Self isolation in the shop continues when I'm able. Progress has been steady and unfortunately when things are moving along well it's sometimes hard to remember to take more pictures!
I continued building up the first of the four flapperon sections. It's been slower than I like due to a couple of rework items, but the lessons learned will help make the other 3 sections go together faster.
With the skeletons built, it was time to layout the skins. I cleaned off the bench and laid out some soft pile carpet for rolling out the aluminum:
When I ordered the aluminum from Aircraft Spruce it comes rolled up, in this case four 12x4 foot sheets rolled up together. I only need one at a time and can get two flapperon skins (and more small 016 parts) from a sheet, so the other three were rolled back up for storage.
One of the challenges of scratch building is making some the more complex bends, particularly things that are long/wide such as flapperon skins. I had similar issues with the elevator trim tab - trying to accurately make 3 angled bends to the correct length between bends and the correct angle at the same time.
For the first flapperon skin, I decided to cut it about 20 mm wider than what the plans call for. My logic is that I can always trim an edge if needed. I started with the nose bend,using a piece of 4130 steel tube as the form and a long board to fold it over. At this width it's challenging - the nose bend is only short distance from the spar edge of the skin but very wide. It's quite a task even with a long board to bend it to 90 degrees like the plans describe. Same process as the nose skins on the stab and elevator. I got it over enough though to make the skin fold down tight with ratchet straps when ready.
To confirm the skin was the correct length, I temporarily finger clamped the skeleton to the skin. So far so good. I proceeded to drill some holes through the skin and into the spar, but when I bent the trailing edge, the skin wouldn't reach to the spar... ARGH! I measured it six times to make sure before making that bend.
To fix the issue, I decided to revise my order of operations and work backwards a bit. I knew the folded over skin was correct, I secured the long edge of the skin to the spar then reworked the nose skin a bit to start the bend earlier. It's kinda hard to explain and near impossible to capture in pictures, but it worked well.
With the skeleton now located correctly inside the skin, I could scribe the spar centreline along the bottom side. Ron has a really nice long straight edge made from 032 that works perfect for this:
I drilled out the flapperon pick-up angles to A5. I was about to remove them and realized the importance of marking where they go back as everyrthing will need to come apart for cutting the holes in the skin and for eventual debur and priming. I figured a simple matching alpha character on the spar, the nose rib and the angle would work well for this.
While on the bench I measured out where the rib centre lines were and drilled them to A3, working from trailing edge to spar, keeping everything flat and tight. The inboard root rib can be seen in the foreground along with it's "toe-in" rivet line. Next was A3 holes through the skin and in the spar and nose ribs.
Again, I missed taking a picture, but to layout where the pick up angles protrude through the skin, I placed and example angle in position against the spar and nose rib, traced it to define the hole then drilled the corners from the inside of the skin to the outside. With the holes now defining the edges of the angles. I used the Dremel and cutooff wheel to open the L-shaped holes from the outside.
With the top and bottom ribs and the lower spar secured and the fit of the angles through the skin confirmed as good, I started the gentle process of wrapping the nose skin over with ratchet strap. With a long board to distribute the load across the width it went fairly easily and the skin curved around the nose ribs really nice and even. The short edge extended well past the spar leaving me clearance to drill new spar holes.
Here is the nose skin wrapped and in the correct position, spar holes drilled to A3 and strapping removed. Very happy how it looks, leading edge is correct in profile and perfectly straight.
Here is a closer look showing the new spar line on the skin (green) and the extra skin that will be trimmed off (anything right of the thick black line to the right of the A3 silver cleco)
Finished drilling the A3 holes out to A4 on the top side, flipped it over and drilled the bottom side A3 out to A4. A close look up to the first rib line you can see the flap attach angle poking up from the spar below.
With most everything now the correct hole size, I confirmed my markings where the inboard skin will be trimmed to match the root rib.
Everything comes apart again for trimming:
So here was another problem. I traced the "toe-in" line around the nose on top and on bottom and figured where they meet would be where the skin needed to be trimmed back to. Wrong! It's actually a complex curve as the nose isn't actually perfectly round. Damn. The tip of the root rib won't be covered by the nose skin - it misses by about 5mm.
