Width of boards for Panel Glue Up

[James "Cubby" Culbertson]

Hiya All, I'm getting ready to build a couple of hutches out of pine. I'm going to be having to glue up panels for the sides. Is there a general formula for how large your boards for glueing up can be? For instance, let's say the panel is to be 18" wide. Is it acceptable to use two 9" wide boards? 3-6" boards? etc.... Given the pine will show (ie. no painting), I want to minimize grain changes etc and gluing up two boards might be more beneficial for that. I've done a number of glue-ups like this before, but I always used plans that have told me how wide my boards should be for the panel. These do not. Thanks very much for any help!!!!! Cheers, cc

[Doug Miller]

No wider than the bed of your jointer.

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

[Swingman]

Take your jointer and planer width limitations into account.

Usually the boards fall within the width of your jointer, and the initial glueup of panels fall within the limitation of you planer.

IOW, if I was going to do it in my shop, I'd keep the board width less than six inches, and glue up two panels, each less than 13 inches wide, into a larger panel, slightly wider than your final width.

I find I get a much nicer and flatter panel glue up by doing it in two stages, instead of one ... this is just my preference and, as always, the proverbial YMMV applies.

[D K Woods]

Well in a perfect world you would be able to resaw a thicker board to get the boards for this panel, and then bookmatch them... That might not be an option, but it's always good for aesthetics!

david

[Preston Andreas]

In the industrial cabinet-making world, it is suggested not to join boards that are more than 3" wide for stability reasons. I don't go that small. Usually, the boards I join are around 4" to 7" if they are flat sawn boards. If the boards are quartersawn, their stability allows even wider boards. However, there is no hard and fast rule. If the boards have good figure, then you may want to use a wide board for the panel. You will have to live with the seasonal changes. Hopefully, they are well behaved boards so little movement is seen. Since you are limited by you jointer (unless you neander it), you may have to rip a wide board to less than jointer width, mill it and reglue. But remember, it is still considered one board since you haven't changed the grain direction. If you do use wide boards, try to use ones that have the grain oriented more or less transverse to the face (quartersawn).

Preston

[Trent©]

You need to have the sides ready for gluing...either with a good saw blade, a jointer, or a router, etc.

Whatever your preference. Whatever size your tools will accomodate...to get the sides ready for gluing.

Have you ruled out plywood?

You might also look into the Kreg jointer system instead of clamping. Not for everybody...but pretty slick.

Have a nice week...

Trent

Cat...the OTHER white meat!

[James "Cubby" Culbertson]

Thanks folks for the insight. As for jointer/planar width, I'm using handplanes to join the edges and smooth so there is really no limitation to the size. I'll take the consensus that somewhere between 3-5" is appropriate. I've had marked changes in boards given my extremes in humidity levels (New Mexico).

Cheers all! cc

[Brett A. Thomas]

cc,

I think the important thing to understand is, when you edge joint them and glue them together they effectively become one big board for lateral movement purposes. One 20" board is going to expand and contract across the grain just as much (or as little) as 5 4" boards glued to make one 20" panel. The trick is that you're a lot more likely to get warping and cupping out of a 20" board than from a glued up panel. Similarly, a 20" panel made from two 10" boards is more likely to end up not flat in some way than a 20" panel made from 20 1" boards.

In some designs, this doesn't matter, if there's something holding both ends so it can't twist. For example, a headboard is usually stuck in a very long mortise. Similarly, breadboard edges on a table prevent warping. So can floating panel construction.

When you consider how wide to make the boards, you also need to consider exactly how the boards will be restrained from warping. If there's no constraint - a non-breadboard-edge table, for example, you'll want narrower boards. If the wood is constrained from moving out of flat, you may be able to go with wider boards, which will look better.

Regardless of whether you go with narrow stock or wide to source your panel, you still need to remember to account for seasonal expansion and contraction across the whole panel width, however.

-BAT

[Gfretwell]

Is there somewhere that has typical expansion rates for various types of wood?

[Brett A. Thomas]

The "rule of thumb" is 1/8" for every foot of width. A big factor is the seasonal change of humidity in your area; another big one is difference between working humidity and finished humidity. If you make the furniture in an outdoor shop in August in Savannah, GA, and use it inside in the same place, you're probably looking at a 95% humidity environment where you worked it versus a 20% humidity environment it'll live in. As that humidity leaves the piece, you may end up with wood that is a significantly different size than it was when you made it.

