Im asking this question to help me and anyone else who may have a similar issue.

Are there any methods of restoring atlest minimal downbearing to a soundboard?

These methods are an act of desperation before soundboard replacement or to save an old piano that isnt worth soundboard replacement.

My current project is one not worthy of a soundboard replacement.

Soundboards have crown, strings have down bearing. Between the string and the soundboard is the bridge. The bridge could be replaced or the plate lowered to increase the downbearing. But if there is insufficient crown, the soundboard may "invert" and then have negative crown.

What has been suggested is to make the soundboard stiffer, which is what crown is all about, with an epoxy treatment or with "riblets". But the present downbearing/crown may simply balance each other to nearly zero when under tension, and not be problem at all.

So let me ask you a question. Why do you think the piano will sound better with more crown and downbearing? It might never have sounded good in the first place!

Oh, I forgot another treatment. Engine valve springs have been installed on brackets mounted on the backposts and pushing on the ribs. Supposedly it does work!

As I said before, you are worrying about this too much. Put the piano back together and see how it comes out.

Not very well.

ddf

Shhh...

The piano sounded ok. loose bass bridge and old bass strings made a tubby bass. It had poor sustain, no volume(couldnt even get as loud as a wurlitzer spinet). How is the epoxy treatment or ribblet procedure done? Is putting it all back together worth loosing $250 in strings? What kind of sound am I going to get with no downbearing?

lol

Just curious Amature (sic): How many threads do you intend to start about your soundboard bearing and crown?

As many threads as he requires;

AR if the piano sounded ok before you began working on it, the sound will be the same; a bit cleaner because of the new wire and all; the bass section should be much improved with the improvements you have completed there.

As BDB stated you worry too much; just re-assemble and see what you have. If the project is not worthy of sounding board replacement then it is a moot point.

Remember that people who don’t make mistakes generally don’t make anything at all....

I don’t know what you refer to when you state “epoxy treatment or ribblet procedure”

I have decided just to put it back together, it should sound a little bit better since I repaired the loose ribs. It also will hold a tune well, and Look decent. I would like to get some new hammers for it, anyone know of a place you can get cheap hammers?

Tomorrow Im going to replace the understring felt and start the restringing process.

Farther down the front page of this forum there is a thread about supply houses. You will find hammer sets there.

I would let the glue dry before you begin stringing or the pressure will force the glue to soak through the felt and rust out the wire.

yeah I could leave the original felt in but its faded and ugly my only problem is when I orderd the felt I forgot about the felt in the bass section so I may have to leave it out somewhere

Hopefully you are keeping track of time spent and parts purchased on this project. It's important to track costs so you end up making a profit in the end.

Not for an amateur, nor for a beginner. The most important thing is to get it as close to right as possible. You should not be rushing through the job, nor should you stint on the job until you have a better feel for this sort of work.

This is the BEST interaction I've seen on here in a long time. Bravo!

I will at least break even. Since this was my first I had to get a lot of new tools I wont include that in the price when I do sell this.

I went ahead and took a trip over to the shop and glued the under string felt to the plate so the glue will be dry tomorrow, I will also have to do some trimming is some areas.

It still amazes me how much hide glue smells like wet dog witha hint of pepper.

Interesting definition of "OK" sound!

This is what my piano sounded like before I did anything to it. Tell me what you think.

Im glad I can play the piano better than that now lol

Hey I just posted a link to a vid of the piano before I did any work

The first refers to soundboard treatment I described in a series of articles that appeared several years back in the Piano Technicians Journal. Very simplistically it describes a technique of using very thin coating epoxy to fill minor cracks and stiffen the soundboard panel without adding any appreciable amount of mass to the system.

The second refers to an article written by my brother in the same magazine several years later. Again, very simplistically, it refers to a technique of adding short, auxiliary ribs—i.e., riblets—between the existing ribs to stiffen the area most affected by compression failure within the soundboard panel. I have also used them from time to time to stiffen the area at the end of the tenor bridge to lessen the “end-of-the-bridge” effect.

ddf

Yes of course; this had slipped my mind, I recall having this conversation with Darryl when he was here. I have also read some materials on this forum about the process. Thanks for the reminder.

I've used epoxy to fill cracks and it worked quite well. I'd dry the soundboard out for 36 hours with dry heat, which opened the soundboard cracks as wide as they would go. Then, I'd fill the cracks with epoxy, which dried before the cracks closed up. That prevented filled cracks from opening up again during dry winters, and I suppose added tension to the sound board.

I don't think I'd use heat with moisture, though. That might loosen up ribs, and other glue joints, I would think.

Did you measure crown in the board and string bearing at the bridges before you took it apart?
Does the board have any crown on it after taking it apart?
If it does, best thing you can do when you reassemble is to set absolutely minimal bearing - maybe only 1mm across all of the bridges.
Don't do this in a cool damp shop.

