F-Twister 1st & 2nd Test Flight

LAST EDITED ON Nov-21-04 AT 03:59 PM (CST)
 
I did several test flights today. The F-Twister did not crash. First flight the outboard wing came up 12" above the inboard wing and the airplane tuned toward the center of the circle. Lines got slack and it skidded across the ground and broke the prop and the spinner. Lucky it never got more than 3 feet off the ground. I thought I had plent of wing tip weight. I added another 14 grams. 2nd flight the airplane took off fine. It flies with the outboard wing 6" above the inboard wing. I did several wing overs, lots of up and down stuff. Balance and controls seem to be OK. Engine mounting bolts needed to be tightened after the flight. I added another 14 grams of wing tip weight and did the 3rd flight. The outboard wing flies 5" above the inboard wing. I did lots of wing overs, up and down stuff. Engine mounting bolts needed to be tightened again after the flight. I added another 8 grams for wing tip weight for the 4th flight this is all the weight I have with me. Total wing tip weight is now 36 grams added. The outboard wing flies 4" above the inboard wing. I did about 30 wing overs and several sharp turns. WOW, I never saw a stunt airplane turn this sharp. Full up elevator and it appears to turn as sharp as my combat airplane. I think it turns in a radius of 2 feet. This seems to be to shape but I am not sure. Turning too sharp is how I ripped the wings off of my other Twister. I checked the outboard wing when I returned home and I can see it is twisted up. I forgot to check this after I built the airplane. The MonoKote pulled up tighter on one side of the wing than the other. I need to twist the wing and reheat the monokote to get out the twist. I have the lead outs all the way back on the wing tip and the airplane does not have very much line tension. Line tension will probably get better once I remove the twist from the wing. The OS 40 LA engine is more than enough power. I got the needle adusted too rich on one flight and the airplane did not seem to care it flew good anyway. I have a 12x5 master air screw plastic prop on the engine. Fuel tank is doing fine the engine ran great and never gave me any trouble. Once I get the bugs worked out I hope the engine continues to run fine doing loops and inverted.

Gary,

Something wrong with that outboard wing flying that high. It's strange sometimes, you can have everything looking very straight, and have a trim problem. You've twisted the flaps a little to compensate?

You have lengthened wing span, right? And kept the full length flaps?
That also contributes to better response, as well as the longer tail moment. The stock Twister is more "skittish" than I like, personally, I know that the Fancherized version flies very well.

I may get some disagreement here, but I've never cared for the MA plastic props - for anything. You might try any of several wooden props or an APC, just for comparison. Props can make a huge difference.

Good luck with this project!

[photo not recovered: 3e69bb3870f12ad5.jpg]

"There is still no cure for the common birthday." -John Glenn

Move your leadouts forward for tension, they are way too far back. Hang the airplane by the leadouts and move them forward until the airplane barely hangs nose down. I mean barely! Go from there with flight tests. Get the airplane flying where you are looking straight down the wing, then try moving the leadouts forward some more, at most 1/8 at a time. You will find that your up high tension will get better as the leadouts move forward, up to a point. An 1/8 inch move will make a clear difference in how the airplane flies up high.

Once you get the warp out(most important), you'll probably have too much wing weight. Get the airplane unwarped, ie flying the same right side up and upside down. That's the only way you can tell if it is a warp or a wing weight problem. If it flys outside wing low both ways, too much weight. Outside wing high both ways, too little weight. Then fool with the wing weight. I like to use BB's and add or remove 5 BB's at a time in the early trimming.

>Move your leadouts forward for tension, they are way too far
>back. Hang the airplane by the leadouts and move them
>forward until the airplane barely hangs nose down. I mean
>barely! Go from there with flight tests. Get the airplane
>flying where you are looking straight down the wing, then
>try moving the leadouts forward some more, at most 1/8 at a
>time. You will find that your up high tension will get
>better as the leadouts move forward, up to a point. An 1/8
>inch move will make a clear difference in how the airplane
>flies up high.

Find the balance point, and put the midpoint of the leadouts between 1" and 1 1/4" behind the CG. Leave it until you get it completely level upright and inverted.

>Once you get the warp out(most important), you'll probably
>have too much wing weight. Get the airplane unwarped, ie
>flying the same right side up and upside down. That's the
>only way you can tell if it is a warp or a wing weight
>problem. If it flys outside wing low both ways, too much
>weight. Outside wing high both ways, too little weight.
>Then fool with the wing weight. I like to use BB's and add
>or remove 5 BB's at a time in the early trimming.

