PZL P.38 Wolf (oz14939)

About this Plan

PZL P.38 Wolf. Radio control sport-scale model of the Polish prototype twin heavy fighter. Wingspan 66 in, for 2x .48 four-stroke engines.

Quote: "Sport-scale version of a little-known Polish fighter bomber. PZL P.38 Wolf, by Roy Day.

I FIRST SAW a picture of the PZL-P38 Wolf fighter bomber in an old 1959 issue of Air Progress magazine, It was developed by Poland between 1938 and 39. Only two prototypes were built: one was flown, and both were destroyed during the German invasion of Poland in September 1939. I liked the lines of the P38 and thought it would make an interesting twin. A little later during the project, I struck up a correspondence with Polish modeler Piotr Zawada, who furnished me with a 3-view and some photos of the PZL-P38. The aircraft probably would have been good as a ground-attack fighter, but it could only carry a couple of small bombs under its wings. It has some interesting lines and is certainly not frequently modelled, if ever.

WING: For a conventional twin such as the PZL-P38, the most complicated part is the wing, which has the engines, nacelles, landing gear and fuel-system plumbing in addition to the usual servos and control linkages. The airfoil is flat from the trailing edge (TE) to the forward bottom spar, so you can build the wing flat on your board.

Make the forward spar by laminating two 1/8 x 1/4-inch spruce or basswood pieces as shown on the plan. Make the spar caps long enough to extend onto the wingtips for added strength. Lay your ribs on the plan, and mark the hole locations for the aileron control cables and throttle cables and the pressure and fuel lines for the engines. Don't trap yourself by installing the wing sheeting without first installing these Iines and cables.

Lay down the 1/16-inch TE sheeting and both lower spar caps. Jig up the TE at the tip rib, R-9, 1/4 inch to give about 2 degrees of washout. Glue in all ribs except the center rib. Put into place but don't glue it until later, when you are ready to join the wing halves. This is necessary because you are building on the tapered bottom of the wing, and when you assemble the wing upside-down on a flat surface (no dihedral), you want those center ribs to fit together perfectly. Now add the top spar caps, one of the leading-edge (LE) laminations, aileron hinge blocks and horn plate and the shear webs. Now you can glue on the TE sheeting.

Remove the panel from your board, and build the other panel to this same stage. Join the wing panels upside-down on a flat surface. Pull both center ribs together to make a good joint, and glue them to their respective wing panels. Chances are, if you had glued them in earlier, they would not fit exactly.

Glue the carbon-fiber strip on the bottom of the forward spar cap. Now glue in the bottom LE sheeting, and turn the joined wing over to the upright position. Add the carbon-fiber reinforcement to the top of the main spar. With your lines and control cables in place, you can now put on the top LE sheeting in one continuous piece across the center joint to make the wing stronger. Fill in the remaining sheeting as shown on the plan, and add the rib caps. Add carbon strips on top of the sheeting at the LE and TE as shown on the plan. Cut out the ailerons and face the openings with 1/16 sheet. Add 2-ounce fiberglass cloth and resin out past the nacelles as indicated on the plan. Glue on the wingtips and the remaining laminations for the LE, and sand to shape. Set the completed wing aside.

You may be wondering if I've forgotten the dihedral braces; there are none, as they are not needed. For this thick wing, at the root, the needed strength comes from the continuous skin, plus the fiberglass cloth, plus the carbon-fiber reinforcements. I can vouch for its strength because a nasty crash broke only the wingtip. You don't need dihedral braces on this wing..."

Direct submission to Outerzone.

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