Back in the shop tonight, finishing up some of the smaller details on the elevator.

Got the motivation to cut the trim tab slot out of the trailing edge of the elevator.  The plans call for a slot for almost the full length of the trailing edge.  This doesn't leave much of the trailing edge remaining done this way, so after some discussion with Ron, I decided to shorten the trim tab somewhat.

Cutting the skin is tricky - have to be real careful not to damage the trim tab spar.  I decided to drill some pilot holes to work towards, then clean the edge up close using a Dremel tool.  It took several assemble/disasemble cycles to get it just right but it turned out nice a square.  A round file helped to round out the inside corners.

I've decided to add some trailing edge ribs on the rear elevator skin and inside the trim tab as well.  This not only supports the skin where I changed the cut, it also looks nicer and will be cleaner aerodynamically.

It took a few tries to get it right - there is no template in the plans for these, I'm making my own.  I'm happy with the fit and feel.

Next on my list of small details was drilling the trim actuator hole in the trim spar and elevtor lower skin.  The step dill was again very handy for this:

Took the spar out of the elevator skeleton to drill the matching slot:

Back together for final fit.  The slot stays the same as the plans.  I think I might try and come up with some sort of flexible cover for the trim actuator rod hole to prevent bugs, dirt, snow or rain from getting in there.

Started the initial fit of the elevator nose skins.  These need to be in place to confirm the correct spacing between the elevator and the stab.  Happy with the fit but surprised how much of the nose skin tucks under the rear skins - but that's what the plans call for and my nose ribs are correct!

With both nose skins temporarily in place, I set the elevator against the stab again to confirm (again) the alignment of the upper and lower horns and centre hinge bracket - all good.

Forward and rear brackets drilled and added - this really stiffens up the elevator centre assembly!

All in all a productive night.  I'm headed back to the shop in the morning to continue to knock off the small details - it all adds up!

After a much too long break from working on the airplane, I'm back at it again.  Not much has happened over the last couple of months in the shop.  Returning to shift work has been harder to adjust to than I anticipated.  Add to that the passing of my Mom, Linda in October and all the things to process both emotional and tangible - it's been tough to concentrate on anything else.

Mom was always one of the biggest champions of my dreams, including flying.  She was my first passenger when I got my licence in 1995.  I told the story of that day at Mom's Celebration of Life as it was one of my favourite memories of many during times I spent with her.

We went flying on a beautiful early spring day in a Cessna 150.  Typical first passenger type of flight, showing off my newly minted licence by taking a tour of local sights from above.  It was beautiful.

Mom always appreciated a good joke.  When we were turning base from downwind, I pretended to look around the cabin like I'd lost something.  Of course, Mom asked what I was looking for, to which I quipped "There should be a landing checklist in here somewhere, I might have forgot to bring it".

The look on Mom's face was priceless as she went from surprise, to fear to sly recognition that her oldest son was just trying to pull a fast one.  Fast transition!  She punched me in the arm and reminded me that landing checklists are important and I should have it memorized.  I'm not sure she ever truly forgave me, but she probably did.  She was that kind of person; kind, forgiving and loving.  I miss her very much.

I also know she wouldn't want me to delay getting my plane built, even if she never got the chance to see it or fly in it.  So this week I got back at it.

Work continues on the elevator and horizontal stab.  There are lots of little things to complete, but it's coming along nicely.  In order to mate them up, I had to finish adding the fences on the stab.  Here they are lined up where they will be fastened on the stab.  To ensure that both ends are exactly the same, I taped them together and dry fit them, marking out the rivet lines:

Quick fit check on the other end, before drilling A3  pilot holes through both

Pilot holes drilled then clecos to hold it in place to confirm measurements are correct and fence is equal all around the stab aerofoil:

The fence is 063 thick, same as the original outer hinge plates which  are attached at the trailing end with A5 rivets, so I'm doing the same here (where the black clecos are).  The A5 holes are already in the tip rib, so I used the rivet hole duplicator to match drill them on the fence.  The balance will be A4 rivets.  This combination will only improve the strength of the whole assembly.

​Happy how the fence cleans up the whole end of the stab:

​I flipped the stab over to make getting at the A5 holes easier

​Once flipped, I noticed how tight the fence is to the tip rib skin rivets.  I made a note to remind me to river the skin first!