What's scary is that it's yawed so far out, and has a mega-ton of tip weight, yet it's STILL rolled in at him. That's an impressive warp.

But it might not be excessive tip weight - recall a previous episode where it too clsoe to 2 oz - because the leadouts were something like 3/32 welding rods....

Very nice job, I love that color. Too bad about the wing warp, I can actually see it in the picture. I had the same problem with an ARF Cardinal and it flew 10 times better once I straightened it out.

I don't know how you're swinging a prop that big on an LA .40. Mine likes an 11-4 rev-up wood. Maybe you have a bigger venturi?

LAST EDITED ON Nov-21-04 AT 03:42 PM (CST)
 

Gary,
Lose that black Master Airscrew. You should be running a 11 x 4 APC. It will make you happy and your motor happy and your plane happy. I have also used a Master Airscrew 10 x 6 wood the one with the yellow tips with good success...Grins

Greg L. Bahrman

>Too bad about the wing
>warp, I can actually see it in the picture.

No wonder it's called a "Twister".

I set the airplane up on parallels and took some measurements of the wing. The wing is not twisted bad at all. It is twisted only 1/16". I twisted the wing back the other direction and reheated the monocote. All the twist has been removed. I replaced the 12x5 prop with a 10x6 prop to reduce torque on the airplane. I bent the inboard wing flap down so it is 1/8" lower than the inboard wing flap. I put flat washers under the front side of the engine. Line tension is still ZERO on take off but once it is in the air it flies great. Both wings fly level with each other now. I removed all the extra 36 grams of wing tip weight. Turns are perfect. Line tension during flight is not much more than my 1/2a airplane but it flies excellent. I did several loops and multiple loops, several figure 8"s, inverted flight. I did all the manovers and had no problems. This is a very nice flying airplane much better than anything I have ever flown. Square corners are easy. I did about 6 flights then decided to fly my Flight Streak. The flight streak is like flying a tinker toy after flying the F-Twister. I got in several more flights on the F-Twister before it started to rain.

LAST EDITED ON Nov-21-04 AT 03:44 PM (CST)
 
WOW ! ! ! THAT'S GREAT NEWS ! ! !

>I set the airplane up on parallels and took some
>measurements of the wing. The wing is not twisted bad at
>all. It is twisted only 1/16". I twisted the wing back the
>other direction and reheated the monocote. All the twist
>has been removed. I replaced the 12x5 prop with a 10x6 prop
>to reduce torque on the airplane. I bent the inboard wing
>flap down so it is 1/8" lower than the inboard wing flap. I
>put flat washers under the front side of the engine. Line
>tension is still ZERO on take off but once it is in the air
>it flies great. Both wings fly level with each other now. I
>removed all the extra 36 grams of wing tip weight. Turns
>are perfect. Line tension during flight is not much more
>than my 1/2a airplane but it flies excellent. I did several
>loops and multiple loops, several figure 8"s, inverted
>flight. I did all the manovers and had no problems. This
>is a very nice flying airplane much better than anything I
>have ever flown. Square corners are easy. I did about 6
>flights then decided to fly my Flight Streak. The flight
>streak is like flying a tinker toy after flying the
>F-Twister. I got in several more flights on the F-Twister
>before it started to rain.
>
>Gary Weaver

Gary for line tension you might want to try some motor offset. 1-2 degrees. Good luck.

Gee Gary,
I wish you would give this plane another name, rather than "F-Twister" (how about Fancher Twister). Your designation always triggers another "f" word in my mind!

>Gee Gary,
>I wish you would give this plane another name, rather than
>"F-Twister" (how about Fancher Twister). Your designation
>always triggers another "f" word in my mind!

F = fun

LAST EDITED ON Nov-22-04 AT 10:21 PM (CST)
 
Gary,

It's great you're having a good time with your Twister. You've received some good advice. I've got a question for you and maybe some advice as well.

Your discussion of not much tension and the extremely tight corner make me want to ask you where the Twister balances. If a ship is a little tail heavy it could exhibit both of those characteristics.

From the picture it looks like you've enlarged the tail from stock. Yes? No?

If the tail is stock you probably want the CG around 15% aft of the wing halfway out the wing. If the tail is larger it can be back some from that but try not to get it more than 25% aft of the leading edge in any case. As I recall this is going to be between 1.5" and 2.5". If it's behind that you might want to put a spinner on it to bring the CG forward to that vicinity. As Brett suggested, the mid point of the leadouts aft of the CG (at the wingtip) should be right around one inch.

