Max static RPM

I’m thinking about a new prop and and curious what some of you are getting for max static RPM. 160hp, I’m getting 2400 ish, maybe 2410 or so. Borer 82/44. Trying to decide whether the Catto (when/if it gets certified) or the Sensenitch is going to be worth the $$. There’s a pretty big weight difference, 16# on the Sensenitch, not sure on the Catto. Currently @2450RPM I’m getting a true AS of 90mph. Other Borers, what are you getting and is there anyone out there with the Sensenitch? We know no one is running a Catto yet.. Thoughts?

ross d said:

I’m thinking about a new prop and and curious what some of you are getting for max static RPM. 160hp, I’m getting 2400 ish, maybe 2410 or so. Borer 82/44. Trying to decide whether the Catto (when/if it gets certified) or the Sensenitch is going to be worth the $$. There’s a pretty big weight difference, 16# on the Sensenitch, not sure on the Catto. Currently @2450RPM I’m getting a true AS of 90mph. Other Borers, what are you getting and is there anyone out there with the Sensenitch? We know no one is running a Catto yet.. Thoughts?

Click to expand...

First question you should ask: What are the LEGAL static limits for your engine? Those are in your TC


MTV

Talk to the folks at Catto, they’re very helpfull.
thinking 2475 static if I recall for Catto.
Completely different animal than Borer.
I’ve heard of folks running Catto 82/39 on a strong O320,
Borer - 82/44 with 2550 static.
With roughly same cruise/climb numbers.

Is that max static in the hot, humid south Texas air? I will be interested to see what the Sensenich wood prop does on a 150 and 160 how but have a sneeking suspicion it is going have a bit less pull than the Borer with less weight on the nose.

Yep! It was about 82*f when I checked. I’ll be interested to hear how both props perform. Right now I think switching is just an expensive way to lose 16#. I’m thinking the Catto is going to have the most promise.

Yes the TC usually give both min. & max. for each propeller/pitch. I assume a STC will do the same. These will be at standard conditions.

It's important as problematic static will suggest a sick engine. I always check static as I add takeoff power unless its a poor surface(gravel).

I recently installed a new(old run out) IO360 in my Acroduster 2 with a Sen. 76EM X 60. I was looking for better performance than the IO360/160 I took off. If not enough on 180 hp my plan was to part out the airplane. If good enough I would rebuild the engine.

I took the static values from the Pitts S1S TC. I should have gotten at least 2250 RPM and was only getting 2025. After checking everything else I decided to take the engine apart so I drained the oil and pulled the suction screen. The suction screen was FULL of non magnetic material, I figured maybe Al-piston pin plugs? I knew what it was after I pulled the first jug and noticed the rod was moving at least 1/16" on the crank. The material in the screen was bearing material. The other rods were the same. Only a shell of the bearing was left. Time for rebuild of maybe sell a pile of engine parts.

Just an object lesson to pay attention to static rpm. It should not be subjective. A good engine will turn a certain rpm. If expermental like me find a TCDS for the same engine/propeller.

I understand that your question knowing you have a healthy engine is rather more subjective. You want to know if a certain propeller will be better and/or lighter? But the absolute figures(as others already suggester) are or should be out there.

Me, I look for rated power/rpm at Vy. If you must clear tall trees maybe look for rated rpm at Vx. Either will translate into correct static RPM.

FWIW my IO360 with Sen. 74DM X 58 was not quite there, would turn 2600 rpm at 90 IAS(Vy) with static around 2400 rpm. A 74X56 would have been better. Indeed my old Pitts/150 ponies would turn 2700 at 100 IAS. I never saw what static was, the brakes wouldn't hold it and too $%%$% busy to look.:lol:

Jack

Steve Pierce said:

Is that max static in the hot, humid south Texas air?

Click to expand...

Now you got me to thinking. ( well at least trying)
Does it matter.
Hot air is thinner so the prop will turn easier but you won't have the power to turn it faster.
Another one of the many tests I've never done.

S2D said:

Now you got me to thinking. ( well at least trying)
Does it matter.
Hot air is thinner so the prop will turn easier but you won't have the power to turn it faster.
Another one of the many tests I've never done.

Click to expand...

Our RV-4 has higher static RPM in thin/hot air, in spite of the lowered horse power. At low density altitudes it gets off better, but the prop is turning slower.