Flat ? What's Flat ?

My shop's floor is not dead level and my WW2 surplus office desk/work bench is not 'true'. I did overlay the top with 1/4 inch thick plate glass and plan on using 1/2 inch 'sheet-rock' on that as a building surface.Will this give me the FLAT I need to build a wing straight? Assuming my skills are adequate.("NEVER assume")

Thanks for any input.

Phil

Phil,

I have wondered the same thing. I build on sheetrock, and use a level and long straight edge and shims to true up my drywall building board. It seems to be true enough, but I don't really know.

I thought all one needed was a flat building surface???

SoHawaii
Ua Mau Ke Ea O Ka 'Aina I Ka Pono
("The Life/Sovereinty of the Land is Perpetuated in Righteousness")

I think You are right!

>My shop's floor is not dead level and my WW2 surplus office
>desk/work bench is not 'true'. I did overlay the top with
>1/4 inch thick plate glass and plan on using 1/2 inch
>'sheet-rock' on that as a building surface.Will this give me
>the FLAT I need to build a wing straight? Assuming my skills
>are adequate.("NEVER assume")
>
>Thanks for any input.
>
>Phil

Phil,
Put the glass on top of the sheetrock, instead. Shim it if necessary.
It must be flat AND levelled.
Don't use this surface as a workbench. ONLY as a building surface.

Enjoy,

Claudio Chacón
ARGENTINA

>My shop's floor is not dead level and my WW2 surplus office
>desk/work bench is not 'true'. I did overlay the top with
>1/4 inch thick plate glass and plan on using 1/2 inch
>'sheet-rock' on that as a building surface.Will this give me
>the FLAT I need to build a wing straight? Assuming my skills
>are adequate.("NEVER assume")
>
>Thanks for any input.
>
>Phil

Yes, "flat" is all you need. However, glass is a liquid (or so I have read) and even 1/4 inch glass can bow if the length is long enough and it is not adequately supported. I would get a long straight edge and check it in several directions (including diagonally) to make sure it is true. If it needs additional support, check with a couple of real estate offices and hint that you might be interested in purchasing property in the future. They will heap upon you many business cards which you will find are perfect for use in shimming your table top. You don't want to give them a real phone number, however, or you will never have time to build.

Seriously, the flatter the building surface is, the better. And business cards do make good shim stock to insure that it will remainn such.

sport and stunt flyer

I have found that a blank door from the local building supply works great for a flat work surface. I set mine up on cabinents with drawers in the bottom where I can keep all my building supplies, when I used it temporary I put it on saw horses. I use the luawn doors they are cheaper and the wood is softer. I never thought about the drywall before that might work out good. It should be easy to pin to.

But because of the way cheap doors are made they are very flat and hollow inside with cross webbing to keep them that way. Putting a piece of drywall on top might be even better I must try that

>sport and stunt flyer
>
>I have found that a blank door from the local building
>supply works great for a flat work surface.

>But because of the way cheap doors are made they are very
>flat and hollow inside with cross webbing to keep them that
>way.

Every single door I've examined at several home improvement stores has been anything but flat. This goes for the hollow core wood and non-wood doors.

I've given up looking for a ready made flat surface.

Instead of a ruler, I heard someone comment a 48" fluorescent tube is a very precise straight object to reference your surface against.

>sport and stunt flyer
>
>I have found that a blank door from the local building
>supply works great for a flat work surface.

My eyes and brain aren't connected this morning: when I first read the above I thought he said "a BANK door". well that sure should be flat. and stay that way

>Seriously, the flatter the building surface is, the better.
>And business cards do make good shim stock to insure that it
>will remainn such.

FWIW, another source of good shims is a deck of plying cards...

Hi Phil. When I got back into toy airplanes, I took my Sears work bench, flipped the slightly warped press board table top over, placed three pieces of 3/4 inch board (the coated stuff used for shelves) on that and topped it with a 5/8" tempered piece of glass I had cut at a local glass company. Then by sliding my feeler gauges along the length, found the low or high spots and used very hard 1/32 " balsa to shim it to dead level. Worst spot was .005" (thickness of a one dollar bill). Not bad. But I got it down to .001". That was four years ago and it is still dead level. The garage floor is very level too, so very little shimming of the table legs was needed. I build on the glass or on a large balsa building board.
The main thing, after getting it dead level, is get the height just right for you. No one can tell you this, only you will know. Saves on sore backs, and I use a floor mat so my old feet don't get too tired. But then I spend 5 to 9 hours a day building. Got lots of kits, need the time.

Thanks so much for the ideas.Still ...if I get the glass "dead level" should I use the sheetrock? Is it stabel? And is it "true"?

I use a lazer level to check everything. $19 at Harbor Frieght. Works great for the trailing edge. To make sure that it's stright.

It needs to be flat, not necessarily level. As long as the surface is flat you can use a square, protractor, etc. and your model should build true.

