With both the wings into going into storage, I added the fuel tank drain/test ports. I need to make sure that nothing can get into the tanks while they sit in storage, and the any openings on the wings, like the lightening holes at the root have been covered up with tape and plastic to prevent bird or mouse nests!
First time in a very long time the bench has been completely clear of wing stuff! Time to start laying out the fuselage skins.
Had a couple of minutes one afternoon after work to finish one of the horizontal tail fuselage bulkhead frames need for the fuselage:
The plans are a bit deceiving when looking at the them when scaled down from full size. Close attention shows that the four corners of the fuselage aren't actually directly straight - the fuselage tapers very gently from the back of the cabin to the tail along all four longeron corners.
I've been pondering this for a while and when I was at the Zenair factory in Midland buying my longerons last month, I asked Nicholas Heintz (Chris' son) what would be an acceptable way for a scratchbuilder like me to make the correct tapered curve of the skins (the longerons curve to match the skins and are pre-cut in the kit versions).
Nicholas said the taper is very subtle and I should just connect the measured points out from the centre-line as shown in the plans. As long as the taper is equal on both sides of each of the four fuselage skins, all would be acceptable, but the taper is important as it provides some longitudinal rigidity to the fuselage..
Apparently that's not good enough for me! I wasn't confident that each 500mm point would give me enough points close enough together to draw through to make the gentle curve. So I grabbed the plans and entered them into CAD, like a lot of the templates I've made.
CAD has a great "spline" tool that is like using a draughtsman's French curve ruler to average out the points in the plans to establish a smooth curve. Then I used tools within CAD to section each of the 500mm sections on the plans into 100mm smaller sections, then measured where the points along the curve so I could transfer this onto the aluminum. Enough points along this curve means I can connect them with a real French curve ruler and have my taper drawn correctly on the aluminum sheet.
Here is a snapshot of the fuselage bottom skin, half way through the sectioning process in CAD:
The fuselage skins are all 0.020 thick, with several doublers between the longerons laterally and diagonally to stiffen everything up. The bottom skin is laid out on the table and I used the long straight edge to draw the centreline from which the edge points will be measured:
I measured out each of the sections lines along the centre-line, then used a square aligned with the long straightedge to plot the section lines out the edge of where the skin will be. I soon realized that Nicholas was probably right, curves based on the 500mm sections would probably be enough, so I decided to divide the sections into 250mm sections instead. This is a good compromise and accurate enough for me to make the taper correct using the French curve ruler we have.
This picture shows the lateral lines drawn out from the centre - the circles are where the curve of the edge of the skin will be and the lines from circle to circle are the skin edges which will be trimmed later. From there, I laid out the lower hatch door opening (often called the hell-hole) and some of the other lateral lines for the stiffeners, diagonal "L's" and torque tube bearing channel (supports the control torque tube):
A 10mm line scribed inboard from the edge skin is the rivet line where the skin will be fastened to the longeron once the skin sides are trimmed. This picture is the tail end of the lower fuse skin.
The lower fuse skin is actually too long to fit on a full 12 foot sheet of aluminum, even if I "tilt" the lower skin outline on the sheet, so a lower rear skin is added - it becomes part of the horizontal tail "box" and further strengthens this part of the fuselage to support the tail structure. Aligning it on the centre-line at the proper location ensures the lower skin is the correct length from the cabin to the rudder supports. Here it is temporarily clecoed in place:
Z-channels are added around the sides and rear of the lower hatch. These still need to be trimmed, I just wanted a rough idea where/how they interact with each other and how the rivet spacing should lay out. The square of cardstock is a quick cut out for me to use to visuallize where the flap motor will mount - again for rivet spacing, etc.:
Cutting out the access hatch was fairly easy. I used the fly-cutter to shape out the corners:
Then connected the edges of the circles and cut out the hatch. Some filing and sanding to take care of some rough edges and the access hole is done. I'll make the hatch cover from some of the left over 020 of the top skin.
I finished (for now) the bottom skin. All the rivet lines are laid out and drilled. Before I cut the bottom skin out, I've rolled it back up as as full 12x4 full sheet. Much easier to store.
Returning to CAD, I sketched out the two side skins and the top skin - this time with 250mm sections. It worked so well with the bottom skin, this will be the path to obtain the tapered curves for the other 3 sides of the fuselage (these are snapshots from CAD, not scaled together):
The top skin is somewhat shorter in length than the bottom skin, so I can comfortably "tilt" it on the aluminum sheet to save wasting some of the sheet.