As Jiffy noted, the warp in the outboard wing is visible to the trained eye in the picture. I'm not sure how you are measuring it but I urge you to view the airplane carefully from behind. Because the wing is a constant chord you should be able to slowly bring the tail up until the trailing edge is in line with the top of the wing. If there is a warp you'll find that you'll still see some of the top of the wing at the tip when it disappears at the root. Reshrink the covering until the trailing edge (ignore the flaps for this test)covers up the top of the wing at the same time all the way out both wings.

An ounce and a half of tip weight on an offset winged profile sounds like a lot. Remember, you've already got the engine and tank on the outside of the fuse so there is some built in "tip" weight. Have your flying buddy watch the wing very carefully in both upright and inverted flight and note whether the wing is in line with the control lines. If not, how much out of alignment is it and in which direction (up or down) both upright and inverted. The results of that test will give us a good idea of the efficacy (proper relationship) of tip weight, wing straightness and even line offset.

Good luck. Let us know how it comes along.

LAST EDITED ON Nov-23-04 AT 09:15 AM (CST)
 
>Gary,
>
>I've got a question for
>you and maybe some advice as well.
>
>Your discussion of not much tension and the extremely tight
>corner make me want to ask you where the Twister balances.
>If a ship is a little tail heavy it could exhibit both of
>those characteristics.
>
>From the picture it looks like you've enlarged the tail from
>stock. Yes? No?
>
>If the tail is stock you probably want the CG around 15% aft
>of the wing halfway out the wing. If the tail is larger it
>can be back some from that but try not to get it more than
>25% aft of the leading edge in any case. As I recall this
>is going to be between 1.5" and 2.5". If it's behind that
>you might want to put a spinner on it to bring the CG
>forward to that vicinity. As Brett suggested, the mid point
>of the leadouts aft of the CG (at the wingtip) should be
>right around one inch.
>
>As Jiffy noted, the warp in the outboard wing is visible to
>the trained eye in the picture. I'm not sure how you are
>measuring it but I urge you to view the airplane carefully
>from behind. Because the wing is a constant chord you
>should be able to slowly bring the tail up until the
>trailing edge is in line with the top of the wing. If there
>is a warp you'll find that you'll still see some of the top
>of the wing at the tip when it disappears at the root.
>Reshrink the covering until the trailing edge (ignore the
>flaps for this test)covers up the top of the wing at the
>same time all the way out both wings.
>
>An ounce and a half of tip weight on an offset winged
>profile sounds like a lot. Remember, you've already got the
>engine and tank on the outside of the fuse so there is some
>built in "tip" weight. Have your flying buddy watch the
>wing very carefully in both upright and inverted flight and
>note whether the wing is in line with the control lines. If
>not, how much out of alignment is it and in which direction
>(up or down) both upright and inverted. The results of that
>test will give us a good idea of the efficacy (proper
>relationship) of tip weight, wing straightness and even line
>offset.
>
>Good luck. Let us know how it comes along.
>
>Ted Fancher
>
>

The tail is the exact demensions copied from the print. The plywood doublers are 1/8" instead of 3/32" this will add some nose weight. I left off the 1/2" balsa nose doubler this will make the nose light. I added the 1/16" cowling both sides of the nose this will add a tiny amount of nose weight.

The wing warp has been removed check out the pictures. Wing warp was slightly up on the outer half of the outboard wing and slightly bent like a banana near LE. I held the wing between my knees and twisted the wing back and reheated the monocoat and removed the warp and bend.

The wing tip balsa is solid on the outboard wing and hollow on the inboard wing this provides wing tip weight more than enough weight to counter balance the weight of the lead outs. The engine and fuel tank provide the rest of the wing tip weight. The outboard wing is 22 grams heaver than the inboard wing with NO lead weights attached.

The print shows CG on the wing spar. With a plastic prop and spinner CG is 1/8" off toward the tail making the airplane a tiny bit tail heavy. With a spinner and a wood prop CG is 1/4" off. With no spinner and a plastic prop CG is 3/8" off. With no spinner and a wood prop CG is 1/2" off. The test flight was done with a plastic prop and no spinner.

Fuel tank holds 6 ounces of fuel. Fuel tank is 4.5" long and 1/16" from the engine.

I have NO rubber offset I built it like the print.

I had NO engine offset I built it like the print. I later added flat washers under the front of the engine but it still flies the same.

