Finishing the Practice Rudder

Time to tackle the remaining stiffeners, gussets, and finish the practice rudder.  The strengtheners are not made with tube, but rather aluminum sheet.  The first step was to measure and cut the spare sheet.  I measured out a piece 21" in length, with a 1.5 inch end and the other end at 2 inches.  These dimensions allowed for a clean 0.5" bend along the lengths of each side, as one end connects to the 0.5" rudder tube and the other connects to the 1" spar.

Once cut, a little work to re-straighten the sheet as the cutting with the snips produced a slight curve and the piece was laid out to make sure the sizing was correct.

 

After that, I used a sharpie to trace out the 0.5" flaps for the bend.

 

 

Next, the piece is deburred and smoothed.  Then, using a step drill I drilled out the slot for the 0.5" rudder tube.  The slot was cleaned with snips and then smoothed and deburred.

 

 

After that, I used a 1" hole saw in the drill press to create the slot for the spar.

 

 

Once done, the rough hole (below) was turned into a slot with tin snips and smoothed and deburred.

 



 

The piece was then trial fit with the rudder before bending the 0.5" side tabs.  At this point, the protective plastic is still on the sheet and will be taken off once the bends are complete.

 



 

Off to the trusty Harbor Freight sheet metal brake.  The first tab was bent up about 90 degrees.  The second side was bent in the same direction, but because of the first bend I couldn't get fully to 90 degrees.  A few taps with the rubber mallet along the length of the stiffener brought it to the final 90 degree angle.

 

 

Once bent, the piece is trial fit and it sits snuggly in place. After that, the plastic was removed and piece was run through the sander to smooth and debur all the edges.  The tabs along the rudder edge was trimmed with the sander to match the curve of the rudder and make a smooth connection.

 











Next, the rivet holes were drilled, deburred, and held in place with clecos.

 

The rudder was flipped over on the edge of the workbench, clecos in place, and the rivet holes on the opposite side were drilled, then cleaned and deburred.

 

 

Once riveted in place, the strengthener looks good!  A few taps with the rubber mallet on the tabs makes them flush.

 





Time to do it all over again on the bottom strengthener!  Following the same process, it took about one third the time the first one did.

 

Now, the structure of the rudder is finally complete.

 

 



The next step was the final gussets for the top and the middle of the spar.  Using the sheet and snips again, the gussets were cut out, trimmed, and smoothed.

 

 

 

Next, due to the angular difference between the 0.5" rudder tube and the 1" spar, I used the metal brake to bend two bends at about 15 degrees in the gusset plates so they would sit flush when riveted.

 

 

This idea was not in the plans, but rather courtesy of my dad, an A&P.  From the look and feel of it, the gussets are just as strong and the rivets are nice and flush.  Holes for the rivets are drilled out and deburrednext.

 



 



Then, the gusset is riveted in place.

 

 

The rivets look good.  After this side was finished, the process was repeated on the opposite side.

 

 

I like the additional bends in the gussets, they look quite strong, despite the "slot" connection with the rudder tube that will be changed to a better design in the final rudder.

 

 

Next, on to the gussets for the middle tube.

 

I used the same process here, including the bends to allow for the size difference in the spar and the tube.

One side is riveted in, then flipped over for the other side.

Here is the final rudder before cleaning and priming.

And here it is!

Finally, the rudder is cleaned with M.E.K. thoroughly to remove and any gunk, sharpie marks, or any other debris accumulated through the process of constructing the rudder.  Lastly, a coat of self-etching primer and the practice rudder is finally done.

What do you think?

Planning Time = 2.5 hours









Installing the wood dowels

The plans call for a "wood dowel" to be inserted in the rudder frame at the bottom joint with the spar, and the middle support tube.  The kit did not include dowels or screws, so I went to the local Lowes and bought a pack of #6 x 1" stainless steel countersunk screws and a 7/16 wood dowel.

I should have done this step before riveting the frame to the top of the spar, because a good deal of bending was required to re-fit the dowels in the joints.

First, I shaved a little off the diameter of the dowel so it would fit snugly into the tube.  Then, I cut two 1 and 3/4" lengths of the shaved-down 7/16 dowel.  I used a #45 drill bit to drill a 1 inch guide hole for the screws in the top of both dowels.

 

I then countersunk the 1/8"hole on the front of the spar so the screw would sit relatively flush.

 



Next, I screwed the dowel in tight and fit the frame tube over the dowel.

 

The tube fit around the dowel snuggly and is quite firm in its place.  It is not riveted or screwed directly into the spar and, right now, is held in by the surface tension of the dowel, but I assume the final covering will hold it tight in its slot.

