Please advise:
I am not yet soloing after returning to the hobby. Instead of buying an ARF/RTF Superstar and the like, I built my very old 3-channel kit of a Cessna 172. I built it accurate and straight. Since the front gear is not steerable, I was hand-launching it. another thing, it is a little small and has a slightly high wing loading (22-23 oz/in^2). It usually flies well - but I still have hard time hand-launching it. Last week it was the second time that it crashed immediately after takeoff[&o]. It hit the grass at just above the launch speed - straight down.
As with the first time, there is absolutely no sign of damage (the fuselage is made of thick flexible plastic). Even the engine is protected by a thick plastic cowl - but now that a little lump of dirt made it to the entrance of my LA-25 carb, there was a risk that little rocks would make it inside. I removed the plug , pushed some fuel into the cylinder and genty rotated the crank so that the fuel sprinkled out of the carb. I did it three times.
My questions:
1. Take off: How should I hand launch this beast without ever crashing (reminder : relatively small (51""), no ailerons, high wing loading)?
2. Did the method above for flushing the engine suffice? I would prefer to avoid removing the carb on this new engine unless it is essential for cleaning. But I want to avoid grinding the engine with one or more soil particles that may make it to the combustion chamber.

Because of time constraints I did not add ailerons (for improved roll control immediately after launch) or steerable nose gear (for ROG).

The engine should be ok. As far as hand launching goes, about all I can say is:

Straight into the wind, SLIGHTLY up, and with a push equal to the engines pull.

Remember, at launch your plane is not at flying speed. It needs to gather speed first, then you can apply control gently (to climb or turn).

I suggest you use both gravity and the engine to gather flying speed. To do so, launch the plane toward the horizon or below, preferably below (so the plane is not angled up.) That way as the plane drops, gravity will help it gather speed. (If you launch it with an upward component, gravity will slow the plane.)

Then, do not apply elevator or try to turn until the plane is almost on the ground.... and then apply just enough elevator to get the plane level. When it has flown a few seconds level, you can gently apply some elevator to get altitude.

When you have altitude, you can try any maneuver you wish, but without altitude or flying speed, you have two strikes against you, and no room for errors in input.

Good luck!
Dave Olson

Agreed. Level launch, or "slightly" down until flying speed is obtained. IF the plane has sufficient power, level to "slightly" up will work as well.

Throwing it with too much up angle, or too much up elevator will result in a stall.
Dennis-

Somehow I usually launch at some roll angle and slightly up. When I run and push the plane hard, I lose the accurate orientation. It seems that doing it easier but focusing on the orientation. Now I remember that in these two crash cases there was no wind at all. It always quickly recovered when I launched into a 10MPH wind, regardless of my mistakes, so speed is an issue.
Future plans: Add ailerons and steerable landing gear, or retire it and move to a better design (e.g., Avistar).

A .25 model is a little large for hand launching especially with a high wing loading. I disagree with the previous poster somewhat about not having flying speed. You must hand launch the plane with enough speed to get it flying right away. If you launch it in a stall you will have no control and crash (but you know that already). When I hand launch a "larger" model I set it on the ground and throttle to full. Then I grab the model at the CG and hold it at shoulder height. Next I start jogging (always into the wind). The throw is as hard as I can safely manage. Safely meaning a level controlled throw without breaking anything in the model. I aim at a point on the ground 50-100 feet in front of me and I throw it like a football. After launch make any roll corrections and maintain a glideslope at a spot 50-100 feet ahead. Once the plane has some speed on reverse the descent and gradually climb out.

.25 too large for hand launching?

Occasionally, we'll hand launch .40 trainers, and even Sig Seniors, usually when a nose wheel is broken and the person does not have a spare (One of the trainers has no problem landing in this situation). Have a buddy throw slightly down (to build airspeed) and directly into the wind at full throttle.

Don't do it yourself, as you need to control the plane as soon as it is out of the thrower's hands.
Also, the person controlling the plane in this situation needs to be experienced, as a wrong move can be dangerous.

I don't control the plane after launching, but my instructor, who is a very good flyer. Actually, one time another very experienced guy launched it and it almost crashed, but usually, when someone other than me launches it - there's no problem.

It seems that this plane (with high wing loading and no ailerons) should be converted to ROG. Ailerons will help too. After reading all the good recommendations It still seems to me that a beginner cannot launch it safely.

There's a guy at my field who started learning after me, already soloed and does aerobatics - and he is 6 years old!

ROFL
I'm just laughing because you just called a 6 year old child a "guy." That's funny!!!!
Don't get me wrong, it's cool that he can fly and all, but please, he's not a "guy."
BTW--I'm just ribbing you a little, no harm meant....

I have always hand-launched my planes, all .40 trainers. The only one I don't hand-launch is the kadet senior,....and thats only cos its too big to hold with one hand and the transmitter in the other! I haven't crashed during a launch (yet). Its the landings that bite me, some of them unintentional[X(]

Ha! That reminds me of my Kadet Senorita! With OS .25 FP (flea power!) it originally would ROG, especially if a stiff wind was present. I bought it with the engine almost worn out. With age and use, it became weaker and weaker. A couple years ago I dug it out to do instruction with a fellow who hadn't finished his plane, yet. I could not make it ROG on a calm evening, so we hand-launched it! In the air, it could still loop and roll (after a dive, of course) but would not lift off the grass runway.

Just reminiscing. Trouble with getting old - everything reminds me of something else...
Dave Olson

OK, installed a custom made steerable nose gear and the launch problem was solved. Surprising that an LA 25 can lift a 4lbs plane off grass without any problem

It's great that you are back in the air, but I wouldn't give up that idea of an Avistar trainer. I had one with an OS46FX on it and it was a great plane to learn on and fly. I say was because it met an untimely death when a bird hit it head on.