I don't have info available on what species expand more than others, but I can tell you this:

Quartersawn is much better than flatsawn for all stability.

According to my _Woodworker's Guide to Wood_, these are the "Checking and Warping Tendencies in Hardwoods:"

Low: Alder Basswood Birch, paper Cherry Cottonwood Elm, white Poplar Willow

Medium: Apple Ash Birch, European or Yellow Elm, European or rock Hickory Holly Pear Sycamore, European Walnut

High: Boxwood Beech Chestnut Oak Sycamore, American

-BAT

[Gfretwell]

Thanks That was what I was looking for. What is the length delta?

I doubt anyone's house is that tight. I have a weksler running all the time and my humidity cruises in the low 60s with the AC on when the outside ambient is

85-99 (SW Fla) I have the cypress in the house now so it will be stabilized when I glue it up.

[George]

Not necessarily.

When you buy 4" lumber, you are generally buying the first board off the log. This is the one most affected by heart/sapwood differences in moisture while drying, and even when dry and planed, has a great degree of annual ring curvature relative to its width. It's the curvature that makes the difference in staying flat. If the board has little curvature across its width either because the growth rings are vertical or horizontal, it will stay flat. Of course, the horizontal one will still have a greater expansion coefficient.

Wide boards are only more expensive at the retail level. Until then a BF is a BF. Thicker stock, because of the different drying schedule, becomes more expensive at the wholesale level.

[Mark Ohlund]

There's little to no length change. Wood cells swell in thickness (across grain) rather than in length (with the grain) with moisture changes.

[James "Cubby" Culbertson]

I've got enough clamps to get by I think. Won't be able to glue everything up at once but that's ok.

I've now run into the Aesthetics issue. I'm working with knotty pine and need to make these panels from that. I've got 1x10 boards to work with. Where I'm having trouble is this. I need a 12" panel for instance. Ok, figure on cutting three boards around 4 1/4 wide or so. No problem. Cept I can't find a single board that will allow me to do this without cutting through a large knot. Obviously I don't want to be gluing this into a panel (prefer to have whole knots at least on the bulk of the panel). Is it acceptable to say go for 2

3" boards and a 7" board? If I mix and match my widths I think I can make it work. I'll prolly end up using more wood than necessary as it'll throw my cutting diagram all to hell but at $0.79/BF, I could justify buying a couple extra boards.

Any thoughts?

Thanks much. cc

[Mike Hide]

I would say glue up the minimum number of boards, the object being that the sides seem to be one single board . The less boards you use the less grain matching needs to be done .

Usually try and match edge grain to edge grain, the grain at the edges usually is straightest and therefore easiest to match.

-- mike hide

[Groggy]

James,

I have limited experience with panel construction to date, please bear that in mind when you consider my advice.

If you are concerned about having a 3", then 7", then 3" board - you are only a rip cut away from making them a lot closer. You could cut the 7" board and rejoint it to make it closer to the others. The different width would not be as obvious as the narrower pieces would "disappear" into the stile.

cheers,

Greg

[James "Cubby" Culbertson]

Thanks. Unfortunately, with knotty pine, I'm trying to avoid cutting the knots and then jointing. What I'd end up with is half a knot then pure grain and that wouldn't look so good. I think I'm just gonna try building the panels based on where the knots are and hope I don't get warping. I might install a couple of cleats on the back of the panels to help prevent it. Thanks for the help. Cheers, cc

[Brett A. Thomas]

Er, I've never actually worked with knotty pine, but aren't the knots supposed to be sound in that stuff?

Also, I don't think you ever said what these panels are for. :)

-BAT

[James Cubby Culbertson]

Actually, in the very first line of my original post, I said these panels were for a couple of hutches I'm building. Basically sides. The knots in the knotty pine are solid but I don't want to edge join a clear board with one that has a knot cut in half at the edge. Strength and such aside, it's an aesthetic thing. Looks cheap. So I'm trying to rip my boards without splitting knots so when I glue up, all I have is grain to grain at the joints with no half knots. Make sense? Thanks. cc

[Morgans]

Make

My personal rule with pine panels, is nothing over 4 1/2 inches. Get some more wood, so you can get rid of that one knot.

-- Jim in NC--