Flattening A Warped Reed Pan

[Don Taylor]

In another topic Chris advised:

 

 

Were you successful in removing the warp and if so how did you do it?

I dont know yet, but it is promising so far. I have it clamped to a flat surface in a well hydrated atmosphere. I need to replace some end bolts and a missing end bolt insert before I can try it out. But there are lots of other issues to work on. I expect that I will need a tuning rig too so thanks for this information and the videos.

 

If this doesn't work, get a thin piece of material, a worn sheet for example, dampen it (less is better) and put it between the concave side of the wood and the flat surface. It will flatten out within a day or so.

 

I followed Chris's advice and my warp is almost gone. The first 3 day compression session reduced the warp from about 3/8" to 1/4", the second session with re-wetted cloth, took it down to 1/8" and I have now put it back for its 3rd session.

I used a piece of plate glass, a thin cotton handkerchief, a plywood form and six clamps tightened snugly but not real tight - just enough to flatten the warp.

A couple of pictures:



and



A man can never have too many clamps!

Thanks for the tip Chris.

Don.

Edited December 23, 2015 by Don Taylor

[Geoff Wooff]

Let's hope it stays un-warped.... good luck with that Don.

[Jake Middleton-Metcalfe]

hmm I have often wondered about this - I have some old reedpans I took out of a busted lachenal, they have a slight warp. Surely the rest of the instrument would hold it in place in a way that compensates for this? So long as the support blocks in the bellows frame are positioned in a good way or am I wrong on this..

[Don Taylor]

Jake

 

I suspect that my reed pan warping is more extreme than you would experience in the UK.

 

My LHS reed pan was badly warped when I bought the concertina. Two of the support blocks had broken off and one of the end-bolts and its insert was missing - presumed killed by a previous owner when over-cranking. The reed pan was basically unsupported, it was actually twisted inside the bellows of the concertina.

 

I know that the concertina was stored for years in this state in Ontario where the summers are very humid (sometimes >90%RH) and the winters indoors are very dry (sometimes <20%RH).

 

The RHS reed pan is fine, all support blocks and end bolts in place and everything is flat and sealing well.

 

I replaced the missing support blocks on the LHS but I am unwilling to really crank down on the end-bolts to try to flatten the reed pan in situ until I have the pan in a close to flat state.

 

Also, I am still missing an end bolt and its matching insert - which is my next problem.

[Chris Ghent]

Don,

 

the number of clamps needed in any shed is the number you already have plus 10%..!

 

A couple of words on the subject of removing warps by adding water to the concave side. It is my experience water is easily lost to lack of humidity and takes a long time to go back in when it is humid. In addition, it does not always re-enter the wood evenly. Once it is flat if you look you will see it may undulate. I don't think this is going to be an issue with a reed pan as it the partition heights are easily adjusted if needed but it can be with a padboard. Which brings me neatly to my other topic. I have not found a Lachenal with a warped reedpan which did not have a corresponding bend in the padboard. I don't know if it happens because the same lack of humidity affects both or because the reed pan forces it upwards. Should this be true in yours you will find it does not seal well when you reassemble it. The same method for de-warping will work with a padboard though it might not be completely flat afterwards, as mentioned above and you may need to flatten it a little on sheet of sandpaper glued to a board. Figure eight pattern, making sure you are not putting more pressure on either the leading or trailing edge.

 

20% humidity is terribly dry, I put all exposed good bits in a mildly humidified environment if the hydrometer goes under 35%

[Jake Middleton-Metcalfe]

Ah, Don I didn't count for the different climate. Sounds pretty extreme

[Don Taylor]

Chris

I think that my pad board is OK. This is a Crabb from the mid 1950's and the pad board is made out of laminated layers and it is flat.

 

Jake:

 

We get extremely low humidity in the dead of winter when the outside temp somtimes goes below -30 for a few days. Air at this temp does not hold much moisture and when it is heated to a comfortable temp for humans then everything, including humans, dries out. We run a humidifier for us and keep a moisture source inside the instrument boxes. This is why Greg always warns us about the onset of winter each year, his warnings do not apply to the UK except maybe to Scotland. I do not remember any lack of humidity when I lived in the UK.

 

 

 

 

[banjojohn]

I presume that correctly seasoned timber will have a 'memory' for the humidity level where it was seasoned and stored prior to being made into a reed pan... Don, I do hope that by maintaining a typical 'UK' level of humidity, given time of course, that your reed pan will stay flat enough, to once again become part of a functioning instrument.... I wish you good luck, from a very grey, damp and humid Oxfordshire!

