Prop thrust gain per inch?

Static thrust for the actual operation is important only when taxiing for takeoff site.
For a real airplane in the first place is important aerodynamic efficiency of the propeller, its ability to maintain traction in all flight modes.
Hungarian pilots recently installed some new saber propeller diameter of 1600 mm (63 ") on their trikes with engines Rotax-503 (2.58).
They were 2-bladed wooden propeller.
Thrust increased from 125 kg to 159 kg.
American pilot went even simpler: it dismantled three straight blades of the hub and set new saber with the same diameter 63 "
Increasing the thrust due to the replacement of the blades was 25 kg
Engine - Rotax-503 (2.58).
Thus all observed pilots better retention in flight thrust.
Scimitar-shaped blades are more expensive, more difficult to manufacture.
But this is the case when a new blade is equivalent to setting a more powerful engine.
 

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Thanks Bill,
I appreciate your input. My prop diameter is constrained to 60-62" without modifications to the airframe. I'm trying to figure out if an airframe mod is worth it for the amount of thrust gained. I understand that it's not just about thrust, I'm trying to learn a bit more about the subject.

I haven't followed or read much of the postings in this thread, What engine and prop do you have now and what are you thinking of changing to?

If you are going from a 582 with a 60 inch warp to a 582 with a 72 inch warp, you will really mainly see a better rate of climb, with no real significant change in cruise or top speed.

A 582 with a 60 inch warp drive requires about the most pitch out of the prop as you can go without having " too much " pitch... ie... getting to the point where the blades are slightly stalled until you reach a certain airspeed.
 
Thrust increased from 125 kg to 159 kg.
American pilot went even simpler: it dismantled three straight blades of the hub and set new saber with the same diameter 63 "
Increasing the thrust due to the replacement of the blades was 25 kg
Engine - Rotax-503 (2.58).
How did they measured the thrusts during flight ?
With diameter 63" and 52 HP, Maximum theoretical efficiency is 0.7 at 50mph.
According NACA tests, classic propeller gives at best only 0.63, because the loss by friction on blades and rotation of wash.
This gives a thrust of 110 kg.
If extra 25 kg, then his efficiency would be 0.77
Probably magic propeller !
 
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I have a question? I had airboats and read all the discussions on props also i am a retired agpilot with about quesstimated 30,000 hours, does prop width have an effect on thrust or push in airboat terms, i noticed that the 72 inch props had a bad effect on thrust lines, i am trying to get the materials to start building a gyro using the geometro engine and maybe making a prop based on what airboats use (wide blade wood prop) maybe around 60 inch diameter, the air speeds are some what similar to an airboat, just pondering thanks
 
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Propellers are a very complex subject Dan.



In my opinion it is unlikely you will get as much static thrust from a 60 inch propeller as you would from a 72 inch propeller turning at the correct speed.



Thrust lines are simple; arrange things so the variable loads are near the center of gravity and the thrust line passes through it.



The gyroplane I fly most of the time (The Predator) has a 68 inch three blade propeller made specifically for the application by Craig Catto and she is very near centerline thrust.



If I were looking for the best propeller for a specific frontal area, horsepower and speed range I would either copy someone with a similar application or go to someone like Craig to work through the numbers.
 

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Complicated nawwww! I went from fixed pitch pawnees to 1300 hp AT-602 five blades props designed for kingairs, i did see and experimental 4 blade with wide blades and the figures were outstanding, i guess what i am saying is that a prop designed with over 200 knots in mind isnt what would be ideal hauling 630 gallons off a half mile strip i come to the conclusion that mission parameters is what one designs for, being on fixed income i have to now use my head instead of my pocket book, i am looking at starting a hornet but your limited to certain engines, i have plans for a parson 2 on which i have seen everything from 582 rotax to mazda rotory to lyc 0-320 i am thinking the just overhauled 1.3 geo tracker i have maybe just the ticket with redrive of course, anyway my mission is being able to pullit out of carport taxi to the field next to house and takeoff, saving hanger or storage costs, us crpdusters are an outlaw bunch.
 
