Some help with poplar stability?

[Fred Voorhees]

Gentlemen, I am about to start a dining room table for a friend and it will be constructed from poplar, which I will end up staining. Top will be between 1 1/2" and 1 3/4" thick. It will have breadboard ends and will be six foot long and roughly around 42 inches wide with various width boards composing the tops field. The individual boards will be joined using glue and splines. I am concerned about the expansion and contraction of the tops field in relation to the length of the breadboard ends. I know poplar is one of the more stable species, but I am in the dark as to how to relate the breadboard ends width to the possible reaction of the top field to the moisture variations from season to season. I have never worked with the expansion and contraction calculators on line and took a look this morning at them, but feel a bit intimidated by the process. Someone want to take on the challenge of explaining how these calculators work? I am a bit naive as to starting moisture content...final moisture content, etc that are the needed figures in calculating the growth or shrinkage of a chosen species of wood.

[Jerry Miner]

I noticed you are in NJ--so I looked here and found that the EMC range for nearby NY (NJ is not listed---don't ask me why) is about 11-13%. And this site calculates that you can expect about 1/4" of movement in a 42", flat-sawn, yellow poplar top in this range.

You WILL be allowing for this movement in your breadboard ends, yes?

[Frank Drackman]

Are the breadboard ends part of the design requirements by the client, or are you adding them to increase stability? I assume that the design has the the top boards running the 6' length, not the 42" width, correct?

[Jamie Buxton]

...I noticed you are in NJ--so I looked here and found that the EMC range for nearby NY (NJ is not listed---don't ask me why) is about 11-13%...

Careful -- that table is for wood which is outdoors. In areas which are cold in the winter (for example New Jersey), outside air gets heated when it comes inside the home, so it gets drier than outside. Therefore the EMC of interior wood in the Northeast is likely to be lower than shown in that table.

[John TenEyck]

Correct, the seasonal indoor RH change in NJ is likely 6% in the Winter to 14% in the Summer unless you have a humidifier in the Winter and AC in the Summer. Next you need to know what the MC of your wood is right now. Then you can calculate how much it will shrink and expand from where it is right now and allow for that as you build and attach the breadboard ends. In the end breadboard ends are only going to be flush with the field part of the year. You might also want to rethink using poplar for the top. It's pretty soft and will show every ding from dropped silverwear, etc. Maple would be a far better choice.

[Kevin Jenness]

Here in VT in a house with wood heat and no air conditioning the interior furnishings may swing from 5% (correlates to 20-25% relative humidity)in the winter to 10% (55-60% RH) or more in the summer. Just based on rules of thumb I would expect the tabletop you describe to be 3/8" or so wider in the summer here. In a warmer clime like NJ or with air conditioning or wintertime humidification the swing may be less. You should be able to discover the current RH in your friend's house and make an educated guess about what it will be in the summer.

Using the formula for wood movement is a matter of plugging in numbers, but you need to start with the right ones including the wood's MC at fabrication. To dispel with the math (thanks Marco) go to Woodweb.com and use the timber movement calculator (way down the left-hand side on the homepage).

To find your present MC get a moisture meter or do an oven-dry test with a precise scale. An hygrometer is also a valuable tool to have in the shop and it can be as simple as a wide short-grained cutoff of your tabletop with widths related to relative humidity.If you don't already have it, Bruce Hoadley's book "Understanding Wood" gives a good explanation of the issues of water and wood.

Breadboard ends are usually grooved to accept a stopped tongue milled on the ends of the tabletop. The tongue can be glued for several inches in the center and dry pinned through lateral grooves to allow cross grain movement. Sometimes longer tenons are used at intervals along the tongue.

[Fred Voorhees]

I'll answer everyone in one fell swoop in the interest of consolidation. Jerry - Yes, accounting for movement in the breadboard ends....but only involving one of two areas where I am concerned about expansion and contraction issues. The dowel placement through the breadboard piece and through the tongue of the joint, back into the breadboard end...that is a no brainer....going to solidly dowel the center of three dowel locations - the outside two - getting a dowel with the pass through in the tongue being elongated for movement. My issue is sizing the length of the breadboard end...accounting for the seasonal movement of the top "field". Being the colder and drier months right now...obviously the wood is at its least amount of width and will expand as it warms up around here. So, I guess the answer is to simply make the total length of the breadboard end whatever dimension is specified and at this time of year...make the table top field less of a width by the amount that the calculations tell me. Just divide the difference between both sides obviously. This, theoretically, will bring the table top out to meet the length of the breadboard ends when the summer humidity returns correct?

Frank - I was presented with a picture of what the friend wanted. Fortunately the design had the breadboard end designed into it and I have never done one, but have wanted to give one a shot for a while now and this was a good opportunity. The tabletop will be oriented with the breadboard ends on the 42" width of the table ends. The main field of the tabletop will be oriented with the grain of the planks running end to end.

