We have to use a theory for science whether plastic, card or paper makes a better sail. Please give me your opinion. Thanks heaps!
The sail has to take a curved airfoil shape to be effective so card would not be best since it won't bend well. Paper falls apart when wet, not a good choice for a boat. Plastic is the best choice. High tech sails are made with mylar and kevlar, special types of plastic.
Since a sail acts like a wing at at least some angles to the wind any material ridgid or flexible can act as a sail as long as it can maintain its shape. At other sailing angles it acts as an impeller and this requires a different shape to be efficient. Since the sail serves different functions at different wind angles it is probably best to use a flexible material that can be modified on the fly ie cloth sails. Paper would seem to be the closest to sail cloth with the provission of it not getting wet of course!
OOOPS... Someone needs to do some serious updating here... Today's technology doesn't stop at Dell or Microsoft... That is where it begins... Fact is Rigid Sails are now proving to be much, much faster then cloth. Now rigid airfoils on sailing vessels (especially on multi-hull sailing vessels) are shattering all kinds of world speed records across the water. The trick is balancing maximum strength with mimimum weight and keeping it all together. I don't really know the answer to your question - only to say that if you are building a model (either real or imaginary) a rigid sail is proven best... as to plastic, card, or paper - I would go with the one that gives the best strength ratio to the rest of my model. The site below also has a lot of links that may be helpful. Have fun! Capt. John
Plastic sheeting like construction plastic would work the best. I cannot explain it in scientific terms but you would get the same effect as using sail cloth. But the plastic would not be as strong as cloth.
