With both the wings into going into storage, I added the fuel tank drain/test ports.  I need to make sure that nothing can get into the tanks while they sit in storage, and the any openings on the wings, like the lightening holes at the root have been covered up with tape and plastic to prevent bird or mouse nests!

First time in a very long time the bench has been completely clear of wing stuff!  Time to start laying out the fuselage skins.

Had a couple of minutes one afternoon after work to finish one of the horizontal tail fuselage bulkhead frames need for the fuselage:

The plans are a bit deceiving when looking at the them when scaled down from full size.  Close attention shows that the four corners of the fuselage aren't actually directly straight - the fuselage tapers very gently from the back of the cabin to the tail along all four longeron corners.

I've been pondering this for a while and when I was at the Zenair factory in Midland buying my longerons last month, I asked Nicholas Heintz (Chris' son) what would be an acceptable way for a scratchbuilder like me to make the correct tapered curve of the skins (the longerons curve to match the skins and are pre-cut in the kit versions).

Nicholas said the taper is very subtle and I should just connect the measured points out from the centre-line as shown in the plans.  As long as the taper is equal on both sides of each of the four fuselage skins, all would be acceptable, but the taper is important as it provides some longitudinal rigidity to the fuselage..

Apparently that's not good enough for me!  I wasn't confident that each 500mm point would give me enough points close enough together to draw through to make the gentle curve.  So I grabbed the plans and entered them into CAD, like a lot of the templates I've made.

CAD has a great "spline" tool that is like using a draughtsman's French curve ruler to average out the points in the plans to establish a smooth curve. Then I used tools within CAD to section each of the 500mm sections on the plans into 100mm smaller sections, then measured where the points along the curve so I could transfer this onto the aluminum.  Enough points along this curve means I can connect them with a real French curve ruler and have my taper drawn correctly on the aluminum sheet.

Here is a snapshot of the fuselage bottom skin, half way through the sectioning process in CAD:  

The fuselage skins are all 0.020 thick, with several doublers between the longerons laterally and diagonally to stiffen everything up.  The bottom skin is laid out on the table and I used the long straight edge to draw the centreline from which the edge points will be measured:

I measured out each of the sections lines along the centre-line, then used a square aligned with the long straightedge to plot the section lines out the edge of where the skin will be.  I soon realized that Nicholas was probably right, curves based on the 500mm sections would probably be enough, so I decided to divide the sections into 250mm sections instead.  This is a good compromise and accurate enough for me to make the taper correct using the French curve ruler we have.

This picture shows the lateral lines drawn out from the centre - the circles are where the curve of the edge of the skin will be and the lines from circle to circle are the skin edges which will be trimmed later.  From there, I laid out the lower hatch door opening (often called the hell-hole) and some of the other lateral lines for the stiffeners, diagonal "L's" and torque tube bearing channel (supports the control torque tube): 

A 10mm line scribed inboard from the edge skin is the rivet line where the skin will be fastened to the longeron once the skin sides are trimmed.  This picture is the tail end of the lower fuse skin.

The lower fuse skin is actually too long to fit on a full 12 foot sheet of aluminum, even if I "tilt" the lower skin outline on the sheet, so a lower rear skin is added - it becomes part of the horizontal tail "box" and further strengthens this part of the fuselage to support the tail structure.  Aligning it on the centre-line at the proper location ensures the lower skin is the correct length from the cabin to the rudder supports.  Here it is temporarily clecoed in place:

Z-channels are added around the sides and rear of the lower hatch.  These still need to be trimmed, I just wanted a rough idea where/how they interact with each other and how the rivet spacing should lay out.  The square of cardstock is a quick cut out for me to use to visuallize where the flap motor will mount - again for rivet spacing, etc.:

Cutting out the access hatch was fairly easy.  I used the fly-cutter to shape out the corners: 

Then connected the edges of the circles and cut out the hatch.  Some filing and sanding to take care of some rough edges and the access hole is done. I'll make the hatch cover from some of the left over 020 of the top skin.

 
I finished (for now) the bottom skin.  All the rivet lines are laid out and drilled.  Before I cut the bottom skin out, I've rolled it back up as as full 12x4 full sheet.  Much easier to store.

Returning to CAD, I sketched out the two side skins and the top skin - this time with 250mm sections.  It worked so well with the bottom skin, this will be the path to obtain the tapered curves for the other 3 sides of the fuselage (these are snapshots from CAD, not scaled together):

The top skin is somewhat shorter in length than the bottom skin, so I can comfortably "tilt" it on the aluminum sheet to save wasting some of the sheet.

Same layout method as the bottom skin.  This skin has a flanged hole near the tail - this is where the elevator control cables will pass through the fuselage into the vertical tail assembly.  Cut it out using the fly-cutter.  I'll flange it later once the skin out cut out form the sheet so I can clamp the flanging dies easier (can't reach the hole now):

A second hole is cut near the tail end.  This will form the round end of the channel as laid out by the lines drawn rearward from the circle to the rear skin edge:

Now onto the part that has been keeping me up at night.

We don't have the ability to bend complex shapes such as the upper top channel shown below.  It's a slightly leaning C shaped channel, tapered at the ends that forms part of the wing spar carry-through on the top rear of the cabin.  It is made of understandably stout 063 aluminum and both the shape and dimensions are critical to ensuring the wings mate to the fuselage at the right angle and location.  So I ordered this from Zenith and picked it up the same day as the longerons.