Same layout method as the bottom skin. This skin has a flanged hole near the tail - this is where the elevator control cables will pass through the fuselage into the vertical tail assembly. Cut it out using the fly-cutter. I'll flange it later once the skin out cut out form the sheet so I can clamp the flanging dies easier (can't reach the hole now):
A second hole is cut near the tail end. This will form the round end of the channel as laid out by the lines drawn rearward from the circle to the rear skin edge:
Now onto the part that has been keeping me up at night.
We don't have the ability to bend complex shapes such as the upper top channel shown below. It's a slightly leaning C shaped channel, tapered at the ends that forms part of the wing spar carry-through on the top rear of the cabin. It is made of understandably stout 063 aluminum and both the shape and dimensions are critical to ensuring the wings mate to the fuselage at the right angle and location. So I ordered this from Zenith and picked it up the same day as the longerons.
Problem is, I hadn't thought it through and asked them to provide the channel pre-drilled, as they would in a kit. What I didn't consider is how to transfer the holes to the cover channel and doubler that make up the other sides of the top channel to form the spar carry though box.
I could order those pieces too, but when I spoke with them, they couldn't guarantee they the holes in the other 2 parts would be an exact match to mine as they drill them together at the time of manufacture, and mine was a one-of ordered part.
What to do. Start looking at order of operations and see if I can match drill the holes somehow, while respecting the bends yet to be made in the other two parts.
I can access some of the holes at the end of the top channel where it is cut diagonally to match the cabin uprights, so I placed the top channel in the proper position of on the top skin, drilled/clecoed the accessible holes form above into the skin. With that done and the channel secured to the skin in the right location I then duplicated the remainng holes along the bottom of the channel (actually the top when the skin is in place) onto the top skin because I can use the strap duplicator before the other pieces are added and drill from below the table level:
Unfortunately, as well as that worked, several of the holes on the channel are the bigger A6 river size rather than the standard A5 in the rest of the channel. Here is the channel lying on it's back. The 5 holes grouped close together are the ones I'm taking about. I don't know if an A6 duplicator is available, but we don't have one. These A6 holes are not accessible from inside the channel either.
Time to get creative.
I bent a matching piece of 016 to fit inside the channel and long enough to cover both the A6 holes, two inboard A5 and the A5 hole outboard holes and clamped it in place:
Back drilling through the channel into the 016 (using clecos in the three A5 holes to hold it together straight) and A6 size in the other holes gave me an excellent template to transfer to the skin that will match the channel holes:
Template added to skin, secured with clecos in the existing A5 holes, then A6 holes drilled through the skin:
I added more holes in the template from the forward facing A6 holes so once I have the doubler and channel angle bent, it too can be duplicated without having the access from inside the channel:
Fabricated and drilled the upper baggage area rear panel support angle to the upper skin:
This angle won't change once needed, so I finished all the river holes, deburred it and put it back into storage.
Next up was fitting and predrilling the upper fuselage top doublers. These doublers are almost like the shoulder blades of the wing/fuselage junction which transfers the loads back over the fuselage longerons and upper skin.
First I lined them up on the top skin and used extended lines from the top channel holes and the longeron rivet lines. Once in place, I traced those same river lines onto the doubler and laid out the rivet locations as per the plan. The doubler actually fits onto the outside of the fuselage, but laying it out this way allows me to see the lines before drilling through the doubler and the skin.
Once I was satisfied with the layout, I drilled pilot holes in the doubler on the drill press in the require locations, but not where the top channel lays. Then I back drilled through the doubler in 5 locations to secure it to the skin. The rest I'll drill once the longerons are in place:
Both doublers in place, secured enough for the next steps:
Shifted the doublers to their proper position on the outside of the fuselage skin (remember, I'm working on the inside of the skin and it's actually upside down on the table) and clecoede them in place from above. Then I placed the top channel back in place and secured it from below using the holes duplicated earlier in the skin:
I drilled the forst A5 hole and the two A6 holes I can access at the end of the top channel, then removed the channel and marked the others through the skin and into the top skin doubler:
Removing the top doubler and finishing the holes on the drill press, proves the matching worked (for some reason the picture below seems to show the holes are out of round, but it must be a shadow from the flash as they are actually perfectly matched):
I've also been scrounging a bit online on various marketplaces, classified listings and forums. Scratch building makes you keen to grab deals when they come up and I've been scoring well lately.
Both Ron and I want to make epoxy resin castings for our navigation light lenses and strobes. One of the tools needed to cast clear lenses is a vacuum chamber which is used to de-gas both the silicone molding mixture and the epoxy itself.
