Big Impala (oz6586)
About this Plan
Veron Big Impala. Radio control slope soarer.
Quote: "The BIG IMPALA at 74in (1880 mm) span has been introduced as a larger development of the phenomenally successful 52 in Veron Impala ( oz4658) which set the original standard and form for a stable, dependable, tough and compact One or Two Channel Radio Hillside Soarer.
A great innovation is the use of uniform plastic wing (and tail) ribs designed with T-girder flanges for rigidity and to hold to even camber the highly successful high - lift medium speed aerofoil section; also the two basic formers in rigidly designed plastic to simplify construction and assembly of the fuselage.
The alternative options with the design are for 2 Channel Radio with Standard Dihedral for Rudder and Elevator, or for 3 Channels with reduced Dihedral for Rudder, Elevator and Ailerons. Substantial trailing edge material is provided for the ailerons to be cut out of the balsa wing structure and hinged on.
Also the nose-block is designed to be secured with a nylon bolt and removable to permit a nylon or metal motor mount for converting to auxiliary power by fitting a Diesel or Glow-Motor of up to 1.8 cc (.11 cu in) capacity. The motor mount is not provided. Power can be applied to both versions.
Simple tools are needed. For the general balsa and plywood structure use BRITFIX 55 White PVA Adhesive. For ABS Plastic ribs and Formers to Balsa or plywood use a heavy grade of Contact Glue (as used for bonding 'Formica') used as a normal glue by application when wet, not tack dry, or HUMBROL 66 Balsa Cement. BRITFIX 88 Epoxy glue will also be necessary in a very small quantity. HUMBROL Clear Shrinking Dope is used - with HUMBROL Coloured Dopes or Enamels for decor - for lightweight nylon, Chiffon - nylon or the Modelspan tissue supplied. Iron-on Mylar sheeting is also recommended such as SOLARFILM..."
Direct submission to Outerzone.
Update 20/04/2018: Added kit review from RCM&E, August 1976, thanks to RFJ.
Quote: "RCME Kit Review No.89. Veron Big Impala, by Ray Favre.
The Big Impala is a 74 in wingspan slope-soarer with a basic shape which will be familiar to many who have built the smaller Impala. It can be built as a 2 or 3 function model and I chose to do the latter ie rudder, elevator, ailerons. Conversion to a power-assisted model is also included in the design.
The big innovation with this kit is the use of moulded ABS plastic for wing and tail ribs plus main fuselage formers. I was a little surprised to read that balsa cement is one of the two adhesives recommended for joining ABS plastic to balsa (the other being heavy grade contact adhesive in the 'wet' state), but it works satisfactorily.
The kit contains comprehensive hardware, but it was here that I found the only fault with the kit. The control horns supplied were not suitable. I like their construction but the type of fixing could not be put close to the hinge line and, regrettably, there was not sufficient distance in front of the fixing lugs to enable the push rod holes to intersect the hinge line. Homemade or other proprietary types had to be substituted.
All other aspects of the kit were first class and several good points are noted in the construction notes which follow. The instructions were copious but do assume some previous knowledge in a few places.
Fuselage: The fuselage is the standard sheet-sided rectangle (ply sheet on underside at nose) with triangular-sectioned corner longerons. The fuselage sides each have to be made from two pieces of sheet with a 'fish-tail' join. A ply template is provided for this and I was very surprised at the accuracy of the joint. Before cutting though you have to think first - always a good principle - to ensure that the length of fuselage is correct. I found that location marks on the plan and on the template were essential to ensure identical sides in this respect.
The fuselage also has a rectangular sectional longeron from nose to tail which neatly serves three purposes (apart from added strength): cockpit canopy reinforcement runners; tailplane platform runners; location projec-tions for main formers. The ply fuselage doub-lers are in two pieces each side - to fit round the rectangular longeron.
The use of moulded ABS for the two main fuselage formers is, I think, a distinct advance. They are far more rigid (and square) than balsa could ever be, yet by careful choice of cross section have neat large openings in them for control linkages, etc. The weight penalty is negligible - indeed they are definitely lighter than a balsa structure with equivalent strength. The other advantage is the accuracy to which the formers can be produced. This allows precise fitting of the formers onto the location longeron mentioned above, as well as triangular lugs which locate with the corner longerons. All in all, a most satisfactory improvement. (By the way, the moulded plastic accuracy really shows up the slight but inevitable inaccuracies of stock balsa - particularly on the triangular section).
As I chose to use cable-in-tube for controls, these had to be installed in the fuselage before completion. Finally, the noseblock is designed to be held on by a nylon bolt to enable its removal and direct replacement by an engine of up to 1.8 cc. I found it a little awkward to get a screwdriver in the right position for this bolt, but it can be done and I concede that it makes for very neat conversion.
Tailplane and Fin: The fin/rudder is entirely conventional and from balsa sheet. The tailplane, however, is not conventional in that it is built with plastic ribs in both the main tailplane and the elevator. These ribs are supplied whole and have to be cut to permit insertion of elevator hinge line support spars. Cutting the ABS plastic was quite easy with either balsa knife or razor saw. Where guidelines are provided by the mouldings, the knife is probably quicker, but I tended to use the razor saw for an accurate straight line - at least to start off the cut.
The trailing edge of the elevator is provided already slotted and location lugs on the ribs permit secure and accurate fitting. Despite the unconventional means of arriving at the finished tailplane, it is an easy exercise.
The fin is cemented permanently to the tailplane, but the combination can be either fixed permanently to the fuselage or held by rubber bands. I chose the former - purely out of laziness. (The fuselage depth at the tail and the short span of the tailplane both reduce the risk of casual damage at the tail end.)
Wings: The aileron version has 2-1/2 in dihedral under each tip (as opposed to 5-1/4 in on the rudder version) and the flight characteristics (see later) suggest to me that the more experienced flyers could reduce this even further.
Wing construction is entirely conventional, despite the plastic ribs. These ribs are I-section or, if you wish, have built-in cap-strips top and bottom. The photos show generous cut-outs for lightening plus this lugs for locating into leading and trailing edge slots - a very satisfactory arrangement.
The weight of each rib was roughly the same as a hard 1/16 balsa conventional rib without cap strips - so there is no weight penalty at all. The plastic ribs are superior in rigidity in one plane but considerably more flexible in twisting and in the direction horizontally at right angles to their normal upright position, This explains the use of several triangular gussets at the centre section of the wing. This flexibility could be an advantage - only time will tell.
Again, the accuracy of the ribs was the most noticeable improvement over balsa - particularly in the main spar cut outs. It was also very nice for once to be able to drop the aileron control wire from one end of the wing to the centre without snagging, yet through a hole only about 0.15in. diameter! (That could say a lot about my balsa building accuracy though.) Slight moulding flashes had to be removed from a few ribs before use.
Finally, the ABS plastic does not crush and so a good tight 'force fie can be made at all balsa/plastic joints without danger of breaking ribs.
The ailerons are of the conventional strip type which are cut out after construction. The control servo sits in a box under the wing in the centre section and the depth of the wing is such that very little of the servo protrudes. The sketches show how the accuracy of the moulded ribs is used to provide ledges for some inset flush sheeting on the bottom of the centre section. The finished wing is in one piece - held onto the fuselage by rubber bands. Leading edge sheeting is on the top of the wing only..."
Update 16/10/2018: Added kit review from Radio Modeller, June 1976 thanks to RFJ.
Supplementary file notes
Instructions, text only.
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User commentsHello again. Attached a picture of my latest project [main pic], a Veron Big Impala (oz6586).
Bob Pickernell - 01/05/2022
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- Big Impala (oz6586)
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