John - Poplar fir the budget of the client...it's as plain as that. I going to look at the bright side and say if there is one good thing about poplar...it's that it mills beautifully and clean and crisp and that is one of the things that I like about poplar and since this whole issue with me surrounds a first attempt at breadboard ends and that requires lots of milling...I figure what better wood to have to use than poplar?

Kevin - Thanks for that link. I will go check it out right after I hit the send button to launch this one away. And yes, I do have a moisture meter and I also have had the pleasure of reading..or at least paging through Bruce Hoadley's book. Unfortunately, it was borrowed and I would have taken a while to read the entire book the way I would have wanted to and I didn't want to keep it that long. I assumed that I would get around to purchasing the book, but its been way longer than that. I can see that I should probably pick it up if not just for the excellent info and reference opportunities.

[Joe Adams]

Just make sure your friend understands the breadboard ends will not line up with the rest of the table for roughly half of each year. I always explain wood movement to clients who insist on a design with breadboard ends. Some are okay with it and some change the design to show endgrain.

[Michelle Rich]

Just make sure your friend understands the breadboard ends will not line up with the rest of the table for roughly half of each year. I always explain wood movement to clients who insist on a design with breadboard ends. Some are okay with it and some change the design to show endgrain.

I think Joe hits the nail on the head here..customers do not understand wood movement..so this info for them may very well nix the ends OR NOT..best to find out before you build.

[John K Jordan]

Is this Yellow Poplar (Liriodendron tulipifera) or one of the true poplars (Populus)?

I assume Yellow/Tulip Poplar since it is most likely to be used for furniture but it might be good to verify.

JKJ

[Jeff Bartley]

Fred,
In regards to material selection keep in mind the overall percent of the expense that the material represents. It's usually much lower than the labor, and in this case, if you remove the need to stain it you might be looking at even money choosing a harder species. Any ding in stained poplar will be very evident!
Whatever you choose keep in mind that using quarter sawn stock will minimize movement.
And I'll second the recommendation to check out the Bruce Hoadley book, it's awesome!

[Jim Becker]

Is this Yellow Poplar (Liriodendron tulipifera) or one of the true poplars (Populus)?

I assume Yellow/Tulip Poplar since it is most likely to be used for furniture but it might be good to verify.

JKJ

Yes, "Tulip Poplar" which is extremely common in our area...the whole back of my property consists of poplar (100'+ tall) and most of my wood rack is filled with it.
-----

Fred, I think you have a handle on the wood movement and agree that it will be a very good idea to explain to the client about wood movement and how the look at the breadboard ends might change slightly seasonally. That way, you'll avoid any misunderstanding later. That's kinda something that needs to be said about breadboard ends regardless of material...

I'm looking forward to seeing this project unfold!

[Fred Voorhees]

Yes, "Tulip Poplar" which is extremely common in our area...the whole back of my property consists of poplar (100'+ tall) and most of my wood rack is filled with it.
-----

Fred, I think you have a handle on the wood movement and agree that it will be a very good idea to explain to the client about wood movement and how the look at the breadboard ends might change slightly seasonally. That way, you'll avoid any misunderstanding later. That's kinda something that needs to be said about breadboard ends regardless of material...

I'm looking forward to seeing this project unfold!

Yeah Jim, I have made up some poplar samples with different shades of dark stain for the customer so that they can pick one and use it to choose the chairs for the table. At that time...I am again going to explain to them the issue of the wood movement and give them a last opportunity to either go with the breadboard end option or change over to just plain having end grain showing.

[John Vernier]

Just a suggestion - I have looked a lot at original work by Greene and Greene, and made some pieces in their style. They always made their breadboard ends a bit wider than the boards they were capping. That way, the look of the fit changes minimally as the top expands and contracts. If the overhang varies from, say, 1/8" to 1/4" each side over the seasons, that is a lot less noticeable than changing from an overhang to an underhang over the seasons. This looks best if you aren't running a through tongue and groove on your BB ends. I use a stopped tongue and groove and leave space for the tongue to expand inside the stopped groove on the BB end cap.

[Fred Voorhees]

Just a suggestion - I have looked a lot at original work by Greene and Greene, and made some pieces in their style. They always made their breadboard ends a bit wider than the boards they were capping. That way, the look of the fit changes minimally as the top expands and contracts. If the overhang varies from, say, 1/8" to 1/4" each side over the seasons, that is a lot less noticeable than changing from an overhang to an underhang over the seasons. This looks best if you aren't running a through tongue and groove on your BB ends. I use a stopped tongue and groove and leave space for the tongue to expand inside the stopped groove on the BB end cap.

John, it's coincidental that you should mention that because that was also something I considered doing. Purposely making an overhang that would remain an overhang year round....just sometimes less of an overhang and sometimes more. Certainly much less noticeable than sometimes underhang and sometimes overhang. And this is something else that I may run by them. I really want to do a breadboard end. This is one way that the entire situation could be remedied.