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?
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.