Before I start flying precious scale models ...
The kit I built is the Multiplex Big Lift II, the second edition of the classic 'working horse'. The Big Lift has been a very popular model for many years, known for its good flying characteristics.
| Span | 2.225 m. |
|---|---|
| Length | 1.620 m. |
| Weight | 6 kg. |
| Engine | Saito .80 / 13cc four-stroke |
Some words about the kit...
The Big Lift is indeed a pleasure to fly, yet the kit was somewhat disappointing to me. Compared to the original Big Lift, the kit of the Big Lift II has new parts added for the landing gear and the wing struts, but for the rest it's old news. To my opinion they should have reconsidered the construction as well.
The thing that amazed me the most was the construction of the wings. Each wing halve consists of two parts, a straight and a tapered one. These two parts are supposed to be built separately, each with its own spar and then just glued together rib to rib! Although some people assured me this is strong enough and no one ever heard of a Big Lift folding up its wings, I still think this is no proper construction. I have build the wings with spars and sheeting from root to tip as it should be.
By mistake they've made the aluminum landing gear 5 centimeters higher than the original landing gear which made it look high-legged like a stork. I have bent it to lesser height.
The wing strut attachments for the wing can't be used. These parts are mounted to the wing with one bolt only, so there's no fixation in the direction of the forces from the wing struts. Furthermore the bolt is supposed to go through the bottom wing spar and you should never weaken your wing spar like this.
"Strength comes from construction, not from thickness." This notice does not apply to the construction of the Big Lift. I really couldn't see the reason for the heavy 5 mm balsa for the top and bottom fuselage sheeting. Whereas other important spots needed stronger material. Balsa wing spars for a model of this size? I'd rather have them from spruce.
Another improvement could be to make the angle of incidence of
the wing less. While building I wondered about that angle, because
most high winged trainers I know have the bottom of the wing parallel
to the datum line. The center line of the profile is from leading
edge to trailing edge, so with the bottom of the Clark-Y profile
parallel to the datum line the angle of incidence is still positive.
That big angle of incidence the Big Lift got, is from the past when
they controlled model airplanes by rudder and throttle; using throttle
for pitch control. It makes her very sensitive to speed.
When my Big Lift survives my training, I think I will revise her
(strip the covering, repair the damage and refinish her) ... then
I will also rebuild the cabin top, putting the wing bottom parallel
to the datum line. (In which case the down trust of the engine has
to be made less too by one or halve degree, I think.)
All in all, the model needs some modifications and the kit is a bit expensive for what you get. It made me remember why I prefer scratch-building. "Building a kit is finishing someone else's job."
More Big Lift pages:
Multiplex Modellsport
Choose "Produkte", "Flugmodelle", scroll down to papragraph
"Holz-Modelle (ARF und Kits)" and choose "BK Big Lift".
Hans
Meij Modelvliegen
Choose "Bouwprojecten" from the menu, then "Big Lift".
Struts
versterken
A building tip for the original first kit.