Span 58.5 cm / 23 in
Weight 68 g / 2.4 oz ready to fly
The original Whatsit was designed by the great American model builder Frank Ehling (1914-2001) and was published in the 1/1942 issue of Airplane News. What made the Whatsit so distinctive and unique was that no one could tell for sure what it really was. — Was it a biplane without a horizontal stab? Was it a twin flying wing? Was it some sort of an elegant flying flea?…
I built one glider version 1024 enlarged by 157 % and one version enlarged by 192 % (here) for my rubber power unit (RPU 30).
The original plan was used with minor alterations only.
Further details:
https://outerzone.co.uk/plan_details.asp?ID=15004
https://freeflightarchive.com/images/plans/clg_hlg_plans/Whatsit_oz15004_article.pdf
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 Whatsit
https://outerzone.co.uk/plan_details.asp?ID=15004
Material:
Fuselage: hard B 1 or 1.5; wings: hard B 1 or 1.5; wing supports: B strips 5 x 5; wing struts: B 1 sheet; fin: B 1; linen band width 10 mm / ½ in; two pieces of Velcro tape; ballast: 5 g / 0.18 oz lead or scrap steel.
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