Race - the answer is Race.(not sure at my current pace what place I'll come in, but still progressing).
Although things are still progressing on the plane, there isn't much to share that you haven't already seen. This wing is obviously a mirror image of the first, with very few differences that are yet to be addressed. I've also been busy with projects outside of the build which have kept me away from the shop more than I would like. Summer is coming to a close and winter is not far behind, so more shop time is likely (I hate the cold of winter.... maybe hate is too strong a word but whatever).
With the rear channel now in place and riveted to the rest of the skeleton, I took the upper skin off for debur and to check and rivet the main and nose ribs.
It pays to double check every thing. On the inner wing tank rib, I "figure eighted" a hole when back drilling the upper root skin. It's easy to do, just was very disappointed to make this mistake.
I originally planned to replace the entire rib, which would mean starting from a blank, forming the rib on blocks, cutting and flanging lightening holes, the works. Not to mention removing the damaged rib from the skeleton by drilling out the rivets, etc. In consultation with Ron, we decided a doubler L epoxied to the inside of the rib flange would be a suitable and easier repair. That took a couple of hours to make up, but the results are strong and acceptable - also much better than making an entirely new rib!
Drilled out the tie down ring and match drilled it to the nose rib:
Upper wing skins final riveted to the ribs. When I flipped the other wing over, I noticed the square tubing left scuff marks on the skins despite having masking tape on them. I decided to mask the skins where they will contact the tubes when this wing is flipped over to try and alleviate the issue this time around:
Flipped the wing over on the bench and squared everything up with a level (pic is before levelling):
With the spar now perfectly vertical and the skeleton evenly supported from below, I laid out the rivet line in the lower main spar using the shop LONG straight edge. Also rivetted the nose ribs to the spar:
Pulled a fresh 12 foot roll of 020 and cut out the inboard lower skin. Rolling it out on top of the skeleton it was nice to see a good square fit on the wing frame:
Flash forward a bit, the lower skin is in place, as are the flapperon arms and requisite slots in the lower skin:
The outboard lower skin was next.
Outboard lower skin complete with stiffening L. Trimming the end to match the wing tip will come once the wingtip is fitted:
All ribs and lower skin drilled out to A4 with the exception of the lower root rib:
Way back, I made up 2 root rib splice plates while I had a couple of scraps of 025. I put them away in my bin for when I got to the wings but apparently I lost track of them. When doing the first wing, I had forgotten them so made up the one I needed at the time. Low and behold today I found the pair I made way back when. Today I added the second one. That's the way it goes with scratch building and small parts I suppose.
Pulled the flapperons/skin support angles, slat supports/support angles and the root rib doubler from the skeleton, deburred them and cleaned them up for priming:
Grey self etching primer complete, these parts will be riveted to the wing soon:
Progress is progress, even if slow. Thanks Mr Tortoise for the valuable lesson.
More to come including debur of the lower skin and fabrication of the pitot/static probes. Thanks as always for following along :)
It's been a while since I posted, but progress continues on both wing spars. As I stated previously, I want both main spars complete and ready for ribs before starting to add the other wing structures. The wing takes up a substantial part of the work area, so the left spar when complete will go to storage while I build up the right wing. Once the right wing is skinned, it will swap into storage and I'll build up the left.
All the bucked rivets in the right wing spar are done, so it was time to final hole drill the left wing spar in prep for debur, prime and final reassembly.
This picture was taken around Halloween. The black A5 clecos and copper (orange) A4 clecos reminded me of the season!
Unfortunately, one of the holes in the spar web doubler came through very close to nicking the spar cap. Thankfully it didn't, but this will make it impossible to have enough clearance to drive the rivet with the bucking gun. Solution was to drive the rivet from the other side - not ideal, but perfectly acceptable according to the build standards.
With all the holes now complete, it comes all apart for debur, prime and reassembly.
When I was reviewing the drawings, the question of dissimilar metal corrosion (called a galvanic reaction) came to mind. Galvanic corrosion (also called bimetallic corrosion or dissimilar metal corrosion) is an electrochemical process in which one metal corrodes preferentially when it is in electrical contact with another, in the presence of an electrolyte. The electrolyte in this case can simply be environmental humidity. Salt water exposure would be worst case scenario.
The aluminum spar attachments are made of aluminum. The connection points on the struts and front of the cabin frame are 4130 steel. I did some research on the forums and it seems most people just ensure they have good prime/paint on both parts and/or powder coating on the steel parts.