On a QUESTIONABLE OLD sound board.

Dry the sound board to 5% to 5.5% EMC.

Measure your crown.

What ever that number is, you can not have any more bearing than that.

If you have 0 crown at that point, then set your bearing to 0.

If that is the case, I would hire Del for some thoughtful help in stiffening the board.

The rest will be your understanding of what hammers you use and how you make them work with your sound board choices.

Are these what I think they are?

Nice description, isn't it?

One thing you could do is roughly measure the existing crown on the board and do tests by stringing a single (or a few) plain wire strings to see where it's at.

See what it sounds like by sliding the action in and listening to the tone in that region and checking with your downbearing gauge. Poor tone results from lots of things, not just poor crown, so listen to see if you can isolate how the soundboard crown is affecting the tone.

If you want to experiment, you can also remove the board from the inner rim, then add compression when reinstalling by drying the board, reinstalling, and shimming/clamping around the edge before raising the humidity carefully to see if you can increase the crown. Measure and test like before.

Other options are experimenting with reinstalling new radiused ribs, but this, like many other piano design factors, is hard to test and change once you do it. Many rebuilders just guess what will produce good tone and go with it - based on past success and their experience.

There is no number for good crown, but there is a number for a specific piano (optimum region). What you want to do is balance the potential energy stored in the soundboard with the potential energy stored in the strings (based on the mass, length, elasticity and tension of the scale).

I hope these thoughts are helpful to you and spur freedom and experimentation.

Probably, but minus spring, jaws and screws.

OK, I need some clarification on this. What units would the crown be measured in and what units would the down bearing be measured in. I could see someone measuring 1/8 inch of crown along a 5 foot rib and then setting 1/8 inch downbearing over a 1 inch length of string!

Jeff,
What note are you asking about?

No particular note. Perhaps if you gave example it would be good.

There are very few 5 foot ribs.
Few notes have a back scale of one inch or less.

It should be plain to see the vertical measurements of crown vs bearing.

It would be helpful to start there if that seems vague.

Great! Then could you give an example of vertical measurement of crown vs bearing?

That one is too easy Jeff ... I will insist on leaving that one to you.

Well, its just one more thing that has not been adequately explained. I have not done it, so I don't want to lead anyone astray.

Pete,

It is not my intention to be elusive.

Down bearing is only one of several considerations when deciding on the voice of a piano.

One could write an entire paper on that subject here on PW.

Also, to only look at bearing, without an understanding of the entire relationship, risks failure. I don't want to oversimplify nor do I want to "write the entire paper" here.

Many technicians work a lifetime for the understanding of this relationship. They can be hired. It is not wise to give the entire thing away here.

Try things, gain experience. Practice on pianos of no consequence. We all did. Attend the PTG conventions. Over time, one will acquire the understanding.

Larry:

Then it is not as simple as your earlier posts suggested, and who is Pete?

Not exactly what I am saying.

"Pete", I meant Jeff

Then for "Pete's" sake, what exactly ARE you saying???

Jeff, I think I may have called you Pete before ... I am a recovering Blond.

In the OP's situation, I would venture the ONLY consideration is preventing too much bearing and risking reverse crowning the board. Other than that, he should take all the bearing the crown of that board will let him have reasonably.

In a perfect world where one has control over ALL the parameters ?? Del has described the considerations used in this process as well as anyone can.

To write at length on my specific choices here is simply not wise.

From time to time, I have a piano here I have put a lot of work into. It is good to play those. They reflect the summation of my choices and I can speak about those choices in context.

Roy123 recently had the opportunity to play a Baldwin L and write about it on the Piano Forum. That piano is still here for anyone to play and examine. Playing that piano puts into context my choices. That Baldwin L will here for maybe another week.

Larry:

OK...

Would it be wise, on your part, to just explain how someone might: "take all the bearing the crown of that board will let him have reasonably"?

Otherwise, why did you even post? Just to say you really won't explain anything?

Measure the crown.

In this piano, that vertical distance is ALL you have in down bearing.

I said this right at the beginning.

I might not go all the way to zero BTW if I thought I could get away with it.

A Soft light hammer properly voiced will make the most of that situation.

The rest of the answer must be in the trial and answer process.

There is a lot of discussion about "proper execution". The Trial and error process is what sorts all that out.

As good an answer as can be given right here IS the simplest and least wordy.

Next step .. do it and listen.

Here's an instance of to much down bearing


<http://leacocks.com/FeaturesBlog/wp-content/upLoads/2011/11/crushedpiano.jpg>

For this old board inside of this old piano, if it does have - for the sake of numbers - 1mm of crown and the plate height is set so the strings are deflected by the bridges by 1mm, when the strings are brought up to pitch, the board may not be deflected by 1mm - possibly less. Not likely on an old board but possible.
The good news is that it could not invert.