I have some numbers for the crunchers

[Bob Gregory]

I have some numbers for the crunchers

Bob, this will not answer your question about flat plates.
This is to show the conservative lift values of D Riley's measured
results of a 0012 airfoil.
D Riley's data is 58 percent of the flat plate and 20 percent of
the HS_liftcalc airfoil. I placed his at -4 degrees and theirs
is unknown. So his figures are very conservative for a 0012
airfoil of their unknown airfoil. D Riley's foil would have be
set in the seven degree negative vain to be consistent with
the HS_liftcalc foil figures. This would add drag to
counteract the propeller PPO force and add pounds for
the rotor to lift. I think I would limit the stabilizer to minus
three degrees and add area to balance.
If I was to build a stabilizer it would be an upside down airfoil
for maximum down force with the least material. Dick Degraw,
I believe, used an upside down foil on one side of the
stabilizer for torque roll control on the Gyrhino.
There are four to six places to "What If?" The D Riley area
uses his data and the other four use the air density chart.

 

[Bob]

Bob Gregory:
Ahhh ! You did alot of fiddleing I see !
and I can see where this can get out of hand quickly heheheh

So I have one more question....
is the .04 coefecient of lift valid at -3 degrees of HS AOA ?
it doesn't sound like it , sounds like that .04 is for a very steep pitch angle if thats the case then almost ALL HS's out there are not angled enough to give the needed downward force !
includeing mine !
I used the .04 coefecient of lift when I used the calculator
but didn't realise that the angle of attack was part of that figure... now that I realise that what can I do ? because at most right now the HS on my gyro is setting at -1 degree
( I have it shimmed up from -3 degrees so its easy to get it back to -3)
but if that flat plate coefecient of lift is counting on the angle being -7degrees its so far out its unuseable !
....

It looks as if Dougs Chart is also unuseable because of the high AOA, I don't think there is a gyro on the planet that uses -7 AOA for the HS, but I may well be wrong there. <grin>
as You mentioned -3 to -4 is the most common although there are many with the HS set at 0 degrees and rely on the airfoil shape to do the downward force.
If I knew where to look up the figures we need I would
a flat plate at -3 degrees in a 90mph flow of air should produce
a downward force but I have no idea how much.
....
Ok consider My HS now ....
it is 31" long 19"wide on each side of the VS with a triangle cut out for the rudder on each side that both togather equil about 1/2 sqr ft. so its an Honnest 7.5sqr ft in airea
yes ...its BIG !.... it is a flat plate however, a sheet of plywood
that is supported by metal bar stock to make it ridgid.
if I put my HS into the calculator along with the same air speed and thrust figures and distance... I still don't know what the calculator is giveing it as an AOA..... thats the problem
and to be honnest if its more than -4 degrees I ain't going to move the HS that far.hehehehe
any sujestions ?

thanks for your Hard work Bob thats a great addition to the HS lift Calc files !
...
Bob.....

 

[Bob]

Bob...
I just got done playing around with the Excell program and I discovered a few more things that you did, makes more sense now!
and I do think the .04 coefecient of lift for the HS is reasonable for a flat plate, because that is lower than even 1 degree on Doug's chart for the 0012 air foil.
( though I'ed like to know what angle its realy at ! hehehe)
I changed the figures to match my gyro and was happy to see that it still falls within safe paramators,luckily the distance to the COG is longer on my craft (5ft) and the offset is 2"
and probly the thrust is lower but I didn't change that figure
and it still said I had 58% leeway so I'm happy !
....
it takes a while to figure out what you were doing on that thing but once you figure it out its easy to see ! HAHAHAHA!
thank you very much !
I bet it helps alot of people in the future !
Good man !

Bob......

 

[dragonflyerthom]

Bob

You can glue up some high density foam on to the bottom of your flat plywood, then cut some aerodynamic ends to glue onto the ends of your HS. Then take a hot wire and form the upside down HS. This will give you the airfoil that you are looking for. It is cheap. Then you can go to the hobby shop and get plastic tape. Put this on. This will be your underlayment. Put a thin application of glass cloth, Your mixture and hardener to wet the glass cloth and you will have a very neat and finished HS with the form you are looking for. It won't add a lot of weight either. It is not as expensive as going out and buying one off the shelf. Good luck

 

[Bob Gregory]

Bob, read this about the Gurney Flap. Inexpensive and
supposedly a break through at the time.

http://www.allamericanracers.com/gurney_flap.html

 

[Bob]

Thanks for the Sujestions Thom !
Problem is the Plywood itself is so blasted heavy that its way too heavy NOW the way it is.!
I have cut out of strafome ( the white stuff used for packing)
a "T" tail and HS for it altrady, the plan is to cover the Foam with heavy tinfoil ( to keep the fiberglass off the foam) and then lay a few layers of fiberglass cloth over it ...
but I havn't gotten around to that yet as its still winter-time here !
I figure with the Foam and glass "T" Tail I will LOOSE 30lbs
off the weight of the gyro, so it will make me UL Legal again !
obviously the way to go !
.....
Very interesting information there Bob Gregory!
the Gurney Flap is nothing but a hunk of angle alum put on the trailing edge of the airfoil but gives a substantial increase of
downforce when used on racecars... I amagon it increases drag by a great deal as well, but if a person is lacking the downforce they need it might be the answer to their problem.
calculateing it in to how much though is more guess work I think... but it might be an alternitive !
thanks guys for the info and sujestions !
...
Bob.......

