, after all, much lighter, and therefore more capable of turning string forces into sound. The reason the 'main back' mode can help is that it's the 'monopole' mode; a large area is moving like a loudspeaker cone, and can thus help to pump air through the soundhole at low frequencies. Tuning the back so that the 'main back' resonant mode is reasonably close in pitch to the 'main top' mode helps it pump more air. So, in the low range you want the back to be able to respond to pressure changes in the box and help out. Above that, any motion of the back is most likely just taking energy from the top and wasting it, so you want to minimize that. This seems like a paradox, and it is, to some extent: we want the back to move sometimes and not others. One possible resolution to this is to see that the back can act like a 'flywhel' in the low range, storing energy to feed back into the air. Making the back reasonably heavy makes it a better flywheel, since it can store more energy at a given amplitude of vibration. The weight also helps it resist the urge to dance when those high frequency signals come around. If it's got low damping, that's even better: in might dance more at it's tresonantpitches, but those are pretty narrowly defined, so the loss is resstricted to only certain frequencies. So, let's see, that suggests a dense, stiff wood with low damping might make a good back; something like, say, Brazilian rosewood? Now, obviously, this doesn't explain why mahogany can also make a good back. A 'hog' back can be as little as 20%-30% heavier than the top; not a lot. So you can see that 'Al's Grand Unified Theory of the Guitar' need som more work. |
|
| Author: | Corky Long [ Mon Oct 26, 2009 9:41 am ] |
| Post subject: | Re: Thoughts on hardwood braces for back |
All - Thanks for the thorough and considered responses. I'm going to give it a go and see what happens. Although it's true that shaving these braces is going to be a challenge. This stuff is very hard indeed. I'll let you all know how I make out. Regards, |
|
| Page 1 of 1 | All times are UTC - 5 hours |
| Powered by phpBB® Forum Software © phpBB Group http://www.phpbb.com/ |
|