Hobie

Howdy glow flyers I got a question . I graduated from a Duraplane trainer a couple weeks ago to a 4* .40 ARF . I read so many good things about it being the perfect 2nd plane good low wing trainer does better aerobatics than a trainer etc. I could do pretty good basic aerobatics with my Duraplane but I just can’t get a decent roll out of this 4* . I got a used Hanger 9 Twist last Wednesday for $20 I flew it Friday for the first time and every day since . I love the way the Twist flies and it rolls and double rolls just great . I didn’t even fly the 4* for a few days I like the Twist so much . I flew the 4* one time today and I have the same problem I can not get a decent roll out of it . So my question is what am I doing wrong ? I could roll the Duraplane real well and am doing good rolls with the Twist . Oh by the way I have a OS .46 AX on both the 4* and the Twist . I know many people have the 4* they have flown for years and still love them after flying more advanced planes . I have to say I am very disappointed with my 4* right now after reading so many good things about it and paying more for it than some other ARF’s cost . I have read RC forums and forums about other interests to know what to believe and not to believe so what is my problem here ? The 4* was my first ARF could I have set up something wrong ? Could something be wrong with it out of the box I don’t notice ? I put together the Duraplane and Twist with no problems . I know this not much to go on for anyone to help me figure this out . The only other thing I can tell you is a electric flyer watched me trying to roll the 4* today and he said when I throttled up to do a roll the plane was turning left at throttle up right before I went into the roll . Any and all advice you can give me to fix this problem will be appreciated .

Thanks
Bruce

jlguru

I have both the planes you describe, similarly equipped, and I enjoy them both. You're right, the 4* doesn't roll like a Twist. It doesn't have the control surface area and deflections of the Twist. The only thing I suggest you change is your mind set. The Twist can be wildly acrobatic and if that's what you want, then fly it. The 4* is more like a poor man's pattern plane. It flies straight, true and "on the wing". Use it to practice/learn/demonstrate moves that require finesse, like inverted flight, perfectly round loops, huge inverted loops, 4-point rolls, slow rolls, hovering, rolling circles, sustained knife edges, graceful coordinated turns, and silky smooth cross-wind landings. I expect there will be posts that suggest different mods to help the roll performance of the 4*, but it will never roll like your Duraplane or Twist, it's not the plane's character. So, just learn to appreciate and take advantage of what the 4* does well and fly the Twist when you feel like banging the sticks. A 4* flown well by an expert pilot can be a thing of beauty and grace.

Live long, and prosper
Jerry L. Gubka

da Rock

You're talking about an axial roll right? where you simply jam the aileron stick to one side and hang on, right?

Is it not rolling fast enough or is it not holding it's heading well enough?

Have you tried rolls in both directions? Does it roll faster in one direction than it does in the other?

First off, the 4* is advertised just as you've noticed, as a good low wing trainer that does decent aerobatics. The Twist isn't a trainer; it's designed to be thrashed about. A trainer usually has design features that cause it to try to fly upright and straight. Those features cause the trainer to fight aerobatics. When a trainer is said to be a good 2nd plane, they're telling you that it is less trainer than the primary ones. So it fights less, but will still resist somewhat. The Twist is neither a primary or 2nd trainer. So the Twist isn't fighting at all.

I've been helping a friend fly his 4* and have noticed a couple of things. Those large, square wings really get bumped around by gusts. The plane doesn't pitch up or down, it does little roll bumps all the time. And it brings itself back level. I'd suggest that the plane looks like it's rolling along on a gravel road that has potholes. And it's like the buddies 4* has harder springs and shocks than my CAP for example.

It just might be that your 4* is doing what it's designed to do. The Twist certainly is.

On the other hand, almost every model can be improved. So........ Is it not rolling fast enough or is it not holding it's heading well enough? Have you tried rolls in both directions? Does it roll faster in one direction than it does in the other?

da Rock

BTW, you've just gotten a good lesson in aerodynamics.

The wing on the Twist is a "short aspect ratio" wing. Low aspect ratio wings will give the airplane a faster roll rate than it would have with a high aspect ratio wing. The 4* has a higher aspect ratio wing than the Twist, doesn't it?

