Ch 20 - Winglet and rudder - Part 1

Bottom winglets (28 hrs)

From now on, in an effort to better keep you up to date, I will  jump back and forth between current events, and JT’s latest upgrades (already completed). Hopefully this won’t be too disorienting. 

Since JT is now back at the hangar, and I still had the rest of September off from work due to the pandemic, I found myself with a lot of free time. Laying on the couch working on my CFI renewal suited me just fine, but my wife quickly picked up on the situation, and started dropping hints about holes that needed to be dug in the backyard, and other general gardening nonsense.

This was the time #2 (formerly #1 before JT took over my life) had been waiting for during the past four years, when a sudden urge to return to proper building became too hard to ignore.

With the executive decision made, and the gardening specter no longer looming over my newly found freedom, all I had left to do was choose what to start working on. 

Being a bit out of practice, I really wanted to start with something smaller and easier to manage, but big enough to feel like progress would be made, and the lower winglets seemed like the perfect fit. 

The hardest thing would be digging the cores out from wherever Gina had stashed them four years ago. Eventually though the foam was found, and this show was able to get back on the road.

The foam the cores came from was split in halves to be used as stands for glassing the winglets

I trimmed the the cores exactly per plans

Cutting your parts is always a bit scary

Bottom edge of the lower left winglet radiused 

Turning the donor-foam into supports

Support needs to be smaller than the winglet

This will allow the fiberglass to wrap around the rounded edge some

Fiberglass from the opposite side will eventually overlap over the rounded edge making a strong structural joint

I'm using glue between tape to make sure I don't damage the foam

A little weight while the glue hardens helps

Peel ply is held with staples in the trailing edge juggle

Next, I prepared four plies of UNI @45º (two for each core), and added duct tape to the foam to simplify cleanup. 

Hadn't used this table in a long time

Tape helps with clean up the next day

Stage is set

Then went back to the business of fiberglassing.

Micro-slurry over foam

First layer of UNI 

Black mark helps me keep the proper orientation of multiple layers

Second layer of UNI

Layer orientation is easy to screw up. The two marks confirm all is well.

Making sure the UNI wraps all the way around the bottom edge

Wouldn't want the FAA to think someone else built this thing 😂

Peel-ply added to all places where a secondary bond will occur

Of course, all of it had to be repeated for the other winglet.

Micro-slurry

First UNI layer

After adding epoxy

Second UNI layup

All peel-plied up

Curing overnight

The next day started with trimming the winglets.

Always looks sharp as a porcupine, and rough as hell the next day...

...until it gets cleaned up a bit, that is.

Because I didn’t add micro to the trailing edge juggle when it was wet, I took the opportunity to do it at this stage, but I used flox instead of micro because this area is easily banged into in the hangar, and I wanted it to be a little stronger.

Isolating the trailing edges

Floxed and peel-plied the trailing edge 

As always, the next morning started with a cleanup from the day before.

Cutting off the trailing edge support foam (aka fishtail)

Tacks holding the trailing edge peel-ply exposed

Crusty peel-ply being removed from the trailing edge

A before and after shot of the trailing edge

Once again

Luckily I didn't spill any blood on these tacks like I did on the canard

Tacks and peel-ply on the way out

Cleanup complete

Then I set up for fiberglassing the opposite side.

Reusing the opposite side of the donor-foam

Exciting gluing action 😂

Winglets placed at the corners of the table to ease glassing under the overhang

The process should look familiar at this point.

Dry-micro filling damaged foam sections

Micro-slurry over foam only. Note the foam removed from rear bottom edge.

Pure epoxy in structural bonding area

Flox at the bottom rear edge makes the structural bond with the glass possible in a sharp corner

First ply of UNI

Second ply

This time around I decided to try Terry’s unconventional technique of peel-plying everything in sight. This would make my life easier later on by reducing sanding chores, and unavoidable damage to the outer fiberglass layer.

Trying JT's builder's technique

I'm gonna go through a lot of peel-ply this way

Conventional wisdom has it that the extra epoxy trapped by the peel-ply will add weight to the final structure, but at slightly less than a thousand pounds in fully redundant IFR regalia, JT is not a heavy bird by any measure, so perhaps the idea is worth a shot. 

I usually cleanup all straggler filaments left behind by peel-ply by sanding them off the structure, and with them most of the added epoxy. This extra epoxy ends up protecting the fiberglass below as I sand the surface smooth, and might actually prove to be a win-win situation.

Meanwhile, there goes the other winglet…

Second ply about to be glassed under the overhang

Both winglet bottoms done!

Another look at them

Another day went by to allow for curing time, then the peel ply was ripped off, and the cleanup began again.

Peel-ply overlaps leave a small ridge of epoxy between plies that need minor sanding

Here's a before and after cleanup view. A lot of the extra epoxy was sanded off.

Two lower winglets completed. The upper ones will get done next time.

As you can see, even though I peel-plied the entire outer surface, I ended up sanding a lot of the extra epoxy off the structure. Furthermore, I was able to sand the surface smooth without damaging the underlying fiberglass structure, unlike what usually happens when sanding is done just before applying the finishing micro.

It is still a lot of grunt work, but the surface is already smooth enough for finishing now, and the strength of the part was not compromised in the process. 

The yellow dust is epoxy sanded off the winglet surface

I have to say I am liking this technique so far, even considering the added sanding step, and I have the feeling the weight penalty might likely be negligible.