My hobby shop is very cluttered, and I HAD to build my Larry Richards Bearcat. Only room left was in my Hot Rod shop, on top of my Chassis Jig, which is 8 ft. long, and dead-level. I have a cargo door from the interior of an airplane, aluminum double-skinned over a honeycombed inner structure that I use for a building table.
A visitor gaped at what I was doing, and asked "Why the toys on the Hot Rod Table?" "Priorities," said I.

Doors do make good work benches but they should be of the solid core variety. The other ones flex to much. I had a metal bench built for me and then topped it with 3/8" glass that I put 1/4" bulletine board cork on the bottom of. Doesn't really matter now as I have one of Tom Morris's wing building tables. They are very nice indeed.

Bill

<<<>>>But I got it down to .001". That was four years ago and it is still dead level. The garage floor is very level too, so very little shimming of the table legs was needed. I build on the glass or on a large balsa building board.<<>>>

You got it down to One Thousandths of an inch? How did you measure that? Did you use an Optical Flat? Laser? Fen Shue?

I mean Jeeze! All that work and if you accidently hit it with the 400 grit once too many times, your work of art might as well go into the trash can.

One Thousandth of an inch? You're kinda stretchin it a bit aren't you?

From somewhere near Parkville, Mo.
William Crane
AMA 6733

LAST EDITED ON Jul-29-04 AT 04:52 PM (CDT)
 
The further along I get in 'the hobby' the pickier I get about details!

The first thing that I used as a building board was an old oak desk, then I switched to a drawing table and later used a drawing table with a hollow door on top. A few more planes down the road, I used an old dresser, that I topped with a sheet of glass, shimmed flat.

When I decided to set up my new workspace, I kind of lucked out.

On one of my trips to the dump, I found a 6 foot-long bathroom cabinet with plenty of storage space underneath. It's really well built, and only costs $12 at the recycle office!

I topped it with 3/4" pressboard (the stuff with the white plastic laminate on top.) I was intending to shim that flat and then cover with a glass sheet.

Then I got REALLY lucky and snagged a 5'x 25" x 3/4" black Granite countertop from a stone companies reject pile, for free. I checked the stone, after I got it home, and couldn't find any gaps under my best (very expensive!) ruler.

Later today, I'll be picking up a sheet of 1/4" glass to use as a building surface.

Now, maybe I'll be able to build a warp free wing! LOL!!!

I could jig build and still warp it, but I'm trying. Amazing what a good ruler can do.

I'm afraid "flat" is only relative, and for most purposes the eyeball is good enough. I built a complete new lower left wing for my 1938 Focke-Wulf 44J (Steglitz) biplane by making two saw-horses. After aligning them together, the finished wing didn't require any "tweaking", and it is still flying! There was no assurance that my concrete shop floor was level and not twisted, once the saw-horses were separated by about 15' to recieve the spars.

Some of my models have had slightly twisted wings. Although my work bench is as level as humanly possible, things happen during covering and doping. No matter how careful you are, it will usually take a couple of trim flights and some "steam kettle" work to get a plane o fly just right. That is part of the trim process.

Nope, I used my set of feeler gauges. I have six sets I used as a Diesel Mech. Never had to use the real thin ones until I got back into modeling! The .001" gauge is very thin, obviously, and just slid under the glass at the middle of the table. All my shims were in the middle. I put them under each board, so they did not have a hump in them. Table, shim, board, shim, board, glass. You can get feeler gzuges in steel or brass. The brass ones are for electonic systems where any magnetism may exist and throw off a steel gauge or worse magnetize it.

>I spend 5 to 9 hours a day building.

I wished I could find 5-9 hours a day just to sleep!

They say that as you get older, you only need 6 hours of sleep a day. That's about all I need. Just like in the fleet, if you were lucky! I'm retired, for the third time, wife makes the big bucks, gives me a nice allowance and lets me stay in the garage all I want. That way she gets to watch girl flicks or her sports, drink beer, fart, eat popcorn, (none for me that way), scream at the umps. cheers for her teams (Broncos, baseball Cardinals). My kind of gal.
Actually she drinks diet coke.

LAST EDITED ON Jul-30-04 AT 03:29 AM (CDT)
 
I suppose one way to detect any tilt or curvature on glass is to spill some BBs or ball bearings (aha.. that's where the term "BB" came from.. ) onto it and see which way they roll...

OK guys, time to 'fess up. How many set up their building table to a gnat's butt, then "eyeball" the stab position?