​With both fences attached, the stab looks real good!

With the stab fences in place, now I could place the elevator in line and see how they line up:

Even without the elevator nose skins on, I was real pleasing to see them "together" for the first time.  Have lots to do yet, but it feels good to see the sum of the parts looking close to what they will be once done.

Also important was seeing that the measurements of the centre hinge is correct!  It's a tight fit tolerance but I nailed the measurements perfectly!  (Picture is not very clear, sorry.  Just noticed the camera focused on an errant rivet stem)

I placed the elevator horns temporarily in place to confirm the alignment - all looks good.

BINGO! Correct spacing for the hinge bolt and bushing.  So satisfying to know everything is correct!

Next I decided to take care of the elevator cable pass-through hole.  It starts with drawing a centreline on the leading edge of the stab and a measured horizontal where the cable guard angle will be riveted on.  Thank goodness for flexible rulers!

Sketch out the lines where the slot will be and draw the circles that make up the ends of the slot:

​Pilot hole to prevent tearing of the aluminum - that would really suck!

A small step drill bit used carefully does a great job.  With both holes done, simple straight cuts from edge to edge on the new circles to open up the slot.

The leading edge of the stab has a slight curvature to it where the cable guard mounts.  So once I had the guard angle bent, I rounded it out a bit to match.  This will be primed before riveting to the stab:

Not a bad prodcuctive couple of hours.  Like I said above, it's nice to see the sum of all the little parts I've done and it's motivating me to get back in the shop.

Next up, nose skins and tackling the trim tab.  I've managed to write some good code for the trim tab Arduino computer that will control the servo.

Thanks Mom and thanks to my wife Brenda for getting me moving in the right direction again :)

I consider myself so fortunate to have a workshop space to build my plane.  This is solely due to the kindness and generosity of Ron and Donna.

When I first talked with Ron about building my plane, he only asked that I share in some of the labour around the shop, such as cleaning and organizing, helping with other planes on the go etc.  One of the big ones every season is cutting, splitting and stacking firewood.

Over the past coupe of weeks, I've been over to the property where the shop is and worked with Ron and Donna to split up five backhoe buckets of hardwood and stacked it in the woodshed in preparation for this coming winter.  Although it's physically tiring and my shoulders are sore the next day, I'm glad to help out, and there is nothing better than working in a warm shop in the winter months!

Work had me on the road quite a bit the last couple of weeks getting some more project sites up to the latest standard, and I've got two more road trips scheduled in the coming weeks before I return to the communications centre.

While passing through Kapuskasing one morning, I passed their airport.  I noticed a Zenair 701 parked/tied down on the apron and made a mental note to stop on the way back through later in the day to have a look.

One the way back, I had enough daylight to stop to look.  You may recall, Dad and I traveled to St. Hubert Quebec back in June (see this post).  I spend a lot of time driving for my job, and I got to thinking about that trip and how one of the Buffalo Airways mechanics Ronny McBryan (Uncle Ronny) had traveled from Red Deer to St. Hubert and passed through Kapuskasing on the same route I was on.

With this thought in my head and just as I came over the rise in the road west of the airport, what do my tired eyes see?  Is that an orange tail!?!?  Holy crap!  It's a Buffalo Airways C46 Curtis Commando C-GTPO!
​

Unfortunately, there wasn't anyone around that could get me closer for a look, but I was dumbfounded what could have led me to be thinking about Buffalo Airways just before spotting one of their iconic war bird era cargo planes - so cool!

​Second unfortunate thing, I couldn't get anywhere close to the Zenair 701 either.  Oh well, maybe next time.

Here is a brief look at what I've got done when I've been able to get to the shop.

