Ch. 5 - Fuselage sides RH - Part 1

Glassing the right fuselage side (8.5 hrs)

Coming home late the other night, I decided to sand the shaped, yet unfinished right sidewall, while standing it back to back with the finished left sidewall (bad idea). I figured I'd make them identical.

Unfortunately, due to my tired state, I sanded it at an angle and never noticed it (so predictable).

I woke up the next morning refreshed, and ready to glass the right side. Luckily, I took some time beforehand to double check the positioning of the gear mount, LWX, and LWY on the sidewall (second smart thing I did). Good thing I did, because nothing fit right anymore!

After shifting pieces around numerous times to no avail, I eventually measured the size of the sidewall every 10", and what I found was a bit shocking. I was missing 0.2" to 0.3" (5 to 8 mm) just about everywhere! 

Initially, I couldn't figure out what had happened, then I remembered the late night sanding session, and I became furious with myself, and also a bit unsure about what to do next. I wanted so bad to proceed anyway, but the gaps were just too big. So, I took all the scraps I had saved (first smart thing I did), and glued them back to the bottom of the fuselage side.

Glueing foam scraps back onto the bottom of the sidewall

Same thing seen from the other side

I let them cure overnight, then basically started all over again by remeasuring the fuselage side, marking it, and cutting it one more time. 

You can see how much foam I had to add back

This mistake just set me back two days, but it goes to show two things:

First, you shouldn’t even think about touching the project when you are tired. 

Second, this type of construction is very forgiving, and there is no reason to having to live with your mistakes, instead of fixing them.

Here’s one of the problems that were fixed by adding the missing foam...

The simulated longeron is glad it doesn't have to stick out of the bottom of the airplane anymore

In this case part of my lower longeron would have been sticking out the bottom. Not cool!

Having solved the latest crisis, I moved on to glassing the right sidewall.

I was curious to try out the latest gadget... I mean, indispensable tool... I had picked up at LOWES a few days prior. 

Cutting through UNI the lazy way

At $28 it’s not cheap, but I will still be cutting hundreds of yards of fiberglass, and  so far, none of the methods I’ve been using has been without problems.

The “pizza cutter” rollerblade method is pretty good, but the cutting edge quickly develops a few dull spots that leave a number of uncut strands with every pass, that are impossible to see. When you try to remove the cut piece, these individual uncut strands pull partially out of the weave, and also pull the weave out of shape. The solution is to slowly pull on the piece just enough to identify where it has not been cut, then use the “pizza cutter” over the same cut again. This is slow, tedious, and never ending, if you don’t follow the original cut precisely, since you will have just created another cut in the glass with identical problems.

The scissors method is cheap and definitive, but BID is so sensitive that the mere opening and closing of the scissor can sometimes deform the weave.

On the contrary, using the new tool, the cut edges of the glass are nicely sheared, and there is no up and down scissor-like motion to disrupt the cloth. This cutter has been working well enough so far to make me want to keep it around for more testing. 

Nicely cut edges

Pressing on!

As on the left side, I started slurrying the right sidewall.

Micro-slurry contagion spreading

I then added dry-micro to fill some dents in the foam, and created a fillet in the joystick depression to help transition the UNI.

Looks like Meteor Crater in Arizona

I had heard enough tales about what a pain it is to make the UNI conform to the side-stick cutout, that I decided to go overboard with the size of my fillet, in an effort to make the transition super-smooth.

Close up of Meteor Crater

This effort really made laying the glass in the hole easy. I don’t want to jinx myself, but I think the UNI is down in there without any air bubbles.

Laying UNI at 30˚

As I mentioned while working on the left side, I decided to use a peel-ply sheet on the whole right side, rather than tape, in an effort to cut down on the evil loose peel-ply strands, that are in the habit of sticking to my work well after their time is up.

Peel-ply covering the entire sidewall

I would say that working with the peel-ply sheet was very easy. 

Sadly though, dozens of little epoxy bubbles did form under the peel-ply every time I left the shop. I think must have gone back at least three more times to squeegee them off the side of the piece, leaving a perfectly smooth surface every time, only to see them reappear later. I have no explanation for this behavior, I suppose I will just have to sand them back down after the peel-ply sheet is removed.

I didn’t take any pictures of them before I left, but I will in a few days, when I return home. Hopefully that is the only small issue I’ll have to deal with.

Ch. 5 - Fuselage sides LH - Part 5

Gear hard-point glassed (8.1 hrs)

I started the morning making sure the foam did not stick up above the wood...

... then marked the positions of the local buildup for the gear mount extrusions...

... taped anywhere I did not want epoxy to go...

and cut all the fiberglass I needed.

For the eagle-eyed out there, the bigger fiberglass pieces should have been cut at a bias. I didn’t realize what I had done until after I took the picture, and ended up having to cut it again.

The big plies went on as usual...

... but I decided to pre-preg the next two 15 plies buildup, to make things less messy.

Next, I peel-plied everything. 

No more “Mr. Nice Guy”!

I am sick of the little peel-ply strands leftover after removal!

The next morning I ripped it all off... 

... and I still had the strands to contend with!

I think I’ll use a single sheet of peel ply next time.

Here’s what it looks like after trimming it, and attempting to remove the loose strands by sanding.

