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Sri Lanka
Joined Mar 2010
571 Posts
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Quote:
My Cessna is still progressing, flies OK but fast, I am putting the finishing touches on it now |
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Sri Lanka
Joined Mar 2010
571 Posts
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Photos of the Cessna
A flew good flights yesterday, despite the damage to the model. Attached are some pictures.
The model flies straight and level, with the emphasis on level, a 40 g monster is not going to break any time to height records. The rubber motor only spans half the fuselage so there is room for improving the 5 second or so flight times. Unlike previous models, it does have some reserve power. To increase lift, I cut the flaps section and bent the card downwards about 30 degrees. There was a definite improvement in lift and flying performance. Need to repair the model and test it out in a large field. No luxury of tall grass, and the model has already sustained an crash on its nose from 10ft ( 3 metres ) up, when a gust of wind pitched it up in a zoom climb, and it stalled. I am somewhat pleased with its durability, though, especially the wing and wing/fuselage attachment points. The fit and finish leaves something to be desired so I would appreciate comments on how to make it look better and neater. |
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Sri Lanka
Joined Mar 2010
571 Posts
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I decided to build to 1:32 scale instead of the 1:24 scale. The smaller scale is more convenient, and the plans will fit on A4 pages. Wing loading will be higher, but using paper for the wings and other weight saving techniques it should fly well enough.
1:24 Scale Length: 33 cm Span 46 cm 1:32 Scale Length: 25 cm Span 34 cm This means a 34% decrease in wing area. I will be building the wing bigger than scale, in this case. The photos show the construction details of the fuselage. Using Bristol board instead of paper results in a smoother fuselage without any buckling of the material used. The center tunnel houses the single rubber band. Right now weight with prop and rubber as installed is just over 23g. Cut outs and weight saving will come later. |
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I hate to say it but at 23gms already for only about half the model for a 25cm span you may as well stop right now. That's far too heavy to fly well at all. An acceptable weight for just the fuselage and prop for this size would be about half that weight even for casual front yard sport flying.
You're going to need to find ways to use less material. For example I see that you're still using a motor tube and wrapping a fuselage around that tube. That's a lot of extra material to achieve what is basically a doubling up of the construction. Perhaps work on forming the outer skin into a U shape with a glued in top cap so it can be stiff enough to accept the rubber loading on it's own. Even just making the tabs on the formers smaller would be a good step in the right direction. |
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Sri Lanka
Joined Mar 2010
571 Posts
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I have been continuing to build some test models. Got rid of the motor tube and tested a fuselage that could withstand the torque of the rubber motor upto about 100 turns or so.
Following previous advice, I have started experimenting with a non scale stick plane with originally a 40 cm span and weighing oh maybe 20 grams or so due to styrofoam wings. Replaced the styrofoam wings with bamboo and paper and the model flies surprisingly well, although impact resistance and water resistance is very low. (I'll say!) Also deformation is also a big problem. All this will be solved with a new design taking inspiration from this designer in this post: already a test wing has been built and is quite strong but weighs 7g per side for a 30 cm span wing. Will post pictures of it all. What a journey. |
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Sri Lanka
Joined Mar 2010
571 Posts
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Stick Plane and test wings
Pix
How much does it weigh? I have realized that an accurate weighing scale is critical to this project, so I am building one at present. I have the weights for calibration. Weighing scale post Flew the stick plane with the pictured wing, covered with light covering paper. Due to the undercamber and the improved structure and the uniformity of the wing, it actually flies quite well, although heavy -maybe 35-40g, and does not change direction too much, very stable. This opens up all sorts of possibilities for cereal box cardboard. I am not going for long flights, 15 seconds will be good enough if given the space. Cheap materials and easy building - there as to be a downside - but this is a great educational tool. |
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Sri Lanka
Joined Mar 2010
571 Posts
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Stick 180 wings and tail
Pictures of stick plane with 180 wings and tail
Construction Continuing the experimentation I have rebuilt the foam stick plane using cardboard wings and tail. The material used is "Bristol Board" or thin card. The wing is made out of the cardboard with a single spar over which the cardboard is folded. The wing is solid cardboard. The tail and rear stabilizer are single side thin cardboard except for the folded leading edge. The fuselage is the original wooden stick that came with the original plane model and is very stiff and strong. The propeller is a Guiilows like unit about 6 inches in diameter (15cm). Power is provided by a loop of 3mm wide rubber that can take upto 10 turns without breaking. As you have guessed, the wings and tail are patterned after a 1/32 scale Cessna 180. Specifications Span: 40 cm (10 ") Weight: 30 g (estimated) Flying: How does it fly? Quite well, given the fact that it is still unstable in pitch. After trimming out the initial tendency to bank left and turn it performed a few straight , stable flights on 140 turns. It does fly. Durability Durability is the key factor here: the pictures you see have been taken after about 10 flights, all of them ending in a sort of crash or another. Under these conditions the model has stood up quite well, thanks to the stick fuselage, rugged prop and also the material used. Appearance The material used makes for a relatively smooth finish that can be painted and finished nicely for a scale model. Basically the Cessna 180 wings and tail are done now, and the wing can be made somewhat lighter than this one. Scale models now seem within reach, at least a scale model that will putter around the 'front yard' without breaking any endurance records. For a child who assembles and builds such a model, there is a great deal that can be learned from this model and can pave the way for model building. Next Steps A full fuselage model is under construction, and since weights are satisfactory for my purposes, it looks like it will fly as well. This model, lets call it the Stick 180, will be balanced properly and flown again, possible with added camber and more power. |
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