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Thread: Conference Table

  1. #1

    Conference Table

    Hello,

    I have a 4'x10' conference table I've been working on. It is made of 1 1/4" white oak slats, each slat being 1 1/4" thick and 48" long, so they are running perpendicular to the length of the table. The base is 82" in length and has steel support between the legs to support the top. The individual parts of the top are glued and have 5 14x140mm Dominos ea. Because the wood is perpendicular to the length, it needs as much support as possible. I'm considering inlaying steel under the table, or using angle iron to offer extra rigidity. It has a center console for power and cabling that is yet to be installed.

    I have decided I'm going to assemble the table in a solid top that is full length so it can be finished properly. Then I have two options, I can leave it as a solid top, which will be large and hard to move, but not impossible, or I can cut it in half, into two 5' sections, then perhaps use alignment dowels and a tensioning system underneath. Since the steel base has direct support under the main 6' body the joint would be supported. The wings extend out by 2' unsupported on each end, so it would be 3' on the base, and 2' unsupported (except for the steel I add under the top). That seems like it would add a lot of stress to the center joint. The other issue is the center console for cabling and power also needs to go in the middle of the table. This will sit right in the middle of the joint.

    I was hoping to get some opinions on the best way to proceed.

  2. #2
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    With a sense of humour,

    as this may be a good learning experience.

    A 10' wide slab of flatsawn oak may want to move from season to season you could be talking 1" or more across the 10' length. Hope that your design can accommodate that.

  3. #3
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    A top which is 1 1/4" thick cantilevered 2 feet makes me nervous. Somebody may try to move the table by picking up on the ends of the top. I'd look for some way to extend the base, either with steel or wood. Can you cut the base in the middle, and spread the legs further apart?

    Mark is right: the wood is going to expand and shrink across the grain. You should fasten the wood top firmly to the base in the middle, and fasten it with sliding joinery away from the middle. The sliding joinery has to allow horizontal sliding, but no (or little) movement vertically. And I'd say it has to survive some gorillas who attempt to move the table by picking up at the ends of the top. That's going to be a lot of weight to pick up.

  4. #4
    Quote Originally Posted by Mark Hennebury View Post
    With a sense of humour,

    as this may be a good learning experience.

    A 10' wide slab of flatsawn oak may want to move from season to season you could be talking 1" or more across the 10' length. Hope that your design can accommodate that.
    Hi Mark,

    I went with plain sawn; I believe it will be ok, the steel is for vertical support, not for tensioning the wood together. Its loosely anchored to the stand, again its there to provide vertical support from downward pressure. The table should able to expand and contract in all directions. Is that what you meant, or possibly I misunderstood?

    Derek
    Last edited by derek labian; 01-22-2022 at 1:02 PM.

  5. #5
    Quote Originally Posted by Jamie Buxton View Post
    A top which is 1 1/4" thick cantilevered 2 feet makes me nervous. Somebody may try to move the table by picking up on the ends of the top. I'd look for some way to extend the base, either with steel or wood. Can you cut the base in the middle, and spread the legs further apart?
    I'm also nervous, I'm going to be re-inforcing it with some type of steel, I just haven't decided what yet. Because the tabletop is perpendicular to the length, if I widen the legs out, the middle will sag. I feel pretty confident I can make the tabletop stable. I am planning on using sliding anchors to attach the top to the base. Similar to:

    Whi1000-0008-2.jpg

    Any thoughts on cutting in the middle or leaving as a solid piece?
    Last edited by derek labian; 01-22-2022 at 12:38 PM.

  6. #6
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    Quote Originally Posted by derek labian View Post
    ..Any thoughts on cutting in the middle or leaving as a solid piece?...
    Consider the path the table must take to get to wherever it is going. Can a 10'x4' object get through? For instance, is access to the conference up an elevator, or up stairs with a bend? And do you have a crew big enough to move an object that big and heavy?

  7. #7
    Are you familiar with the shrinkulator? I havent punched it in but as Mark mentioned I would guess you may be looking at more like 2" of growth with maybe a 5-7% swing? Its not to say if your basically doing a massive 4' wide x 10' long strip oak cutting board with the strips running on the 4' axis you couldnt accommodate the movement but it will definitely take some support and probably long slotted holes in your steel fasteners and something like bellvile or way washers.

    In addition expansion/contraction I'd be pretty concerned with it staying flat but balanced finish, nothing is impossible.
    Last edited by Mark Bolton; 01-22-2022 at 2:00 PM.