 

[Bob Gregory]

Check out this site for flat plate, airfoil, and eclipse.
It is interactive for checking speeds, degrees, etc.

http://www.auf.asn.au/FoilSim/FoilSim.html

All use pounds per square foot
50mph 90mph 50mph 90mph 50mph 90mph 50mph 90mph
0.5deg 0.5deg 1 deg 1 deg 2 deg 2 deg 4 deg 4 deg

.340 1.101 .680 2.203 1.359 4.406 2.718 8.807 Flat plate Sim

.378 1.226 .756 2.452 1.513 4.903 3.024 9.800 Foil 0012 Sim

.183 .592 .366 1.185 .731 2.370 1.463 4.739 Foil 0012 D Riley

Looks like the HS_calc-2.xlr is using about 3.7 degrees at 2.48 and 8.05 pounds flat plate
when HS is compared to the SimFoil format. I see the airfoils have an edge compared to
the flat plate. At our speeds there is not much difference for the work involved.

 

[Bob]

COOL thanks Bob !
and thank you for posting the numbers as my brouser doesn't like that site at all (java turned off!)
so it looks like its 2.718 pounds per sqrft. at 50mph for 4 degrees for a flat plate.
...very interesting about the 3.7 degrees of HS-Calc-2.xlr
I suppose I should add about 1 degree more to my HS's angle
to have it the same as the calculations
....
I want to thank you Very Very Much Sir for your help !
for 5 years now I have been after the numbers here and I realy appreaciate it a big bunch !
....
THANK YOU !

Bob.....

 

[Bob]

OK let me try this the hard way....
at 50mph
7.5sqrft HS
-4 degrees AOA of HS
5ft behind the com
2.718 lbs per sqr ft

(2.718x7.5)=20.385
(20.385x5)=101.925 ftlbs of torque on the frame from HS.
.....
Engine thrust 300lbs ( seams high to me)
offset 2"
(2x300)-600 inchpounds of torque /12 = 50ftlbs of torque
....
end results are ,
(101.925-50)= 51.925 pounds of torque left over from the HS as extra safty margin.
....

Did I do that right ?

Thanks !

Bob.......

P.S. I realise 50mph accross the HS is just above idle for the engine.

 

[Bob Gregory]

Bob, yes that is the result I have using the sheet. The Foil Sim file has the airfoil over the flat plate 9 percent better. Might be 5 mph faster at 50. I doubled D Riley's chart and that came out 53 % more so we are in the realm.
Try this sheet. It shows according to Cierva that the stab is slightly too small for the damping that is needed.

 

[Bob]

Cool thank You !
its not as dificult to figure out as I thought it was !
as my method above used 6th grade math ! hehehehehe
....
getting all this info in One file where anyone can calculate the needed size and placement of the HS is going to help alot of people !

Fantastic Work Bob Gregory ! thank you !

Bob.....

 

[Bob Gregory]

Sending an update of the StabCalc file. You can set the negative degree for the stabilizer for in the propeller flow or position it below (on the keel).
You can vary the area of the stabilizer and relocate the propeller offset.

 

[Bob Gregory]

I am sorry but the prior post #32 with the StabCalc02.xls needs to be doctored.

Remove the top 46 rows because that is the prior file.

I had to do it this way to get it into an acceptable format for this thread.

Thank you.

 

[Bob]

humm, I'm workin on it ! heheheheheh
...
Ok, on another thred Doug Riley mentioned that having the fruntal airea of the gyro for drag purposes, is a good idea and I totally agree.... because even the tire has a frontal airea and lever arm to the COG.... add them all up and you have alot of ADDITIONAL PPO force ! ... then you can see why that big margen for error is so nessarry! <grin>
....
going to be a busy day today so I best get after it !
Catcha later !
and thanks again Bob. !

....
Bob.....

 

[Bob Gregory]

Here is a spreadsheet for stabilizers. Find size, incidence, and calculate for drag.

 

[Bob]

Ahhh ! I see your point on the ballanceing out !
however on some gyros like mine for instance they have long legs
and the wheels at the end of them which would add more force to the PPO force in that case the amount should be added to the total PPO force that the engine and prop devolips, THEN calculate and see if you have enough from the HS at that point in time!
....
Very good Sir !
thank you !
...
Bob.......