What is Best Material for Flat Panel Tables?

Discussion in 'Materials' started by CatBuilder, May 13, 2012.

  1. CatBuilder

    CatBuilder Previous Member

    I have some Advantek that I bought at great expense to make my strongback into a table to do infusions on.

    Well, it was somewhat warped, in that I need to do very minute fairing thanks to the Advantek sheets not staying perfectly flat.

    What other surface can I use (that can be walked on) that is readily available and not terribly expensive in the USA?

    I don't need it to be a mold release because I just lay down some poly plastic on the surface I have now to protect the infusion bag. No big deal. It just needs to be incredibly flat.
     
  2. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    The only truly flat products I have seen are either MDF or Particleboard. Steel is great, but expensive of course. Commercial flooring just isn't that precise.

    Even with Ply, to get a perfectly flat surface, I have to buy two thinner thicknesses, and glue them together weighted and cramped down onto some other perfectly flat surface.
     
  3. CatBuilder

    CatBuilder Previous Member

    At what intervals do you need to support the MDF to keep it flat? Even my premium Advantek flooring is not staying flat. Each sheet gets a concave in it.


    [​IMG]
    http://www.advantechperforms.com/product-lineup/advantech-flooring.aspx

    While we are at it can anyone who has built a boat please give me some tips on speeding up a build?

    The fairing and painting is looking to be a half a year project in itself.

    What is the quickest way to whip out flat panels to shape and get things done so they are painted in the shortest amount of time?
     
  4. tunnels

    tunnels Previous Member

    a sheet glass is the best ever , Sheet aluminium is pretty good but scratchs easy , sheet steel is ok but has to be painted with gloss epoxy paint . MDF with meltica is resonable , And just MDF is porous . As for partical board well dont even go there !!. :D
     
  5. pdwiley
    Joined: Jun 2008
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    pdwiley Senior Member

    Oh, that's dead easy.

    Do NOT start. Buy, don't build. I realise it's a bit late for that and the advice wasn't taken by myself either, so....

    On painting, it is dead slow. Painting the interior of mine has taken far longer and been more painful than I could have imagined. I'm hoping the exterior will be a lot quicker & simpler. At least there are no stringers etc, OTOH paint runs aren't really acceptable so I need to take more care.

    BTW IME steel sheets are not flat, FWIW. The only answer to how many supports your table needs is, as many as it takes to reach *your* standards of flatness.

    If you want certifiable flatness, try a granite surface plate; mine comes with a certificate that says it's flat to less than 5 microns. Good luck finding the size that you want though. Not to mention paying for it or moving it (mine is 180kg for 600mm x 900mm surface area).

    I would be tempted to build a steel angle sub frame with judiciously placed jacking screws and put your MDF etc on top, fastened down. You could then use a good level (not a carpenter's level or cheap laser level) to spot the surface and adjust from below until you reached your desired level of 'flat' or ran out of patience, whichever came first.

    This is basically how I built my welding platen but I only cared to get it flat within the 'spot' from my laser level, which is approx 3mm, so pretty coarse.

    PDW
     
  6. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    If you need a bigger table, then the only way to ensure micron level flatness is to support the sheets at ~ 1 sq metre intervals. The cheapest support base is more mdf panels supported vertically underneath the horizontal panels, like making boxes. You can fine tune the 'bed' by using those threaded legs like they do on kitchen cabinets on unlevel floors.

    You could also use steel folded U sections ( roof purlins etc) as the cheapest steel base. You can easily build up a really flat grid of light or heavy steel sections to lay mdf or particle board on. It has the advantage of not being subject to moisture deformation.

    Glass is certainly flat, but once again, only if supported properly, and it is soooo heavy to move sizes around that you can walk on. - not to mention expensive for new stuff.

    The 'flat' steel I was talking about was not steel sheet, PD, but square sections. I have one large one I have just used to make some straight beams with. You cant get 8 metre lengths ( you know, the ones you put on top of your ute :) ) to minimize possible joining bends.
     
  7. SheetWise
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    SheetWise All Beach -- No Water.

  8. pdwiley
    Joined: Jun 2008
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    pdwiley Senior Member

    I hadn't thought about glass but that's likely because it'd last ~5 seconds after I struck the first arc and a bit of spatter hit the surface.

    Interesting though as I have 16 (I think) 16mm thick glass doors approx 2100 x 900 lying in the weeds. Throw-out stuff from a previous job when they did a building renovation. I've always been planning to use them as a glass wall in the next building here. I had the opportunity to get a lot more and passed it up. Oh well.