Again, not many pictures of what I mean, but a couple of nights pondering what to do, I realized the best course of action was to move the rib inboard slightly and make up the difference. This meant a new rib attach angle which would be easy. Only problem was I had already drilled the holes in the skin into the rib flange, and they wouldn't match anymore..... hmmmm guess I need a new root rib. So back to the form blocks and dead-blow hammer again.
With a new root rib, it was a simple matter to mount it 5mm more inboard with a new attach angle, drill through the existing skin holes into the rib flange. Now the skin wraps correctly over the root rib tip - problem solved. It doesn't change anything on how it will mount to the wing and interface with the flap actuator rod either. Phew.
Next was adding the flapperon control horn to the root rib. I removed the new root rib again and traced where the control horn would attach to it. I used the spar attach holes to secure it with clecos, then drilled the other river attach holes to A4. Decided to use the drill press for more accuracy.
Here is the bracket in place, drilled out to A4. It fits flush against the root rib and in line across the top surface of the flapperon (which is upside down on the bench in this picture).
Next issue.... The plans call for a L doubler in the corner formed by the control horn and skin, secured by four A5 rivets. Unfortunately, I'd already drilled four A4 holes (circled in red) as I misread the rivet specs in the plans, mistaking the root rib for a full rib (at the other end). I could just drill these holes out to A5, but then the support doubler wouldn't be in the right spot and would interfere with the control horn bolt which goes through the trailing end of the horn (approximate position shown by the gold arrow in the picture).
I made up the doubler of the correct length and placed it where it needs to go, leaving room for the control horn bolt. By offsetting the A5 rivets and placing them between where the A4 holes are, and up-sizing the spar hole to A5, I can accomplish the goal and meet the plan requirements. The hole near the bolt will remain as an A4 rivet.
A little back drilling through the horn and doubler up to A5 and it looks good to go Crisis averted.
Assembly of everthing is now complete. It's recomended to leave the control horn bolt hole and flap pickup brackets undrilled until they are ready to be fitted to the wing. Also, the inboard flapperon splice plate that connects to the outboard flap splice plate is attached during final assembly. This allows for final offset of inboard/outboard to be done in final rigging.
Guess what's next..... it all comes apart for final debur and prime, then back together again for final fit and riveting. Then I start the process (hopefully quicker this time) on the other inboard flapperon.
It's good to be in the shop :) Thanks for reading, more to come.
Ok, funny story.
I went to the local hardware store to pick up some items. I needed some stainless machine screws for the trim cover plate and Brenda asked me to pick up some paper towels for thous house. I also picked up some 6mm drywall vapour barrier plastic, and a large roll of duct tape. While standing in line, I noticed some work gloves on sale, so I add that to my cart.
While checking out my stuff, I realized I had most of the makings of a murder kit! I mentioned that to the cashier whom I happen to know and we had a good laugh. No, I'm not planning anything nefarious!
With the machine screws in hand, I was able to secure the cover plate. Worked well, but I had to enlarge the holes a bit to make up for some slight offset in the rivnuts.
With everything done on the stab and elevator that can be done before fitting it on the fuselage, it's time to wrap them up for storage in the barn.
Nice to see an open bench again! I decided to start on the flapperons next, as I already have the ribs bent/formed. Can't believe it was over a year and a half ago I did them! (see this post).
The plans are quite detailed here, even though there are fewer parts. The flapperons are built in four sections, an inboard and outboard section for each wing. As such, there are left and right ribs with varying orientations, Like the stab and elevator, I found it easier to lay all the parts out for inventory before beginning.
In studying the plans, I came across a small discrepancy. The flapperon control horn (part 75A1-6) shows 2 different shapes. The overview assembly page shows it like this:
The part dimensional drawing matches as well:
But the assembly/rivet drawing shows a different shape (circled in yellow below).
I emailed Roger Dubert at Zenith who got back to me right away. Thankfully the dimensional drawing is correct and thankfully I won't have to remake mine. He was kind enough to include an updated rivet/assembly detail drawing as well. Not sure I saw this anywhere in the update pages. Problem (if it even was one) solved.
It's important to accurately place the ribs on the spar, as the flap bracket spacing must match what is on the wing when it is built. I decided to do the inboard flaperrons first, as they are slightly more complex. To start, I lined the left and right spars back to back and matched measurements for the rib attach points. These finger clamps are perfect for this task and this will make them the exact same.
Drilled the spar holes out to A3 to start, then back drilled through the spar into the rib flanges.
