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#1
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How to repair warped table top?
Planks (a light wood?) that make up the top of a small table are weather
warped. "Cupped" upward. This isn't meant to be a centerpiece of the home, but it would be nice to make it presentable again. What's the usual repair recommended for such a condition? Tools available: the usual drills and hand tools; table saw; router; belt sander; palm sander; paint gun and compressor. Suggestions welcome. Thanks. |
#2
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How to repair warped table top?
Paul Conners wrote:
Planks (a light wood?) that make up the top of a small table are weather warped. "Cupped" upward. This isn't meant to be a centerpiece of the home, but it would be nice to make it presentable again. What's the usual repair recommended for such a condition? Replace the boards. And put them so if they cup they will cup with the center up. Fasten in the center and keep painted/varnished. _____________ Tools available: the usual drills and hand tools; table saw; router; belt sander; palm sander; paint gun and compressor. Suggestions welcome. Well, you could .... a) plane down the boards to make them flat on the surface b) if thin/narrow enough, bend them down and fasten c) if not thin enough, remove and rip one or more kerfs on underside, put glue in kerfs, bend flat. -- dadiOH ____________________________ dadiOH's dandies v3.06... ....a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at http://mysite.verizon.net/xico |
#3
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How to repair warped table top?
On Feb 17, 12:55*am, Paul Conners wrote:
Planks (a light wood?) that make up the top of a small table are weather warped. "Cupped" upward. This isn't meant to be a centerpiece of the home, but it would be nice to make it presentable again. What's the usual repair recommended for such a condition? Tools available: the usual drills and hand tools; table saw; router; belt sander; palm sander; paint gun and compressor. Suggestions welcome. Thanks. Depends on the amount of cup and the edges of the table. My wife inherited an attractive elm claw foot from her mom. It had a similar problem and one of the glue joints had failed too. I removed it from the legs, removed the edge trim, sawed through the failed glue joint and glued it back together. Before gluing I took a thin pass through a thickness planer to level the top out again. Came out looking good. If you don't have a planer, search around for a friend or school that does. RonB |
#4
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How to repair warped table top?
On Feb 16, 10:55*pm, Paul Conners wrote:
Planks (a light wood?) that make up the top of a small table are weather warped. "Cupped" upward. This isn't meant to be a centerpiece of the home, but it would be nice to make it presentable again. What's the usual repair recommended for such a condition? Tools available: the usual drills and hand tools; table saw; router; belt sander; palm sander; paint gun and compressor. Suggestions welcome. Thanks. Very hard to say how I would address it without seeing a picture. Can you post a pic somwhere? Be careful if you plan to try and address it with a planer because depending on the defect the planer rollers can sometimes just hold it flat while it planes it, then aftewards it rools right back into it's curl and you have a nice flat but curled surface still. |
#5
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How to repair warped table top?
On 2/17/2012 12:55 AM, Paul Conners wrote:
Planks (a light wood?) that make up the top of a small table are weather warped. "Cupped" upward. This isn't meant to be a centerpiece of the home, but it would be nice to make it presentable again. What's the usual repair recommended for such a condition? Tools available: the usual drills and hand tools; table saw; router; belt sander; palm sander; paint gun and compressor. Suggestions welcome. Thanks. I like to start this type of conversation by saying, "you're not happy with it the way it is now, are you?" or "it doesn't work now, does it?". I guess we can't hurt too bad. I would remove the top. On a nice spring day I would lay it on the grass with the humped side up. Let it sit there a day preferably with some sunshine. The piece has probably gotten wet at some point and the top dried quicker and pulled the warp. I am suggesting you try to equalize the moisture throughout the piece. I'm thinking you will see some substantial improvement after a day of absorbing ground moisture on the shrunken side and air/sun drying on the top side. I would them give it lots of weight on a flat table surface, not on the concrete patio or garage floor. After a week, see what you have. -- ___________________________________ Keep the whole world singing . . . Dan G remove the seven |
#6
Posted to alt.woodworking,free.uk.woodworking,rec.woodworking
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How to repair warped table top?
I would remove the top. On a nice spring day I would lay it on the
grass with the humped side up. Let it sit there a day preferably with some sunshine. The piece has probably gotten wet at some point and the top dried quicker and pulled the warp. I am suggesting you try to equalize the moisture throughout the piece. I'm thinking you will see some substantial improvement after a day of absorbing ground moisture on the shrunken side and air/sun drying on the top side. I would them give it lots of weight on a flat table surface, not on the concrete patio or garage floor. After a week, see what you have. [Dan G] I like your suggestions. The lawn and sunshine are readily available. But the only large flat surface is the garage floor. And weight? Hmm... 2 front wheels of the Toyota come to mind... Thanks. |
#7
Posted to alt.woodworking,free.uk.woodworking,rec.woodworking
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How to repair warped table top?
In ,
Paul Conners typed: Planks (a light wood?) that make up the top of a small table are weather warped. "Cupped" upward. This isn't meant to be a centerpiece of the home, but it would be nice to make it presentable again. What's the usual repair recommended for such a condition? Tools available: the usual drills and hand tools; table saw; router; belt sander; palm sander; paint gun and compressor. Suggestions welcome. Thanks. Find someone with a planer and have them smooth it out for you into a flat surface. |
#8
Posted to alt.woodworking,free.uk.woodworking,rec.woodworking
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How to repair warped table top?
