Building board for a workbench top??

[gdjsky01]

Hi ya'll,

I am putting together a shop. I have a very strong ex-kitchen island which is now mounted on eight HD casters. It's 2' x 7' long (.61m x 2.1m). I would like to secure to it a 3.5' x 8' (1m x 2.4m) top as it has no top right now. What should I mount on it and how does one go about making sure the surface is secured to the base, it is not twisted and is wrap free? I intend on building 2 and 3 meter sailplane wings on it. I am looking for durabilty and straightness first and formost. I can then cover whatever that surface is with ceiling tile or 'what not' for pinning.

I guess what I am asking is how does one look for and detect warps in a workbench surface as one is building the bench? As I secure a top, I want to be able to detect and shim out, any warps.


Thank you for your time and best wishes,
Jeff

[schrederman]

Jeff,

I use a sheet of 3/4" birch plywood and a laser level to check for warps. I sometimes have to clamp it to the drawing table underneath as the humidity changes here in Houston can be kind of unkind. I just check it with straight edges before beginning a model. I haven't had to shim it and it now stays clamped ost of the time. I build right in the plywood and drive pins into it with an old pair of diagonals......

Get busy on that Hawk!!!

Jack

[BMatthews]

Get yourself a 6 foot level or a similar length of similar section extruded aluminium stock so that you know it's straight. Use that to set up the top. Use it as a simple straight edge for detecting dips with the section parallel to the edge. Then set it up diagonally and look for a dip one way and a rocking the other. If it's not even on both diagonals then it's twisted. Shimming to elliminate the difference will ensure a level surface. Chances are that it'll have a dip in the middle even if square and level. You'll have to secure and level the four corners first and then shim and pull down the middle areas.

For a little extra help you may want to consider setting the top up with leveling studs instead of just screwing it into place. Set the top in place and clamp down temporaily. Drill up through convienient points at the corners and several other points of opportunity in between so that you can have a support points set no further apart than about 18 inches. Use a size of drill that will let you secure short lengths of 1/4 threaded rod into the holes in the top. I suggest 13/64 or 7/32. Take the top off and re-drill the base with 9/32 for clearance. Bed the 3 or 4 inch long studs in place with epoxy as you screw them in. A simple hacksaw kerf in the ends will let you use a slot screwdriver to do this. Now you can use nuts and washers to set up the level easily and when needed. Use one set of nuts and washers above the base plates and another below. This way you can force the local stud up or down as needed to level and flatten the top. You just need to make sure you can get into the upper nuts from inside the base of the unit so you can properley make the adjustments.

[gdjsky01]

;)
Jeff,

I use a sheet of 3/4" birch plywood and a laser level to check for warps. I sometimes have to clamp it to the drawing table underneath as the humidity changes here in Houston can be kind of unkind. <snip> I build right in the plywood and drive pins into it with an old pair of diagonals......
Get busy on that Hawk!!!

Jack


Thank you Jack. As you know, here in Southern CA we think it is really humid when it hits 40% RH. :D Of course I need only think back to my years in Rochester NY to know just before or after a mid-summer's T-Storm... 90 F (30C) and 80% RH! THATS humid.

If you can build em on that... I can. Honest Jack, please do NOT leave the forum even if real sailplanes are serious fun!

Honest? You drive all those pins with pliers??? That seems pretty hard... or perhaps you use a lot few than I????



This way you can force the local stud up or down as needed to level and flatten the top. You just need to make sure you can get into the upper nuts from inside the base of the unit so you can properley make the adjustments.

Wait! I think I get it.
(Actually I read it aloud to my wife and SHE got it and explained to me me! LOL!) This is fascinating (my best Spock impression). Are you saying in effect to use 'jack screws' to slightly push or pull from underneath depending of what is needed??? Have you found that level of sophistication necessary? It sounds way cool. :cool:

I just know that one needs to try and build straight. You can manage to fix almost anything, but if you can build it straight in the first place, you save yourself some grief. So I appreciate any help I can get!

I had never thought of the jack screw method (if I got that right?)... best wishes.
Jeff

[Loone]

I have a counter space I work off of with a flat of epp foam and a guillows building bourd on top of that for building and wood work. nice and flat and real easy to work with . about 25 bucks from guillows.


MH

[Radian]

This might sound unusual to some of you, but I have found a glass tabletop to be the best building surface for the planes I build.

This is because most of what I do is using composites or foam and tape. No matter how careful I try to be I eventually drip epoxy or CA on the glass. In all cases, after it is dry, a razor blade easily scrapes it off.

When wiring, solder does not stick or burn it either.

Also when cutting plastic packing tapes, I can wet the table with a wet paper towel, lay the tape down on the wet area and trim to needed size or shape. Then the tape lifts easily for putting on the plane.