Edited December 24, 2015 by banjojohn

[Don Taylor]

John

 

I think that I am going to be OK, it does not take much pressure on the pan to flatten it out now. Dave Elliot advised me to leave it as is and raise reed chamber walls with strips of card or wood. I tried this but the original gaps were too big and I could not extend the wall height with stability. At the end of the day, I think that I may still need to do this but only for a smal distance on a few of the reed walls.

 

FWIW. This is what I think happened. It is a canted reed pan and I suspect that someone put it back in the wrong orientation and cranked down on the end bolts breaking off two of the corner blocks and breaking the brass end bolt insert. A subsequent owner then tried to seal the subsequent leakage by padding the tops of the reed pan walls with lots of felt which twisted the reed pan even further down on one side. Then it was stored away until they put it up for sale as a non-working instrument.

 

Moral: Be very careful to put reed pans back in the right orientation and no cranking on the end bolts.

[Dana Johnson]

Corner blocks coming loose is all you need to allow a warp. I can't see how you can incorrectly orient a reed pan and still have any of the notes right. A canted reed pan misoriented and screws reefed on could dislodge the blocks, but you'd understand the mistake as soon as you tried to play it. In any case, old glue and very dry conditions are enough to break loose a corner block. And once gone, the reed pan is free to do what it wants. Reed pans ( and glued in pad boards like Chris mentions ) warp because they are full of bracing ( partitions or chamber walls ) that are oriented at various angles to the grain of the pan. Stress exists at any humidity level other than that of manufacture due to the differential expansion or contraction between long grain and cross grain. End clamping can restrain that stress, and natural wood creep over years can relax it at a new ( constant) humidity level , but it is a consequence of the traditional design. Once re flattened, re blocked and re assembled you are good as long as you pay attention to humidity. The general rule is that if you take a reed pan out for any length of time other than that needed to fix a valve or tune, you clamp it between blocks to keep it flat or it will want to move on you. ( this doesn't apply to Kensington reed pans which are made differently )

[Wally Carroll]

Sorry to be a little late on this . . . In my experience the only way to really keep it flat is to somewhat crush the wood fibers by bending it in the opposite direction. See photo.

 

A few notes on the process . . . Make sure the paper towels are damp and touching the pans. A damp sponge would probably work better. Apply a small amount of pressure to start the flattening then walk away for an hour. Add a little more pressure and redampen towels if needed then walk away for another hour. Repeat this process until you go about 1/8" - 3/16" past flat. Remove towels and leave for 24 hours. Next day remove all pressure and let it sit for a few hours. You may need to reclamp and take it even further.

 

Please be extremely careful when doing this as you can easily crack the pan!

Edited January 6, 2016 by Wally Carroll

[Wally Carroll]

Sorry, can't get the photo to attach. I've tried several times now. It might be too large. Anyone know how to lower the resolution on an iPhone?

[Bruce McCaskey]

There's a free iPhone App called Simple Resize that will reduce pixel resolution. Lots of advertisements in it but it works. Of course, close cropping helps reduce overall photo size too if it won't impact the value of what you wish to convey.

 

Here's an example of a photo processed by the mentioned App, before (about 175 KB) and after (about 42 KB).

 

You can pick how much reduction you want, I chose a substantial reduction to illustrate the possibilities. By the way, the image may not look smaller on on your iPhone after reduction because that device always fills the screen, but you'll see that the detail degrades if you compare before and after versions. You will likely see a maximum physical size reduction when you post to this forum.

 

Because you were having trouble attaching the photo, I might also just comment on the process for clarity. First use the "Choose File" button to select the photo from your collection, then use the "Attach this File" button to make it "stick" to the post - you have to do both steps. So long as you are under the 1.95 MB size limit for attachments you should be OK.

Edited January 6, 2016 by Bruce McCaskey

[Wally Carroll]

Thanks Bruce! I think I was missing the second step. I was choosing the pic but didn't realize I also had to to hit the attach button.

[Wally Carroll]

Thanks Bruce! I think I was missing the second step. I was choosing the pic but didn't realize I also had to to hit the attach button.

[Don Taylor]

Thanks Wally, I may need to do this and your picture tells the story.

 

Interested to see that you rout out the reed chamber walls from solid timber, one of the advantages of a CNC router I guess.

[Wally Carroll]

I recently made this change to both the reed pans and action/pad boards in order to better keep the pieces from warping. It works really well. That being said, warped pieces are often not a problem as they are usually flattened out sufficiently when the instrument is bolted together. I would only go the route I outlined above if you are unable to get a good seal after bolting the instrument together.

[Don Taylor]

Thanks again, Wally.

 

I noticed that in one of your Youtube videos you use something other than chamois leather[*] for your gaskets. About 1:36 in to this video.

 

Would say something about this.

 

Thx. Don.

 

[*] Maybe they are chamois leather - but from black sheep...