So what does the aerospace industry do? They anodize their parts.
Anodizing in the simplest of terms is a process of increasing the thickness of the natural oxide layer on the surface of a metal part. This thickened oxide layer renders the part non-conductive electrically, thereby preventing galvanic reaction with other metals. The anodized aluminium layer is grown by passing a direct current through an electrolytic solution, with the aluminium part serving as the anode (the positive electrode). The current releases hydrogen at the cathode (the negative electrode, either lead or aluminum) and oxygen at the surface of the aluminium anode, creating a build-up of aluminium oxide on the part.
This doesn't however change the dimensions of the part as the layer is nano-metres thin.
Sounds complicated, but is actually simple enough to do in the shop. There are literally dozens of YouTube videos online showing different methods for doing this. Many home hobbyists do this when making parts for their car, computer cases, flashlights etc.
I managed to find a good article in KitPlanes magazine which was simple enough I thought I'd give it a go for my strut pick-ups and spar attach brackets. In the end, if it it didn't work, I can always just prime and powder coat where necessary. The over-riding mantra of my build is to learn, so this is something worth trying.
There are several components needed for the home anodizing process, which I'll try and detail here in pictures.
I scored a small aquarium air pump at the thrift store - 2 bucks. A new piece of air tubing for $3 and a air-stone for making bubbles in the electrolyte $5 from the local pet store. The purpose is to agitate the electrolyte, essentially circulating the solution as the process happens.
Distilled water which makes up the majority of the electrolyte solution. A thrift store kettle for $5 - I should have bought a larger one as the parts once complete need to be boiled in distilled water for an hour to seal the anodizing coat (more on this later). Baking soda to neutralize the electrolyte bath acid and also to contain any spills.
The main electrolyte bath tub.
The main rinse/neutrailizing bath - warm distilled water/baking soda solution:
My electolyte bath is a 10% solution of Muriatic acid and distilled water. I followed the measurements closely and all the warnings of adding the acid to the water slowly. Never add water to acid - always acid to water. The thermal reaction is easier to control by adding acid a little at a time - it can be explosive if you do it the other way around! Pay attention closely to the instructions. Muriatic acid is nasty stuff, so wear gloves, goggles and breathing mask. Make sure to use a well ventilated area.
Before the parts can be anodized, all residual oils, markings and natural corrosion must be removed. The easiest was to do this is using household amonia. Again, proper gloves, googles and respirator mask - this stuff is hard on the eyes.
I proped everything up on some bent metal strips to allow full circulation around the parts. The parts sit in the bath for a while.
For the negative plate in the anodzing bath, I used a piece of scrap aluminum sheet that had too many dings/creases in it to be useful for anything else. I cleaned it with lacquer thinner and made sure it was completely dry before bending it to shape inside the acid tub. The more surface you can expose to the bath and parts the better, so it's bent up both sides of the bath.
Checking back on the ammonia bath, the parts are starting to bubble - a good sign that any contaminants on the surface are being lifted away. I don't have any pictures, but once I was satisfied they had soaked long enough (about 30 mins), I used a clean 3M scrub sponge to wipe them down, then a spray bottle of distilled water to rinse them off. A good indication that the part is completely clean is when the water spray refuses to stick to the aluminum and jut flows off. Water beading on the part means contaminants remain. Mine parts just flowed the water freely. It's important to not touch the parts at this point without clean gloves as any natural oils on your skin will contaminate the part again.
As the parts are left to air-dry, I prepared the anodizing tub. I connected the negative lead from the power supply to the aluminum plate in the tub (the cathode).
The process is hard to capture, but the next steps are to hang the parts in the electrolyte acid bath from aluminum wire. The parts need to hang freely, not touching the other parts or the cathode. The positive lead from the power supply is connected to the parts via the hanging wire. The circuit is now complete and the power supply is engergized. The airpump is also turned on. The following pictures are of the anodizing bath well underway. The electrolyte solution is fairly cloudy by this point, making it hard to see the parts.
The voltage and current applied is calculated with an online tool, using the total square area of the parts to be anodized and what thickness you want the anodized layer to be. This gives you the starting voltage and current and how long the circuit needs to run.
