aeroplumber
Newbie
I have a sport copter with a 618 engine with a three to one gear ratio. It has a powerfin with a 66 inch prop now. I called Darrell @ warp drive and he told me that the three to one gear ratio with a 66 inch prop is wrong. He said it will work OK on a 582 and of course a 618. But with the 10 extra HP your losing torque and thrust. Jim @ Sportcoter said he could never see much difference between the 618 and and 582. Darrell says that reason is in the just assuming whats good for a 582 is OK for a 618. He says a 618 is real beastly when set up write. He says the higher the gear ratio the larger the prop needed and the lower the diameter of the prop the smaller ratio needed like 2.62 would work best. I only have room for a 66 inch prop. I installed a 68 inch prop with the 3 to 1 ratio which gives me just 1" clearance. Darrel also explained by using the three to one gear ration with a 66 inch prop turns it into a cruise prop like 120 mph and not good for a gyro. So what do you guys think. Mick