Druid (oz2992)

About this Plan

Druid. Free flight towline glider contest model.

Quote: "One full size free flight plan and it’s Druid by Canadian Jim Moseley. Druid is a good flying A/1 glider the result of quite a bit of development work. Jim said the result is an easy to build and easy to fly model that can hold it’s own with any of the classes."

Update 27/8/2024: Added article, thanks to Shawn.

Quote: "Druid. Jim Mosley from Ontario based this model on a design first published in 1969.

Druid owes its name to the fact it is based on an unnamed A/1 design by Elton Drew published in the July 1967 Northern Area News. The new ID of this Drew design is thus in recognition of its origins ie Drew-ID = Druid.

Two replicas of Elton's design were built and proved to be excellent gliders though ultimately suffering wing failure under tow. A completely new one piece wing was then built, of slightly higher aspect ratio and incorporating the airfoil from a Wichita 8 A/2 which was flying well for me at the time. This revised A/I proved to be an immediate success with better performance coupled with exceptional towline stability. The design has since remained proportionally unchanged over the years other than a small increase of fin area; indeed one of the original 1967 fuselages is still in use though sadly faded and somewhat worn.

Minor structural changes have been made in that external ply doublers have been added to the fuselage nose to prevent breakage at the timer aperture, which are not unsightly when chamfered to blend to the fuselage side and perhaps incorporated as part of the colour scheme as indicated in a photograph. Stabiliser spars have been repositioned to reduce upward bowing of this unit. In recent versions the lower centre panel spar has been reduced from 3/16 square spruce to 1/8 x 3/16 as some airfoil distortion at the spar location was noticed when wings were several years old (though no difference in performance or handling was noted) and this appears to be adequately strong. The next version will have carbon fibre added to this spar to further increase the bending strength of the wing.

The outcome is an attractive easy-to-build and easy-to-fly A/1, well within the ability of a relative beginner and which can hold its own with any of its class.

Wing: I prefer to start any new model by building and fully finishing the flying surfaces to give them time to begin ageing whilst the rest of the structure is assembled. An accurate plywood rib template is essential and should be identified and stored for future use. (I'm still using a 24-yr-old template). Prepare the requisite number of ribs from medium-grade 1/16 balsa using the template. Spar slots may be incorporated but I prefer to slot spars into the structure once the ribs are cemented into the LE and TE structure. The trailing edge is carved from a 9/16 wide strip from firm 1/8 stock. I find it better to first cut a 1 in strip from which I then re-cut the 9/16 TE with a good metal straightedge as guide. If the TE is cut directly from the sheet I find that stress relief in the wood can result in a strip that is far from straight.

The front edge of the TE should be packed up with scraps of 1/16 to conform to the undercamber, and the rear edge of the LE similarly packed with 1/32. Cement all centre section ribs into place except those at the dihedral joint, and add 1/16 gussets to the TE. A chore, but they add immeasurably to the eventual strength and warp resistance of the wing.

Dihedral joint ribs are installed with the aid of the template, the top of the rib thus sloping towards the centre. Two upper spars of 1/8 sq spruce may now be slotted, or dropped, into place depending upon how you chose to cut your rib template. If slotting in, a metal straightedge and a new razorblade are required, with due care not to cut deeper than necessary and thus weaken the rib. When all is thoroughly dry remove the panel from the board, invert it and carefully add the lower spruce spar. Balsa cement is not recommended for these spruce/ balsa joints, a slower drying PVA being far more preferable. The LE may be carved to section and the spar ends carefully trimmed to conform to the slanted end ribs.

Tip panels are built similarly though slightly lighter stock may be used for ribs and LE/TE than in the centre panel. After pinning down the LE and TE with appropriate packing, laminate the tips into place. This may be done around a wall of pins or against a foam or cardboard inner former. There is no need to soak strips of 1/32 as PVA - or balsa cement if you work quickly - softens them sufficiently. A set can be put together and then carefully eased around the form until they can be secured to the LE and TE and left to dry out thoroughly. During this time ribs may be added with the end ribs slanted as before..."

Supplementary file notes

Article.

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