I needed to way to fold the trailing edge flatter without creasing the skin.  To accomplish this I taped two small diameter rods together end for end and secured it to the table.  I added a strip of wood near the middle to ensure the rod stayed in place securely for the bend:

The rod is slightly bigger than the radius required, but can be folded flat more once the skin is in place:

Like the horizontal stab, I prepped the table with blocks, lined up in parallel.  These will be my guide to ensure the skins are equal at the trailing edge: 

Skins are placed on the skeleton and roughly lined up.  Wide mouth ViseGrip pliers hold the skin square to the spar for match hole drilling to the factory drilled spar:

With everything double checked for square, the first of the spar rivet holes are drilled using the hole duplicator:

Happy with where everything lined up, the skins came back off again for mark-up.  It takes a bit of figuring as the plans aren't very clear on the rivet spacing and there are some offsets to consider closer the trailing edge, but it's doable with a little thought:

With the layout complete and double checked against the plans and skeleton, the holes are pre-drilled out to A3 size and the skin is clecoed back to the skeleton.  I centre-lined the ribs with red sharpie, making it easier to align the ribs beneath the skin for drilling.

I want to draw the skin down from the spar back to the trailing edge equally on both upper and lower sides.  This will ensure the skins are flat to the ribs and will continue to flatten the trailing edge.  The first 3 or 4 rivets back from the spar on this side - I'll flip it over soon and do the same on the other side.

With the skin secure with the ribs rivets, I went back and finished duplicating the spar holes out the A3.

I then added the reinforcing plate that Ron and I discussed over the centre spar box joint and duplicated the holes at the spar and added the new holes on the rear channel.  This really tightens everything up, and the entire centre section will eventually be riveted to A5 size.  The same reinforcement plate will be added on the other side as well:

One of the complaints early builder/flyers of the Zenair STOL aircraft was the lack of elevator effectiveness and authority at slow speeds - i.e. landing flare.

To help alleviate this, sever builders have added aerodynamic "fences" at the tips of the horizontal stabilizers.  These help keep airflow on the horizontal tail and over the elevator, preventing the air from flowing off the tips.

Following the examples shared by other builders on the Zenith forums, I set out to create my own based on their designs.

First was laying out the 063 aluminum sheet.  I placed the horizontal stab tip form on the sheet, along with the original outer elevator bracket.  I want 1.5 inch fences all around, so I measure this on the flat (upper) side of the tip rib:

The bottom edge was easy, how to do the top?  Make a tool of course!

A simple stick of wood, drilled out to accept a sharpie.  Trace around and voila!

Important to have exactly sized fences for each side, so I rough cut out the first one, fastened it to another rectangle blank and final cut them together as a sandwich on the bandsaw.  I rounded out the trailing edges a bit as well:  

 
With the final cutting done, a quick pass of the sandwich on the disc sander and some final hand sanding to clean everything up, they turned out very nice!  These will take the place of the elevator hinge brackets as well....  so if anyone wants to buy a pair of original outer hinge brackets, shoot me an offer.... hahaha!

​More to come on the elevator skins, support plates and hinge assemblies soon.

Thanks for reading!

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!

I'm finding it more and more difficult to keep my blog up to date - I've accomplished much in the last few weeks.  A lot of it has been routine fitting, drilling, cleco stuff so I haven't been taking many pictures.  There are a few updates to share though.

​With the one side partly secured with clecos, I moved the stab to the other bench.  A large square steel tube was placed on the top to gently bend the skin partially into position before we tightened the ratchet straps to pull the skin down tight around the nose and upper surface.

Long strips of wood help spread the strap loads across the length allowing for fine adjustment.  You have to be real careful here, too tight and the skin can collapse at the nose, leading to damaging kinks.

With the fit confirmed, I made a few reference marks, then it all comes apart and I can start the process of measuring the skin for holes.  This is the only way to make sure the skin rivets are centered on the ribs as I don't have the luxury of pre-drilled skins.

Measure twice and then twice again, using the stab skeleton as a reference.

Again, I don't have any photos of the assembly, but the process is the same as above - weigh down the skin with the metal tube, use the straps to draw the skin down tight.  The only thing that's different this time is drilling through the skin holes and into the structure below.  I worked from the nose back to the rear edge (right to left in the photo) and from centre section out to the tips.  Each hole gets a cleco until the rear most holes, ensuring a tight and bubble free fit.

