Monday, June 27, 2011

Ch 6 Begins: Time to Start Making a Fuselage...

Well it's been a couple of weeks since I finished the fuselage sides and although things have been quiet here, I have been working...just not as fast since I'm back at work now.  Unfortunately, I'm just now starting to have something to show for it.  Over the last two weeks I've...

- Performed some clean up of the fuse sides:  I had some areas I needed to smooth out with micro so it will look better when painted and I had some dry spots left over from some glassing I needed to repair.

Lowered table w/firewall mounted upside down ala Wayne Hicks style
- Spent a really annoying afternoon trying to level the blasted work table:  After lowering it to prepare for fuselage assembly, I shimmed it level, came back to check to see if it had settled any, leveled it again, etc.  I went through this a few times and then noticed that my level that had just told me the table was high on one end, now told me it was low on that same end...and I hadn't changed anything.  After doing some checking, I finally realized my level was bowed!  Not much...but enough to affect the SMART Tool digital frustrating!  I ordered a new one which came four days later.  PS: The SMART Tool digital level is a great tool...but be prepared.  If you're as anal as I am, you'll spend whatever time it takes to see 0.0 degrees level on the scale.  It doesn't have to be that precise to build the Cozy...but I should have a very straight airplane to for my trouble.

Stir sticks used to secure the final longeron positions
- Finished the Ch 4 temporary firewall by cutting the holes for the longerons:  I started by establishing the 23" Water Line and a centerline and then cut the main longeron holes per the paper template.  I left some side-to-side wiggle room to make adjustments on assembly.  Then I cut the other holes leaving both vertical and horizontal wiggle room. During the dry fit of the fuselage and after the positions were established, checked, rechecked, adjusted, and checked three more times, I glued some epoxy stir sticks on the back of the firewall around the final position of the longerons.  The thought is that this will provide an accurate template for mapping the holes to the real firewall and minimize any accidental oversizing.  We'll see how well this works out.

- And of course I did start the dry fit of the fuselage.  Onward.


Tuesday, June 14, 2011

Chapter 5 Fuselage Sides...check!

Wooo Hoooo!  Here I am...the proud papa of two new fuselage sides.

The final stage of cutting each side to the proper length was nerve racking to say the least.  If you built the sides exactly to plans, it doesn't leave you with much room to trim.  I only had a 1/4" of margin so I was worried that any mistake was going to leave me with a short side I would have to figure out how to fix.  I thought about it and played with different methods for making the cuts for 2 days before doing it.  In the end I believe I have two sides that are the prescribed 101.75" long...and I miraculously seem to still have the 5.5" width in the aft section for the spar cutout.  I ended up using the Fien tool with the multipurpose cutter to do the trimming.  I love it when a plan comes together.

The sides are a little on the heavy side.  I believe them to be about 12.3 lbs each...almost 1 lb heavier than the average (11.5) posted on the Unofficial Cozy Website.  I thought it was more like two lbs at first after measuring on my son's fish scale, but after some checking, I found out the scale was off about a lb at the 10 lb mark.  I don't have another scale that is capable of fractions of a lb up to about 12-15lbs so right now the 12.3 is my best estimate.  The extra weight should be mostly the repair I had to make to the aft section for air specks which added a top layer of BID per repair instructions and some extra UND glass.

Now it starts to get exciting.  I get to take all these smaller parts I've been working on and put them together into on bigger one that actually starts to look like something...maybe not an airplane...but definitely something other than just parts.   Onward & upward.


Monday, June 6, 2011

LWX & LWY Stringers...

Step 5 of Ch 5 started with the lower longerons (previous post) and then went on to installing the so-called LWX and LWY wooden stringers in the aft section.  These stringers form an important structural section that carries loads from both the center wing spar and the main landing gear.

The biggest issue I had here was that when the two stringers were lined up according to the proper measurements, the angles that were cut to fit the intersection of the two stringers (middle of pic) and the intersection of LWX and the lower longeron (bottom right in pic) didn't fit nice and flush.  I'm not blaming the plans here...I'll take the full blame on behalf of my cheapo miter guage.

The important thing was to make sure the 3 key measurements were correct: 5.5" from the aft edge to the vertical support, 8.7" down and parallel to the bottom of the top longeron, and 16.3" from the aft edge to the intersection at the lower longeron.  After those were solid, I adjusted the intersecting angles as best I could to get a better fit and let flox fill any minor gaps.   The pic shows the wooden stringers in place as well as the beginning work of step 6...which includes securing the electrical conduit cover and filling the voids with foam.  Next is securing the foam in place with micro, filling the gaps, sanding the section level, and glassing over this area to make it one solid enclosed structure.

It's not an illusion that my electrical conduit covers are slightly curved.  When doing some double checking, I realized that I failed to cut the conduit channel at the "recommended" 14.7" down from the longeron and instead cut them according to the plans 14.5".  The problem is that at the plans measurement, the conduit opening at the firewall will likely interfere with the rudder pulley mounted on the firewall.   The easy solution was to shape the aft part of the conduit cover with an ever so slight bend in order to exit the firewall below the pulley assembly.

OK.  I'm in the last step of Ch 5.  I'll have some fuselage sides done very soon.


Wednesday, June 1, 2011

Nice Curves...The Lower Longerons that Is...

Curvy Fuselage Bottom
Clamping tool used by many builders
The lower longerons go in pretty easy per plans.  The key is to make the necessary relief cuts for each curve of the lower fuselage side so the longerons fit well.  You will want plenty of clamps to hold the longerons down in the curves while it cures well.  Be sure to use the nails per plans to hold it in the proper location and then the clamps to hold it against the side while curing.  These two things working together made this easy.  It would be also helpful to make some small wooden tools (here we go again :-)  )  for the clamps to mate well to the top of the longeron stock vice trying to clamp the points of the triangular longeron.  In the pics, you can see the wooden clamp tools made from a spare 2x4.  As always, click the pics to enlarge.  My first one came out great.  I don't have enough clamps to do both at once so I'm waiting for the right side to dry now.
Clamping the Lower Longeron
TIP: I do want to mention something that the plans does not discuss and may cause you a pause.  Assuming you have done everything to plan, you may find that the lower longerons will overhang anywhere from .1" to .3" at the aft half of each fuselage side when placed in the appropriate location.  (see graphic below)   When I encountered this, I wasn't sure whether to go ahead and place them per the measurements from the upper longeron or line them up with the edge of the foam and just make sure they were the same on each side.  The plans clearly says to place the longeron at the specific measurements, but you know you start to second guess the meaning.
Click to Enlarge

Well, I found in the archives someone mentioning the same issue.  The answer was basically, don't worry about it.  Place the lower longerons at the proper measurements and let them overhang.  In a future chapter, when you shape the bottom of the fuselage, some of the bottom longeron will get sanded away anyway.  If there are any gaps left in the foam at that point, just fill it with pour foam, shape, and move on.  Below is a drawing I made to describe the problem to the Cozy Email Group before I found it in the archives.