adjusting elevator

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Re: adjusting elevator

Postby Familyflyer » Thu May 22, 2014 11:38 am

Once I get mine flying I will be completely open with the results of all my testing of different mods. As open as I am with my build. (New Update to come soon on that) I feel it is very imortant that we spread the knowledge and findings that we all have so we can learn together and make it the best plane it can be. As we know with the kit, there is much left up to the builder. I really do think that what Steve has done is the answer. I see no other choice, the flap gap needs to filled in. Troy had told me not to put them on until they did testing. I wish I would have at the begining though, it would have been much easier. The plus is I will have a nice comparison with and without. That fill in at the turtle deck will keep the air from spilling out too. If it ends up not being the plane I want, I am sure there will be some takers :D
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Re: adjusting elevator

Postby levyland » Fri May 23, 2014 5:11 pm

Well I think I have started a robust discussion here.

Steve is right on the money with his experience and very much helped me with my airplane.
Especially sharing his story about the flap seals. A MUST DO FOR EVERY BUILDER!

Reading through the last several posts:
I replayed Swingles video (which I have watched a million times) and even though there is very little straight and level flying Gary's airplane was showing the same pitched up AOA as mine. That airplane has had more facelifts than Zsa Gabor, so where it was in the development when the video was shot nobody would know.

However as I have mentioned in previous posts. The adjustability of the HS remains a problem and we need to come up with an easy way to adjust it.

For both pre and aft covered airplanes.

Most likely we will have to have turnbuckles on the top and bottom forward flying wires.

Screw jack sounds cool, but unnecessary as this is only going to get adjusted once the airplane is flying.

So I think a simple shim's maybe even AN washers will suffice with an inspection cover.

As I told Troy, he is out playing cock a doodle doo for the video cameras in demonstrating the STOL characteristics of the airplane (which are awesome) however in real life we actually want to go places in the airplane too.

My airplane with a Rotax 912 ULS (100HP) weighs 820 LB empty and cruises at 65 knots. Not 90 as mentioned by one of the builders. I am embarking (as Steve has) on cleaning up the gear undercarriage and struts, and even putting in gas cap fairings to try and step on it.

I doubt I can get 10 knots from that.

Steve addresses the issue with horse power, but that costs gas money and more money in engine acquisition costs.

So lets put our thinking caps on (including you Highlander guys) and come up with some ideas.

Remember:
There are no problems just solutions........................
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Re: adjusting elevator

Postby taildrgfun » Fri May 23, 2014 6:39 pm

I do have more horsepower than most and that really does help, but I think just as important if not more important is to aerodynamically clean the airplane up. As I said before filling in the flap cove was the most important thing I did to improve the overall flying characteristics. All I have done besides that aerodynamically is the fillers by the turtleneck and the shock aero covers. I can't help but wonder how much more speed there is to gain by making the jury struts and the tail feather wires less draggy. I would also like aero covers for where the gear legs attach to the fuselage and where the lift struts attach to the fuselage and to the wings.
Steve Henry, Wild West Aircraft
(the Dead Stick Take-off Guy)
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Re: adjusting elevator

Postby levyland » Sat May 24, 2014 10:20 am

Thanks Steve for your thoughts.

To all of the guys out there building this airplane I do not want to sound negative about the airplane, because I am not.

It is a super fun airplane to fly with no bad habits as far as I have been able to ascertain. The lower speed aspects of the airplane are phenomenal.

It's just that the Highlander goes 100MPH for lots of reasons and I want to maximise the top end as much as I can.

I think the HS and main wing are fighting each other and creating drag, and as Steve has pointed out we need to concentrate on as many ways to clean up the drag.

I even ordered gas cap fairings from Kit Fox yesterday.

I will keep everyone posted as to my pursuit of this.


Keep building the dream.

Cheers,

John
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Re: adjusting elevator

Postby Jim Bair » Sat Jun 14, 2014 11:45 pm

I have been hearing of this problem from some people off forum and finally found the thread. Very interesting discussion. I am not an aeronautical engineer and haven't finished and flown my SS yet, so I am certainly no expert. That said, my gut feeling is the Steve Henry is on the right track with the flap gap seal solution. And Levyland, too. Are you guys using the same shape seal? I.e, a shared solution, or did you work separately to achieve the same solution?

I think the horizontal stab angle problem is a separate issue. Changing that angle won't change the angle the wing flies through the air, in my opinion. It will change the angle of the elevator relative to the HS, but that's it. In every aircraft, the wing does the flying and the fuselage is along for the ride. Thus the angle of incidence to make the fuselage level while the wing cruises. The tail simply controls the pitch. Maybe I missed something and am simply stating the obvious. If the flap seal helps change the COP that sounds like an excellent solution and I look forward to hearing more details. Changing the actual angle of incidence of the wing is waaaay too hard at this point, and is a factory solution for future kits.

