The Long EZ Build: Fuselage cutouts

The first step is to mark the fuselage sides and remove the cutouts. These are the through-holes for the pilot and passenger stowage areas.

Page 21-2 in the plans give us the dimensions for these cutouts.

I had made these marks onto the fuselage way back in Chapter 7.

Don't pay attention to the triangle on the lower right - I had made that to help me orient the fiberglass when I glassed the fuselage sides a long time ago!

After verifying that all cutout dimensions were perfect (something about measuring 6546513584831 times and cutting once)... it was time to cut! So I took out my handy jigsaw and tested to see if it was up for the task. Here I am testing a cut on a scrap piece of fuselage side I had removed when making the fuselage cutouts for the center section spar.

The jigsaw is a little rough on the fiberglass.. notice how it causes a bit of delamination on the cut's backside edges...

Front side looked good, so I figured I would proceed with caution...

I made a hole for a starting point...

And cut away! No pressure... just butchering my fuselage!

I wanted to get close to the cutline as possible, but left room to fine tune it later...

I left plenty of room on the top edge since I was afraid I would eat into the top longeron...

Oooooooo...ahhhhhhhhhh!!!!

I then took calipers from the inside and outside, and realized that if I had cut my original 'per plans' mark lines, I would eat into the longeron by 0.1"... how could this be?! I checked and double checked my dimensions 6546813125684 times! I then looked at the plans and started to question if something was wrong there... nope! Everything seemed to check out in the plans too! So why the discrepancy?!

I went back to Chapter 5 (pg 5-2) and I realized that the top longeron and stiffener should be 1.4" tall (top longeron 1" tall + 0.4" tall stiffener)... mine was 1.5" tall. Why?! So I went back through my purchase logs and realized I had purchased a 0.5" stiffener. Perhaps Aircraft Spruce didn't have a 0.4" tall spruce cap back when I made the purchase and figured adding 0.1" wouldn't hurt? Who knows - the point is I found out why I would eat into the lower part of my top longeron by 0.1".

So now I had two options: A) mill 0.1" off the bottom longeron, or B) keep the longeron as is, and sand the outside opening to the correct opening - creating a small 0.1" ramp to transition from the bottom of the longeron to the top inside skin of the baggage compartment.

I scrapped option A since I didn't want to mill the longeron bottom - removing fiberglass layups and weakening it. So I went with option B.

I used the multitool from the inside of the fuselage to cut flush with the longeron's bottom.

A little sanding and fine tuning.. and it was good to go!

I then repeated it for the other side...

Rough cut... but later gets trimmed with finer precision...

UPDATE:

After I made the ribs and bonded them to the fuselage (next post), I was asked, "Why aren't you doing the passenger elbowroom mod?!"

Currently, the aft vertical line of the passenger cutout is 15" of the forward face of the spar. Recent builders have extended this cutout so that it is only 6" of the forward face of the spar. This pushes the BAB bulkhead farther aft, allowing the passenger to stick his or her arms/elbows inside of the stowage compartment. It may sound negligible, but believe me - every extra bit of elbowroom, legroom, shoulder room is EXTREMELY valuable!

Here is the original "per plans" setup...

I removed the BAB bulkhead... and took these pictures to demonstrate the difference... notice with the original cutout, the passenger cannot stick his or her elbows inside the stowage area...

This is not comfortable! Thumbs down for sure!

By extending the cutout farther aft, the passenger is able to stick his or her elbows inside the stowage compartment with no problem.. giving them a much more comfortable ride! Thumbs up!!

Before I had committed to the decision, I had made a few "back of the napkin" calculations to see the effects from a structural point of view. The results indicated that extending and moving the inboard edge of the BAB bulkhead aft 9" did increase the stress concentration by a hair.

However, what concerned me even more was that on the left side (the port side), there is a high chance that the passenger will step on the top inboard skin of the strake while boarding and deplaning. Moving the BAB bulkhead farther aft increases the area under the skin without any support under it (think of a roof without any columns underneath it for support - you can't just remove a load bearing wall, else the roof might collapse!). Given enough steps, this portion of the skin might warp or buckle.

So to put my mind at ease, I decided to go ahead with the mod BUT also add a bulkhead perpendicular to the fuselage wall near the pilot's seat. This way, the top skin will have plenty of support should the passenger step on the strake's top inboard skin.