okay...what's with the tail dragger thing being so damn impossibly? again today i went out with my buddy and tried to fly my plane, and why did the piece of junk ground loop? every time i try to fly the thing, i have to change the prop before i even get the thing in the air. why is the torque so much different than a trike, or is it? see i wouldn't know because i haven't tried a trike yet. everyone else makes it look like it is. they make tail dragger-trainers and i like the look of it because deep down i'm a warbird junkie, so i buy and build one and i can't get the damn thing in the air unless my buddy hucks the crap. i've tried every way that i can think of to take off from slowly rolling on the throttle to holding the plane with full throttle to slamming the throttle to assault spiraling down the runway at full throttle hoping it gets airborne before it hits something. if i do manage to get it dwn the runway in a straight line, all the sudden it gets squirlly and i lose control and hit something like a pit spot, or i yank back on the elevator and barely get it up completely out of control and hope i recover from it before it snaps over (like today) and augers in. could i have too much rudder? is the plane made to make you think it's supposed to take off from a runway? because it did come with a fake chunk of wood painted to look like a tail wheel and i changed it for ground handling purposes. anyway... are all taildraggers like this or is it just me and my plane?

G'day Mate:
Sounds to me like you have way too much rudder throw, do you hold full up elevator while slowly increasing power, then release the elevator as the she starts to roll, holding just enough rudder (usually right rudder) to keep her straight, remember to hold the rudder, don't just bump it. the same way you do when driving a car, you hold the wheel as you go around a bend.
If you have too much throw it will be nearly impossible to judge just how much you need.
Best wishes,
Allan.

It would help to know what plane you are trying to fly. Is it the GP Cub you wrote about in other posts? What is your experience level?
Are you using wooden props? If so, go buy some Master Airscrew props, they will survive casual ground strikes much better than wood.
With a trike gear plane, the main wheel stays in contact with the ground for most of the takeoff roll. This tends to keep it going striaght. With a trike gear, the tail wheel comes up and you're steering with the rudder. If something causes a bit more drag on one of the two main wheels, the plane will turn.
It's possible you have too much rudder. Is it set according to the plans? It's also possible that you have the wheels set with toe out rather than toe in.
I've always maintained that taildraggers take a bit more work to get off the ground than trikes. Others disagree. Some planes, such as Cubs, are by nature more difficult than others to take off. However, it's quite common that setup issues, such as toe out on the main gear, cause some of the difficulty.

The other thing that can make tail draggers more difficult is the center of gravity position in relation to the wheels. In most scale models, including war-birds, the cg is located only slightly behind the main gear. This contributes to the scale appearance, but makes it harder to keep the tail wheel on the ground at the beginning of the takeoff roll. Once the tail wheel is off the ground, if there isn't sufficient air speed over the rudder, control is lost, and you ground loop. If the wheels are close to the CG, it also makes it easier to nose over. This will be aggravated if the plane is nose heavy. A rough runway will also make it more difficult. If there is anyway to move your main gear forward a little (an inch or so), you will see an improvement in ground handling, and better resistance to nose overs.

Holding up elevator at the beginning of the takeoff roll is absolutely necessary. Releasing it as the plane gains speed is the trick to prevent the plane climbing out too steeply and stalling.

Some tail draggers are easy, some are hard. Personnally I prefer tail draggers cause they're easier to set up, and nose gear is heavy. You just have to get used to them.

There really is an aerodynamic reason that tail draggers handle takeoffs differently than tricycle gear airplanes.

A taildragger's prop isn't square to the airflow at the beginning of the takeoff run. A trike gear airplane's prop is square and doesn't change that angle much at all.

When the prop fan isn't square to the airflow, one side has more lift than the other side. It has to do with the Angle Of Attack each prop blade encounters. The blade that is going down on one side of the fan area sees it's normal AOA plus the extra angle that comes from the taildragger's stance. The blade that is going up on the other side sees it's normal AOA minus that same stance angle. So one side pulls the airplane forward with more power, while the other side is pulling with less.

There's also a turning torque that happens when a prop fan pitches. It's called gyroscopic precession. We won't get into that other than to say it happens on the takeoff of a taildragger when the tail comes up.

What a mess, right?

Well, with our models, we've got more problems than those. We have to install our wheels to run true. And we have to install the gear so the wheels will run true (if we have them true to the gear legs that is). And we have to install the wheels on the axles so they don't bind.

And some tailwheel designs on our models have a TON of leverage, and others have about ZERO. So we have to steer some a lot to get them to turn, and when the airspeed gets up to where the rudder is working, the rudder is CRANKED over. Or we have that weak lever tailwheel and when the rudder starts to work, it almost dead straight.

