Sunday was a good day in the shop, and both Ron and I can see the finish line with the 701 wing repair and extension. Just a few more small items to go.
As Ron gets close to covering his Aeronca Scout with fabric, we've been discussing his plans to make a fabric/pain rotisserie rig for the shop. You may recall from way back in this blog an engine stand I bought for my Corvair. With my engine parts in Florida for rework, we're going to modify my engine stand and Ron's engine stand to become the end pieces for the rotisserie. This rig will allow us to mount any fuselage, wing or other large parts for priming and painting and being able to rotate them will be very helpful.
The inboard nose skin is ready to be installed. I clamped the skin in place, lined up along the spar. To draw the nose skin tight, ratchet straps are used, pulling the skin tight across the ribs. It's important to place the straps directly over the nose ribs to prevent caving in the nose skin before it is riveted.
Straps are equally tightened until the nose skins lay tight against the nose ribs and spar:
Folded protectors distribute the force across the trailing edge, thin scraps of wood protect the surface skins from the ratchet and strap hooks.
Using the hole duplicator, I matched the new nose skin to the original spar holes on the upper side of the wing. These were drilled to final size, the nose ribs to A3 until final fitting. The 3rd rib is drilled, but missing clecos so I can fit the outboard nose skin where it will overlap the slat pickup.
Once measured up, the outoard skin needs to be slotted to allow the slat pickups to protrude through. The easiest way to do this is with a trim router and spiral up-flute milling bit. I laid the outboard skin out on the table and set clamped a straight edge in place as a guide. Two strips of plywood under the sheet on either side of where the slot will be cut support the thin aluminum sheet and are thick enough to raise the bit above the table
After cutting all 3 slots perfectly straight, a valuable lesson learned - even if you right down the measurement, that is no guarantee that what you wrote down is correct :(
I measured the first slot as 395mm from the inboard edge, but for some reason I wrote down 595mm. From that point on, every time I double checked before cutting the slot, I measured/checked it as 595mm. Bringing the sheet back to the wing, my error was immediately obvious.
After pacing around the shop wondering how I could have possibly messing up the measurement, Ron told me he could fix the error fairly easily with a simple patch - go ahead and cut the right slot. This is part of learning and too much sheet metal to start over.
With the correct slot cut, all the slots lined up perfectly with the slat pickups - minor crisis averted.
Before working on securing the top side of the outboard nose skin, we thought it best to finish securing the inboard nose skin, that would give us a solid reference point for the outboard skin. We flipped the wing over and end for end on the bench. To get the nose skin flat, a thin strip of wood is placed under the ratchet straps. Once lined up and tight against the ribs, I again duplicated the spar holes and drilled the ribs to A3 size. Everything lined up excellent.
Even this nose skin, as small as it is lengthwise makes the overall wing so much more rigid. A good sign.
While waiting to discuss my slotting error I also unrolled my 040 sheet and start marking out the 3 horizontal tail doublers I need. I was initially really surprised at the amount of tape Aircraft Spruce used to secure the roll, but quickly understood why! There is a bunch of pent up spring energy in that roll, and I had to be real careful about wrangling it onto the flat floor for measure/cutting. The longest piece I need from this sheet is 1440mm long, so it was safe to cut that length off the end of the 12 foot long sheet. I marked and rolled the balance back up (that was a task!) and put it back into storage.
Aircraft Spruce ships all their sheet aluminum with a protective plastic sheet coating on both sides. Depending on how long the sheet has been on the shelf, room temperature, and other factors determines how easy it is to remove this coating. I think next time I'll gently warm it with a heat gun or hair dryer - this stuff sticks too good. For now, I've only removed a few inches from the edge I'm cutting from.
Even cut down to length, this sheet is awkward to put in the bender for scoring, and it's thick enough to making scoring a very long process. Instead, Ron and I think we are going to try using the router we used on the nose skin slots to accomplish the long cuts. If this works as we think it will, we'll use the same process for the wing spars (032) and maybe the fuselage sides/tops - anywhere a long straight cut on a large piece of material is needed. As I said above the tool makes really clean cut edges that require little in the way of deburring.
One other thing I've been doing is adding some of the complex shapes from the plans into CAD. Like my smaller parts (ribs, plates, etc.), these will be printed out to provide templates. One example is the wing root nose skin. I use a free downloadable 2-D CAD program called LibreCAD - it is very simple and more importantly it will accept the X/Y co-ordinate system common in the Zenith plans:
If you like doing things in 2-D CAD, you can download a free copy of LibreCAD here.
For those that have been asking, my finger is healing up nicely :)
More soon, thanks for reading.
After a week of resting up my arm, I took the day to go to the shop to see what I could get done.
