Horizontal Stabs

[Harry_S.]

Am starting a new thread for Horizontal Stabs.

I believe there is a *lot* of theory floating around on the need and function of such stabs.

I will try to start this off with a quote from Paul Bruty from the RAF Forum.


Originally Posted by Aussie_Paul
Wow!! that is some stab and vertical fin set up. From my Raf experiences IMHO it will eliminate the "doors on" yaw instability, BUT may cause insufficient rudder authority.

Also, IMHO, that stab will need some negative AoA, as it appears to me from the pic to be to be neutral. With an un modified thrust off set Raf, the stab HAS to be at least 3 degrees (depending on stab size) neg AoA to the keel.

Aussie Paul.



WOW...I transfered a quote!! I'm learnin' how to do stuff on the forum...slow, but I'm learnin'.

Paul, I will try to look up a post I made describing my first flight with the addition of the KJ stab. I don't recall where I posted it...it was not on the RAF thread.

Anyway...the crux of the thing is that with 1 and 3/4* NEG. incidence, the machine was practically uncontrollable. By that I mean, with normal power and full forward stick...she continued to climb, aggressively.

After re-installation, and at Zero incidence, she flew beautifully.

I'll try to find that post.


Cheers :)

[dragonflyerthom]

Harry

You must remember that the H/S is to keep the fuselage on a straight flight. Its purpose is to keep it from oscillating. Any incidence is to be done when trimming the A/C.


Thom

[Aussie_Paul]

Am starting a new thread for Horizontal Stabs.

WOW...I transfered a quote!! I'm learnin' how to do stuff on the forum...slow, but I'm learnin'. Well done Harry

Paul, I will try to look up a post I made describing my first flight with the addition of the KJ stab. I don't recall where I posted it...it was not on the RAF thread.

Anyway...the crux of the thing is that with 1 and 3/4* NEG. incidence, the machine was practically uncontrollable. By that I mean, with normal power and full forward stick...she continued to climb, aggressively.I am afraid that does not make sense Harry. That coul;d have been something to do with the CofG change with Kens quite heavy stab.??

After re-installation, and at Zero incidence, she flew beautifully.

I'll try to find that post.

Cheers :)

Harry, I meant to add that these findings of mine are with the mast in position 4 so that the keel is as close to level in s/l flight. With the seight of that AC stab arrangement way out the back I reckon position 4 wouild have the keel level when dual and at 70 mph. A stock Raf in position 4 still flys with the keel 3 degrees nose down in position 4 dual and at 70 mph. This allows the broad frontal windscreen area to keep pushing the nose down the faster you go.

FWIW I like to have to front point of the cabin a little higher so that there is more air going under the cabin, and a suitably sized and efficient stab to produce the amount of down force on the stab as is occuring on the cabin as speed in increases.

Remember that Kens stab was a flat plate variety and so would perform slightly less efficiently than an aerodynamically shaped stab and probably at a slightly diferent AoA.

Aussie Paul.:)

[Harry_S.]

I have not had time to locate the post yet.

When I do locate it and post it, I will counter all theories put forth.

After all, I installed it and I test flew it. Twice.


Cheers :)

[dragonflyerthom]

Harry S.
I have started to run my engine in on my RAF. I put the prop on and started it. I did chain it to the back wall of my carport so that it would not get away from me. Boy was I surprised when it moved 6". The thrust of the prop was great and the horizontal stab lifted the back section of the gyro up about 7 inches. It held this attitude until I lowered the gas and engine rpm. It could have been the thrust of the prop also. I'm thinking it was both, I was standing outside the cabin when all of this was taking place. Now let me get to my question Harry. What is your idle rpm ? Since you have the same setup I have. I thought you would know. When I let the rpm go to 1200 or so I have a sound . As soon as it goes above 1200 it goes away. It doesn't want to idle below 1200. Do you have this same problem? I have my H/S at 0 degree of incidents and it is back about 8 or 9 inches behind the original Keel end.

Thanks Harry

Thom

[dragonflyerthom]

Harry are there??


Thom

[Harry_S.]

Harry S.
I have started to run my engine in on my RAF. I put the prop on and started it. I did chain it to the back wall of my carport so that it would not get away from me. Boy was I surprised when it moved 6". The thrust of the prop was great and the horizontal stab lifted the back section of the gyro up about 7 inches. It held this attitude until I lowered the gas and engine rpm. It could have been the thrust of the prop also. I'm thinking it was both, I was standing outside the cabin when all of this was taking place. Now let me get to my question Harry. What is your idle rpm ? Since you have the same setup I have. I thought you would know. When I let the rpm go to 1200 or so I have a sound . As soon as it goes above 1200 it goes away. It doesn't want to idle below 1200. Do you have this same problem? I have my H/S at 0 degree of incidents and it is back about 8 or 9 inches behind the original Keel end.

Thanks Harry

Thom



Yeah, I'm here, Thom. Was typing for somethin' else and I'm not the fastest two finger typist around.:cool:

IMO Thom, I wouldn't worry right now about your idling rpm...in fact I would not let it idle at all for the first 20 hrs. of breakin. Don't let it overspeed either.

All the while here...watch your coolant temp...between 190 and 200 is good.
Block off the radiator some, if you have to.

This is the way I broke my engine in. Set the prop pitch 13-15*. Set your timing about 18*. Start her up and let it run between 2000 and 2500 for about 5 hrs. Up and down between 2 and 5.