As the anodizing takes place and the oxide layer builds up, the current slowly diminishes to almost zero as the parts no longer can conduct the current. A good indicator other than the readings on the power supply is the distinct reduction of bubbles coming off the parts.
Very close to the time to shut off the circuit, the bubbles coming off the parts took a dramatic downturn as expected. I waited for the time to run out and stopped the power to the circuit and the air pump. The parts are carefully lifted out off the acid bath and immediately dunked in the soda bath to neutralize the acid on the parts. With gloves on, sloshing the parts around makes sure the acid is fully removed from the parts. Once satisfied the parts are "neutral" they get boiled in fresh distilled water to seal the oxide layer. It's at this step that some people add dye powders to the boil to colour their parts. Iwas thinking of doing this, but decided colour wasn't import as I was going to prime/paint the parts as well.
Overall the process of anodizing went ok and I learned a lot. In hindsight, I'm not sure it's worth all the effort when prime and paint will suffice. There is also anti-galvanic paint on coatings that they use in marine applications. I'll look into those as well. The complexity of the system and process turned out to be too big a distraction from acutally building. It would have probably been easier to send them out to an anodizing shop, so my foray into anodizing is over, but in the end I'm smarter about it now than I was.
With the left spar primed and reassembled, I finished bucking the last of the rivets in the spars.
The spar pick-ups have been primed at this point on top of the anodizing I did. I need to order some AN bolts to go with them and the strut pickups (should be here next week). They look fantastic!
With the spar now essentially complete, it is time to start lining things up to ensure the spacing of the ribs match the spacing of the slat and flapperon pickup brackets.
I stood the spar up and anchored it to the bench. I started to add the ribs temporarily using small clamps at the spar and masking tape:
With the ribs in place temporarily, I clamped the nose rib slat attach brackets. These are only in the lateral position for now to allow for lateral measurement. They actually sit up higher on the nose ribs when mounted.
I did the same for the flapperon brackets at the tail of the rear ribs. Preliminary measurements show that the slat and flapperon bracket positions are perfectly matched to the slats and flapperons. This allowed me to drill the pilot holes in the spar for the ribs.
Next up for assembly is the rear wing channels - an inboard and outboard.
I previously had these channels bent by a professional shop as we don't have a suitable bender available at this length. The inboard channel has a support angle across the top. I laid out the angle rivet spacing and drilled out to A3:
The inboard and outboard channels are joined by a splice channel at the rear strut pickup point.
I laid out the splice channel, drilled out the holes to A3 as per the plans.
With the holes complete through the splice channel and the rear channel, I laid out the rear strut pick up. The plans aren't completely clear on the placement, but with a little figuring I was able to confirm the placement.
I clamped the strut pickup in place to the splice channel and backdrilled through the splice channel, ensuring accurate line up of the holes for the entire assembly:
The rivet spacing is tight here and one of the holes is actually for an AN3 bolt. Before drilling the holes out to A5, I finished adding the strut pick-up AN6 bolt hole:
Moving the clecos to the underside, clears room to work with the drill to brig the holes up to A5 size. The far right row of rivets is where the tail end of a wing rib attaches through the channel and splice channel. I'm leaving them as A3 until I fit the rib. I'll have to decide if I want to debur, prime and rivet this section first, or wait until final fit up of the wing ribs.
I did the same at the root end of the rear channel. Lay out the rivet pattern, then back drill through the root plate (a .125 plate inside the channel) that supports the rear channel attachment to the cabin frame.
With the placement of the nose and rear ribs confirmed earlier, I could drill the remaining pilot holes in the rear channel for for the rear rib attach points. Until the wing ribs are in place, I'll wait to debur and prime everything before riveting. After this picture was taken, I drilled everything out to A5 size and trimmed the outboard end of the channel to length and taper (more on this later).
Before final layout of the wings, I decided it was probably best to confirm the work table was completely flat, so I cleaned it off completely. It still was very flat and required almost no adjustment. It was weird to see it so empty!
Making sure the spar is completely straight laterally, vertically and no twist is critical. This is accomplished by using the flat table as a reference. The right angle towers are placed at each end across the rear face of the spar and secured to the table. A tight string line between the outer uprights gives a straight line reference for the other uprights. My spar is straight in all dimensions.
The camera shot give the impression this is far from vertical. It is, confirmed by inclinometer - the view is an optical illusion.