I spotted this complete set on Facebook from a seller not to far away. She wanted $125 for everything but I managed to get it for $100 just by asking. It's really brand new, she told me she'd only used it a couple of times but couldn't handle the fumes, so she was looking to sell it to someone who could use it. I looked it up after I bought it and there is easily $400 worth of stiff here, so I was a bit surpised she was willing to sell it for so little.
I brought it to the shop and tried it. Ah. It's not working, that's why.
The vacuum pump appeared to be pulling lots of pressure at the end of the vacuum line, but nothing was jhappening in the pot. Originally I thought maybe the valves were bad or something and I would have to replace them.
When I looked closer however, it looks like someone let the some casting epoxy get into the vacuum port on the pot lid, sealing it completely over! A quick drill and clean out of the port, freed up everything and it is working like new again. Score! We can also use this to de-gas paint for the planes too.
On the Zenith website classifieds, I spotted a suitable airspeed and altitude indicator. Used, but in excellent used condition, clearly taken care of by the previous owner. $200 USD for the pair - Score!
Another Facebook marketplace find were these cable turnbuckles, cable swivels, and throttle cable. Less than $200USD for everything - Score!
Ron continues to look for some parts for his Continental O-200 conversion for the Aeronca Scout rebuild. He bought a Cessna 140 for the engine, but it needed a new intake spider which was cracked.
These are getting very VERY hard to find as they often get damaged during prop strikes and need replacing. New ones are available, but cost north of $800USD!! I spotted one on Facebook marketplace, contacted the seller and managed to get this good used one and a box of other intake parts for $100USD shipped! - Score! I've given it to Ron as thanks for all his help with my build and his kindness in letting me use his shop. That's the kind of karma that I believe we need more of in this world :)
I'm getting close enough now that I need to consider what I need for my Corvair engine install with regards to firewall forward stuff.
I ordered my Corvair/Zenith installation manual as well as the MOP (Maintenance and Operations Procedures) manual.
They arrived in my hands and I sat on the dock the following morning looking through them. This build is always on my mind, even in the quiet times :)
More to come, thanks for reading along!
Happy New Year to my dedicated and loyal followers!
A bit of a slow start to 2022, but back in the shop for a few hours over the past few days. I'm still waiting on the fuel lines and fittings to come from the supplier, hopefully soon as I'd like to get them test fitted before I flip the wing over in the next couple of weeks to build up and fit the fuel tank in this wing.
While I wait for those to arrive I got the backing strips epoxied to the inside of the wing tip. EcoBond epoxy is spread thinly on both sides and left to set up for about 5 mins:
The 016 aluminum backing strip is clamped in place and left to set up. I leave these overnight and have no problem with them bonding well.
A test fit to the outboard wing reveals little trimming to be done. I'll need to confirm the measurements of the other wing to see where the other wing tip positioned for final fit and make sure this one is in the same place making the wings symetrical.
My push-connect unions came in from the supplier. If you are familiar with SharkBite plumbing fittings these work the same way. I'll be using these to connect up the pitot-static lines once the wing is flipped over.
Long time readers will recall the genesis of this entire project was largely credited to the mentorship of my friend Captain Barry Morris. When he passed away suddenly in Sepember 2015, I made it my mission to get working on this project and not wait for it to just come to me (see my earliest blog posts for more).
I've been in regular contact with Barry's widow, Linda Morris since his passing and we've shared many memories, laughs and tears. She gave me the honor of gifting me a damaged wooden propeller that belonged to Barry that he "acquired" and had cut down to a "trophy" of some sort. I wish he was still here and could share how this prop came to be, but somewhere in his adventures it came into his possession and I will treasure it forever.
For Christmas from Brenda, I was surprised to receive a hand made clock insert for the prop. Here is a picture of it installed. The words scribed on the face mean a lot to me, it is in a prominent position in our kitchen where I see it every morning:
Next up in the shop are fuel tanks and today I'm working on the design of strobe/position/nav lights for the wings among other things. Now that I have finalized the controller design, I want to test some higher power LEDs that I found on Amazon and see if I can really make the lights punch it out by boosting the voltage up. Also pondering lens design using clear casting resin - all in with experimental right? I'm NOT paying over $500 for what is currently offered on the market for lighting solutions.
Stay tuned, more to come.
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? :)
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 :)
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 :)
Getting close enough to getting the 701 wing completed, it's time to start planning the rest of the tail group on my 750. That means ordering some aluminum!
