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cconry wrote:Sofan--did you say you used 2 or 4 rotors?

Is anyone using two layers of ~6 rotors each?

2 rotors

As covered before, a rotor can have any number of blades. I suspect that you mean 2 rotors of 4 blades. I guess that if they were directly hooked together and not independently rotating it would be 1 rotor of 8 blades, but that probably would be confusing.

is mylar suppose to be in the $40-50 range?(for 50 feet) I need to know if i am getting ripped off.

sofan wrote:is mylar suppose to be in the $40-50 range?(for 50 feet) I need to know if i am getting ripped off.

It depends on how thick/thin you are getting.

Save your money. Using mylar is going to save an insignificant amount of weight compared to the weight of the egg. The variability of the weight of eggs is probably larger than the weight of a nicely built device. Saran wrap or the equivalent will do the same thing. Our students are going to use a very thin plastic from large bags that we got from a large local department store. It is a lot easier to work with.

Nooo, don't use Saran wrap, that's stuff's nasty heavy. Looks the same and all, but its surprisingly heavy.

Good indoor mylar is a little pricey, haven't checked lately, Roy White generally offers indoor mylar at good prices to SO students. But frankly it is probably overkill for this event, unless your wing area is getting so large that it represents several grams in weight savings..

Much cheaper, and probably good enough is a good Japanese tissue.

Cheapest (free) is retired1's suggestion, the lightest plastic bags you can find. Collect samples from as many local stores as you can. Check your parents for which store bags they hate the most. Don't forget produce bags, sometimes they are very light. Cut out 10 in by 10 in (or at least consistent size) squares and WEIGH them. Figure out the weight per unit area, pick the lightest. You'll quickly find bags that are lighter than Japanese tissue, FAR lighter than Saran Wrap, and sometimes approaching indoor mylar.

Jeff Anderson
Livonia, MI

I'm curious, how about mylar helium balloons you find at party supply stores? They aren't very expensive. Are they too thick to utilize?

Only way to know is to cut a sample and weight it.

But I suspect it is on the heavy side, the helium in those balloons provides LOTS of lift, on the order of 50 gm for the large ones (from memory when we had balloon launch glider). The material needs to be robust/leak free more than light. And from handling experience I know the balloon material is FAR heavier than indoor mylar. I think its heavier than the lighter shopping bags, but thats in the range of guess, not fact.

Jeff Anderson
Livonia, MI

Another option for the people with a tight budget is using crystal paper. The stores that sell crystal and fine china type stuff wrap the glass in it. Most will give you several sheets for free because it is a good cause. It is a bit heavier than some plastics, but it is a lot easier to use. It is a very thin paper, not in the Asaki category, but a lot lighter than silkspan.

Any ideas for the materials for the blades?