Main Spar; Wing Ribs - Model Shipways MA1040 Instruction Manual

Fokker dr.1 tri-plane

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Main spar

The main spar on the Dr.1 is essentially a box-beam. The top and bottom members have slots

facing forward to receive the forward half of the ribs. The difference between the top (WW1a)

and bottom (WW1b) is that the slot for the root rib is canted out at the bottom to clear the

landing gear, thus the slot in the bottom is further outboard. To build this spar cut .40 inch

(10mm) long spacers from 1/32 x 1/4 inch (.8 x 6 mm) and glue at three positions along spar

bottom (Two shown in Figure 1.2). Their exact locations are not critical as they only act to

provide guides to keep the front and rear square to the bottom while gluing them in place, but

keep the inboard spacer outboard of the first rib as shown to the left in the figure. Before gluing

ensure that the ribs fit in the slots and lightly sand the slots as needed.

Glue the spar front (WW2) and rear (WW3) to the bottom making sure the slots are aligned (See

Figure 1.2). The rear spar notches are offset for the root rib so it is canted out at the bottom to

clear the landing gear strut. Glue on the top. Mark inside the spar to note the root relative to

the tip. Check that the ribs fit in the slots and that the root rib is canted outward at the bottom.

Figure 1.2 Bottom Wing Spar Details

There are eight ribs (WW4) on

each side of the bottom wing,

not counting the tip rib (WW5).

Each rib (except the root rib) has

stiffeners on both sides as

shown in Figure 1.3. These are

cut from the 1/16 x1/64 inch (1.6

x .4 mm) strips. On the root rib

only put stiffeners on the

outboard side.

The easy way to add the stiffeners is before the ribs

are removed from the sheet as show in the

photograph, Figure 1.4. Glue strips of stiffener to

both sides of the ribs and then cut on the laser cut

lines, on both sides, to free the ribs from the Sheet.

Then clean off the carbon residue and sand the

stiffeners to match the rib out line as needed.

Figure 1.3 Wing Rib Details

Figure 1.4 Rib Stiffener Details

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