On 2/18/2012 12:42 PM, Paul Conners wrote:
I would remove the top. On a nice spring day I would lay it on the grass with the humped side up. Let it sit there a day preferably with some sunshine. The piece has probably gotten wet at some point and the top dried quicker and pulled the warp. I am suggesting you try to equalize the moisture throughout the piece. I'm thinking you will see some substantial improvement after a day of absorbing ground moisture on the shrunken side and air/sun drying on the top side. I would them give it lots of weight on a flat table surface, not on the concrete patio or garage floor. After a week, see what you have. [Dan G] I like your suggestions. The lawn and sunshine are readily available. But the only large flat surface is the garage floor. And weight? Hmm... 2 front wheels of the Toyota come to mind... I thought his suggestion ingenious as well. How about that Toyota, an appropriately-sized sheet of 3/4" plywood (make a sandwich of your "moistened" top) and a piece of 2x10 as a caul? |
#9
Posted to alt.woodworking,free.uk.woodworking,rec.woodworking
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How to repair warped table top?
Paul Conners wrote:
Planks (a light wood?) that make up the top of a small table are weather warped. "Cupped" upward. This isn't meant to be a centerpiece of the home, but it would be nice to make it presentable again. What's the usual repair recommended for such a condition? Tools available: the usual drills and hand tools; table saw; router; belt sander; palm sander; paint gun and compressor. Suggestions welcome. Thanks. Just a note - cupping takes place towards the moisture not away from it. |
#10
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How to repair warped table top?
Just a note - cupping takes place towards the moisture not away from it.
Just to clarify: the concave side is moist, and the convex side is dry? |
#11
Posted to alt.woodworking,free.uk.woodworking,rec.woodworking
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How to repair warped table top?
Paul Conners wrote:
Just a note - cupping takes place towards the moisture not away from it. Just to clarify: the concave side is moist, and the convex side is dry? Yes. Table top looks like a U (not as drastic I hope). Top got wet while the underside remained drier. When it dried out the compressed fibers (caused be the dry side restricting even swelling of the wet side) distort it... according to the books As mentioned, a possible sollution is to wet it all down lay it on stickers and put weight on it to dry. The "proper" method for an antique is to router out the underside and replace with hardboard. That leaves the original top surface while providing a flat base for it. Something I probably would not have the nerve to do. Mike |
#12
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How to repair warped table top?
On 2/22/2012 12:05 AM, Michael Joel wrote:
Paul Conners wrote: Just a note - cupping takes place towards the moisture not away from it. Just to clarify: the concave side is moist, and the convex side is dry? Yes. Not necessarily ... and AAMOF, and depending upon the grain and the way the wood was cut off the tree, it more likely to be just the opposite of what you stated ... the concave side being the dry side, and the convex the moist. There are indeed some exception with certain grain patterns due to the way the wood was cut from the log (plain sawn, rift sawn, etc.), or if laminated, but mostly wood cups and checks parallel to the grain and to the drier side. Excellent example is the cupping of hardwood floors, which "cup" (concave side up) when wet from the underneath ... dry on the top, wet on bottom ... one of the main reasons why a moisture barrier is always used _beneath_ a hardwood floor. Another hole in your balloon ... leaving a board to dry out in the sun, The concave side is drier from exposure to the sun and heat, and, once again, the board generally cups toward the dry side. Try this by laying a board on wet grass before the morning sun hits on sunny day, check it out by noon. Here is indeed, "according to the books": http://www.fpl.fs.fed.us/documnts/fp...chapter_16.pdf 16-6: quote Wood warmed by the sun experiences a virtual RH far below the ambient RH. The surface dries faster than the rest of the lumber. This is why cupping and checking often occur on decking boards; the top surface is much drier than the rest of the board. Shrinkage of the top surface commensurate with this dryness causes cupping and checking parallel to the grain /quote -- www.eWoodShop.com Last update: 4/15/2010 KarlCaillouet@ (the obvious) http://gplus.to/eWoodShop |
#13
Posted to alt.woodworking,free.uk.woodworking,rec.woodworking
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How to repair warped table top?
As mentioned, a possible sollution is to wet it all down lay it on
stickers and put weight on it to dry. ... Mike What are "stickers"? |
#14
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How to repair warped table top?
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#15
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How to repair warped table top?
On 2/22/2012 11:58 AM, Paul Conners wrote:
.... What are "stickers"? goatheads, sandburs, wavy thistle, ... Sorry, couldn't help it. -- |
#16
Posted to rec.woodworking
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How to repair warped table top?
Swingman wrote:
On 2/22/2012 12:05 AM, Michael Joel wrote: Paul Conners wrote: Just a note - cupping takes place towards the moisture not away from it. Just to clarify: the concave side is moist, and the convex side is dry? Yes. Not necessarily ... and AAMOF, and depending upon the grain and the way the wood was cut off the tree, it more likely to be just the opposite of what you stated ... the concave side being the dry side, and the convex the moist. There are indeed some exception with certain grain patterns due to the way the wood was cut from the log (plain sawn, rift sawn, etc.), or if laminated, but mostly wood cups and checks parallel to the grain and to the drier side. Excellent example is the cupping of hardwood floors, which "cup" (concave side up) when wet from the underneath ... dry on the top, wet on bottom ... one of the main reasons why a moisture barrier is always used _beneath_ a hardwood floor. Another hole in your balloon ... leaving a board to dry out in the sun, The concave side is drier from exposure to the sun and heat, and, once again, the board generally cups toward the dry side. Try this by laying a board on wet grass before the morning sun hits on sunny day, check it out by noon. Here is indeed, "according to the books": http://www.fpl.fs.fed.us/documnts/fp...chapter_16.pdf 16-6: quote Wood warmed by the sun experiences a virtual RH far below the ambient RH. The surface dries faster than the rest of the lumber. This is why cupping and checking often occur on decking boards; the top surface is much drier than the rest of the board. Shrinkage of the top surface commensurate with this dryness causes cupping and checking parallel to the grain /quote Sorry but I believe what I said to still be right. While grain of course will have effects the cupping will take place towards the moist side (or away from the compression pressure might also be a way to say it). Take a look at porches or decks, do you seen any cupped down? Fave you ever found a table top that cupped down? Your wood floor - is it cupping because it is moist underneath or because of the mopping and drying taking place above? as for the board on the lawn - don't know, would have to try it. Your quote - Is it indeed the sun causing the surface to dry faster or is it in fact that the problem is not visual until the surface dries? I will explain it as one of the books due (please recall I said this was according to the books - not neccessarily the truth - I believe much of the things "known" are not the truth of what is happening, but only what we as humans can guess at/or comprehend with our limited knowledge). Wood cells normally want to swell and then shrink back to their normal shape and size. When something restricts this the swelling continues on uncompressed sides (i.e. the bottom of the board, or anywhere else it is not wet/or drier). This forces the cells into more of an oval shape instead of their original shape. When they shrink from drying this shape is not shanged so the compressed sides of the cell (we will call it the width) ends up smaller than it used to be. As this is repeated we end up with cupping/warping/checks/etc.. I can never recall seeing a board that was cupped in any direction except on the side effected by changes in moisture. Mike |
#17
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How to repair warped table top?