With the spar completely vertical and straight, I started to add the rear ribs. I back drilled through the spar web and into the rear rib flange, using an upright bubble level to ensure the rib was square up and down.
Very happy how this is going. The ribs are a perfect match to the spar. Once I have all the rear ribs in place, I'll remove them one at a time and repeat the process for the nose ribs one at a time, back drilling them through the rear of the web.. This will ensure they too are lined up exactly correct.
Lots to go on the wings, but they are starting to come together. I'm back to Monday to Friday schedule at work, so I should be able to get to the shop more regularly, perhaps one or two nights a week and a full day on the weekend. Hopefully my blog will keep up!
Thanks for following along.
So, a lot has been happening in the world in the last week or so.
The Novel Corona virus, better known now as COVID-19 has seen exponential spread across international borders from it's origins in China. Unless you have been living under a rock or are reading this blog in some distant, future archive (thanks by the way!), news and anxiousness is rampant about what is now officially declared a pandemic. People are scared, some more than they realistically need to be and world financial markets are feeling the squeeze.
Mandatory closures of schools, businesses and government facilities are becoming commonplace as we work to "social distance" ourselves from others. Large groups, social gatherings, events and meetings are highly discouraged if not outright banned Efforts are underway by people everywhere to prevent the spread of the virus and protect those who may not have the benefit of good health and the ability to fight off this particularly nasty bug - it can and has been shown to be fatal. Unfortunately there are those ignoring common sense which is leading to more anxiousness and unease. This has even lead to a very strange phenomenon of the panic buying bulk toilet paper!
I've said before how much my shop time is my happy time. It's my place to decompress from my emergency services job. While a good portion of society has been told to stay home from work, my colleagues and I continue to work shifts in a busy 9-1-1 communications centre and although the calls for service have yet to peak as I think they will, we are an essential service and will continue to come to work and answer the calls. It's scary but I think we'll come out the other side of this craziness better off as a society from the lessons learned.
So, what better way to practice "social distancing" and "flatten the infection rate curve" of COVID-19 ng than to get to the shop and work on my build! Here's what's happened since my last blog post.
A couple of weeks ago, I traveled south to visit Dad and made a side trip to Princess Auto and Aircraft Spruce for tools and hardware. I needed an inch/pound calibrated torque wrench and was happy to find a good quality one on sale - score!
I stopped at Aircraft Spruce and picked up my online order of the remaining aircraft hardware I need for the build, other than some back-ordered nut plates and stainless machine screws. Obviously this isn't everything I'll need (the interior will require some fabric fasteners etc), but what you see in the picture below is the lion's share of bolts, nuts, washers and cotter pins called for in the plans.
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!
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 :)
Not a huge update, but a few things to mention this week.
Ron and I got further along on the 701 wing repair the last two weeks. We are being really challenged by the mistakes of the previous builder's measurements and decisions on what was "good enough". We've compounded that by adding the wind extention, but we are getting it figured out.
The flap extension to match the new wing length is coming together nicely. Because this is an add on, wrapping the short flap skin is certainly fun...
Once we get the flaps skinned we can fix the spacing of the flap brackets. As most things on this repair, nothing is consistent, even between both wings. Having the flaps apart allows us to adjust where they meet the flap brackets. Make it right has been the goal all along.
The days lately have kinda blurred together with my new position at work, but I'm certainly not missing the shift work that's for sure. It has made it somewhat difficult to focus on my project, but things will improve soon as I adapt to my new job and this Monday to Friday schedule. What hasn't changed is the feeling I'm doing something great when I do get to the shop, even if Ron and I spend the hours just jawing about airplanes and flying.
I've long been following the online musings of William Wynne, the Corvair expert I've mentioned before. He wrote the following quote on his blog the other day and it really struck a chord with me:
“Hours in the shop working with your own hands cleanses the part of your sanity which modern life soils”
Indeed William.... indeed :)
It's safe to say that any flying machine is a collection of parts that are strategically placed and assembled to enable one to fly.
Although this is true, it's the little things that get accomplished over the course of a building project that make the difference in not only getting the plane built, but improves the overall quality and performance of the end product. It also contributes to the philosophy I spoke of last August on my blog: ( a-little-here-a-little-there).
Today I decided to pull out the Corvair heads and have a closer look at them.
You might recall that these heads are 110hp versions from a 1966 car. They are just as I received them from the seller - not filthy but certainly not clean either!