First up, I decided to tackle the patch we need to make for where the original upper wing skin got torn at the root. This was either in the crash (likely), recovery of the wreckage (more likely) or propagated from the non-existent edge deburring by the original builder (probably most likely, but no way to prove it).
I had previously stop drilled the end of the tear and trimmed back towards the root edge. Using a lid from a coffee can, I traced the approximate shape we want the patch to cover:
I cut the patch to match the blue outline. The line is an appoximation of the open space we are trying to cover:
Final holes to A4 size, deburr and rivet. I used an edging tool to roll down the trailing edge. This tightens the patch against the skin:
The final photo of the patch - nice and tight:
Next up was finding another length of 016 for the outboard nose skin. While rolling up the remainder, the coil slipped a bit, catching my finger with the fresh sharp edge.... ouch! Feel kind of stupid and should have known better to wear gloves. Fairly deep cut, but took more skin layers than anything and I was able to tape it up and stop the bleeding without to much effort. Just in a bad spot on my good hand. Learning as I go right? LOL
I didn't take many more pictures today, just wanted to keep working. Did manage to get the outboard wing nose skin cut to rough size and deburred. Next up I'll have to cut the remaining slot bracket holes and get both of these nose skins mounted.
One thing I did take a picture of though.... one of my rolled sheets of 040 that I bought last summer. I'm getting it ready to roll it out and cut some more parts for my 750 tail. This time I'll wear gloves :)
Thanks for reading, more soon :)
Finally got back to the shop yesterday and got some work done on the 701 wing repair. Looking out our window lately makes travel to the shop..... fun. Makes me look forward to having some flying fun on skis!
Before starting up again on the 701, I decided to have another look at the 750 cabin frame I picked up last weekend.
The edition 2 cabin frame was changed/updated to edition 3 by Zenith in an effort to increase head room and apparently allow for a design gross weight increase. From a Wikipedia defintiion, aircraft gross weight is the total aircraft weight at any moment during the flight or ground operation. An aircraft's gross weight will decrease during a flight due to fuel and oil consumption. An aircraft's gross weight may also vary during a flight due to payload dropping or in-flight refueling (neither of which applies to my 750 - imagine in-flight refueling... oh the places I could go LOL).
The changes included removing the diagonal tube that crosses the top of the cabin and replacing it with two shorter corner tubes at the front corners of the roof - these new corners serve the dual purpose of becoming hand holds for climbing in and out of the cockpit. Both the old diagonal tube and the corner tubes are made of the same diameter and wall thickness tubing, so when I make this modification, I won't have to buy new tubing, I'll just use the removed diagonal.
The other change I've read about is that a larger spar carry through tube is required for the gross weight increase. This is the major component of the cabin frame and where the wings attach to. It's the main structural component that gives strength to the wing-fuselage interface - very important obviously as I plan on using this plane off strip, also putting the 750 on floats eventually and definitely want that extra strength and rigidity. Some others that have done this upgrade to edition 3 cabin frame have noted their spar carry-through tube needed to be changed to a larger tube. That's a lot of welding.
The cabin frame I have must be a late model edition 2. I measured the spar carry through tube and it matches my edition 3 plans in both diameter and wall thickness! This saves me a ton of work and materials. Once the corner braces are done, this cabin frame is good to go. Good news!
Measured up the inboard nose skin for the 701 wing. We have to use an inboard and outboard nose skin due to the extended wing. I tried using the original damaged wing skin as a template, but like most things the original builder did, it's measured wrong. I decided to cleco the old skin in place to see how far they were off the plans (my repairs to the nose ribs and spar caps are correct to the plans now). Yup, they were no where close and certainly didn't debur anything.
Once the skin is cut to rough size, I had to start to do the figuring out stuff regarding the slat attach brackets. The goal is to make the slot just the right length and position for the bracket to project through. Think twice, cut once is what they say, but in this case it becomes think many times, cut many small times and think again until it's just right. Repetition plays well here.
I placed the original wing root skin in place - look how far they were out from spec. If it had been right, they wouldn't have drilled the skin rivets in the wrong spot on the ribs - they should be on the flat spots between the relief bends. The root skin is too badly mangled to salvage, a new and proper one will be made.
The upper skin now completely done and riveted. The last few will be done when the new root skin is made. We'll likely wait on this until this wing is mounted on the fuselage to ensure proper fit.
Was going to go back to the shop again today, but I've somehow managed to strain my right arm to the point I can't left a drill or grip a set of cleco pliers.. I suspect I overdid it when shoveling off our house roof the day before. Some say it's part of getting old. So today is a day of rest and recuperation.
More to come, thanks for reading!
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.