Ch 19 - Wings and ailerons - Part 2

Wing attachment points (45.0 hrs)

"How many bolts does it take to mount a Long EZ wing to the fuselage?"

"Three."

Yep, you read it right, only three bolts are needed to keep each wing attached to the center-section spar, and the wing bolts attachment points (aka metal plates) are all installed in the first foam block (FC1).

Eureka CNC plans broken down by major foam blocks

Two of these bolts are accessed through two small dedicated depressions cut into the top and bottom of the wing, and one from the wing root pocket.

Using JT to illustrate the location of the wing's top bolt...

... and the wing's bottom and inner bolts

The plans will have you do the work of creating these pockets with the foam blocks already in the jig, but it is much easier to do it before glueing FC1 to the rest of the wing.

Let’s work on the root pocket first, then we’ll do the other two.

This process involves slicing off a part of FC1, hollowing it out, then glueing it back to FC1, then installing the first one of many metal plates.

Marking the cut line on the wing root foam block

Using two nails on the black line as guides for the ruler

Clamped one ruler on the wing foam top, and another one on the wing foam bottom.

Using the rulers as guides for the saw

This will become the wing root pocket

Using the rulers as guides again

Cutting off the critical 0.6" (15 mm) dimension

Front face to be reattached later, 0.6" non-critical perimeter marked in black.

Creating the wing root cavity

The inner piece of foam will be reused to stabilize the now delicate foam perimeter

Front face reattached to the perimeter foam, curing around the inner core 

Wing root section with micro, in preparation for getting reattached to FC1 foam block.

Wing root section curing after being reattached to FC1

Talking about metal plates, I had already made most of them years ago when I was working on the center-section spar, but a few of them weren’t mentioned in the spar chapter, so I had to make some new ones.

Two LWA4 ¼" (6.35 mm) 2024 Al plates, and two WI8 0.016" (0.4 mm) 2024Al sheet 

Etched then Alodined the metal parts

My Alodine is a bit weak, so I used aviation style etching primer on the plates

We will use these a little bit later. First we have to create the depressions for the outer two wing bolts, one on top of the wing, the other on the bottom, then glass them.

I often colorize the plans' photos in the blog to make them a little easier to understand

Unfortunately the depth of the two depressions are not only different, but also decreasing the further back one goes due to the slant of the wing profile. 

Measuring the deepest part of the slot (gray= metal, blue = foam)

Bottom slot is 0.030" (0.76 mm) shallower

The floor of the depression however is perpendicular to the front face of the foam block, so with a little ingenuity (thanks Ary) it is possible to cut the foam as in the plans.

Drawing dimensions on foam is difficult. I learned this trick from Walter Grantz (R.I.P. my dear friend).

It's just regular painter's tape, nothing fancy, but the pen marks are much more readable.

Bottom slot dimensions marked

Establishing a reference plane (plexiglass) perpendicular to the front face of the foam 

Using the reference plane as an aid to cut the slot to the charted depth

This was Ary's idea, and worked quite well.

The obligatory photograph for a future DAR (Designated Airworthiness Representative)

Slow progress precision foam removal

Here's a perfect variable depth slot perpendicular to the foam face

Shimming the square to establish the reference plane on the opposite side

Bottom slot cut using the same technique

Wow, that was a little bit weird, but worked quite well. Time to glass the pockets.

I think I use as much duct tape as I do fiberglass building this plane

Two plies of BID cut at 45º bias

Foam slurried, and micro fillet applied to the edges.

BID prepregged

BID applied and peel-plied

Always use a bigger piece of glass than needed, then trim later.

What a difference a day makes!

Slot trimmed and lightly sanded to remove all peel-ply strands

Most of you probably already know what’s going on here, but for those new to fiberglassing let’s look at this process again in detail on the bottom side of the wing.

FC1 flipped over to repeat the process on the bottom slot

One can never have too much duct tape

Painting on the micro-slurry

Wetting the BID cloth with pure epoxy in between plastic sheets

The result is what we call pre-preg

Pre-preg means previously impregnated, referring to a ready-to-use epoxy soaked fiberglass sheet.