Any engine that is more than 50 years old is bound to be grimy. Air cooled engines like the Corvair have many, many cooling holes factory cast in between the head fins. Being small, they trap everything. Not good as the GM engineers counted on these being clear for optimum cooling. What the GM engineers didn't consider is that casting aluminum or other metals sometimes leaves "flash" where the moulding halves join up during the casting process. Either it was considered to costly to remove the flash or maybe they decided it was good enough. What I have experienced however is the massive range of acceptable "flash" tolerances - some heads have so much the cooling holes are almost closed over. With a small amount of dirt in there, they are effectively closed to cooling air.
Here is a look at the cleaner of the two heads. I've put a lightbulb behind to ease the viewing:
As you can see, the cooling holes are many and this head seems quite good. Some minor flash to clean up but generally good.
The 2nd head, despite being from the same casting lot as the first is terrible! I could only find one hole that was clear and even then it was almost closed over from flash:
Took an hour with a combination of small files and old steak-knives, but I managed to clean out the majority of the gunk from the cooling holes.
Both heads really do need a good pressure wash before I'll be able to remove all the flashing, but this was a good start. Removing the flashing is very important and goes a long way to improving cooling of the heads.
It's these little things that take time, but make a world of difference and counts towards the goal. Along those same lines, my father Jim and I have been working on an important submission regarding my mentor Barry. I don't want to say much yet but it's a little thing that also counts for something. Stay tuned for more on this shortly.
I had every intention of spending the entire day in the shop today. I'd taken the time last week to mark specific "shop days" on the calendar - days that are set aside for the shop and my build. A discussion with Brenda and our girls regarding my build led us to an agreement that these days are next to untouchable on the schedule so that I can make real progress this year. Obviously if something special comes up that can't be scheduled somewhere else my shop day can be compromised by moving it to another day, but the goal is to maintain a regular shop presence.
So, I discovered that "something special" can also includes those days when I physically can't go. Today was one of those days.
Last night at Natalie's Scout meeting, I tried to prove that I could still play volleyball like a 20 year old. A "I-used-a-could-do-that" type of thing. Needless to say I slept poorly last night and felt like I'd been run over by a Russian cargo plane today, so I missed the shop.
After some rest and feeling sorry for myself, I decided I didn't need to go over to Ron's and could at least get something done here in my own shop.
I pulled out something simple to work on - the flaperon rear ribs. These are simple flanged parts, really just smaller versions of the elevator rear ribs I made before (see my previous blog post here).
It starts with lining the forms up on the metal template. Unlike other templates, due to their size they don't have bolt holes for the forms. Just line them up and place the entire sandwich in the vice:
The soft faced dead blow hammer is used to gently form the flange over the edge of the form:
Turns out the flanges are a bit wider than the thickness of the form. With the short top-to-bottom height of these ribs, I had to devise a way to protect them when I inverted the form to bend the opposite flange. To do this, I added two blocks on each side. One of them had a small groove cut in it to make room for the opposite flange but still enough area to hold the forms:
As per the plans I need 8 left hand and 8 right hand rear ribs and I made a conscious decision to do only six right hand ones first in case I mistakenly made a right hand one when making the left hand ones. Hate to end up with extras - that would mean making replacement templates for each one I screw up. It's easy to see how this could happen, glad I thought of it ahead of time. Good trick to remember for later when I start working on all the wing ribs!
It's amazing! With a bit of attention to detail, I managed to bang out 16 flaperon ribs, all of equal dimensions and quality. Really cool.
16 complete ribs.... not bad for a day I didn't feel up to doing anything :)
I also got a new 14 tooth-per-inch blade for my band saw. Installing the new blade was challenging, but I learned on YouTube how to properly set the tension and blade guides for my model. Once I make some of the rougher cuts on the plate aluminum using the big industrial saw at Ron's shop, I can use my fine tooth band saw to make the final cuts.
I've said it before.... a little shop therapy goes a long way :)
p.s. Photo credits to my daughter Natalie.... thanks for making me look good!
A while back I saw the following quote which really sums up building a big and sometimes overwhelming project like an airplane is....
How do you eat an elephant?
I have a lot of time on nightshifts at work to study my 750 plans and as I think of all the things I need to make, decisions on features I think I want to incorporate and how I'm going to make all these the parts, I get a bit discouraged. It is indeed a massive undertaking.
