Contouring and Covering the Sides

So the summer building season has drawn to a close, and it’s time to get serious about getting caught up with the ol’ blog.  Back in June, I was preparing for covering the sides of the fuselage, and the last step is carving the contours of the top of the fuselage.  The first step in contouring the fuselage top is cutting out the section in the front for the canard.

To be CUT!

As you can imagine, this is rather gut wrenching, taking a saw to this beautiful thing you’ve been working on for nearly a year.  Anyway, it has to be done, so I cut this out with a combination of a Japanese flush cut saw and the Fein tool.

I then used the templates from the plans to carve the tops to the pleasing rounded shape. I really enjoy this kind of work, though I tend to be a bit too much of a perfectionist for my own good.

Though I read and re-read the plans, I have found yet again that perhaps I should get a second opinion on things that are a bit confusing.  I misread the section that says where the final template should taper from, and wound up starting my taper back to the spar much further forward than the plans would lead you to.  In all, it just means the outside of my fuselage is about 1/4″ wider on each side at the seatback, and the general consensus is that it will not affect anything down the line.

My parents were up visiting for 4th of July weekend, and I put Dad right to work. He, Heather, and I got both sides of the fuselage covered over the course of the 3 day weekend. Again, I can’t imagine trying to get all of that done without the extra hands.

Covered!

My posts are going to be a bit light on the text for a while, I’m going to try to see if I can get caught up since I can’t spend as much time building.  At least until I get the heat tent in the hangar reconstructed and a new outdoor cover for the heater.

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Rotisserie Building

Before the sides can be covered, they need to be contoured.  Before they can be contoured, the fuselage needs to be moved from the table, onto a support structure that will allow changing the orientation of the fuselage easily.  This structure should also allow easy access for covering and contouring.  Here’s how I built my rotisserie.

I first built two tripod looking support structures, each on casters, as seen below:

Rotisserie End

Once these were built, I needed to decide how to support the fuselage while allowing it to rotate about its longitudinal axis.  The plans call for reinstalling the false firewall with a hole drilled in the center, and then drilling a hole in F-22 to be filled in later. I took the plans advice on the aft end, but didn’t like the idea of cutting holes in my bulkheads. Here’s a look at what I built on the forward end:

FWD Support

This support allows for a bolt to be used as an axle, but outside the forward end of the fuselage, so no holes in the fuselage are required. It is crucial in building this support to have the tolerances pretty tight between the top and bottom of the tub and the bracket, so that when the fuselage is rotated, there is no bumping it around.

Here’s a look at what the aft end looks like:

AFT Support

As you can see, the crossmember in the aft support is significantly longer than the forward support, this allows me to drill holes in either end, and match drill holes in the temporary firewall, allowing me to lock the fuselage in any orientation I desire.

You can also see in the above pictures that additional wood has been added to the rotisserie underneath the original strut design.  This consists of 2x6s providing additional structural support, while raising the structure up a bit higher, which provides additional ground clearance for turning the fuselage. You can also see I have slats running the length of the fuselage, tying the bottoms together.  This prevents the two supports from spreading apart at the bottom due to the weight of the fuselage.

And of course, I had to get Heather’s approval:

 

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Covering the Bottom

So the last few posts have been building up to this point, covering the bottom!

Having reinstalled the landing brake, with a few dabs of 5-min epoxy, sanded the depression all around it, and built the duct tape buildup around the brake area… don’t remember if I covered that before or not.  Either way, I don’t have pictures of it.  I’d also completed contouring the sides and bottom, installed the step reinforcement, and installed the nav antenna, so I was ready to cover the bottom!

I mentioned my readiness to cover the bottom at an EAA Chapter 478 meeting, and had a couple volunteers to help me out.  Doug Crane, of www.craneplanes.com was quite interested in helping out. However, the very next day Heather and I got off work about the same time, and the weather was perfect, so we set about glassing the bottom!  It really isn’t a difficult layup, much easier than the inside layups, it just takes time because of how large a surface it is.  With both of us mixing epoxy and wetting out as quickly as we could, it took right about 3 hours.  Here’s a few pictures of the process:

Getting the cloth laid out

Ok, so I have ONE picture of the process, and a couple shots of the layup already peel plied:

I tell ya, the extra layups around the hardpoints for the landing gear and the engine mount were a PAIN.  It’s quite difficult to get the cloth to laydown straight around the bend of the corner.  Thankfully, I had rounded the corners off enough that we didn’t have any airbubbles form around the corners. Still, there was quite a bit of grumbling and getting frustrated involved in finishing these reinforcements.  Many thanks to Heather for taking over on the last one when I got too fed up!

