Lumber selection and grain prediction ??
I have a general question and a specific question here. The general question is: What type(s) of wood are appropriate for the chair design pictured below, for outdoor use (but not left out in bad weather). This practice chair was made from scrap cedar, and white oak is the other choice in mind:
The specific question is, how do I (or can I) predict the edge grain when viewing the surface grain of the board? Here are two pictures, in both of them the surface grain is pretty wide, but as you can see the edge grain is very, very different. The tight and straight edge grain works OK for the leg portion of the chair, but the widely-spaced stuff on the edge breaks under load:
forestgirl — you can take the girl out of the forest, but you can’t take the forest out of the girl 😉
Replies
FG, if the chairs are merely used for outdoor gatherings of relatively short duration, but stored indoors, the decay resistance of the species used is essentially insignificant. They are not being allowed to take on and maintain a moisture content in excess of 20%, where the fungi that cause decay are able to metabolize. Your higher priorities would be strength (or strength to weight ratio, since the weight of a portable chair has some significance), elasticity (the ability to absorb shock), wear resistance and perhaps even appearance.
Your photo with the "weak" label exhibits grain run-off. In other words, grain direction that is more perpendicular, as opposed to parallel, to the length of the board. Look at the edge grain of the "weak" example, where the annual rings run from face to face, versus the longitudinal direction of the annual rings in the comparison photo. In the weak example you are looking at an obiquely angled end grain on the edge, while in the other photo you are looking at exposed radial grain on the edge. There are some other subtle clues you could examine, but you almost never need to resort to them.
Edited 7/9/2003 8:42:57 PM ET by Jon Arno
Jon, if I were picking out lumber for the chairs, and could not see the edge grain (S2S), what clues would I look for? Sorry if I'm being dense, but I have lots of trouble with 3D stuff! I can look at the edge grain and see where it's strong and where it's weak with respect to the direction of force against it (human body), but can't figure out how to tell by looking at a planed surface what the edge grain might look like.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
FG: Unfortunately, it's almost impossible to guess at the configuration of the edge grain -- you have to see it to know for sure. There are a couple of hints, but nothing which is a sure predictor.
If the wood has been quartersawn, then the edge grain is more likely to be parallel to the face -- again, this is not a sure thing, just a hint. (Also note that quartersawn boards are inherently stronger than riftsawn.)
Next, check the end grain (assuming that you can see the ends). If the end grain is vertical (like fence pickets), then the edge grain is more likely to be parallel. (Vertical endgrain indicates quartersawn wood.)
If the species of wood in use is one that shows flecks (or curl or other indicators) when quartersawn, then that is a good indicator too. Note that white oak is not the only wood that looks different when quartersawn.
One more indicator, tho less reliable, is the presence or lack of "cathedrals" in the face grain. A cathedral is where the grain lines sort of run up the board, then turn and run back down. If the face grain has cathedrals, then the wood was probably flatsawn or riftsawn (both of which are weaker than quartersawn wood).
And finally, I'll say that there is another indicator of wood strength -- other than grain direction. The tightness of the grain lines is as important as the direction of the grain. If you want really strong wood, look for lots of grain lines per inch -- really tight grain means really strong wood. (But in the application in your picture, grain direction will be the bigger factor.)
Vast projects should not be founded on half vast ideas.
When I need straight grained wood I do one or both of the following.
Ask the lumberyard to edge saw one edge of the wood after telling them why it is important. I've never had them refuse me but I buy a lot at their yard.
I take a block plane whenever I am going to the yard that has either rough sawn or S2S lumber. I ask them if they mind if I "lightly" preview the edge wood. Generally, no problem.
I am not aware of any way of reliably predicting the edge grain unless it is sawn or planed.
I've got two sets of chairs similar to yours - one set out of pine(don't know the specie) and the other out of oak - the pine are more comfortable, altho there has been some crush where the seat slides into the back (I bought them from the neighbors when they moved, they were very large people) -
anyway, I grab the pine set first - 'softer' - lighter -
David, pine? Interesting. Tight grain?