I called the supplier (Aircraft Spruce Canada) and ordered all the 016 I need for the entire build, a sheet of 025 to replace what I've used from Ron and some elevator trim tab hinge. The plan was to go last weekend, but the huge storm that dumped on southern Ontario precluded the trip so instead we loaded up the truck and headed south this weekend.
We arrived in Brantford and convenient for the girls, an equestrian riding store is about a kilometer away from ACS. I dropped them off and headed to ACS to pick up my order and some items for Ron.
The staff at ACS are fantastic - I had asked them to roll the aluminum as small as possible in order to fit it under the tonneau cover of our truck and keep it out of the winter weather. They are masters!
In addition to stopping at ACS, I had been in contact with another 750STOL builder in Burlington - Ghazan Hieder. Ghazan has been slowly working on his kit for about 10 years and self admits that any upgrade that comes out from Zenair he buys, so when edition 3 cabin changes were announced, he bought the plans and updated parts, making some edition 2 parts available. He had advertised on the Zenair Builders website he was giving away an edition 2 cabin frame and windshield, so I made arrangements to meet up with him while down south to take possession of these two valuable items.
He was glad I called as he had hoped to find another builder who could use these items - and I was glad to take them off his hands. All the research I could find shows only minor modifications need to be made to the cabin frame and the windshield is another easy mod.
Ghazan also offered me an early edition nose wheel fork and nose strut - he'd replaced his with Viking steel spring mod, something I'm considering too. If I can't use the strut he gave me, it will work for one of Ron's 701 builds.
Brenda helped me load everything into the truck as best we could, but we decided to put the windshield in the back seat until we could work in the daylight the next morning.
With better lighting, it was easy to pack everything safe ans secure. I borrowed some moving blankets from a buddy and laid them out in a way to protect the plastic edges of the windshield and the sharp edges of the cabin frame.
Getting it home safely worked really well, thanks to Brenda's amazing packing skills!
Unpacking it all at the shop, here is a better look:
Needless to say, I am truly thankful to Ghazan for his generous donation. He could have just tossed these away (frankly I'm surprised no one else came forward to take them) but he didn't - he just wanted someone else to use them on an airplane. Estimates are hard to nail down because I have no idea what this stuff would cost to ship, but conservatively? I saved about $800+ by picking up these surplus (to another builder) parts!
One of the coolest things I've learned about the homebuilding community is how keenly interested everyone is in other people's builds and more importantly successes. I have or am learning the skills to make these work for my build and that works for me, whereas Ghazan is happy to build from a factory kit. Either way we share a common bond - dream, build, fly!
Thanks for reading!
Yup, I said it..... no, I can't speak german... thanks Google translate.....ha ha!
The Corvair authority William Wynne talks extensively on his blog about different carb applications in a Corvair conversion and the importance of keeping things simple.
The dual (and sometimes quad) factory Rochester carb setup on a Corvair car engine not only complicates matters (syncing throttles arms, etc) they were never designed for altitude compensation and mixture settings required in an aviation application. The converted Corvair engine falls into the same horsepower range roughly equivalent to typical medium Continentals and Lycomings, approximately 100 to 120HP. This requires a fuel delivery system capable of delivering an air to fuel ratio capable of supporting this demand.
Fuel injection? I believe the advantages (no carb icing, small increases in HP) are FAR outweighed by the complex system components (injectors, return fuel lines, pumps, electronics, sensors, etc). Keep it simple.
The MA3-SPA carb as found on the O-200 continental and O-235 Lycoming is the definition of simple. They haven't changed much since the 1940's and Marvel Schebler continues to make new ones today - in other words it works, simple. Overhauled to new specs it's the perfect carb for my conversion.
Finding one that is both inexpensive to obtain and overhaul becomes a problem due to this popularity. A good core for rebuild can be found in the three to four hundred dollar range then count on six to seven hundred dollars to overhaul it. Expensive, but not an area I want to save money on - engine reliability is important in flying! The recommended overhaul shop (D&G Supply in Michigan) also will convert specific O-300 carb models to the Corvair specifications.
Armed with this knowledge, I've been searching online for a suitable core.
A couple of weeks ago while surfing E-Bay, I came across a listing for an O-300 Marvel Schebler carburetor that would be suitable for my engine. It's clearly an older one, but again the model number matches the acceptable models for conversion and the pictures showed well.
