boss_blueangels

Well, this morning I went out to the local soccerfields at about 10:30AM to fly, and test my Stryker. Lately, I've been wanting to play around with the aerodynamics a bit, and built a pair of leading edge slats to install, hopefully improving high alpha flight, letting it turn better, and land a bit slower. Also i designed some winglets to see if that made any noticable differences. Well, today I finally was able to test these, with three flights. First was without any mods, and put it through its paces... loops, rolls, tight turns, and slow flight. The, i put on the Winglets... didn't notice too much of a difference. Seemed to glide a bit better, and farther. Gentler angle. Next, i added both leading edge slots. Each one was made out of balsa, about 15 inches long, 1/4 inch wide, and sanded to nice airfoil. I attached them so they stuck forward of the eading edge about 1/4 inch, and it is about 1/4 inch from the surface of the wing.
As for this test... WOW! I'd say it increased performance at least 50%! Before, the planewould never really do a loop... it'd just kind of drop out of the top when the speed bled off. But with the slots, she rounded out the top just fine, even at only half power! Turns were extremely tight. Although, a problem did develope with the elevons. I noticed that at high alpha, it had almost NO roll authority. I remember going into slow turns and moving the stick all the way left and right, without a single movement of the aircraft! Not good... But, besides that, pitch authority was amazing. No matter what the speed, I could get the nose up another 15 degrees and keep it there easily with minimal power. Landings were done consistantly with a 40 degree nose up attitude. Also, when trying to do the Strykers version of a tailslide, I would point the nose straight down, and then pull back all the way, and it was awesome because the nose would actually pitch about 30 degrees ahead of the actual movement of the flight path, making a beautifully rounded bottom, and the plane climbing with the nose about 45 degrees nose up. It's increadible... you can really save it from almost any crash just by hauling back onthe stick at any altitude, and attitude. Also, you almost cannot even tell when the airplane stalls. It just starts to slowly sink.

But, as for the roll problems... as I was still at the field, i just wanted to make a quick change, and using some thin cardboard I cut out two strips about 4.5 inches long, and inch wide. I used packing tape, and made a 1/3 inch gap between the end of the elevon and the new extension, to form a bit of a sloted flap effect. Flight tested it, and plane flew great with full roll authority, and a little extra kick in maneuvering. Even inverted flight was great with all the additions.

My next project is going to be to remove the current ailerons, and reinstall them with with a nice big gap and their own slots, to help redirect some more air around them so they will work at any AoA. Also, I wanna see if I can change the characteristics with some vortex generators, and even contemplating cutting out a slot in the wing to get even more air over the wings.

Anyway, I'll take some pics of the plane and post 'em whenever I can. Fun stuff.

Glacier Girl

My Feedback: (4)

Boss,
We're waiting......... Photos!!!!
BJ

BenMK

Hey Boss, I know you from Simviation. Cool!

Nice to see your little project!

cadetman

boss_blueangels
Pics would be nice
the leading edge extrnsion sounds Brill
Cadetman

boss_blueangels

Hey Ben, nice to see you here too! Small world eh?

I'm not really sure how to post the pictures from my gallery, but you can click on my gallery link to check them out. i tried to take them from different angles so you could see exactally how I placed them. The one "bottom view" was taken about 90 degrees to the bottom, so it shows how far out they stick. Even when blowing air over the wing you can feel a big difference in airflow seperation.

Anyway, lemme know what you think!!

Glacier Girl

My Feedback: (4)

Boss,
Could you take a picture of the leading edge addition by itself? Top,side,ends?
You may have answered a question I had on Stryker #5, Tape wouldn't adhere to new paint job, so I used standard hinges. So if I'm understanding correctly an air gap at the flap to wing joint may improve flight characteristics? And your flap extensions, just tape holding them?
No other support? Sorry for all the questions. Just don't want to crush my custom built bird.
Thanks for your help.
BJ
p.s. New ailerons from PZ have a wing shape leading edge now.

cadetman

boss_blueangels
nice pics Cheers
i have a couple of questions for you if you will indulge
what altitude do you fly from.. above sea level? preferably in good old fashion Feet
what inspired the leading edge modification?
Cadetman

boss_blueangels

Sure, I'll take some pics for you... it may take a while because I have to keep transfering pics from my PC to the computer labs on campus because my computer has so many viruses it was disabled from the school network. lol So I'll get those up ASAP!

I got my stryker this Christmas, and the packing tape (kind with string in it) sticks just fine to the paint.

Yeah, the gap helps a lot at high angles of attack, the same way a fowler flap is a little better than just a plain flap. It allows higher energy air from under the wing, to "slip" over the top of the aileron/flap and sort of re-energizes the flow, and prevents it from seperating at the trailing edge. At the high angles of attack, the air over the top of the wing begins to seperate at the TE, and therefore gives the elevons almost NO airflow to work with. And I just figured, if slotted flaps add so much more lift... why not just put it on the elevon too? But as I said... this ONLY makes a difference in really high AoA. In normal flight I noticed no difference in performance.

