Span 50.5 cm / 20 in
Weight 55 g / 1.9 oz
The concept:
• Easy to build.
• Good flight characteristics
• Few parts
• High wing monoplane layout
Tomek is a popular Polish name for boys and at the same time the affectionate diminutive form of the name Tomasz. The last being the equivalent to Thomas, Tomás, Tomaš, Tomas, Tommaso, Θωμάς, Томаш, Фома.
Origins of the name are Aramaic or Greek and its meaning is twin or double.
In Poland Tomek is a name with a friendly nature and its bearers are associated with being reliable, reasonable, logical, disciplined, wise.
In a certain way are some of these features as well applicable to my model Tomek.
Poland is more than worth a visit. People, landscape, historical sites, flora and fauna, flying schools, aviation in general… I couldn’t resist, there is no other country in this world I visited more often than Poland!
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 Hurricane five minutes later on a Zero and ten minutes later on a Reggiane 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 BEGINNERZONE 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 a bit different from RPU 20 and 30. Instead of the four skewer chopsticks it uses two strips of bamboo wooden sticks (400 x 9 x 3 mm). The rest is identical.
Building the balsa sheet model Tomek RPU 30.
Materials
Fuselage: B 3; fuselage side stiffener: B 3; wing: stiff B 1.5; wing support: B strips 3 x 3; horizontal stab: stiff B 1 or B 1.5; horizontal stab support: B strips 3 x 3; fin: B 1.5; linen band width 10-12 mm / ½ in; Velcro tape with adhesive backside; ballast: steel or lead or a coin.
Assembly
Cut out balsa parts in accordance to plan. Sand well. If colouring is desired do it now.
Fuselage:
Pin fuselage onto your building board. Cement fin on fuselage while observing diligentlysymmetry. Let dry.
Cement fuselage side stiffener, wing support strip and horizontal stab support strip into their respective places on the left side of the fuselage. Let dry.
Cement wing support strip and horizontal stab support strip on right side. Let dry.
Wing:
Wing consists of a right and a left wing half. Pin right wing half onto building board. Underlay left wing half tip in accordance to required dihedral. Join both halves with glue and cover wing joining area with linen band. Let dry.
If wing has the tendency to rest only on one side then it is too heavy on this side. To compensate the imbalance disperse an amount of white wood glue on the opposite wing half’s tip underside. Do it if necessary twice until balance is obtained.
Horizontal stab:
Fix fuselage upside down on so called ‘third hand’. Cement horizontal stab on fuselage and on horizontal stab supports as shown on plan. Visual check symmetry from all sides. Let dry.
Final Assembly:
Remove fuselage-empennage assembly from ‘third hand’, turn it upright and fix it again.
Cement wing in place. Check symmetry and let dry.
Stick two pieces of Velcro according to your RPU on right fuselage side.
For balancing your model properly install RPU with airscrew and start unpowered testglidingover 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.
Miłego lotu! (Tenha um bom voo!)
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