Landing brake - part 2

Time for a brake! (9.0 hrs)

There is something cool about needing a landing brake. It subliminally screams FAST, and it's also going to be the first component of the plane to actually move as it's supposed to. Needless to say, I've been looking forward to this part.

With the landing brake recess cut and glassed, it was time to start manufacturing the actual brake.

I had a few pieces of 3/4” (19 mm) foam in my scrap pile, so I microed them all together to form a landing brake blank.  

Using West System micro to glue the foam pieces to each other

Landing brake blank curing at 72℉

Curing was taking too long, so I fashioned an "EZ bake oven" out of an Aircraft Spruce box.

At 140℉, it cured solid in no time!

Since I cut the slopes of the depression at 45˚, I setup my table-saw at the same angle, and quickly roughed up a matching outline.

This is so much easier than sanding!

Looks menacing already!

The panel fit into its recess a bit loosely, and was in serious need of some top sanding.

This is going to need a lot of sanding!

Following the instructions, I mixed up some 5 min epoxy, and placed small beads into the depression every 3” (7.6 cm) or so, then laid the foam panel back in it.

With the panel firmly attached to the underlaying fiberglass, the sanding started, and went on, and on, and on... you get the idea!

The original 80's landing brake was made out of urethane foam which was very easily sanded, but there were later issues with its strength, so the move was made by RAF to the much stronger, but harder to sand blue foam.

Polishing my cabinet making skills!

The two shims prevented the forward lip from dipping into the deeper part of the recess, under pressure.

Eventually the tough foam was sanded into submission, and a pretty nice brake started to emerge.

Gray tape was added once the final shape was achieved

This is where I deviated slightly from the plans, and took a different but proven detour.

Borrowing from Beasley’s experience, I used modeling clay to fill in the gap that had been created, so that the outer BID layup would bridge across it without any dips.

The clay will be removed before glassing the inside part of the brake.

I wish I could take credit for this smart idea, but it was Beasley's.

I think I've done this once before... in kindergarden!

Looks like a square blueberry pie, crust and all!

No need to be too precise here, somewhat flat will do.

Gap bridged, we are ready for glassing.

Last thing left to do was prepping the work area for 3 simple flat plies of BID.

When the epoxy started flying, I ended up needing all this protection.

I chose to reuse a small piece of BID, but I would do it differently now, and go with a full BID piece, since the scrap left a minute bump on the finished surface that could have been avoided. This will be fixed with the final outer coating, but I will try not to do this again on the exterior surfaces.

Reusing scrap bid. Bad idea on outside surfaces!

All three plies curing

You can't see it, but there's a tiny ridge where the scrap overlaps the rest of the first ply.

Landing brake - part 1

Creating the depression (20.0 hrs)

The landing brake will be housed in a depression carved into the bottom of the fuselage.

Like plastic surgery, it all starts with a sharp cutting implement, and a lot of hope for the end result. 

"Nip and Tuck"

Fiberglass did not stick to the strategically positioned packing tape below it

As much as I tried holding the cutter at the 45˚ by hand, I kept steepening the angle for some reason, so I decided to rig something up to help myself.

Cutting a slot at 45˚

This worked very well indeed, and the plywood panel fit nice and snug into the slot at the required angle.

The hinge will attach to the plywood, after it gets trimmed down

Because I still needed to cut the actuator slot into the fuselage floor, I tried the “carpenter square” method again, with equally good results.

Vertical milling

And voilà,  a landing brake actuator hole!

The plans call for carving a 0.5” to 0.6” depression into the foam. As I did in the past, I used the router to clear up the foam in a consistent matter.

A "depressing" job

Clearing the foam

Edges sloped at 45˚

Up until this point everything went pretty fast, but it only took one dumb decision to deviate from the plans sequence of events, to put the stop to that!

I thought that it would be simpler to drill and tap the aluminum blocks before attaching them to the fuselage. While I was right about that, I didn’t anticipate the amount of work, and headaches this would create for me later.

Aluminum blocks erroneously tapped before installation (don't you do that!)

Aluminum blocks epoxied to the plywood (swimming against the current now!)

Needless to say, I should have followed the plans. What was I thinking?

To prevent micro-slurry from getting into the threaded holes I tapped into the blocks, and that should not have been there in the first place, I had to make something to plug them temporarily. So, I shortened some bolts I had, and cut slot into them to allow me to remove them later with a screwdriver.

Trying to dig myself out of the hole

This ought to keep the evil micro at bay

After carving more foam to clear the actuator brackets, I microed the plywood into the slot I had carved, and went to bed.

Plywood, aluminum blocks, and headless bolts microed in place

Done for the day

The next morning, I prepped the fuselage for glassing by taping around the depression, and putting dry micro into every sharp corner.

