Ch. 6 - Fuselage assembly - Part 12

Fuselage bottom (17.2 hrs)  

After getting the foam panels from Wicks, I sat them in place to check their dimensions.

Foam pieces covering the bottom of the fuselage

As you can imagine, the pieces had to be first bonded together with micro.

Micro in place to bond the panels together

Bottom panel curing

Because my fuselage is 2” wider, the regular 24”x48” panels were about 1.5” too narrow to cover the complete width of the fuselage bottom.

This foam is too narrow to cover the entire bottom of  the plane

Since the plans required that I trim the rear foam panel 0.25” past the back seat, this left me with plenty of leftover foam, which I then sliced into 2” strips, and used to fill in the missing width.

Additional strips glued to the side

Coverage is now 100%

Next step was tracing the bulkheads layout onto the foam floor from the inside. To accomplish this, the fuselage had to be moved back on the sawhorses, upside down.

I had to crawl inside the fuselage with a Sharpie

This are the outlines of the bulkheads I traced while inside the fuselage

Later, I drew the outline of the new aircraft bottom 0.7” outboard of this line, and used a saber saw to cut the foam along the outer one.

The outer line represents the outer edge of the fuselage

A few more changes to the floor layout were necessary due to the fuselage width change, as well as the moving of the front seat 2” forward. 

Brainstorming session caught on paper

As far as the shapes of the parts to be scooped out are concerned, I ended up first drawing their outer edges, then calculating and drawing an inner line representing the closest place to the outer edge with a full depth of cut.

Rear seat contour lines

Using a router, I dug along this inner line at full published depth.

No going back now!

Then again, to clear up all the rest of the foam.

Getting the rest of the foam out was more fun

This inner lines were prepositioned to achieve the angles required by the plans, 45˚ for the back side of both seats, matching the seat slopes, and 30˚ for the front of both seats. Everywhere else the angles were left to the builder, so I just doubled the depth of the particular cut, and drew the line inboard by that amount, this turned out to be 26˚, which should be nice and shallow for the fiberglass to follow with ease.

With the math sorted out, I cut along the diagonal connecting outer and inner lines, and went on to sand, sand, sand.

Rear seat, rear slope at 45˚

Rear seat, side slope at an arbitrary 26˚

Rear seat, front slope at 30˚

I used the same process for the rest of the fuselage bottom.

A lot more router action

I ended up needing a short recess for lunch, because I started seeing crazy things in the foam...

"Behold the Long EZ Tiki God!"

With my belly full, I felt much better and the visions disappeared, so I moved on to trying different cutting implements. 

I eventually settled on coarse saw, with a pretty stiff blade. This produced a rougher finish, but it did so in a fraction of the time, and since every tool I tried still required further sanding, the initial surface finish didn’t really matter.

Having a go at it with the Dremel

This took way too long, and was pretty stressful.

This ugly old saw did the trick

I had this roughed out in no time

It felt like sanding went on forever though, and I actually disintegrated 3 sheets of 30 grit and 2 of 80 grit.

All contours aft of the instrument panel finished

It still looks a little rough now, but it will be great once micro, epoxy and fiberglass do their thing.

Finally I flipped the fuselage back onto the bottom piece to make sure things were fitting alright, and I was pleased with the results. The seat lines flowed smoothly into the carved foam, and all the bulkheads lined up precisely.

Looking a bit tiny, I hope I didn't screw it up! I can't wait to get in there to try it on for size.

The rear space looks palatial by contrast

I did not carve forward of the instrument panel yet, because the fiberglass nose wheel cover I need to trace on the foam, has not arrived yet but it should be home about the same time I get back, so I will get on with it next week.