After seeing a posting on otherpowers message board of a 700mph coffee can i decided to have a look into how a Darrieus works and to see if i could make one myself that would self start.Looking at the ROPATEC which is made in italy it has non symetrical wings just like a plane, i knew i had a set of model glider wings at my parents house left over from my model flying days, at first i played with the idea of cutting them up and making two wings. I remembered that there was 2 spacers where the wings slotted into the Fuselage and these spacers were the profile of the root of the wing so i removed one of these and used it as a template, the rest they say is history.
Using the spacer as a template i marked out 16 ribs out of doulble sided cardboard, the type with the corrugated card in the middle. I decided to use the corrugation as if it was the grain of wood and these grains run the lenght of the rib for strength, then i cut the 16 ribs out.
With a hot glue gun i made 4 thick rib sections by gluing 4 ribs togehter.
Once again using the same strong card board box and cutting two of the boxes flaps off i mounted the 4 thick ribs on the ends of the flaps. Here you will see that the leading edge is not on the flap as the cardboard was too strong to work over the leading edges.
Not being happy about getting the wing skins on those 4 thick ribs i cut out another 20 ribs with the same method as the other ribs and glued them together in 2 sets of 10 then glued them to the base in the middle of each wing. I can now skin over each wing with 2 pieces of card.
To skin over the wings i used cereal boxes as these have a smooth glossy finish on one side which should help the air flow better and a rough card finish on the other side which will adhere better to the ribs.It also bends easier to form the curve on the leading edge
PHEW 2 wings built and thats the hard part over with, all i need to do now is have a top and bottom to attach them to.
Now there mounted with a top and bottom and these were cut from the double sided cardboard box. I drew 2 lines on each from corner to corner to find the centre. I put a hole in the bottom and glued a toilet roll tube to the underneath of the top.
A broom handle and some wind and its reached its finale prototype stage. It didnt self start but that might be because the wings are too close togehter but with a spin to start it it nearly took off and reached some incredible rpms am i glad i tried this with card board !!! It was the lack of self starting which has got me thinking but i shaw liked the rpm and will return another day. If any body wants a copy of the rib template email me and i will get it scanned, there should be no reason why it cannot be scaled up or down.