BumbleBee Rudi (oz15730)

 

BumbleBee Rudi (oz15730) by Arthur Nicolae 2020 - plan thumbnail

About this Plan

BumbleBee Rudi. Control line sport model. Wingspan 784 mm.

Direct submission to Outerzone.

Hi friends, in 1987 the 'Modellbau Heute' magazine published a funny plan designed by Winfried Grabsch who wanted to bring a smile on the spectators faces: Hummel Rudi (oz15729) which means 'Rudi the Bumblebee'. I built the model in 2000 without using a single bit of balsa and I covered it with japico paper. An MK-17 (1.5cc) engine was powerful enough to lift the Bumblebee into the air. It was really fun. Now, over the years, I feel obliged to try the same thing.. to pull out a few smiles.

That's why I redesigned the model and updated it for modern technology. I created a much lighter structure, I corrected the symmetry errors in the original plan and based on experience I made a few small changes.

I gave up on the wing's dihedral because it made the model sideways dancing at the slightest breeze. The wings are mounted on 2 carbon tubes (aluminum tube can be used as well) which thus ensure strength and correct alignment. The tube near the leading edge must be glued along the spar box (CA is very good for this).

The wheels used are smaller in diameter but sufficient for taxiing on grass. The landing gear was made of 2.5mm steel wire instead of 3mm, which saves some weight. Very important, compared to the original method, the landing gear is made of 2 pieces, which after being glued into the fuselage (I recommend epoxy glue) must be tied together (at the base of the fuselage, at both ends) with a thin copper wire and soldered. This way even if the model suffers a harder landing, the landing gear will not break the plywood side face.

In order not to have to adjust the side angle of the engine I moved the bellcranck into the fuselage. A groove is dug in the balsa core for the shaft of the bellcranck, and the bellcranck is mounted before gluing the plywood sheet on the right side of the model. This solves several problems of the original model.

For balancing, a hole was provided on the outside of the right wing where a lead button must be glued (8 grams should be enough).

The model flies beautifully in a circle with a radius of 11m. If you want to use longer cables (16m for example) I recommend a 2cc engine.

In the plan I have also provided dimensions for a flat tank, especially designed for engines that have the carburetor at the back... this type of tank is not suitable for inverted flight but allows evolutions such as wing-over, looping, etc. For more acrobatic evolutions, a classic triangular prismatic tank is necessary, aligned with the engine axis.

The final dry weight of the foil-covered model should be less than 400 grams. Today there are synthetic wires on the market that are much lighter and thinner than the metal wires used in the past, for this model some that can withstand 15~20kg would be more than enough.

I have also attached the *.dxf files for laser cutting, so the model will be even easier to build.

In the end, I can only hope that I have achieved my goal... and I am waiting for your smiles. eng. Arthur Nicolae.

Supplementary file notes

Parts zipfile (dxf format).

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BumbleBee Rudi (oz15730) by Arthur Nicolae 2020 - model pic

Datafile:
  • (oz15730)
    BumbleBee Rudi
    by Arthur Nicolae
    2020 
    30in span
    IC C/L
    clean :)
    all formers complete :)
  • Submitted: 27/11/2024
    Filesize: 3627KB
    Format: • PDFbitmap
    Credit*: ArthurNicolae
    Downloads: 268

BumbleBee Rudi (oz15730) by Arthur Nicolae 2020 - pic 003.jpg
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BumbleBee Rudi (oz15730) by Arthur Nicolae 2020 - pic 004.jpg
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BumbleBee Rudi (oz15730) by Arthur Nicolae 2020 - pic 005.jpg
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Scaling

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