Spar lines front and rear are drawn and rivet holes drilled.  These don't have to be done with the skin off as the spar is a straight line and on this side the spar isn't pre-drilled.  Again, measure 3 times - it's important the spar holes are centred on the spar flange:

I'm happy with how this turned out.  Next step was using the template I made earlier to start laying out the slots for the horizontal stab brackets

This cutting is very delicate.  The skin needs to be trimmed to be flush with the spar so the brackets sit flat and vertical against the spar.  Cutting the skin is fairly easy, but any damage to the spar will be fatal!

I traced out the approximate location of the slots using the template and confirming with the plans started a pilot hole

I used a Dremel tool and rotary burl bit to slowly expand the hole enough so i could see where the rivet holes in the spar for the bracket are:

With a confirmed visual and measured slot location, I redrew the hole on the skin and slowly used the burr and some gentle hand filing to get it to the correct shape and location, ever mindful not to cut or mark the spar.  Round files make a perfect corner:

Eventually with patience, the stab bracket fits nice and straight in the hole and perfectly vertical and flush with the spar underneath (it's sitting a little low inside the stab here as I couldn't hold it and take a photo at the same time!)

With that experience, the second slot went well too.  I cleaned up the ragged edges a bit using a Dremel sanding/cutoff disc.  The slots still have to be deburred properly, but that will come when the skin is off for full deburring:

On another note, Dad and I travelled to St. Hubert airport outisde of Montreal to attend the first flight of a C47/DC3 know as C-FDTD.  We've been following the epic journey of Mikey McBryan (of Ice Pilots fame) and his Plane Savers team as they restore to flight a WW2 D-day survivor - a DC3 that dropped paratroopers over Normandy on D-day and during operation Market Garden,  and that was sitting derelict, falling victim to vandals and the passage of time being slowly destroyed by neglect.

Here are a few personal pics of that trip - motivational for sure!  For a full experience and to see what an amazing accomplishment this is, checkout www.planesavers.ca - of particular interest, watch the YouTube segments from the beginning - awesome and well worth your time!

Here is a copy of the flyer they were handing out to guests:

What an honour to be there and share this with Dad and the thousands of others who followed the restoration was unbelievably amazing.....  what a great feeling watching it take to the sky again!  All I could think about were are brave young countrymen that participated in the D-Day invasion exactly 75 years prior - God bless them and thank you for our freedoms!

I was so happy to share this adventure with Dad.  As I post this blog on Father's Day, I'm reminded how much influence Dad has had on my life, particularly a love for aviation history.  Thanks Dad!
​
While in the Montreal area, I also picked up a left/right set of fibreglass wingtips for my 750.  These retail for $160USD a piece and I grabbed this uncut pair for $100CAD.  Steal!

So, it's been a productive couple of weeks.  Next up, I'll finish the stab skin, get the stab brackets installed permanently and proceed to skin the elevator. Once I have it skinned, I begin the process to line them up together and drill the mount holes for the hinge points.

Thanks for reading, more to come :)

Got a chance for a few hours at the shop last night.

The plans call for the stabilizer skin to be pre-bent to 90 degrees prior to attaching it to the skeleton for drilling.  Conventional wisdom from other scratch builders is that this can be a challenge to do right.... bending this incorrectly, either crooked or in the wrong spot on the skin can at minimum lead to challenges getting the skin to lay flat on the skeleton and at worst render this very large piece of 020 aluminum useless (kinks are easy to make in such thin skins).  I been nervous approaching this step, but with a bit of prep and double/tripple checking everything it worked out well.

First step was to mark the skin with the bend line which represents the middle of nose curvature (done previously) and lay the stab skeleton in position to confirm alignment:

I had to find a long enough (10ft) length of hard wall pipe to use as the bending form, as Ron doesn't have anything long enough in the shop.  I originally thought I'd need some schedule 40 iron pipe, but I managed to find this mild steel electrical conduit at Home Depot that will work fine:

​To prevent the sheet from slipping, I used wooden blocks as clamps, screwed down to the table:

Some thought went into the placement of the pipe in relation to the line.  The overall goal here is to pre-curve the aluminum leaving room to tighten the aluminum down, not to make the curve exactly the same as the nose ribs.  The pipe gives the curved surface to bend against.  So the pipe is not directly on the bend line, but where the bend begins.  Once exactly straight, the pipe is secured at both ends with blocking screwed down and a strip placed in the end and screwed down to the table to prevent it from lifting:

It's hard to capture when both of us are lifting the skin and forming it around the pipe.  We use a long piece of rigid steel tube to place even pressure across the width.  It's bent a little at a time, readjusted under the pipe, bent again, shifted, bent until the 90 degree bend is complete.  If you look closely at the end you can see the incremental marks we worked to:

The size/width of what will be the horizontal tail on my 750STOL is really evident when I stood the skin upright.  At almost 9 feet across it almost touches the ceiling!

