I first became interested in the Maricardo when I saw one being flown back in 1985. Harvey Murray, a friend of mine, was flying all types of aerobatic manoeuvres on the Kettle Field with his Maricardo in a very impressive manner. Harvey’s model was built to the original plan (Radio Modeller 1985) with an upright engine, the original amount of dihedral and banded-on wings. The engine (I think) was a standard O.S. 40. I was so impressed with Harvey’s model that I decided to build one myself, and unwittingly began a tradition in our club. Over the years I’ve made a number of changes to update this superb design, mainly on the suggestion of Gareth Williams, one of the Delyn club’s best aerobatic pilots. I was careful not to change in any way the Maricardo’s good looks, great flying abilities and exceptional stability, which are the hallmarks of C. A. de Felice’s classic design. Just after Christmas last year I completed a further batch of Maricardos for club members, bringing my current total up to 32! I think this fact alone speaks volumes for the model and I’m secretly delighted that with the publication of this free plan, a new generation of modellers will now discover the superb flying qualities of this classic. The Maricardo will fly on any .29 - .53 two-stroke or .48 - .54 four-stroke. The Irvine .53 is by far the most popular choice in our Club, giving the aircraft a sparkling aerobatic performance whilst retaining her legendary stability.
Before getting down to business, I must record my great respect for C. A. de Felice as a designer. In my opinion he got the Maricardo right first time. However, radios, engines and indeed flying styles have evolved, and are now very different from when the Maricardo first appeared all those years ago. Wishing to retain her essential character, all I’ve done is to incorporate a sympathetic update. So this version will knife-edge, spin, invert, and flick-roll with the best of them. You can fly her with as many mixes on your transmitter as you like, and with bolted-on wings and canted over engine you can appreciate her original sleek lines all the better. She still looks like a pylon racer, but when throttled back she’s as gentle as a baby. This makes her an excellent choice as a follow-on model after a trainer, and an ideal first mid-winger.
MODIFICATIONS TO THE ORIGINAL DESIGN
The main modifications I’ve introduced are:
Dihedral has been removed from the wing (improves roll rate).
Original ply dihedral brace is ‘flattened’ but kept to the same size, and used as joiner.
Rudder is increased by 1” in size to improve knife-edge and spin manoeuvres.
Aileron is increased to 11/2” x 3/8” stock (for faster control response).
Engine is canted over so that the silencer exits under the fuselage.
Ailerons and elevator are top-hinged for improved response.
Servos are added to each wing to facilitate tighter response and allow the mixing of controls.
Wings are bolted to the fuselage with a liteply hatch fitted in the underside for access.
Wing retaining blind nut is glued to a ply cross-plate in the cabin.
Two stub dowels in the forward part of the wing locate in a new ply plate directly in front of F2b.
Engine side-thrust is added, 3° for .46 - .53 two-strokes. This provides better tracking and neutral power on / power off trim.
Down-thrust has been removed.
Lower air scoop (that disguised old, bulky radio) has been removed.
Engine mount is now the round series SLEC unit; this has the great advantage of being rotatable, whilst maintaining its thrust line on the centre.
A nose ring is fitted and the nose shaped from 1/2” balsa sheet.
The original dural undercarriage has been replaced by a simple 8 swg piano wire unit, bent to match the original dimensions and retained by nylon saddles.
Elevators have 1/2” removed from the centre ‘V’ portion to increase rudder travel.
The Maricardo is straightforward to build from the new plan, which follows the original very closely. As with all plan-built aircraft, it’s a good idea to make a kit of parts before assembly. Note that the original dihedral is dispensed with, so the dihedral brace is flattened and now becomes a wing joiner. Since she’s a traditional balsa-and-ply model and needs neither cowl, canopy, fibreglass nor commercial items to complete, she is amazingly cheap to build. This traditional building method also produces a model that’s tough and that shrugs off most of the petty knocks and grazes. If you do break a bit off her, it will repair easily, since the construction is so basic. Truth is, if you pay careful attention to fuel proofing and seal all the edges, she’ll probably be flying in twenty years time, barring thumb-trouble, of course!
Begin the fuselage by cutting out the sides and applying doublers, followed by the 1/4” balsa wing seat doublers, 1/4” square longerons, uprights and diagonals. Make sure to fabricate a right- and left-hand pair. Formers F2 and F3 are then glued to one fuselage side, making sure they’re perpendicular. When dry, glue on the second side. The firewall F1 is added next, after which you can pull in and glue the fuselage sides together at the rear, having first chamfered the tail posts and longerons as shown on the plan. The turtle deck formers, 3/32” balsa sides, 1/4” balsa fin seating and fin are glued in place next.