Problem is, I hadn't thought it through and asked them to provide the channel pre-drilled, as they would in a kit.  What I didn't consider is how to transfer the holes to the cover channel and doubler that make up the other sides of the top channel to form the spar carry though box.

I could order those pieces too, but when I spoke with them, they couldn't guarantee they the holes in the other 2 parts would be an exact match to mine as they drill them together at the time of manufacture, and mine was a one-of ordered part.

What to do.  Start looking at order of operations and see if I can match drill the holes somehow, while respecting the bends yet to be made in the other two parts.

I can access some of the holes at the end of the top channel where it is cut diagonally to match the cabin uprights, so I placed the top channel in the proper position of on the top skin, drilled/clecoed the accessible holes form above into the skin.  With that done and the channel secured to the skin in the right location I then duplicated the remainng holes along the bottom of the channel (actually the top when the skin is in place) onto the top skin because I can use the strap duplicator before the other pieces are added and drill from below the table level:

Unfortunately, as well as that worked, several of the holes on the channel are the bigger A6 river size rather than the standard A5 in the rest of the channel.  Here is the channel lying on it's back.  The 5 holes grouped close together are the ones I'm taking about.  I don't know if an A6 duplicator is available, but we don't have one.  These A6 holes are not accessible from inside the  channel either.

Time to get creative.

I bent a matching piece of 016 to fit inside the channel and long enough to cover both the A6 holes, two inboard A5 and the A5 hole outboard holes and clamped it in place:

Back drilling through the channel into the 016 (using clecos in the three A5 holes to hold it together straight) and A6 size in the other holes gave me an excellent template to transfer to the skin that will match the channel holes:

Template added to skin, secured with clecos in the existing A5 holes, then A6 holes drilled through the skin:

I added more holes in the template from the forward facing A6 holes so once I have the doubler and channel angle bent, it too can be duplicated without having the access from inside the channel:

Fabricated and drilled the upper baggage area rear panel support angle to the upper skin:

​This angle won't change once needed, so I finished all the river holes, deburred it and put it back into storage.

Next up was fitting and predrilling the upper fuselage top doublers.  These doublers are almost like the shoulder blades of the wing/fuselage junction which transfers the loads back over the fuselage longerons and upper skin.

First I lined them up on the top skin and used extended lines from the top channel holes and the longeron rivet lines.  Once in place, I traced those same river lines onto the doubler and laid out the rivet locations as per the plan.  The doubler actually fits onto the outside of the fuselage, but laying it out this way allows me to see the lines before drilling through the doubler and the skin.

Once I was satisfied with the layout, I drilled pilot holes in the doubler on the drill press in the require locations, but not where the top channel lays.  Then I back drilled through the doubler in 5 locations to secure it to the skin. The rest I'll drill once the longerons are in place:

Both doublers in place, secured enough for the next steps:

Shifted the doublers to their proper position on the outside of the fuselage skin (remember, I'm working on the inside of the skin and it's actually upside down on the table) and clecoede them in place from above.  Then I placed the top channel back in place and secured it from below using the holes duplicated earlier in the skin:

I drilled the forst A5 hole and the two A6 holes I can access at the end of the top channel, then removed the channel and marked the others through the skin and into the top skin doubler:

Removing the top doubler and finishing the holes on the drill press, proves the matching worked (for some reason the picture below seems to show the holes are out of round, but it must be a shadow from the flash as they are actually perfectly matched):

I've also been scrounging a bit online on various marketplaces, classified listings and forums.  Scratch building makes you keen to grab deals when they come up and I've been scoring well lately.

Both Ron and I want to make epoxy resin castings for our navigation light lenses and strobes.  One of the tools needed to cast clear lenses is a vacuum chamber which is used to de-gas both the silicone molding mixture and the epoxy itself.

I spotted this complete set on Facebook from a seller not to far away.  She wanted $125 for everything but I managed to get it for $100 just by asking.  It's really brand new, she told me she'd only used it a couple of times but couldn't handle the fumes, so she was looking to sell it to someone who could use it.  I looked it up after I bought it and there is easily $400 worth of stiff here, so I was a bit surpised she was willing to sell it for so little.

I brought it to the shop and tried it.  Ah.  It's not working, that's why.

The vacuum pump appeared to be pulling lots of pressure at the end of the vacuum line, but nothing was jhappening in the pot.  Originally I thought maybe the valves were bad or something and I would have to replace them.

When I looked closer however, it looks like someone let the some casting epoxy get into the vacuum port on the pot lid, sealing it completely over!  A quick drill and clean out of the port, freed up everything and it is working like new again.  Score!  We can also use this to de-gas paint for the planes too.

On the Zenith website classifieds, I spotted a suitable airspeed and altitude indicator.  Used, but in excellent used condition, clearly taken care of by the previous owner.  $200 USD for the pair - Score!

Another Facebook marketplace find were these cable turnbuckles, cable swivels, and throttle cable.  Less than $200USD for everything - Score!

Ron continues to look for some parts for his Continental O-200 conversion for the Aeronca Scout rebuild.  He bought a Cessna 140 for the engine, but it needed a new intake spider which was cracked.

These are getting very VERY hard to find as they often get damaged during prop strikes and need replacing.  New ones are available, but cost north of $800USD!!  I spotted one on Facebook marketplace, contacted the seller and managed to get this good used one and a box of other intake parts for $100USD shipped! - Score!  I've given it to Ron as thanks for all his help with my build and his kindness in letting me use his shop.  That's the kind of karma that I believe we need more of in this world :)

I'm getting close enough now that I need to consider what I need for my Corvair engine install with regards to firewall forward stuff.