Placing the skin back on the bench and adding the stab skeleton confirms the bend is very close (enough) to make assembly move on to the next step.

In a previous post, I mentioned making a decision having to be made about which surface to fit first.  While researching how to bend the skin, it became apparent most builders suggest easiest is attaching the flat side first and drawing the skin across the curved side, so that will be my plan too.

Another challenge faced by scratch builders is that nothing made by the builder comes pre-drilled.  In my case this becomes compounded by the fact my factory spars have rivet holes already - so how am I going to match those blindly from outside the assembly?

First step was to drill though the existing spar holes to match the holes on the doubler from the outside - no problem, that part is easy.

Now how to proceed?  I can't drill from inside the skeleton out through the skin, there isn't room for a drill inside the spar web that is big enough to drill straight and the strap duplicator won't reach that far.

I placed the stab skeleton back on the skin all squared up and marked some of the points on the skin where holes will have to be drilled.  I really don't like this method as there is too much room for error if the skeleton shifts even the slightest over the length of the skin and there is no easy way to clamp it down.

Before drilling more than a couple of holes, I flipped things over on the bench, moved it to the edge where the top side can hang over the edge and secured the skin where the holes matched up at the one corner:

The trailing edge holes I can rivet from the outside and matching them up is easy with the duplicator.  There isn't a good way to blindly drill holes in the forward spar that guarantees a tight fit of the skin and correct hole alignment - and no second chances.

This got me to thinking about a way to drill from inside like I want to.  The only thing that I can come up with is buying a tool like this that will fit inside the spar, but man they are expensive and most require specialized drillbits:

I'll continue to ponder this until the next time at the shop and maybe Ron and I can come up with an alternative.  Happy with how this stab is coming together so far and really glad the bending of the nose worked out so nicely.

Another thing that got done for each of the airplanes being built in the shop was the elevator hinge pins.  Made form plate steel and a modified AN bolt, Ron put several hours into each of these.  What you can't see from the picture is the tiny cotter pin hole drilled in the pin or the finite welding he did making these - excellent work.  The black paint is a first coat of anti-corrosion primer:

Back to the shop this weekend for a whole day hopefully on Sunday.  Got to keep moving this project forward :)

Thanks for reading

I worked this week on getting the elevator trim channel installed on the elevator skeleton.  I went over the plans several times to visually ensure I was adding the trim to the correct side of the elevator (remember, I'm building it upside down to take advantage of the flat upper surface of the airfoil).

Again, the plans have to be interpreted correctly - in this case the position of the channel is determined relative to the trailing edge of the elevator.  But, that can be difficult without the elevator skin installed as the fold of the skin at the trailing edge extends past the tail end of the elevator rear ribs.

To solve this, I made a small narrow strip of 020 aluminum and bent it exactly as the elevator skin would be - it looks rough but it is exactly the right length to simulate the trailing edge:

I placed the strip in position and clamped it with clecos to the spar as if it was a complete skin.  Measuring back from this temporary trailing edge, gives me the position of where the elevator trim channel should be but gives me room to to see my work.

Even with the measurement confirmed, I was having a hard time getting the trim channel to fit correctly, until I got a look at the build pictures that come with the plans.  Turns out the kit supplied channel has been joggled at the end, allowing it to sit inside the tip and inner elevator rib.

Once I joggled my channel (that sounds bad as I type it), it fit in the ribs where I needed it to.  This automotive body panel air tool is very handy for this:

The middle elevator rib gets trimmed down to fit between the spar and the trim channel.  It's attached to the trim channel by an appropriately sized L bracket. 

With everything squared up thus far, a quick check of the elevator alignment to the horizontal stabilizer shows extremely close to the plans, so my measurements, cuts and bends are very good and accurate.  Very, very happy.

