Spent some time in the shop on a rainy day.
Managed to make the rear elevator trim channel. It's critical to ensure this is made straight and to the correct dimensions as the covering skin leaves little room for error. A millimetre too big or too small translates to many problems, so I want to make sure I get this right, and it will be good practice for bigger parts later on in the build.
Unfortunately I've learned the plans sometimes leave out the "developed length" dimensions on some of the parts. In other words, what the dimension is prior to bending (which changes the length or width of a part as it bends). Not a huge deal if you are buying a kit as these parts come pre-formed for you, but for a scratch builder like me it's a critical piece of info. The math to figure out this isn't overly difficult, but making it repeatable using different material thicknesses and bend radii could be tricky.
Looking at the Zenair builders website, I found a great spreadsheet put together by another builder that does the math for you. It asks the basics (thickness, flange and web lengths and bend radius required). Input these or at least the ones known and the spreadsheet returns the "flat" or "developed length" dimensions. It's these that you use for cutting the raw aluminum. Here is a look at how a bend is calculated:
The spreadsheet makes it easy to apply the math, in this case for a piece of stock being bent into a channel:
So in the example above, entering 18mm for both flanges, with a channel web length of 80mm, requiring 90 degree bends with 1/8 inch (0.125) radius bends in the material 0.016 inches thick results in a developed length (dl) of 112.01mm. Just adding 18+18+80 mm together doesn't account for the bend radii or the thickness. The other result is handy too. Measuring 16.41mm in from the edge of the flat material provides you the sight line for the bending brake. I'm obviously only going to get as close as a half millimetre to these dimensions, but that's well within acceptable limits. Perfect, right?
One thing I learned early on in the process of making parts for the 701 wing repair is to use the never ending supply of scrap corners to try the theory before actually bending the full size parts (cheaper to experiment on scrap!)
So, I measured out the required dimensions on scrap, used the markings to align the piece in the bender and voila! Perfect example of what the full size piece should look like - this channel has two flanges, on at 90 degrees and one at 105 degrees.
Repeat the dimensions on the full size piece and bend the same way. Perfect and straight!
Finished off the relief angles on the rear wing ribs and root rib forms:
With this done, I made some headway on the 701 wing extension. Next step was figuring out the inside web doubler.
It's a bit of a puzzle as it needs to be fitted to span the spar caps top and bottom, the spar web and the closest wing rib. Consideration also has to be given to where the spar cap rivets will come through this doubler.
After careful measurement, I drew out the initial shape of the doubler. The dotted lines running left to right are the distance between each spar cap. The vertical dotted line represents the flange for attachment to the win rib:
To make the doubler fit correctly by sitting flat on the spar web and over the spar cap flanges requires a technique called "joggling". A joggle is a rise in the surface of the metal to overlap the adjacent panel or other piece. It's also used in reverse to create a depression in a surface to allow another piece sit flush, such as an inspection cover.
Joggles can be made in numerous ways, but I found a real neat tool that can be made out of scrap aluminum plate.
First, I measured out a rectangle of 0.125 aluminum plate:
Measure out the piece for a flex hole and bend slot:
Drill a hole on the press with a step drill bit. Makes a nice clean hole:
Cut the bend slot to approximately the same thickness as the plate, in this case 0.125:
Grind and sand everything smooth.
To use the tool, insert the piece to be joggled in the slot:
From here you have a couple of options. Thin gauge metal could be bent by hand by pressing down on the top of the "X" formed by the piece and tool.
Because this piece was made of 0.025, I decided to use the better option of pinching it all flat in the vise. This provides a much cleaner joggle and both sides of the bend lay flat. It's hard to capture this in a picture and I forgot to show it in the vise, but here is the result:
I purposely left both the flanges on either of the joggles wider than needed as the important dimension was the distance between the spar caps against the spar web. The flanges can be trimmed after test fitting it in place.
What a great tool. I made it big enough to do anything that needs joggling on my plane as well.
Next up, trail fitting the spar tip extension inner doubler and fabricating the rear rib channel. I want to get my 750 wing and root ribs final sized so that I can finish sand them prior to bending.
