3035 Tubarão RPU 30

Span 58 cm / 23 in

Weight 58 g / 2 oz ready to fly

The concept:

After having built Tubarão gliders and rubber powered models consequentially a RPU model of the proven design had to follow. Here it is and it is big. 

Features:

• Shark-like fin, nose, horizontal stab tips and wingtips
• For RPU 30
• Few parts
• Easy to build
• Good flight performance

The name of the plane is Portuguese/Brazilian and means of course shark.

Rear end of the Tubarão was drawn up in accordance with the rear of the French sport coupé Panhard CD from 1963. The rest of the model is totally sharkish.

Brazil’s coastline measures more than 7000 kilometers. And the coastal waters are inhabited by more than 100 different shark species. Among the more aggressive ones are the Bull Sharks, the Tiger Sharks and the Nurse Sharks. Others are the Brazilian Sharpnose Shark, the Scalloped Hammerhead, the Whale Shark, the Reef Shark, the Angel Shark and the Dusky Shark. Bull Sharks also love to travel into freshwater like for example into the Amazonas river.

Most shark attacks on humans occur in the waters of the Recife region (state of Pernambuco) or around Rio de Janeiro. Especially active are sharks in summer as they follow food sources close to the shore. Sharks also prefer to come closer to the coast at high tide. 

Since 1931 Brazilian statistics recorded around 110 confirmed attacks by sharks, in average there are one to three incidents a year. 

What is RPU?

RPU stands for rubber power unit.

This is a device designed for the modelbuilder who likes to fly many models with one only powerunit. Main material of the RPU comes from the grocery store around the corner: four barbecue skewer chopsticks. Add to them scratch balsa, a hook made from piano wire, some black rubber and a commercial plastic airscrew. That’s all. 

The unit is attachable through two pieces of Velcro tape and can thus be used for example first on a little Spitfire five minutes later on a Mitsubishi Zero and ten minutes later on a Macchi Folgore of the same configuration. You build only one RPU and use it on as many modelplanes as you wish. 

Models with RPU use the same asymmetrical principle as is known from No-cal models. From the one side they look handsome as from the other the power unit disturbs the harmonic view considerably.

Generally there is no great difference between the flight performances of a balsa sheet profile model with built-in rubber motor and a model flying on a RPU.

Why not try both principles? Among the plans range of beginner.zone you will find models of both categories. Sit down, build, fly, compare!

I developed and tested three different types of RPUs. 

• The one for small models of 30 cm / 11.8 in to 40 cm / 15.75 in wingspan is the RPU 20 (lenghth 20 cm / 7.9 in).
• The one for medium sized models with a span of 40 cm / 15.75 in to 60 cm / 23.6 in is the RPU 30 (length 30 cm / 11.8 in).
• The one for larger models of up to 80 cm / 31.5 in wingspan is the RPU 40 (length 40 cm / 15.75 in). 
• The RPU 40 is made from slightly different material. Instead of the skewer chopsticks it uses two strips of bamboo wooden sticks (400 x 9 x 3 mm). The rest is identical.

Building the sheet balsa RPU model Tubarão RPU 30.

Materials:

Fuselage: hard B 3 or B 4; wing supports: B strips 3 x 3; wings: B 2 or soft B 2.5; horizontal stabilizer: B 1; horizontal stab supports: B strips 3 x 3; fin: B 2.5 or 3; linen band width 1/2 in or 12 mm; ballast: scrap steel or lead.

Assembly:

Cut out balsa parts in accordance to plan. Cut slots for wing and horizontal stabilizer. Sand well. Transfer outlines of cabin, rudders, elevators, flaps etc. from paper to wood with pen (photo).

Wing:

Wing consists of a right and a left wing half. Fix one wing half on building board with pins. Cement corresponding half to it by paying attention to dihedral (100 mm) given in plan. When dry reinforce joining area with linen band (photo) and let dry. 

If wing has tendency to rest on one side only, then it is too heavy on this side. To compensate the imbalance, disperse a small amount of white wood glue on the opposite wing tip area and let dry. Do it, if necessary, twice until balance is obtained. Let dry.

Fuselage:

Cement fin on fuselage. Let dry.

Cement wing support on left side into position (photo). Turn fuselage around and repeat this procedure on right side.

Empennage:

Fix fuselage on a so called ‘third hand’. Cement horizontal stab into position using pins to hold in place. Visual check symmetry. Let dry.

Final Assembly:

Turn fuselage upside down and fix it again on ‘third hand’. Cement wing on fuselage and on wing supports. Use pins to hold in place. Doublecheck visually symmetry. Put aside and let dry.

Attach two pieces of Velcro according to your RPU on right fuselage side.

For balancing your model properly install RPU and start testgliding over tall grass. Add ballast according to your test results. Note given position of CG on plan.

Remember correct center of gravity (CG) is essential for successful flights.

Many pleasant flights! (Size bol başarılı uçuşlar diliyorum!)