Then run between 2000 and 3000 for about 5 hrs. Up and down.

Then run between 2000 and 3500 for about 5 hrs. Up and down.

Then run betwwen 2000 and 4000 for about 5 hrs. Up and down.

Just make certain that nobody gets close to your machine when it's running. I would set the throttle at say 2800 rpm and go do something for 10-15 min. come back and run the throttle up and down a few times, then set it at 3200 rpm and take another break. Always within earshot of the engine sound.

If you have the tail tied down, I would also use wheel chocks. Safety first.:)

That engine and prop will sound real cool purrin' away at 3000 rpm.:D


Cheers :)

[dragonflyerthom]

Thanks Harry

Thom

[Harry_S.]

When I let the rpm go to 1200 or so I have a sound . As soon as it goes above 1200 it goes away. It doesn't want to idle below 1200. Do you have this same problem? I have my H/S at 0 degree of incidents and it is back about 8 or 9 inches behind the original Keel end.




Thom;

As in my other post...when you start your engine go immediately to 2000 rpm and let it warm up there...nothing lower. Believe me, I really baby my engine, am close to 500 hrs...and the only time I let my engine idle is when I return from a flight or if not flying, only after it is thoroughly warmed up...like before changing the oil or check compression.

Would you post some pics of your machine eg, the horizontal, tail feathers etc.

I'm not qualified to answer your questions on the extended keel, the AC or Parham stab. Some of the other guys should come in here and give you some hints.:D From what I gather tho, a degree or two of NEG incidence, would be a good starting point?!


Cheers :)

[KenSandyEggo]

"Safety first." says Harry.

Then Harry also says: "I would set the throttle at say 2800 rpm and go do something for 10-15 min. come back and run the throttle up and down a few times, then set it at 3200 rpm and take another break. Always within earshot of the engine sound."

Harry, can I assume that there is no one in the area where you did that? No pre-schools or nursing homes with kids and foggy oldsters wandering around? How about dumb pilots or airport rats? :eek: If I did that at my old airport in San Diego, I'd probably still be in jail. Please tell us that you're in the middle of nowhere. "Within earshot" could be hundreds of feet away. Soothe my nerves, Harry.:D

[Harry_S.]

"Safety first." says Harry.

Then Harry also says: "I would set the throttle at say 2800 rpm and go do something for 10-15 min. come back and run the throttle up and down a few times, then set it at 3200 rpm and take another break. Always within earshot of the engine sound."

Harry, can I assume that there is no one in the area where you did that? No pre-schools or nursing homes with kids and foggy oldsters wandering around? How about dumb pilots or airport rats? :eek: If I did that at my old airport in San Diego, I'd probably still be in jail. Please tell us that you're in the middle of nowhere. "Within earshot" could be hundreds of feet away. Soothe my nerves, Harry.:D


Awww...Cum' on Ken;

Didn't I preface it by: "Just make certain that nobody gets close to your machine when it's running."?!

If this required the use of a 12 ft. high, chain link fence, topped with razor wire...K-9 dogs...the Local Gendarmes...the State or National Guard, etc., so be it.

You're almost right, I am just about in the middle of nowhere.:rolleyes: I am in a far corner of the airport complex. The nearest thing to me is a couple of horses, a mule and a donkey and a few cows...all on the other side of a barb wire fence. That fence keeps me safe.:D

Now relax and pop another Lithium.:rolleyes:


Cheers :)

[Harry_S.]

Here is a pic of Tom T. Hall's stab.

Angle of incidence?


Cheers :)

[KenSandyEggo]

I prefer Paxil. You never saw a cow walk into a spinning prop?

[Ga6riel]

The thrust of the prop was great and the horizontal stab lifted the back section of the gyro up about 7 inches. It held this attitude until I lowered the gas and engine rpm. It could have been the thrust of the prop also. I'm thinking it was both,

Thom

could be how you had it hooked up with a chain and all but
shouldnt you be getting downforce not lift ?

[dragonflyerthom]

Ga6

You are probably right. The chain is what is doing this. I hadn't thought about the downforce and not lift. It was just straight as an arrow. I have 0 incidence at the present.


Thom

[Harry_S.]

Ga6

You are probably right. The chain is what is doing this. I hadn't thought about the downforce and not lift. It was just straight as an arrow. I have 0 incidence at the present.


Thom



I don't know how much you weigh, Thom.

Were you sitting in the seat...I hope you were...when you first started her up? When you sat in the seat, before starting up, did the nosewheel come down to the ground? If it did not, then the engine/prop thrust is what pushed the nose wheel down and the tail up.

Paul B. will now suggest you move your axle back 4 in.:D

The first hour or so of my break in time, I sat in the seat and made additional engine noises:p as I played with the throttle. After that, I would prop the tail up with a piece of 6x6, chock the wheels and start her up and let her run. Then I could walk around, listen and look at stuff.

When I started running her up to 4000 rpm, I would be in the seat as I would let her purr at 4000 for about 15 min. and then throttle up and down and let it run at 3500 for 10 min. etc. etc.

I would change your oil after the first 5 hrs. I used regular oil up till 50 hrs. and then switched to synthetic.


Cheers :)

[dragonflyerthom]

Harry

I was outside tha cabin in the whole thing. I still am working on my instrument panel. So all that movement is without me in it.

