How much twist in the grain is too much ?

[Samuli Samuelsson]

Hi.

I asked about splitting a log for soundboards on the old side of MIMF, and got some great help.

Well, since the temperatures rose enough for my tractor, I finally managed to get the pieces down to the yard and split one of the short ones according to the instructions.

As I kind of suspected, there's quite a bit of twist, that's very common thing on pines and spruces that grow in Finland.
The twist is about 30 degrees on a ~60cm piece.

That obviously means that there's no point in splitting them from the instrument making viewpoint, but is there any point in sawing 'em for such use either?

Does the intended use as archtop instrument soundboards help or hurt the decision any?
How about a double bass, the twist is somewhere near 90 degrees then?

[Alan Carruth]

I'd say that was too much twist for soundboards, but you might well get some good bracing stock.

Often the twist will change as the tree grows. Sometimes it starts out more or less straight, and the twist bewcomes greater as the diameter increases. It's actually the same number of degrees per vertical foot, but as you go out the distance becomes greater as the radius increases. In that case you might find some stuff close enough to the center of the tree to avoid the worst twist, and far enough out so that the reed curvature in a brace would not be too bad.

Our local 'Red' spruce often starts out with a tewist in one direction, and then reverses as it gets bigger. It's just like the 'stripe' figure you see on tropical woods, but slower to change from one to the other. There will be nice areas of no runout in wood like that.

You can actually use tops that have a pretty large degree of runout, so long as you can keep it from showing along the center join. Sometimes, in the case of a tree that twists more as it gets older, you can use a 'heart match'; joining the halves of the top along the edge that was toward the center of the tree, rather than along the 'bark' side, which is the usual way. This won't work for archtops, usually, but sometimes you can do it on a flat top.

[John Hamlett]

For archtops, with the carving that goes on that exposes end grain to one degree or another, I feel like quite a bit of twist is acceptable as long as the wood is cut for minimal run out at the center seam. That results in more waste and obviously less yield from the tree. I'm having trouble visualizing the amount of twist trying to think in "degrees". I assume the 60cm is the length of the piece? What is the measurement from heart to bark, and if you lay the piece on a table with 3 corners touching the table (or as near as possible) how far from the table is the 4th corner? Whatever that is, it's the amount of run out that would be at the outer edge of the top plate.

[Samuli Samuelsson]

Hi.

Thanks for taking the time to answer guys. Appreciated.

The thing is, from a quartersawn piece, it's pretty difficult to determine the twist the trunk had, right?
At least with my rather untrained eyes.

I'm having trouble visualizing the amount of twist trying to think in "degrees". I assume the 60cm is the length of the piece? What is the measurement from heart to bark, and if you lay the piece on a table with 3 corners touching the table (or as near as possible) how far from the table is the 4th corner? Whatever that is, it's the amount of run out that would be at the outer edge of the top plate.

Yep, 60cm is the lenght.

I'm a BeEng Mech so I tend to think eveything in drafting, metalworking and construction terms .


I didn't take any precise measurements and didn't do the math, just eyed the pieces, but I'd say that with a 25 cm wide (from heart to bark) 60cm long piece, the 4th corner rides 6-7cm high.

The piece was from about 2.5m height, and I intended to use the lower portions as the trunk isn't excactly huge. Well not huge from instrument making viewpoint, I nearly tipped my Nuffield when carelessly swinging the lowest portion of the log with the ancient Hiab loader .
Even the quarters I made with the aid of a chainsaw were a handful.

[Clay Schaeffer]

On the frets.com website Frank Ford has a section in his illustrated glossary that explains runout and it's possible effects on the top.
If you split the wood and allow the twist in the grain to follow the shape of the arch of the top you may get an acceptable top. It might not be possible to book match it and still do this, but if you are willing to forgo this cosmetic consideration it might work. One of the major criticisms of runout in tops is the lack of gluing strength for holding bridges, which is not a consideration for an archtop.

[Tom Harper]

I've got an article saved from 2005 that has info provided by Larry Davis, Bruce Harvie, Larry Stamm, and Mario Proulx regarding their experiences with runout. For those that don't recognize the names since several are not active on mimf anymore, the first 3 are wood dealers with great reputations. (EDIT:Just to be clear that I am not slighting Mario - he is not a wood dealer as far as I know, but contributes valuable info in this exchange and of course builds great sounding instruments.) The series of exchanges is saved in a MS Word document. Can I repost this article, and if I can, can I repost the entire exhange as 1 entry rather than creating replies for each original reply? It contains 35 posts and is about 7000 words long. Oh, it also contains photos. Did I read that there is a 3 photo limit per post/reply?

[Greg Robinson]

Tom, if the file is available somewhere on the web, feel free to post a link to it.
In terms of posting it here, as you are not the author of the article, you cannot post it here due to copyright concerns.

[Tom Harper]

Hi Greg,
I did not make myself clear enough. The information is a saved mimf thread from Feb. 10, 2005 titled "How Much Twist is Permissible for Topwood Plate Resaw? ", so I am not sure the copyright issue applies. It contains quite a bit of information regarding grain runout that I think might be of interest to all those following this thread.

Clay, you may remember this thread. I posted about some average sounding wood with more than average runout I ended up with. Your suggestion that it's a bad idea to use average wood for a handbuilt instrument is what I have followed.

Greg, there may be another option to get this info posted. I am guessing that the thread may have made it into the library archive, so if the port of the library is successful, the thread should be once again available. I can't remember when the library backlog started.

[Greg Robinson]

Tom, the library port is coming along well, and the new library should be available soon.
Rather than posting that thread again, please hold off until it becomes available with the new library.

[Clay Schaeffer]

Hi Tom,
I don't remember that article very well. Any chance you could send it to my email?

[Bill Raymond]

Actually, there are a number of articles available in the old library concerning runout that you may want to consult, although the article mentioned above doesn't appear to have made it into the library. http://mimf.com/library/catalog_wood.htm#wood

[Tom Harper]

Hi Clay, I'd be happy to. Check your private messages please.

Bill, thanks for looking. Hmm, there must be a daunting backlog if something from 2005 is not in the currently available threads.

[Bill Raymond]

Tom, just because I didn't happen to see it in a cursory look doesn't mean it's not there! <G>

[Clay Schaeffer]

Hi Tom,
Thanks for emailing me that discussion. Hard to believe it has been 7 years since that posted. I wonder if the buying public has become more or less picky about runout since then?

[Tom Harper]

Bill, I checked after you and had the same results. I don't think its there.

Clay, probably not, but I am hoping that one of the effects of CITES and the Lacey act will be an increasing open mindedness about what is or is not acceptable for instrument building.