Dan,

Try this site, and change the numbers in their work sheet till you get it to the desired level. I even use their formula for mixing diesel fuel, by substituting ingredients. Scroll way down till you see the options to Add oil only, or Add Nitro and oil.

http://www.nitrorc.com/default2.asp?Introduction=http://www.nitrorc.com/fuelws

Bill

If you have 29% castor now, in one gallon of fuel, you have 0.29 gallons of castor.

If you have 0.29 gallons of castor and you want 15% castor, you want to increase your total volume to

(0.29 gal)/0.15 = 1.933 gallons.

So whatever else you do, you need to add 0.933 gallons total of stuff.

Of that 1.933 gallons that you end up with, you want 11% to be synthetic.  That works out to needing to add

(1.933 gal)(0.11) = 0.213 gallons.

So, of the 0.933 gallons that you're adding, 0.213 are synthetic oil, and you need to make up the rest in methanol.  That works out to

0.933gal - 0.213gal = 0.720gal

So 92 ounces (11 1/2 cups) of methanol,
27 ounces (3 1/4 cups + 2 tablespoons) of synthetic,
and your fuel.

Thanks guys! Thats exactly the info I needed.
-Daniel

Without getting too deep into the math, you will end up with about 40% total oil.

Since when has 11% + 15% added up to 40%?  When I was growing up it was always 11 + 15 = 26.

Granted, 26% is a tad high -- but it's not 40%.