Here, the plans could use some clarity. No where do the plans tell you how far the outboard rib of the inboard flap stands-off from the spar. The dimension I needed is shown in yellow below.
The only way I can figure is to complete the root end then measure back to the outboard end. This will work as the root rib has specific placement and is "toe-in" a bit to match where the fuselage narrows behind the rear cabin post. At this point, I also used a sqaure HSS tube to act as my straight edge to make sure the nose ribs and line up parallel to the spar. This made measuring the "toe-in" easy too.
With the root rib in place and secured to the bench, I can measure back to the outboard rib and adjust as necessary. The measurement is defined by the width of the flapperon skin with the widest dimension measured from the tail of the root rib to the tail of the outboard rib. I marked this on the plans as I will need it again for the left side inboard flap.
The left inboard flap went much quicker, just had to remember the ribs face a different direction. I lined them up facing each other against the steel tube and everything is square and identical.
With the inboards done, the outboards went smoothly too. The rib placements are similiar, but the process is the same. This time the inboard rib is square to the spar (no toe-in) and there is no outboard tip rib. The tip is a fiberglass aerodynamic plug that is inserted later (I'm considering 3D printing it!).
Next were the flap attach brackets, made from 6061-T6 angle. 65mm long.....
....cut and beveled and corners rounded off. Still some fine sanding to do to clean them up before paint.
Marked for drilling.....
.... and drilled to A4. Until these are in position, I'll leave them at A4, but final rivets will be A5.
Here is the first one in place. The bracket needs to extend 26mm through the flap skin. This piece of wood I'm using is about 28mm tall, so this is correct accounting for the 0.016 skin. I'm happy with the fit.
Really happy with my time spent in the shop over the last couple of days. The flapperons are well underway and I'm looking forward already to the dreaded slats!
I was thinking I wasn't going to post the following video because I'd like to think fellow builders are a smart, rational and analytic group. But the more I see on the news about the ignorance of people regarding Covid-19 and the steps EVERYONE needs to adhere to it wouldn't surprise me that some still need the reminder. Take it for what it's worth. Be careful, be smart, be safe everyone.... FLATTEN THE CURVE!!
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.
I've primed and final riveted the elevator outer hinge pins
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!
Yesterday, February 20th was the 61st anniversary of what is known as "Black Friday" in Canada's aviation history. A once proud and world class aerospace industry was decimated when then Prime Minister John Diefenbaker rose in the House of Commons and terminated the Canadian designed and built A.V. Roe Arrow, the world's most advanced military aircraft.
Immediately following the cancellation, thousands of people lost valuable and good paying jobs and worse still, Canada suffered the loss of many talented engineers and tradespeople, a brain-drain to the USA, where the newly formed NASA gobbled up the talent for their fledgling space program. These loses included all the businesses who were suppliers of materials to the Arrow program too. All the aircraft, both operational and on the production line, destroyed by cutting torches for and sold for scrap. All the tooling/blueprints and research ordered destroyed. Iroquois engine program gone. Dark days indeed.
Over the past sixty years, debate has raged on endlessly about what could have been had the Arrow made it to production. Theories abound that at least one aircraft was spirited away before the axes fell - I'd love to believe it, but no concrete evidence supports this theory. Where would Canada's military and aerospace industry be now if the Arrow program was allowed to develop? Was the Arrow a victim of government shortsightedness or the geo-political realities of an emerging space/ballistic missile threat? Was it pressure by the USA to purchase anti-ballistic missiles instead? Maybe a combination of some or all of the above!
I was born much too late to know much about the politics of the time and it would be another 20 years before I really began to understand the ramifications of what the cancellation meant to so many. What I do know is that it saddens me to think our nation missed the chance to be an unstoppable aerospace giant.
Interest in the Arrow continues unabated today with several groups keeping the memories alive, both from a historical preservation view to groups wanting to resurrect the Arrow program.
A couple of documentaries and at least one made for TV movie about the Arrow are available for viewing online if you search for them. The TV movie (through the magic of film) did a good job of capturing the essence of what happened, but an even better spin off from the production was of a scale replica of the Arrow for film use. After the completion of the filming, the Toronto Space and Aviation Museum took ownership of the Arrow replica and displayed it for a short time at their facility in Downsview.