Pre-preg is easier and less messy to work with. Just peel the backing plastic, and stick where needed.

Then one works it down to the foam with an epoxy soaked brush

Peel-ply added over the fiberglass (not required in this instance)

The glass should have lapped slightly over the metal plates, but I chose to install them later.

Peel-ply removal time

Cleanup is alway a bit tedious

Bottom slot ready for business

I like the way those pockets came out. Now we just need to recess them, and the foam, so that we can fit the metal plates through which the wing bolts will connect to the main spar.

The two metal plates I should have mounted before glassing the slots

Setting the Dremel tool to a depth equal to the thickness of the LWA4

Ready to remove material

Foam and glass removed to accommodate the LWA4 plate

Test fitting the bottom LWA4

LWA4s need to be flush with the foam as they will be glassed over by the shear-web

The plate didn’t line up exactly the way I would have liked, so I used toothpicks to hold it in place for the next step.

Creating a flox corner by removing foam, and sanding the micro-slurry off the back of the glass.

Using toothpicks to make up for my previous lack of control with the Dremel tool

The toothpick trick worked amazingly well in lining up LWA4 precisely

Flox in the corner (hence the flox-corner name)

LWA4 and WI8 floxed to the slot

In case you were wondering, I did not remove the toothpicks. There was really no need to do so, as the toothpick are stronger than the foam they displace anyway.

You might notice I used flox instead of micro here. I did this for two reasons. First, I wanted to create a flox corner between the fiberglass of the slot, and the fiberglass of the shear-web that will go over it (and the metal plates). Second, since I didn't lap the fiberglass slightly up the metal plate in the pocket (as seen in section B-B on page 19-12), a little extra strength there made me feel better. Probably not necessary, but definitely didn’t hurt anything.

The toothpick trick worked well by the way, and the plates lined up with the foam surface correctly.

The next day I double-checked for alignment with the foam

The toothpicks certainly worked their magic

Getting three surfaces to align at the same time can be a challenge

This might be a good point to bring up a Builder Hint from CP38…

JT doesn't have this, and I haven't had any issues to date, but #2 will get this soon.

I’ll put that off until later. For now let’s concentrate on the top pocket using the same toothpick trick to line the metal plates up with the foam.

More targeted toothpick action

Flox will close the slight gap

Taped the two plates together

Test fitting the plates together

Duct tape means we are ready for business

Floxing the corner

Adding the metal plates

Using some small tools to add weight to WI8 while curing

Last but not least is the inboard wing mount.

Test fitting LWA6

Duct tape to the rescue!

One last check after priming

I used micro here since it will mostly be removed while glassing the wing root pocket at a later date.

Micro used here

LWA6 curing

Next day. LWA6 is there to stay.

Nothing left to do but bond FC1 to the rest of the aft wing already in the jig.

Just as with the rest of the foam blocks, slurry and wet micro will glue them together.

FC1 reunited with the rest of the aft wing in the jig

The ever present duct tape

I used nails as usual to hold things steady while curing

One day later we are back in business, ready to begin work on the shear-web.

Stay tuned, because next time we will begin the process of building the internal structural parts of the right wing.

Ch 19 - Wings and ailerons - Part 1

 Foam and jigs (22.8 hrs)

Perhaps it shouldn’t be, but this chapter has always been a little intimidating for me, not only are the wings the biggest single item of this project, but they also need to work… or else. You know what I mean?!

Slightly foreboding, isn't it?

An issue that never previously crossed my mind has been the difficulty of maneuvering something so big and fragile around the shop. One soon runs out of space when working with so many wing pieces, and it always seems that anytime the foam is handled, more and more dents get added to the tally. So, reducing the number of interactions with the foam to those strictly necessary to the building process quickly became an imperative.

First things first though, time to get all the pieces of foam out of the many boxes they came in from Eureka CNC years ago, and put them together on the big table.

RW (Right Wing) foam pieces emerging from long term storage

OMG! This thing is humongous! 

"What was that saying about how to eat an elephant?"

"Oh yeah... one piece at a time... gulp!"

