I have a engine that turns a
menz 22x10 at 6800
mejzlic 22x8 at 7600
does anyone know roughly how much static thrust I can expect, I need to know if the ship will have good verticle

Darin

Download yourself the Thrust HP calculator (FREE) from:

http://freespace.virgin.net/barry.hobson/

BTW - the answer for the first prop is about 32 lb and the second is about 39 lb.

The chart is optimistic
18-6 Mejzliz at 9000..chart 25, spring scale on the tailwheel, 17.5
18-6 wood, maybe Zinger,( it was painted) 7800 rpm, 18+ on a spring scale..

See what I mean about prop load and thrust, Darin? If my MA wood 20x8 turned as fast as you're getting on the 22x8, then I would be more pleased. My motor only has about 16 oz of gas through it so, I hope the numbers improve.

The charts are good late night reading - other than that - good for starting a fire - if printed out.
A quality scale -up to 50 lbs - is far more meaningful .
A MenzS 26x12 -at 6000 rpm - shows about 35 lbs of thrust here.
the chart?

46.56

Thrust Calcs give out absolutely meaningless data. They do not take into account all the dynamics necessary to even give an approximation. I used a fish scale like Dick H. suggested and got totally different figures. While not scientiffic, they proved to be alot more realistic than what I was getting off those thrust calcs. If you do this test, try to do it on a smooth flat surface such as concrete or asphalt as the resistence to rolling that grass gives, will affect the results.

The test we use for static thrust -goes like this.
The helper stands over the rear of the plane - -holding the force along the root of the stabs.- wuth his legs.
A line is hooked to the rear of the model -and to the scale .
pick a solid location.
I hold the scale aligned with the attached line.
Then the engine is advanced to full throttle -and I pull on the scale , till the model is backed slightly away from the holders' legs.
A few trials will tell you if the setup is aligned, as the readings will all repeat.
This also insures that the plane does not scoot away -if the line or scale fails.
Don't be surprised if the actual thrust is nothing like the friggen chart suggests.

Could this fish scale thrust test be incorperated into a test bench? I have an engine coming that I plane on running in and possibly burning it's first few gallons through and it might be great to get some real time data like this. I can think of at least one way to do this. Hmmmmm. Anyone?

Joe

the test tells you nothing --except for comparative rpm data - under a static condition.
It is of little value in determining how various models will fly -
the reason?
each model has it's best flying speeds--
a given prop may OR may not be most efficient in that speed range.
Each engine design works best at a particular rpm - - change the muffler - you may change that efficiency range.

Probably the most useless info available to modelers as it supposes that it has data close to real world use.
So unless you use the thrust test --to find which prop pulls best at ZERO airspeed -- you learn little from it.

For what it is worth - the largest diameter and least pitch - will produce most thrust --at zero airspeed.
this setup is also - typically-- no good for flight performance.

I am deciding between 2 motors and dont want to mount two different engines to get actual thrust, I would like to get a good thrust readings before I comite to this engine, otherwise I will go for the biggen.when I get the thing going I will post actual thrust at all rpms so others can know what to expect I wish there was actual thrust #s out there I will run both props and post some #s on tues.

Darin