The airplane is balances on 2 pencils in the pictures.

Looking at the last picture I can see why your were flying outboard wing high. Also use the plastic Master Airscrew to mix epoxy. I have been using their wood props as they seem more like the old Rev Ups to me. My opinion tho. -DOC Holliday

On your last picture, I notice a slight dihedral in the elevators/horizontal stab. Also, the right flap is slightly higher than the left flap at the fuselage centerline. Also my opinion.

>The wing warp has been removed check out the pictures. Wing
>warp was slightly up on the outer half of the outboard wing
>and slightly bent like a banana near LE. I held the wing
>between my knees and twisted the wing back and reheated the
>monocoat and removed the warp and bend.

The last picture shows what appears to be a 1/2" of warp in the outboard wing (TE warped down). The inboard wing *might* be warped similarly, but too much less of an extent. That's why it's flying rolled in at you upright.

>The print shows CG on the wing spar. With a plastic prop
>and spinner CG is 1/8" off toward the tail making the
>airplane a tiny bit tail heavy. With a spinner and a wood
>prop CG is 1/4" off. With no spinner and a plastic prop CG
>is 3/8" off. With no spinner and a wood prop CG is 1/2"
>off. The test flight was done with a plastic prop and no
>spinner.
<<<...>>>
>
>The airplane is balances on 2 pencils in the pictures.

As show, the CG is too far aft. I would suggest at least an ounce on the nose, and you are shooting for about 3/4" ahead of where it is shown in the pictures. Or about 1 3/8 - 1 1/2" behind the leading edge. Then move the leadouts forward to the middle of the guide (about 3/4" behind the CG).

This combination of issues would cause exactly the sorts of flight characterstics you describe.

I would be almost certain that if you fix the warp, and move the CG/leadouts forward, it will be MUCH more solid on the end of the lines.

LAST EDITED ON Nov-23-04 AT 09:01 PM (CST)
 
I am sure the wing still has some warp other wise it would not fly with the outboard wing up. I need to do like I use to do when I was flying combat. I need to take my monocoat heat iron to the flying field with me and twist the wing after every test flight until I get it right.

I guess I need to figure a way to take a better picture. After taking that other pic I went and looked at the wing. Its a shadow combined with not enough camera flash that makes the bottom of the wing look different on the left than the right. There is a window on the left side of the table that provides more light on that side of the airplane. Its raining outside so can't take a pic in the driveway.

Yes the left wing flap is 1/8" below the other flap I did that to make the airplane fly level.

If I had the spinner and plastic prop you could see the CG is only off 1/8" according to the print. Are you saying the print is wrong?

The print shows CG in the center of the spar at 2.750 from LE. The CG is 1/8" off center of the spar.

Maybe this is a better picture. I lined up the wing flaps I thought maybe they might be creating an alusion.

>I guess I need to figure a way to take a better picture.
>After taking that other pic I went and looked at the wing.
>Its a shadow combined with not enough camera flash that
>makes the bottom of the wing look different on the left than
>the right. There is a window on the left side of the table
>that provides more light on that side of the airplane. Its
>raining outside so can't take a pic in the driveway.
>
>Yes the left wing flap is 1/8" below the other flap I did
>that to make the airplane fly level.

The fixed portion of the outboard wing (in the picture above, and the new one) looks to me to be about 3/8" warped, TE down, at the tip. And it looks like it all happens in the last 12" or so. The inboard wing looks about the same, so maybe they even each other out.

The proof in the pudding is the roll angle upright and inverted. If it's the same, then whatever combinations of warps you have are cancelling each other out - to first approximation.

>If I had the spinner and plastic prop you could see the CG
>is only off 1/8" according to the print. Are you saying the
>print is wrong?
>
>The print shows CG in the center of the spar at 2.750 from
>LE. The CG is 1/8" off center of the spar.

That's too far aft. You might get away with that if everything else was in perfect trim, but it doesn't leave any margin for error. I didn't even know there was a full-sized drawing, so I have no idea what it shows. But I can tell you how to figure it out - measure halfway out one wing, measure the chord at that point, mupltiply that by .15 to .18 (15-18%) and that will give you a reasonable CG position in inches from the leading edge. This will make it much more stable and much more consistent in different conditions.

This will slow down the control response, but probably won't limit the turn. It will just take more deflection. So widen the handle spacing.

APC 11.4 You will like it with the OS 40 LA

>APC 11.4 You will like it with the OS 40 LA

Greg....thats 11x4