I would expect this airplane to be slower than the Highlander. It is a much dirtier wing. But I wanted more performance on the low end, which is why I chose it over the Highlander.

Has anyone experimented with vortex generators? I hVent found the thread yet if there is one. I'm new so apologize in advance if there is and I haven't found it.

Jim
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Re: adjusting elevator

Postby danerazz » Sun Jun 15, 2014 1:39 pm

Jim,

I mentioned the same wing incidence/tail angle issue earlier and everyone seems set on this being a tail problem, and I agree with you. Changing the angle of the tail won't help how the airplane flies. It will only reduce the amount of trim in level flight, but will not bring the nose down in cruise be use the wing will still fly at the same angle at a given speed/weight.

After a bunch of screwing around I think this issue will go away because I think "fixing" it with anything other than gap seals (changing wing angle) will probably hurt you on the bottom end (too low of a fuse angle to allow the gear to do what it is supposed to). This plane is meant for STOL and forcing high speeds will always be a trade off.
Dane

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Re: adjusting elevator

Postby levyland » Sun Jun 15, 2014 4:54 pm

Jim, Dan and et all........

As I have said in previous posts:
All of us most likely bought the airplane because of it's STOL characteristics, and yes it performs very well in that area.

However the airplane incidence angles should be rigged properly and it is not!

As Jim has pointed out there is no doubt that the issue has to do with the incidence of the wing as it relates to the fuselage, and yes I can not imagine a way of fixing that as the incidence is set in the fuselage weldament.

The tail is just along for the ride. The problem is that in the current HS incidence they are fighting each other and slowing the airplane down, hence HS adjustability is necessary.

Jim I have VG on just about every lifting surface, and yes they very much help in slow flight regimes but they will do nothing to increase your top end..

Heres what I think is disturbing WHY THE FACTORY HAS NOT WEIGHED IN ON THE SUBJECT?
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Re: adjusting elevator

Postby danerazz » Sun Jun 15, 2014 5:17 pm

While Jak does occasionally weigh in here, this is not an "official" forum necessarily monitored by the factory. If someone wants the factory opinion then they should contact them directly (phones are incredible inventions) and they can fill everyone else in here.

Also, I still believe if the wing angle is changed on the fuselage so it provides a comfortable deck angle in "high-speed" cruise, there will be a detrimental effect on deck angle at takeoff and landing. The horizontal stab angle may also cause an undesired low-speed result if adjusted to work better at cruise. Remember, high lift airfoils produce increased nose down pitching moments with increases in airspeed.

The faster you fly the worse it gets, but SS flyers should want an aircraft tuned for the bottom end.
Dane

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Re: adjusting elevator

Postby levyland » Mon Jun 16, 2014 2:23 am

Dane,
The forum is an information gathering source where all builders/pilots share information, disseminate ideas and hopefully solve problems.

Many manufacturers have their own forums or blogs, and sometimes they use Wings forum.

Regardless of the forum they are usually monitored by the manufacturer and they will normally weigh in a subject, especially one of this nature.

Were not debating the merits of a paint job here.

I have used that "incredible invention" of the phone in contacting Jak, Troy, Steve Dentz, Jim Pekola, and Steve Henry but everyone is scratching their heads.

So I am filling everyone else in here, and hopefully out of the 1441 folks that have read this post we might get a few ideas cooking.

I am one of a handful SS flying with another 100 plus sold or being built.

If I were one of those builders I would want to know about this very important issue and what the factory recommendations are to resolve it while I am still building the airplane.

Per your analogy of tuning for slow or fast flight.

In straight and level flight all lifting surfaces should be parallel with their corresponding control surfaces.

Control surfaces create lift or drag.

In straight and level flight you would not lower your flaps, anymore than you would input ailerons.

It's going to pitch you up, or down, turn you right or left, but one thing is for sure.

It's going to slow you down.

The notion of setting a high angle of incidence to "tune" for the bottom end of a flight envelope does not make any more sense than setting a low angle of incidence for the high end.

Thats what fowler flaps and leading edge slats do for a living.

For me to get the leading edge of the elevator parallel with the leading of the HS takes about 15 pounds of forward pressure.

Clearly the wing and HS are fighting each other and creating drag.

Sorry I am just the messenger...................
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Re: adjusting elevator

Postby danerazz » Mon Jun 16, 2014 2:18 pm

Understood, but...