I noticed some crush too, I suspect that's to be expected just from the way the two pieces fit together. I love this chair because of the way it knocks down and nests together for storage. Storage is always an issue here in the Northwest because the summer is so darned short.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
A year or so ago I rebuilt a set of four of these chairs. The slats were cedar and the curved pieces had been made of 5/4 PT SYP. The chairs had been indifferently painted and left in the weather (mostly hot and humid, rarely wet) for about 10 years.
The cedar had held up well, although with some fastener failure due to rust. The PT had fallen apart where it was in contact with the ground. No particular attention had been paid to grain direction, and they lasted a long time while being completely neglected.
I rebuilt them in the same materials. To test them I sat in them and had my four year old son jump all over me. They seemed fine, and I have not heard any complaints in the year they have been in use.
HTH,
Jon
OK, Jon, I give, what's PT SYP. Pressure treated something? Thanks for providing the thickness of the curved pieces. One of the reservations I had about the plan this chair was made from is that it specified 3/4" thick for the frame pieces, seems too thin, especially if using a wood other than oak or some similarly tight-grained dense wood.
Is the upper (head) part of your chair similar to this one? Do yours knock down? (These you simply pull the two parts away from each other and nest them together.)
Thanks for the input.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Pressure treated southern yellow pine. The nasty stuff, you have to clean and wax all your tools after you machine it, it's so wet. Also, because it's so wet it shrinks a lot. Really a lot.
The chairs were identical, as best I can recall, except that instead of a "missing" slat on the back rest, one of the upper slats was milled wider and had a notch cut out for a hand grip.
The slats were pinned, the load bearing pieces, where the two halves of the chair meet, were screwed. No glue anywhere. They were pretty rickety when I got them.
I like the design. Clean and minimalist. I'd go with a hardwood, just for the reason that it is such a minimalist design and you could make a showpiece out of it. I'd like to build that chair in jarrah, from Western Australia - it would finish beautifully, have way more than adequate strength, regardless of grain direction and spacing, but it WOULD weigh a ton. My .02. Ed
Ed, I'm thinking about making a set as a wedding present, would probably make those out of white oak. For my own use, I might go to something exotic, but for other folks, seems like something lighter and less expensive might be in order. Wonder how one of the "mahogany" woods we have these days would work. Any thoughts?
PS: I'm not real fond of that "missing slat" either. IMO, it makes the upper back of the chair not very comfortable. I thought maybe there was a reason, but couldn't find one after sitting in it. It also seems thatthe chair is rather height-sensitive with regard to comfort -- the match-up between the person and the top of the back has to be just right, unless a small pillow is added.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Edited 7/10/2003 11:14:03 AM ET by forestgirl
FG,
I think white oak will be frantastic. I think any kind of hardwood that you would normally use on a sailboat would be great. It will probably be the best wedding gift that they get. Please post pictures in the gallery, when done.
BTW, I once made some outdoor furniture out of red oak, despite every piece of advice I ever read telling me not to. My thoughts: "This oak is so pretty, I have to make two adirondack chairs out of it. Besides I will completely seal every pore of the wood. I will treat it like brightwork on a boat and refinish it every two months. I will make it work!" Needless to say, the wood eventually turned black and rotted in places. So when they say don't build outdoor furniture out of red oak, they mean it. Being the world's number one knucklehead, I had to find out the hard way. Enclosed is a pic of what they looked like when they looked good.
Oooh, they are (were?) very pretty. Sorry to hear all that hard work was for naught (except the learning experience, dontch love those?). Yep, I've been tempted, because I have quite a bit of red oak in stock, but I will resist the temptation!
PS: The one thing that kinda gives me pause about making those chairs as a wedding present -- the bride's father is an incredible woodworker (and knows it, LOL!) so dare I make something? Hmmmm, it's a toughie.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Edited 7/10/2003 12:38:15 PM ET by forestgirl
If you want to get a better understanding of grain and how it affects strength characteristics, you should probably become more familiar with softwood grading rules. You might try looking at the Western Wood Products Manufacturers Association (http://wwpa.org) to see if they have literature or grading standards available on line.