  8. #8
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    Hi Derek,
    The table will move across the 10' span, maybe well over an inch seasonally, It will shrink and expand due to changes in humidity. As Jamie said fasten it solid in the center and let the movement take place in and out from the center. So no slots in the center fasteners, just tight round holes. slots in the fasteners either side. And the other possible problems that Jamie has mentioned.

    Quote Originally Posted by derek labian View Post
    Hi Mark,

    I went with flat sawn; I believe it will be ok, the steel is for vertical support, not for tensioning the wood together. Its loosely anchored to the stand, again its there to provide vertical support from downward pressure. The table should able to expand and contract in all directions. Is that what you meant, or possibly I misunderstood?

    Derek

  9. #9
    Quote Originally Posted by derek labian View Post
    Any thoughts on cutting in the middle or leaving as a solid piece?
    What would be your plan to finish the cut edge after you finish the main top? Sharp fractured corner on the finish of the main top would not wear well and if you were to try to finish the cut edge after you cut it you'd never be able to have a top edge corner that you'd be happy with trying to put finish on the cut face (assuming a film finish given its a conference table).

    Cutting it post finish seem a nightmare. Either cut it and finish it as two pieces, use dowel pins and hardened drill bushings for registration or leave it as one piece and hire some help.

  10. #10
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    Derek,

    Flatsawn lumber will shrink and expand twice as much as quartersawn. This design is at best a problem done in solid wood, Quartersawn would have been less worrisome, but still, something I would steer clear of. But it depends, and will be interesting and educational. Good luck.

  11. #11
    Quote Originally Posted by Mark Hennebury View Post
    Derek,

    Flatsawn lumber will shrink and expand twice as much as quartersawn. This design is at best a problem done in solid wood, Quartersawn would have been less worrisome, but still, something I would steer clear of. But it depends, and will be interesting and educational. Good luck.
    Oddly this was a wild facebook marketplace image I saw today... the danger of going into the woodworking business.... I have no idea:

  12. #12
    Thank you for the insightful responses. Let me give a bit of additional background on this project.

    1. I purchased the wood for this project about a year ago, and at that time, the requirement was for an 8' table. I went with plain sawn because the cost was almost double for quarter/rift and this project was going to be indoors.
    2. Because I purchased wood for an 8' table, but now needed a 10' table, I decided to go perpendicular. I found someone making table in this style, using steel under-support to reinforce the weak edge joints. I have no idea how the planks were joined beyond that.
    3. I purchased the steel frame based on what was available and what was acceptable to the customer. I did consider commissioning a custom steel frame for this, but I decided that reinforcing the "wings" with steel, either angle or box, would be sufficient for support.

    That said, I know the table would expand, but I was not expecting up to 2". The wood all has surface moisture between 4.6% and 6% currently. According to the wood calculator I used, if the wood goes from 6% to 4% (equally) it will shrink between .2" and .4". If it goes from 4% to 8% the change should be .4" to .8". That seems reasonable to me, but I'm no expert. I was hoping the indoor environment would be relatively stable. The designs I saw using these same methods were also plain sawn.

    Quote Originally Posted by Mark Bolton View Post
    Are you familiar with the shrinkulator?
    I was familiar with the concept but I have not used it. I did just use it though and my calculations are above.

    Quote Originally Posted by Mark Bolton View Post
    but it will definitely take some support and probably long slotted holes in your steel fasteners and something like bellvile or way washers.
    I agree, I haven't recieved the base yet, but I expected to have 1" slots. I also expected the expansion to be cumulative, so by using shorter steel support for the wings, less than the main frame, the overall movement they need to accommodate should be less (I think).


    Quote Originally Posted by Mark Bolton View Post
    In addition expansion/contraction I'd be pretty concerned with it staying flat but balanced finish, nothing is impossible.
    I was hoping the long rest time would help with long term stability, I know surface moisture is only part of the picture on thick wood though. The assembly and final location are of similar temperature and humidity etc too. I'm not sure there's much more I can do other than the finish? Perhaps finish will help seal the surface from moisture.

    Quote Originally Posted by Jamie Buxton View Post
    Consider the path the table must take to get to wherever it is going. Can a 10'x4' object get through? For instance, is access to the conference up an elevator, or up stairs with a bend? And do you have a crew big enough to move an object that big and heavy?
    I think it will fit into the office and through the doors. I measured and it doesn't have to go up any stairs or elevators. My primary concerns was weight and stress in moving.