When I sit in it the nose goes down but I can feel it want to go back kinda. I would say that it is slightly nose heavy. Not much mind you. I weigh 200 lbs. I started proping the tail up last night. I now have about an hour on her.


Thom

[Doug Riley]

Harry, you've heard this before but others have not.

A RAF with no stab uses its rotor thrust to counter the nose-down moment that HTL creates. The rotor has to hold up the nose. The rotor thrust line in cruise flight MUST, by the most basic rules of physics, end up ahead of the CG.

A gyro laid out according to Bensen's specs will have to dangle quite nose-low to get the rotor thrust line enough ahead of the CG. My early Air Command, which had a fairly vicious HTL, flew so nose-low at high throttle that it gave a very strong sense of trying to dump you out, like dirt out of a wheelbarrow.

People who don't like this nose-low stance will move their rotor head forward to "correct" it. That's what Chuck Beaty means when he says HTL gyros fly tail-heavy. They have to; a tail-heavy (i.e way forward) location for the rotor thrust line is necessary to counter the prop's tendency to push the nose over.

If you take a gyro that's set up like this and add a down-loaded HS without changing anything else, things will get all weird on you. Remember, you intentionally built in a state of tail-heaviness to deal with the prop thrust. Now that you've put a down-loaded HS on, you no longer need the tail-heavy setup. But you've still got it. It's no surprise that the machine flies excessively nose-high.

You need to move your rotor head back when adding a down-loaded HS, IF (only if) your machine used to fly level without the HS.

OTOH, if your machine flew wih its chin low like my Air Command did, the HS will bring it back to a level stance; no rotor head adjustment needed.

[BrianBeatty]

I put a parham style H- stab on my RAF. It is approx. 10 lbs. I want to put 10 lbs. up front to keep the balance close to where it was before. Thinking about adding fluid to the nose wheel, any thoughts if this is good idea or bad ?

[Aussie_Paul]

I put a parham style H- stab on my RAF. It is approx. 10 lbs. I want to put 10 lbs. up front to keep the balance close to where it was before. Thinking about adding fluid to the nose wheel, any thoughts if this is good idea or bad ?

....Bad Brian. All you need yo do is shift the axle back 3". You will find it nice. I can send you the details if you want. Not a big job at all.

Aussie Paul.:)

[BrianBeatty]

Thanks for your input PB. I think moving the axle is a good idea and will probaly do that when I modify my gyro to closer CLT, but I want to keep the plane balanced in the air. The axle mod. just balances it on the ground.

[PW_Plack]

Thom, I just read your post above about the tail rising during a tied-down engine run. This is what the H-stab should prevent. Your thrustline is high enough that it wants to push the nose down, the stab should oppose it.

From what I've read over the years, it's a trick to get enough downforce on an H-stab to fully neutralize the thrustline offset of an RAF in stock configuration. Some negative incidence should help.

[WHUBBS]

i just installed the air command H/S with winglets on my new raf build project and the company said it's weight was 12 lb. i put it on a bathroom scales up on edge and the total wt. was 22 lb. and that did not include the tail extension of 2 ft. or the extended arm of two ft. for the tail wheel ?????

any thoughts please.

Wayne

[Aussie_Paul]

Wayne, IMHO you definately need to move the axle otherwise the nose comes up soooo early that to balance on the mains, or to have the n/wheel just touching the ground, the stick will be so far forwared that the reduced rotor disc AoA will take forever to get the blades up to flying speed.

I have seen it and experienced having to let the tail wheel run along the ground to get the rotors up.

Brian, as far as balanced when flying, just put the Raf head in the correct position to have the recomended hang test.

With 22 lbs out the back I would be shifting the axle back 5" and possibly running the mast in position 2.

Aussie Paul. :)

[Harry_S.]

i just installed the air command H/S with winglets on my new raf build project and the company said it's weight was 12 lb. i put it on a bathroom scales up on edge and the total wt. was 22 lb. and that did not include the tail extension of 2 ft. or the extended arm of two ft. for the tail wheel ?????

any thoughts please.

Wayne



Wayne...you're going to have Ron Menzie check out your machine? I'm sure he'll have it all squared away for you.

Like Paul said, the hang test will show a lot.


Cheers :)

[Harry_S.]

I have seen it and experienced having to let the tail wheel run along the ground to get the rotors up.





What's wrong with having the machine back on the tail wheel to help bring the rotor up to speed?!

I do this every flight. Of course I'm not moving faster than a walking pace. When the rrpm gets about 250, I ease in some fwd stick, balance on the mains, ease up to full bore and away we go.;)

Then again, with a good breeze I need a bit of throttle to keep from going backwards, while the rrpm is comin' up.


Cheers :)

[WHUBBS]

HARRY & PAUL thanks for the suggestions in ref. to the 22 lb. H/S . by installing the tail wheel 2 ft. further back, that changed my distance in inches from the ground to the wheel, per the raf builders manual.

because of this i was afraid i would not be able to flare at the proper angle, so i raised the wheel up one inch from what the manual said you need.

[WHUBBS]

HARRY, while at mentone this year, i noticed some of the gyro's had hand brakes and some did not. talking with those folks, some would say just what you said in your post above, that they would stay back on the tail wheel and run up the engine, and let the rotor hold you back instead of the hand brake and other folks said it was manditory to have a hand brake.????? i know some folks use it to taxi while keeping your feet on the rudder pedals, not sure if i need to construct one or not???

