What have I gotten myself into!: Nose and nose gear

Retraction system & NG-30s prep (8.3 hrs)

The original nose wheel retraction system consisted of a hand-crank mechanism that was light, and worked quite well. Notwithstanding these advantages, it created the need to turn a handle multiple times right after takeoff, and just before landing, something I have never been looking forward to.

Hand-crank to raise/lower the nose gear

One alternative I had set my sights on was one of the electrical retraction system manufactured by Jack Wilhelmson of EZ-Noselift, I chose the NL1-12E.

NL-12E system components plus NG15A and NG6A (aluminum pieces on left)

You can read all about it on Jack’s website, but I’d like to highlight the fact that it has a back-up battery pack able to power the gear down in case of a complete electrical failure, and the shock is contained within the actuator. Pretty cool!

This system is marketed as a retrofit for an existing short nose Long EZ with a manual retraction system, and the instructions reflect this fact, so they are not as useful as they could have been in my situation (new build), and I will have to modify the way I approach this installation.

So, with plans for a short nose I will not build spread out on one side, retrofit instruction for something that is not even here (and never will be) on the other, all the while keeping the long nose in mind, I started to untangle this mess.

Because of the “retrofit thing”, the installation will use the same bolt holes as on the original short nose with the manual retraction system, except for the lower one (let's call it A hole!).

On the short nose drawings, I first identified the 4 holes (the lower of which I will not use).

Original bolt hole locations

Then, I devised a coordinate system allowing me to locate the holes on the plans...

Locating the holes using a reference system

... and transfer them to NG-30.

Reproducing the hole pattern on NG-30

At this point, I tried putting all the pieces together as best as I could, to see how wide the whole thing would be, but I kept coming up with bigger dimensions that I expected. This was a problem, as the nose structure width must fit the center post of F-22.

Unsure if the problem was an actual one, or just the result of hastily holding numerous pieces up in the air while taking measurements, I decided to take the time to model all the nose structure components as precisely as I could, down to the thickness of the skin, in a CAD program.

Nose structure

Peeling the onion

This took a long time, but it eventually confirmed my suspicions... the nose structure came up 0.308” (8 mm) wider than the part it attaches to.

This looks like a problem

"It's always something, isn't it?"

"If it doesn't fit, you must acquit!"

While a little unsettling at first, I discussed my finding with other builders/fliers, one of which a mechanical engineer, and the general consensus is that making a flox corner between F-22 and NG-30 will restore, and actually exceed the original design strength of the joint.

Hand-drawn sketch of the proposed fix on my iPad

Although I was unable to draw it appropriately in the sketch above, foam will be removed from the core of the two parts, and the inner micro layer sanded off.

If I were to make F-22 again, I’d probably leave it 1/4” (13 mm) oversize at both ends of the center post, and plan on trimming it after NG30 installation.

In light of the recent fitting issues I uncovered on my nose, I decided to also model the actuator jack in CAD as faithfully as possible to ensure everything would fit all-right, and that there would be no more surprises.

Virtual actuator jack

Here’s the way the nose retraction system fits virtually...

Virtual fitting session

... and in reality.

Actual fitting session

Good thing I checked, because the virtual fitting session highlighted one more area of interference where the head of the actuator bumps into the top of NG-30.

"What now?!"

Interference volume highlighted in red

This was never an issue with the short nose NG-30s, since they were not as tall, but it is now, and my solution to this problem is to carve a small triangular niche in the foam 0.150” (3.8 mm) deep.

Modified NG-30 foam depth

Interference removal process

One other issue I identified through CAD, was that of the proper edge distance of the actuator bracket's holes when using my coordinate system.

Obviously something is slightly askew somewhere, perhaps my hole measurements wasn’t precise enough, or my hole pattern reproduction might have been somewhat inaccurate, or my modeling of the brackets... the point is, I made a mental note to not go by those C and D hole locations.

A week later, eager to get back to work, I forgot all about my previous assessment, and drilled those two holes per plans.

"Measure once, drill twice. Doh!"

It’s really a smaller issue that it might seem at first, but it still pissed me off, and of course I figured it out just as I drilled the last hole.

Since the brackets already had the bottom hole predrilled with the correct edge clearance, I used them as a template to locate the correct position for the C and D holes on the brackets themselves. I will eventually use the bracket holes as templates to drill the correct holes in the NG-30s.