Gettin? Jiggy!

Ironflight · #1 11-03-2009, 08:15 PM

I have been mildly dreading this moment ? building the fuselage jig for the RV-3 ? but not for the reason you might think. I really wasn?t too worried about the actual building (although how you get wood that won?t warp, and build the thing with real precision that?s good enough for an airplane were troubling mysteries?), I was just not looking forward to finding all of my carpentry tools (never unpacked since last year?s move?) and digging through the mountains of stuff piled on my radial arm and table saws!

Actually, building the jig was sort of enjoyable. Precision is taken care of by ?mass producing? identical parts, like the ?ladder? rungs ? seven pieces all identical in length. Set up the saw for each type of part and make them all at once. It sure makes it easier to square things up that way. Louise went with me to Lowes to pick out the wood the day before ? it is much easier to sort through a pile of sixteen foot 2x8?s looking for two perfect ones when you have a partner, believe me! Materials for the jig ran about $150. If you consider I put about 8 man-hours into the job, that?s a reasonable price to pay for shop-related entertainment?..

You can find some photos of the ?build? at this link?

http://picasaweb.google.com/Ironflig...V3FuselageJig#

?.and here are a few notes and random thoughts from along the way:

1) Take care to cut everything very square (a radial arm saw is perfect for this), and alignment during construction almost takes care of itself.
2) I was not surprised o find out that my garage floor with neither flat nor level ? I went on faith that the two side-rails were straight enough to act as ?keels? to keep the jig true.
3) I cut two lengths of cross-bars, 21? and 24?. The 21?s went between the side rails, the 24?s on top to form the ?bed? where the longerons will rest. Since every piece that went between the cross-bars were the same length, I knew that they would be aligned.
4) As is typical of Van?s clever drawings, read them very, very carefully. The datum for each crossbar is given on the drawing, and is the FORWARD edge of edge cross bar ? for all but ONE of them. One of them is a measurement to the AFT edge. Don?t ask me why?.just re-do it when you do it wrong.
5) Galvanized angles are great for bracing the ?bed? crossbars, and making sure they are vertical. Using ?? plywood for the triangular braces, and sandwiching the ?bed? crossbars between the triangles and the braces, you can leave the ?bed? parts loose until you are doing final alignment. You can then slide shims under from the side to bring all the ?bed? cross-bars into alignment. Don?t fasten them down until you get it into final position.
6) I have not yet fastened the jig to the floor, and right now, and considering not doing so. It is heavy enough to be very stable, and my hangar floor appears to be very level. Unless/Until it shows signs of warping, I am not sure that it is going to have to be drilled in. I?ll let it set for a week and see if it changes shape.
7) I used a couple of 19? 2x4?s nailed in between the two uprights of the firewall supports to brace them for attaching to the front of the jig ? this made it very easy to assemble. I might just leave them there until I find that they are in the way.
8) The diagonal braces that run from the side rails to the bottoms of the firewall supports are shown as bowing outward from the narrower side rails to the wider firewall supports. I didn?t like this, and used one inch plywood to make the side rails wider where the diagonals attached. Much cleaner!
9) I elected to go with 2x8?s instead of the 2x6?s shown on the plans ? just seemed more rigid to me! You need 13-foot lengths, so will have to 16 footers, unless you have a very odd lumber yard nearby.
10) A package of cedar shims is rally handy to bring everything into final alignment.

Now I can?t wait for Louise and I to start assembling actual aluminum pieces!

Paul

scsmith · #2 11-04-2009, 01:25 AM

A nifty material to use for jig side rails, is an engineered wood product called "LVL", which I think stands for laminated veneer lumber. It comes in 1.75" x 11". Carpenters will often rip them in half and join them face to face to make 4x6 headers over sliding patio doors. ( a 4x6 is 3.5" x 5.5") This stuff is VERY STABLE and STRAIGHT. It is kind of pricey, but if you want a jig that won't change shape with time or humidity changes, this is the stuff to use.

