Glueup Worry?

[Canuck]

I am gluing up some 4/4 cherry for a small table - 18" square. The boards I selected are 6", 8", 6" wide for the rough top blank. Do you you guys think that I may end up with problems with cupping with the 8" width board over time? I am edge gluing with 3/8" dowels for alignment. Cupping is what I am really concerned about. (The wood is good and dry - right now.)

1st time I have worked with cherry!

Thanks a lot

Wayne

 

[DavidF]

Wayne - I would rip the board and re-join. Two reasons; one is cupping, I have had a lot of movement in the 8" wide cherry boards I am using for the bed rails and I did then rip to 4 1/2" and join. And Two, anything less that 6" will enable you to surface plane on a small 6" jointer. You may of course have a bigger bed size, but the first reason still applies.

 

[DaveO]

If the wood is flat now and dry and you are working with it in the same environment that the finished piece will live in (air-conditioned/heated) then you shouldn't have any problems with cupping. BUT if any one of those factors isn't included then you run the risk of the wood changing it's MC and possibly cupping/bowing. A good rip down the center of the wide board will be hardy noticable, and you will sleep better...althought that still doesn't guarantee that cupping won't happen.

Dave

 

[Canuck]

Thanks DavidF and DaveO!!!!!

Thats exactly what I will do......... Rip and join!

(Your right on the money DaveO, in reference to the environment. My garage is warmer and more humid than where the table will end up.)

Thanks again guys!

Wayne

 

[DavidF]

Thanks DavidF and DaveO!!!!!

Thats exactly what I will do......... Rip and join!

(Your right on the money DaveO, in reference to the environment. My garage is warmer and more humid than where the table will end up.)

Thanks again guys!

Wayne

For the same reason I have been ferrying the wood back into the house at the end of each working session. It's so much more humid in the WS than in the house at the moment so I imagine lots of movement taking place if I left it in the shop and then brought it all in the house after several weeks.

 

[Howard Acheson]

I'm a little confused. Ripping a 8" wide board down the center will have no affect on its propensity to cup or warp. If you rip it into two 4" boards and reglue them, it will still warp. If you rip it into two 4" boards and reverse the endgrain orientaion, and it warps, you will end up with a wavy board. Ripping the board has no affect on whether it will warp or not.

If the board is dry and flat now, use it in its full width. Lumber dealers get a premium price for wider stock. Why mess it up with a glueline in the center of each board? Using a lot of narrow boards for a panel is a sign of less than stellar furniture.

Let me also suggest that you do not need any dowels. They add no strength and unless perfectly drilled, will not even help in alignment. Just go ahead and edge glue the boards into your panel. The glue joint is as strong or stronger than the wood itself.

Finally, when you attach the panel to the support structure, it will prevent the top from cupping.

 

[DavidF]

I'm a little confused. Ripping a 8" wide board down the center will have no affect on its propensity to cup or warp. If you rip it into two 4" boards and reglue them, it will still warp. If you rip it into two 4" boards and reverse the endgrain orientaion, and it warps, you will end up with a wavy board. Ripping the board has no affect on whether it will warp or not.

If the board is dry and flat now, use it in its full width. Lumber dealers get a premium price for wider stock. Why mess it up with a glueline in the center of each board? Using a lot of narrow boards for a panel is a sign of less than stellar furniture.

Let me also suggest that you do not need any dowels. They add no strength and unless perfectly drilled, will not even help in alignment. Just go ahead and edge glue the boards into your panel. The glue joint is as strong or stronger than the wood itself.

Finally, when you attach the panel to the support structure, it will prevent the top from cupping.

I have to disagree there Howard; ripping the board changes the grain orientation with respect to the faces and the cupping is much reduced; not totally eliminated, but much more manageable resulting in the need to plane off less of the thickness of the board to flatten if it does move. I also must disagree with your "Using a lot of narrow boards for a panel is a sign of less than stellar furniture." I would rather have the boards ripped and stable than have a massive cup after a change in humidity. If wood was as stable as you suggest then we wouldn't need MDF and veneer:lol:

Note - any criticism is too be taken in the light of a "discussion" and not to be taken personally

 

[BobN]

I'm a little confused. Ripping a 8" wide board down the center will have no affect on its propensity to cup or warp. If you rip it into two 4" boards and reglue them, it will still warp. If you rip it into two 4" boards and reverse the endgrain orientaion, and it warps, you will end up with a wavy board. Ripping the board has no affect on whether it will warp or not.