[dragonflyerthom]

Wayne

The advantage of the hand brake is you can set it up with a lock. When you run up the prerotator you can concentrate on the whole gyro and your throttle then release the hand brake and go. This is used at the 125 -140 rrpm then you get to the middle of the runway and start the take off roll. Now if you rotate to the higher rpm you won't need the hand brake. You prerotate to 190 and go from the runway.

It is up to you Ron Menzie will explain all of this when you go see him.


Thom

[Harry_S.]

HARRY, while at mentone this year, i noticed some of the gyro's had hand brakes and some did not. talking with those folks, some would say just what you said in your post above, that they would stay back on the tail wheel and run up the engine, and let the rotor hold you back instead of the hand brake and other folks said it was manditory to have a hand brake.????? i know some folks use it to taxi while keeping your feet on the rudder pedals, not sure if i need to construct one or not???



Were these in the RAF?

Experience will dictate what you need or don't need. I don't see you needing any sort of hand brake, Wayne. As you get more involved in your training, you can make these decisions. As I see it...a hand brake is totally unnecessary with the RAF.

I see no logical reason for it


Cheers :)

[Gary_in_Orygun]

I put a hand brake on mine way back when another RAF'er told me how he ran into a parked trailer while doing some taxi tests when he took his foot off the rudder pedal to apply the brake. He lost control of his steering.

I do not think you should ever remove your foot from a rudder pedal to apply the brake while in motion. That is why I have a hand-brake. Also, I can lock my brake (parking brake) when I start up or park on an inclined ramp.

[Harry_S.]

I put a hand brake on mine way back when another RAF'er told me how he ran into a parked trailer while doing some taxi tests when he took his foot off the rudder pedal to apply the brake. He lost control of his steering.

I do not think you should ever remove your foot from a rudder pedal to apply the brake while in motion. That is why I have a hand-brake. Also, I can lock my brake (parking brake) when I start up or park on an inclined ramp.



To each his own, I guess.:rolleyes:


On grass, I taxi no faster than a walking pace...reason; I see no need to taxi any faster. I'm not in a race with anybody. Plus, I want the engine temp to get to the green faster, before takeoff.

On hard surface, I taxi with the engine at idle (1250)...reason; That's where I have the idle set. If I get to rollin' faster than say 5 mph, I touch the brake a little and let it roll on till I touch the brake again. I usually have a 1/2 mile taxi and brake maybe twice.

I can see where you will have some problems if you're taxiing 10-15 mph.

I've posted this once or twice before. I consider it good advice, so I'll post it again:

If you're a new pilot to the RAF...WITH THE ROTOR REMOVED, practice taxiing for an hour or so, on GRASS only, not on hard surface. Get to a GRASS area removed from buildings, fences, vehicles or anything you're liable to hit. Taxi no faster than 3-5 mph and make S turns, 180 & 360 turns. Especially note how much wider your turns to the right are vs left turns. I guarantee what you learn here will benefit you later on.;)

I'll say again...I see no reason to install a hand brake in the RAF 2000.

With the proper technique, brake application is not needed during pre-rotation and takeoff...but this comes with experience also.


Cheers :)

[Gary_in_Orygun]

One place where I consistently need to apply the brakes is when taxiing for takeoff. Most times I must stop at the hold line until the active is clear. Sometimes I'm going around an airplane who is doing a runup.

And yes, on those bigger airports I do taxi in the 10+ speed range.

Harry, your advice is good stuff. You are proof that you can get by without a handbrake. But, I still feel having one is a safety feature.

[Aussie_Paul]

A lot of the Raf CFI's adjust the brakes that when you apply brake the right wheel brakes more thus turning the gyro to the right. You then use left rudder to keep it from going right.

In other words you turn left with the left rudder pedal and you turn right with the brakes.

I am sorry to have to say this but what designer would design a system where you have to remove you foot from a rudder pedal in order to apply brakes!!!!:eek: :eek: :eek: And worse that that, as with all the Raf problems, they do not fix the problems as they arise.

Aussie Paul.:)

[WHUBBS]

Harry, i think you are correct and experience will let me know if i need the hand brake. and yes the hand brakes that i was talking about at mentone were in the raf-2000

[WHUBBS]

i do like the thought that PAUL has, where you would adjust up one brake a little more than the other and that would allow one to make a little tighter turn in that direction if needed.

sorry, if i got off the subject of the H/S in this thread and going into hand braking, but for a new person, that has not taxied his raf yet, all that was said has really helped me be aware of other possibilities

[Doug Riley]

There are many ways to skin this cat. Some U.L. planes have bicycle-style brake handles on the stick -- like our prerotators. I've flown these and like them.

The original Bensen had separate nosewheel steering and rudder. I thought that worked pretty well. You switched to nosewheel steering once the nose wheel came down post-flare. You could then reach the scrub brake. You could hold all the rudder you wanted against crosswinds upon landing, without affecting the nosewheel. I liked this system enough to revive it for my Gyrobee.

[Harry_S.]

The original Bensen had separate nosewheel steering and rudder. I thought that worked pretty well. You switched to nosewheel steering once the nose wheel came down post-flare. You could then reach the scrub brake. You could hold all the rudder you wanted against crosswinds upon landing, without affecting the nosewheel. I liked this system enough to revive it for my Gyrobee.


You're right on there, Doug.