At that time the Downsview museum had plans to further renovate the premises to better house their large exhibits and to provide more detailed information for visitors and school programs. Plans included specific galleries to house the full-sized Avro Arrow replica, another for the Avro Lancaster and additional galleries dedicated to the history of the de Havilland aircraft company, Canadian achievements in space, including a theatre and planetarium.
Unfortunately in the coming years, the museum struggled to establish a viable following and was given the notice of eviction from its hangar ostensibly for failure to pay over C$100,000 in back rent, even though the museum was in the process of repaying the rent owed and had been assured they would not be evicted. The museum relocated the collection to a secure storage location at Toronto Pearson International Airport.
In November 2018 it was announced that the museum's collection would be relocated to Edenvale Airport, 100 km northwest of Toronto. By mid-December 2018 the museum's Avro Arrow replica had been relocated from outdoor storage where it had begun to deteriorate, to an Edenvale hangar.
Thanks to foresight of the airport owner and the work of dedicated volunteers at Edenvale, the Arrow replica had it's environmental and neglect damage repaired, it was cleaned up, reassembled and placed on public display.
I went with Dad last weekend to have a look - all I can say is wow!
The first impression I was struck with is how big an airplane the Arrow was. I'd seen a real Arrow cockpit artifact on display at the National Aviation Museum in Otttawa, but this really brought home the size. It's massive.
The orginal creators of the replica were able to get the original main and nose landing gear manufacturer Dowty Limited to make a real set from their original production plans. Hard to believe these gear and brakes would be large enough to support and stop such a large plane, but they did it well. The single row of wheels allowed the gear to fit in the thin wing instead of the fuselage body, freeing up room for more internal weapon loads, groundbreaking technology and design at the time.
I snuck up a set of maintenance steps to take the next two shots which give a good view of the famous delta wing. The tip of the rudder is 29 feet from the ground!
This picture gives a good view of the weapons pack or pod. More than just doors, the entire pod could be swapped out. A packed pod could be a combination of missiles and other munitions, electronic warfare gear or even supplementary fuel tanks. By carrying it internally, the aircraft could still fly supersonic, regardless of load.
Back to my build which now seems a lot less complicated!!
With my stailizer back open for final debur of the new stab fence rivet holes and assembly of the centre hinge support, I got a chance to complete the centre hinge assembly.
The plans call for AN3-5 bolts through the centre support and spar flanges. I placed them in backwards first to check that the nylon lock nuts would fit with enough thread showing when two washers are added - much easier to see this way. The plans and the assembly pictures aren't very clear on whether the washers are doubled up together or one on each side of the sandwich. I decided one on each side was best, one under the bolt head, one under the nut - it doesn't change the amount of threads available to the nut and distributes the load better across the aluminum.
The final A5 rivets are added to the support flange.
Overall, the fit is beautiful and rock solid. I still need to torque the bolts to 22.5 inch/pounds, just waiting for the proper torque wrench.
Next I cleaned and primed the elevator pieces in preparation for assembly.
I still like the Cortec primer. It's a bit tricky to get the right consistency when thining it, but at least it is water based and cleans up nice when I'm done.
The elevator trim servo installed very easily. I've replaced the plastic servo arm with an billet aluminum one which will be much stronger in use.
According to the plans, the trim servo cover plate is supposed to be riveted in place. I don't like this as I may want to service the trim servo and definitely want access during annual inspections without having to drill out rivets! So, I'll do the same as I did for the fuel tank covers on the 701 wing repair and install rivnuts.
I started with evenly spaced holes in the cover and place the cover over the hole to transfer the holes to the elevator skin around the access hole.
I pilot drilled matching holes then widened them up carefully to mount rivnuts.
I finished by flanging the cover plate edges. The fit is excellent and very serviable with little if any increase in weight. I think any is worth being able to look in there easily.
With all the parts Cortec primed and dry, I reassembled the elevator and started to drive rivets, working from the center section outwards to the elevator tips.
It's clear how the use of A5 rivets in the centre section makes this elevator assembly incredibly strong yet light.
Elevator lower skin is now in place. Still have to rivet the attachment points to the tip ribs and rivet the trim tab in place. I'll flip the elevator over next and temporarily rivet the nose and rear skins down for storage. Temporary only so it can be opened up for pre-close inspection by MDRA inspector.
Another one of Ron's projects is a Cessna 170 he is rebuilding. I gave him a hand moving it down from the barn to the shop where we worked together to get the engine off for work. It was cold and blustery, but we got it done. Happy for the chance to pay back some of the generosity Ron has shown me.