This side is nearly done. All that is left, is to drill eight 1/4” bolt holes, and attach the landing gear mounts.

But I still have to counterbore four of its holes, Alodine it, and make some steel bushings for the main bolt holes (to be slightly enlarged) to reduce future wear.

Stay tuned, I will start the right sidewall soon.

Ch. 5 - Fuselage sides LH - Part 4

Foam filler (1.3 hrs)

I just got back this afternoon from Germany, and I am pretty tired. I did want to take care of one small thing though, so that I could be ready for tomorrow’s big layup.

I have to fill the space between LWX, LWY, and the lower longeron/stringer combination, with foam.

Space to be filled with foam

Luckily, I saved all the small pieces that were left from cutting the fuselage sides, so I had plenty of scraps to chose from. Like a jigsaw puzzle, I found some matching pieces, then I massaged them a little with a sanding block, before glueing them in place with some micro-slurry.

I decided to tape the wood up because I will have to make a structural connection there tomorrow, between the wood and 6 plies of BID, and I did not want any glass bubbles to weaken the bond.

I used West System epoxy because it cures fast, so it’ll be ready to go by the morning.

Ch. 5 - Fuselage sides LH - Part 3

Rear longeron (2.5 hrs)

The list of things to do this morning was pretty short. Number one on it was finishing the lower longeron by adding a triangular stringer.

First thing to do was removing the nails, which was accomplished in a very traditional manner, twist and pull.

Then I got sidetracked admiring the sidewall, and decided to go for a “glamour shot”. I figured it would be good for showing how all the bulkheads will eventually fit together.

After the motivational interlude, I got busy cutting and fitting the stringer, basically the other half side of the rear lower longeron. 

I used plenty of wet flox on the mating surfaces, since it’s easier to clean up the excess, than it is to add more later.

Then I threw every clamp I had at it, trying to bend it to match the other half. 

You might ask why I didn’t cut slots on the stringer as well, to help bend it. The answer would be, I’m not sure. But looking at everyone else’s photos of this step, no one else has found it necessary to do so, and the manual is mum on this technique as it applies to this part. 

Maybe cutting on the base of the triangle might weaken it too much. Again, I’m not sure, but enough force was brought to bear that it never became an issue.

Pretty much everything I've got!

With the flox curing I had nothing else to work on, so I went back to the lathe, and mill, made a test bushing out of some scrap, and pressed it in some leftover aluminum angle I had laying around.

This test piece has demonstrated counterboring (top hole), and now press fit steel bushing.

The reason I am even experimenting with this, is that in CP #46 (Builder Hints), Burt states (talking about the landing gear extrusion in LMGA assembly): “ ... if you bought your extrusions from Brock, you will note that they have flanged, steel bushings pressed into the aluminum angles, these steel bushings ... are an excellent idea.” 

Unfortunately he gives no dimensions at all, so I am polling all my builder friends, and trying to come up with some I can use.

UPDATE: Wade just phoned in with some dimensions he called “exact”. In reality he probably made them up to shut me up, but I’ll try them on for size next time around anyway.

Ch. 5 - Fuselage sides LH - Part 2

Lower longeron (6.7 hrs)

The good news is that the air bubble I was chasing last night is gone.

Bubble-less surface

Unfortunately the bad news is that another bubble appeared somewhere else, and I’ll have to "terminate her".

No, it's not a snake!

Since I did not use any flox to radius the 90˚ angle above, I was almost expecting air bubbles to appear at the intersection with the foam board. I’m actually surprised I did not get any more than that. In retrospect I should have eased the transition, and I definitely will when I make the right side-panel.

To correct this issue, I had to drill two holes at either side of the bubble, and inject some epoxy with a syringe I "borrowed" at my last dental appointment.

I was told this should work, but I had never actually done it before.

Wow, that was awesome! I will definitely use this technique again next time I screw up.


By the way, I ended up drilling another hole further to the left, and filling the remaining void with epoxy.


One additional item I had to take care of, was the removal of BID I had laid on the last 0.5” of the longeron. Apparently it wasn’t supposed to go that far, so I took a razor knife and cut it off. Simple enough.

BID extending all the way to the rear end of the top longeron

Removing the offender

Problem solved

The new item for the day was the lower longeron. I drilled holes through it, and the cured fiberglass, and inserted some nails to hold the wood in place. 

Working on the lower longeron

Because the longeron needed to curve upward in the aft section of the fuselage, I cut some slots on the top side of the longeron, to aid in achieving the proper curvature.

Slotted longeron temporarily in place.

"Nice curves!"

After dry fitting, I mixed some wet flox, applied it to the longeron’s back side, and put it back in position.

Applying wet flox while "enjoying" the hot and humid midday

A substantial amount of weight is useful to hold the longeron down while the flox cures, but its sharp edge makes it challenging to weight it down without damage. Since I am not that smart, I will admit to shamelessly plagiarize the following “load distribution scheme”.

I wish I could take credit for this idea

Basically it consists of a grove cut into some scrap lumber, matching the triangular profile of the longeron. This was easily accomplished with the table saw, and the results were as brilliant as the individual I stole this idea from (thanks again Walter).

I was then able to pile up as much weight as I could physically fit on top, without any fear.

Plenty of weight holding things down while the flox cures