Chapter 14 - Section 10

Installation to the Fuselage

 

Trial Fit

It is recommended that installation of the Center Section Spar should not be done until the wings and ailerons are built and match drilled to each other. However, it is rewarding to see a trial fit...

 

The center section spar fits into the fuselage slot without any difficulty. I shimmed the spar with 2 stir sticks to the left and was able to line it up to 0o with my digital level and visually lined it up with the canard trailing edge... My center section spar weighs just a hair over 41 lbs.

 

Now onto Chapter 19....

 

After mating the spar to the wings in Chapter 19, its time to install the spar to the fuselage such that I can complete the torque tubes, etc.

 

Engine Mounts (EM-2)

My EM-2's are a bit larger in size than plan because my inserts at the firewall are 1.75" round discs instead of 1" x 1" squares (Chapter 4 Step 5). I made the EM-2's out of 2024 T4 (instead of T3 because that's what I have on hand) with the size large enough to cover the entire disc area. I rounded off the corners and shaped its edges to fit into the fuselage corners. Per plan, I applied flox all around the EM-2's, then I applied 1 layer of BID and peel plied.    

 

 

 

 

 

 

Centering the Spar

I slid the center section spar into the fuselage opening per plan. Besides leveling the fuselage and spar side to side and front to rear, I must check the skew of the spar by measuring from each end of the center section spar to the tip of the nose. However, I do not have a good center spot at the nose to measure, so I made a simple fixture (as shown) and clamped it onto the center of F28. It consists of a piece of scrap wood, a small screw, and a picture hanging cable. This way, I can swing left and right while squaring out the spar to the fuselage.   

 

 

 

 

 

Here's a picture showing my alignment approach. I mounted two (2) level boards on the spar (earlier), just in case 1 breaks off. Since they were in tact, I used the second one as a backup. I also used a plumb line to make sure the spar is lined up to the center of the fuselage. The bubble level (that I hot glued to the aft face of the spar) gave me a rough check on the leveling of the spar as well.

 

 

 

 

 

 

Here's an angled board resting on top of the upper longeron (WL23). Note the horizontal line I drew on the vertical leg - which is 5.6" below the top of the upper longeron or WL17.4. I used it to verify the height of my spar to be at WL17.4 exactly.

 

    

 

 

 

 

 

 

 

 

 

 

 

 

Murphy Strikes

After everything was lined up, I filled the gaps between the spar and the fuselage with flox, doing it in two stages - the front & top first, let cure overnight, then the bottom. I did this because I have the shims at the bottom and I do not want to flox them in. The next day, I double checked all the alignments one more time (it was perfect), then I removed the bottom shims, and completed floxing the bottom gap.

 

While I was waiting for the flox at the bottom gap to cure and calculating the BID tape requirement, I came across the M-8 drawing again and it just dawned on me that I mounted the aft face of the spar FLUSH to the aft side of the firewall - it should have been flush to the forward face of the firewall.... Aaagh!!! A quick call confirmed my intuition - I need to cut the spar out and re-do... The partially cured flox (at the bottom) was not bad, I have to cut off the cured portions with my FEIN and hack saw. What a mess... I did measure, measure and measure as all builders would, I just didn't READ, READ and READ! After half a day of re-work/sanding and lots of !@#$%, I was back on track.

 

Floxing the Spar to Fuselage - the Second Time

The second time was a bit easier. I re-shimmed and clamped the spar in place, making sure its 0o front to back and side to side (as the fuselage). Since I moved the spar forward 1/4" it actually fits better and the gaps (at the front) were smaller. I floxed all the gaps as before and let cure.

 

Glassing the Spar to Fuselage

Before the glassing task, I roughed up all the areas and rounded off all corners with flox. I also removed the rear most section of the torque tubes and covered up their brass bushings with masking tape. I glassed the spar to the fuselage per plan with 5 layers of BID on all sides, except the 3 long BIDs between and spar and firewall - they were 2 layers each. Once completed, I re-confirmed its alignment and allowed to cure overnight.

 

Mounting the Wings to the Spar

This is one of those moments you look forward to ...after all those alignment efforts in Chapter 19, Section 12, I balanced the main wing on a 4 wheel roller cart and lined up the 3 mounting holes in the spar and wing. It took Susann and I quite a bit of joggling to line up the bushings between the spar and wings. Once they lined up, the bolts slipped through nicely. 

It was most rewarding to see our Cozy spreading its wings for the first time...

 

 

 

 

 

Noodly Effect

Once the bolts were in, I placed the digital level on the level boards (spar and wing) for verification. My spar showed 0.0o (same as the fuselage) while both wings showed TE up by 0.2o . My first attempt to rectify the mismatch was to add a thin washer (AN960-816-L) between the outboard lower bushings as recommended per plan. With a bit of struggling, we finally got it in. But the digital level now showed TE down by 0.2o - which is a 0.4o correction (and in agreement with the plan's estimation). It became obvious that I should get a washer that is 1/2 the thickness (i.e. 0.015" thick). I found a stainless steel shim washer from McMaster-Carr which will fit the bill. However, I decided to post the question to the Cozy forum first before diving in.

 

I received a few e-mail responses and a call from Wayne Hicks within 15 minutes... what a support group!!! Wayne pointed out that the spar is still a bit noodly (hence the noodly effect!!!). I believe the weight of the wings (& winglets) caused a twisting moment at the spar, especially without the support of the strake causing the TE up effect. Most recommendations were to hold off any washer corrections until the strakes are built.

 

After giving it some more thoughts on the above comments, I took a couple of stands and propped up just slightly at the TE of the wing next to the winglets and voila... I got my 0.0 degree back - no washers needed.

 

Now, it is time for me to jump back to Chapter 19, Section 11 (Controls), to complete the torque tube linkage between the ailerons and the control stick...  

 

[Hindsight 09/2010] At this point of time, I have the engine mounted onto the firewall and the upper cowling in place (that required mounting the wings back on). I get 0.0o on the left wing an 0.1o up on the ring wing. I may not need to add any washer after all.

 

[Hindsight 08/04/2012] I have to remove the wings for seam treatment between the wing root and center section spar. After putting both winds back and bolted down, I got 0.0o on the fuselage and both left and right wing. The engine is not mounted at this time. Regardless, the wings are close to balance.