AH64 Apache (450 size) build thread

[therick04pp]

Originally Posted by Keyrigger

Impressive. You should have no lack of thrust now. I would not be surprised if you might even have a bit too much so I would start with a slightly smaller set of blades and see how they react. As an example, I had a system on an F3C heli that used two blades on the tail under normal circumstances. I tried to get that helicopter to first work with very low rpm as a trainer and even with 120mm tail blades, they were overwhelmed by the torque of the 810mm blades. I got a three blade tail rotor system, installed three 120mm blades, and lack of authority was no longer an issue..

Fast forward to the next version of the machine which had normal head speeds for F3C and now the triple tail blades were too much. I cut their size down to 110mm and things in the tail control department were back to normal. Now insert big smoking hole in the ground.

The next version of the system along with a whole new helicopter was 806mm blades plus the included triple blade tail with 115's. That was a very nice setup and was evenly balanced. The main blades were not really suited to F3C so off they came and a smaller set of F3C capable 760's were installed. Well, the tail had a bit too much thrust so it was back to getting smaller blades. I now have a set of 105mm blades and they are a good match for the system.

My own experience is that if you have tail gain settings much lower than 40 to keep a tail in place, you most likely have too much blade. Flight testing will have the last say but that is what I have found to work for me. I actually had very high gains when I had it setup for the hovering maneuvers to really lock in the tail. I wouldn't dare run that helicopter with those gains while in fast forward flight.

What we are missing here is the motor and gearing you are using for the main rotor. That can help fill in the blanks. I also have a four blade head on an Agusta A109 but am using two 61mm blades. It works well. Keep up the nice work.

Don

Thanks for the reply Don! I appreciate the info. Im running a Scorpion 2221-12 motor on 4s, with an 11 tooth pinion, also 61mm tail blades. You think those will be too large?

Previously with 65mm, I could get it airborne, but ANY pitch up or down, and the tail would swing bad. Almost lost it twice, no amount of gain would get rid of it. I didn;t dare try to get it into IU1 or 2.

[Keyrigger]

There is a good chance that you may find the thrust too much with four 61mm blades. Here is the difference in our two systems. I use the same motor on three cells, a 13t pinion, and four 305mm Rotor Tech blades. I ditched the plastic blades made by the same company as your BURP blades as they beat the air great but provided very little lift and performance was never that good. I need to replace the KBDD tails with better profiled CF blades but it is not high on the "List of To Do's". It has been along time since I flew it but I need to get my three 450's out and blow the dust off of them. You know the funny part is that if you had run it in Idle 1, it might have performed a bit better as the thrust level might have been raised enough to counter the torque. Take care.

Don

[therick04pp]

Thanks again Don. I'll for sure take it slow and see how it goes. I finally buttoned up the fuse today with some weathering. Rust/dirt and some soot around the engine and where the exhaust exits near the tail. Super hard to capture on camera but looks good. Also rubber painted the interior of the canopy glass. Only thing left is to mate them up. Once im finished getting the airframe dialed in, ill post back.

Originally Posted by Keyrigger

There is a good chance that you may find the thrust too much with four 61mm blades. Here is the difference in our two systems. I use the same motor on three cells, a 13t pinion, and four 305mm Rotor Tech blades. I ditched the plastic blades made by the same company as your BURP blades as they beat the air great but provided very little lift and performance was never that good. I need to replace the KBDD tails with better profiled CF blades but it is not high on the "List of To Do's". It has been along time since I flew it but I need to get my three 450's out and blow the dust off of them. You know the funny part is that if you had run it in Idle 1, it might have performed a bit better as the thrust level might have been raised enough to counter the torque. Take care.

Don