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!
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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.