I ordered my Corvair/Zenith installation manual as well as the MOP (Maintenance and Operations Procedures) manual.

They arrived in my hands and I sat on the dock the following morning looking through them.  This build is always on my mind, even in the quiet times :)

More to come, thanks for reading along!

Been over a month since I've updated the blog, but that doesn't mean I haven't been very busy in the shop making tons of progress!

Second fuel tank went together very quickly. Using the 2 part sealant enough times now, I've become used to best methods of applying it.

Outboard side of 2nd wing tank.  Rivets on the lower seam are held in place with masking tape.  This allows me to apply the sealant bead, insert the tank wall and then squeeze the rivets in one (almost seamless) process:

With the edges closed up and rivets squeezed, another layer of sealant is applied to all outside edges and seams.  I learned from the 1st tank to make things cleaner by masking off the edges:

Waited the required 6 days after the last of the sealant was applied before leak testing the tank with water.  Like the 1st tank, a couple of small weaping leaks required some re-work of the seams and some more sealant.

While that cured (for another 6 days!), I got some work done on some of the smaller parts for the controls and fuselage.

Some of these templates are ones I created a few years ago using CAD, a PDF conversion program and then printed out on cardstock using a laser printer.

​Lots and lots of small parts from aluminum plate and aluminum sheet:

More recently, I've been using the CriCut Maker machine more as it has the ability to not only cut my templates from card stock direct from the CAD file, but I can also print on the templates as well - handy for part numbers and drawing centre marks for holes etc.

Some of the last parts I needed were from 063 aluminum sheet.

Some templates don't need to be the full length either.  For example, these flapperon control rod covers are 890mm in length, but the same width at both ends.  A short template serves dual purpose for both end cut measurements:

I laid out several of the pieces I have made for the cabin and fuselage - including seat pans upper and lower fuselage doublers and more.  Like I said, I've been very busy!  Here they are in an animation using the online gif maker Kapwing.  My animations skills won't have me working for Pixar!

With the tank sealant cured and tested again (this time no leaks!), I got it installed in the wing.  Fuel line and fuel tank wiring is done:

Wing is sealed up again:

Fuel cap and filler neck fit perfectly!  Wing is ready for storage!

Next I started final bending/fabrication on some of the parts I've been cutting out from sheet.

Seat pans require lightening holes, so I drilled those out:

Then I used the flanging dies and some large C-clamps to form the lightening holes:

Same for the seat pan supports:

Major milestone completed with both wings now complete and ready for storage.  Next, we'll get this wing into the storage barn and start the process of laying out the rear fuselage.

Thanks for following along!  More to come soon!

It has been almost a month since my last blog post, but work continued on the slats over that time.  No real need to blog about it as the process was the same for all four with the exception that the outboard slats were slightly longer externally.  The internal skeleton and assembly steps were the same.

A pciture of the last slat on the bench awaiting trailing edge bend before debur, prime and rivet.

Also in the last couple of weeks I played a bit more with the 3D printer.  It seems I've run into an issue with the filament jamming in the extruder.  Very frustrating stepping away to do other things while the printer works on something, just to come back and find nothing coming from the nozzle!

I took the extruder apart and it was clear it wasn't feeding correctly as evidenced by the "knot" of melted filament between the extruder and the hot end. 

​I spoke to a work colleague who is very invested in 3D printing as a side business and showed him some pictures.  There are two things that most commonly cause this are a gap between the hot end feeder tube and the extruder, or worn extruder parts.  As the extruder parts are 3D parts themselves from the manufacturer, his suggestion was to spend some money to upgrade to an all metal extruder and hot-end.

Looking further into this, I decided to not to proceed any further with using this printer.  The printer is not mine (it belongs to the local library) and I'm not quite ready to invest the time or money to upgrade something that is already esentially obsolete.  I still plan on printing parts for the airplane eventually, but this printer is has become a bit of a distraction from the airplane itself.  Also, newer model printers are getting cheaper by the minute and easier to use with built in functionality that makes printing exactly what I need more sense, so I'll look at investing in one of my own eventually.  I've accomplished what I set out to do - proof of concept and making it functional again for the library. 3D scanning is also functionally feasible, but it too needs more time to getting it working the way I want it so it too will be shelved for the meantime.

A question came up from another builder on the forum on how I've managed to bend the trailing edges so cleanly.  The entire procedure of assembling the slats can be seen on a previous blog post but for the sake of explanation, I used a small diameter rod along the inside of the fold held in place with some spacers Ron and I came up with.  The are scrap strips of 0.016 aluminum with a a small curled up end.

I used wide painters tape to hold the strips in place, the curl of the strip against the rod.  The picture make sit look like the curl is taller than the rod, but it is not.  If it were, it would leave a mark on the inside of the skin so caution is warranted here

Strips and tape are cheap, good to have several across the entire width of the slat skin:

Slats complete!

The inboard slats (the shorter ones) eventually tuck inside the outboard slat enough to be riveted together once they are mounted on the wings.  Here they are back to back and upside down on the bench lined up but not yet tucked together - this really gives the idea how long and wide the wings will be!

Looking at my "completed sections" drawing, I'm pleased to be "mostly done" the control surfaces.....

.... and happy to see an empty bench, even for a few minutes!  Now to begin one of the bigger sections both in size and number of parts - the WINGS!

I brought a fresh roll of 0.032 (on the bench) and 0.042 (coiled beside the bench) down from the storage barn, to start laying out the components for the wings.  Like everything else, I want all the parts made and ready to use in assembly to minimize the time on the bench.

