BUILDING THE HORIZONTAL STABILIZER

 

 

Initiating the H.S. construction Wheels added to the workbench

Actual assembly work started on May 27, more than one month after the kit was ordered.  Just before work started I decided to add wheels to the work bench (RH photo).  This was a good mod.  I need to be able to move this thing around.  It is very solid but very heavy.

 

H.S. drawing and plans book on bench

H.S. rear spar drilling process

The Home Depot work bench serves as a drawing holder for now (LH photo above).  Horizontal stabilizer rear spar is in process of being drilled and re-enforcements added (RH photo above). 

Outboard Elevator hinge bracket

Inboard Elevator hinge bracket

 

Elevator hinge brackets are being installed at this point.  I used alignment pins to keep elevator attach holes in alignment during the drilling process. The two pictures above show the process.

 

Front spar re-enforcement

 

 

Forward horizontal stabilizer spar re-enforcements are trimmed per the drawing (photo above left).  Here they are installed and drilled to spar.    The left photo also shows a yellow clamp.  These are very cheap at Lowes (where I live most of the time) and are handy.  The right photo above shows both horizontal stabilizer spars in initial stages of assembly preparation.  Also in the right photo you can see at the bottom of the workbench, the water-trap, filter and regulator for the air supply.  These are available at, where else, Lowes.

 

H.S. structure taking shape

Wooden assembly spacer beneath rear spar

 

Here, in the photos above, you can see the Horizontal Stabilizer “skeleton” is starting to take shape.  All of these computer punch press installed holes really do line up.  I have been involved in aircraft sheet metal for many years and any time a part came with “pilot holes” it was always a problem.  These holes never lined up and instead of speeding up repairs they in fact slowed things down.  I was really skeptical about pre-drilled parts but I am being turned around as we speak.   Notice the wood beneath the rear spar.  I cut a 2 X 4 to fit inside the rear spar.  The horizontal stabilizer skin extends past the spar and this spacer allows the installation of the skin in a vertical position.

 

LH H.S. skin installation

LH H.S. stabilizer skin bottom side

Here the  LH horizontal stabilizer skin is in process of being installed (two photos above).  The holes are still at pilot hole size for now.  There is a dimension of 12 & 3/16 inch from the forward spar to the rear spar in the center section area.  The 2 blocks of wood were cut to this dimension.  Prior to drilling the inboard ribs (which have no pilot holes) these blocks of wood were inserted between the two spars.  Since the left skin is now drilled to these two ribs (HS-404 and HS-405) this block of wood is being used to protect rear spar from the clamp that holds the assembly to the table.

H.S. cleco'd together

Another view of H.S.

 

At this point (above) the right skin is installed.  The horizontal stabilizer is now ready to have the holes upsized and dimpled.  Then all the parts will be etched, alodined, and primed.  This was a good time to clean off the workbench and put all of the tools back where they belong.  If you don’t do this occasionally the garage gets back to looking like it did before this project was started.

 

Wooden spacer block.

Close-up of wooden spacer block.

 

It is time to disassemble, de-burr, etch, alodine and prime the parts. The left photo above shows the block of wood that was placed under the spar for support.  A close up at right shows that there are several holes drilled in the wood.  These are ¼” in diameter and are in line with the skin to rear spar holes.  These holes allow the clecos in the skin to be installed with the wood in place.  With this wood in place I could clamp the rear spar to the table cleco the skeleton together and then cleco the skins to the skeleton in a vertical position (Inset).  This is the method I used to help keep the H.S. square and un-twisted.  The work bench is very solid because I used expensive finish plywood, 5/8" thick, for the top.  (You will never guess it but this plywood is available at Lowes.  Stop in sometime.  I think they are ready to give me my own office.)

 

Prior to de-burring the holes and edges of the Horizontal Stabilizer parts, I decided to modify the two P/N HS-707 nose ribs.  During the pre-assembly, I noticed that these ribs were pushing on the leading edge of the skins hard enough to form a bulge.  It also was nearly impossible to put the very top cleco in the hole without putting a decent amount of side pressure on an alignment tool in the hole beneath the top hole. It is my  opinion that this condition would load up the skin and these ribs to the point that cracks may develop.  The problem was only at the leading edge.

 

Other than the leading edge area these ribs fit like a pair of special made gloves.  The rib on the right in the photo is shown prior to modification.  The rib on the left has been modified.  I left the web of the rib intact.  I removed only the very last 3/8”, leaving adequate edge distance on the hole in the flange.  Interestingly enough, there was no fastener hole in the area that I removed, nor was there a callout on the drawing for one.

 

All of the ribs in the horizontal stabilizer are de-burred and dimpled at this point.

LH horizontal stabilizer skin at start of dimpling process with the "C" frame.

Another picture of the “C” Frame with the platform.

A close up of the “C” frame at work.