Next step is to start cutting the skins.  These are fairly large in size and the bench is pretty crowded at the moment, so I rolled out the 020 sheet and traced out the skin on the floor, leaving it a couple of millimetres wide and long - it can always be trimmed back once I have it fitted to the tail skeletons.

First up is the horizontal stab skin.  Making it fit correctly is challenging as you have to make holes AND account for the curvature of the skin across the top (bottom) of the airfoil as well.  A kit skin would already be trimmed and holes cut for the front and rear stab brackets.  As a scratch builder, this isn't a luxury we benefit from, so we have to come up with a workaround.  Time for a template!

First step I did was to mark the location of the front brackets on the spar: 

In order to transfer these measurements to the skin, I made a template from scrap 020.  I cut out the space needed for the rear bracket, keeping in mind the overlap that is required by the real skin past the spar (15mm):

I removed the front brackets and with the template now in place (clamped) where the skin will be  including the curve, I drew a line with a straight edge to represent where the back of the spar is - the goal here is to simulate where the final skin will sit in relation to the brackets.  It's better to make mistakes on the scrap than on the full skin!

Knowing where the brackets come through, I was able to measure-mark-create the matching holes in the template and gently open the holes a little at a time with a Dremel tool until the brackets can be reattached where they will protrude through the skin:

I'm very happy how this template fits and I'm very confident it will transfer the positions of the holes to the real skin.  I'll use the template to cut the slot for the rear stab bracket before final fitting the skin, but for now I placed the skin across the stab skeleton to check the fit - perfect, nice and square with the outer tip ribs and has the correct overhang of the spar.

Now I've reached a decision point.  Do I fit the skin on top first and tighten it down with straps across the flat bottom or vice versa?  Both have advantages.  I can work form the rear bracket at the spar, fit the skin over the front brackets and pull the skin tight across the nose.  Or I can start at the spar on the flat side, secure it and draw the skin tight around the nose, over the curve of the top  - essentially working in the opposite direction.  I've read that drawing skins tight over a curve is easier, but that means fighting with the brackets.

Either way, the skin will need to be pre-bent at the line that defines the tightest curve first - at the nose with a 27mm radius.  The plans show a 90 degree bend in the skin prior to wrapping it around, so I need to get that done first.

I flipped the skin over on the bench to mark the centre of the bend line as per the plans (checking very carefully to mark it in the right spot - right and square:

A long piece of factory edge aluminum clamped down with wood blocks makes a great straight edge:

With the scribed line, I slipped the sheet under the stab skeleton to where it overlaps behind the spar 15mm and the bend line coincides where it should.

​The next step will be pre-bending the skin, but I'll need to obtain something close to 27mm radius and more than 8.5 feet long so I can clamp it to the bench.  I was thinking a piece of 2 inch ABS plumbing pipe might work, but it may not be stiff enough laterally, so maybe a piece of steel pipe.  Unfortunately, Ron doesn't have anything that long in house, so I guess I'm going shopping :)

Thanks for reading, more to come!

The next sub assembly to do is the elevator.  This is the trailing edge of the tail and it's primary function is to control pitch movement for the aircraft in flight.  The initial assembly of this structure is somewhat less complex than the horizontal stab, but as always just as critical to get straight and square.

The nose, tip and rear ribs I formed fit almost perfectly and with a bit of trimming squared up the spar really nicely.

Being able to interpret the plans is becoming more apparent as I progress through this build.  One item missing on the plans is the distance from the elevator spar to the elevator rear support channel seen below.  The builder is left to decide where this fits.  From what I can determine, the placement is designed to be back far enough so the flanges on the support channel are equal in height to the inner rear ribs.  This would make sense as the skin and elevator hinge assemblies attach here.  Front to back spacing is held temporarily in place with tape, squaring the whole thing up proved to be a bit tricky but I got it done without too much issue.

I had some discussion with Ron at this point, as I wasn't happy with the rigidity of the  elevator assembly.  I know that things will square up and get stiffer once the skin is on, but the assembly seems a bit lacking in structure at the middle where all the force and weight is acting on the elevator in flight.

Ron suggested I make a small modification that he is doing on his 701 builds by adding a 016 gusset plate across the top and bottom of the elevator centre section, extended out to the spar.  