Most simple but very efficient...but there again...it took me several hours of operating, vis-a-vis, taxiing, spin ups, turns, takeoffs and landings...to get my brain co-ordinated with my feet.

Ahh, those were the days...with the original Bensen design.:D


Cheers :)

[Harry_S.]

A lot of the Raf CFI's adjust the brakes that when you apply brake the right wheel brakes more thus turning the gyro to the right. You then use left rudder to keep it from going right.

In other words you turn left with the left rudder pedal and you turn right with the brakes.



I'm glad you brought this point up Paul.

I meant to mention this offset brake adjustment and completely missed doing it.
Thank you.

I'm going to start a new RAF thread...for miscellaneous *stuff*, to help keep the different threads on track.


Cheers :)

[BrianBeatty]

....Bad Brian. All you need yo do is shift the axle back 3". You will find it nice. I can send you the details if you want. Not a big job at all.

Aussie Paul.:)
Paul
I would like to know why you feel that adding weight up front to counter balance the weight of adding a H-stab is ( Bad )
Has anyone else that added a H-stab on their gyro added weight up front?
I don't want to adjust the mast unless I have to. The hang test was bang on
and flies great before adding stab.I mounted the stab out the back of keel, so 10 lbs back that far from the moment arm is alot of weight

[PW_Plack]

Brian, adding any unnecessary weight, aka "ballast", degrades performance, which most people consider bad.

If you have to add weight for a temporary condition, a very light occupant, simulating instructor's weight for a first solo, etc., that's one thing. The H-stab is a permanent addition, and it's already added 22 pounds to the aircraft. To balance with ballast, you'd have to add 22 pounds on an arm the same distance forward of CG. The front of the keel's not that long, so you'll need even more weight on the shorter arm.

Paul B.'s mod will address the takeoff issue, but place the weight of the axle, and therefore the CG, even farther aft. If it is necessary to restore proper takeoff attitude, go for it, but when you get things balanced, re-hang.

[BrianBeatty]

I agree with keeping the weight down P.W.P and have shed where I could but I also want to keep it as close to the balance it was before the mod. My stab is only 10-11 lbs. That was someone else with an Air command stab that was 22 lb. If Air Command said it was suppost to weight 12 lb and it weights 22 lb I would send it back and ask for the lighter version

[Aussie_Paul]

I agree with keeping the weight down P.W.P and have shed where I could but I also want to keep it as close to the balance it was before the mod. My stab is only 10-11 lbs. That was someone else with an Air command stab that was 22 lb. If Air Command said it was suppost to weight 12 lb and it weights 22 lb I would send it back and ask for the lighter version

Brian, whenever any aircraft has a modification it is mandastory to re asses the Cof G. In the gyros case you must redo the hang test.

What was the correct hang test before the mod, will NOT be the correct hang test after the mod. That is why Raf have the adjustable mast to make up for the changes to the hang test with one or two heavy or light people, and every combination in between.

As Paul W said, the shifting of the axle is for the correct attitude for take off which will be quite different after the mod.

Aussie Paul.:)

[Harry_S.]

I'm posting these pics for Wayne. Very good detail shown.

Wayne will come on here and ask for advice as to his angle of incidence. I have no experience with this stab, so I wll pass to you experienced fellas...I will however, comment that it appears to me to be 3-4 degrees negative. Too much, I don't know?! Don't have my protractor with me...just eyeballin' it.

Edit...I like that wheel cover you added, Wayne.


Cheers :)

[Harry_S.]

Wayne;

Looking at your photos again...what brand of paint are you using and what brand of sprayer? Can't get over the mirroring (reflection) in your photos.:)

One other comment/question...are those the supplied #6 turnbuckles from RAF?


Cheers :)

[WHUBBS]

Harry, it is dupont primer, LIME LITE dupont green with gold metal flake paint , and clear coat. tomorrow i will send you the paint number. i really like the paint in the sun and the surface appears to be a very hard finish.

using the prop protractor, i measured the shims to be 2 1/4 degrees.

the turnbuckles are the standard that comes with the kit but want to change to the ones that most folks are using. would you know the part no. and could i get them from aircraft spruce?

[Harry_S.]

Here is an overhead shot of Wayne's stab. Beautiful!!


Cheers :)

[WHUBBS]

I have figured out the sq. ft. of my AIR COMMAND H/S WITH VERTICAL FINS and is as follows. the vertical fin is 2.33 sq. ft x 2 = 4.66 sq. ft.

the Horizontal stab totals 9.10 sq. ft.

i installed the shims under the H/S and i measure i have lowered tha AOA by 2.25 degrees.

[Doug Riley]

Two-and-half degrees incidence may be too much or too little, as may four degrees.

To know how much incidence to apply to your HS, you need to know (1) the nose-down moment created by the engine-prop unit (and any other nose-down moments present, for example from fuselage shape) and (2) the airspeed that the HS experiences.

The worst-case thrust-induced moment can be determined by multiplying the vertical distance between the CG and the prop thrustline by the WOT static thrust. From what I hear, this number is around 600 ft.-lb. in a stock RAF.

The HS's airspeed is harder to pinpoint. Keel-mounted HS's are likely to receive some propwash. Therefore, to start you could use an airspeed indicator connected to a long hose that terminates in a pitot tube. Position the open end of the pitot here and there around the HS (top and bottom) while doing a static runup. Use a long stick to manipulate the pitot.

