Indoor HL Glider (oz13656)

About this Plan

Indoor HL Glider. Simple indoor chuck glider design.

Quote: "Indoor Hand Launch Gliders. Hugh O'Donnell discusses the design, construction and flying of 'chuck' gliders and the refinements that give a 'contest' performance.

Hand launch gliders give a vast return in enjoyment for the small amount of time and money involved in their construction; but in this country, due to the restricted venues for indoor meetings, interest in this field has hitherto been small. However, Cardington is once again available, and this article has been prepared to give a general outline of the techniques involved to those modellers who wish to fly there. This last sentence does not mean that only modellers with similar facilities to Cardington will find these notes of interest, as much of the material is applicable to outdoor as well as indoor chuckgliders.

The basic requirements are a good model and sound launching and trimming techniques, so let us discuss these in detail.

The Model: With this there are three essentials - design, quality of wood and workmanship.

Design: First of all, we must adjust the glider's size and weight to suit the thrower's arm and the available flying space. At Cardington, where space is no problem, we design for maximum duration regardless of model restrictions. In smaller halls, such as the Corn Exchange, Manchester, we must reduce both size and weight in order to circle within the space available and considera tions such as increased airfoil thickness and undercamber are important here.

For Cardington, a guide to the size of model for a person. of about average strength is given by the accompanying full size plan of my own design. Weight is more critical than size - heavier models being best suited to stronger arms, and it would seem that the 'tolerance' range for indoor models is from 0.6 to 0.9 oz.

The actual layout of the model is more or less standardised. Once a model has been designed which performs to our requirements, then it is doubtful whether further refinements in the layout are worthwhile. having developed a sound design any substantial increase in duration is achieved only by improving the throw, obtaining a better finish, varying the weight, adding turbulators, etc.

Quality of wood: Due to the enormous stress which an HL glider must withstand both in flying and on impact, sound workmanship and best quality wood are essential. Since the outlay is small it is well worth while to select the best timber regardless of cost, and for this reason I prefer to use American 'Indoor Balsa' for all flying surfaces. The wings should be made from light, even textured stock having a short or quarter-grain. Light, quarter-grained 1/32 or 1/16 sheet should be used for tails and fins. Hard 'English' balsa is suitable for the fuselage and should be chosen with a long straight grain. When finished, the fuselage should have an even flexure between wing and tail to reduce the risk of breakage on impact.

Workmanship: Not only does the model have to be built accurately, but joints must be carefully prepared and cemented firmly, while correct alignment is imperative. It is a mistake to attempt to finish a model in an evening; I prefer to allow a week for the construction of two models simultaneously.

Having decided upon a suitable design, the model is best constructed in the following manner. Make card templates for the wing, tail and fin outlines. Starting with the wing, cut the planforrn accurately, mark the dihedral joints and cement the leading edge reinforcement in place securing with Sellotape. Tail surfaces are now made, and using a sanding block the sections are formed. Finish with 600 grade wet-or-dry paper.

The fuselage should be marked out and the outline cut carefully. Ensure that correct zero-zero incidences have been obtained, and that the recesses for the wing, tail and fin are suitable. Round off the appropriate corners and alter sanding with progressively finer papers, finish with 600 grade, and pre-cement the fin and tail surfaces in place. Make sure that these are correctly aligned with the fuselage before allowing to dry overnight.

When the LE reinforcement has dried, the wing section should be formed. If the wing plartform is elliptical, the wing should be tapered spanwise and roughly sanded before the section is carved. Use a sharp knife to form the section roughly, finish off with a razor blade and sanding block. It is a bad policy to make the TE too thin; aim Ibr a thickness of about 1/32 in at the centre, gradually becoming 'knife-edged' towards the tips. Having achieved an accurate section at this stage, finish off with progressively finer sandpapers, down to 600 grade. It is a good plan to place several layers of newspaper on the work bench to avoid small scratches and dents.

The wing is now cut along the dihedral breaks, and the tip joints formed and pre-cemented. When these are dry, the centre joint is made, and allowed to dry. Cement fillets are applied to all dihedral joints, both top and bottom. Give the centre joint an additional fillet..."

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