First up, the wing spar webs from 0.032.  The two spar webs are almost a full length section of a sheet and requires accurate cutting so the spar assembly is straight and true.  They make up the centre part of the spar between to 6061-T6 angles on the top and bottom (more on later).

I cut the first web using a plunge saw with metal cutting wheel and it turned out fairly decently.  The saw isn't as accurate or clean cutting as I would like leaving me some extra work with a hand file to clean up the cut edge by hand before deburring and sanding smooth.  With a bit of work, it eventually cleaned up nice and straight.  I cut the second spar web by hand using the large hand shears - it took longer to cut, but I found that if I was careful I could be more accurate cutting by hand and it took a lot less time to debur and clean up the cut.  I used each side of the factory edges of the sheet to be and edge for each spar web giving me a perfect factory edge to measure from..

With the spar webs cut to size, I measured and cut out the tapers at the inboard ends of the spars where they will meet the wing (the bottom of the spar web faces the ruler in the picture below)

The thickness of the 0.032 and 0.040 sheet make them awkward to roll/unroll, so it makes sense to cut the other pieces out while the sheet is on the bench.

In the picture below you can see the remaining 0.032 sheet after cutting out the spar webs (coiled at top of picture), the spar root doublers (bottom of picture) and the four rear spar channel blanks (middle of picture).  The two thinner strips on the right at 0.040 blanks that will be bent into angles as inboard rear channel doublers. 

The 0.032 rear spar channels and the 0.040 doublers are too long to bend at our shop, so I've taken them to the same shop who bent the flapperon spars for me previously.  I'll get them back this week.

I also needed to cut out the left and right 0.063 strut support brackets (bottom right in photo below).  So while I had the sheet on the bench I also cut out some of the other 0.063 parts for the fuselage - the fuselage parts will be put into storage until I need them, but at least they are done.  I ran out of space on the 0.063 sheet I had to layout/cut the spar web doublers, so I'll have to get some more from storage to get these done. 

So despite no blog updates, I have been working away.  Control surfaces are "done" and work on the wings is underway.  Looking at the completed parts picture I posted above I'm very pleased how far I've come since starting. I'm not sure I can put a concrete answer on how much I've got done, but of the approximately 275 aluminum parts to make, I've got about 145 done which is very roughly 53%.  Understand that's just parts made, not bent, assembled, drilled, debured, primed, riveted.

Onwards!

As always, thanks for following along.

A really productive day in the shop today.  Managed to finish off the last flapperon (inboard right).  A milestone part of my build is complete.  Here is a family pic of them all together:

The opposite end shows the open ends of the outboard flaps (on the left below).  This is where the aerodynamic tip inserts will go during final assembly:

With everything complete on the flaps, I stacked them up for wrapping in plastic sheet to protect them:

Once wrapped up tight, they go up in the barn for storage until needed back out for inspection and set-up on the wings.  Stacked on some of my rolled aluminum, from botton to top, my completed assemblies are stabilizer, elevator then flaps.

One thing I want to try is 3D printing some of my parts and the aerodynamic flapperon tips are the ideal candidate for this technology.

I wrote previously in my blog about 3D scanning some original parts and using the 3D model from the scan to print them.  I discovered that although my home server has enough processing power and memory for 3D scanning, the video card currently installed does not quite have enough chops for the job.  A replacement I ordered arrived last week from Amazon and I set to the task of installing it.  For some reason, the server will not power up (it has been sitting idle for a couple of months while I waited for the new video card).  Bummer, I will have to investigate this further before I can start experimenting with 3D scanning.

 
Meanwhile, our local library allowed me to bring home their 3D printer.  It broke several months ago and they have no money in the budget to repair it or hire someone to fiddle with it, so I offered to see if I could get it working.  No idea at this point what it will take to get it working (it is an early model) but I told them in return for trying some prints from my 3D scans, I would both work on getting it working for them and pay for any parts that might be needed.  From what they have told me, the extruder nozzle is clogged and the print bed may be damaged.

Very happy to have the flapperons done.  Next on the build table will be the slats which I am led to believe is one of the more challenging sub-assemblies of the entire build.  But that is what I got into this for - to learn :)

In an upcoming blog I document the 3D printer un-boxing, rebuild and repairs.

Thanks for following along.

So, a lot has been happening in the world in the last week or so.

The Novel Corona virus, better known now as COVID-19 has seen exponential spread across international borders from it's origins in China.  Unless you have been living under a rock or are reading this blog in some distant, future archive (thanks by the way!), news and anxiousness is rampant about what is now officially declared a pandemic.  People are scared, some more than they realistically need to be and world financial markets are feeling the squeeze. 

​Mandatory closures of schools, businesses and government facilities are becoming commonplace as we work to "social distance" ourselves from others.  Large groups, social gatherings, events and meetings are highly discouraged if not outright banned  Efforts are underway by people everywhere to prevent the spread of the virus and protect those who may not have the benefit of good health and the ability to fight off this particularly nasty bug - it can and has been shown to be fatal.  Unfortunately there are those ignoring common sense which is leading to more anxiousness and unease.  This has even lead to a very strange phenomenon of the panic buying bulk toilet paper! 

I've said before how much my shop time is my happy time.  It's my place to decompress from my emergency services job.  While a good portion of society has been told to stay home from work, my colleagues and I continue to work shifts in a busy 9-1-1 communications centre and although the calls for service have yet to peak as I think they will,  we are an essential service and will continue to come to work and answer the calls.  It's scary but I think we'll come out the other side of this craziness better off as a society from the lessons learned.