As for extensions... yes, just put tape on BOTH sides. They are stiff enough to still move with the elevons, but elastic enough not to make it too controlable. And yes, right now it's just more packing tape holding them on. Also, I'm only using cardboard from a box of snack bars. lol Just did it out at the field. And that sounds nice having them shaped like an airfoil... after I'm done replying to this I'm going to disconnect the elevons, and install them with the gap, and remove the "extensions." I'll evaluate both conditions, then just for the heck of it, see if there is any difference if I then add a slot to the elevons themselves.

Here is a good site I just found that explains the leading edge slot... http://www.fubarhill.com/stol.html On real airplanes they have some that actually extend on their own... when at high AoA the lower pressure over the top actually PULLS the slot out of the wing. Also, if you notice on that site, the paragraph under the chart of Coefficient of Lift... how he mentions loss of control over elevator... that's exactally why I put the "extensions" on.

The elevation here is about 1,700 feet MSL.


For the LE mod... after building my own balsa wood gliders, taking a few aerodynamics classes, and always wanting to design my own planes... it was just kind of a whim really. lol I spent hours in BORING classes, drawing out what I wanted, and just wanted to see if it would really make a difference on such a small airplane.

And since it works so great... I'm thinking of doing the same thing for my UltraSport 40... see if I can get a little extra "umph" out of her.

And if you have any more questions, don't hesitate to ask! I love talking about this stuff.

Glacier Girl

My Feedback: (4)

Boss,
Ok going back to my history classes, During the development of the P38 lightning, they ran into a similar condition where in a high speed dive, controls lost effectiveness/ locked due to aerodynamic forces on the flaps. Granted we're not going to reach 600 mph in a dive, but we're experiencing something similar due to loss of air over the flaps. And since we want speed in a dive, an air brake would be detrimental.
I now think I understand the leading edge idea, redirect air over wing for better control.

p.s. noticed all the photos in the backround, were you?
BJ

cadetman

boss_blueangels
as soon as you said a 50% increase i knew you had to be at about 2000 feet above sea level or even higher elevation
at a lower alt the mod will make the Stryker turn quicker but will slow the Stryker down.
the leading edge add on is making the wing thicker and creating more lift for you at a higher elevation
this allows better Loops
but the loss of elevon control/roll is because the elevons are Blinded from the airflow at high/medium AoA
you need to create a DisFlow of air to regain the roll control on the elevons
hope this helps
Cadetman

boss_blueangels

BJ--Yeah, same kind of idea, just different causes. And the little slot in the elevon takes no real toll on performance, and if anything, increases the performance.

Cadetman-- That's a good point, i'm going to be going home next weekend where the elevation is a mere 50 feet. I will disconnect them, and fly with and without to compare. hopefully it'll be on the cold side to get even better than sea-level perforance. It'll be interesting to see if I notice a change in the performance. The way i made them i'm sure it'll add a lot of drag. lol

Also, what's DisFlow?

boss_blueangels

Oh, also, as for pics, just a few in the background are my own. The one of the Blue Angel delta formation has the signatures of the 2003 team, and the Blue Angel stationary/card on the left is from Lt. Scott Kartvedt, former Lead Solo pilot from 2001.

For more pics see my website www.cwu.edu/~fortenbj if you want.

cadetman

boss_blueangels
DisFlow is when you deliberatly disrupt the airflow on one wing to keep roll control in a high alpha flight
the wing with the disrupted airflow will drop
if you have ever been on a commecial flight on take off you will often see a flap of metal move up and down,
its not the flaps or airlerons but a sheet of metal halfway between L.E & T.E
i think its automatically deployed in commercial aircraft to keep the wings level on take off
another way to achieve the same result would be to have your leading edge mod's that move in and out from the wing its self coupled to the elevons..Now That would Be Awesome

you should see a difference at the lower alt as i see a difference between 700 feet and sea level,
check out the Pressure/mb on the day you fly at sea level as it may confuse your results
its Brill idea and i am thinking of making a similar unit but not as pronounced to help me at my elevation
Cheers
Cadetman

boss_blueangels

Oh I know what you mean, a spoileron. Tomcat's have 'em too. That would e awesome to link them to the ailerons too. That one is a few airplanes down the road. lol

Well, if the weather is nice, I'll have a complete update this weekend and see how big of a difference the elevation makes on the slots.

Oh man, today it was pretty windy when I went to fly, and man this plane kicked butt! When I'd turn from the tailwind to the head wind the plane would just pivot in place, totally awesome! Several times I got it to just hover, and almost go "backwards" but the wind was too light. I was afraid to fly this plane in the wind as she's so light... but it actually does excellent in the wind! It was about 10 mph today... which improves my number of flying days by about 30! lol I'd definately be willing to go fly with another 5 mph added on. I'm used to flying my UltraSport in 30 mph wind, and this was nothing. And the LE slots certainly made a difference too! Also, the winglets help a bit with the wingdrop when she stalls.