Google is your friend...
Sticker A sticker is a type of a piece of paper or plastic, adhesive, sticky on one side, and usually with a design on the other. Stickers, Bumper Stickers - Sticker Giant Stickers made easy. 26,000 bumper sticker designs in stock. Custom sticker Stickers - Shop for a new Custom Stickers Political stickers, art stickers, funny stickers and millions more! Highest Stickers Galore Stickers Galore offers an incredibly large selection of stickers for \ 123stickers.com - Custom vinyl stickers | Custom Banners ... Custom Vinyl Stickers | Custom T-shirts | Custom Banners. Low minimum custom Then I tried "sticker wood" and got this and the like: http://www.ebay.com/sch/items/?_nkw=...w=&_mPrRngCbx= 1&_udlo=&_udhi=&_sop=12&_fpos=&_fspt=1&_sadis=&LH_ CAds= There comes a point where the flaming of "Don't you use Google?" is worth it... |
#18
Posted to alt.woodworking,free.uk.woodworking,rec.woodworking
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How to repair warped table top?
Paul Conners wrote:
As mentioned, a possible sollution is to wet it all down lay it on stickers and put weight on it to dry. ... Mike What are "stickers"? Sticks of wood (lumber). Usually they are used in stacked lumber to keep the wood separated for air flow - and flat. I did not mention that you would want a flat surface under the stickers. Mike |
#19
Posted to rec.woodworking
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How to repair warped table top?
On 2/22/2012 1:09 PM, Michael Joel wrote:
Swingman wrote: On 2/22/2012 12:05 AM, Michael Joel wrote: Paul Conners wrote: Just a note - cupping takes place towards the moisture not away from it. Just to clarify: the concave side is moist, and the convex side is dry? Yes. Not necessarily ... and AAMOF, and depending upon the grain and the way the wood was cut off the tree, it more likely to be just the opposite of what you stated ... the concave side being the dry side, and the convex the moist. There are indeed some exception with certain grain patterns due to the way the wood was cut from the log (plain sawn, rift sawn, etc.), or if laminated, but mostly wood cups and checks parallel to the grain and to the drier side. Excellent example is the cupping of hardwood floors, which "cup" (concave side up) when wet from the underneath ... dry on the top, wet on bottom ... one of the main reasons why a moisture barrier is always used _beneath_ a hardwood floor. Another hole in your balloon ... leaving a board to dry out in the sun, The concave side is drier from exposure to the sun and heat, and, once again, the board generally cups toward the dry side. Try this by laying a board on wet grass before the morning sun hits on sunny day, check it out by noon. Here is indeed, "according to the books": http://www.fpl.fs.fed.us/documnts/fp...chapter_16.pdf quote Wood warmed by the sun experiences a virtual RH far below the ambient RH. The surface dries faster than the rest of the lumber. This is why cupping and checking often occur on decking boards; the top surface is much drier than the rest of the board. Shrinkage of the top surface commensurate with this dryness causes cupping and checking parallel to the grain /quote Sorry but I believe what I said to still be right. Did you bother to even read the supporting evidence I provided disproving your unequivocal contention, first above? I will explain it as one of the books due (please recall I said this was according to the books - not neccessarily the truth It is indeed "not necessarily the truth", as I clearly outlined above, complete with a cite as to the an explanation for why your statement is not necessarily the case. By all means, offer a cite that supports your contention to the contrary. I believe much of the things "known" are not the truth of what is happening, but only what we as humans can guess at/or comprehend with our limited knowledge). Yes, and as a result, that attitude arguably insures that your knowledge in this regard will remain limited. Wood cells normally want to swell and then shrink back to their normal shape and size. When something restricts this the swelling continues on uncompressed sides (i.e. the bottom of the board, or anywhere else it is not wet/or drier). This forces the cells into more of an oval shape instead of their original shape. When they shrink from drying this shape is not shanged so the compressed sides of the cell (we will call it the width) ends up smaller than it used to be. As this is repeated we end up with cupping/warping/checks/etc.. The above is either so poorly worded as to be useless in defining your contention, or the result of a total misunderstanding of the effects of moisture and humidity on the dimensional instability of wood. It's really impossible to tell which? I can never recall seeing a board that was cupped in any direction except on the side effected by changes in moisture. Again, too loosely worded to be of much use in defining the problem ... and your admission that you have "never recalled" seeing that, is certainly no proof of your argument. Yes, it is indeed this _differential_ in moisture content between opposite faces that causes the phenomenon of cupping, but not necessarily for the reason you unequivocally stated first above. Simply put, cupping is most often the result of the opposite (convex) side being moist, and the cupped (concave) side being drier ... the exact opposite of your unequivocal statement. IOW, your understanding is mostly backwards of the actual effect of moisture on wood, with the exceptions I noted above. You will certainly want to do your homework, and provide some supporting evidence to the contrary, if you want to continue a reasonable discussion of the issue. -- www.eWoodShop.com Last update: 4/15/2010 KarlCaillouet@ (the obvious) http://gplus.to/eWoodShop |
#20
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How to repair warped table top?