If you don't see much airspeed over the HS during the static test, then it may be getting only the gyro's own airspeed. This is not good; at low flight speeds and high throttle settings, the HS will be hopelessly inadequate unless the prop blasts it.

Of course, you also have measure the HS's lever arm (= distance from the quarter-chord of the HS forward to the CG).

Using standard lift curves (I've attached some numbers*), you can determine how much down-lift your HS can make at different angles of attack. You want it to make enough down-lift so that, when this lift is multiplied by the lever arm, the resulting moment equals and opposes the nose-down airframe moment you already determined.

The calculation is simple arithmetic. It takes a lot longer to describe than it does to do it. Example: HS at 50 mph and 4 degrees negative AOA. Area 9 sq. ft. Down-lift equals 1.46 x 9 = 13 lb. If the lever arm is 8 feet, the HS can create a nose-up moment of 13 x 8, or 104 foot-lb. You can see here why you need that fast propwash to get enough HS power.

Once the HS is set, you will likely have to relocate the teeter bolt aft. HTL gyros are often "hung" so that they are tail-heavy, and you need to get rid of that once the HS is working properly.
_____________________________

* the table is a plot of lift per square foot of HS area at various angles of attack in degrees (the horizontal axis) and airspeeds in mph (the vertical axis). It's based on actual tests of a 42" x 21" 0012 HS.

[Harry_S.]

Thanks Doug for posting that in friendly layman's language...I even understand some of it.

I haven't measured the airspeed over and under the HS on my machine at static runs, but visually, it "looks" impressive...I know, visual observations don't mean ****, but it looks good on the ground and it flies good in the air.

I thought I had a big barndoor back there at 6.2 sq.ft., now Wayne comes along with 9.1 sq.ft. and his is on a much longer arm.

I'm anxious to see what Ron M. will have to say about it?!


Cheers :)

[Doug Riley]

Harry, that 600 ft.-lb. of PPO moment is a huge challenge. You can see from the chart that a HS that's only cranking out a couple pounds per sq. ft. just isn't going to cut it. Adding a few sq. ft. of HS area won't close the gap. Pushing it back to add leverage won't, either -- although both of these things will help a little.

The only things that will enable to HS to match PPO moment are (1) airspeed, by immersion or (2) reducing the PPO moment.

Lift per square foot increases as the square of airspeed. A gyro's prop blast is often 100 mph or more, so immersion is a pretty potent tactic. You get FOUR times the lift at a given AOA if you can give the HS 100 mph instead of 50.

Of course, raising the cabin is the best solution -- but you know that!

[Harry_S.]

the turnbuckles are the standard that comes with the kit but want to change to the ones that most folks are using. would you know the part no. and could i get them from aircraft spruce?




Wayne, I overlooked this part of your prior post. Sorry. I would strongly recommend you change those puny turnbuckles, here's the Part No's you would want.

AN 140-16S...This Part will come with two cable eye ends, which will make for easier safety wiring. Yes, you can get 'em from Aircraft Spruce...or from a local parts store.

Let's hope you get one each, left and right hand threaded ends.:lol: I received both R/H threads. The turnbuckles came as three separate parts. It took 2 weeks to get it straightened out.


Cheers :)

[Harry_S.]

I gotcha Doug...and I hope the newbies do as well. Far be it from me, to debate your theories or your figures.

You flew many hours in totally unstable HTL machines, as did I, so you know where I'm comin' from. One big factor in safely flying HTL machines is...pilot experience in flying HTL machines. How many pusher gyro's in past years were not unstable HTL?

I had no problems whatsoever in flying my *stock* RAF2000. I had no problems whatsoever in flying my *stabbed* RAF2000.

If a newby is set on the RAF2000, I would be the first to recommend the addition of an effective HS, even tho the stabilator is now a stock item?! Additional mods to his machine could follow.

Regimented practice flying...do not attempt any flying maneuvers your instructor has not okayed you to do. You have questions, ask your instructor. These, I fully endorse.


Cheers :)

[WHUBBS]

Harry, i will get the turnbuckles on order tomorrow, thanks for getting the part no's for me.

i have printed off all the information that DOUG RILEY has posted and really appreciate all his effort to help a new-be, like myself to understand what is going on with our machines.

[cgmg]

Harry,

Regarding the turnbuckles: If I order them with two cable eyes, how do I attach them to my rudder horn?

Mine has a grooved flat piece which the current puny turnbuckle attaches to.

If you have a picture of your attachment system, I would really appreciate it.

Thanks,

Mark

[Harry_S.]

Harry,

Regarding the turnbuckles: If I order them with two cable eyes, how do I attach them to my rudder horn? Does your turnbuckle attach with a forked end at the horn?

Mine has a grooved flat piece which the current puny turnbuckle attaches to.

If you have a picture of your attachment system, I would really appreciate it.

Thanks,

Mark



Sorry Mark...I can't visualize your turnbuckle attachment that you describe above?! It sounds totally different from what I have. Could you post a pic, please.

My rudder horn attachment utilizes a pivot piece and a pin thru the eye of the turnbuckle.

I will take a pic of my install and post it.


Cheers :)

[Doug Riley]

Some people use Quik-Links. The good ones, available from stores that sell rock-climbing gear, are quite strong. The problem is that there's no easily inspectable way to safety them. Use hard Loctite and snug them up well.

Harry's system, using purpose-made links, probably is better, though.