Once you get a little bit of knowledge about the actual grading rules and how these visual criteria correlate with board strength then the only thing you need is some application and lots of experience in looking at boards and boards and more boards.
Or, you could just put a tag on each chair that limits the load and absolves you from any law suits!
Hey there forestgirl-
Not to hijack your thread, but those are great chairs, and really look well suited for doing a production run, like a set of 6 or 8 or whatever. How comfortable are they: short conversation kind of comfy, or all-day-by-the-pool kind of comfy?
I don't suppose you've got a set of measurements around for that chair, or a link? How is that scissor joint put together? I'd appreciate it!
Thanks,
Kevin
not to hijack either, kevin - but here's a few picts of one of the pine units I have - maybe this will explain how they work - you see them around 're-inactments' of historical events where rules don't permit plastic and such - if they fit you, they are quite comfortable -
FG - maybe you can speculate on the species represented here - I'd think something like redwood would make a comfortable chair - -
David, thanks for posting those pictures. It's interesting to see different versions of the same basic design. No idea from me what the wood is though. Are there 3 screws in each slot? Wow.
I like the handle in the top, does it feel funny on your head, though, when you're sitting in the chair? I wonder if carrying is one of the purposes of the missing slat on the PW design.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
FG - It would cost a bundle, but I think teak unquestionably would be one of the best woods for your design. I would use an oil finish.
My second choice is a marine influence. Mahogany with a Spar varnish finish.
Two very different looks, depending on the use.
Oh, yes, teak would be wonderful. Oh, that price tag though.....ummmph.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
FG, sorry to be jumping back into your thread so late, but I've been out of town. A mile or so earlier you asked about other subtle clues for determining grain direction when you can see only one face of the board.
One of the other quick clues is to examine the surface luster from one end of the board (or surface) then go to the other end and examine it again. Because grain run off is a condition where the wood fibers are coming up to the surface at an obique angle, looking at the surface from the direction where the fibers are coming up toward you will reveal a dull (lusterless) surface. Looking at the board from the direction where the fibers are climbing up away from you will be more lustrous.
This difference in luster is especially apparent on the quartersawn surface of woods with interlocked grain, such as African mahogany and elm, because you get to see the difference in luster side-by-side in the alternating bands...that is, if you first want to look at an example of this difference in luster, just to develop an understanding of what you'd be looking for.
Other clues are best seen with the aid of a hand lens. Grain run off exposes the oval shaped lumens of the pores (oblique end grain) which is easy to spot with magnification.
Of course, if you are looking at the face of a board that has grain running off toward its edges, the pattern (direction) of the figure will be diagonal to the length of the board...but that is so obvious, it should be difficult to miss.
The important thing to remember is that virtually all sawn lumber has a certain amount of grain run off. You would have to split, or riv the wood to avoid all run off...So , the structural impact of run off is a matter of degree. With experience, you learn to spot signs of grain run off by the distorted figure of the wood; the arched, or "cathedral" pattern mentioned earlier in the thread is an important tip to look for that would at least cause you to then check other clues. It may not always indicate a run off that is structurally significant, since it can also be produced by a slight wave in the grain.
FG, the real skill you are seeking to develop here is to be able to look beyond the pattern of a wood's figure or grain and read what that pattern is revealing to you about the cellular anatomy of the wood. If you "tune" your mind to it, it's not that difficult a skill to master.
Hopefully you'll find these comments helpful from an old boatman who knows a lot about wood and weather.
The whole idea of outdoor chairs is a problem, mainly, I think, because of the fact that they get banged up a lot so that it's hard to keep a finish on them or any kind. When they get nicks and dings, then the wood starts absorbing water and the rest of the finish starts lifing off. Then the legs sit either on wet earth or damp decks. People always have good intentions about never leaving them out in the rain, but we know how that goes . . .
