Mini Helides (oz2921)

About this Plan

Mini Helides. Mini version at 26in span of the original 40in 1950 Helides, this one for CO2 power.

Quote: "Mini Helides. A CO2 mini-version by John Russell of RA Grasmeders 1950 original.

Construction: Wood used should be of medium to soft grade. Make every effort to keep the rear end as light as possible, The tailplane has to he a compromise, as it is of rather high aspect ratio and prone to warps if really soft wood is used. Balsa cement was used for construction of the original, except where otherwise stated.

Fuselage: Build two sides over the plan in the usual manner, noting 1/l6in components to be used towards the rear_ Incorporate front sheet parts at this stage.

To avoid any slight distortion caused by the upper longeron pulling the lower one into a slight curve on removal from the plan, it is worth splitting the top longeron into two laminations over the front two thirds of its length and Blueing together. Pin down over the plan while still wet and the curve will be permanently set. This is not very easy unless a balsa stripper is used and is a good idea but not essential. Diagonal braces would be another solution to this.

Pin and glue the sides together at the tail post and before glue sets, insert the main former. Wait a couple of minutes, then pull sides together at front, and fit the front bulk-head and pylon former. Fit pylon centre piece and semi-circular formers, then wrap round soft 1 /32 sheet to form the pylon front. Sand the bottom edge of this to match the pylon core, fit cross former, then soft 1/32 balsa curved into the fuselage side sheets, Dampen the 1/32 sheet if neces-sary, or use several pieces if reluctant to bend!

Fit the remainder of the cross pieces and gussets. Epoxy the undercarriage to former. then fit bottom sheet and ply mount for charging nozzle. Mount the motor onto the ply mount, make recesses in 1/4in sheet backing for nuts and bolts and epoxy together. A little grease on the bolts will prevent them being epoxied in. Remove the motor and glue the mount to the front bulk-head, then add side cheeks.

Finally sand the fuselage smooth. Dowels, dethermaliser guides and main wing mount may be fitted after covering.

Wing: Laminate the tips around a balsa former and shape the trailing edge from 1/8 x 3/8 straight grained balsa. Build the wing flat on the building board, propping up the front of the trailing edge 1/32 to suit the undercamber of the ribs. Omit the spar and 1/16 ribs at the dihedral breaks at this stage. Cut 'V' notches at the dihedral breaks, prop up to correct angle and glue with PVA. When set, fit the remaining ribs, then the top spar (using PVA again).

Make the spar joints a good fit as no ply braces should be necessary in a model of this size and weight.

Fill in beneath the spar in centre bays with scrap spar stock flush with the bottom of the ribs to provide a firm area to suit the wing rest. The wing rest, can be made at this stage to fit wing, then glued between the fuselage sides.

Tail unit: Build the tailplane over the plan using ribs cut to approximate shape from 1/32 sheet. Sand these to final shape when cement has set, using fine sandpaper on a long block (NOW stick back the ribs you ha ve just knocked out!).

Fin and end plates are made from the lightest 1/16 sheet you can find, sand to help reduce weight (to about 1/20 in).

Sand base of fin to a good fit on the centre rib. The end plates are best fitted to the tail-plane after covering the bottom surface but before covering the top. The top covering can then be extended over the top edges of the end plates.

Covering: Cover with lightweight Jap tissue, steam to shrink and give one coat of dope, about 50/50 dope and thinners on fuselage and slightly thinner on wing and tailplane (about 40/60 dope/thinners). Pin down while the dope dries, the tail-plane can be pinned down across short lengths of thin sq balsa, The inner right wing panel should he given slight wash-in at this stage - about 3/32 under the leading edge should suffice.

Trimming: Cut across the fin for about 1/2 in near the base to form a trim tab, this can be simply bent for turn, then fixed by running a bead of cement along the base to fix when the correct setting is established.

Add weight if necessary behind the front bulkhead, until the model glides just off the stall. Bend trim tab to the right to obtain circling glide. On a gas charge, the model should now climb gently in right hand circles, the wash-in preventing a spiral dive.

My model flew with very little trimming apart from slight reduction in wing inci-dence as noted on plan, if any incidence adjustment is necessary, this is easily done by packing up, or cutting away the rear wing supports.

If your model is reluctant to turn right, try a left turn - I once spent a whole afternoon trying to trim a 'Scram' to fly left because the instructions said to do so. In the end I tried a right turn and that model has flown perfectly ever since, in right hand circles. If 'Helides' is flown left then the wash-in should be reversed, although if reluctant to turn right - your warps have probably changed anyway! "

Supplementary file notes

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