aero-naut Canadair CL-415 Instrucciones de construcción - Página 3

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Canadair CL-415

Glued joints: selecting the correct adhesive can save a significant amount of weight. Use cyano-acrylate

glue ("cyano") wherever possible, either thin or thick as appropriate; the thin type penetrates into the wood

grain and stiffens it considerably. You can often simply hold balsa parts together and tack-glue them with

cyano. Increased humidity (e.g. breathing on the joint) accelerates the hardening process. In many

situations it is easier to apply the adhesive using a length of stick with a pointed end.

Caution: cyano-acrylate adhesives are injurious to health! Do not breathe in the fumes, and build the

model in a well-ventilated workshop. Read and observe the instructions on the glue packaging. We also

recommend epoxy laminating resin for this model. Compared to fast-setting epoxy glues, laminating resin

is easier to apply accurately, producing stronger, lighter joints. It penetrates into the smallest gaps and

ensures really sound joints.

For some work the resin should be thickened using a thixotropic additive; this prevents it running out of the

joint, and makes it easier to apply in exactly the right place. These and other resin additives can be

obtained from any good model shop.

Sanding: many of the model's components are made of GRP, but there is still plenty of wood which

requires sanding. A block of wood with new abrasive paper stuck to it is the basic requirement for building

this model successfully. The kit is supplied with two blocks (280 x 50 x 20 mm and 200 x 25 x 20 mm), but

please check that they are perfectly flat before using them.

If necessary, sand them flat by rubbing them on a sheet of abrasive paper. Apply abrasive paper to the

blocks using thin double-sided adhesive tape (e.g. carpet tape). We recommend that you apply medium-

grade paper (approx. 100 to 150-grit) to one face, and fine-grade paper (approx. 240-grit) to the other. Thin

balsa sheet parts (e.g. the two-part wing trailing edge) should be sanded to the correct taper by pressing

them down on the building board and sanding them back gradually, holding the block at an angle to the

grain direction. Solid parts and sub-assemblies can also be sanded free-hand. However, it is always best

to lay the part down on the board if possible, as this makes it easier to direct the sanding block accurately.

For larger areas, whether flat or curved, the sanding block can be used to "remove the high points", i.e.

any inaccuracies arising in the course of construction are smoothed out, producing a continuously curved

surface. The designer of this model can no longer imagine building models without a range of

commercially available reinforced plastic sanding plates, to which a variety of self-adhesive metal sanding

sheets can be applied. These can be purchased in any DIY store, and are highly recommended.

Advantages: a very sharp, long-lasting cutting tool, with no tendency to clog from sanding dust. Ideal for

quite hard wood, transitions between hard and soft materials (e.g. balsa - hardwood), and produces flat

results even with dissimilar materials.

Preparation: these building instructions include a reduced-scale drawing of all the die-cut balsa and

plywood sheets. Use a soft pencil to write the part numbers on the components, referring to this drawing.

Separate the parts from the die-cut sheets using a balsa knife. You may find it necessary to ease the

plywood parts out of their carrier sheet using a balsa knife or a fretsaw. All parts must be trial-fitted and

trimmed before being glued in place, as many are supplied slightly oversize to allow for final adjustment. A

flat building board is essential for constructing the model.

If you are an experienced builder, you may wish to deviate from the sequence described in these building

instructions, but please think ahead carefully before you do this!

Refer to the building instructions constantly, together with the stage photos and parts list, and check actual

dimensions of motors and gearboxes, servos, receiver, speed controller and your choice of flight battery as

you build the model. We hardly need to mention that micro-servos and a small receiver are a basic

necessity for a model of this type.

Whenever you are working on the model please keep the principle of weight saving in mind from the

outset. For example, the GRP parts are moulded using the minimum possible thickness of gelcoat resin,

but it is still possible to sand away some excess resin to save weight. However, the surface should remain

white overall, so take care not to sand through to the glass cloth. Don't round off edges and corners. We

recommend starting with 240-grit abrasive paper, used dry, and finishing with 400-grit paper.

Wings: the wing panels are assembled directly over the plan, which should be laid out on a completely flat

building board and protected with clear plastic film

The trailing edge panels (55) are supplied sanded to a taper at the extreme trailing edge; check the taper

and trim if necessary. Place one panel (55) accurately over the plan and pin it down. Position the bottom

leading edge sheet panel (61) in the same way (align the rear edge with the plan) and pin it down. Open

up the slots in the main and secondary spar for the outboard ribs (57) to 3 mm.

Position the main spar (53) exactly as shown on the plan - it should be offset slightly to the rear relative to

part (61) - and pin it in place. Place the secondary spar (54) in position, checking the correct spacing by

trial-fitting a few wing-ribs. Fit all the ribs and the secondary spar, check that everything is exactly at right-

angles, and pin the parts in place. Tack the ribs to the trailing edge (55) using individual drops of thin

cyano, and glue them to the secondary spar (54) in the same way. Glue the bottom leading edge sheeting