Swingman wrote:
On 2/22/2012 12:05 AM, Michael Joel wrote: Paul Conners wrote: SNIP Just 2 mor cents... Grain of course plays a part is how the reaction takes place, but as you said "but mostly wood cups and checks parallel to the grain and to the drier side". As my previous post metnions - never seen a floor/table/deck cup down. But I don't want to argue it. As said - I am simply repeating it from information I have read. I doubt anyone knows for sure the real reasons for it all. Mike |
#21
Posted to rec.woodworking
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How to repair warped table top?
Swingman wrote:
On 2/22/2012 1:09 PM, Michael Joel wrote: Swingman wrote: On 2/22/2012 12:05 AM, Michael Joel wrote: Paul Conners wrote: Just a note - cupping takes place towards the moisture not away from it. Just to clarify: the concave side is moist, and the convex side is dry? Yes. Not necessarily ... and AAMOF, and depending upon the grain and the way the wood was cut off the tree, it more likely to be just the opposite of what you stated ... the concave side being the dry side, and the convex the moist. There are indeed some exception with certain grain patterns due to the way the wood was cut from the log (plain sawn, rift sawn, etc.), or if laminated, but mostly wood cups and checks parallel to the grain and to the drier side. Excellent example is the cupping of hardwood floors, which "cup" (concave side up) when wet from the underneath ... dry on the top, wet on bottom ... one of the main reasons why a moisture barrier is always used _beneath_ a hardwood floor. Another hole in your balloon ... leaving a board to dry out in the sun, The concave side is drier from exposure to the sun and heat, and, once again, the board generally cups toward the dry side. Try this by laying a board on wet grass before the morning sun hits on sunny day, check it out by noon. Here is indeed, "according to the books": http://www.fpl.fs.fed.us/documnts/fp...chapter_16.pdf quote Wood warmed by the sun experiences a virtual RH far below the ambient RH. The surface dries faster than the rest of the lumber. This is why cupping and checking often occur on decking boards; the top surface is much drier than the rest of the board. Shrinkage of the top surface commensurate with this dryness causes cupping and checking parallel to the grain /quote Sorry but I believe what I said to still be right. Did you bother to even read the supporting evidence I provided disproving your unequivocal contention, first above? I will explain it as one of the books due (please recall I said this was according to the books - not neccessarily the truth It is indeed "not necessarily the truth", as I clearly outlined above, complete with a cite as to the an explanation for why your statement is not necessarily the case. By all means, offer a cite that supports your contention to the contrary. I believe much of the things "known" are not the truth of what is happening, but only what we as humans can guess at/or comprehend with our limited knowledge). Yes, and as a result, that attitude arguably insures that your knowledge in this regard will remain limited. Wood cells normally want to swell and then shrink back to their normal shape and size. When something restricts this the swelling continues on uncompressed sides (i.e. the bottom of the board, or anywhere else it is not wet/or drier). This forces the cells into more of an oval shape instead of their original shape. When they shrink from drying this shape is not shanged so the compressed sides of the cell (we will call it the width) ends up smaller than it used to be. As this is repeated we end up with cupping/warping/checks/etc.. The above is either so poorly worded as to be useless in defining your contention, or the result of a total misunderstanding of the effects of moisture and humidity on the dimensional instability of wood. It's really impossible to tell which? I can never recall seeing a board that was cupped in any direction except on the side effected by changes in moisture. Again, too loosely worded to be of much use in defining the problem ... and your admission that you have "never recalled" seeing that, is certainly no proof of your argument. Yes, it is indeed this _differential_ in moisture content between opposite faces that causes the phenomenon of cupping, but not necessarily for the reason you unequivocally stated first above. Simply put, cupping is most often the result of the opposite (convex) side being moist, and the cupped (concave) side being drier ... the exact opposite of your unequivocal statement. IOW, your understanding is mostly backwards of the actual effect of moisture on wood, with the exceptions I noted above. You will certainly want to do your homework, and provide some supporting evidence to the contrary, if you want to continue a reasonable discussion of the issue. Ok. Whatever you would like to make it. I have no need to argue. I think my sentences were clear enough. You also call into question whether or not I even undestand moisture - and that I will not be able to learn (if I don't). I do believe for some reason you feel offended and seem to have a chip - but that is fine too. You have decided what you will take for the answer - nothing I say or do will change it. Mike |
#22
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How to repair warped table top?
On 2/22/2012 2:11 PM, Michael Joel wrote:
Swingman wrote: On 2/22/2012 12:05 AM, Michael Joel wrote: Paul Conners wrote: SNIP Just 2 mor cents... Grain of course plays a part is how the reaction takes place, but as you said "but mostly wood cups and checks parallel to the grain and to the drier side". As my previous post metnions - never seen a floor/table/deck cup down. But I don't want to argue it. As said - I am simply repeating it from information I have read. I doubt anyone knows for sure the real reasons for it all. You don't want to argue because you were mistaken, charitably, either in your wording, or your understanding. And you are very mistaken in your contention that you "doubt anyone knows for sure" ... a first semester, college level, Botany 101 class would prove to you that this is well understood, and well documented with empirical evidence. For your future benefit, and so this ends on an instructive note, you will certainly want to explore the definitive work on the matter: http://www.amazon.com/UNDERSTANDING-.../dp/B000UQH160 Every woodworker can learn something from reading Hoadley, guaranteed. -- www.eWoodShop.com Last update: 4/15/2010 KarlCaillouet@ (the obvious) http://gplus.to/eWoodShop |
#23
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How to repair warped table top?