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NAV Antenna Installation

So I’m finally back with a new post.  The last several weeks have been rather hectic around here, starting with a trip to Oshkosh (awesome), followed by weeks of the annual inspection on the Tri-Pacer (not quite as awesome), culminating in  hurricane Irene generally making a mess out of things (not awesome at all, my man cave basement is toast!). Now we’re back to building most days, though the remnants of a tropical storm are rolling through southern Maryland as I type this. Time to try to get the blog back on track of keeping up with us. The activities described below took place around June 18th, 2011.

Back in the end of June, we were getting ready to fiberglass the bottom of the fuselage, and the last task in our way was installation of antennas in the bottom. Some people have put as many as 3 different antennas in the fuselage bottom, I’ve elected to keep it simple and just put a NAV antenna down there.  We can get glideslope by building a splitter for a NAV antenna if we decide we need it, and marker beacons are quickly becoming a thing of the past.

I had ordered the supplies for building the antennas for the plane long in advance from Jim Weir, thinking that there may be a long lead time. The lead time turned out to be too long for my liking, and I wound up buying the copper tape, coax cable, and torroids from Aircraft Spruce.  Do this. Do not bother with RST Engineering.  2 months after I had installed this antenna, I got a refund from Jim, with a note expressing his regrets at having not been able to complete my order in a timely fashion.  There are many more people who have reported similar experiences on the mailing list.

Anyway, the first thing I did was draw 2 lines 45 degrees to the centerline, locating the nav antenna more or less in the plans location. I then laid the proper lengths of copper tape on the lines, and drew a path for the coax that took it to the back side of the instrument panel, just off center. I routed out this line, so that the top of the coax would sit just flush with the foam, and so there was a recession for the torroids after they were shrink wrapped in place.  I then simply soldered the tape to the coax, one leg to the core wire, and one to the shielding.  I did a continuity test on each leg, saw that all was well, and microed everything in place.

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Step Indentation

In today’s post, I’ll cover the trials and tribulations of preparing the fuselage to accept the metal step that is called for in the plans.  A lot of people are moving away from the original step design and putting in retractable steps, but I’m not willing to go through the trouble for something that is aerodynamically insignificant, with the replacement potentially adding weight.  It’s mainly a cosmetic decision.

There are a couple of important things that you have to do to mount the step, and there are a couple points that the plans do not really make clear. The first issue is that the drawing for the wooden reinforcement comes directly from the long ez plans… or was it the cozy 3 plans? At any rate, the shape of the wooden insert is significantly different than shown.  The second issue is where the step actually fits.  You need to look ahead to chapter 8 to see where to mark the bolt line on the step that should be coincident with the longeron. Third, the plans do not mention the difference in curvature between the pre-manufactured step and the curvature of your fuselage.

First off, here’s what my cutout into the foam looked like.  A scary thing to go cutting into your recently shaped fuselage, for sure.

The cutout

As you can see, I simply scraped the foam away with a chisel.

At this point, I think I had been assuming that the step surface was flush with the longeron.  This is incorrect. The correct placement of the step and the issue with the step curvature I tackled at the same time. The first job was to make a wooden block to fit in the foam recess.  The foam is much shallower here than in the drawing, so even though I started with a 1/4″ piece of birch plywood, It got shaved pretty thin.  At the same time, I carved an indentation into it, so that I could have the curved section of the step recessed into the fuselage, so the upper surface would sit more or less flush.

Wooden insert

Insert in place

So at this point, having drawn the correct bolting line on the step, I gave it a little test fit:

Test fit

As you can see, I had carved away a bit much of the wood, based on my initial thoughts on where the step mounted. At this point, I carved away a bit of the longeron and the foam above the longeron so that the step would recess a bit:

recessed

At this point, I decided that I was going to simply fill in the gaps around the step with flox.  I wrapped the curved part of the step in packing tape, to act as a mold release, and put tape all around the perimeter to protect the surrounding foam.

Ready for Flox

I then floxed in the wooden block, filled the recess part was with flox, and smooshed the step down into it.  I wish I had taken a picture of this, but I clamped together a structure with a square up against the fuselage and the surface of the step, to ensure that it would be perpendicular to the sides. The following day I had no problems pulling the step right off.  More on the step to come when the blog catches up into chapter 8!

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