Servos

A rainy day yesterday meant no yard work, no bike riding, but I got a chance to work on the plane for a bit.  

I mounted the stab and rudder servos in the tail.  These are relatively easy mounting options because of all of the room I have back there.  I will create access doors in the sheeting to allow for maintenance.  This should make for nice tight linkages, and with the short tail moment I should not suffer too much on the nose weight penalty.

I also figured out how I want to mount the wing, and it will be a simple flat plate bolted to another mounting plate inside the fuselage.  Here is the 7ply 1/8" wing plate epoxied to the center panel.

No building but a new chapter

I spent most of the morning at the Toledo model show yesterday.  As always it was a fun event right up until the lights went out.  Not sure what happened, but emergency power kicked on which meant we only had about 25% of normal light.  Tough to see small model stuff like that, but oh well.

My total excitement for the day came when I finally signed up for the Society of Antique Modelers (SAM).  Now, if I could get these guys to have contests on the weekends I would be able to participate!

I will proudly join Jay, Kent, and Hank in Chapter 111 of the Bluegrass Cloud Busters!

Back to the wings - aw sheet

Time to move back to the wings.  A couple of major steps needed to be taken to start to get a real feeling of accomplishment.  First, the center wing halves were attached by sandwiching the 2 spars with pieces of 1/8" ply, and creating a flat base for the leading edge to tie into.  Each 'tip' is 6.5" off of the table.

Next came the leading edge sheeting.  I was looking forward to this because I knew it wouldn't be easy with the compound curves and had already decided to use a planking method similar to the way I have built boats. So one by one I measured, cut, fitted, measured, cut, rinsed and repeated multiple times until I got both side done. They turned out great, but look worse than they are.  Using the hot iron method it tends to instantly dry any surface glue that may be on the wood, so you can get the dried glue marks.  These are not big globs of dried glue, and you can barely feel it when running your hands over the wood.  A light sanding, and the top LE sheeting is good to go.  I also completed the bottom of the LE sheeting using a single piece, but no pics of that yet.  The top and bottom added significance stiffness to the structure!

The stab

In order to finish the fin and before I could start planking the fuselage, I needed to figure out the full flying stab controls.  I had already decided on a bell crank style with a center pivot, but I'm a visual person and wanted to be able to hold the stab up to the fuselage while building the pivot point.  Again, this plane has no instructions and the plans don't have this laid out, so it's design as you go and it was time to start the stab.

This thing seemed a little overly complex / engineered, but I'll chalk it up to the journey that counts.  I could have built a simpler version with the same shape, but chose to stick with the 'stock' method as much as possible.  It's basically a 3 spar system of hard 1/8" tapered balsa with the 1/16" x 1/8" rib strips.  Then the entire subframe was wrapped in the top and bottom sheeting and rib caps added to round it out.  It does produce a very stiff and lightweight stab, and these stabs are as big as some of the wings on my park fliers!

First, I created a pattern of the stab sheeting using file folder card stock.  Then I transferred the pattern onto 1/16" x 4" sheets of lightweight balsa.  It turns out the 3 pieces make up each half, so I had to join them together to make one connected sheet for each stab half.  I use the method of a covering iron turned all the way up to superheat the Titebond glue and cure it extra fast.  I also use this method to attach sheeting to wings and things.  Then I use a piece of ceramic tile as my surface because the glue won't stick to it, and the heat of the iron won't affect it.

I used the surgical rubber method of attaching the pivot connector to each stab half.  The pivot rod is a piece of hollow carbon fiber rod that slightly presses up against the surgical tubing which has been glued to a hard piece of balsa on the center spar.  This grips the rod and holds the stab tight.  Worked well on my Genie, and should work fine here too.

Next, the sheeting was attached using the hot iron glue method.

And then I could get started on the control mechanism.  I made a bell crank out of some spare computer board material that I have from a flatbed scanner that I tore apart a few years ago.  The stuff is very stiff but easy to work with, and I've used it for control horns and other bits in the past.  You can see in the pic that I added extra bearing surface to each side so it fits snugly between the hard balsa rails, and also adds more stability as it pivots on the brass carrier.

After getting the alignment correct, it was just a matter of inserting aluminum recover tubes into each stab half to receive the bell crank rod, and the controls are almost ready to go.

Tackling the tail

Time to get started on the fin and rudder.  No real surprises here.  It was just a little thicker and swoopier than normal.  Upon the suggestion of Jay Burkhart, I added some cross grain ply to each side of the top of the fin to make sure it didn't break on a flip over.

The rudder was built on end.  Again, no surprises here except when I had to rebuild it after building it backwards as you may be able to tell in the picture....

And finally, you can see here that I've started thinking about mounting the servos in the tail.  PLENTY of room back there!

Fuselage formers

The formers are next.  The first three formers are 7 layer 1/8" plywood.  The remaining formers were made using hard 1/8" balsa.  The patterns were spray glued using 3M spray adhesive and attached to the wood.  Then I used my scroll saw to cut everything out.  Pretty standard.

Next, I had to attach them to the crutch.  I suppose I could have oversized the formers and cut them off the crutch later, but I chose to use a small dab of hot glue at The base of each one.  I can cut through it later with a hit wire for easy removal.  At least that's the plan.  

Of course I used my laser again the ensure everything was nicely lined up.

I then created a backbone using a 1/4" x 1/8" piece of spruce.  I notched each former along the center line and glued on the spine.  I will do the same to the bottom when I remove the partially sheeted fuselage.

And last but not least, I used 1/4" x 1/8" hard balsa to create lateral side spines on the fuselage as well. 

Next, the tail.....

Starting the fuselage

The fuselage on this beast is beautiful, and intimidating at the same time.  I was now far enough on the wings that I needed to create something new, so the fuselage was up next.

There are a number of ways that I could have built the fuselage, but I chose the crutch method mainly because I've always wanted to build a fuselage like this, and what better time than now.  Besides, there are no instructions to tell me that I'm doing it right or wrong, so the crutch method it was.

The first thing I did was lay the plan out on my drywall board and mark the former locations with a finishing nail.  By nailing down through the plan and numbering the marks, I could remove the plan and lay it out for reference without covering it up.  In this case, I taped it to the door of my workshop.

After getting the formers marked on the board, I needed to build the crutch system.  First, I taped a straight edge to the door that connected the main wheel to the bottom of the fin which creates a perfectly level and even edge at the bottom of the fuselage.  Then I measured from the line to the bottom of the former on the plan, and recorded that on a notepad.

After that, I cut some risers and base pieces for the crutch system.  I had some scrap hardwood and composite board that had nice straight edges.  I cut them up according to my measurements, glued and screwed them together, then mounted them to the board according to my nail marks.  In order to ensure a nice straight fuselage, I also setup my laser line and marked each crutch center line as I screwed them down to the board.

Next, the formers......