I liked the idea and set out to make the suggested gusset plates.  Even at 016 thickness this will strengthen the centre spar of the elevator without causing undue problems adding the elevator skins.

I've drilled them out to A3 and will wait for A4 holes once the skins are on.  One on the lower side....

​...... and one on the upper side:

The last pieces to be fit on the elevator spar skeleton are the tip ribs.  It's a bit of a juggle to get them in the exact right position, but they fit perfectly.  Figuring out the order to drill them and the attachment angles to the spar was fun, but I got it done.  A pair of wide neck welder's vicegrips are excellent for holding things together for drilling (note the protective masking tape on the pads to avoid scratching the aluminum):

Here is a picture of the elevator tip rib clecoed into place.  The final rivets here are four A5 rivets which also hold on the outboard elevator pivot pins.  Ron and I are going to weld up enough sets for each airplane being built and the holes will be matched with the A3 pilot holes I've drilled here.

As mentioned in my previous blog post, I'm considering options for a system to control the elevator trim tab.  The plans call for a Ray Allen trim actuator and digital trim position indicator for the cockpit.  But at $400+ I'm exploring alternatives, including substituting in a giant scale RC servo.

The Ray Allen system is spec'd to provide 40 pounds of linear push/pull force.  Current metal gear RC servos are more than capable of meeting or beating that spec and with a bit of microprocessor power and programming are an attractive alternative.  The whole replacement system from front to back including servo, a cockpit indicator and voltage regulators will likely be less than $100.  The question is how?

Welcome to the world of Arduino, a programmable microprocessor board based on the AT328 chipset.  With a bit of time, I believe I can use the Arduino to not only control the trim servo but provide failover support and control correlation.  In addition, I have many options for how I want it to display in the cockpit, from a simple bar graph LED to a more intuitive graphic display.  Only imagination limits me here.  I',m also considering an Arduino board for controlling LED navigation lights and LED strobes.

So what does an Arduino processor look like?  There are several models of boards all with different strengths and weaknesses, but most of either are related to what the board is capable of providing. I want the board to be simple to use but small for space considerations behind the control panel.  For my prototype and likely final design, I've settled on the smaller sized Arduino Nano for the trim system:

I went on Amazon and ordered the Arduino Nano board and the associated mounting pins.  I was able to find a 3 pack that included the unsoldered breakout pins.  My plan is to use one board to prototype the trim system, one board to make for the airplane (wire soldered to the board) and one spare (in case one decides to poof into blue smoke if I screw up).    I also ordered a voltage step-down board (top of picture) - the trim servo operates on 6 volts, so i needed a way to power it from the 12 volt system:

The easiest way to prototype and learn how to use the Arduino board, is to mount the pins on the breadboard, then place the Arduino on the pins.  From there careful soldering each pin of the Arduino:

The Arduino is supported by a large online community of programmers, experimenters, robotic designers, musicians and others.  It's simple but powerful programming language is easy to learn and because it is "open source code" based, there are literally thousands of example projects to build from and modify.  I won't get much more into it here, but if this interests you, check out ​https://www.arduino.cc/

After getting everything together, I powered up the Aruduino from the USB port of my laptop .....  IT'S ALIVE! (I guess it's a stretch to consider that this might count as the first "power" my aircraft has had - I'm such a geek!)

​After a bit of fussing around with loading up the correct USB drivers so that the Arduino programming application on the laptop can talk to the board, I uploaded my first "sketch", (the Arduino name of a coded program that instructs the board what to do).  In this case, I added an LED and used the basic "Blink" sketch which tells the board to blink it's on board LED light

Again, I know this sounds geeky, but it's really cool!  I messed around with the sketch and changed the blink rate and patterns and uploaded it again to see the result.  I've got a bunch of learning to do, but a work colleague sent me some links to YouTube instructional videos which I'll work through and learn what this board can do.

Well, that's it for tonight.  Back to the shop Thursday night to work more on the elevator.  Got to finish the centre section, the elevator upper/lower control horns and start looking at how the elevator trim gets mounted.  Got some disassembly, deburring and priming to do as well.

​Thanks for reading, more to come :)

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!