    Quote Originally Posted by Mark Hennebury View Post
    Hi Derek,
    The table will move across the 10' span, maybe well over an inch seasonally, It will shrink and expand due to changes in humidity. As Jamie said fasten it solid in the center and let the movement take place in and out from the center. So no slots in the center fasteners, just tight round holes. slots in the fasteners either side. And the other possible problems that Jamie has mentioned.
    I think your right, the stand, below, could be fastened along the rails and floating/sliding as it radiates outwards.

    il_794xN.3611116330_rsid.jpg


    Quote Originally Posted by Mark Bolton View Post
    What would be your plan to finish the cut edge after you finish the main top? Sharp fractured corner on the finish of the main top would not wear well and if you were to try to finish the cut edge after you cut it you'd never be able to have a top edge corner that you'd be happy with trying to put finish on the cut face (assuming a film finish given its a conference table).


    Cutting it post finish seem a nightmare. Either cut it and finish it as two pieces, use dowel pins and hardened drill bushings for registration or leave it as one piece and hire some help.
    The plan was to leave the grain exposed, and put a partial profile on the edge around all sides. If I cut it, I was going to do the edge first, then cut in half. Once in two parts, finish both parts. It seems like cutting it in half might be more trouble than benefit, and I like the idea of finishing it as a single piece.

    Screen Shot 2022-01-22 at 1.09.00 PM.png

    Quote Originally Posted by Mark Hennebury View Post
    Derek,


    Flatsawn lumber will shrink and expand twice as much as quartersawn. This design is at best a problem done in solid wood, Quartersawn would have been less worrisome, but still, something I would steer clear of. But it depends, and will be interesting and educational. Good luck.


    I didn't know that. It was my understanding that rift/qtr sawn would only expand outward from the face, in other words, the edges would expand/contract, but not the face.

    Thank you for all the feedback and advice.

  13. #13
    Quote Originally Posted by derek labian View Post
    The plan was to leave the grain exposed, and put a partial profile on the edge around all sides. If I cut it, I was going to do the edge first, then cut in half. Once in two parts, finish both parts. It seems like cutting it in half might be more trouble than benefit, and I like the idea of finishing it as a single piece.
    I had incorrectly assumed you were going to finish the entire top in the shop then cut it in half for ease of transport. Your plan is much more sound. Hardened drill bushings and dowel pins will make for very precise alignment (cheap, mcmaster carr). Your central void for the data/electric who knows. Sketch it out in CAD.

    All you can do is do your best to accommodate the expansion. My guestimate of 2" would be based on wood moisture content not R/H but I can honestly tell you I have made numerous bread board edge dinning tables that are in the 36-40" width range in various species. All flat sawn material for the same reasons you are using flat sawn. And its not uncommon for any dinning room table with breadboard ends to see 3/16" seasonal change in the field thickness PER SIDE throughout the year. Its why I hate breadboard edges. Customer will want you to cut the field back when its proud of the breadboard edge (summer) and they will want you to cut the breadboard edge back when ITS proud (winter). This process would result in an ever narrowing table until the summer/winter spread in difference is acceptable to the owner.

    So at the 3/16" per side on a 36" wide table thats 3/8" over 3'. x 3 gets you closer to an inch, likely more, not near 2" But still a lot.

    All the tops Ive ever made are fully balanced finish both side. Not so say there is the final sanding on the bottom edge but if theres 2 coats on the top theres 2 on the bottom, all edges, etc.. That will buffer the moisture issues but never eliminate it.

  14. #14
    Quote Originally Posted by Mark Bolton View Post
    All the tops Ive ever made are fully balanced finish both side. Not so say there is the final sanding on the bottom edge but if theres 2 coats on the top theres 2 on the bottom, all edges, etc.. That will buffer the moisture issues but never eliminate it.
    Do you know if any particular types of finishes will retard RH moisture absorption more than others? I assume (and I have no idea) that a polyurethane will work better than a water based sealer, but I'm wondering if a clear epoxy would be even better?

  15. #15
    Most finishes (commercial finishes) that I know of dont give perm ratings though I'd imagine in situations like flooring and heavy industrial/aerospace maybe would. Any film finish is going to dampen the swings. I'd imagine full epoxy encapsulation being about at the top of the list but I wouldnt discount any good quality waterborne finish by default but there is going to be movement period. Any finish is going to eventually break over a joint (hole in the balloon), etc.. and dealing with it is just what it is.

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