Until next time!
So Facebook reminded me this morning I hadn't posted to the blog in a little while but rest assured I've been busy at the shop.
First I had to tape together each of the four sections of wing rib templates and make sure the matched the plans. I used the form template as a rough guide and pinned both to the table for measuring:
After confirming the template is exactly as per the plans, I unrolled a sheet of 0.025" sheet and traced out 12 rear wing ribs and 2 root ribs. It's a bit of a challenge to arrange them to minimize waste:
It took about an hour, but I managed to get the big sheet cut down to manageable size then separated each of the ribs as rough cuts using the bandsaw:
Lots of final trimming and edge sanding in my future!
Work continues on my forming blocks. Now that I have them cut out and sanded to final size, the next step is to router a 1/8" roundoff edge on the inside (metal facing) edge. This prevents the aluminum from bending too sharply:
Next, I needed to figure out a way to bevel the outside edge of each form to create springback relief. Aluminum, particularly thinner gauges needs to be bent 6 to 10 degrees past 90 degrees in order to spring back to the intended angle. Turns out Ron still has the table adapater he made for his forms:
Here you can see a nose rib form sitting on the adjustment table just before I sand away the springback angles:
Here is a good picture showing the nose rib forming blocks, stacked as they would be in use. The routered edge and springback angles can clearly be seen:
Just to confirm everything matches up, I placed the aluminum nose rib blanks between the form blocks for a picture.... perfect fit and ready to start bending soon!
Encouraged by my success, I continued onwards with the rest of the form blocks for the tail group and they too are ready for bending aluminum blanks. Really pleased how these turned out:
Work also continues on the 701 wing repair. As part of the tip extension, two new full ribs will be inserted between the last factory rib and the wing tip. The necessitates cutting back the original rear rib channel:
Trimmed of the flanges of the existing rear channel leaving a long tab that will attach to the new wing rib we are inserting at this location. Once I have the wing rib in final position, this will be trimmed accordingly:
This new ribs will form the support for the wing skin extension joint and a second rib will provide the outermost structural pick up point for the extended flap and slat lengths. Here is the first extension rib test fit in place:
Next up, figure out where the second rib needs to be by determining where the outermost flap and slat pickups will be. Once I know that, I can make a new rear channel and also decide on the second part of the spar cap/web inner doubler. It will have to be attached to ribs too.... phew.
Progress... back to the shop again for the day tomorrow, hopefully to finish off the wing rib blanks and the wing rib form blocks. Thanks for visiting!
One of the things that I'm really enjoying about being in the shop working on airplanes is it gives me a great way to decompress from work as a 911 dispatch supervisor.
With new technology arriving every day at work, it becomes very difficult to champion change as a team leader in the communication centre. We're all feeling a bit overwhelmed and morale at work isn't the greatest right now. I think too that we all feel we were robbed of the summer as the leaves are already changing here in our part of northern Ontario. Winters tend to be fairly sedate (we don't use the "Q" word - that's how you summon death and mayhem in emergency services) and as a result nightshifts feel longer. It's no fun going to work in the morning when it's dark and coming home when it's dark.
Going to the shop for some plane therapy helps, so that's where I headed tonight.
I made working on the 701 wing extension a priority tonight as Ron wants to get that finished up so we can concentrate on both my 750 build and finishing off his Scout. Once they are complete I'll be able to get some stick time in both while we fly off the required post inspection hours. We're aiming for spring and that should be around the time I'll need use of the workbench for my wings and fuselage.
I've been working on the wing tip extensions. We decided to extend them by 18 inches and this requires extending the wing spar caps as well. These will be extended out to the tips, giving a much stiffer extension that what the plans call for.
Here I'm using the rivet pitch guide to centre punch mark the rivet hole locations.
After marking, and using the drill press to make the holes in each of the upper and lower cap angles, I backdrilled each of the spar cap extensions through the spar web extensionm adding clecos as I went to ensure the spar web cap remained in the correct place.
