OK, friends, forgive me up front for starting this but it is somthing we really need to address. About year ago I was running in some F2A engines and switched from a bottle of commercial 80/20 to my home-mixed 80/20 and my engine speed dropped enough to concern me that I was loosing a glow plug. Many plugs and much head scratching later, it finally dawned on me.
In my background is a bit of experience in bottling liquids and all the commerial bottling equipment I have seen is based on weight. So, a quick look at the CRC book, I noted that the specific gravities of methanol is 791 and Castor oil is 956. So, if one mixes or bottles based on weight, there is a much higher than 80/20 ratio of methanol to Castor oil and therefore a “hotter” fuel.
Reading the AMA and FAI rule books there is no mention of how the the 80/20 (or any of the fuel ratios) are to be determined. Since a fair number of fliers mix thier own based on volume, I sugget we ask to have “by volume” add to the rules. It is a simple matter for fuel bottlers to calculate the weight limits from the specific gravities of the fuel components.
Ron Bennett, Monmouth OR