Building New Stabilizer

 With the Elevators welded I started on the Stabilizer.  I've been slowly working on it but haven't found time to post my progress, so this one is rather long.

The first step was to form the 1/2" Leading Edge tube.  The fixture only does one half at a time so there is a long end sticking out.

I had previously made blocks which lifted all the lengthwise tubes to a common plane above the plywood.  I clamped the LE tube in it's blocks and worked from the center toward the tip forming the tip bend.  I used the particle board tube bender from the first set of control surfaces.

I probably should have left the tube a little longer so it would be easier to bend.  I only left about 4" extra on each end so I used the reverse bender I made for the elevators.  It worked fine.

The other end just has to be done more carefully to assure both tip bends are in the same plane.

My old particle board bender died.  I should have used hard wood for the bending surfaces with a plywood connector.  It lasted longer than I expected.

To prevent the tube twisting I supported the end with one of my roller stands.  In the end I only had about 1/8" twist so it worked fine.

The ends of the spar tubes get flattened to fit the 1/2" LE tube.  If the shape were perfect each of the flattened ends are about 0.14" wider than the 1" tube.  On the rear spar the aft ends need to be in a straight line so I use a conduit bender to bend the forward about 3/16" before flattening.

It just takes a small nudge to bend the last 6" of the spar.  You have to be careful that the 2 bends are in the same plane.

With a leather mallet and some clamping blocks it's pretty easy to form the ends flat.

After forming a cut the end roughly to shape on the band saw, what a pain with a 10' piece of tubing.

The bend worked so the trailing edge of the spar in very straight.

I used a 1/2" round file to fit the LE into the flattened spar end.

Same process for the forward spar except it doesn't need to be bent before flattening.

After I cut it to shape I tweaked the flattening with my vice grips by doing it in very small steps.

When I did the second ends I got much smarter and cut the ends to shape, after flattening, using my hand held jig saw.  I used the finest blade I had, looks like about 32 teeth per inch.  I had the spars clamped in their blocks and it worked great, much better plan.

I found it easier to cut with the panel beneath the cut removed for good blade clearance.

Once the lengthwise tubes were done and clamped in place the next step was forming the ribs from 5/16" tubing.  I have a forming dolly which I used making the OX-5 Exhaust Manifolds.  It's 1" in diameter so it worked great for forming the aft ends to fit the 1" rear spar tube.  I started with the end about 1/8" past the center of the dolly.

A few blows at about a 45 degree angle flattened the end and curved the underside for a nice fit to the spar.  I use a 32 ounce hammer.

It ended up with about a 30° angle on top and a nice curve on the bottom.

They set on the spar very well.

The center rib needs 2 tubes, the other positions need 4 tubes for left and right.

The next thing was shaping the curve of the ribs from the front spar forward to the LE.  I clamped one of my bending tools, from the Elevator Trailing Edge, to the assembly jig.

Then I used a piece of 1" tubing to hold the aft end square while bending the forward end of the rib, staring at t he tip.

I wanted the bend to stop before the spar.  I also wanted the tube to have about a 1/16" gap at the forward spar when fitted to the LE tube.  That way I could use the springiness of the rib tube to hold it tight at both ends while tack welding it in position.

There were enough full length ribs to make, that I made a simple guide for shaping and cutting, etc.  

After drawing the centerline, spars and LE, I clamped a socket to act as the rear spar to hold the flattened end in its natural position.

The angled line is the cut line I drew on each rib

I cut them on the bandsaw and the cleaned them to the line on the belt sander.

A Dremel 1/2" drum sander with 60 grit drums worked worked perfect for shaping the forward end to fit the LE tube.

The tip ribs were a bit more trouble but the process was about the same, just more care checking the fit after small cuts with the Dremel Tool.

Everything is ready for tack welding.  The painter tape worked to hold the ribs squeezed into position.  I also held each bottom rib tube snug with a wood shim.

Some joints were easier to weld with the jig clamped vertically to the saw horses.

Also I took off all the hole panels for good access to the joints.

I tacked the spars to the LE tube then tacked the ends of each rib.  Then I repositioned the tape before tacking the ribs to the forward spar.  I didn't want to burn of even melt the tape.

You can see here where I moved the tape to for welding the spar/ribs.

Other end all ready to tack weld.

When I formed the second end of the LE tube I marked where it was supposed to fit to the rear spar.  Now that the first half is welded and the second half fitted the LE is right where it was planned to be.

The clamp is pulling the LE tube tight against the spar, removing the tiniest gap.

Back in the tent tack welding the second half.

There's a lot of welding to do on the stabilizer.  In between nice weather for welding I'm making the inboard retainers/bearings for where the elevators are attached to the stabilizer.  They also attach the stabilizer to the tail post of the fuselage.

They are bent around an aluminum form block with a 5 degree spring back angle.

The spring back angle worked.  The bens are nice and square.

The right, aft, end of the piece gets a 5/8" long piece of 1-1/8" tubing welded between the bent tabs.  The left, forward, end get cut off with a hole saw to fit over the 1" rear stabilizer spar, then welded.  I made a holding block for the sawing operation by sawing 2 slots in the end for a tight fit of the bracket legs.  I also whittled the inside corner to fit the bend radius.  Then I drilled the 1/4" guide hole for the 1" hole saw.

I used a 1/4" punch to help position the hole in fitting withe the hole in the wood and tapped to fitting tightly into the slots

The hole saw worked as planned and we have 2 fittings ready for welding.

To weld to tube and bracket together I modified the saw fixture.  I sawed a 1-1/8" hole about 5/16" deep to hold the piece of tubing.

A bolt, washers and wing nut were used to hold everything tight.

I was able to get 3 tack welds on each bracket without burning up the fixture.  The inside and outside edges of the tube were then welded to the bracket.  The folded tabs get welded to the piece of tubing once they are welded to the spar of the stabilizer.  We want the tubes as close as we can get them parallel to the spar.

Now I've got the center and outboard bearings to form.