You really have to think about the steering out to the runway VERSUS the steering on takeoff for a lot of models. I've got a couple of taildraggers that take a bunch of steering movement to taxi around at my field. But after I've got the suckers lined up for takeoff, they take very little rudder/steering at the first of the roll. I go from "it won't steer worth spit" to "IT STEERS LIKE CRAZY" in a heartbeat. As soon as I push the throttle forward for takeoff. I barely move the rudder on takeoff or the sucker will crank that way A BUNCH. But I've used almost full rudder to steer it out to the takeoff point. Think about it. Are you seeing that, but aren't expecting the sudden increase in steering power?

grasshopper31,
Well, without knowing what plane you are trying to fly and your experience level it's a little hard to give concrete advice, but let me venture a couple of educated guesses. As an instructor I can tell you that there is one universal fact when it comes to beginners, they over control the plane. Meaning they move the stick more than is needed. Every new student does it, so it's not something to be embarrassed about. I'd be willing to guess that is what is happening here, you are simply putting too much control in and causing the plane to act this way. When I am teaching a new student to fly I usually won't let them take off until I see that they have started to overcome the over control issues.

Also, as Chuck mentioned, if you are using the Cub you mentioned earlier then I'd say it's partly the plane. Cub are notorious for acting just as you described on the ground. That combined with the over control I mentioned above results in a situation that drives a new pilot crazy.

I have to ask if you have an instructor helping you on your flying?? If not the ground loop you are experiencing may be a minor problem compared with what you will face as soon as the plane is in the air. The instructor should be taking the plane of until you've overcome the over control issues.

Hope this helps

Ken

Just another thought based on what you wrote. The tire size may be too small. If you have a grass runway 3" tires work well. Smaller than that can make controlling more difficult because the tires are trying to push through the grass rather than roll over it. [8D]

One other thing. Just like a car, you can have understeer and oversteer. Kits that have prebent wire gear can sometimes be put on backwards and give you an oversteer condition. Look down from the top. If the wheels are turned out at the front, that's oversteer. If wire gear, reverse them. At any rate, a little toe-in will help you go straight. It preloads the gear.
There's alot of good advice here! First off, I'd use a little expo, dual rates or just turn the rudder down and make sure the wheels aren't binding.

ptulmer hit on what I was goint to say

Tail draggers can benifit from a little toe-out: the main gear wheel point to the outside a very little bit. As a groundloop starts, lets say it begins to turn to the right, the weight is shifting to the left wheel more than the right. If that left wheel was toe-in(pointing to the right some) it would tend to help the plane turn to the right. But with Toe-Out (left wheel poining left some), as weight shifts to the left wheel from a right turn, the left wheel wants to pull the plane to the left more- pulling it out of the right turn.

A wee-tiny bit of toe-out helps, and like everything else, More is not Better- too much makes it squirrelly

oh, just remembered- if you have enough room for rotation, lower the tailwheel to raise the tail a bit. Helps reduce prop induced yaw, but make sure you still have enough clearance to let the tail down some when you rotate to takeoff. Not really needed if you can avoid slamming the throttle and have a nice gradual run-up & TO

<edit>
Was just told folks set toe-in standard to taildraggers
This post reflects what was told to me by, Some Old RCguy at a field, and it helped in that particular case. This may not help in all, or your case.
</edit>

it's a laser models Colibri .20. i'll certainly try the toe in thing again though i'm sure it's okay; it's pretty beefy gear. as for ahead or inline with the leading edge of the wing, it came with wire landing gear, but those didn't last long and were replaced with the doral style and i would guess with out looking at the plane, they are right about where the old ones were because i was worried about the CG being shifted if placed incorrectly. i may have inadvertantly built them in wrong or just cruked enough after crashing the first few times, i don't know. maybe it's just time for a new plane. though i could build another set of floats and take my shot at the water front with that plane. my cub is going to eventually have floats anyway and all the work i'm going to do to that thing, i'd rather learn with and dunk an old piece of junk. but the LG is ripped out right now and i'm having thoughts of just moving it back and putting a nose gear on it while it is out of commission. as for the right thrust angle on the engine, LOL, like i said before, FRANKENSTEIN... right now it has a chunk of 1/4 inch plywood with a cut out for the engine to bolt to and is doweled through and epoxied to the fire wall. i haven't measured it with any triangles or anything, but it's pretty damn straight and i do have an architects eyes. maybe the gear is on backwards. are they supposed to sweep back looking from the side, or sweep forward? maybe i'll just change it for and grins. i do have access to a trainer, but i also work grave shift fixing real airplanes (how ironic) and trainer night at my club is tuesday evening and it seems like most trainers work during the week and i have thursday/friday off. so i would have to go try to fly, rush home to get ready for work and that's no fun. the planes don't do this on real flight G2. that's why i think it's the plane and not me. my buddy tried to take the thing off and it did it to him also. we were thinking of taking the engine off and putting huge rocket motors on the plane and launching it as high as it would go and auger it into the groung one final time, but with my luck i wouldn't be able to keep it in a dive and it would just belly in again and mess it up just enough to ground it. anyhoo, i guess i'll do some measuring and get a real engine mount and clean everything up again. it's such a confidence killer when people watch you and you can't keep from trashing your plane though. it gets hard to fix it over and over and keep going back for more.