So, what better way to practice "social distancing" and "flatten the infection rate curve" of COVID-19 ng than to get to the shop and work on my build!  Here's what's happened since my last blog post.

A couple of weeks ago, I traveled south to visit Dad and made a side trip to Princess Auto and Aircraft Spruce for tools and hardware.  I needed an inch/pound calibrated torque wrench and was happy to find a good quality one on sale - score!

I stopped at Aircraft Spruce and picked up my online order of the remaining aircraft hardware I need for the build, other than some back-ordered nut plates and stainless machine screws.  Obviously this isn't everything I'll need (the interior will require some fabric fasteners etc), but what you see in the picture below is the lion's share of bolts, nuts, washers and cotter pins called for in the plans.

With the elevator all closed up I started fitting the trim control rod and servo arm

Here is a good look at the servo arm and trim control rod.  I'm not happy with how they fit together as there is too much slop or play between the pin and the arm, so I'll likely put some JBWeld metal epoxy in the arm hole and drill it out to match size the rod arm pin. 

The rod as it comes from the hobby store is plenty stiff enough to work in this arrangement, but comes much too long.  I attached the trailing rod end to the trim tab actuator bracket.  With the elevator trim in the neutral position, I held the road alongside the rod end, trimmed the rod to length on the bandsaw and ground it smooth on the bench grinder.

I specifically left the rod long enough so that I can trim is shorter if needed.  The plans call for the elevator to deflect 20 degrees up and 40 degrees down from neutral.  Before I can set the system up, I'll have to thread the this end of the rod for the safety nut.  I may change the "neutral" position of the servo arm to favour the 40 degree pull - it will take some playing around to get it just right.  The servo programming is the easy part!!

Some final clean up of the stabilizer was completed and I temporarily closed it up with rivets, just like the elevator.  The insides will have to be inspected by Tansport Canada before all the final rivets are done.  Stabilizer fences are just temporarily attached for storage purposes and may need to come off to open it back up for inspection, but I may get lucky and they can stay on for final riveting.

The following pictures show the completed tail assembly with outer and centre hinge pins installed.  It lined up perfectly and shows no signs of binding - very pleased!  (it's sitting on the bench upside down compared to how it will be mounted on the plane - it just sits better that way).

So!  The tail is now complete.  I currently have roughly 150 hours of work into it.  Once wrapped in heavy plastic it will join the rudder up in the storage barn.  There's about another full day's work once it's cleared for final close up to complete, with a lot of that having to wait for fitting to the fuselage.

​I feel so productive and safe from the world's dangers in the shop right now.  With all the temporary closures, I couldn't think of a better place to stay safe from COVID-19 -  working on the some temporary closures or my own :)

Thanks for following along.  Next up flaps and slats!

A real good, full and productive day today at the shop.

I'm pulling together the last of the details about the elevator.  Started off today by laying out the access hole for the trim servo:

The hole turned out well and deburred nicely.  I think I may have to enlarge the hole some, but I've already cut my cover plate as per the plans:

The easiset way to make sure the cover plate is centred over the access hole is to extend the layout lines far enough, that layout lines copies to the cover can be lined up:

The plans call for A4 pulled rivets to secure the cover - I think I'll add riv-nuts like I did on the fuel tank cover of the 701 wing repair.  I want access to the servo during routine maintenance inspections and drilling out rivets each time doesn't make sense to me.

Next up was figuring out how the elevator connects to the stabilizer.  According to the plans, the centre elevator hinge requires a bushing between the attach bolt and elevator horn and the specs are described in the drawings below.

 
I cut a small length of bushing tube material and confirmed the diameter is 1/4 inch:

Initial width was brought close to 2.5mm using the bench grinder.  Pro tip - hold on tight with a pair of pliers, the busing tends to go flying across the shop if you don't (this was my 3rd attempt!)

Careful hand sanding brings it down to the correct width of 2.5mm

This is where things got a bit confusing.  The plans clearly show the bushing extending on either side of the elevator horn - 2.5mm is barely wide enough to protrude out each side of the horn?  Should the bushing rotate in the elevator horn? Right now, my bushing is almost a press fit in the horn with very little to no movement. The bolt rotates freely in the bushing.  I'm guessing the bolt rotating in the bushing is better than the bushing rotating in the horn - easier to replace a worn bolt/bushing than a horn?

​Also, I've been told that any bolt involved in a moving assembly should be drilled and cotter pinned or safety wired. The plans call for a nylon lock-nut here, but I'm kind of leaning towards a drilled AN3-5 and appropriate castle-nut and pin.

An email to Roger at Zenith cleared things up nicely.  The bolt should clamp the bushing and the horn rotates around the bushing, not the busing around the bolt.  Roger was kind enough to send a reference page that explains all this:

So, as counterintuative as this is, now I know what the correct assembly should look like (just like the plans).  One difference is that the reference page explains the dimensions better.  If you look closely the bushing should protrude a minimum of 0.5mm on each side of the horn when the nut is tightened.

To make the bushing rotate freely, I ran the bushing tube on the belt of the bench sander to very slightly reduce the diameter, only enough so that it would rotate freely in the elevator horn, and then cut it to the correct width:

I test fit the hinge and everything looks good.  I used a non-locking nut temporarily to hold everything together, the proper nylon lock nut will be added at final assembly.  Just enough clearance and no slop in the hinge - very good.