Another benifit is the surface doesn't scratch and is very hard.

Of course it does have it's limits and I keep a small MDF board handy for other work. Also, all "hammering" is done on a seperate workbench.

[BMatthews]

A large sheet of glass will still sag. Glass is actually quite flexible. Just step up to a large store front window and push lightly in the middle while looking at the reflections and you'll be surprised at how much that 1/2 or 3/4 inch thick glass flexes. But I agree that glass would work well for LOCAL flatness but it still needs to be supported well and accuratley to avoid sagging or twisting for a piece large enough to use for a counter top or even for building a wing on.

GOOD FOR YOUR WIFE :D Yeah, the idea is that you can lift or suck down each jackscrew stud as required for each localized area. Do you need the sophistication of the leveling jacks? I wish I'd thought of it years ago. I'm still using the two benches I made back then. Both of them have one of the 4 legs set up with a jack screw so I can use it to compensate for twisted floors and set the two ends of the bench dead even. Sort of like the jackscrew idea here. But I'm finding that the tops have sagged in the middle over time despite a generous support framework underneath. A jackscrew top would be adjustable to make up for the aging problems I've seen. And then there is the aspect of moving the bench. You can set it up for where it is now but if you move it later then with the jackscrews it's a simple, if fussy, matter to reset the top to flat and level. Speaking of levels, with the top supported by about 8 of these little jackscrews you can set the two ends to dead level and then work from either end in using a regular 3 foot level since you're working the segments only rather than the whole top at once.

I got the idea for this about a year ago and it's filed away in my "Don't Forget" part of my brain for my next worktable. It's particularly applicable to a set of kitchen counter units like you're using as there is no real built in carry through structure to ensure the different parts stay in alignment as the floor moves or the unit is slid to new spots.

[DeuceTrinal]

My favorite table was made from a sheet of 15/16" glass, with a frame I built out of 1"x2" square tubing, welded together to have a leg at each corner with a strut going to the middle to for an x that had a 5th support in the center. This made a table that was flat enough for anything I could build (within 1/64", near as I coudl measure) and you could epoxy, solder, anything else and just clean it with a razorblade.

Unfortunately that table has now been sold, and my new workspace is a workbench made of thickly sealed 2"x8" pine boards just butted together like a deck, with a peice of 1/4" glass on top. The glass isn't nearly as large as I'd like, but the workbench underneath is flat enough that the glass stays within 1/16"-1/32" or less at the worst corner (I avoid that corner), and I can just use the large bench for big stuff. If i need a larger surface for a bult up wing, I use a couple ceiling tiles to make a longer surface that is pinnable, but I haven't done that in a long whle.

BTW - most big window glass is only 3/8" thick, max. Usually closer to 1/4 or less. Anything thicker imparts a very distinct green color to everything. Having dual panes with inert gas in between helps increase the strength of the big windows.

[rogerflies]

I agree with the suggestion to use glass. Mine was two layers of 1/4" plate from a junk patio door supported by a solid core wood door.

One way to hold pieces in place on the glass is to use CA to hold little positioning blocks around the pieces you're working with. A light tap gets the block off the glass, once again proving that CA isn't worth a flip for anything important. Sorry, just had to get in my jab at CA.

Another thing I used for working on glass is rolls of pennies. They're free (since you can spend them later), heavy enough for most things, and a convenient size. You can also link them in strips with packaging tape to make a flexible weight for holding wing sheeting on the leading edge while the glue dries.

Stamp your name on the rolls before you tape them together so they'll already be marked when it comes time to spend them. It's hard to mark over the tape.

Roger

[robert harik]

A cheap ,easy and straight building board is a hollow core door. You can buy them for about $15-$25 at Home Depot. You can put a sealer, like water based poly on all sides to keep it more warp resistant, though I have never had a problem with warping in all the years I have used them. Its also light weight so you can move it around if you need to. You do have to use a small hammer or plyers to put in the pins, but the pins hold very well.
You do have to support it somehow. I just put mine on a large folding table.

[rycomm]

I use a couple of ceiling tiles on a hollow core door. I buy damaged tiles to save some money. This has worked well for me. For my woodworking, I use solid core door, with vices and dogs, but thats overkill for models.
Ryan

[SoCalGliderFlyr]

Thick plank of clear soft pine 12" wide by 7 feet long. Glued 3/4 x 1 1/2 pine stock along the bottom at the edges and in a bridge like truss arangement between them. Used wood screws from the top to hold everything in place. Put it on a very flat cement garage floor and piled as much weight on the top as I could find. Let it sit for serveral days while the glue diried. Removed the wood screws and had the top planed flat then the bottom planed flat. Did this in 1972. It's been resurfaced a few times since and is getting a bit thin. Almost time for a new one.