Finally I got it Right(-angled), Mar. 19th, 2001

After lots of measuring, pushing, pulling and head-scratching I found the right way how to align the fuse tailcone.

If you want to get the inside of this frame right-angled (and you should to)...

(outside dimension is 1017.6mm, not 1016mm as the plans show)

... and if you want the sidewalls also at a right angle to the horizontal...

... then you have to lift up the tail (no chuckling please). Top of the box is horizontally levelled. This is the reason my fixture shown further down did not work properly!

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How Strong are these 'Pop' Rivets actually? Mar. 13th, 2001

I just purchased two packs of stainless steel blind rivets from a German manufacturer. Before ordering I asked for a specification. They were very cooperative and faxed the spec right away. The spec shows shear & tensile strenght a bit higher than the Avdel Textron 'N' Rivets (606lb shear/764lb tensile), which are usually used for the Sonex design. 'My' rivets are made according to DIN 7337, head is made of 1.4301, mandrel of 1.4541, the manufacturer is qualified according to ISO 9001. The rivets are 1/8" (3.2mm) and the grip range is from 1 mm to 3 mm.

But THE BIG QUESTION is how strong are these rivets really?

To get an answer I made a test tool using two scrap (aargh) horizontal fuselage stiffeners. The thing I constructed like shears, where the pivot point is made up by an M8 steel bolt. 15 mm from the steel bolt I set a 1/8" rivet. The 'handle-bars' were made from 0.032" and 0.025" 'U' profiles. They are about 400 mm long, thus giving a force translation factor of about 1 : 27.

Without much effort I pulled the handles apart. The rivet was pulled through the aluminium (more through the 0.025" profile, less at the 0.032"), but the rivet didn't shear off.

What have we learned from this? This rivets will hold, even when the construction already has separated ;)))

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Fixtures, Mar. 10th, 2001

Before clecoing the aft fuselage cross ties, the tailcone has to be aligned properly. I used the following procedure:

at first I drew a centerline on the large worktable, then I marked the outside shape of the aft fuse.

then I aligned the sidewalls exactly with these outside markings

then I clamped (using C-clamps) the crossties in between to give the thing some stability

a first check with the carpenter's angle revealed not a single right angle!

so I decided to build a very simple fixture which will hold the sidewalls exactly vertical. The scrap-box at the hobby market's wood section contained lots of rectangular pieces. They cut very exact, so this is what I need

Watch the three particle boards (1) at each side. Additionally at some interval I nailed small wooden sticks right and left of the longerons (2). This will prevent the longerons to move laterally.

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Tail Cone Test-Fit, March 6th, 2001

This is the first time I have put losts of these small (and not so small) parts together to a big shiny something.

This thing is NOT so crooked as it looks - just the camera's perspective - HOWEVER if you hear soneone talking about -easy build - jigless construction - just a flat table required - DISTRUST it. It's only the usual sales talk. If I would rivet the pieces together as is, then you wouldn't find a single right angle afterwards. Next task is to build wooden triangles which will hold the sides properly aligned.

Another view. I have worked now about 600 hours and 8 months for this project (and according to my schedule there are at least 1400 more hours to come until this thing will lift off...)

Next tasks are:

• build fixture, exactly adjust and clamp all the parts
• drill to final size
• dimple all rivet locations which are visible from outside and where sheet metal meets sheet metal. Here I'll install flush solid rivets *1. All locations where sheet metal is attached to 'L' extrusions (longerons) I will install conventional/round head solid rivets *1 in order to avoid countersinking/weakening the highly stressed extrusions
• disassemble the whole thing, deburr, clean and prime inside surfaces *1
• rivet together

remark: *1: this are some of my own deviations from the original Sonex design

I have allowed at least two months for this. The timing is fine, because I'll prime-spray the parts outside and temperature will (hopefully) then be high enough (in late April).

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Preliminary Electrical Wiring Diagram, Mar. 1st, 2001

download wiring diagran as JPG picture

download in Corel Draw 8 format

some objectives in planning my aircraft wiring scheme:

• The electrical system is structured. It hould be possible to isolate any of the sub-networks by either switching or pulling resettable circuit breakers
• Short circuits should be confined to an as small as possible sub-network
• (electronic-)engine ignition is the most vital part and should be extra fail-safe
• the on-board voltage should be over-voltage protected

some about material acquisition:

• 'Strategic' switches (contacts) and circuit breakers should be of highest quality *1
• wire termination is wherever possible by either crimped Fast-On (AMP) or ring screw terminals, soldering should be avoided
• fuse holders should have high clamping force
• any termination should be serviceable (accessibility to rear of instrument panel)

*1: quality switches come with a spec sheet (on/off resistance, No. of cycles, material of contacts), cheap ones don't. Don't use the listed AC amperage! DC is always LOWER.

Looks as if Leburg will become the ignition of choice for my Type 4

Suggestions always welcome.