[Harry_S.]

Harry,

Regarding the turnbuckles: If I order them with two cable eyes, how do I attach them to my rudder horn?

Mine has a grooved flat piece which the current puny turnbuckle attaches to.


Mark



Mark...I just happened to think...do your turnbuckles have a fork end that attaches to your rudder horn?

A pic of your set-up would sure help.


Cheers :)

[cgmg]

Harry,

Here are pictures of my rudder horn setup currently. The manual says there is a 1/8" clearance in the forked piece.

[StanFoster]

Mark: I forgot to mention that when I discarded my 6/32 turnbuckles for the heavier 10/32 ones...I had to mill out the slot in the clevis for the bigger turnbuckle eye. I radiused the corners inside as well. I didnt have to take out much...mayber 1/32 of an inch each side.


Stan

[WHUBBS]

Harry, has posted photos of my air command H/S which is very heavy at 22 lb. for just the H/S not to mention the keel extension and moving the tail wheel back 2 ft.

today i thought i would see what ball park if any i would be in with the hang test before i get professional help to do it again.

i weigh 180 and added 5 gal of gas and the mast was in position 4 to start.
i obtained 1 degree nose down only.

pilot 5 gal. gas position # 1 pos. 5 degrees nose down

pilot full of fuel 23 gal. # 1 pos. 6 degrees nose down

pilot, 180 lb passenger full of fuel 23 gal # 1 pos. 8 degrees nose down

would appreciate good or bad comments please.

[Harry_S.]

Harry, has posted photos of my air command H/S which is very heavy at 22 lb. for just the H/S not to mention the keel extension and moving the tail wheel back 2 ft.

today i thought i would see what ball park if any i would be in with the hang test before i get professional help to do it again.

i weigh 180 and added 5 gal of gas and the mast was in position 4 to start.
i obtained 1 degree nose down only.

pilot 5 gal. gas position # 1 pos. 5 degrees nose down

pilot full of fuel 23 gal. # 1 pos. 6 degrees nose down

pilot, 180 lb passenger full of fuel 23 gal # 1 pos. 8 degrees nose down

would appreciate good or bad comments please.



Hi Wayne:

Would it be possible, you could measure your nose down in all four cam holes with the same load; for comparison. Controls all loose.

Pilot...5 gal/fuel.

Pilot...180 lb. passenger...5 gal/fuel.

You will probably have two better hole choices to start with after the hang tests.



.

[Harry_S.]

Harry,

Here are pictures of my rudder horn setup currently. The manual says there is a 1/8" clearance in the forked piece.



Hi Mark:

Your rudder horn attachment is the same as mine. Sorry if I mistook your description of what you had.

I originally ordered and installed the "pin eye" end of the new turnbuckle to attach to the horn. I have subsequently ordered the "cable eye" end to replace the pin eye...but haven't changed over yet. Either end is "good" but the cable eye, IMO is easier to safety.

I just removed the attaching bolt and the puny rod end and installed the new rod end, at the rudder horn. I did have to rout out some clearance as Stan mentioned. A rotary file did a quick job of that.

The other end of the turnbuckle, connecting to the rudder cable, you can go two different routes. I did it this way...using my Dremel tool and a cutting disc, I removed the crimped splice; added the TB end and crimped a new splice.

I believe it was Paulp and Rudy who used a "fork end" to the TB and attached it to the existing cable thimble with an AN3 bolt.

You can order these turnbuckle parts individually...barrels...pin, eye or fork ends. Your choice.


Cheers :)

[Harry_S.]

Harry, has posted photos of my air command H/S which is very heavy at 22 lb. for just the H/S not to mention the keel extension and moving the tail wheel back 2 ft.

today i thought i would see what ball park if any i would be in with the hang test before i get professional help to do it again.

i weigh 180 and added 5 gal of gas and the mast was in position 4 to start.
i obtained 1 degree nose down only.

pilot 5 gal. gas position # 1 pos. 5 degrees nose down

pilot full of fuel 23 gal. # 1 pos. 6 degrees nose down

pilot, 180 lb passenger full of fuel 23 gal # 1 pos. 8 degrees nose down

would appreciate good or bad comments please.



Wayne sent me a couple pics of his hang test which I am going to post on the RAF Miscellaneous Stuff...thread. He's past the stab phase now, so on to better things.:)


Cheers :)

[WHUBBS]

thanks for everyone help, on my gyro project . you folks are some fine fellows. i purchased the larger turn-buckle and installed them today ; )
also installed the doors so i can cover the machine better while traveling to ARK. for flight instructions. purchased a 14 ft new trailer and now need to rig it for travel. i look forward to make this a fun trip. it has taken me about 4 months to put this thing together and i loved every minute as i am retarded and have nothing else to do.

[Harry_S.]

Wayne;

I think you have done a fantastic job on your machine...you should be proud.

You're anxious to start your training and I'm sure you'll do well in that endeavor, too.

Have fun and keep us posted.;)


Cheers :)

[CLS447]

Best of luck with everything left to do yet, Wayne ! You have done a great job with your gyro !

I take it you're going to see Ron Menzie ? Have fun !

[WHUBBS]

YES CHRIS, i have an appointment with MR. MENZIE on oct. 9 th. but must get the airworthiness first and that will be this weekend. i appreciate you wishing me luck as i will need all i can get.

thanks

[Harry_S.]