If you discover you do need to add toe in, I suggest removing the gear from the plane, taking the wheels off and bending the gear in a vise. Whatever you do, don't try bending them on the plane, more than one of us has done this and torn the gear right off the plane.

Upon PM, I edited my post to specify what I was told & worked for me in a particular case

I have the P51 PTS and it also does that most of the time, also when landing, just as it start to roll on the pavement as it slows down, it make a wicked left turn to the point that the right wing touches the pavment, this happens about 60% of the time.
I have replaced the tail landing wheel, and also the mains, with better quality type.

roltech

I think the gear should sweep forward if at all. It sounds to me like no toe-in and overcontrolling. Once you get an oscillation started, there's no way to "outhandle"it, the best thing to do is back off the throttle and start over from a stop. If you have the capability in your Tx, add about 40-50% exponential in the rudder, it will be less sensitive around stick center and may help with the overcontrol until you get a feel for how much rudder you need; then start taking expo out until you're around 25%.

I have to disagree with the post regarding toe-out, that will only increase the tendency to oscillate on the take-off roll. You only need about 1-1/2 to 2 degrees toe-in, but it needs to be equal between the wheels.

It may be that your plane is more sensitive than most. All my planes except my old Superstar are tail draggers, and they all handle differently, some are easier than others to maintain straight on the roll, but they ALL have to be steered with the rudder. I am a big fan of the "roll the power on slowly" method, allowing airspeed to fly the plane off the ground with just a nudge of up elevator. Horsing it off quickly at max power is a recipe for ground loop or torque roll into the ground.

If you haven't flown tricycle gear yet, I strongly recommend it first. There's a reason that almost all trainers are set up this way. Warbirds will still be there for later, and hey, P-38, P-39, P-61, P-63, B-26, B-25, A-20 all have tyricycle gear

Don't look at the tail during the take-off run. Tail goes left, you add right ? The plane was turning right to begin with. Thats one possible reason for having a difficult time.

so i shouldn't have to be at full power on takeoff roll? maybe that's the problem. i don't watch the tail on the rollout either. just which way the damn thing is cruising for the edge of the runway. usually the wind has a lot to do with it also. i think even with the slightest breeze, this thing is affected. even when i try to work on ground handling through taxi practice, the tail gets blown around with the slightest breeze. should i add weight and re-adjust the CG again to hold it down better? i think it only weighs about 4 pounds total. maybe a couple ounces more.

That sensitivity sounds like you need toe-in. Hopefully, the CG is set where the manufacturer recommended it to be?[&:]

I'm sure I will get it to perform well all the time soon or later, I do have toe in on both wheels I will check the degrees on them,
this is my first low wing, although I have taken it up about 30 times since, It does not do it all the time, I can almost "most of the time" keep it straight on take off, but the landing is not good unless I land on the grass. The gear is sweep forward at the LE
I have four tricycle trainers, and have my wings, just not use to low wing plane yet.

You absolutely SHOULD be at full power on take off, just don't punch the throttle at the start of your take off roll. Just gradually push the throttle forward (maybe 5 seconds from start to full throttle). You want to be at full power to avoid stalling immediately after takeoff (thats stalling aerodynamically, not deadsticking). Once the wheels lift off the runway, don't go to full elevator. Just a touch, let the plane continue to build up speed, and do a nice gently climbout. Once you're about 50-60 feet up, turn gently away from the pit area and enter the pattern.

Brad

The main problem with taildraggers is that the main wheels are ahead of the plane's center of mass, which makes it directionally unstable when rolling on the ground. This is also known as "oversteer" . The more forward the landing gear is, the worse the oversteer is but the less likely the plane is to nose over, so landing gear position is a tradeoff between nosing over or ground looping.

If you have ever ridden in a full scale taildragger, you may have noticed that the pilot used the individual wheel brakes a lot to keep the plane straight during initial part of the take off roll and during the later part of the landing roll. If the plane starts to veer to the right, he steps on the left wheel brake a little in addition to using the rudder to get the plane straight again, until the plane is going fast enough for the rudder to be effective.

Toe in acts like automatic wheel brakes. If the plane yaws to the right, the right wheel is lined up with the direction of travel and it's rolling resistance decreases while the toed in left wheel is scrubbing sideways which increases it's rolling resistance. The increased rolling resistance of the left wheel along with the reduced rolling resistance of the right wheel counteracts the yaw and helps stabilize the plane.

I have found that using those spongy "lite" wheels also helps stabilize taildraggers. Their higher rolling resistance has a stabilizing effect similar to toe in. When the plane goes into a turn on the ground, the inertia of the turn puts the plane's weight on the outside wheel which increases it's rolling resistance while unloading the inside wheel which reduces it's rolling resistance........automatic wheel brakes!

If you are an experienced flyer but new to taildraggers, you may want to do your first few flights on a day when there is a little wind coming straight down the runway, maybe 10 to 15 mph. That way, you will already have enough airspeed for the rudder to be effective at zero ground speed and takeoffs and landings will be a breeze.