    Square sections of steel (RHS) incidentally are often not 'flat', IME, depending on your definition of 'flat'. Flat enough (straight enough) for construction purposes, yes. Catbuilder hasn't defined what his acceptable deviation from 'flat' is.....

    Distance from my front carry bar to the rear one is just on 5.4m so carrying an 8m stick of 'whatever' is only just illegal (yeah I know, that's like being just a little bit pregnant) as you're allowed 1.2m overhang front & back. 6m & 7.2m lengths are fine AFAIK - based on my knowledge of NSW rules, I might add. Anyway the cops have never shown any interest in me carrying long lengths.....

    PDW
     
  9. Charly
    Joined: Dec 2009
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    Charly Senior Member

    For four foot wide table, Four I joists for the runners. Two bys on the flat for the crosspieces. screw them down on 16 inch centers. also two by cutoffs running length wise atop the joists in between. scew advantech to that. Space peripheral screws on sheets at 4 inches. six inches in the field. don't bang up the tounge and groove joints too tight. leave an 3'16 inch gap for swelling. you could put some masonite over that if you wanted to.
     
  10. groper
    Joined: Jun 2011
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    groper Senior Member

    Catbuilder, i made my table by welding up a steel frame to support 16mm melamine covered chipboard i bought from the hardware store -cheap. Could have done the same with MDF but then i would had to buy/glue the melamine laminate to it or seal it some other way whilst keeping it flat - making it more expensive / time consuming. I used a steel frame, because timber is just too warped - its never stays straight...

    The steel frame i made from 75x50x2.5mm RHS steel. The steel frame supports the melamine boards at 24in centers - anymore than this and it would probably sag between bearers. Its very flat - not perfect - as over the entire length of the table there is a slight wave / warp that you cant notice without eyeballing it level from edge to edge - looking from any other angle it looks dead flat. Each sheet i routed a V into the edge and glued together with epoxy, then sanded the joint flat afterwards to make sure its was vacuum sealed... my first attempt with silicone joins didnt hold vacuum...
     
  11. rwatson
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    rwatson Senior Member

    Yes, the definition of flat is the key - and maybe a bit of a curve wont matter as long as the surface is flat crossways.



    Just looked up tassies load regs - they have made it a bit more complicated at http://www.transport.tas.gov.au/__data/assets/pdf_file/0005/73679/R_-_Rear_Overhang_15_Nov_2011.pdf

    if you failed primary school math like 80% of Tassie kids, you are in trouble
     
  12. pdwiley
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    pdwiley Senior Member

    Cool, I'm in compliance carrying 8m as long as I have a flag on the end. Usually I tape/tie some rag there so close enough.

    Total thread deviation but I was one of the senior developers on the new Tassie registration system to keep myself amused for a bit before retirement. One of my friends got booked because the ANPR (automatic number plate recognition) system picked out the vehicle was out of registration (by 1 day, bit of forgetfulness due to a family emergency). I was *not* popular when I said I'd had a hand in it, nor when I said that I'd spent a fair amount of time closing every code loophole that I could find...

    Mind you there are a couple of loopholes in the Tas rules themselves, but I'm not saying what they are and they're of no use except for very special conditions....

    PDW
     
  13. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    If you build a table consider the effects temperature and humidity level changes and the parts try to expand/contract different amounts. I know from experience that MDF with pine reinforcements glued to it does not stay flat with a large change in humidity.
     
  14. CatBuilder

    CatBuilder Previous Member

    Wow, that is a lot more support than I was using. I used my strongback with regular station spacing for 2x4s and nothing else. Were those I beams the premade ones with plywood web and regular wood tops and bottoms?

    I need a 25' x 8' table.

    I also tapped the tongue and groove into place. Probably another mistake.

    The table was taken apart for shop logistics, so i will put it back together as you are saying here. The worst parts were at the tongue and groove joints, so that should go better leaving them loose this time.
     

  15. Charly
    Joined: Dec 2009
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    Charly Senior Member

    Yes the I joists have osb webs and glue lam flanges. you can level the whole thing up at the corners, then come back and add more vertical supports, along the middle.. Since your floor is probably unlevel. I used four foot vertical spacing for the legs, probably overkill. I wanted to make sure the thing didn't move. Also thwart braces out of more two bys set right down on the floor, and screwed to the legs makes the table much more stable.

    The advantech axis of strength is long ways, so if you make the table eight feet wide with eight foot seams running across, you need at least 16 in centered supports running fore and aft.
     
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