A high lift wing has a pronounced forward pitching moment with an increase of airspeed. If you want the airfoil to work at 25mph, it is going to be trying like hell to bring your tail up at 95mph. You will either have a compromise at both ends of the asi, or it will be optimized for one of them. So if you are concerned with cruise speeds you will end up with a tail that tries to drop on you at low speeds.

The flaps and slats are there for airflow modification over the wing, not to help out the stab. Pressure on the stick means out of trim.

My comment about the phone is because, yes, I am sure the factory does see this, there is no requirement for them to respond here. There are many other forums other factories do not respond to.
Dane

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Re: adjusting elevator

Postby Mountain Eagle » Wed Jun 18, 2014 9:27 pm

Great information. I have the Mountain Eagle which is similar to the Highlander and have installed bolts in the horizontal stab where I can shim it up. My initial setting is 1 degree leading edge of horizontal stab down and can go up from there.
After reading this subject, I'm very interested to see where mine ends up in flight.
Thank you,
David
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Re: adjusting elevator

Postby av8rps » Sat Jun 21, 2014 9:42 am

This is just another idea I was thinking of;

I'm not very familiar with the design details of the Super Stol wing, but is it possible to adjust the ailerons and flaps down by just a minor amount, which should in effect help change the fuselage angle at cruise? (much like Steve H did by installing flap gaps and/or flying with the flaps down 10 degrees)

I learned this is a pretty common thing to do on Lake Amphibians when they don't fly flat. Lakes tend to have weight and balance numbers all over the place affected mostly by if the battery is installed in the nose or in the rear baggage area, if it has optional fuel tanks, lots of goodies in the panel, etc. And the condition is usually made worse if you don't understand how to properly load them to get the proper CG. When I restored mine I removed a lot of old heavy junk from the cabin and baggage area, only to learn that it performed worse than before I removed all the extra weight. I was extremely disappointed to see a speed loss as well as general performance loss when I expected to see gains. But then I came to realize my Lake wasn't flying flat like it used to. Lakes have HUGE trim tabs (1/3 of the elevator), so if they aren't flat in cruise flight, speed really suffers. So I followed the advice of some Lake experts and adjusted my flaps and ailerons, and sure enough, after some minor adjusting my plane flew flat again. And I gained my cruise speed back plus some additional, and saw overall performance improvements thoughout the flight envelope.

And much like some are noticing now with the Super Stol, I can look at pictures or videos of Lake amphibs in cruise flight and tell you if they are properly rigged just by looking at where the trim tabs are set. Many Lake owners complain about poor cruise performance, and invariably they are the ones that have the trim tabs halfways up when at cruise.

Could it be this simple to fix the Super Stol? Just another idea...
Last edited by av8rps on Sat Jun 21, 2014 10:08 am, edited 1 time in total.
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Re: adjusting elevator

Postby av8rps » Sat Jun 21, 2014 10:00 am

And while I still have my thinking cap on:

How about utilizing an airfoiled horizontal stabilizer and elevator? One could dramatically impact the tail forces by doing something like Zenair has done with their 701/750. I know that might still be a pain to do, but compared to moving the entire wing incidence it would be much easier to change the tail. And who knows, it probably would improve the Super Stols' low end performance even further by adding some additional lift ???

Ok, thinking cap is being removed now...
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Re: adjusting elevator

Postby levyland » Sun Jun 22, 2014 7:35 pm

Gidday Av8rps

Thanks for your input.
Early in the piece I thought a way of getting the airplane to go faster was to negatively reflex the flaps in cruse, but Steve Henry suggested lowering the flaps 10 degrees which did raise the tail with a minimal amount of drag. About 1 knot.

It does help a bit, however the flap seals made the greatest change.

So clearly creating a negative reflex will make the tail go down.

In terms of an airfoil HS not a bad idea but way too much work at this stage. I had a good chat with Jim Pekola and shifting the HS attach point might not be as bad as we think.

At this stage I am going to clean up the drag of the gear assembly and strut and then reassess

The flap seal makes a huge difference but for all of you that have not covered the tail I would strongly suggest that you make a provision for an adjustable HS.

Thanks again for your input


Cheers,

john
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Re: adjusting elevator

Postby R Rinker » Sun Jun 22, 2014 11:57 pm

...In terms of an airfoil HS not a bad idea...


A flying tail is a joy to fly in slow flight. It is super responsive and when other airplanes start to get a little sloppy and uneasy..it still 'feels' like you are in control. I think the 750 was changed to incorporate an airfoil horizontal. As an add on (if I remember right) they provided strips to put on the bottom which made it an upside down wing, thus added slow flight control.
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