Next up, I had to devise a way to accurately place the hole for the outboard hinge pin in the wing fences.  To do this I made a template for each side using card-stock paper.  To make a clean hole that doesn't tear open and also matches the 3/16 diameter of the outboard hinge pin, I placed the card-stock between to thin scraps of wood, clamped it together and drilled through:

Placing the template over the pin, I now have a convenient place to mark a reference line (the wing fence rear rivet holes) - sorry, took a pic from each side as I was doing this:

Black reference marks on the card-stock where the rivet holes are:

Connect the reference marks and voila - when laid across the wing fence, reference marks line up with rivet holes and the drilled hole in the card-stock shows where the hinge pin hole will be.  Easy!  From here, I drilled out the hole to 1/4 inch, in anticipation of adding a bushing:

The plans don't call for a bushing on the pin, but there is room for one and I'd prefer that for smooth rotation and protecting the aluminum of the wing fence.

To make the require bushing I added the inside washer then measured out the pin to where the other washer will be inboard of the cotter pin hole - turns out to be about 6mm between the washers when assembled:

It's hard to position this completely as the clecos protrude out from the hinge pin plate, but this is close enough for now.  Unlike the centre hinge, this bushing is free to rotate in the wing fence and around the outboard hinge pin.  It will be well lubricated and I may add some more washers on final assembly to tighten up any slack:

With the Arduino trim control pretty close to final set up, I wanted to double check the power source as it will be in the plane.

The aircraft will have 12v DC nominal power from the Corvair engine, so I need a way to regulate this down to 5V for the Arduino board and the servo.  Welcome to the "Buck Converter" - it takes up to 48V DC input and brings it down to a flat regulated output of the users choice.

The brass set screw on the potentiometer allows the user to set the output.  The beauty is the output remains a constant flat voltage, regardless of changes in the input (say when the alternator is charging the battery circuit).  Once set, I'll add a drop of LocTite to prevent it from changing due to vibration.

For testing purposes, I borrowed a 12V utility battery from Ron and hooked it up to the converter, and the converter to the Arduino test board:

The Arduino trim system runs exactly as it would powered by the USB cable - perfect!

I might use the converter below for powering the trim system.  The trim system doesn't draw a tone of current (very little actually).  This converter does the exact same thing as the one above, just not as bulky as the other one - reducing the footprint even further.  The converter above might be better suited for powering LED landing/nav/strobe lights.  Arduino will be used for lighting control too.

Next up, I started working on the mounting bracket for the trim servo.  I grabbed a previous incorrectly bent bracket to re-purpose as my mount:

Once cut down to size, I laid out the lines for the servo mounting hole:

A cutoff wheel in the Dremel and the air-saw made cutting the mount hole easy:

With the bracket built, I can work on getting it mounted inside the elevator.  I haven't got the push-rod or connectors yet, so I'll wait until I have those to mount the servo.  I'm not sure this will be enough support for the servo either.  The plans call for the Ray Allen trim servo to be riveted directly to the elevator skin - I'm thinking I might do a rework on my mount to attach it to the elevator spar.

What I could do in the meantime is fabricate and mount the trim control horn.  I cut the piece a long time ago and bending such a small part was challenging but I got it done fairly quickly: 

The control horn will be riveted to the trim corner.  The horn end will be drilled once I know the size/type of push rod connector I'm using.

 
It took a long time to get to this stage and I'm almost ready to.... pull it all apart for deburring, priming and reassembly!  It's nice to be able to move the elevator up and down now that it's attached to the stab - no binding, no grabbing.  Nice and smooth!  Really like how the fences turned out too!

With the horizontal tail group getting close to completion, it will soon head to storage.  Next up will be the slats and flaps - both parts of the control surface systems on the wings.
 
I've been spending a lot of time considering creating a 3D digital model of the slat and flapperon tips.  Normally these are blown plastic inserts or made from fiberglass and way to expensive to buy from Zenith.  My theory is that I should be able to print them on a 3D printer - possibly even out of carbon fiber!!

To create a 3D model easily, it should be possible to scan an original (which are the same as the 701, which Ron has several in stock).  Wouldn't that be cool!

There are many commercial grade (read expensive) 3D scanning tools available to buy.  But what if I could hack a 3D camera sensor that used to belong to a Microsoft XBox gaming console?  Yup, we can do that thanks to YouTube tutorials.

I picked up an almost brand new XBox 360 Kinect sensor bar for $15 dollars in Facebook Marketplace!  Next up, hacking it to interface with my Windows laptop, scan example items, and print them!  <Insert evil laugh here>

Thanks for following along, more to come!

July was a washout with regards to getting anything done in the shop, so not much available content for the blog....

A home project to replace the shingled roof on our house with metal took up 2 weeks of my July holidays and work travels took up a good portion of the rest of the month.  Day trips with family need to happen too. This Monday to Friday temporary assignment I'm currently doing at work is good that the work is both challenging and really interesting, but it only leaves weekends to enjoy the summer.  As of last week, I've been advised that I'll be returning to shift work at the end of September.  I don't want to go back to the communications centre, but on the bright side, my schedule during the week gets freed up substantially (4 days off every week), allowing me more shop time.

Speaking of work travels, I had a chance to check out the Chapleau Ontario airport.  Although there wasn't much to see (MNR fire base was quiet), I did notice this cool sign posted by the local flying club:

July and the beginning of August hasn't been a total loss I suppose.  I did manage to get some work done on the elevator and horizontal stab.