Like anything on E-Bay, Kijiji or Craigslist it's a buyer beware mentality. One has to consider the odds and what it's going to cost to ship. In my case, the core I was interested in had no reserve pricing but the shipping costs weren't cheap - it was in Germany! This compounds the pricing with the Euro being somewhat strong against the Canadian dollar. Worth a shot.
With this in mind, I did the responsible thing and figured out my maximum bid would be about 100 Euros. I watched the days count down and was pleased to see my bid of 40 euros was enough to win! With shipping and currency conversion the total costs came to $112 Canadian. Not bad and certainly better than what I expected to pay for a core.
"Mein vergasser ist angekommen" (which means "my carb has arrived") on Friday and I picked it up at the post office yesterday. My first look had me really worried as the box had a crushed corner and was split open at the top:
There was a sticker on the box from Canada Post stating the box was damaged by the forwarding shipper. Not good. One of the fears shipping any item overseas or otherwise is theft. Hope there isn't just a bag of sand in here!
Opening the box, I smiled a bit finding a note from the seller:
Opening the box further, it came apparent that the shipper used a lot of bubble wrap to protect the carb on it's journey, but more importantly there is a carb inside the wrap!
It's definitely old, but everything seems intact and the throttle/mixture arms move freely. The accelerator pump seems seized but that's typical of something that has been sitting on a shelf for a long time and that will be repaired as part of the overhaul.
The data plate is intact and shows this is a model 10-4895 MS carb, typically used on O-300 engines. This is a good carb for overhaul and conversion to the required specs for my Corvair!
Glad I found this. It will be sent for overhaul this fall.
Back to the shop soon.
I made some excellent (small step) progress on my airplane build this past week.
Before I get into details, I want to share a bit of scrounging advice. Don't ever be afraid to ask around when you are looking for something, be it materials or tools.
While building, Ron and I often get to talking about ways to save on costs. One of the things that costs a bunch of money when getting it done by others is powder coating parts. Powder coating is a dry finishing process that gives various materials a durable coating that can be much tougher than paint alone. It's particularly good on non load bearing parts that may be handled regularly or exposed to friction. Control columns and rudder pedals come to mind.
Powder coatings are based on polymer resin systems, combined with curratives, pigments, and other additives and ground to a fine powder. A process called electrostatic spray deposition (ESD) is typically used to apply the resin to the metal substrate. The process uses a spray gun which applies an electrostatic charge to the powder particles which are attracted to the grounded part. After application of the powder coating, the parts enter a curing oven where, with the addition of heat, the coating chemically reacts to produce long molecular chains, resulting in high cross-link density.
That's the long way of saying "it sprays on and sticks really well after being cured in the oven".... ha!
Ron and I both figure the majority of the parts we might want powder coated should be able to be done ourselves. Ron has a source for the powder coating gun and resins, we just need an oven. Baking resins can generate a fair amount of unpleasant fumes, so we won't be using the kitchen!
I've been real fortunate over the course of the last few years to have several people I know come to me with leads on "airplane stuff" and I owe a bunch of that to talking to everyone I know about my project and plans. Opinions regarding my sanity range from "wow, that's cool" to "you are bat-s%$t crazy dude!" However, even if the vast majority consider me closer to the slightly crazy side of the scale, they do come to me when they hear of something.
In this case, when I mentioned that we were seeking an oven, Brenda noticed a Facebook post from a friend of a friend who was remodeling their kitchen. Turns out they were giving away a built in Jen-Air oven! Free! Brenda messaged them, I hopped in the truck and 10 minutes later, it was in our possession. We really don't need the stove top portion for baking parts so this is perfect:
We'll build a simple stand and wire it for power. It will require some calibration tests to ensure the temperature settings are accurate as they need to be for the powder coating. Not every oven is created equally as far as accuracy is concerned and oven temperature can drift as much as 25 to 50 degrees over time.
As for my airplane, I started to put the templates I made to use and traced out my first parts with them.
They worked real good. A thick Sharpie marker leaves a good line for rough cutting:
Before making the rough cuts of individual pieces from the sheet, now is the time to drill the corner relief holes where reuired. Here are some that I remembered to drill before cutting them out. Much easier to do this before hand I've learned!
Once the parts are rough cut out (thicker pieces on the bandsaw), further fine cuts are made using hand tools. By always leaving a bit of the thick marker line, we can see where the part will be trimmed down with the grinder, a file or hand sanding when taking of the burrs.