On 2/22/2012 2:19 PM, Michael Joel wrote:
Swingman wrote: moisture on wood, with the exceptions I noted above. You will certainly want to do your homework, and provide some supporting evidence to the contrary, if you want to continue a reasonable discussion of the issue. Ok. Whatever you would like to make it. I have no need to argue. I think my sentences were clear enough. You also call into question whether or not I even undestand moisture - and that I will not be able to learn (if I don't). I do believe for some reason you feel offended and seem to have a chip - but that is fine too. You have decided what you will take for the answer - nothing I say or do will change it. To the contrary, and unlike you ... I will certainly read any supporting evidence you have to support your position. -- www.eWoodShop.com Last update: 4/15/2010 KarlCaillouet@ (the obvious) http://gplus.to/eWoodShop |
#24
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How to repair warped table top?
Swingman wrote:
You don't want to argue because you were mistaken, charitably, either in your wording, or your understanding. And you are very mistaken in your contention that you "doubt anyone knows for sure" ... a first semester, college level, Botany 101 class would prove to you that this is well understood, and well documented with empirical evidence. For your future benefit, and so this ends on an instructive note, you will certainly want to explore the definitive work on the matter: http://www.amazon.com/UNDERSTANDING-.../dp/B000UQH160 Every woodworker can learn something from reading Hoadley, guaranteed. See - that is why I get pulled back in. Because the logic is so illogical. If I said I don't believe they really know what is happening - you say take a "first semester, college level, Botany 101 class would prove" - The only thing it would prove is they believe it. Very circular thinking (as the "scientists" would say). That will be the last think I desire to say on the subject to you. You may continue to deride me if you like. Mike |
#25
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How to repair warped table top?
On 2/22/2012 2:28 PM, Michael Joel wrote:
Swingman wrote: That will be the last think I desire to say on the subject to you. You may continue to deride me if you like. You are wrong again ... it is not you being derided, It is you showing up here, making a statement that is misleading, and taking exception to being corrected (and very nicely and politely so, if you read my first post) What we don't particularly care for here is misleading information, so pardon me if I don't feel sorry for your above whining as somehow being a "victim". -- www.eWoodShop.com Last update: 4/15/2010 KarlCaillouet@ (the obvious) http://gplus.to/eWoodShop |
#26
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How to repair warped table top?
Sticks of wood (lumber). Usually they are used in stacked lumber to keep
the wood separated for air flow - and flat. I did not mention that you would want a flat surface under the stickers. Mike Thank you Mike. Three or four 2in x 2in sticks for a 36in x 48in table top? It will be placed on a concrete slab apron in front of the garage. No cracks or obvious defects in the slab. Thanks. |
#27
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How to repair warped table top?
On 2/22/2012 2:28 PM, Michael Joel wrote:
Swingman wrote: You don't want to argue because you were mistaken, charitably, either in your wording, or your understanding. And you are very mistaken in your contention that you "doubt anyone knows for sure" ... a first semester, college level, Botany 101 class would prove to you that this is well understood, and well documented with empirical evidence. For your future benefit, and so this ends on an instructive note, you will certainly want to explore the definitive work on the matter: http://www.amazon.com/UNDERSTANDING-.../dp/B000UQH160 Every woodworker can learn something from reading Hoadley, guaranteed. See - that is why I get pulled back in. Because the logic is so illogical. If I said I don't believe they really know what is happening - you say take a "first semester, college level, Botany 101 class would prove" - The only thing it would prove is they believe it. Very circular thinking (as the "scientists" would say). .... Well, that's self-serving to the max. You might as well say that the physicists on believe Newton's Principles; after all, it's "only" a theory. I suggest you do read Hoadley (or any of several references from the US Forest Products Lab, these can be downloaded at no cost); specifically Chap 4, "Wood and Water". The short story is---wood shrinks as it dries and it does so non-uniformly. The tangential/radial shrinkage ratio from green to oven-dry has been measured for some hundreds of species and averages about 2 (roughly an average of 8%/4% T/R) but shows a significant variation between species of from just barely above 1:1 to highs approaching 3:1. The higher the ratio the more the particular would will distort as it is dried as the relative shrinkage in the two directions competes at a different rate. The difference between tangential and radial shrinkage isn't random nor magic; it's caused by the anatomical structure, principally the effect of wood rays whose lengthwise axes are oriented radially outward. Species w/ more predominant rays are more stable. Over the range of moisture content shrinkage is roughly proportional to moisture loss. This doesn't matter too much as raw lumber is dried; the roughsawn stock is oversize to begin with and if dried uniformly will be stable after it is milled given a uniform environment. This is why it is so important to finish both sides of a furniture panel, say--if one side is finished and the other not, differential moisture absorption is highly likely to cause movement. Cupping after the fact is owing to one of two causes--either the piece wasn't at equilibrium to begin with and dried after milling with the resultant change in dimension as determined by the species' particular T/R ratio and the percentage change in moisture. The second is that the piece has subsequently absorbed moisture and therefore grown. The relative amount in the direction is also dependent on T/R and how uniform (or un-uniform) the moisture absorption is. Cupping in flatsawn boards results in concavity away from the pith, the result of greater tangential than radial shrinkage. The magnitude is greater as the location of the board from the original trunk is closer to the pith on a surface. This face is completely radial while the opposite is tangential in the portion across from the location of the pith and will therefore shrink at twice the rate. Woodworkers tend to say the "rings flatten out" which an easy way to remember the direction the board will cup but the reason for the cup has virtually nothing to do w/ the growth rings themselves. Cup is reversible on swelling which is why the idea of wetting is given as a cure. Of course, the end then has to be to get the whole board in equilibrium again at that point which goes back to point a) above--if the piece was milled in inequilibrium, it's an insoluble problem w/o mechanical repair. -- |
#28
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How to repair warped table top?