Take it all apart and debur all the holes on each piece (my new tool works great for that!). Then reassemble with clecos and test fit in position at the end of the wing spar. Perfect fit, tight and level!
Fit the front side spar web extension doubler and back drill through the web. Disassemble, debur, reasemble for final fit:
I've made the spar caps match the angle of the spar tips. Really like how they look and how they will secure the tip skins:
Great progress tonight...... not bad for 3 hours of therapy :)
Well, it was worth it heading south.
Took a side trip before a concert at the casino and met with my new friend Jim who was selling off some aircraft parts inventory.
Managed to pick up a bunch of stuff that I'll need for my build and at excellent prices.
From the top row, 2 bottles of EkoEtch and cleaner used for prepping aluminum for primer/paint.
Next row down from the top, 2 master brake cylinders for the rudder pedals on the pilot (left) side and a single master cylinder for the right side rudder pedals (I'll need a second one to match, this one I think was used as a hand brake).
On the white tissue paper and hard to see, 2 clear plexiglass window vents and associated hardware.
On the bottom row, 2 Matco axles and matching brake calipers. These were the model used on early 750 aircraft, but have since been superseded by a larger diameter version. Ron can use these on the 701 build which they are still the standard.
Very happy with my purchases!
Earlier this week was the 16th anniversary of the September 11th terrorist attacks in North America. I say North America vs. New York and Washington because even though these are the locations of the actual attacks, they had profound impacts all over North America including here in Canada.
I'm not going to go into a long story about where I was, or what I remember, but I think it's important to remember what happened that morning and how lucky we are to have the freedom to pursue what makes us happy, despite the efforts of others in the world who turn to terror in the furtherance of their beliefs. You can see more of my thoughts in a video I posted on my Facebook page.
Okay, time to move onto happy thoughts!
Spent a fair amount of time in the shop this week. Managed to get a bunch of parts cut out and ready for bending.
This week I also spent some time in the wood shop prepping my plywood forms for final sizing. The scroll saw is excellent for this fine work:
The important part is to make sure both sides of the forming block pairs match. So I started by cutting and sanding one side to perfect size, then used it as the guide for making the second the same size.
I didn't get all of them done in this session, but a got a good start. I focused on the ones I need for the horizontal stab and elevator, the current section I'm working on. I think I'm going to wait on the others and see if these work well and what improvements may be needed before cutting out the others.
That's it for today's update. There isn't really any easy way to capture all the work that goes into these but I hope this blog is somewhat east to follow along with. If you have any questions, please don't hesitate to ask by leaving a comment below.
Heading south today to go check out an inventory of parts that a gentleman has in a barn. It looks like I may be able to pick up some hardware for my build and possibly for Ron too. More details to come!
The last week of summer has come and gone. We made a family mini vacation to southern Ontario and took in the Brantford Community Charity Airshow among other things. It was an awesome airshow with quite the collection of warbirds, aerobatics and of course the Canadian Forces Snowbirds!
Also located at the same airport is Aircraft Spruce, one of the biggest suppliers of aircraft parts, pilot gear and building supplies. I had placed an order the week before and was able to pick up 3 rolls of aluminum sheet to be used in my build. Ron and Donna were also at the airshow and were kind enough to bring the rolls back north with them to the shop, saving us having to drag them around on the rest of our family trip.
I also stopped at KBC Tools in Missisauga and picked up a couple of really handy items. First, I've been reading about how to cut long straight edges on aluminum sheet. Some of the spars and doublers I have to make for my airplane are too long to be easily cut by shears. Even local machine shops in my area are either unable to handle the widths or too expensive.
One of the solutions on the Zenair builder's forums caught my eye. It involves making a aluminum cutting knife out of a carbide machine shop grooving insert attached to a handle, in this case a old crescent wrench.
I found the grooving insert at KBC tools. It's expensive for it's size, but is able to make very thin cuts in aluminum. For a couple of dollars more, I opted for the Titanium nitride coated insert making it more durable:
For a donor handle, I used an old crescent wrench with a seized head. I cut the head off at a 110 degree angle at the narrowest part of the handle using the chop saw:
Cleaned it up on the grinder.....