But as I keep being reminded both by others and myself, it's all the small bites that add up.
I find myself spending more time focused on completing tasks than taking pictures of my build which is both good and bad. I'm probably getting more done this way, but it doesn't leave a lot to add to my blog for you readers. Most of what I've done in the last couple of weeks is really just repetitive steps that I've already shared. But here is some of what's been happening.
In my last post I said I was headed back to the "drawing board". Here is the correct plywood I should have been using for my form blocks. Much smoother and knot free!
Each form template gets traced twice in opposite (flipped over), creating left and right side forms. These will be cut out in rought form using a hand jigsaw then cut close to final size using the scroll saw (more on this later).
Ron and I continues on our discussion regarding the wing extensions for the 701 wings I'm helping repair. Now that the main repairs at the root end are done, I can focus on this. Ron wants a 18 inch extension, so that's what I'll work towards.
First we have to remove the "factory" wing spar tip extension. I say "factory" because like a good majority of other "factory" items on this plane, it's really not to "factory" plans. Not the right thickness and missing two critical rivets at the upper and lower spar caps.... sigh. At least this time it's coming off to be replaced with longer ones, not just coming off to be fixed or replaced as original.
The wing spar tip extension isn't considered structural per se, but it is an important component of the wing. It supports the fiberglass wing tip and completes the outer structure end of the wing. Here it is close to it's original position on the end of the spar (I had already removed it at this point but forgot to take a picture):
....and removed from the spar. There appears to be a small wrinkle in the wing skin behind the joint, but that can be fixed easily and will be underneath the new skin extension:
Next we had to decide on how to handle the new wing skins extensions and how they would attach to the old skins. We believe at this point we can get away with a simple overlap with a double row of rivets, but we'll probably add a doubler strip underneath for strength, or even another wing rib. We trimmed the lower and upper wing skins to a convenient length and made sure to leave enough skin outside the last full wing rib. Where the trim line ended up (defined by green frog tape below) is actually a good place for a new rib:
The upper wing skins were trimmed back in the same fashion. Then, using the original plan dimensions I cut a new wing spar tip extension web (actually two, one for the other wing to match), by adding a full 18 inches to the inboard end. I was very important to get these right as they need to be perfectly straight to match the wing spar. After careful measuring, they turned out perfectly! This was also good practice making the long scoring cuts from a full 4 x 12 foo sheet of 0.025 aluminum. I'll be doing the same for my 750 wing spars and tips too:
With a little thinking and practice on a scrap piece of matching 0.025 aluminum, the top and bottom flanges were bent to a perfect 18mm width, leaving the total top to bottom dimension of 209mm, exactly as the plans call for!
We are going to wait on putting in the lightening holes until we see where the new ribs end up. The flapperons will also need to the extended, making another pick up point necessary which in turn will determine where one of the new ribs goes.
Ron keeps reminding me to continue working on my stuff too. So I took some time to make some of the smaller parts needed from some of the "scraps" left over from the 701 wig repair.
It's paying off studying the 750 plans when I can too. For example, I new I had to create 6 full length flapperon ribs and probably had enough cut-offs lying around from the repair I was doing to complete them. But then I recalled that the plans call for 4 full flapperon ribs made in 0.016 thickness and 2 full flapperon ribs in 0.025. I referred back to the plans and remembered that the two thicker ribs are "root ribs" meaning they are where the control rods for the flap actuators attach, requiring something more robust. The other 4 thinner ones are distributed elsewhere in the flapperon assembly. Glad I noticed nd didn't make them all the same!
They use the same templates, so I traced out the other four flapperon ribs on the 0.016 aluminum:
Although almost any thickness of aluminum can be roughly cut out on the bandsaw, a standard office paper cutter works great for cutting 0.016 aluminum sheet. Here I cut as close as I can to the template trace lines, then I use the grinder and hand sanding to bring them to final shape/size:
I'll store these in inventory as they are for now as I don't have the bending forms ready yet and wont be building the flapperons for a while.
To continue towards starting my tail section, I found another couple of little parts I could make up while I had the scrap out. I'm also learning that it sometimes pays to bend multiples of the same part where required. The tail section call for two of these 35 x 40mm bent angles from 0.025, and I had the perfect piece to make it from. After cutting and deburring, into the bender they went:
This way they end up being perfectly matched!
I got several other small parts made as well that aren't pictured here, but like the quote says.... "One bite at a time".