I've always known aviation is my passion and I've come to realize shop time is my happy place, whether I'm working on my build or helping Ron with his. In the coming week the tail will be done and I'll be moving on to the flaps and slats.
We'll never know what the Arrow could have been, but my dream is alive!
Thanks for reading, stay tuned for more!
A bit of time in the shop this week. Dismantled the elevator (again) and deburred the holes now that everything is drilled to right size. It's points like this in a project that make you feel both accomplished and behind at the same time. You realize all the work you've done to this point by the number of holes you've drilled, but taking it all apart for deburring seems like a backwards (but necessary none-the-less) step.
Deburring the trim tab after it is bent is problematic. The holes for the hinge can't be drilled without having it bent to shape first. How to debur the holes on the inside angles (see yellow arrows)? Make a tool!
Normally we'd use a rotary debur tool, but access is too tight. To get access, I came up with this idea.
1. Slot a piece of wood
2. Insert sandpaper
3. Slide onto flange
4. Gently and carefully slide back and forth along the length of the flange. The goal here is to remove the burrs, not to sand the flange. It worked really well!
A follower of the blog had asked me why the elevator skin looked wrinkled in the pictures on the bench and the look of wrinkles is due to the protective plastic coating on the sheet aluminum. I've now peeled that back anywhere there are rivet holes so I can properly debur them. I'm leaving the remaining plastic on the skins to help prevent scuffs and scratches as I work with them off the skeleton.
With the elevator skin off the spar, now is a good time to fit the trim servo. The bracket I made will work, but now that I'm fitting it I've discovered something I hadn't thought of. If I have to remove the servo for replacement or repair, orienting it this way (mounting screws are sideways in the bracket) means it will be painful if not impossible to remove it through the access hole!
I decided it best to create a new bracket similar to the one Ron is planning for his 701:
It took a couple of tries to get it right, but it turned out well!
I'll need to add a grommet or strain relief at the pass-though hole to prevent the servo wire from chafing:
The servo will sit on an angle, parallel to the inside of the skin surfaces - the more direct the push/pull rod can be to the trim tab control horn the better.
As I sit on nightshifts at work, I have some time to ponder what else I can do with the Arduino. The ideas are truly endless and easy to implement. One thing that really excites me is the ability to display data on little screens. For example, here is a picture from the internet where an Arduino programmer has an OLED (Organic LED) panel emulating a basic cell phone display. OLED displays are super cheap and highly customizable and some models are capable of displaying in different colours.
Here is another example of a development board with an OLED display connected to an Arduino mini exactly like the ones I'm using. They are very small in size, but can be used to display lots of things at really bright contrast and resolution.
Here's an animated guage from the interwebs being used for something someone was developing:
If animation can be done, animation in colour can't be much more difficult.
I'm pondering a small display like this on my instrument panel, with a custom display graphic. Perhaps a overhead drawing/graphic of my airplane with animated lights that blink in co-ordination with my navigation/strobe/wig-wag lights! How cool would that be? Here is a (very) rudimentary idea about what it might look like. I can't animate this picture, but I think you get the idea - the red/green nav/beacon/strobe lights would blink or in the case of the landing lights alternate back/forth when in wig-wag mode. Maybe I can animate the prop too hahahaha!:
Maybe instead of the bar graph LED showing elevator trim like I already have planned, I can integrate the bar graph onto an OLED display, either by itself or with the light display above:
My engine gauges will be traditional mechanical versions - much more robust. Everything I propose here is for non-critical indications.
I've got a long way to go before I have to worry about this stuff anyhow, but it is cool to think this is easily and cheaply within reach for a simple hobbyist like me!
Some my regular readers might have noticed I've removed the countdown timer from the right navigation bar of the blog. I originally intended this to be a motivator for me. I had set the goal of first flight to be my 50th birthday, but that is never going to happen. I got behind in my build with changes at work etc., so I'm removing it for now as it doesn't reflect reality. I'll continue to strive to get the build done.
Next up, priming the elevator pieces and reassembly for riveting!
Thanks for reading :)
As I mentioned at the end of my last blog post, I want to scan some of the parts into 3D digital models.
