It has been said by many that the 4s does not need a shorter nose moment to turn tight. The heavy weight of the motor does not seem to effect the turn rate. The larger the diameter does not seem to effect the turn rate either.
Windy said this in his video but had no explanation why. Dirt touches on it in his article but leaves you with something like, it is pretty easy to figure out what is going on here so the extra nose weight doesn’t effect the model. Please go a little further than that. Throw a dog a bone here. I was reading the whole article wanting to find out why this happens and it was touched but not put out there in black and white enough for me to “get it”
As far as I have seen Brad Walker is the only one who actually tried to put it on paper why this happens. He is thinking that since there is only one pulse on the prop every other revolution then the plane can finish the turn easier, or something like that.
It is a given that I am not the sharpest tool in the shed but let me see if I got this right. The 4s engine we use is a very docile motor at best. When 4s engines are docile or down on power to size ratio or setup in with a smallish cam the HP curve and the Torque curve happen at opposite ends of the rpm range. This was why the Honda Vtec engine was supposed to be a marvel in the engine building world. The oil filled camshafts would adjust valve lift during the rpm range to get the torque curve and the hp curve together at last. It works so well they put 32 different patents on it. Our little 4s engines are docile meaning the maximum torque happens way early in the rpm range and we are flying on the negative torque curve where it is flat and the prop is receiving the same torque at all times no matter where the nose is pointed. Does this explain why it does not effect the plane with the extra weight up front and the large props???????
This would also explain why Paul said he could fly 4.8 laps and have a fine looking pattern. The plane is hauling a** and as the nose is pointed up the rpm goes up(away from the torque curve) and torque goes down. This creates that usable maneuver speed. The 56 that Paul is using is much less of a motor compared to the 72 Brad has been using. The 72 lap times are much more in correlation with maneuver speed. The 72 must have more torque on its negative curve. We dabbled with the 56 and got the same type of reaction Paul was getting fast then slower but usable. We never really got it working well but that was due to many other factors(fuel and tank and stuff). Once the 72 was fitted with the Pat Johnston manifold it has been pretty much unstoppable. The 72 however likes a lot of NITRO. It needs nitro to get good runs. The 56 seems to be a different story. These motors are going to be fun but there is not going to be one philosophy that works for 4s setup. The motors and their size will dictate what fuel you run. There is only one certain thing so far. THEY WILL NOT RUN GOOD ON UNIFLOW IF THEY EVEN RUN AT ALL!!!!!
One of the coolest things about it is in Brads current setup you just needle it for max RPM and go. No guess work. He has four or five different props and he can tell you the exact speed of each one. Prop A 5.2 lap, put it on and put it to the watch and bingo 5.2 laps, prop B might be 5.4 lap and so on. By the way these are all props from Local hobby shop with just a little sanding work. It is pretty much clockwork now for him to get excellent runs over and over and over.
Dirt please explain why the larger diameter and the heavy nose doesn’t effect the corner like it does on a 2s. You touched on it but didn’t go into to detail.
DMoon