I made several parts over a couple of hours:
I took a good idea from Ron and taped the template to the parts when they were done. That way I don't have to write the part numbers on the aluminum. These completed parts will be stored until I need them later. I'm keeping a massive spreadsheet to track parts made, where they are stored and what inventory of materials I have on hand:
I know I have a TON of parts still to make, some simple, some complex.... but there is something so motivating about making these first parts for my 750 that makes me want to be in the shop full time. Unfortunately without spending at least some of my waking hours at my paying job, I can't afford the materials to make parts, so I guess I'll have to get back to the shop when I can.
Next up, further repairs to the 701 wing and I'll finish the sub assembly parts I need for the tail group on my 750!
Snuck over to the shop for a couple of hours Monday morning. I'm trying to squeeze in time when I can and a few hours in the morning before I head to bed for my afternoon pre-nightshift nap works perfectly.
Work continues on the 701 wing repair/rebuild. I managed to fabricate my first replacement piece, a rear wing channel. It took some time to figure out how to use the sheet metal bending brake, but I got it done. Here you can see the original bent and mangled one on the right and my new one on the left. The previous builder for some reason made his channel with a thinner gauge of material than what the plans call for. I'm all for saving weight and money, but this is a critical structural component, not something I would consider worth skimping on:
Next was removal of the damaged nose skin. As part of the repair/rebuild, Ron is planning on extending the wing by a couple of feet. We'll cut out the damage, fabricate a tip extension to the main wing spar and add a rib where required. A new nose skin and upper/lower wing skins and will be cut and fastened to the originals. Of course, this means drilling out more rivets. I suspect there will be times this will come in handy when I make mistakes on my own build!
This picture shows the extent of damage. What do you think..... is this creased too far to be "popped out"?
I drilled out the rivets on the closest good rib to allow some flexibility when cutting the bad nose skin. We'll trim it cleanly back to the rib to enable a clean joint with the new extended skin. These empty holes will become part of the stronger joint as a result.
As always, I'm keeping my eyes open for good deals on things I need for my project. Surfing the classifieds section of the Ultralight Pilots Assocication website, I came across an individual selling a complete rudder section for a CH750 for an amazing price that was too good to be true! A quick game of phone tag and the seller and I agreed to meet on Friday this week.
On the road again..... can't wait to get on the road again.....
Previously on part one.....
Without the resistance of the blower fan and suction of the vacuum filter assembly, this motor spins way faster than what the label states. So fast in fact it wants to tear itself apart while merrily dancing across the shop floor despite being mounted on springs (or maybe because it's mounted on springs?)
So, I need to figure out a way to slow the motor down or reduce the vibration component.
My first thought is to reduce the size of or modify the shape of the metal strip I added to the motor axle.
I think doing this only reduces the vibration. The motor will still be spinning way too fast and determining the right size of strip may be hit and miss to get exactly right.
How about controlling the motor speed? I think this will be the easier route.
Digging through my box of household electrical stuff, I found two incandescent dimmer switches that should work. They are designed for AC power (as is the electric motor) and this would add the ability to fine tune the vibratory effect for best results.
Before that however, I need to finish creating the parts bowl. First I inverted the bowl and traced a circle on a piece of spare lucite (plexiglass):
Cut the circle out using my bandsaw...... that's when I realized the centre section of the bowl sits above the rim:
To secure the new lid, I used a piece of hollow threaded rod. I screwed it into the top plate of the tumbler and l left it long enough to add a cap to hold it down tight to the bowl:
To hold the lid, I found an old powder scoop that fits perfectly over the bowl centre. That and a washer and nut hold everything down nicely:
Now that everything is built, back to slowing down the motor.
I added in the rotary dimmer switch. It has an off position when turned counter-clockwise all the way. I'll tide up the wiring once I figure out if this is going to work as designed. The picture was taken prior to creating the lid. Using the dimmer works!
Time to test the machine....
First, add the tumbling media, in this case a couple of scoops of clean clay cat litter. Then add some dirty, greasy and rusty test parts:
Close and fasten the lid..... all secure and "go for power-up!" The vibrating of the tumbler makes it hard to get a clear picture, but the media very quickly envelops the parts. As it tumbles, they occasionally come back up the top:
The tumbler is NOISY! I suspect the bolts between the levels of the tumbler are vibrating against the bowl. That should be easy to fix. Perhaps it might have to be run outside. After letting it run for about five minutes, I decided to have a look at the progress. Even after only 5 minutes, the parts are obviously cleaner and devoid of the grime they entered with:
Although the parts come out a bit dusty, clearly this method and machine I've built works very well, even at a short duration. I'm planning on running a longer test this afternoon and will post more details.
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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.