Repeated the same step on the middle support and am done for the night.  Again, I should have done this step before riveting the tube frame into the top of the spar.  I'll do the real rudder in that order.

Planning time = .5 Hours

Well, that didn't work as expected.

After the work last night and posting the pictures, a builder with obviously more knowledge than me said "I believe  you may have overlooked a major issue related to bending the tempered aluminum tubing - spring back.  It is impossible to form the tubing over an exact pattern. The tubing must be bent well past the desired shape, held for a few seconds for a "set", then allowed to spring back."

Whoops.

So much for the "quick, easy, and rewarding" promise from the kit manufacturer about the build. It seems to me that you need quite a significant about of metal-working experience and engineering training.  That I don't have.  The problem is the instructions are not as detailed as hoped and have some "there are several way to do this and no one right way" statements.  Now, I don't want to seem like I am degrading the manufacturer because, by all accounts and brief personal experience, he is responsive and will talk things over on the phone.  However, the thousands of calls I envision for every bend have me embarrassed, so I'm trying to not call him whenever possible.

Long story short, as much as I desperately want to do this project, I'm starting to have thoughts that I don't have the engineering qualifications required for this project.  I can drill and clean holes, rivet sheet, safety-wire bolts, and many other things related to aircraft.  But, there is a lot more fabrication in this project than expected.

Still, I'm pushing forward with the practice rudder.  I gradually formed the rudder frame with a small series of had bends outside the form.  Below are the pictures of the work done tonight.  I'm not all that happy with the work, as I want something that will carry me in the air to be built as precise as possible.  Ironically, the advice I keep getting is from builders telling me to not worry:

"This is not an F18, so do not drive yourself crazy with minute precision"
"We are building airplanes....not heart valves"
"Perfection is the enemy of completion"
"Airplanes, and in particular AA aircraft, are simple (crude?) machines
where precision is only required in a few areas"
"Keep it simple light and strong 'enough' !"
And my favorite:"you're building an aeroplane......not a pocket watch! "

I get it, I really do.  Micrometer precision on metal bends aren't practical.  However, when you have an office job and no formal A&P or engineering training, I have no real idea of what mistakes are safe to work with and what ones compromise safety (in some instances). That makes me paranoid, especially without step-by-step instructions.

That said, here are tonight's pictures from the practice rudder build.  Please comment and be critical if you see something wrong.  I need it.

The final rudder frame, not a precise as I wanted.

Marking the rudder spar for cutting

Using the marks to drill a 1/2" hole for the rudder frame slot

Testing the hole with a 1/2" drill bit after using a step-bit to drill the hold and deburring it.

Cut along the line, which turned out to cause problems

Here is that problem demonstrated with a 1/2" drill bit:  the walls of the slot don't go up high enough to attach a rivet.

Used the tube notcher to drill out the hole deeper to give more metal area on the sides for rivets.

Test fit works, so the spar then went to the sander to smooth and debur before drilling and riveting.

Used a rubber mallet to hammer the sides flush against the rudder frame.

After the test fit, the spar and the frame are marked and drilled with a #30 bit for the rivets.

The finished rivets.  Not too happy with the finish (the term "wonky" comes to mind).

My biggest concern:  the structural integrity of the rivets with the gap in between the frame tube and the spar walls. Of all these photos, this is the one I REALLY want comments on.

The bottom of the spar was drilled as instructed with a #30 hole in the forward side and a 1/2" hole on the rear for the rudder frame.



The fit was nice and tight after trimming the rudder frame.

This is the fit inside the spar.  The plans call for screwing into wooden dowels placed inside the rudder frame tube.  I'm not really understanding that part, and there were no dowels in the kit.  PLEASE HELP!  What do I do here?



Next, the same #30 in the front and 1/2" hole on the rear for the middle support strut/tube/whatever it is called...



Test fit looks good after notching the end of the strut, deburring, and sanding the cuts.

Next, cutting and fabricating the gussets for the left and right of the support strut.  These were mage with 0.032 sheet, marked and trimmed to match the curve of the rudder. Made two, one for each side.

The finished and riveted gusset for the middle support strut.

Top view of the riveted gussets.

The other side...

Finally, where I stopped tonight. I need some help understanding exactly how the middle and bottom tubes are to be attached to the spar, so that is the next step.

 Well, there it is.  It seems to be coming together, but I am really having doubts about my ability to finish this.  Comment and tell me what you think.

Planning time = 2.5 hours
(again, this is the practice rudder)