Asymmetry

[Fear the Duck]

Circleburners, as far as I've seen, are always built with the coaming sides off-center, to shift the center of gravity of the boat slightly to the left, thereby helping to keep the skid fin planted and making it less likely for the right sponson to dig in and hook the boat. Being native to a different racing scene where hydros run center fins and turn right as well as left (Cal-Ore River Racers), I have to wonder about the effectiveness of this imbalance. Could a balanced boat, with a bit more leaning from the driver, corner competitively? I can't help but think that a balanced boat could potentially be faster on straightaways, since the airflow underneath the boat would be uniform and the weight of the driver wouldn't be forcing the left sponson to drag. An even air cushion could perhaps raise the skid fin faster, allowing for quicker acceleration out of the corners. Am I way off, way out of line with this? Thoughts on this topic?

[les]

Most of the builders put a little twist deliberately in the bottom to help compensate for the offset, Among other things.

[STEVE FRENCH]

I believe Frank Zorkin builds the Z-Crafts with a centered cockpit.......Dana?

[sam]

Prop torque is not centered or balanced

[les]

Prop torque is not centered or balanced

Good point.
So tell us some secrets, Sam. What sort of bias do you put in your boats to make them fast on ovals? Does the length of the course come into play?

[sam]

Yes, the longer the course is, the less likely I am to finish a heat.

Maybe that's why I liked Denton.

[ZUL8TR]

Cockpit offset

The offset in the hydro I run (20ss 10ft range) is 2" left. I cannot notice the effect of left balance bias. The extra 2" provides a slight extra distance to lean into the turn. Also most cocpits are 18" and that allows the driver (w/o a big butt) to shift right (in a kneel down) a bit to compensate in the straights. The 2" offset on the hydros I have run seems to have no effect on aero or bottom lift.

[Fear the Duck]

Thanks for the feedback, I actually never thought about the prop torque. Makes sense. I'm designing a hydro right now, so these are good bits of info to keep in mind as I doodle.

[fbref5269]

the oconner hydros are offset

the oconner hydros were built offset and they handle nice in the corners. i just have to get use to mine. the streering is centered but the cockpit is offset you may want to check with occoner owners to see how they like their boats.

frank novotny

ps
sam, i am still smiling over your last posting here

[Team B&H]

If any of you ever ran a hydro with the customary left hand prop with a centered motor and driver on nice, calm windless conditions, you'd find the left sponson rides higher. Yep, the motor does produce torque and the prop delivers it to the water. Newton tells us that for every action there is an equal and opposite reaction so voila, the left sponson rises up! Figure out how much this torque is in foot-lbs and divide by the offset weight of driver and/or motor and it gives a pretty good number to compute the needed offset to counteract torque. See math was a useful subject.

But things don't always work out exactly. The unlimited guys did it this way and then suffered a number of blow-overs in the corners because they got lift from the right sponson deck when the boat was in a yaw in the corner and didn't have enough sponson loading to hold it down. Never saw that condition on an outboard but remember, there aren't many free lunches out there.

[Fear the Duck]

Thanks, B&H. I'll try figuring the torque range, and tailor the offset of my coaming sides to my median weight (always fluctuating, hooah Air Force), plus the weight of a helmet, jacket and cutsuit.

[Bill Huson]

I am a mathematician but too lazy to do the math - I just built an offset cockpit, and a bit of twist called "warp plane" in the bottom. Worked fine. Once R.C. Hawie insisted I center the engine with the boat rather than the offset cockpit and I did. Ran one heat and put the engine where I had i, centered on the transom of the offset cockpit.