 

The  dimpling process takes longer than I thought it would.  The ribs are a snap because I used a pneumatic squeeze tool.  The photo above left shows the dimpled ribs. The skins took much longer however because each hole had to be set up separately.  Also the “C” Frame Dimple tool (RH picture) would not work near the leading edge. 

 

Pop rivet dimple tool in use.

A close up look at the pop rivet dimple dies.

At this point a “Pop Rivet Tool” dimple die had to be used.  My able assistant is holding the tool in the left  photo above (She was not dressed for pictures and threatened me if I showed her in the picture, so I show only her hand.)  The right photo shows the dies close up. This dimple process is not fast but it sure beats using a pneumatic rivet gun with dimple dies and bucking bar.  It is a 2 step process.  For some reason they supply a pin of the appropriate diameter made from brass.  You put a slight dimple in the metal with this pin then you remove the pin and finish the dimple with a hardware store nail.  It makes a perfect dimple every time and is invaluable in places that are inaccessible.  After a while, I realized that if you were careful to hold the male dimple die centered on the hole, you could skip using the brass pin which saves some time.

Horizontal stabilizer parts during priming process.

Paint booth filter after use.

 

After the holes were all dimpled (8 hours later but I got much faster with experience), I etched and alodined all of the parts with DuPont 225 and 226.  This is a 2 part system, etch and alodine.   I am going through this process to clean the metal in preparation for primer instead of as a needed treatment that aluminum that is bare (no Alclad) has to have for corrosion protection.  These parts are almost all alclad and priming is optional.  I went into more detail as to why I am priming in a different section of this log.  The photos directly above show the priming in progress.  The paint booth worked pretty well but a little paint got completely through.  I have to use even better filter material or I have to figure out how to put more filter material on the booth.  There will be an update in the "Paint Booth" section concerning the filter.  The RH photo shows that the filter did stop a lot of paint.   I let the parts dry overnight and started the assembly on Monday, June 3rd.

 

Horizontal Stabilizer Ready for assembly.

Inner structure (skeleton) during assembly.

HS-707 and HS-708 ribs attached to spar.

LH H.S. skin installed and partially riveted.

 

The horizontal stabilizer assembly has begun in these 4 pictures above.  It is a very straight forward process.  I deviated from the plans in three areas.  The first area was the assembly sequence.  The plans had you rivet the HS-707 rib to the skin on each side first.  I decided to attach the ribs to the forward spar first.  Next the plans called out to attach the HS-707 rib and skin assemblies to the forward spar along with the HS-708 rib using “pop” rivets.  I elected to use AN470AD solid rivets instead.  Last but not least, the plans called out to rivet the HS-707 ribs to the rear spar after skins were attached to everything but the rear spar using more “pop” rivets.  I left the inboard ribs out and was able to rivet these 2 ribs to the rear spar using AN470AD4 rivets.  Had I not been able to do that I would have used aircraft quality blind rivets on the HS-708 to HS-603PP rear spar attach.

 

LH H.S. skin riveted in place

RH H.S. skin cleco'd in place

 

The left photo shows the left horizontal stabilizer skin attached and the next step is to install the right skin.  It is apparent that the rivets from the HS-707 rib to the outboard end of the skin have not been installed yet.  The rear spar had to be removed to install these rivets so I decided to save these and do both sides at once.  The right photo above shows the RH skin cleco'd in place on the top.  I installed all of the rivets in one side of the skin before I cleco'd the other side in place.  This allowed me to rivet the assembly together by myself.  If you decide to install rivets un-assisted, practice on some scrap.  If you slip with the rivet gun, you will be very disappointed.

 

H.S. with all fwd spar rivets on top side installed.

H.S. with rear spar removed and hinges brackets installed.

 

At the point the left photo above was taken, I installed the HS-404 forward inboard ribs on each side.  I then removed the rear spar and installed the remaining rivets in the forward spar prior to the RH photo being taken.  I then installed the elevator hinge brackets to the spar except for the center one.

 

HS-708  attached to rear spar with solid rivets.

HS-708  attached to rear spar with solid rivets.

 

The upper left photo shows the HS-708 rib.  I left a row of fasteners out of the skin to rear spar attachment in order to have just a little extra room to put my arm in here with a bucking bar.  Photo on the right shows the rivets are all the same type in the rear spar re-enforcements.  I do not like “pop” rivets and I even avoid aircraft quality blind rivets if I can.

 

H.S. complete except for center hinge and tip caps.

H.S. in cradle.

 

On Friday June 7, I primed the bearing holder for the center hinge bearing P/N VA-146 and I installed it into the brackets P/N HS-411BPP. I installed this assembly onto the rear spar with 4 AN3 bolts per the plans.  I made a storage cradle for the stabilizer out of wood.  Everything is finished on the horizontal stabilizer except for the fiberglass tips.  I will do all of the empennage fiberglass tips at the same time when all of the aluminum parts are complete.  The Vertical Stabilizer is next.