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Old Oct 08, 2004, 07:59 PM
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Originally Posted by Erez-E
As an engineer, I take offence to that comment. Just for my own edification, I want to see a breakdown of the material cost. I'm not considering molds, pump and whatever else you need to buy once.

So epoxy is what, about 9 lb/gallon? Let's say you've got a 20oz plane and a fiber fill ratio of 60%, so that's 8oz of epoxy. Let's say you waste a bit and use a 16 oz. That's .11 gallons. If the epoxy is about $80 a gallon, including hardner, that comes to $9 worth of epoxy, lets say $10 with shipping.

Wax is relatively free.

Ok, on to the graphite. 3k is about 6oz/yd^2. and about $22/yd^2. So carbon is about $4/oz. 60% of 20oz is 12 oz. soooo that's $48 worth of carbon. You would need say $12 worth of peel ply and breather.

So for an all carbon jobbie, your total cost would be $70, again assuming you have the mold (this is where the problem is), a pump (~$300 for a kit), AND assuming you buy in small quantity.
Not so fast--3 oz carbon costs more like $80-90 sq yd, Kevlar about $20 for the 1.7 oz sq yd nice stuff, high grade carbon tow for the spar caps $100lb, Epoxy that will give long enough working time yet set overnight $100 gallon, Roha Cell $40 for 24/48/.032 inch sheet---etc --etc--etc. The costs go on! Material costs are just the start--you have also to put into the mix the cost of the parts that don't come out of the mold in one piece too.

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