On 2/22/2012 3:36 PM, dpb wrote:
On 2/22/2012 2:28 PM, Michael Joel wrote: Swingman wrote: You don't want to argue because you were mistaken, charitably, either in your wording, or your understanding. And you are very mistaken in your contention that you "doubt anyone knows for sure" ... a first semester, college level, Botany 101 class would prove to you that this is well understood, and well documented with empirical evidence. For your future benefit, and so this ends on an instructive note, you will certainly want to explore the definitive work on the matter: http://www.amazon.com/UNDERSTANDING-.../dp/B000UQH160 Every woodworker can learn something from reading Hoadley, guaranteed. See - that is why I get pulled back in. Because the logic is so illogical. If I said I don't believe they really know what is happening - you say take a "first semester, college level, Botany 101 class would prove" - The only thing it would prove is they believe it. Very circular thinking (as the "scientists" would say). ... Well, that's self-serving to the max. You might as well say that the physicists on believe Newton's Principles; after all, it's "only" a theory. I suggest you do read Hoadley (or any of several references from the US Forest Products Lab, these can be downloaded at no cost); specifically Chap 4, "Wood and Water". The short story is---wood shrinks as it dries and it does so non-uniformly. The tangential/radial shrinkage ratio from green to oven-dry has been measured for some hundreds of species and averages about 2 (roughly an average of 8%/4% T/R) but shows a significant variation between species of from just barely above 1:1 to highs approaching 3:1. The higher the ratio the more the particular would will distort as it is dried as the relative shrinkage in the two directions competes at a different rate. The difference between tangential and radial shrinkage isn't random nor magic; it's caused by the anatomical structure, principally the effect of wood rays whose lengthwise axes are oriented radially outward. Species w/ more predominant rays are more stable. Over the range of moisture content shrinkage is roughly proportional to moisture loss. This doesn't matter too much as raw lumber is dried; the roughsawn stock is oversize to begin with and if dried uniformly will be stable after it is milled given a uniform environment. This is why it is so important to finish both sides of a furniture panel, say--if one side is finished and the other not, differential moisture absorption is highly likely to cause movement. Cupping after the fact is owing to one of two causes--either the piece wasn't at equilibrium to begin with and dried after milling with the resultant change in dimension as determined by the species' particular T/R ratio and the percentage change in moisture. The second is that the piece has subsequently absorbed moisture and therefore grown. The relative amount in the direction is also dependent on T/R and how uniform (or un-uniform) the moisture absorption is. Cupping in flatsawn boards results in concavity away from the pith, the result of greater tangential than radial shrinkage. The magnitude is greater as the location of the board from the original trunk is closer to the pith on a surface. This face is completely radial while the opposite is tangential in the portion across from the location of the pith and will therefore shrink at twice the rate. Woodworkers tend to say the "rings flatten out" which an easy way to remember the direction the board will cup but the reason for the cup has virtually nothing to do w/ the growth rings themselves. Cup is reversible on swelling which is why the idea of wetting is given as a cure. Of course, the end then has to be to get the whole board in equilibrium again at that point which goes back to point a) above--if the piece was milled in inequilibrium, it's an insoluble problem w/o mechanical repair. Wow, nice explanation! Thanks for taking the time to write that up. -- Any given amount of traffic flow, no matter how sparse, will expand to fill all available lanes. To reply, eat the taco. http://www.flickr.com/photos/bbqboyee/ |
#29
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How to repair warped table top?
Paul Conners wrote:
Sticks of wood (lumber). Usually they are used in stacked lumber to keep the wood separated for air flow - and flat. I did not mention that you would want a flat surface under the stickers. Mike Thank you Mike. Three or four 2in x 2in sticks for a 36in x 48in table top? It will be placed on a concrete slab apron in front of the garage. No cracks or obvious defects in the slab. Thanks. Whatever will allow air movement and keep it basically flat (flat is relative really - a wal-mart straight edge is "flat" - unless of course you compare it to a $45.00 straight edge - which is more flat ). Let me clarify (at the danger of possibly being accused of trying to change tack) what I meant when you asked "concave moist side". I meant yes - as in moist side that has dried. I did not mean simply the moist side causes a cup - it would have been made moist while compression was placed on it (i.e. the dry side) and then dry out (but it may also take many many times of this before a cup is seen). Information that is only needed if someone is interested - from books - and not even needed to be mentioned to answer your OP - so I guess my headache was caused once again be me Mike |
#30
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How to repair warped table top?
On 2/22/2012 9:21 AM, Swingman wrote:
On 2/22/2012 12:05 AM, Michael Joel wrote: Paul Conners wrote: Just a note - cupping takes place towards the moisture not away from it. Just to clarify: the concave side is moist, and the convex side is dry? Yes. Well no not normally. The side that absorbs the moisture expands. |
#31
Posted to rec.woodworking
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How to repair warped table top?
