Petrel (oz14637)

About this Plan

Petrel. Free flight sport flyingboat model, for .20 - .25 diesel engines. Wingspan 26 in. All-sheet construction.

Direct submission to Outerzone.

Update 23/6/2023: Added article, thanks to RFJ.

Quote: "Build this pert little fvree flight semi-scale flying boat for small (.020) engines. Petrel, by John McStea.

The cover picture of Pilot magazine recently caught my eye, showing a French amphibian called the Petrel. I thought immediately of building a small version, but as a tractor rather than the original configuration of pusher, for CG considerations.

Construction is simple. Cut out the hull skin from 1/64 or 'mirror' ply (why is it called that?) and mark out the centre line, pylon slots, former positions and the holes for the lower wing fixing tubes.

Cut out the keel member and all formers from 1/8in. balsa and glue the keel into place on the hull centre line, blocking it up to a plumb 90 degrees. Add the 3/16 x 1/8 strips along the edges of the rear hull, F3 to F5, to provide a bed for attaching the skins for the after planes, and put to dry. Leave the similar pieces for the front plane until the hull has been formed.

Whilst these pieces are setting, cut out the five pieces for the pylon, a 1/8 sheet core, two laminates of 1/16 ply, and the outer skins of 1/16 sheet balsa. Note that the inner core is shorter than the other pieces which reach down to the keelson, since it buts only the upper edge of the keel piece. Assemble the pylon and place to dry under some pressure - a heavy book or two - being careful to keep the weight even, to avoid 'squeeze and slide'.

Glue the half formers into place on the keel, and when set, apply glue to the upper curves of the frames and carefully pull the ply skin down into position, holding the ply into place with lengths of drafting tape. When this is set, add the 3/16 x 1/8 pieces to the edges of the front plane between the formers from F1 to F3.

The carbon fibre tailboom tube is now pushed into position and epoxied in place. An alternative tube may be rolled from ply, the rolling made easier by soaking for a time in household ammonia. If the true cylinder is difficult, try forming around a waxed rod and bring the two edges of the ply to a Vee joint, using a shaped strip of balsa inside the vee to provide a glueing face, trimming F5 and the keel slot accordingly.

Now cut the two 1/8 in wide slots along the hull top to take the outer sides of the pylon and insert the pylon, before glueing, shape the bottom edge and the keel to suit the curvature of the vee of the planes, to make a good bed for the bottom skins. Add the 1/64 ply skins to the front planes from Fl to F3 and the 1/16in. balsa skins to the rear planes, F3 to F5. Fill out the vee to the step at F3 with 3/16 balsa, and sand to the shape of the ply skin..."

Supplementary file notes

Article.

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