Posted by knlever |
Jul 24, 2010 @ 05:07 AM | 2,831 Views
1) The HLG has flown, and although not exactly scale, it proves the concept. Thinking of the next model.
2) The cardboard, bamboo and paper wing has been sucessfully tested on the stick rubber powered plane, I had to add an extra rubber band for more power and flies satisfactorily - a short 15 metre flight or so but entertaining enough.
Now to build a scale fuselage and make that fly. Plan - Do - Study - And... I forget the next Adjust? Works for me.
I am looking at the set of vintage sheet balsa kits ...
Can alternative materials replace sheet balsa? The answer is yes, and it has in some cases, but what about weight?
Some free flight sheet balsa models use sheet balsa, and balsa has a density of between 5 and 10 lbs per cubic ft. ( 88 - 160 kg per cu metre)
A sheet balsa wing of 12 inches span and 3 inches wide ( 30 cm by 7.5 cm ) will weigh about 1.6 g and can be replaced by three bamboo spars and covered with 80 gsm paper. The paper will weigh 0.0225 sq metres weighing 1.8 g. What will the bamboo spars weigh?
Twice or more the density of balsa, so say Bamboo 300 - 400 kg/ Cu metre.
Volume of the spars : 30 cm x 1mm x 1 mm = 0.0000003 cu metres, and will weigh 0.36 g
So we have: balsa wing weight: 1.6 g
80 gsm paper weight for the wing area: 1.8g
Tissue paper weight for the wing area : 0.9g
40 gsm tissue paper wing with bamboo spars 1.26g
80 gsm paper with wing bamboo spars 2.16g 35% heavier
Cardboard is about 7 times the density of balsa, so using cardboard sheet and cutting out 1/7 of the area or more and covering with the 80gsm or tissue paper will result in a fairly light wing.
Added a set of posts on problem solving - applying these problem solving techniques - for example the '5 whys' I came across in the course of my work, and root cause analysis may speed up progress which has been somewhat slow.
I hope that other modelers will benefit from this approach.