Next I used a combination of Dremmel tools and hand files to carve a shallow groove in the handle for the insert to rest in:
I made a test cut on a scrap piece of aluminum and this tool cuts it nice, clean and straight and only requires a couple of passes to score the aluminum enough for breaking. MUCH faster than using a laminate blade like an Olfa.
The other tool I picked up at KBC Tools was a NOGA Rotodrive countersink/deburring tool:
This is a much quicker and simple way to deburr dril holes. It is a rotating "dog-leg" countersink and with a very light touch and two turns will remove drilling burs without countersinking the hole. Lightweight and fast, it will be super handy as I progress through building. Much better than rolling an oversize drill bit between the fingers.
I continued work on the wing tip extension. I fabricated two (one for each wing) spar web doublers out of 0.032 sheet on the bandsaw. These will be the bread of the sandwich where the tip extension and spar web meet:
Laid out the proper rivet spacing and matched drilled them together:
Mounted the assembly to the wing spar web and match drilled the par caps, then clecoed everything together to confirm alignment:
With the assembly temporarily in place, the next problem needs to be solved. How to match drill to the original holes in the spar web (inclunding the orginal outer wing rib) without any access inside this part of the wing? As you know, the previous builder just eyeballed things so measuring what is already there won't be accurate enough. I could pull more of the wing skins off and back drill through the new doubler, but there is an easier way!
Introducing the "rivet hole duplicator". This ingenious tool allows you to match drill to holes behind the sheet aluminum. It consists of two straps of spring steel, one with a hole locator and the other with a drill guide:
With this tool, it's simple to find the right spot to drill each pilot hole. The pin tang slides in behind the panel you are drilling and the guide lines right up to where your new pilot hole should be..... GENIOUS!
Duplicate holes on web spar (right side of joint centreline) are complete awaiting final rivets. We'll need to figure out what we are doing on the back side to extend the spar caps and sandwich everything together but for now, this should be easily repeatable on the second wing:
With that complete, I took some time to fabricate the wing slat ribs from some spare 0.016 sheet.
There are 12 of them required, 6 in each wing slat. So I traced them out from the template, trying to use up as little real estate as possible. This will become more important later on when cutting other multiple items from full sheets:
One of the lessons learned earlier when I was making tail ribs was to centre punch and drill the relief and tooling holes before cutting out the metal, so I did that here first:
I discovered that the elevator tip rib form I traced out was undersized by about 2%. So I corrected the form and made the tip ribs with the correct aluminum template. Glad I caught this now, not later when I begin assembly. Here they are awaiting bending:
Very please at the progress I'm making. Coming up this week, I'm going to the woodshop to final trim and sand my plywood form blocks and I'll start tracing out the longer spar and doubler pieces for the horizontal stabilizer and elevators. Then I can start the assembly process!
As the summer draws to a close and the kids head back to school next week, I'm getting prepared to get moving in the shop on my build.
I'm hoping to finish up the 701 wing repair and make the updates necessary to the other wing. This will free up some bench space for tracing out my parts on the the aluminum sheet.
I got the wing spar tip extensions made and bent this week and added the stiffener angles:
All ready to be fit and installed, leaving just he skins and extra ribs.
I used some of the spare space on the bench to pin and tape my wing form templates together:
After tracing this out on the plywood, I got to work rough cutting out each of the form templates. These will become the final forming blocks once I final cut and sand them to proper size. I think I have most of them cut out with the exception of a few that I need to find from the 701 which may match (why make them if Ron already has them made?):
We are heading south in the next couple of days to catch the Brantford Community Airshow (see www.communitycharityairshow.com for details). Bonus news.... aircraft building supply store Aircraft Spruce is co-located at the same airport and I'm planning a little shopping :)
Next up, laying out some part templates on aluminum sheet and finish sizing the forming blocks.
LETS BEND SOME METAL!!
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?