On 2/22/2012 3:36 PM, dpb wrote:
The short story is---wood shrinks as it dries and it does so non-uniformly. The tangential/radial shrinkage ratio from green to oven-dry has been measured for some hundreds of species and averages about 2 (roughly an average of 8%/4% T/R) but shows a significant variation between species of from just barely above 1:1 to highs approaching 3:1. The higher the ratio the more the particular would will distort as it is dried as the relative shrinkage in the two directions competes at a different rate. The difference between tangential and radial shrinkage isn't random nor magic; it's caused by the anatomical structure, principally the effect of wood rays whose lengthwise axes are oriented radially outward. Species w/ more predominant rays are more stable. Over the range of moisture content shrinkage is roughly proportional to moisture loss. This doesn't matter too much as raw lumber is dried; the roughsawn stock is oversize to begin with and if dried uniformly will be stable after it is milled given a uniform environment. This is why it is so important to finish both sides of a furniture panel, say--if one side is finished and the other not, differential moisture absorption is highly likely to cause movement. Cupping after the fact is owing to one of two causes--either the piece wasn't at equilibrium to begin with and dried after milling with the resultant change in dimension as determined by the species' particular T/R ratio and the percentage change in moisture. The second is that the piece has subsequently absorbed moisture and therefore grown. The relative amount in the direction is also dependent on T/R and how uniform (or un-uniform) the moisture absorption is. Cupping in flatsawn boards results in concavity away from the pith, the result of greater tangential than radial shrinkage. The magnitude is greater as the location of the board from the original trunk is closer to the pith on a surface. This face is completely radial while the opposite is tangential in the portion across from the location of the pith and will therefore shrink at twice the rate. Woodworkers tend to say the "rings flatten out" which an easy way to remember the direction the board will cup but the reason for the cup has virtually nothing to do w/ the growth rings themselves. Cup is reversible on swelling which is why the idea of wetting is given as a cure. Of course, the end then has to be to get the whole board in equilibrium again at that point which goes back to point a) above--if the piece was milled in inequilibrium, it's an insoluble problem w/o mechanical repair. Very well put and, as a result, that much more informative. -- www.eWoodShop.com Last update: 4/15/2010 KarlCaillouet@ (the obvious) http://gplus.to/eWoodShop |
#32
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How to repair warped table top?
On 2/22/2012 4:27 PM, Leon wrote:
On 2/22/2012 9:21 AM, Swingman wrote: On 2/22/2012 12:05 AM, Michael Joel wrote: Paul Conners wrote: Just a note - cupping takes place towards the moisture not away from it. Just to clarify: the concave side is moist, and the convex side is dry? Yes. Well no not normally. The side that absorbs the moisture expands. Don't look now, Bubba ... but I did not say that. LOL I know ... it's Butch's fault! -- www.eWoodShop.com Last update: 4/15/2010 KarlCaillouet@ (the obvious) http://gplus.to/eWoodShop |
#33
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How to repair warped table top?
On 2/22/2012 1:09 PM, Michael Joel wrote:
Swingman wrote: On 2/22/2012 12:05 AM, Michael Joel wrote: Paul Conners wrote: Just a note - cupping takes place towards the moisture not away from it. Just to clarify: the concave side is moist, and the convex side is dry? Yes. Not necessarily ... and AAMOF, and depending upon the grain and the way the wood was cut off the tree, it more likely to be just the opposite of what you stated ... the concave side being the dry side, and the convex the moist. There are indeed some exception with certain grain patterns due to the way the wood was cut from the log (plain sawn, rift sawn, etc.), or if laminated, but mostly wood cups and checks parallel to the grain and to the drier side. Excellent example is the cupping of hardwood floors, which "cup" (concave side up) when wet from the underneath ... dry on the top, wet on bottom ... one of the main reasons why a moisture barrier is always used _beneath_ a hardwood floor. Another hole in your balloon ... leaving a board to dry out in the sun, The concave side is drier from exposure to the sun and heat, and, once again, the board generally cups toward the dry side. Try this by laying a board on wet grass before the morning sun hits on sunny day, check it out by noon. Here is indeed, "according to the books": http://www.fpl.fs.fed.us/documnts/fp...chapter_16.pdf 16-6: quote Wood warmed by the sun experiences a virtual RH far below the ambient RH. The surface dries faster than the rest of the lumber. This is why cupping and checking often occur on decking boards; the top surface is much drier than the rest of the board. Shrinkage of the top surface commensurate with this dryness causes cupping and checking parallel to the grain /quote Sorry but I believe what I said to still be right. While grain of course will have effects the cupping will take place towards the moist side (or away from the compression pressure might also be a way to say it). Take a look at porches or decks, do you seen any cupped down? Fave you ever found a table top that cupped down? Have you ever seen deck boards or a table top that was not attached? Given restrictions a board will bow in the direction that is not restricted. Given no restrictions the surface absorbing moisture will expand and that will not result in a concaved surface. Your wood floor - is it cupping because it is moist underneath or because of the mopping and drying taking place above? as for the board on the lawn - don't know, would have to try it. Absolutely the underneath side. You mop it and water goes down inside the cracks to lower and side sections of of the board. Those surfaces stay wet longer than the top surface. Then the edges expand and they cut up but the surface has long since dried because of exposure. Your quote - Is it indeed the sun causing the surface to dry faster or is it in fact that the problem is not visual until the surface dries? You are not thinking about all of the surfaces that have actually gotten wet. |
#34
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How to repair warped table top?