Wonder what's for dessert?
The Google search bots are really going to love my posts now!
Remember my fellow Corvair engine builder Jeff Moores of Newfoundland (see previous post "time-to-get-back-at-it")? While at the Zenair Open House we talked over lunch about the struggles I had been having with head studs and Jeff reassured me that my issues were common issues in both his previous builds. He offered to send me some extra head studs that he had lying around his shop to replace the bad ones from my core. They arrived via mail on Tuesday and they are brand new! All for the price of shipping via snail-mail.
The more I continue pursuing a Corvair as my choice of motor, the more I'm starting to realize the value of getting to know other Corvair builders, both for their experience and generosity. This is the kind of group I want to associate with, not some faceless foreign owned engine maker that just wants my money and couldn't care less about my mission to learn. Thanks Jeff!
Next steps, dealing with the 3 stud holes that need to be fixed (see "progress-sort-of") . I've decided on using TimeSerts which are a threaded barrel insert repair that is accepted in the conversion manual. Definitely more expensive than Helicoils (another possible repair method) but I believe worth the piece of mind. Corvair automotve parts warehouse Clark's Corvairs rents the TimeSert installation tool kit and also sells inserts that are the proper length and a blind nut tool for proper torquing of the head studs. I think I'll order those now and get the repairs done soon in preparation for some case machining work I'm planning.
Got a call from my buddy Guy (correct pronunciation is Gee, which is french Canadian) . Despite his best efforts to remove the broken studs he is struggling a bit. He tried welding a nut to them but they just snapped off further down and now they are sitting close to flush to the block. This leaves no option but to drill them out using a milling machine and end mill bit.
Fussy, temperamental work with a fairly high risk of wrecking the threads if not careful.
After finding limited success using the weld method, he tried centre drilling the stud in preparation to back them out with an EasyOut bit. This proved to be very difficult because the studs are a hard material to drill, but he did manage to centre drill one of the three. The other two he's going to use the milling machine as it should be easier.
The next concern will be how to clean out the remaining debris from the threads that gets left behind. The conversion manual is very specific that the lower end of the studs is a special thread called 3/8"-NC5. So at this point I believe I'll need a 3/8"-NC5 tap to clean out the threads. Even an experienced machinist like Guy had never heard of this particular thread (he checked with his suppliers too) and suggested it will be expensive to obtain due to it's rarity.
While my buddy worked on end milling the holes, I decided do do some research.online. Although I wasn't able to find a tap or die that matached this unique thread, I did come across an online archive of GM production drawings that show the machining dimensions of a Corvair engine! I really love the internet!
This is where it gets a bit more confusing. According to the dimensional drawing showing the machining instructions of the casting, the stud holes are supposed to be tapped to a dimension 3/8"-16 UNC:
But how can that be? The hole and stud should be the same thread as the stud..... hmmm.
I sent an e-mail to the internet Corvair conversion forum seeking some guidance.
Not long after sending the e-mail, I got a telephone call direct from William Wynne (the Conversion Manual author and recognized Corvair guru).
We had an almost hour long conversation about the conversion process, my overall plans and this particular issue regarding the studs among other things. He's very supportive of new builders like me that want to learn and his overall philosophy about home-building and being in the arena speaks to me.
He is an amazing person to speak with and very quickly confirmed that the GM drawings are correct, the stud holes are in fact 3/8-16 UNC. The reason the studs are slightly different is GM engineers wanted an interference (extremely tight) fit to ensure the studs would remain in place. Using a common 3/8-16 UNC tap would be appropriate to chase the debris from the holes.
Guy happens to have that tap (it's common) and I called him afterward to confirm what we know now to be correct. He's going to finish cleaning things up. In the meantime, I'll bring him the other half of the block and have him clean it up too. On the advice of William I'll also be contacting Dan Wesseman of FlywithSPA.com, William's recommended supplier for info on obtaining 12 new (to me) OEM matching long studs as the ones I have are too corroded to re-use.
To make things even better, Brenda tells me a fellow Corvair conversion builder called for me while I was at work and invited me to visit his shop near Barrie. He is building a Zenair 650 with a Corvair engine. It is almost complete at this point and offered to help answer any questions I might have along the way. I'll make contact with him tonight when I get home and maybe arrange a time to visit this weekend when I'm in the area for a family function.
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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.