Harry,

Regarding the turnbuckles: If I order them with two cable eyes, how do I attach them to my rudder horn?

Mine has a grooved flat piece which the current puny turnbuckle attaches to.

If you have a picture of your attachment system, I would really appreciate it.

Thanks,

Mark



Mark,

I apologize for forgetting to post a pic of my install. You probably don't need it now, anyway.

Pic is not too good anyhow, being as I had to lay on the ground under the stab. I don't know...it may help some others.


Cheers :)

[cgmg]

Harry,

No apology needed. I'm still waiting for my bigger turnbuckles from AS, anyway.

And I haven't ordered my aluminum for the Boyer mod yet, either. I do have a Word file built with all the details and pics gleaned from the various posts on RAF's, and will add this to it.

I'm not the kind of guy who's going to enjoy this build process on our RAF. I really liked the relative simplicity of bolting our Air Command together, with very little fabrication. So initially, the progress will be pretty slow, until I'm comfortable I'm ready to tackle this horse.

Short answer, thanks a bunch. It does let me see how you machined the strap out just enough to accept the eye hook.

[Harry_S.]

Hi Mark;

I can appreciate your concern in undertaking the modification of your RAF. I think that once you decide to start, you can't wait till it's finished and you can fly.

I think sometimes, I would like to do that mod, but...I really like the way my machine flies just the way it is and...it's ready to fly whenever I'm ready.:)

I'm sure you'll be consulting with Larry B. when you start. If you don't have a power rivet puller now, you should obtain one, or have access to one, as those 3/16 SS rivets are a bear to pull by hand.:help:


Cheers :)

[cgmg]

Harry,

I do intend to line up a power rivet puller.

Larry has already graciously agreed to counsel me on the modification. He even volunteered his cell number. And Paul Patterson has done the same. So support that I trust is there once the decision is made to make the first cut.

For you guys who are attuned to the nuances of your RAF's, there probably isn't a need to do the conversion. But other than our instructor's machine, I've only flown what are considered "stable" configurations. Remembering that I had a real problem with pitch excursions early in my training, it would seem prudent to do everything I can to make our new machine an easier, and safer, aircraft to fly. And since Cathy will definitely be spending more time flying this machine, it's good for both of us.

I'm also like you. I'd much rather be flying my machine than tinkering with it. The only times I tinkered with our Air Command, other than Maintenance, was out of necessity.

[Aussie_Paul]

Harry,

I do intend to line up a power rivet puller.

Larry has already graciously agreed to counsel me on the modification. He even volunteered his cell number. And Paul Patterson has done the same. So support that I trust is there once the decision is made to make the first cut.

For you guys who are attuned to the nuances of your RAF's, there probably isn't a need to do the conversion. But other than our instructor's machine, I've only flown what are considered "stable" configurations. Remembering that I had a real problem with pitch excursions early in my training, it would seem prudent to do everything I can to make our new machine an easier, and safer, aircraft to fly. And since Cathy will definitely be spending more time flying this machine, it's good for both of us.

I'm also like you. I'd much rather be flying my machine than tinkering with it. The only times I tinkered with our Air Command, other than Maintenance, was out of necessity.

Well Mark, I consider the mods a necessity for pleasant flight in all kinds of weather, particularly for inexperienced gyro pilots. Ons thing I can say with confidence is that you wil be glad you did the mods.

That was a great common sense post, Mark.

After spending 30 hours in a Raf without the stepped keel and axle move mods during the last couple of weeks, I don't ever want to do it again. Why would I when I can have a perfectly stable gyro?

When people, such as myself back in the 90's, have never flown a perfectly stable gyro they don't know the difference. After my Hybrid experience and testing I now know the difference. :)

Aussie Paul. :)

[WHUBBS]

for what it is worth, and my lack of experience flying an RAF, i am working on my 40 hours and i am very pleased with the stability of this large H/S of 9.10 sq. ft. and the 4.66 sq. ft. vertical fins. yesterday i flew 2.1 hrs, one hour at a time with a good post flight inspection in between. i did not have the doors on and the wind was only about 5-7 mph. i let go of the cyclic several times and removed my feet from the rudder's peddals and it would stay beautifully straight and level. later i will do the stability test and hopefully i will be able to get someone with much more experience in the RAF to further evaluate this H/S. i feel so comfortable in the machine that i am flying it much higher than my single seater. which i think also adds a little to the safety factor.

[Aussie_Paul]

That's great Wayne.

Aussie Paul. :)

[Harry_S.]

Wayne Hubbs...IMHO, you're doing and have already done a fantastic job in building your machine and now you're approaching the training in a sensible and logical manner. Your solo practice now sounds encouraging and you're having fun doing it. That's the secret...have fun...but don't push it.;)

All of us here on the forum are with you and I'm sure are just thrilled in seeing your progress.

Keep us posted Wayne.


Cheers :)

[WHUBBS]

Harry, you are very correct by saying don't push it and i will do as you say, that is the type of advice all of us newby's in any type of new machine must understand and comply with. you had mentioned you would like to have some better photos of my large A/C, H/S and today i tried to take some for you to post. just post one or one's that you think is the best shot.
i tried to get elevated some for a better photo but could not get the sun to shine when i really needed it.

thanks Harry, for all your help and advice.

Wayne

[Harry_S.]

Check the SIZE of this dude...it's effective and sure is pretty.

Perfect job, Wayne.


Cheers :)