posted 01-25- 12:52 PM               

I'm not sure if OpenPlane models this effect...

Also I guess that the airpoint on the vert. stab might matter - this will cause the rudder to apply a rotating tourque to the plane - I suppose the higher up the airPnt the more leverage the force would have...

Just some ideas... I am very curious about this...

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-Sv =FC=

WWI in SDOE!

posted 01-25- 12:56 PM               

Flight Characteristics

The first thing you notice about a Triplane is that it is definitely a "rudder" airplane and you have to keep on the pedals constantly to keep the ball in the center of the slip-skid indicator. The elevator is excellent with smooth, powerful responses at all speeds. The ailerons are somewhat heavy but I consider the roll control good. There is a large amount of adverse yaw since there is little aileron differential. If the ailerons are quickly displaced, the Triplane will yaw 20 to 300 if rudder connection is not applied.

The rudder control tends to be marginal. All turns must be coordinated and the ball really rolls around the cage during a turn. Turns are not very stable and I have to constantly work the rudder to keep them coordinated. Only a slight amount of back pressure is needed during turns, even steep ones.

At cruise speed of 90-95 mph, the Triplane is very nimble, quick and responsive. You can really move it around if you keep on the rudder.

The Triplane tends to fly tail heavy and increasing speed requires lots of forward stick to hold the nose down~ It appears as if the effective center of drag is above the thrust line so the faster you go the more elevator correction is needed to hold the nose down. This is somewhat of an explanation for the familiar "tuck" position of the Triplane at high speed. The horizontal stabilizer is rigged at a plus 90 (leading edge high) but even with this forward stick pressure is needed as speed increases. The high lift wing airfoil shape really wants to pull the plane up. All the wings are rigged at 11/20 angle of incidence.

Stalls occur at about 40-45 mph and the Triplane "mushes" down without a definite nose break. It is a little like a parachute in descending.

General visibility is excellent except for the mid-wing placement. In the traffic pattern you have to "bob" the nose up and down to keep visibility. Otherwise, the cockpit is comfortable, roomy and lots of fun to fly.

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-Sv =FC=

WWI in SDOE!

posted 01-25- 01:01 PM               

I am guessing here, but I think this means that since the ailerons move the same angle up and down there is a drag issue. Most planes give more up aileron than down - this is because up aileron has less drag than a lowered aileron. I guess this would be the "airleron differential."

So with the fokker, a right roll lowers the left flap giving more drag on the left wing than the right wing. This would cause a yaw to the left, opposit the roll, hence the "adverse yaw."

SDOE can model this if the airfoil file works like I think it does: there is a seperate chart for wing/no aileron, wing/aileron down, and wing/aileron up. We could give more drag to the down position and induce a yaw tourque on the plane. No? MH? Anyone? Am I correct about this?

posted 01-25- 02:10 PM               

I have tried to moving the airpoint 10 feet up and 10 feet back and still no roll. Do you think that I have to tie it into the ailerons? Are the other planes like that?

The following quote is from a DVII pilot.

"Cole Palen, of Old Rhinebeck Aerodrome, New York. We asked him how it flies. "Like a puff of warm air," was his graphic answer. "It'll break ground for no reason at all, without nosing up or you making any real effort. It just floats away. I would say it's very sensitive on the elevators- so many of the early machines were. And it's a rudder airplane. Give it rudder and automatically you're going to get the right angle of bank to make your turn. The ailerons are there just to keep the angle of bank where you want it."

It flies very close to this account except for the rudder.

posted 01-25- 03:16 PM               

I don't know if has anything to do with what you are seeing, but right now the airfoil used for the rudder on all planes still has the "unstallable" tweak that was in the original game. I had to leave it as-is since this airfoil is also used in all the propellers. I've seperated out the propeller airfoils for the 5.3 plane pack, if you look at the 5.3 p38 it has an example of how to replace the prop airfoils with the new ones. After this is done to all the planes I'll make the rudder and elevator airfoils stallable for 5.4

posted 01-26- 12:04 AM               

If you have the 3d model it should be pretty easy to calculate the correct aspect ratio (airAR), chord and area for the flight surfaces. AirPt coordinates should be 1/4 from the front along the wing/stab. Since it's where the force is applied it should also be midway along the surface in the other two axis.