Michael White · #3 11-04-2009, 05:03 AM

Paul,
You forgot the most important part:

Quote:

"Before we use any power tools, let's talk about Shop Safety. Be sure to read, understand and follow all the safety rules that come with you power equipment. Knowing how to use your power tools safely will greatly reduce the chance of injury. And remember, the most important safety rule is to wear these, safety glasses." Norm Abrahm

And yes, I know that one by heart. Norm is my idol...

It looks great!

rvaitor87 · #4 11-04-2009, 07:52 AM

Paul;

Been there, Done that!

If your jig is straight, then your fuse will be too! May your parts fall into place

Mike Bauer
Bartow, Florida

RV-3 Flying
RV-4 building

Ted Johns · #5 11-04-2009, 09:11 AM

Steve Smith has it right, if you want lumber that will stay straight go with LVL or one of it's "engineered wood" cousins, like LSL or OSL. For smaller jigs, plywood is typically used. For example, to make a strong straight 2x4, rip two pieces of 3/4 inch plywood to 3.5 inches and glue together.

To check if your side rails are straight, use a string line. Looks to me like the bottom edge is clear.

Those side pieces in the picture have plenty of face grain and plenty of sap wood. Unless they were kiln dried they are already warping, it's just a matter of how much. If they are kiln dried, they will warp as they react to humidity changes.

If they do dry straight enough for your purposes, or can be secured to the hanger floor in a straight condition, use a good grade of shellac (like Zinsser)to keep them that way. Shellac is a great water barrier, and is easy to apply. Coat everything, and the jig will move around a lot less in the years to come.

If they were not kiln dried, they will be drying and changing for months. I'd wait several months at least before shellacing the jig.

Making a wood object stay straight in a hanger for years is probably harder than building an airplane.

rv7boy · #6 11-04-2009, 10:26 AM

Paul, your RV-3 jig reminds me of the "early days" when there were several RV-6's being built around here. I got interested in RV's at the '93 Sun'n Fun and when I returned home (North Alabama) I discovered there were several RV's being built close to me. One builder actually worked one floor above me here at MSFC.

I don't remember who built the first fuselage jig, but it was good enough to be passed on to 5 or 6 builders. Then the pre-punched kits came out, and there was no more need for the fuselage jig, or empennage jig for that matter.

Maybe Doug would like your fuselage jig when he gets to that point. Hey Doug, how's the RV-3 coming along???

longranger · #7 11-04-2009, 02:44 PM

How much more epensive would a steel jig be, assuming you could do the welding, or trade favors with someone who could? You certainly wouldn't have to worry about humidity changes.

Ironflight · #8 11-04-2009, 02:59 PM

I would have loved to build a steel jig, but welding is one skill I have never had time to pick up....I had all sorts of thoughts about building a metal "be-all, end-all" jig, but in the end, decided I wanted a fuselage, not a jig, so went with Van's tried-and-true.

Paul

Louise Hose · #9 11-04-2009, 03:53 PM

Quote:

Originally Posted by Ted Johns

Making a wood object stay straight in a hanger for years is probably harder than building an airplane.

You think that Paul would allow me/us to take "years" to get the fuselage far enough along to take off the jig?

He's far to strict of a task master to allow such dallying!

For that matter, after flying the -8, I can't wait to finish up Junior and fly "our" -3. I'm excited to get home from my business trip tomorrow and start working on the fuse!

Ted Johns · #10 11-04-2009, 04:26 PM

Quote:

Originally Posted by Louise Hose

You think that Paul would allow me/us to take "years" to get the fuselage far enough along to take off the jig?

He's far to strict of a task master to allow such dallying!

For that matter, after flying the -8, I can't wait to finish up Junior and fly "our" -3. I'm excited to get home from my business trip tomorrow and start working on the fuse!

I wish my wife would build an airplane for me. I'm so jealous!

Quote:

How much more expensive would a steel jig be, assuming you could do the welding...

Probably 2 to 3 times, depending on how carried away you got with the gauge of steel. LVL lumber is about 1.5X regular stuff, so that factors into the comparison. Steel would be the obvious choice for a factory, but I think LVL would be plenty good for home use.