When I fastened the skin to the stab skeleton, I marked out where I needed to trim the trailing edge.  The extra was on purpose - it allowed for proper length and square fit.  Now that fitting is complete and correct, I can trim it back:

With the trimming done, the rear slot is cut.  This is where the elevator cables pass through the stab:

I notched back the spar doubler a small bit, leaving clearance for the rivet.  Everything was deburred, cleaned up and primed after this photo was taken.  Fortunately only had two places where this was an issue.

With the stab skeleton ready, I deburred the stab skin holes on inside and outside - there are a ton!

​Cortec primer on the rivet lines was next.  I really like how it applies - next to no smell, easy clean up and cures almost clear:

With the primer curing, I turned my attention to the elevator skeleton.  Some final measurements to ensure it's built square and it is ready to taken apart again for final debur and prime.

The elevator skins are made of 016 aluminum sheet, folded at the trailing edge and fastened to the top and bottom of the spar.  It consists of two sheets of equal length meeting a the centre:

To allow the rudder to move left and right, the skins are cut out at the centre box where the rudder hinges are.  It's difficult to perceive in this picture, but once folded the cut out makes sense.

It's important to radius the corners of the cutout, so I started with a centre punch then a pilot hole and followed that up with a 3/8 drill hole.

Cut outs complete for the left elevator skin.  Easier to see how this will look when folded.  Round file and debur tool to clean things up.  This is a exposed edge, so I final sanded it with 360 grit:

Careful use of the bending brake got the fold most of the way, then I used a small diameter aluminum rod to finish the fold to the 5 degree bend called for in the plans:

I used the same piece of pipe to curve the elevator nose skins that I had used for the horizontal stab - much easier this time.

​ Skins complete:

By this point the primer has cured on the elevator skeleton.  Re-assemble and check for square - all good to final rivet.  I'll wait to final rivet the tip ribs once the skins are on and I can align the elevator and stab hinges:

With the prime cured on the stab skin, it is reinstalled for final riveting.  I've decided to river the curved side (lower) and leave the flat side open for inspection.  It's kind of weird order - first place the skin over the spar pick ups and cleco everything down tight:

Flip everything over and cleco down the flat (upper) side:

  
Flip it back over and complete the riveting on the curved (lower side).  Really happy how everything is coming together and how straight everything looks :)

The stab is essentially complete at this point.  Remaining items to be done are final rivet the hinge assembly (waiting elevator match up), cable pass-through slot in leading edge and fairleads (rub strips).  I've also decided to add wing fences to the stab tips which have valuable aerodynamic benefits and really cleans everything up.  More on the fences later.

Next up, get the elevator skins fitted up, then cut the trailing edge for the trim tab and install the servo.

Thanks for following along, more to come soon!

You know that satisfaction of reaching an important milestone when working on a large project?  The joy that is only tempered by the fact you know you still have a long way to go?  That's what today felt like..... incredible :)

After deburing, cleaning and priming all the parts for the horizontal stab, everything was reassembled and checked for square - all good and ready for rivets!

My daughter came to the shop to capture the first rivet being pulled on my 750!  I don't think I can wipe the grin off my face.  All the work I've been doing to form parts from paper to CAD to cardboard to aluminum to bending - it all comes together here.

There it is - rivet # 1 of MANY more to come.  Before I close up the stab, I'm thinking of somehow identifying this rivet - a small inscription or label or something.  All small steps may seem to make the journey a long one, but progress is defined as forward motion towards a goal.  Happy builder am I!

With the first one down, the rest are quick to follow....

​The rear bracket riveted in nicely.  I'm going to wait to final rivet the attach bracket and gusset until I have the elevator complete and can match them up to ensure the pivot holes lined up for drilling.  Same with the front attach brackets, but that's more for aligning the skins.

Very happy how this is all coming together.  Next up, I'm going to start building the elevator skeleton using the exact same processes.  Drill, fit, debur, repeat.  When both are complete, I'll start working on adding the outer skins.  I'm also starting to think of a system for activating the elevator trim system that should be an improvement on the plans.

Thanks for reading.​

With the 701 wing gone from the shop and into storage, the bench is now clear for my 750 tail group and I can get to building my airplane using the skills and knowledge I've learned.  This blog post will try and capture several days of shop work over the past week - it's been busy and to the uninitiated observer looks like it's moving really fast, but there's a bunch of work that goes into this that pictures will never capture.

The factory tail spars come predrilled, with all the rivet spacing laid out - this saves a bunch of time on layout, but you still need to consider order of operations and keeping everything square.  Slight imperfections in scratch built parts means measuring everything closely.

​And here it is.... my 750's first drilled hole (back drill from rear spar hole to doubler) and cleco.  This is the basic procedure and first step of everything to be assembled to come.

Each doubler is done the same way, A3 hole in the spar as guide, A3 drill through doubler and clecoed.  I pleased my doublers fit as nice as they do.

With everything together, drill again, this time upsizing to A4 and again to A5 where needed and cleco.  It's quite repetitive but this ensures nice clean and centred holes.  The other thing we did was line both edges of the table with angle iron clamped to the edge.  2x2 HSS tubes laid perpendicular across the table provide a level reference point (flat table) to work with.

With the spars upright and referenced flat, I started to trial fit the rear and nose ribs.  These to are back-drilled from the spar to the rib flange, then up drilled to A4 and clecoed.  A quick measurement confirms my scratch built ribs are correctly sized and by default the spars are spaced correctly.  Excellent!

