Assembly Holding Fixture

[Gearup]

Building a number of similar models has inspired me to improve on my improvised fixtures to help move the projects along. I knew that I could stabilize the model by holding it down with my finger on top of the fuselage and pushing it against the bench. Problem is, I am making high wing and low wing aircraft with varied degrees of dihedral and I need more fingers...
A wooden hand screw style clamp is capable of adjusting to accommodate large or odd shapes with precision force. However, mine are a bit too big for that on models.
So I made a simple fixture from a piece of  aluminium "T" slot, wood scraps and bolts.  It is essentially a small precision screw clamp with a long lower jaw that incorporates a work base. The "T" slot allows the 3rd class lever arrangement to be used as an adjustable "finger" to hold the fuselage in position while the wings are installed.  Again, the wing roots are installed with small brass pins and need to be glued to the fuselage, hence the need for holding the model securely while setting up the wings.
Materials:

Holding fixture
Aluminium "T" track - 12" long or as needed- Amazon, woodworker tool suppliers
Finger - 3/4" x 6" x 1/8" wood stick
Machine bolts - 2-1/2" 1/4-20 (2 ea)
Hex nut - 1/4-20 (3 ea)
Wing nut - 1/4-20
Foam pad - 1" square 1/8" thick (crafting material)

Work base
Base - 3"x 8" 3/8" plywood (or solid wood). Can be sized to fit larger models if required.
Key - 5/16" square x 3" stick to fit slot width of "T" slot

Dihedral blocks
Wooden blocks - 3/4" material sized to fit model dihedral height

Finger assembly
Drill two 5/16" holes in the finger with the first (pivot bolt) 1/2" from the end and the second (clamp bolt) spaced 1-1/2" apart. Glue or double-side tape the small foam pad onto the finger at the opposite end.

On the clamp bolt, thread the wing-nut, inverted, onto the bolt stopping about 2" from the end. With the pad facing down, drop the clamp bolt through the clamp bolt hole.  Thread a hex nut onto the end of the clamp bolt, about two turns, so the bolt does not extend past the face of the nut.

Drop the pivot bolt through the pivot bolt hole and thread a hex nut onto the bolt about 2" from the end. Thread another hex nut onto the pivot bolt, about two turns as with the clamp bolt.

Work Base
To assist in aligning the model on the base, draw parallel lines spaced about 1/4" apart along the length of the base. Draw a center line top and bottom across the base. Glue the 5/16" key on the bottom of the base at the center line.

Usage
Set the base on the track with the key in the "T" track slot.
Slide the finger assembly onto the "T" with the hex nuts in the slot and the foam pad positioned over the base. Lightly tighten the two bolts to hold them in position on the "T". Don't over tighten: just enough to keep them from sliding in the track.
Determine where the dihedral blocks should be under the wing from your drawing to get the correct wing angle and mark lines on the base for reference.
Place the fuselage on the centreline of the base and adjust the pivot height with the hex nut to make the finger parallel with the "T" track when the pad is touching the fuselage top.  Adjust the clamp bolt higher as required to allow the finger to become parallel. Once you are satisfied with the positioning of the fuselage and finger, tighten the clamp-bolt wing-nut down on the finger to secure the fuselage.

Set the dihedral blocks in place at the reference lines and secure them with double sided tape.

The fixture is now set to allow you to work on the model without it shifting around. Install wings, stabilizers or flip the model over and work on the landing gear, struts etc. Just make sure you are clamping the fuselage down and not loading a wing or empennage. Use a spacer under the fuselage to get clearance as needed.

Regards,
Fraser