Recommended Posts

Did you measure the wood properties before starting to carve this one?

I usually cut the F-holes very early, so my taptone data is not directly comparable... but still, it looks heavy/low-stiffness from here.  It also looks like you have some very "hard" (in a visual sense) grain lines along the center of the plate, which I would definitely try to avoid, as I have seen that give locally very poor stiffness/weight ratio as well as higher density.

Share this post


Link to post
Share on other sites

I did measure and that is the strange thing:

http://www.thestradsound.com/ongoing/bakingwoodforthesoil4

http://www.thestradsound.com/ongoing/heattreatedwoodemc

 

The only thing I know so far is that I tend to choose the wrong wood pieces for tops. I kind of fall for the "lively" pieces that rings high and that is not necessarily the ones that are good. Have to find a better way to choose.

 

What I know from the frequency patterns, before hollowing the inside, is that there where too many frequencies. 5-6 measurable with software and tone generator, The ones I usually follow where skewed and odd shaped. So there is definitely some inherit flaw in this piece. Also carving with a sharp gouge cross grains, does not give any clean chips, more difficult in the middle. M2 & M5 on the inside had normal patterns though.

 

post-37356-0-69437900-1481180804_thumb.jpgpost-37356-0-85498200-1481180827_thumb.jpg

Share this post


Link to post
Share on other sites

Took it down to the usual M5 and it ended up 87 g, 3,5 - 3,7 mm thick. definitely firewood.

 

post-37356-0-06341600-1481214279_thumb.jpg

 

Extrados frequency chart (without numbers). Usually there are two clear frequencies (sometimes a third), that are easy to find. On this top these are only some of them, the most prominent. There was also some in between. The red line corresponds to the Intrados M5. No matter what I did it just dropped.

 

post-37356-0-79710900-1481214392_thumb.jpg

Share this post


Link to post
Share on other sites

Looks like about the same taptone/weight that I got with my Walmart firewood... with the F-holes cut.  You mostly just have way too dense wood, but perhaps the crossgrain stiffness is low too.

Share this post


Link to post
Share on other sites

Hi Peter,  your top seems a lot like my #1 top.  Hard to carve or scrape cleanly.  I took the whole thing down to 3.0 mm before checking m2 and m5.  I forget m2 and I'm not even sure I did it right.  M5 was about 300 or a little under. :o   I definitely had an oh scat moment.  Then I thought well it's #1 just go with it and I left it at this thickness.  Final weight was around 62 g with bass bar.  M5 around 105.  Numbers are all from memory because my shop is boxed up for an upcoming move.  Anyway while I missed all my targets (weights ok) it sounds pretty good strung up with old dead strings.  I'll start getting into the setup after I get the new shop up and running.  Point is, the top may still turn out good.  Might as well try it and see.  You can always replace the top if it just doesn't work.  BTW, I usually can't follow your links from work.  I look forward to your pics when you post them here on MN.

 

Cheers,

Jim

Share this post


Link to post
Share on other sites

Point is, the top may still turn out good.  

 

There is nothing that would prevent it from sounding just fine... unless your "fine" includes lots of power and projection.  I think dense wood is not going to knock the socks off folks sitting in the back row.

Share this post


Link to post
Share on other sites

Occasionally top plates have aberrations making it impossible to determine the true frequency of the mode 5 of the extrados.

 

You should continue removing wood in order to see how the mode 5 frequency reacts in the different regions. Ignore mode 2.

 

www.kreitpatrick.com

 

 

I'll do that but there is also a second top on the way, even denser wood 0,48-0,49

 

As dens wood is not equal to heavy plate I hope for this one to be good enough (performance) to bring it down to about 70 g. This one is from 1999 and has been heat treated the usual way (160 C ~2,5 - 3 hours). Felt good under the plane and is yellowish all the way through.

 

post-37356-0-83946800-1481375820_thumb.jpg

post-37356-0-27592600-1481376324_thumb.jpg

post-37356-0-33587900-1481375889_thumb.jpg

 

I'm still not good at choosing top wood, but I think I have learned something (intuitively) because I chose the previous wood because it was different, evidently bad choice.