Spars and inside ribs are drilled and clecoed in place, so next are the tip ribs.  The key here is make sure they are square to the spars and the spars are square to the rest of the assembly.  The front end of the tip rib is connected to the front spar (left side in picture) by a fabricated 025 "L" bracket.  It takes a bit of ingenuity to make it all square and drill it, but not overly difficult - and certainly a TON easier that repairing the completely un-square 701!

To help square everything up before final drilling of the tip ribs, we added some uprights to the bench (there were eventually 4 of these, one at each spar end front and back).

The use of standard "L" around various parts of the airframe allows for small adjustments to square everything up as well.  Kinda explains why I need so many of these (see this post). 

Here is where the tiip rib attaches to the stabilizer spar.  Drilling this takes some thinking about which order to do it first, but the uprights hold everything in place while the drilling is completed.  Another check of measurements first, then final drilling to A4 size clecos.

​With everything squared up, the horizontal stabilizer rear bracket assembly is prepped for installation.  This 063 thick aluminum plate is fun to bend, but again if you think it through it isn't that difficult.  The tabs are bent inwards to 98 dregrees from flat.  This is an important measurement as these tabs are where the horizontal tail attach to the fuselage.  I used a protractor and drew out an example angle on  paper to confirm both tabs were correct before test fitting it on the rear spar.

Clamp the bracket in place and back drill from the pre-drilled spar holes.... all good.... right.... wait a minute... damn...did I just put this in upside down?!?!

This is where paying close attention to the plans was important.  A traditional horizontal tail looks like a small wing - flat on bottom and curved on top.  The Zenith STOL aircraft have inverted tail airfoils, where the flat side faces up.  There are a number of reasons for this that I won't get into here, but what makes this confusing is that it goes against common thinking.  Multiply that by the fact the plans for the ribs and forms are drawn with the ribs flat side down, it'e easy to get confused which way is up!  I'm also building the horizontal stab flat side down to take advantage of the flat table to get everything square.

So, what saved my bacon?  The predrilled factory holes!  The fact that they are symmetrical and the bracket is centred on the spar horizontally means I just had to invert it before up drilling to A4 and eventually A5 holes.  What could have been a nightmare  was avoided, but I'll be much more careful next time!

With the bracket turned up to the correct orientation and DOUBLE CHECKED AGAIN before drilling, I worked on right sizing the holes and clecoing things in place.  Another check and everything is now where it needs to be.

Next to go on is the centre elevator hing bracket, one of three attach points between the stabilizer and the elevator.  The attach point is at the tip of the triangle and will be drilled later when we match up the elevator.

Supporting the hinge bracket is a support gusset, which was chaleging to bend correctly - again the plans give a somewhat confusing view, but a little figuring, fitting, and adjustments finally got things where they needed to be.  It's getting crowded in this area with all the clecos!

Like the ribs, clecos can be moved inside the spar or to the other side of whatever it is attached to - clecos don't seem to care and that's a good thing :)

Making notes on the parts as you go through assembly helps to remind you in the future.  Here you can see I wrote a note that an "AN-bolt", not a rivet goes in this spot - a reminder that the hole is drilled to a specific size that is slightly larger than an A5 rivet.  Before anyone comments that my grammar sucks, the term "AN" stands for a particular type of fitting (in this case a bolt) used to connect flexible hoses and rigid metal structures. It is a US military-derived specification that dates back to World War II and stems from a joint standard agreed upon by the Army and Navy, hence AN.

The final parts to be added to the horizontal stabilizer being measure/confirmed and laid out for bending - accuracy here is critical to make sure all three attach points for the elevator and the two from attachment for the stabilizer to fuselage are correct.  This will make rigging the plane easier at final assembly and a straight plane ALWAYS flies better!

I flipped the stabilizer over, making it easier to attach these brackets.  Alignment bother vertically with the proper amount protruding above the spar and horizontally in relation to the centreline of the spar is critical for tail alignment.  Looking at this picture is decieving, the brackets are perfectlyperpendicular to the spar - I know because I measured it 5 times and confirmed orientation 5 times.... no second chances here.

Next I measured up the stab/elevator hinge attachment brackets for rivet hole spacing and drilled them out.  I thought I might drill them as a stack, but I was concerned about alignment so I did the individually.  The plans are very clear here on where they attach to the rear spar and they installed accurately without issue.  So nice working with newly made, undrilled parts!

So,with everything drilled correctly, together with clecos and measured as correct, it all comes apart for final deburring, cleaning and corrosion protection.  Now was a good time to lable anything that might get confused when it goes back together for riveting.

Well, that's a lot of work done, approximately 14 hours in total.  I'm updating my build time tracker on the right of the page as I go.

Next up, prime everything for corrosion protection.  In hindsight, I think I'll wait to prime/corrosion protect parts until all the drilling/deburring is done - the drill and debur swarf tends to get stuck to anywhere the primer is already applied (it's somewhat sticky even after curing) which makes cleaning more time consuming when it doesn't have to be.  After that reassembly of the entire horizontal stabilizer for final riveting - my first rivets on the 750 will be so satisfying :)

Thanks for reading, more to come!

It's finally "done", the 701 wing repair/extension was completed a couple of nghts ago, but I'm just getting to the blog now.  Here's a quick update of what happened Thursday night to finish it off.

Off the table and to be prepped for storage.  Ron and I will add some plastic sheeting wrap over the ends to keep any birds out while it's stored in the barn.

I'm so glad to be done this repair/extension, but I can't deny how much I've learned.  Now the table is clear and I can focus can be on building my 750!

​Stay tuned more to come!