Ballerina PET

[Peter Miller]

The Mysteryship colours are nice.

I do find that with dark colours a couple of big white marks under the wings help to tell me which way up it is. Better than big black patches on a light coloured model

[Clive Hall]

100% with you there, Peter; I have been doing that since I saw something similar on a full size extra more than 10 years ago. Also use colours not present on the topside, so on a Mystery Ship scheme I would use dark blue with a yellow patch under the wing

[Clive Hall]

I heard rumours that the bureaucrats in Brussels had forbidden the sale of contact glues containing solvents: not true, today I bought a new tube of my favourite.

The wing skins are on at last; here is the rest of the detail for the method.

The wing sits on cradles that can be pinned to the bench. It helps to use masking tape to hold the ribs down on the cradles. Note two extra small cradles have been placed under the leading edge to keep it straight.

I apply the contact glue by putting drops from the tube at about 20 mm intervals and then spreading them quickly with a finger-tip. This spreads the glue at the right thickness. Just make it go as far as it will freely then add some more drops for the next bit. Apply it to all the frame edges and all the marked areas on the sheet that make contact, then return the frame to the cradles and glue two cocktail sticks into place in the holes in the spar.

Place pieces of newspaper over most of the glued frame to protect it from premature contact, leaving about 1 cm gap between the edge of the paper and the spar. If it is too close to the spar it can be difficult to pull away later. Lower the skin gently on to the cocktail sticks. This will ensure exact placement of the skin, so press it down evenly along the spar. All it takes is gentle pressure. Once the two surfaces meet the joint is made. It can be pressed more firmly later - it will not move after the first contact.

Next withdraw the paper and use the edge of a piece of wood to press the skin on to the ribs working progressively from the spar to the leading edge. A piece of 1/2 inch balsa sheet will do for this. Finally make sure the leading edge has made contact along all of its length by running a finger and thumb gently along it to make sure it is squeezed together..

That does it. The skin is now firmly and accurately in place, but the wing will still have some slight ability to twist until the other skin is attached. Cut off the cocktail sticks close to the surface and sand them to the level of the newly applied skin. Any internal wing installations can be done now, before the second skin is applied.

The panel is next turned over and settled in the cradles for the other surface. This is the critical stage where the cradles are most important, as the attachment of the second skin removes any twisting flexibility in the panel and finally sets the incidence along the panel. For this reason I usually apply the lower skins first as they have less curvature. The cradles can be designed to include washout if it is required. Use the same skin attachment method again as was used for the first skin, making absolutely certain that the panel is firmly settled in the cradles and that the cradles are standing on a flat surface.

Then repeat the process for the other panel.

That’s it. It works for any kind of wing, parallel, tapered, delta, and to some degree even for elliptical. A useful tip is to sand the outer surface of the wing skin before doing anything else.

[Clive Hall]

Ailerons and centre section sheeting are now fitted, but no more posts for a while. The build has hit the buffers – problem with left hand, the doc says no more modelling for at least a week; can’t even play with the simulator.

[Peter Miller]

That isreally rough luck

[Clive Hall]

Ballerina PET is back in action. The dodgy wrist has recovered enough for careful use, so I have completed the wing centre section sheeting and now I have begun to make the wing tips. I like to use laminations but regard balsa as a bit flimsy, so I use obechi veneer as used for skins on foam wings. I cut strips about 8mm wide then laminate them in groups of 7 in a temporary jig made of pins.

I knock the pins into the printed outline of the part, prepare the strips by damping them in water, glue them together with white glue, and then hold them in place with another inner row of pins. It helps to reduce the glue drying time if the lamination is left a few minutes to allow the glue to grab, and then lifted a small distance clear of the bench. When dry a hard solid component lifts out and is replaced by another batch of glued strips. Once finished the pins go back in the pin box. The next set of laminations will be the tail group outlines, made the same way.

[Peter Miller]

Looks good.

When I laminate tips I do use balsa. 1/16" X 1/4 strips but I insert one lamination of 1/64" ply on larger models.

[Clive Hall]

The ailerons are now ready to fir, and the cap-strips are on the ribs. Impact glue is ideal for this as it removes the need to use pins, so no split wood, and no danger of a strip lifting once it is in place. Just the thinnest smear of adhesive is enough on the rib edge and the inner face of the cap strip. Leave about 3 minutes to dry, then put in position, and the strip is fully fixed.