Check that the fin is at exactly 90° and on the fuselage centreline. Add the 1/4” balsa fuselage top to the turtle deck, the 1/8” ply undercarriage plate and the 3/32” and 1/8” underside sheeting to the fuselage. This completes the basic fuselage structure and whilst the remainder is quite straightforward, do note that the wing nut retaining plate is let into the balsa fuselage doubler to provide a firm anchor, i.e. it goes through the balsa doubler to meet the underlying ply doubler.Oh, and by the way: the recommended tank is a SLEC 6oz square job (the red one), though if you desire more air time you can just squeeze in a Sullivan 8oz.
Simplicity itself! 1/8” balsa built-up core, skinned with 1/16” balsa sheet to either side; use medium-to-soft balsa to keep the weight down. The elevators are simple 1/4” sheet items, with a 1/8” spruce joiner - note that the elevators have been altered from the original, with the central ‘V’ slot made 1/2” wider to allow for increased rudder travel.
The wing is similarly easy to build. It consists of two full-depth balsa spars, onto which the wing ribs are slotted. The 1/2 x 1” leading edge is then glued in place followed by the 1/4-square balsa trailing edge. Both panels are built identically, and joined with (flat) 1/8” ply joiners to both spars. The leading edge and trailing edge are then sheeted top and bottom, as is the centre-section.
Add the cap strips, together with the 1/2” sheet wing tips, and Bob’s your uncle!The final task here is to add the cockpit to the top of the wing, as shown on the plan. During construction a thin piece of card placed between F2a and F2b, and another between F4 and F5, will temporarily simulate the thickness of the covering material and allow the wing to seat correctly after you’ve applied your chosen film. The aileron servos can now be fitted into each wing, within simple servo boxes (see photos).
Neat, secure, very easy to do, and you won’t need to use extension leads. Of course, that’s all very well if you have five servos laying around, but if you haven’t and you wish to follow the traditional single servo method, we’ve left the details on the plan complete with torque rods etc.
AND THE REST...
Large wheels are best when flying from rough grass strips - Dubro 31/2” diameter are ideal here whilst the tail wheel is 11/4” diameter. As far as covering is concerned, the choice is yours; most of the Delyn Maricardos are finished in either Profilm or Solartex (these two materials also provide an excellent hinging medium).Quoted weight of the original is in the range of 5 - 6 lb, however most of my Irvine .53 powered Maricardos weigh in at between 41/2 and 5 lb.
Mr de Felice obviously got his sums right, because none of the 32 Maricardos I’ve built so far have needed any lead ballast to balance at the stated C of G, which is 31/4” back from leading edge. Experienced aerobatic pilots may wish to experiment with this, once correct flying has been achieved.The control throws recommended for the original remain a good starting point for a predictable, docile model, however if you wish to have more vivid responses to control inputs you’ll have to experiment with much greater throws. Certainly the rudder travel will need to be increased in order to provoke a fully-developed spin, and assuming you chose the outboard servo positions for aileron control, mixing of this function will be much more versatile.
The Maricardo is quite a large and impressive model for this engine range and she isn’t short of wing area, so has a good speed range with excellent lift, and a superb glide. She is stable at all times; at low throttle settings she’s amazingly docile, giving excellent approach and landing characteristics. Ground handling is first rate, and if you want to get into tail-draggers (after your tricycle trainer) she’s the one.
She’s an excellent low-wing trainer on a .40 and returns superb aerobatic performance on an Irvine .53, which is both quiet and powerful. This model is capable of flying anything in the book, indeed the performance is only limited by the pilot’s skill. Inverted flight is very neutral with just a touch of forward stick required... I’ve seen Gareth Williams spinning his Maricardo down to grass level, flat inverted! Although you might not think it to look at her, she has excellent knife-edging capabilities, too. Couple that with a racer’s good looks and this model is just about the perfect all-round sports aircraft.
Aircraft type: Sports aerobatic
Designed by: C.A. de Felice
Updated by: Paul Strawson
All-up weight: 4.5 - 5 lb
C of G from l.e.: 31∕4'' back from l.e.
Rec’d engine range: .29 - .53 two-stroke
.48 - .54 four-stroke
Rec’d no. of channels: Four (five servos)
Control functions: Aileron, elevator, rudder, throttle
Control deflections: Aileron ± 1∕4'', elevator ±1∕2'', rudder ± 1''
This article was first published in the April 2004 issue of RCM&E.