If the board is dry and flat now, use it in its full width. Lumber dealers get a premium price for wider stock. Why mess it up with a glueline in the center of each board? Using a lot of narrow boards for a panel is a sign of less than stellar furniture.

Let me also suggest that you do not need any dowels. They add no strength and unless perfectly drilled, will not even help in alignment. Just go ahead and edge glue the boards into your panel. The glue joint is as strong or stronger than the wood itself.

Finally, when you attach the panel to the support structure, it will prevent the top from cupping.

Wayne, For what it's worth I agree with Howard. Why on earth rip a 8" board if it is truly flat, (if it needs to be flatten any, bring it down and run it across my DJ-20). I assume that this is the cherry that you got when we went to Gibsonville, if so it should be very stable by now and I don't think you'll have any problems with it. Just got to remember to fasten it in a manner that will allow for some movement. Also agree with Howard about the glue up, you don't need any dowels, they will just add to your problems.

Bob

 

[Alan in Little Washington]

Wayne, in order to answer whether it will cup or if it should be ripped first, we need some more info- what is the grain orientation on the cherry? Flat sawn may have a tendency to cup; quarter or rift sawn much less so. Is it dry? What % moisture. How thick is the cherry and what will the final thickness of the top be? Is it flat now? If the cherry is 4/4 or thicker and the finished top is to be 3/4, then you can afford to run it across a jointer first to remove any initial cupping, and if over 4/4, you'll have some additional thickness to run the laminated top through a planer to bring it down to final thickness. With today's glues, long grain glue ups are as strong or stronger than the wood itself- dowels and biscuits are not needed and may make it harder to align the boards and get a flat top if not precisely done. Edge gluing with good clamps (Besseys), C-clamps (or similar) across the joints at each end of top, plus cauls across the middle of the board should leave you with a top that may only need a scraper for final flattening. Oh, depending on the conditions where the wood is store and in your shop, let the wood aclimatize to your shop for a few days before and after machining. This second "rest" period should let you know if there were any internal stresses in the wood released during machining. It will be an indicator of further warping or cupping.

 

[DavidF]

Wayne, For what it's worth I agree with Howard. Why on earth rip a 8" board if it is truly flat, (if it needs to be flatten any, bring it down and run it across my DJ-20). I assume that this is the cherry that you got when we went to Gibsonville, if so it should be very stable by now and I don't think you'll have any problems with it. Just got to remember to fasten it in a manner that will allow for some movement. Also agree with Howard about the glue up, you don't need any dowels, they will just add to your problems.

Bob

What might be a flat 8" wide board today won't necessarily be tomorrow. I still say a ripped and joined board will be more stable and no amount of structual reinforcement is going to stop it.

A discussion on the problem - many different thoughts - you choose..

http://www.woodweb.com/knowledge_base/Preventing_Cupping_in_a_Wide_Board.html

 

[DavidF]

Wayne, in order to answer whether it will cup or if it should be ripped first, we need some more info- what is the grain orientation on the cherry? Flat sawn may have a tendency to cup; quarter or rift sawn much less so. Is it dry? What % moisture. How thick is the cherry and what will the final thickness of the top be? Is it flat now? If the cherry is 4/4 or thicker and the finished top is to be 3/4, then you can afford to run it across a jointer first to remove any initial cupping, and if over 4/4, you'll have some additional thickness to run the laminated top through a planer to bring it down to final thickness. With today's glues, long grain glue ups are as strong or stronger than the wood itself- dowels and biscuits are not needed and may make it harder to align the boards and get a flat top if not precisely done. Edge gluing with good clamps (Besseys), C-clamps (or similar) across the joints at each end of top, plus cauls across the middle of the board should leave you with a top that may only need a scraper for final flattening. Oh, depending on the conditions where the wood is store and in your shop, let the wood aclimatize to your shop for a few days before and after machining. This second "rest" period should let you know if there were any internal stresses in the wood released during machining. It will be an indicator of further warping or cupping.