Although I haven't been in the shop as much as I like the past couple of weeks, I continue to get there when I can. It's hard to be inside when the sun is shining so much outside (which means more stuff to do around the house), but the shop sure is nice and cool when it's too hot to be outside!
The wing root repair/rebuild is now complete, just need to clean up all the Sharpie marker notes:
Progress also continues on cutting some of the smaller template parts that I need for my 750 STOL build. These are wing parts (strut attachment brackets):
Yesterday, I finally completed the wing tank rear channel. Ron decided he wanted to return the fuel tank size to factory specs, so this necessitated moving the channel rearward and cutting down the original shorter to fit inside the tapering wing chord. This is the location where it should be according to the plans, the previous builder had half of this space for his wing tanks. Maybe that's why he purportedly ran out of fuel?
I don't have many pictures of the process, but here is the completed item riveted in place:
With this done, we'll be moving on to the wing tip extension that Ron wants done. While we plan that out, I started tracing out the templates in preparation of cutting out the plywood forming blocks required for my 750. It starts with a piece of plywood which Ron purchased for me as part of another project he is working on. We had discussed the need for only half a 4 x 8 sheet as some of the forms that I need Ron has already made and interchangeable with the 701. So I grabbed a half sheet from the woodshop:
Each form template gets traced out twice to make out each half of the forming blocks:
As you may recall from previous posts, it took a fair amount of time working in CAD and with Adobe Acrobat to print full size templates onto card stock. Some part templates are fairly large and don't fit on a single piece of 11 x 17 inch cardstock, making it necessary to break the template into 2 or more pieces. For the most part, it's long pieces like wing ribs that are the issue, like this wing root rib form template which is shown here taped together:
It's also helpful to pin larger templates down to ensure an accurate trace:
Just as I was pondering whether all my templates would fit on this piece of plywood and how to make that happen while trying to avoid placing cut lines on places with wood knots, Ron arrived back in the shop. He quietly asked how I was making out and I explained my dilemmas. Ron quietly grinned and told me the piece of wood I was using was actually scrap flooring from the other non-airplane project he was working on. My piece was still up in the woodworking shed.
Guess it's a good thing I didn't trace everything out yet and I haven't thrown out the templates, otherwise it would be back to the drawing board. Hehe... drawing "board"... I kill me.
Back in a few days.... :)
I apologize to my regular followers that I haven't posted much lately. End of June and beginning of July are a very busy time for our family, between the kids finishing the school year, birthdays, anniversaries, fireworks shows.... there hasn't been much time for shop.
I did manage to make some progress yesterday when I freed up a full day in the shop.
The work continues on the 701 wing repair. I finally got the final riveting complete on the rear channels, root rib and tip and fuel bay area. All squared up ready for a modified (again) fuel tank support channel:
Getting everything lined up and square is a real pain when working within the bounds of what the previous builder left behind, but it eventually went together okay. Lots of tight places to try and fit the pneumatic riveter!
The tip rib is fastened to the spar and through to the root rib by two A5 rivets. According to the plans, the top most hole also uses the same A5 rivet, but the plans don't seem to account for the extra thickness created by the wing attach point. I'll have to have another look at the plans and check with Ron. I'm almost of the mindset to buck a solid rivet in there - always go better than the plans in any modification made.
With this section repair almost complete, we'll be moving on to the wing tip extension Ron has planned for this 701.
In addition to the 701 repairs and modifications, I've been slowly making parts for my 750 in anticipation of starting my tail group in a couple of weeks. Lots of tracing, rough cutting, trimming and final debur/sanding.
Seat belt attachment brackets and flapperon splice plates complete and ready for inventory. These aren't tail group parts, but it often makes sense to complete items as they fit on the sheet of raw aluminum of the same thickness. You are already tracing and cutting anyhow, why not get stuff done at the same time.
There won't be any shop time for the next couple of weeks as we head east on a camping trip. I've made contact with a guy in Quebec who is selling a bunch of aluminum sheet and angle extrusions. I hope to stop at his place on the way home and pick up a bunch of materials at a discount rate.
Thanks for reading, back in the shop soon!
Time until takeoff
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.