I'm making almost everything from scratch on the build, including the small tip inserts for the slats and flapperons. Normally these come with a kit and are made of either fibreglass or more recently are blown plastic molds. I could just purchase these, but Ron has originals from a 701 which shares the same sie and shape of the 750 ones. Purchasing is easy but expensive and doesn't do anything for increasing my learning. Making my own may not be much cheaper in the long run, but certainly equal or less and making my own also means I can learn some practical skills that come from 3D modelling and printing.
First step in this process is to 3D scan the original tips. Again, I could just purchase a 3D scanner and get at it, but what fun would that be?
When Microsoft brought out the XBox gaming system, they shortly after released a sensor system that can detect player movements and translate that into interactive game play on the screen. I believe this was in response to the Nintendo Wii game system which had already broke ground and was first to market with this type of player interface. Microsoft took the best of what the Wii motion sensor did with infra-red (IR) and expanded it to include camera capable of sensing colour, faces and more refined depth of field. Enter the "Kinect".
In this past decade of electronic and programming experimentation, it wasn't long until someone (much smarter than me I'm certain) said "Hey, I wonder if there is a way to hack this XBox sensor and piggyback on what Microsoft developed for other things?" One of the first uses was for robotics control - robots that could see (sense) and recognize objects. This quickly led to 3D scanning for types of objects, both for item manipulation and avoidance (is the obstacle in my way too big to move or is it of a shape I can grab/push etc.)
These type of developments often branch out to other things, including 3D printing. Think about the possibilities! Being able to 3D scan a rare car part and print a replacement for example. Scanning and printing replacement bio-mechanical pieces (heart valves). Printing materials are also evolving - industry is now printing everything from concrete to rubber to aerospace alloys.
Like 3D scanning, 3D printing has come also come to the home/hobbyist workshop - makes sense, these home hobbyist are often on the leading edge of these things, at least initially. At thankfully for less knowledgeable people like me, they often share their knowledge online - thanks YouTube and Instructables.com!
So, where to get started. I picked up an XBox 360 Kinect sensor. It is the most current one being used by 3D scanning hobbyists and has wide ranging support.
The hack of the sensor requires 3 items. A 12 Volt power adapter (bottom left and middle), the male end of a USB cable (top) and the Kinect sensor itself (cable end on the right).
Normally the XBox console gets power and sensor data directly from the Kinect. As a result (and probably because Microsoft wants to control everything) the Kinect has a proprietary plug similar but not exactly like a USB end. The third party 3D scanning software runs on a Windows computer, so that requires a USB connection. So, my hack requires replacing the proprietary XBox connector with a USB and also injecting 12 Volt into the cable to replace the XBox console power.
I found this wiring diagram in one of the online tutorial videos. In this case, the author wanted to dual-purpose his Kinect sensor for 3D scanning and maintain it for gaming use. To do so, he added a switch in his diagram - I won't be doing this, I don't intend on reusing this for XBox, so I can eliminate the switch and the XBox end shown on the left:
First step was to clip off the unneeded end of the USB cable (the phone end in the case of my sacrificial USB cable) then strip off the outer jacket of the clipped end:
Strip back the outer shielding if there is some and the inner foil shield if there is some (cheap cables don't have these, that's why they are cheap!):
Trim away the two shields, leaving the traditional white (data -), green (data +), red (5V +) and black (ground) USB wires:
Repeat the process with the Kinect cable (cut off the proprietary plug and strip/trim the shielding:
First thing I noticed once the shielding was pulled back was an extra brown wire I wasn't expecting....hmmm.... I was expecting a gray wire. Wonder if the diagram is referring to the outer shield, it's kinda gray?
A little further reading in some of the comments on the YouTube videos and some of the instructables pages I quickly discovered that Mircosoft switched to a brown wire from gray at some point. Problem solved.
I tinned the wires first after stripping of the insulation - this makes soldering them together much easier when the time comes. I also added thin wall heat-shrink tubing to each connection which once I confirm everything is working, will be shrunk to tighten everything up. Next, solder white to white, green to green, red to red.
Next, add in the 12 Volt supply lines. Positive 12 Volt from the wall adapter to the brown wire (gray in the diagram). Lastly, black wire from the USB side, black wire from the Kinect side and Negative 12 Volt from the wall adapter (hard to see in the picture sorry).
Next, connecting to a computer and powering it all up - hopefully no smoke escapes! Unfortunately, my laptop doesn't have a graphics card that is supported by the 3D software, so I'll have to wait to get my home server back up and running to test this, but should be good!