You'll notice that most trainers have longer wings right? The idea is that the trainer won't be so quick to roll so that it'll be easier for the beginner to fly.

da Rock

Another thing........... (another aerodynamic difference)

Take a look at the wingtips of both airplanes. Your 4* has a semi-symmetrical wing. The airfoil is a "lifting" profile. That means the wing will lift "up" better than it will lift "down". So when an airplane with a lifting wing is upside down, the wing isn't going to be lifting like it did right side up. The plane will head for the ground unless the pilot pushes in some "down".

A lot of airplanes require you to fly the airplane in the roll with more than just your aileron stick. You have to do more than just whack the stick to one side or the other. You often have to use some down elevator as the model rolls through the inverted parts of the roll. And some airplanes need a little bit of rudder when they're on their sides in the rolls.

Have you flown the 4* inverted? The "down" elevator is obvious then. And airplanes with semi-symmetrical wings will often take more down than others.

The Twist has a symmetrical wing on purpose. It's supposed to fly upside down a whole lot.

Hobie

I tried rolling both fast and slow adding in down elevator elevator when inverted and adding in rudder to fast roll . It didn't seem to mater . Like I said the electric guy with lots of years experiance in glow too said that when I throttle up right before I try and roll the plane is going left on me as I try and roll . My first glow plane RIP was a high wing with lots of dyhedral and I could do good rolls with it and the Duraplane high wing trainer .(see photos) I would think the 4* should be easier to roll then that high wing trainer I had shouldn't it ? I looked at the wing servo and control rods this morning and I am going to move out to the last hole on the servo arm to see if that helps it was in the hole next to the furthest one out . I think like the guy at the field told me though that when I throttle up to do a roll the plane goes left and you need to stay straight when doing a roll not making a left turn . If he is right why would the 4* turn left when increasing throttle and how do I fix it ?

2slow2matter

My Feedback: (1)

Some things you can do to increase the roll rate:
1) Increase the control surface deflection--mechanically or electronically. Move the pushrod to the outter most hole at the servo, and the inner most hole at the aileron. This will cause the aileron to travel farther. Be careful, though, that you don't cause anything to bind, or over-extend your servo's ability to handle the stress applied to it. This can also be accomplished with a computer radio using the EPA's, but is better done mechanically.

2) Seal the hinge gaps. This forces air over the surface, and doesn't allow air to pass through the hingeline. Air passing through the hingeline does nothing to help the aircraft change heading.

3) Clip the wing--shorten the wing by one or two bays. Requires some surgery, but if you've already built kits, you should be able to handle this.

4) Install larger ailerons--again, see #3

Good luck..

Commander_Drake

My Feedback: (2)

It should not pull left when you throttle up. Somthing is misaligned (or warped). Check it over carefully, with an incidence meter if possible. Make sure you dont have any left offset in the engine mount. Post some pictures if you can.

Hobie

The engine may point a little left although it looks fairly straight . Do you think putting some washers behind the left side of the engine mount is worth trying ?

jrf

My Feedback: (551)

When you throttle up you could be accidentally pulling the throttle/rudder stick to the left. Try doing the roll from high speed level flight, without throttle changes.

Jim

Hobie

[:@][>:][:@][&o][&o] Well now I am screwed forgive the pun for breaking off 2 of the 4 screws holding on the engine mount . The engine seemed to be pointing slightly left so I decided I would put washers behind the left side to make up for some of the torque left problem . I forgot about putting non permanent loctite on the very wimpy screws they provided to fit the blind nuts in the firewall . Those screws must be made of some of the cheapest weakest metal known to man . I applied very little force to get them loose and they broke so easily I didn’t even realize 2 were broke till I had the mount in my hand . So now I have more to worry about then a plane that doesn’t want to roll . I don’t think while increasing throttle a plane should start turning left . No other plane I have ever flown did that . Anyway I don’t mean to sound defensive I know I have sooooooo much to learn but should a plane try and turn left while throttling up ? One thing you are defiantly right about is if I would have flown fast till it quite turning left ( assuming it would eventually fly straight again ) I probably could have done a decent roll . Anyway at this time it is all academic till I figure a way to remount the engine with 2 snapped off screws . I am not a builder my planes were used and put together and the 4* was my first ARF the Twist just needed engine and radio . So like I said if I can’t get the broke screws out I am screwed since I wouldn’t know how or want to attempt cutting the firewall out and replace it .

CHassan

My Feedback: (13)

Was it the screws holding the motor to the mount, or the screws that hold the mount to the firewall?