LAST EDITED ON Jul-30-04 AT 08:57 AM (CDT)
 
> OK guys, time to 'fess up. How many set up their building
>table to a gnat's butt, then "eyeball" the stab position?
>
> George

Reminds me of "close enough for government work" = measured with micrometers, marked with chalk, cut with an ax

Actually I do wonder how flat is flat enough? I use a steel covered exterior door on a steel workbench frame that has been shimmed so I can't see light under the edge of my straight edge and leveled with a bubble level. My great plains incedence meter is only good to .5 deg. I really don't know about the accuracy/repeatability of my bubble level. And we're working with wood here. which for me at least tends to move a bit sometimes after it's removed from the jig despite my best efforts. It also changes a bit with humidity and when a finish (PC)is applied. Thus requiring some steaming and checking with a laser line device... That laser line can easily be 1/16 inche wide. Nice thing about the steel door is that I can use magnets to position stuff. After all is said and done I'd bet that none of my work is better than +/- .5 deg. Better than the old TLAR method but not much... How good are the master builders? .1 deg? .01 deg?

> OK guys, time to 'fess up. How many set up their building
>table to a gnat's butt, then "eyeball" the stab position?
>
> George

Guilty, my building bench is flat withen the thickness of a time card but I still align the stab to the wing via the old eyeball. When I bought my UHP Impact kit it came with laser cut plywood alingment gigs ala Paul Walker.. I may actually use them when I build it

Bob,

This isn't necessarily aimed at you but next in line as I write this. I know I probably missed something here. I wonder why anyone would need an incidence meter, laser level etc. Don't get me wrong here, I’m not trolling or trying to Sparky you. I've gotten by so far by laying a line straight down the fuselage side in line with the engine bearers. Assuming I want a zero angle of incidence for wing and stab, I put the center of the leading and trailing edges of the wing so the line will bisect the center of the wing or stab or a parallel line. If I want neg. or positive incidence I use a protractor to establish that line from the original line. Is there really a big advantage to using the incidence meter? Maybe the incidence meter is used to check a completed model?

I pretty well do the same as you when laying out the fuselage but something seems to always get slightly off during the cutting/building. I always use an incidence meter (actually two) when installing the stab. It seems to only take a little more preasure/glue/balsa dust on one end or the other to get it a couple of degrees off.

I use an incidence meter(2 actually) to check for warps, one at the root and the other at the tip. But I don't use one while building, just lots of measurements from reference lines or bench top.

I submit to you that I have the ONLY usable method of building straight and level, ahhhh I just can't do it like that other guy.

Well anyways, I do set things up, run the ruler on the edges all the way around. Center a string on nose and aft and measure and square and level and make sure evertying can make it, then apply glue and do it all again. And while the epoxy is setting up, I think the CATS GET TO IT!!!!

THAT'S RIGHT. DIRTY ROTTEN FELINES ARE RUININ MY STUNT CARREER!!!! I KNOW THE 3RD YOUNGEST IS A CARRIER PILOT, PARTIAL TO GRUMAN SHIPS (cats, get it, hellcat, wildcat, tigercat, kittycat)

Oh well, if it wasn't for the cats, the Dogs would sit on them!

LAST EDITED ON Jul-31-04 AT 02:06 PM (CDT)
 
My BLANKING CAT got into a cardboard box holding 3 or 4 rubber free flighters I built over a period of six months on a carrier in my stateroom, AND ATE THEM. EVERY BLANKING PIECE.

I HAD SEVEN, S E V E N, OF BLANKING THINGS (cats that is) AND THIS IS THE ONLY ONE LEFT.

I ' L L P A Y S O M E O N E T O C O M E S H O O T T H E
T H I N G ! ! ! !

uh, sorry, I feel better.

Tools

Oh, I frequently build on a 16"x7' solid cast iron surface, that's DEAD flat (BIG old jointer). Then eyeball everything else. If everything is going well, I sometimes deliberately glue a piece on crooked to appease the Murphy gods and prevent bigger problems later on.

I think the wood quality and joint fit quality make more of a difference than the surface. If it's built under tension, it'll spring to whatever shape suits it best when released, especially using really light balsa.

Flattest wing I ever built was a scratch built Flite Streak, using the original plans and built up leading edge. I built it in my hands. Held a piece in place, hit it with thin CA, and so on. Everything was going great until one of the trailing edge pieces went on. Was crooked as all get out. Cut it off, found a better piece, all was straight again.

So, flat is what it's supposed to be when you go fly the thing. What it is inbetween, may vary. Care during wood selection, cutting, gluing, (edit: sanding) covering and painting is what's required. A warped surface is only a problem is you don't realize it's warped (or cupped, or bowed). You can easily get around the problem during construction by checking the progress of the wing (string stretched between ends, straight edges, winding sticks, etc).

I build wings in a homemade jig. It isn't perfect but close. I figure that when you take the wing out of the jig, it is going to tweak itself a little due to built in stresses. Hence my theory. If it is perfect in the jig it can only get out of alignment when you remove it. If the jig isn't perfect, it has a 50/50 chance of getting better when you take it out! I do check alignment after assembling the wing and fuselage using a height guage at center and tips, then spray with water to make any corrections needed before covering.