And,as with a boat, the seat with planks against a frame, mechanically fastened, creates a crevice to suck water in and trap it. Also, crevice corrosion will attack the fasterners at the interface of the two boards. Plus, stress and strain takes its toll, so there we have the reason why outdoor wood chairs fare so poorly unless exceptional care is given them, which it rarely is. Yet another problem is the exposed end grain on the feet which will suck up moisture like a sponge. I think I'd do a special epoxy lamination at the leg terminus to solve that problem.
If I were doing your project I'd choose a naturally rot resistant wood, use epoxy on joints rather than metal fasterners, and put no finish on it at all, especially not oils which mildew like crazy. Teak is the perfect wood for that, but there are also other good choices. True mahogany will also hold up nicely, as will sitka spruce. Luan is another good one but for the interlocking grain. I once did an outdoor table with luan that was still in good shape after 8 years in Florida. It had no finish at all. Sunlight weathered it to a beautiful silver.
PTSYP isn't a bad idea either. It's quality ranges from pure garbage (home depot, lowes) to very good. The stuff is only wet and hard to work because it has been mishandled and stored in weather, or you have a grade that is shipped "wet," which isn't sutable for anything but is widely sold to ignorant contractors and homeowners who don't know any better. Kiln dried PTSYP IS available. Last year, I made an arbor and trelis for my patio with no finish on it and its holding up nicely. Hasn't even changed color yet.
Thanks Boatman, that is very good information and I'll keep it all in mind. Have to tell you about one idea I had for those "tips" that contact the ground -- a silly idea, but just had to entertain it. You know that rubbery stuff you can dip tool handles in to get a comfort grip? Yep! You got it! Probably wouldn't work, but it was an instant-image sort of idea.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
I have a concrete patio. After a couple years of dragging patio furniture around on it, the chair legs got about an inche shorter!!! For wood legs, I cut a short tennon, build a little wood box (coffer dam) around it and then fill with epoxy which is abrasion resitant. When the epoxy is set, I mill off the coffer dam on router table. Thus I have a 1" deep plastic tip on the ends that no way is going to come off, nor does water creep up the end grain. Works good.
When doing outdoor stuff, you always gotta think about capillary effect and try to outsmart the laws of physics.
"...try to outsmart the laws of physics." Well, with a little help from you I might be able to pull that off! (The only class I reaallllllllly blew in college!)forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
The simple rule is that the grain direction should be perpendicular to the direction of greatest force. You can have grain running at compound angles and make a big deal of trying to figure it out. But you'll always be safest if you don't use a piece like the one you've shown.
For example, if you've got bent wood or curved grain, use that board to make a curved piece who's shape follows the grain.Boat builders of old always made curved frames from curved wood. Yep, what we call reaction wood, only you let it react in your favor instead of working against you (every evil hath it's good or something like that). Thus a bent tree isn't a bad thing for it has as many uses as the straight tree. You can still see boats built this way around the world.
Now, when you get to analysing the forces that are applied to your chair, THAT gets a little complicated. Expecially when you have to design for some 300 lb. gorilla tilting back on it so he doesn't get gored with a broken shaft of wood when the thing collapses. Ooops! If you have doubts about it, it's probably wrong.
Hi Kevin, I got the plan out of this summer's Popular Woodworking Outdoor Furniture issue. They might have it at their website http://www.popwood.com
According to the article, this design is more than a few centuries old (Africans to Romans to Europe to Ireland to U.S.). Seems portable chairs were useful to all those armies.
Production? Yes, I was thinkin' that myself. The actual cutting isn't too big a deal, especially using a templte for the curved pieces. The assembly was pretty time-consuming on that first one I made, though. The first two slats (below and above the seat, on the back-rest part) have to be perfect, with everything parallel and exactly the same distances away from the ends. Adding to the time was the fact that I did drill pilot holes, even though I was using self-tapping "new-age" woodscrews.