If it was the ones holding the mount to the firewall there should be blind nuts on the back side of the firewall. Easy enough to knock them out and replace them. Take outthe tank and look at the backside of the firewall. Should be 4 nuts, look almost like washers from the backside. If they are not glued in, tap them out from the front side using a punch or some other object you can strike the broken bolt with. Don't hit them hard, just light taps.

Hobie

I got the engine back on the 4* it was not bad at all . I just tapped out the blind nuts with the broken screws and went and got more . I put thin washers behind the left side of the engine mount to have it point more right and increased aileron throw (with in specs ) at the servo . We will see what happens . I may not get a chance to try it for at least a day or 2 if we get the storms and winds predicted . So anyway if I don't do any better rolling it with the adjustments I made I will have a veteran flyer fly the 4* and see if every thing is set right . If it is I will have to get a little training on how to do what I have been already doing over and over with other planes . Thank you all for your great input I will let you know what happens after I fly it again and get help if I need it .

Bruce

Ed_Moorman

My Feedback: (1)

The 4*40 is in essence a low wing trainer. In stock condition, it doesn't have much of a roll rate. As has been mentioned, you can clip the wings, install wider ailerons and seal the ailerons.

With one rib clipped from each side, the plane will roll faster and you won't notice any difference in landing.

With 2 ribs clipped, the plane will roll like a bandit, but will land a little faster, not like a scale plane, but you'll notice it coming down slightly faster. A buddy of mine has one with 2 ribs clipped and he loves the rolls.

Widen the ailerons. You can buy 2" aileron stock. I always also get balsa 1/4" tri stock to glue to the leading edge of the aileron stock. This makes it easier to hinge, saves carving and adds a little to the width.

Always on every plane, seal the aileron-wing gap. I use 3M clear tape. You can't built the wings close enough to keep air from seeping through. If you think you can, move down to the gulf coast with me and go through a hurricane. 75 mph wind will get through-trust me on this.

One final thing you can do is to add end plates. These will be great on the 2 clipped rib version. They will increase the roll rate and will lower the stall & landing speeds. Make them 3/4 inch wider than the rib outline. Lite ply works. You can get fancier, but I haven't noticed any difference.

Commander_Drake

My Feedback: (2)

Are you using a computer radio? If so, make sure you have all the mixes turned off.

Ernie Misner

I did have to add a bit of right and down thrust on my 4* 40 before I was happy with it. You must realize that there is a natural tendency to yaw and roll left due to torque and prop pitch, so if the engine is straight, or especially, if there is even a hint of left thrust built in, you will pull left like crazy.

I have the throws maxed out on my 4* 40 and it is very aerobatic. I love it. The roll rate (on high rates) is just fine. It will do a great flat spin also, right side up, and to the left, with about 1/3 throttle. It's awsome..... won't climb doing it though, but a nice slow, stalled decent. It takes max rudder and elevator inputs to do that too. IF your hinge line was built a bit too tight, you won't be able to get max throws. I think this is more important than sealing the hinge line. I leave a pin through the center of each hinge when glueing them in to get a nice even, and not too tight, hinge line.

Practice doing slow rolls also. That requires proper rudder inputs during the roll as well as elevator (using opposite rudder to keep the nose up) ..... and snap rolls using same direction deflection on rudder and aileron.

Ernie

Hobie

Flew the 4* today and after putting the washers behind the left side of the engine mount and moving the clevis to the outer servo arm hole she rolls just fine [8D] . I can roll her now with no effort just right or left aileron no rudder no down elevator needed . I can even do a roll like I like to coming in slow over the middle of the field throttle up quickly with up elevator then right or left aileron rolling while going up . I am now very pleased with the 4* I didn't think it was me since I could do this with much less aerobatic planes . I know I am changing subjects but my OS .46 AX on the 4* was starting with 1 flip or 2 and I now have to use the electric starter . It don't seem to stay primed I prime it then you can see the fuel go to the carb but by the time I put the glow starter on it you can see the fuel in the line go back toward the fuel tank [:@] . It never use to do that and the .46 AX on my Twist is starting with just a flip and stays primed . Once the engine starts it runs great like the other one . What could cause it not to stay primed but it runs fine once started ?

Ernie Misner

The carb spraybar is higher in relation to the tank in the 4* apparently. It's a gravity thing!

Ernie