Not much I like better than wiring projects, can't wait to do more of this on the airplane.
I'll file this in tools for now and get back to it soon. Want to get the 3D scanner working so I can scan the flapperon and slat parts I mentioned above then print them. Carbon fibre anyone? :)
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!
Happy New Year everyone!
With the Christmas holidays over, its time to get back..... WAIT!!
Failed well pump at home - replaced/repaired.
Failing clothes dryer - replaced.
Updated home network infrastructure.... started and functionally complete, but need to do more.
Check engine light on the car and new front struts installed.
Back to work... shift shuffle meaning an extra day of work to balance out the hours....yay me.
So, unfortunately the shop has taken a back seat for a couple of weeks. However, I AM BACK!
First up, finishing the centre section drilling out to A5. There is no question the number of rivets make this centre section solid:
Drilled out the rest of the elevator skin and nose skin holes to correct size:
Caitlyn came over with me to the shop on boxing day to shoot some pics of me working. Here I've taken the nose skin off the elevator to prep the outer hinge plate/pins.
The plates are made of 4130 steel, so it's important to centre punch them so the drill bit doesn't wander:
A bit of WD40 helps cool the bit, 4130 is a lot harder to drill than aluminum:
First holes drilled and plates clecoed in place - back drill to A3 then A4, then A5:
Nose skins back on, back on the bench with the stabilizer to start lining everything up, and...
.... uh-oh.... some interference between the nose skins and the centre support brackets. Apparently this is a common problem which is easily remedied by trimming the nose skin slightly and trimming the back the rudder support plate edges to clearance the nose skin as it pivots.
The fit of the hinge pivot point is still bang on - good!
Before pulling them apart again, I used a sharpie to rough out where I need to remove some aluminum:
While I had some downtime during a nightshift at work, I rigged up the trim servo and Arduino controller along with an example rocker switch. I had set this aside for several weeks but I wanted to refine my programming code a bit. This is a refurb laptop I fixed up and it took some more work getting the proper drivers for the Arduino installed amongst other things, but once I had those my new code loaded up perfectly and it looks like I've got the system nailed down to do what I want!
I brought the mock-up to the shop to show Ron but decided it would be a bit easier to demonstrate by mounting it to a board. I've added some spare LED lights to represent a cockpit indicator and a suplus limit switch to represent a momentary contact switch. I also added a really fancy post-it note flag to the arm of the servo to make it easier to see in a video.
Here is a short video describing the components of the system, my reasons for doing so and a demo of what it currently is programmed to do. Be kind, I'm no Martin Scorsese HA!
I've been thinking hard on how to bend the elevator trim tab. It's 025 thick and quite long. In addition, it has some complex tight bends that will be hard to do effectively on the bending brake, so I had to really think out an order of operations.
Like I usually do, I made up a test piece from some scrap 025 and used it to judge if the plan dimensions accurately reflect the true fit of the trim slot. Unfortunately, they don't quite fit - the gap is too wide to be covered effectively by the piano hinge.
I had previously cut a chunk of 025 to the flat dimensions called for in the plans. This the same dimension I used for my mock up piece. This wasn't going to work. The challenge is making the strip wide enough to account for the bends, the depth of the trim tab, the fore/aft distance in the slot and the overlap where they meet the hinge......hmmm....
After much thinking over breakfast coffee it dawned on me - why constrain myself to the flat part size listed in the plans. Why not cut the flat dimensions a bit wider or taller, then trim once I'm happy with the fit? I hate wasting aluminum in this way, but if I oversize the flat dimension enough to clearly cover the trim tab and enough to make use of the cutoff for something else, there won't be any worse waste.
At minimum, I'll salvage the cutoff and my original flat piece for other things yet to be fabricated.
First bend is the small tab at the hinge joint. The bender does good work on this, but can't bend far enough closed on this radius, so I had to bend it down further by hand. Fastening it the bench and leaning on it with a 2x4 worked. Next I bent the lower angle on the bender - this one is much more open so it worked as expected.
I placed the sheet in the approximate position in the trim tab slot. Width is a bit close will trim it down a bit to avoid any interference with the trailind edge. It''s clear from this picture the sheet I cut is well wide enough to cover the return bend back to the hinge.