Paul Conners wrote:
Google is your friend... Sticker A sticker is a type of a piece of paper or plastic, adhesive, sticky on one side, and usually with a design on the other. Stickers, Bumper Stickers - Sticker Giant Stickers made easy. 26,000 bumper sticker designs in stock. Custom sticker Stickers - Shop for a new Custom Stickers Political stickers, art stickers, funny stickers and millions more! Highest Stickers Galore Stickers Galore offers an incredibly large selection of stickers for \ 123stickers.com - Custom vinyl stickers | Custom Banners ... Custom Vinyl Stickers | Custom T-shirts | Custom Banners. Low minimum custom Then I tried "sticker wood" and got this and the like: http://www.ebay.com/sch/items/?_nkw=...w=&_mPrRngCbx= 1&_udlo=&_udhi=&_sop=12&_fpos=&_fspt=1&_sadis=&LH_ CAds= There comes a point where the flaming of "Don't you use Google?" is worth it... Here ya go then.... http://www.ca.uky.edu/agc/pubs/for/for55/for55.htm I did a google search on the phrase "what is a sticker for drying wood" and came up with this link and a bunch more. -- -Mike- |
#35
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How to repair warped table top?
On 2/22/2012 4:32 PM, Swingman wrote:
On 2/22/2012 4:27 PM, Leon wrote: On 2/22/2012 9:21 AM, Swingman wrote: On 2/22/2012 12:05 AM, Michael Joel wrote: Paul Conners wrote: Just a note - cupping takes place towards the moisture not away from it. Just to clarify: the concave side is moist, and the convex side is dry? Yes. Well no not normally. The side that absorbs the moisture expands. Don't look now, Bubba ... but I did not say that. LOL I know ... it's Butch's fault! In know! I probably posted to the wrong person... Obviously. I knew you were right. |
#36
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How to repair warped table top?
Well, that's self-serving to the max. You might as well say that the
physicists on believe Newton's Principles; after all, it's "only" a theory. I suggest you do read Hoadley (or any of several references from the US Forest Products Lab, these can be downloaded at no cost); specifically Chap 4, "Wood and Water". The short story is---... Very interesting and valuable information. But I'm not sure it's particularly relavent to my situation. If it is warped, simply putting under great pressure (I have a few thousand pounds of red bricks at hand), it's probably not pertinent *which* way it's warped. Placed on small square lumber and weighted, should give some good results. |
#37
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How to repair warped table top?
Here ya go then.... http://www.ca.uky.edu/agc/pubs/for/for55/for55.htm
I did a google search on the phrase "what is a sticker for drying wood" and came up with this link and a bunch more. -Mike- Thanks. That helps. |
#38
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How to repair warped table top?
On 2/22/2012 9:31 PM, Paul Conners wrote:
.... Very interesting and valuable information. But I'm not sure it's particularly relavent to my situation. If it is warped, simply putting under great pressure (I have a few thousand pounds of red bricks at hand), it's probably not pertinent *which* way it's warped. Placed on small square lumber and weighted, should give some good results. You can press it flat all you want but unless you change either the moisture content back to equilibrium at the time it was milled and (presumably) flat or, if as noted previously, it was milled while not in an equilibrium moisture content where it now is it will just return to the present shape again. If you can restrain it sufficiently, you _may_ be able to hold it in place. -- |
#39
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How to repair warped table top?
Excellent example is the cupping of hardwood floors, which "cup"
(concave side up) when wet from the underneath ... dry on the top, wet on bottom ... one of the main reasons why a moisture barrier is always used _beneath_ a hardwood floor. [Swingman] This doesn't hold water ;-) when speaking of this table top. The bottom is not likely to be "soaked" in water but free to dry, much more so than the top. The top is exposed to water (rain, spillage), whereas the underside has little exposure to water except for the little that drips around the edges of the table and which gravity will pull it off immediately. The bottom side of the table top looks nearly pristine, whereas the top looks like it's been through a war: the factory finish (polyurethane?) is still on the underside of the wood but long since baked off the top (from sun exposure). |
#40
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How to repair warped table top?
On 2/23/2012 11:26 AM, Paul Conners wrote:
Excellent example is the cupping of hardwood floors, which "cup" (concave side up) when wet from the underneath ... dry on the top, wet on bottom ... one of the main reasons why a moisture barrier is always used _beneath_ a hardwood floor. [Swingman] This doesn't hold water ;-) when speaking of this table top. The bottom is not likely to be "soaked" in water but free to dry, much more so than the top. The top is exposed to water (rain, spillage), whereas the underside has little exposure to water except for the little that drips around the edges of the table and which gravity will pull it off immediately. The bottom side of the table top looks nearly pristine, whereas the top looks like it's been through a war: the factory finish (polyurethane?) is still on the underside of the wood but long since baked off the top (from sun exposure). You obviously did not bother to read the very specific quote at the end of my post that deals with "sun exposure". LOL You're right that what you quote above does not apply to your table ....nor was it ever intended to. What does indeed apply to your table is the description you used in your original post ... the term "weathered". You might want to go back and read the second "example" I used for the effects of moisture on the dimensional stability of wood, as well as the quote at the bottom which specifically deals with wood subjected to sun and "weather". If you did not accurately describe the condition of your table, then you have no one to blame but yourself for misapplying the examples. Just so there is no mistake how appropriate the quote was to your table suffering "sun exposure" (sic), here it is again: quote Wood warmed by the sun experiences a virtual RH far below the ambient RH. The surface dries faster than the rest of the lumber. This is why cupping and checking often occur on decking boards; the top surface is much drier than the rest of the board. Shrinkage of the top surface commensurate with this dryness causes cupping and checking parallel to the grain /quote It really does help to read an _entire_ post, not just those parts you want to take exception to. -- www.eWoodShop.com Last update: 4/15/2010 KarlCaillouet@ (the obvious) http://gplus.to/eWoodShop |
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