Chapter 6 – Shaping Fuselage Bottom

Today, making a mess was the name of the game.  Definitely had to wear a mask to keep from ingesting pounds of fine blue foam!  I used a plunge router to start, then moved into using an orbital sander and some perm-a-grit hand carving tools.  Obviously there’s no effort in cutting foam, (with a power tool, it takes a little effort by hand!) but since the resistance is low then I had to be careful when close to the lines.

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 The process continues: Removing lots of foam, creating a gross outline of the individual areas, transitioning and then smoothing it all out.  I started from the rear half and moved forward.

Fuselage Bottom - Rear Seat Area

Shaping Fuselage Bottom

I started this step mid-morning, and tried to stay in the shade not just because of keeping the sun off the foam, but because it was pretty darn hot as well.  I worked well into the late afternoon and slowly nugged my way through this beast!

 

Chapter 6 – Fuselage Bottom

The fuselage bottom is made up two pieces of 1-3/4″ thick Divinycell foam micro’d together, then shaped into a boat, or football, shape.  Although my fuselage is shaped a little differently than the plan’s shape, it really doesn’t matter with the steps used to figure out the outline of the fuselage bottom.

Chapter 6 - Fuselage Bottom Mark-Up

The fuselage assembly is simply turned upside down and the fuselage bottom is placed on the bottom (which is now the top) of the fuselage and positioned equidistant from each side and abutted to the front bulkhead F22.

Chapter 6 - Fuselage Bottom Mark-Up

Once the fuselage bottom is in place, it’s weighed down to conform to the shape of the fuselage bottom.

Chapter 6 - Fuselage Bottom Mark-Up Detail

Then I climbed up underneath there with a Sharpie and marked the outlines of each compartment.  Then the weights came off and I followed the dimensions spelled out in the plans to create the marked up areas that will be formed into its final shape.

With the mark-ups complete, now it’s time to actually cut out the outside shape of the fuselage bottom.  Once I got the outside shape cut, I took it outside to start getting all that foam out of the marked-upped areas.

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There are specific depths for each area, and obviously all the transitions need to flow together smoothly.  The process definitely takes a bit of time, and it does get fairly messy with all that blue foam!

Firewall & Fuselage Width Update

Aside

I had ordered my Carbon Fiber cowlings from Feather Lite, but with a twist: Mike & Larry were going to put a joggle down the center of top and bottom of the cowling so that I could adjust the cowling widths to my new wider fuselage.  Unfortunately, as they played around with the original plugs and molds— [these were the exact same molds that Mike Melvill designed for his armpit scoop cooling design that he installed before his round-the-world trip with Dick Rutan] —they realized that it was just too problematic and difficult to put the joggles down the center of the cowling halves.  Plus, it would add significantly more weight, minimizing the benefits and increasing the cost, thus nearly negating the reasons for using CF on the cowlings to begin with.

Thus, I would have to go with the original cowling size, meaning I had to trim my firewall down to it’s original plan-sized dimension.  Of course, the firewall being back to its original size does nothing for me if I can’t mount it to my top & bottom longerons… which was the case since my rear seat was widened by 1.2 inches.  So I recalculated everything, and not wanting to have go after my front seat (read: cut)  I compromised (the art of engineering, eh?) and narrowed my existing modified rear seat back by 0.4″ to only 0.8″ over stock. Which still is a decent amount of extra room in this narrow of a fuselage.

The one effect it did have was that it accentuated the curve of my cockpit to make it even more football shaped (fatter at the center, and narrower at the ends).  I’m not an aerodynamicist, but I have had some folks say that my shape is less desirable and less efficient than the original design.  Regardless, I think it will still fly even with a potential small increased drag penalty.

Back to Chapter 4 – Instrument Panel

Ok, obviously by just the fact that I’m building an “experimental” airplane hints that I like to experiment, at least a bit.  I thought quite a lot on how I wanted my instrument panel to look.  I wasn’t sure exactly at first, but then finally I figured I would make the top layer Carbon Fiber on the front face of the panel to A) Add stiffness and B) Add coolness.  I ordered some CF in my last Aircraft Spruce order and after it came in, I assessed it one last time and decided to pull the trigger!

Carbon Fiber Instrument Panel

Back to Chapter 4 – Firewall

After another few discussions with some experienced Canardians familiar with the old glory days of the Cafe Races, I decided on another modification.  Now I’m sure this  may very well elicit some groans and ha-rumphs, and maybe even a few mutterings of how crazy I am, to put it politely.  I decided I was going pulley-less and running my rudder cables from Point-A (rudder pedals) through a curved conduit that traverses through the centersection spar, makes a semi-shallow bend and heads to Point B (rudders).  No fiberglass strands will be hurt in the making of this modification, just merely slightly separated at the holes in the foam so that glass strength and integrity is still in tact on the centersection spar.  So, no pulleys means that I don’t require the pulley brackets, and thus no “ears” on the firewall.

Modified Firewall

Glassing Firewall & Instrument Panel

Once I finished cutting the ears off the firewall, I could get to glassing it (and laying up CF on the instrument panel).

 

 

 

Switching Epoxies

After a couple of discussions with a few members of the “Old Canard Guard,” including one of my building mentors, Dale Martin, I decided to pull the trigger and switch from MGS 335 to MGS 285.  While the epoxy itself isn’t that much more expensive, the slow hardener incurs a hazardous shipping penalty usually on the order of $45 per quart.  Yes, that’s on top of the cost of the hardener and the normal shipping fee!

MGS 285 hardener

So why did I switch?  Well, primarily safety.  After reviewing Gary Hunter’s Do’s & Don’ts of Epoxy Resin, I decided I should go after an epoxy that gives me the highest Tg.  I was already using the MGS system, so I was familiar with the system.  Plus, I’m moving to Germany in late July for a couple of years, so after a bit of research I’m fairly certain I can buy the MGS where it’s actually made and pick it up in bulk quantity ala Sam’s Club style.

Also, for the remainder of my build tasks here, I was also able to find a company in California to sell me two quarts of the fast hardener for  the $45 hazardous shipping fee.