Ready for surgery

Smoothing all corners with dry-micro

The plans require 2 full plies of BID, plus a third smaller ply over the hinge section only. I elected to lay the smaller ply first, so that I would have a smoother transition without having to use extra peel-ply across the layup.

Reinforcement layup

2 full size layups

All 3 plies in place

Lastly, I trimmed the fiberglass all around the perimeter, and peel-plied over it.

Edges trimmed, and peel-plied

A better angle

"Tooling up" - Mill's new back brace

Strengthening the mill column

It took 2 whole days for the conversion, one of which was spent just "tramming" (realigning to vertical) the column!

This type of mill has the ability to tilt the column ± 45 ˚ to make angled cuts. Generally, however, it is preferable to angle the workpiece in the vise instead of the column, since realigning the vertical column can be a lengthy procedure.

Given that one single bolt connects the mill’s column to its base, and the considerable suspended weight of the head (about 40 lbs or 20 kg), it is possible that vibrations occurring during big cuts, might swing the cutting implement (forward / backward) and reduce accuracy.

Using a precision indicator positioned over very accurate “123 blocks”, I measured these deviations by applying moderate pressure on the head of the mill (forward / backward).

The deviation recorded by the indicator was ± 0.001 inches (0.0254 mm). After completing the project of strengthening the tower of the mill, this deviation is reduced to ± 0.0005 in. (0.0127 mm).

Although it doesn't sound like much, this actually translates into a 50% improvement.

For comparison purposes, the average width of a human hair is 0.004”, and we are talking about a movement that is 8 times smaller than that! So, we are literally "splitting hairs".

Unfortunately, the process of realigning the column has become much more involved, since now each bolt wants to impart its own small torque to the column during tightening.

All in all, I think that the gain in precision obtained by this modification justifies, even if only slightly, the increased complexity of the realignment process. Procedure which fortunately will be much less necessary thanks to the update.

This conversion has the added advantage of making the X2 mill a better CNC platform, should I choose to move in that direction.

Looking at the back side of the mill

Adding the back brace

Bracing completed

"Tramming" setup

Left side view of the modified mill

Removing hard to grab peel-ply

Glassing the outer fuselage presented a good opportunity to demonstrate how to remove hard to grab peel-ply.

I'm sure there are hundreds of ways for doing it, but this is what works for me.

How to remove stubborn peel-ply

Ch. 7 - Fuselage exterior - Part 7

Glassing the outer fuselage (23.0 hrs)

While I wouldn’t recommend glassing the fuselage by oneself, that’s exactly what I ended up doing for a number of reasons. 

The main difficulty consists in the amount of time required to complete the job. Sure, the manual says that it should take two guys 4 hours to complete the job, but I’m starting to get the sense that the numbers in the manual might be a bit optimistic.

I ended up spreading this job over the course of two days, mostly to make it easier on my back. I completed the right side of the fuselage on day one, and the left side the next day, peel-plying the seam in between.

The level of technical difficulty is not great, but the sheer size of the fuselage was enough to make me wonder if I’d ever get to the end of it.

One item that proved invaluable during my solo glassing extravaganza, turned out to be the mobile fiberglass dispenser, much more so than I would have anticipated. It basically behaved like a human helper by holding the fiberglass for me, without any complaints, and best of all, without drinking all my beer.

The only part that was a little tricky was the seam down the middle, where the overlap would occur. To avoid creating a bump in the middle, CP#28 highlights a different layup schedule from the plans.

Modified layup schedule from CP#28

If you notice, items 1 and 3 specify the UNI to be laid at 45˚. The correct bias is 30˚, and that was a mistake later corrected in CP#29.

So, here’s how the work progressed...

Draping the 1st ply of UNI in the front section  at 30˚

1st ply rear layer

Posing with the 1st ply rear section

1st, 2nd and 3rd (front only) plies completed

Peel-ply added to the side

Peel-ply added to the bottom

The next day started with a backache from standing on a concrete floor for 12 hours straight. Later, I removed the peel-ply, and repeated the same process on the left side. As I mentioned, not the most mind challenging of layups, but it still took me 10 hours to get done.

Day 2: removing peel-ply from centerline

1st ply front section getting laid (lucky for him!)

I begun by wetting the cloth to lock in the bias angle, before cutting the fiberglass

1st ply rear section

More peel ply on the bottom...

... and on the side

Proud parent

There were quite a lot of sharp edges to cut off the next day...

Removing excess glass in the form of sharp edges

... but I was finally rewarded with a completed fuselage that I can finally sit and make airplane noises in.

Ready for "show and tell"

The girl with the "XX" tattoo

Most peel-ply removed already

"Man, that's a wide cockpit!  I like it!"

Plenty of room in the rear to keep the GIB cheery