You see what happens with this woodworking lark... The poor guy askes a simple question and boom; totally confused:lol: :lol: :lol: :lol:

 

[Howard Acheson]

>> ripping the board changes the grain orientation with respect to the faces and the cupping is much reduced;

Not sure I understand. How does ripping change the grain orientation? Even if you flip the sawn boards, the grain orientation remains the same. Changing the end grain orientation does not change the magniture of the curvature of that board. It just divides it between two boards. One will curve upward and the other will curve downward. Again rip the board down the center, again flip the boards and you will have the exact same curvature as you would if you never ripped the board at all.

>> "Using a lot of narrow boards for a panel is a sign of less than stellar furniture." I would rather have the boards ripped and stable than have a massive cup after a change in humidity. If wood was as stable as you suggest then we wouldn't need MDF and veneer:lol:

Let me ask why wider boards carry a premium if narrower boards are preferred on panel glue ups? I have never seen a top notch custom furniture manufacturer or workshop rip a wide board into narrower pieces. In fact, those workshops sell the fact that they do not do that and therefore have much nicer looking panels.

I will say again, that wood that is properly dried and has been acclimated with not tend to warp even with reasonable swings in long term relative humidity. The only possible issue might arise is if the panel was built in coastal Carolina in August and shipped to Phoenix in the winter. Even there a 1" or less thick cherry panel will be held flat by the attachment to the underlying frame. BTW, I did that two years ago and there has been no warping what so ever. In the shop I was involved with outside NYC, we shipped all over the US for a high end interior designer. We built so the items would be at home in various environments--and never ripped a wide board. I remember one time we had a panel warp. We came to find out that it has sat on an closed moving van for over three weeks in the middle of the summer. We brought it back stickered it for a couple of weeks, refinished it and sent it out and had no further trouble.

I know many folks believe that ripping a board into narrower boards is the right thing to do. That's OK, but I'm not one of them. In this case we are dealing with a 18" square panel for a small table. I can't see how it will warp if it is properly attached to the table framing.

 

[DavidF]

It may have been the incorrect explanation, but if you imagine the end grain of a piece of flat sawn wood with the curves of the growth rings centred on the board. Cup is caused by the stresses that are present when a portion of the ring is removed when the board is cut in thickness. I tend to imagine that the two parts of the ring that were parted are "trying to get back together" -Ahhh. This is why boards will generally cup away from the direction of the circle of growth rings. In our example, that would result in the two sides of our piece cupping towards each other giving a pronounced bend across the width of the board. Now take that piece and rip it down the centre at the crown of the growth ring pattern. The gap caused by the remaining "broken" rings is now lying at an angle to the face instead of parallel to it; the resulting stresses will cause the wood to try and form a "lozenge" shape, not a face cup. In addition, the amount of cup is generally proportional to the distance between the "broken" parts of the growth ring. In the ripped board the distance is smaller; hence less cup in the one piece.

To take your second point; wide boards are still a desirable thing simply because of matching grain patterns. Joining two unrelated boards will result in an "unnatural" grain pattern; ripping a wider piece and rejoining will result in an almost invisible change in the original grain pattern.

In general, depending on the species, this whole argument is probably mute on anything less than 12", but in my experience with Cherry it is very prone to cupping and again, only in my experience and that is what this forum is all about, the results are better when a wide board is ripped. You and I have obviously had different experiences with this phenomenon over the years and that unfortunately is the nature of the beast we insist on playing with.

 

[Gofor]

Speaking only from my experience, I have several pieces of pine furniture that I made with tops made from edge-glued boards 3/4" thick. Center board is 7 1/2"wide, side boards are 4 1/4" wide. Top is attached to carcass by a row of dowels down the center line. Top has 3 coats of poly on top, and 1 coat of poly on bottom. Temp has remained somewhat constant between 60 and 80 degrees since construction. Humidity has changed drastically from normal A/C (probably around 50%) to open windows and 90% humidity when the weather cools. Pieces were glued , assembled and finished when the temp was varying between 50 and 80 degrees aand humidity between 60 and 90% (unheated garage). No problems with warping or cupping. I did alternate the growth rings on the edge-glued boards.
Pine has a lot more tendency to cup and warp than cherry. If your finish is not moisture resistant, it will cause more impact, but if it is a usable top surface, it will have some moisture resistant properties. Coating the bottom as well as the top will minimize warpage/cupping.

My $.0002:lol:

 

[jeff...]

Don't worry, be happy :-D try and edge glue the boards no wider than 3" so they are smiling at you like this UUUUUUU.