Aft fuselage tale cone

[Kevin_Conklin]

I have started working on the aft fuselage tail cone. I have the skins prepped with the lower longerons riveted to the skins, upper longerons clecoed, and the vertical channels all riveted in place.

I am questioning how to square the tail cone box. This is my plan:

1. Place the upper and lower #1 crossties, ensuring the 40" dimension measured from left skin to right skin at the bend break point. Clamp in place

2. Place the Y tail structure with the aft end of the structure flange even with the aft end of the left and right skin. Clamp in place. At that point it seems that I can still “swivel” the Y tail (forward or backward on either side), so I think I would just make sure that the ends of the left and right longerons are ‘even’ at the aft end.

3. Level the lower longerons (with a level resting on the inside top) near the forward end, and also near the aft end.

4. Level the upper longerons, again near the forward end, and also near the aft end.

5. Position and clamp all the other upper and lower crossties, bulkhead, shear web, etc.

I just am not sure how it all stays square until the bottom skin is in place, drilled into and clecoed to the lower longerons.

[Bryan_Cotton]

We had a square, level table and let that set the squareness of the tailcone.

Once you get that far, and it’s riveted, it has some stiffness. Next we flipped it over and drilled in the belly skin. When we did the turtledeck, the bottom skin was off and we had it on precision plastic sawhorses.

That’s one of my favorite build pictures.

[Kevin_Conklin]

I found Jeff Shultz’s build log, and that was very helpful.

[Bryan_Cotton]

For those who haven’t found it:

Jeff Shultz's Sonex #0604 Building Log

[JKS]

I approached it a little differently.

Step 1
Skins are predrilled by Sonex. Longerons match drilled & clecoed to side skins. Vertical channels match drilled & clecoed to side skins.

I have 2 tables, I picked them up cheap during covid. Stainless steel work tables for food service. 30” x 48”. One at the front and one at the tail. I leveled them and used a long piece of angle to make sure that they were level with each other. I am in total agreement with Bryan Cotton on the necessity of a good flat level worktable.

Step 2
I made a jig for the aft fuselage by placing a flat 1 x 12 with a couple of inches of overlap on the table a securing it to each table. The I took the bottom skin and drew a line along the edge of the skin on the boards. I then attached some angle (5 -6 inches each ) on that line.

The clecoed up side panels were clamped to the angles.

setup

side view of set up

leveling both tables to each other

The angle stock is used to support the bottom skin.

Adding the X-members.

Trueing the sides to vertical

Ensuring the X-members are square

To rivet, I removed the former, and riveted them together using a corner block to maintain the squareness.

I also made a large T-square to make sure the X-ties were perpendicular to the centerline.

Hope this helps.

[sonex1517]

One trick we used when trying to make sure things were level is to use a laser level and shoot it down a row of clecos. Obviously also used a level.

It touched the same spot on every cleco. A bit OCD but it worked.

(edited to add I know my two cents aren’t directly relevant to what Kevin asked)