Share this post


Link to post
Share on other sites

Peter, it's not the computer, it's the security settings at work. No problems at home. At work I pop in and out of MN to rest my brain. I'm more productive that way. That's my story and I'm sticking to it. ;)

-Jim

Share this post


Link to post
Share on other sites

You should tell your IT manager that Maestronet and all violin making Sites are extremely good for productivity :)

(says me, who once was behind a decision to turn off facebook in our corporate network, complete stupidity)

Share this post


Link to post
Share on other sites

... there is also a second top on the way, even denser wood 0,48-0,49

 

I'm still not good at choosing top wood...

 

I'm not sure I see the attraction of such dense wood.  You can probably arch it very high and go 1.5 mm thick to get the taptones where you want them with reasonable weight, but I think it might sound a bit unusual, and the arching might be unstable.

 

I see Strad didn't use anything that heavy, and the few "golden era" examples appear to have densities on the lower side.

http://www.trioviolinproject.com/plate-densities/

Share this post


Link to post
Share on other sites

It's too dens for my taste too, but it was the best I had at the moment. It's difficult to find great wood. I have ordered a couple of times via Internet, but they where no good. Finnish wood tend to be dens but strong lengthwise. I also have some super wood that are not suitable for violin tops (0,55, 2LF gives over 6500 m/s)

Share this post


Link to post
Share on other sites

Heating the wood occasionally lowers the performances of top plates (but not those of the back plates). Instead of shrinking, some top plates increase in thickness by 0.5 mm. Longitudinal elasticity and celerity decrease between 2% and 5%, and transverse elasticity and celerity by as much as 18%. This may be the case with your top plate, despite a high frequency for the unworked wood (high longitudinal celerity).

 

I have used top plates with density as high as 0.50 at 6% MC, and they work. Beyond that level, it is just ordinary pinewood. 0.46 should be the limit at 6% MC.

 

Whether the density is high or low does not prove that the wood is good or bad. Its quality depends on the materials’ performances and, more importantly, on the ratio between transverse and longitudinal celerity.

 

www.kreitpatrick.com

Share this post


Link to post
Share on other sites

It's too dens for my taste too, but it was the best I had at the moment. It's difficult to find great wood. I have ordered a couple of times via Internet, but they where no good. Finnish wood tend to be dens but strong lengthwise. I also have some super wood that are not suitable for violin tops (0,55, 2LF gives over 6500 m/s)

Are you not able to order wood from dealers and giving them the parameters you're interested in?  I don't know if you have import restrictions or not where you live.

 

-Jim

Share this post


Link to post
Share on other sites

There is no restrictions, it's just that I have a friend with a big pile of wood. But he is not selling the good pieces anymore and I understand him because it is harder to get great wood noadays. I have to make a trip to wood dealers in Europe in the near future. Or maybe if I find one that can measure density and speed of sound before they send it.

Share this post


Link to post
Share on other sites

During roughing-out of the extrados, the top plate must be in equilibrium on the center of gravity. Only after that has been achieved are the nodal regions activated and the frequencies monitored.

 

If the masses of wood are bady distributed, the top plate’s nodal patterns are diffuse and it is generally impossible to ascertain the true mode 5 frequency of the extrados (with a generator or with software).

 

Two nodal region configurations exist on the intrados of the top plate: their frequencies  reverse during tuning of the extrados and the delta between these two frequencies changes. The higher the moisture content in the wood, the greater confusion there is between them.

 

Cut each new violin model out of cardbord or plywood and determine the center of gravity by placing the model on a pointed instrument: the model must hold its balance on the point.

 

www.kreitpatrick.com

Share this post


Link to post
Share on other sites

Patrick,

Did you develop some intuitive skills on how to choose wood, or just measuring? It seems to take forever knowing what you have. I did read your book again on top wood tuning and it was all there, but I did not understand it before I made the mistake(previous top).

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.