I also used glue, per instructions from the plans. Wasn't originally going to do this, but figured it would help keep the pieces from creating movement that would eventually loosen the screws. Is there another way to approach this and still ensure long life?
The X-shape just knocks apart. You can see, hopefully, that the seat supports fit inside the back supports -- they simply slide in and are braced by the 2 slats immediate above and below the seat.
Oooops, got customers, gotta go.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
["customers" were lookie-loos] As to comfort, the seat-to-back angle is very comfortable for me. This particular version of this chair is a bit awkward in the neck/head area because, I think, of the strong curve toward the body. A pillow (small, almost tubular shape) resolves that though.
Don't know if it would be all day comfortable. With the addition of a footrest, I'd say probably Yes.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
If you get the American Woodworker magazine, I believe they have a brief article in this months issue on the topic of interpreting grain. I was only able to glance at it when I was home for lunch today.
Thanks, JD, I do subsx to AW, must have forgotten about that one. Will find it and read.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Hey Jamie I made several of those about 10 years ago gave them for Christmas Gifts. They are all still around in use. One pair I gave to a friend to use at their place on Galveston Bay. The only time they have been taken in is when a hurricane threatens, today was a good example. Claudette came through this morning not much storm here. I made a porch swing about a year later for the bay place and it still is in excellent shape. These are on a deck exposed to the elements all year no covering.
I made mine out of pressure treated pine, 1" slats predrilled holes, rounded over the top edges with my router. The legs I cut out of a 2" X 8" on my bandsaw rounded those edges also. I didn't use any finish on any of them and they have held up fine. The only mistake I made my top slat I cut out of a 1" X 6" I did a curvy type thing and a couple of them have got busted off. I give a lifetime guarantee on my efforts so I have replaced those as needed.
Gods Peace
les
Hi Les, thanks for the post. I don't know if you can answer just looking at the pic above, but did your chairs curve as much at the top, by the sitter's head? That's the part that seems it needs adjusting to me.
You ay yours were made about 10 years ago...what did they use in the pressure-treating process on the pine? Everyone's so wiggy these days about PT lumber and arsenic.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Ten years ago it was surely arsenic. Today there are several non arsenic types, one copper based which leaves the wood nice and green colored (and ugly) and another type I don't know what it is but from which I made an arbor, benches and flower pot stands. It is very light gray-green and, I think, fairly attractive. Weathers very well.
SYP is one of the most poorly handled woods in existence.Whether it's PT or not, most suppliers treat it like garbage and much of it is. However, good suppliers will carry higher grades that are suitable for projects like ours where the wood is kiln dried after treating and was not stored out in the rain. Those are the factors to look for when buying this stuff. If the suppliers stock looks mishandled, stay away from it and look elsewhere.
Also SYP is highly variable as to strength, but is a very strong wood even when stacked against hardwoods. But fast growing trees with widely space rings can be weak, so when selecting look for tight rings on the ends as the sap wood can be very soft. Fires are known to strengthen SYP considerably, Trees cut from natural stands are much strong than those from plantations. Most wide planks come from natural stands, while plantation stuff ends up as studs. Avoid knots like the plague and watch out for reaction wood.
Being a coonass from down New Orleans way, I always think of Cypress as a wood of choice for outdoor use. If you can find a source for it, it is weather proof and mellows nicely with age. The older wood, like sinker cypress is pretty expensive, but the mellow yellow color is so fine. also the older wood is grainier and looks much better and holds up better to insect and rot deterioration.
No wood lasts forever down here, but cypress comes close.
Squeezer, I've never worked with cypress, but really want to. Since I have white oak in stock already, I'll probably use it first. Then I'll try cypress (we have a supplier in Seattle).
"Coonass"???? I've owned a couple of coon hounds, but never encountered a coonass before!!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Well Forestgirl, you will be in for a treat once you find one. You gotta look way down in de swamp to find a good one....kinda lak lookin' fo de cypress tree.
Good luck on your project....cypress rules for outside. gets a nice gray patina like cedar does, if you don't finish it. Cuts easy...mills easy.
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