The Long EZ plans only deal with five big pieces of foam, FC1 through FC5, but Eureka CNC cut the foam in thirteen pieces to make them easier and cheaper to ship, so it’s up to the builder to reduce these back to the five parts the plans describe.

Eureka CNC foam breakdown (plans' FC sections highlighted)

And reducing I did… for three days.

As usual, tape and slurry the joints.

Tried non-reusable toothpicks instead of nails this time

Honda Element rear disk brakes are very helpful during this process

Obligatory shot for future FAA observers, in case there is any doubt about who built this plane.

It's amazing how fast big surfaces gobble cups of micro-slurry

"Braking action report... Good!"

Rounded pieces are a bit trickier to weigh down

Using the same foam they were cut from helps immensely

The weighing down process becomes even more complicated

Using every trickery at my disposal to get the job done

Creativity and resourcefulness are very much part of the job description when building a Long EZ

Micro-slurry to close the foam pores, and wet-micro as a bonding agent.

Had to use an extendable broom stick to reach both sides

Foam puzzle to weigh down the leading edge on one end...

... and a rear wedge piece on the other end, at the same time.

Admittedly I don't like to rush, and eventually I ended up with the five big foam pieces.

Wing pieces FC1 through FC5 ready for action

With all the foam blocks accounted for, and the help of my trusty laser, I set out to build the straightest wing jig I was capable of, little did I know it wouldn’t turn out to be that easy. Even though my twelve foot table is super flat, leveled in every which direction, and I would be using Eureka CNC cutouts, issues would crop up.

My first step was establishing a straight line 125.6” (3.2m) long that would represent the forward edge of the wing cutouts. Now, I don’t have a straight edge that long, and the sides of the plywood top that make the table were never square to begin with, so I turned on the laser and traced the red beam on the table.

Tracing the red laser line on the table

Dimensions are very specific on the plans

The plans specify the locations along this line for the wing cutouts, which are also marked with a common waterline allowing them to be lined up vertically.

A flat and level table is a God sent in a situation like this

All waterlines lined up on their own, thanks to the work we did on the table

Still no shimming required at this point

Four out of four here... scored!

This is what I look at when I align the cutouts vertically

Last cutout ended up needing a little help... Oh well!

I didn’t have to shim any of them until I got to the very last one.

Used hotel key cards to shim the cutout up. I reckon 4 out of 5 is still pretty good. 

At this point I tried inserting the foam pieces into the cutouts, only to find out that that didn’t work, further damaging the foam. I ended up needing to disassemble all the cutouts in order to insert the foam, but I had already Bondo’ed the aft pieces in place, so I had to chisel that off. Note to self: don't repeat this mistake on the other wing.

Did not like having to do this

Had to chisel off all the back pieces

With that, the wing went in.

Finally an operational jig

Crap! This thing looks even bigger now.

After a few minutes of contemplating what had I gotten myself into, I started noticing a few issues.

"What's happening here!?"

The more I looked at it, the more it looked like cutout #2 (second from the right) was too low, and that if I shimmed it up everything might fall back into place.

Measure with a laser and cut with an axe type of thing.

Now, I had to make an executive decision. I could either keep my “straight jig” and build a crooked wing, or adjust jig #2 and end up with a straight wing.

Duh!

Shimming jig #2 up brought the trailing edges back in line…

Cutout #2 waterline offset up

Now that's more like it!

… and the spar-cap trough… 

Much better

… and the leading edge…

Checkmate!

Yeah… I’ll keep that!

Marked the new waterline for when I build the left wing

In addition to raising jig #2, it had to be pushed back about ⅛" (3mm) from the black reference line in order for the wing surfaces to match without a step. 

Jig#2 backed off the reference line

This will be a problem again later on when both wing and jig are flipped 90º on that side.

Meanwhile, let’s bond the two bottom pieces before they move again.

FC2 and FC3 taped before bonding

A high level view of the job at hand

Foam bonded the same way as previously done with the smaller pieces

Used removable nails to prevent the foam from shifting overnight

Bonded the foam to the jig, top surface only, per plans.

Cleanup the next day

Next time we will be creating the wing root pocket on the first foam block (FC1), and begin installing the wing bolts mounting plates.

JT's right wing root pocket