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F1 Milestone!

Looking good! My favorite canopy for a rocket for sure.

I'm just about to start on a 25 year old front seal myself... first thing I did was look up your Kitplanes write up from 2018.

Alex
 
Capflyer said:
Looks good Paul! Curious what your solution to the fuel pump drain clearance was.
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I ended up modifying the pump (slightly) - drilled and tapped the bottom of the pump boss to install a tiny nipple I turned on teh lathe, then plugged the back flush with an Allen-head NPT plug. If I have to replace a pump in the field, I coudl plug the back of the new one and go without a drain line to get home, then modify the new one when I get it back to base. But the truth is, I don’t know that you can change the pump with the engine in place on he F1 firewall, so you’re probably just grounded (if the pump fails) until you get a hoist anyway…..
 
If I could build an F1 at this pace, I'd start tomorrow. Nice work. And a screamin' deal on IO-540 might help too!
 
While you have your bird in this level position, put a level on the face of the crankshaft and see how plumb it is compared to the datum. I picked up about 3-4 mph on my -6 leveling up the engine to the aircraft datum line. Got that tip from John Harmon when he was racing his HRIII. I had to put some spacers under the two bottom engine mounts to get the sag out of it.
 
Aden Rich said:
While you have your bird in this level position, put a level on the face of the crankshaft and see how plumb it is compared to the datum. I picked up about 3-4 mph on my -6 leveling up the engine to the aircraft datum line. Got that tip from John Harmon when he was racing his HRIII. I had to put some spacers under the two bottom engine mounts to get the sag out of it
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Did you ask John why it wasn't level in the first place? It's there for a reason.

I'm not picking on you Aden. I just don't want to stock engine mounts that cause handling problems.... if it ain't broke don't fix it!

Ask Ai "Why are piston aircraft engine thrust lines offset down and to the left?" Let AI give you the answer.
 
He said it picked up more speed. And as you know, that heavier engines hanging out there with an extended prop, can sag a bit more than normal. I know there is offset for thrust but I did the same on my -6 and will other improvements/mods (not to the engine), I could get 220+ mph out of it at 1500 msl. John said that back in the day when people where really building lots of Rockets, people would complain about losing speed and their planes were not that much faster than a 200hp RV. Upon investigation he often found the engine sagging quite a bit and also Horz stab alignment issues. One fellow had about 17mph gains when it was corrected. So I am curious if a 6 cyl engine hangs down a bit more than we'd like.
 
vfrazier said:
Why are piston aircraft engine thrust lines offset down and to the left
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I asked Grok your question and am including the response:

Piston aircraft engine thrust lines are often offset slightly downward and to the left (from the pilot’s perspective) to counteract aerodynamic and mechanical forces that affect flight stability and control, particularly in single-engine aircraft. Here’s why:

  1. P-Factor: When an aircraft is at a high angle of attack (e.g., during takeoff or climb), the descending propeller blade (on the right side in most aircraft) produces more thrust than the ascending blade due to the angle at which it bites into the air. This creates a yawing moment to the left. Offsetting the thrust line to the left helps balance this asymmetric thrust.
  2. Torque: The engine’s rotation (typically clockwise from the pilot’s view) generates a torque reaction that tends to roll the aircraft to the left. A leftward thrust line offset partially counters this by aligning the thrust vector to reduce the rolling tendency.
  3. Spiral Slipstream: The rotating propeller creates a spiraling airflow that strikes the vertical stabilizer, pushing the tail to the right and yawing the nose left. A left-offset thrust line helps mitigate this yawing effect.
  4. Downward Offset: A slight downward tilt of the thrust line compensates for the aircraft’s tendency to pitch up during high-power settings (e.g., takeoff). This reduces the need for excessive elevator input and improves climb performance.

These offsets are small, typically a few degrees, and are designed into the engine mount or airframe to improve handling, especially during critical phases like takeoff and climb. The exact offset varies by aircraft design and engine-propeller combination, as manufacturers fine-tune for optimal performance and stability.
 
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