You should also create a new copy of the airfoil for your plane so it doesn't share airfoils with another plane. This will help prevent problems with other people's airfoil changes creating problems for you. I think Zurawski did up a step-by-step on how to duplicate and rename airfoils.

posted 01-26- 12:06 AM               

I know this can be done. Just have to figure out how.

posted 01-26- 02:06 AM               

Tweaking has been to the weight, Prop radius and RPM. To get accurate speed, stall and rate of climb. I have a ton of flight data and pilot accounts to verify this. The only thing I have not been able to crack is that the plane is a "Rudder plane"

I have tried duplicating Vstab. using information from planes that do roll when rudder is applied. I have increased the size, shape, airpoint, airk, airMax. Nothing seems to change it.

posted 01-26- 03:10 AM               

Also just added this to the FAQ

Q: What does airMax do?

A: Airmax determines the range of travel for the control surface. A value of 1 is 60 degrees total travel (30 degrees each way from center). A value of 0 means no travel. A value of 0.5 would be 30 degrees or 15 degrees from center each way. You can calculate airmax from degrees by dividing by 60.

For example, if you have plane specifications that say the aileron travelled 10 degrees each way, 20 / 60 = 0.333 for an airmax value. Note that it is not possible to specify non-symmetrical travel. IE most ww2 planes had rudders that travel farther one direction than the other. This is not currently possible using airMax.

posted 01-26- 07:28 AM               

I thought this had to do with tip-stalling and washout, no? Doesn't an elipical wing need no (or less) washout?

It must do more than that though right? Because I don't think SDOE simulates a tip stall, does it?

I think to move foward we really need to better define what a "rudder plane" means. In my mind it means that the plane makes very flat turns, but still normal coord. turns. Guessing here... maybe a little roll input needs much rudder imput to keep the turn coordinated - hence a "rudder plane." So to get our planes do do this we need small amounts of roll to cause a big slip, right? So we want as much force on the plane in the direction of the roll as we can get. Would less dihedral help do this? Also any thoughts on my adverse yaw theory? Hmmmmmm...

posted 01-26- 01:54 PM               

Here is the wing information
Top Bottom vStab.
airK .6 .6 .6
airAdv. .4 .6 1
airMax .5 .6 1
airRA 5.57 5.75 8.25
airArea 77 41 9.70
airChord 5.25 4 3.48

Bold should be accurate for this aircraft. For the rest I went back to the original FokkerDr1a after making so many changes.

Air speed, climb rate, stall speed and max dive seem be be very close. Just that darn rudder.

The FokkerDr1a does not roll when you apply rudder either. Daa

Would this be easier if we just send you the .sm files to look at and test.

Thanks SV and Tailslide for all the time you have spent helping here.

posted 01-26- 08:21 PM               

Right. Since the WW1 wings I've seen are all square they should be pretty far from elliptical?

>I thought this had to do with tip-stalling
>and washout, no? Doesn't an elipical wing
>need no (or less) washout?

The spitfires had an elliptical wing. The Mk 1a had quite a lot of wing twist (thats why my 1a is so hard to drop a wing on). Later marks reduced the twist, I'm guessing because the designers realised the plane was stable with less washout although they still kept 1 degree of washout in the tips for the Mk IX.

>It must do more than that though right?
>Because I don't think SDOE simulates a tip
>stall, does it?

Why do you say it doesn't?

>small amounts of roll to cause a big slip,

I find sideslip to be very undermodelled in SDOE compared to other sims like MS:CFS. It may be because of the current vert stab airfoil which is unstallable?

TS

posted 01-26- 08:30 PM               

Raider buddy where ever would I be without your help

------------------
Zoycite {GS}
GUNSLINGERS

visit The War Paint Factory

posted 01-26- 08:56 PM               

Am I right about this: Tip stall is usually caused by the outer part of a wing stalling before the inner part of the wing. This happens because during a turn near stall speed, the outer part of the wing on the inside of the turn has less airspeed than the section of the wing nearer the root - so the outer section stalls first.

Since SDOE only models one airPoint on a given wing, one section of the wing can never stall before any other part; the entire wing's lift/drag/moment is based on ONE lift/drag/moment calculation based on ONE airspeed over the wing.

Am I forgetting something here? I do have many R/C wive's tails in my head

-Sv

posted 01-27- 12:19 AM               

Do you have the version of SDOE that you can display force vectors? Load up any of the planes and count the airPts.. you'll find at least two per wing. You can specify different incidence for each section as well to let the tips or the roots stall first.

posted 01-27- 05:40 AM               

Maybe I should update my planes so that they have two wing sections...

Yea, I gotta dig up that de-bug version with the vectors - last time I used it I couldn't do anything about the vectors, but is was pretty to watch