Next I started fitting the hinge. The key here is to align the hinge left to right to take best advantage of a full barrel at each end. The barrel of the hinge alse needs to fit snug up against the trim spar. I used a small spare piece of hinge to mark out the correct length and it fits perfectly to the spar laterally.
On top is the spare hinge, length marked in green and my new hinge below it marked in red where I want to cut it
A chop saw makes quick work of the folded hinge, cutting though it evenly and easily. For the next step I pulled the pin out and ground down one side of the hinge arms to accommodate the safety wire required at each end to prevent the hinge pin from working it out - that would be bad!
To allow for safety wire, the hinge pin is slightly shortened to be just long enough to reach the last barrel at each end.
I remembered someone online suggesting using the bench grinder to slightly chamfer the rod ends to make sliding it back down the barrels easier. Just a small thing but made all the difference when reassembling the hinge several times over the course of this work. I also plan on using similar hinge to close up the engine cowling which will be open and closed more frequently - more on that later.
I flipped the elevator over again. When I was drilling the elevator skin, I didn't drill the holes where the skin meets the trim spar because I was waiting to see how the hinge would fit. As it turns out, this was a good idea, it saved me having to drill twice. I marked out the 40 pitch hole placement, placed the un-drilled hinge between the skin and trim spar and drilled it out to A3 (picture is after layout hinge pin not placed as of yet).
With the hinge apart again, careful drill of a small hole through the last barrel at each end to thread the safety wire when final assembly of the trim tab is complete. In this picture, I've already drilled out the 40 pitch A3 holes on the spar side of the hinge. Folding it over on itself, I marked the holes though to the trim tab side of the hinge (black marker dots on the left), then used this as a centre line (black) for plotting my holes on that side. I decided to offset them 20 mm from the spar side (blue tick marks)
Flip the elevator back over for viewing and dry fit of hinge to confirm safety wire hole is accessible AND viewable, both for installation and for routine pre-flight checks. From here I removed the hinge again and drilled out the A3 holes on the trim tab side of the hinge as marked.
With the bend width confirmed, I used the bender to create the trailing edge bend. It's tight and the bender can only bend so far over. From here, a 2x4 it used to lean on it and bend it further down to match the first. This picture clearly shows the long side of the trim tab will extend well beyond where it should - just like I planned.
With it close to coming together I flipped the entire thing over and secured it to the bench. This gives a much better view of the planned overhang. A quick sharpie line down the length gives a good line for trimming away the excess.
I drilled both ends of the trim side of the hinge to the trim tab and one in the middle for good measure. With it clecoed together in these three spots, I ressembled the hinge halves, clecoed it to the spar/skin side. Next, I proceeded to drill the rest of the trim side of the hinge to the trim tab using the previously drilled holes as a guide.
Took the whole thing off the elevator (again) and used the duplicator to match the holes on the overlap trim tab skin. I love this tool!
With everything clecoed together again, I checked the movement - nice and smooth and no binding.
With everything good, drilled everything out to A4 final size
Voila! (gratuitous happy moment capture)
With a few more minutes to spare, I decided to put everything on the bench again and line it up. Before doing that, I made the modification to the centre hinge plate that will allow the elevator nose skins the room needed to move up and down. I also trimmed the nose skin slightly to avoid any interference with the centre hinge support bracket.
With everything lining up and measured correctly, and confirming the whole assembly is flat and level, I marked out where the centre hinge bracket meets the elevator hinge spar bracket. With those marked where they meet, I took them off their respective assemblies for drilling.
I started with an A3 hole which will be enlarged to the correct size next. Holding it together with an A3 cleco, I confirmed they won't interfere when the elevator pivots up and down.
I stopped here, because when I was reviewing the plans, I have concerns about the size and type of the bolt used as the hinge pivot. The plans call for an AN3 bolt and vinyl insert lock nut. Not only does this seem awful small diameter, I believe it would be wiser to up-size the bolt diameter to an AN4 bolt and use a castle-nut and cotter pin to secure it. This mod is an improvement, I'll have to do some research what size bushing that will require.
Very happy with what I've accomplished so far. Next up is finishing the elevator/stab connections and fitting the servo and trim actuator rod.
Thanks for reading :)
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 :)
Husband, father and 911 dispatcher. Long time pilot with a licence that burns a hole in my pocket where my student loan money used to be. First time aircraft builder. Looking to fly my own airplane.