Glacier Girl

My Feedback: (4)

Boss,
Tried my stupidity/your suggestion of air gapped ailerons. Oh MY GAWD, what a difference!!!!!
10 to 15 mph winds today. On high rates would roll instead of turning, reversed directions in it's own length.[X(]
Was too violent for me just yet,switched to low rates, was like old high rates. Will have to relearn how far to move the stick again. Also Yea, no more tape to mess with.
BJ

mrfixit54016

Maybe this has already been tried / asked, but what would the end result be of adding just the cardboard elevon extensions to a basically stock stryker?

Glacier Girl

My Feedback: (4)

mrfixit,
I belive that Boss's stryker is stock. As I posted earlier I only tried the air gap on mine, and it worked unbelievable. I would think the extensions would give you a little bit more control authority. Give it a try.

Boss,
Check out Chuck D's post in RCGroups, Stryker with split Ailerons & AIBRAKES!
BJ

boss_blueangels

Yeah, she's a stock Stryker.

Hey, that's awesome it worked so well for you! Sweet!



Today I was out flying this afternoon at home, where the elevation is 50 feet ASL, and I noticed NO speed reduction at all due to the leading edge slots. She flew just as fast as before, with no differences at all.

I'm checking out the the split ailerons thing right now, sounds cool

mrfixit54016

BJ,

Naturally, I asked the question AFTER I had already installed the elevon extensions! I have not flown it yet due to a snow storm here, but maybe Monday morning before work will have decent flying conditions.

I will post what my opinion is after my flights.

The airgap sounds like a good idea and I will probably do my next Stryker with hinges and a slight gap.

cadetman

boss_blueangels
i am somewhat suprised to read there was NO speed difference between the different Altitudes
the air is a little thicker at 50 feet above sea level in comparison to 1700 feet above sea level
and leading edge Mod or Not i would have thought you would have noticed a difference in speed due to a more dense air at the lower Alt
Cadetman

mrfixit54016

Gentlemen,

The flap extensions proved to be a great mod! I did the 1 inch x 5 inch cardboard taped onto the trailing edge of each elevon. Still a very nice flying plane, but peg that stick right or left and you will roll that plane just like the FMS program shows it doing! Unfortunately, we got a lot more snow yesterday than expected, so I only flew one battery through the plane.

Also, I have heard a lot of people talk about getting rid of all the tape and stickers on their planes. I am ready to do that as well, but I am wondering how you keep the servo wires and antenna wires retained in the bottom of the wing?

Thanks,
Eric

Glacier Girl

My Feedback: (4)

mrfixit,
Take an xacto knife/razor blade, and slit a line down the channels for the antenna/servo leads,aprox 1/8" deep. Lay the wires on top of the slit and use a popsicle stick to feed them into the slit, foam will self heal around them and they will disapear. I came up with this a while ago, never had wires come back out, never have to put up with tape peeling off paint if I have to change somthing.

Bossblueangels,
Ailerons may be too effective now, snappped both clevis pins off on some really nasty stunts,alas both parted ways on a power dive. I guess now finding weakest link in system.[:@]
BJ

cadetman

Glacier
am i reading your posting the right way?
your elevons came off at high speed?

"the only issue i have is if you push to the upper limit of the Wing/ Stryker using a Brushless set up the elevons will part company with the Wing
at low speed it will work for you but speaking as a Compete novice i think at high speed it will rip the elevons from the wing
its just a guess but i would say the Upper limit is 80 Mph "

there is always a reason why i make statements
Cadetman
Addendum
sorry to hear about the Prang

Glacier Girl

My Feedback: (4)

Cadetman,
No, ailerons stayed on, snapped the pins in the clevis's that connects control rod to the horn on the ailerons. Going to try some metal clevis's to see what happens/ or breaks next.
BJ

boss_blueangels

Wow, again, very glad to hear the mod has helped... sorry about the clevis problem though BJ... Humm... that must have been pretty sweet looking though. I hate those plastic ones. I had on bust on an elevator for a gas Avistar I had once. You can guess how that one ended. :P



Also, about the speed, I did fly the Stryker the next day, and still noticed no speed differences. In fact, I even tried out the bomb-drop thing that attaches to the top, and worked GREAT! That definately slowed me down a bit... but was able to make about 8 flight with it on. Since she sits on top, I would just power back to idle, and pitch the nose down a hare as it released, to get it clear of the prop.

Edit... too bad we don't all live close by... would be interesting to see all these Strykers trying to "shoot" the other one down with these mods. lol As you mentioned... with even a slight wind, my Stryker pretty much just pivots in place to turn around.