My 230 HP Subaru has a 5 bladed warpdrive prop,I went to 5 blades because I ran out of pitch on the 4 blades

the extra blade did the job,I am now pitched for 5,100 rpm on takeoff.
 
The complexity was beyond me, so when pitching the prop on the Hornet, we had the 503 DC DI with the B box and a 62’’ inch 3 blade Warp (the guy at Warp advised we could go to 63’ with the 503 but said an inch less would be better), we tied it down and then began pitching the prop to give us 6500rpm with WOT.

This it was said would then be around 6800 RPM/redline in the air in cruise. Then did a thrust test and got 319lbs. This was not bad when we had only five galls, but when I topped of with ten at Zephyr Hills in the summer then gave a very anaemic performance. Then again our machine was heavy at 330lbs and me at 200lbs.

I regret to say that I am very happy with a spreadsheet or tables that work it all out, and grappling with math was never my particular turn on, being far happier sitting fat dumb and happy with a stick and peddles to play with.
 
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Post #37
Vance:
The propeller can’t blow well if it doesn’t suck well.

Vance, are you saying that: When someone is blowing up my tailpipe - they are really a big sucker?
 
Gyro28866;n1122649 said:
Post #37
Vance:


Vance, are you saying that: When someone is blowing up my tailpipe - they are really a big sucker?

No David, I was writing about propellers.
 
Dan R;n1122590 said:
I have a question? I had airboats and read all the discussions on props also i am a retired agpilot with about quesstimated 30,000 hours, does prop width have an effect on thrust or push in airboat terms, i noticed that the 72 inch props had a bad effect on thrust lines, i am trying to get the materials to start building a gyro using the geometro engine and maybe making a prop based on what airboats use (wide blade wood prop) maybe around 60 inch diameter, the air speeds are some what similar to an airboat, just pondering thanks

Wide chord props end up causing drag when power is pulled in flight. Several accidents / mishaps have been blamed on wide props. Airboat is NOT a gyro.
 
So a 72 inch three blade prop has less drag than a 60 wide two blade prop both are spinning disks i will experiment this by hanging a board equaling each type of blade out my truck window and measure the differance, i remember cessna agtrucks on some models had a shorter blade we thought wow we gotta have the long blade version it came down to very little difference in take off and carrying a load but we did notice with the long blade prop cruise speed dropped off and noise levels were ear splitting.
 
Jean Claude;n902220 said:
How did they measured the thrusts during flight ?
With diameter 63" and 52 HP, Maximum theoretical efficiency is 0.7 at 50mph.
According NACA tests, classic propeller gives at best only 0.63, because the loss by friction on blades and rotation of wash.
This gives a thrust of 110 kg.
If extra 25 kg, then his efficiency would be 0.77
Probably magic propeller !

It was a static pull.
Yes, of course - this is a magical propeller.
 

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Jean Claude;n902220 said:
How did they measured the thrusts during flight ?
With diameter 63" and 52 HP, Maximum theoretical efficiency is 0.7 at 50mph.
According NACA tests, classic propeller gives at best only 0.63, because the loss by friction on blades and rotation of wash.
This gives a thrust of 110 kg.
If extra 25 kg, then his efficiency would be 0.77
Probably magic propeller !

Just for the record... This paper describes a clever method of deriving, among other things, the real efficiency of a propeller when working on a light airplane. For the single-engine 'Luscombe' the figure is 0.62

​​​​​​https://engineering.purdue.edu/~andr...-46372-872.pdf
 
70 " 3 blade IVO Magnum on 2.5 Subaru.......Thrust numbers to follow....

From neutral position I have reduced pitch 3 full turns out of a possible 6.5 to obtain 5250 motor rpms.
 

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