Hi!
Hand launching is fine ...have done so with much larger airplanes than yours...problem is ...do you have adequate wing dihedral....?? You did not have ailerons you said! No dihedral and the side rudder will not control your airplane...show us a picture of what it looks like.
Regards!
Jan K
Sweden

Seen many hand launched planes go in after hand launch when the launcher threw the plane pointed "UP" at a high angle of attack. The stab and sometimes the wing are stalled out and the plane goes through several partial rolls, always getting worse as the pilot overcontrolled.

I've only found it necessary to run before throwing a plane once. The design was something called the 'Wasp'. 60 powered, fuselage was turned from a one piece balsa block. Also had less than 600 square inches of wing area. Weighed nearly 7 pounds. Couldn't take off from grass. This was back in the days of reed radios.
I've actually seen people trip while running to throw or during the throw. Usually ends up breaking the plane. Looks and sounds funny, till you think of somebody loosing control of one of today's high revving engines with razor sharp composite props.

My advise is, and sometimes I've demonstrated this, is to throw the plane firmly towards a spot maybe 100 or 150 in front of you, aiming it like you'd throw a dart.

It is built per the instructions. Has ugly 10.5deg dihedral. In order to fly off you hands well, it has to have either a strong engine or a low wing loading. Since wing loading is not nondimensional, smaller airplanes need to have lower wing loading than larger ones to retain approximately the same behavior. So my 23 oz/ft^2 is equivalent to 27 for a 40 size trainer. And the engine: LA25 for 4 lbs is not much. So even when the chief instructor launches it, it sinks to 1-2 feet above the ground before it starts gaining altitude. Of-course there is not problem in windy days (when I launch into the wind). SO it leaves little room for error. On the other hand, taking off grass is easy now.

.. yes, the Avistar will be my next project - next year (it's getting cold now in Michigan). But I needed to solo first with this one. Mission approximately accomplished.

Now that I am have soloed, I realized that the answer for the crashing on hand launch is the default one: the thing has just too much wing loading. It requires either a windy day or a strong, straight, launch. Now that it takes off from the ground the problem is on landing in a wind-less day. I either come a little too fast (and then I sometimes roll over) or too slow (and then I stall - broke a prop). The only way fro slow landing is to stall just before touch down. The problem would not happen in the Avistar, 4*40 or other low wing loading planes. I just can't give up flying this thing because it is scale (much nicer looking than all the Hobbico/Sig _-Stars).

An uncommanded roll on final would indicate a stall, unless gusty winds were present. I realize I'm getting into this conversation late, and after the main question had been answered. A stall can occur at any speed - it's angle of attack that's important to consider.

Also, if the plane drops a wing at the time of the stall, that means one wing stalled before the other one. During a power-on stall, this can be caused by the torque of the propeller, a yaw component or both. With power off, I'd be more inclined to think it's almost completely due to yaw alone.

Because of this, most of your control problems at or near stall speed can be dealt with using the rudder. It would be nice to have ailerons - can't imagine being without them - but yaw is controlled with rudder, regardless of how many control surfaces the airplane has.

I don't want to get into a debate about that, so for the sake of model aerodynamics, I will defer to anyone with more than my meager experience. However, in a stall, I think ailerons actually detract from recovery, because of the extra drag they generate, causing even greater yaw, and a better chance that the plane will spin, rather than just stall.

Just my 2cents......

This thread gave me flash backs. Thirty five years ago I learned to fly all by myself with a CG Skylane that was everything you describe and more. Overweight, underpowered (.049) and to top it off, it was rudder only. I can't complain about it because it allowed me to learn a whole bunch. I really appreaciated more power, more channels, lighter wing loading ect. in later models. The only problem is I've been out of this stuff for 25 years, and I'm almost back to where I started.

The only thing it has enough is power. I wonder whether landing at 1/5 throttle will soften the landing. Since the landing speed, which is a little too high, is determined by wing loading (and others), a little throttle might reduce the descent rate. But maybe the opposit may happen (on grass): it will bounce and then roll over..
My plan is to get a slightly wider wing with extra 15% area btw install ailerons. But that's just my way not to give up on this plane. Alternatively, my Avistar+FX46 will just be easier to fly, land, takeoff, do aerobatics. But it is not "mine" since it's an ARF (=No involvement, no creativity).

Wing loading definitly affects landing speed. You just have to have it trimmed well and avoid trying to float it in. As long as you aren't doing catistrophic damage on every landing, just consider it an education.

Is this an Irish thing? I mean you have landing gear you know! Hahahaaa ... hey no offence, was a joke that was too good to pass on!!!

I unintentionally try to teach the plane to float without enough speed. The good thing about this plane is that it crashed a few times and nothing happened - this is made of Coka-Cola type plastic, just 3 times thicker. The wet mud helps too.
The fact that the landing gear is a little soft helps - it bends on almost all landings (even good ones) and absorbs a lot of the energy. There was a rubber sign on the underside suggesting that the front wheel hit it! I am sure a balsa plane would have needed major repairs. This thing will retire when I have a 10-20 flights after soloing, so I am glad it survived the learning process.

However, for aerobatics it seems most airplanes are very durable: I built the wing without a wing joiner (just a strip of fiberglass cloth). The thing survives VERY tight loops in spite of the heavy fuselage.

The advice you've already gotten about launching your own plane is good.

I hand launch my own planes all the time but only very lightweight models. Any model with a higher wing loading I either let someone else fly and I launch it or I ask them to launch it. The decision is made on whether or not I think the other person knows how to perform a proper hand launch.

The way to hand launch a plane when you are launching for someone else is to run with the plane until you feel it trying to lift out of your hand. Give it a gentle push and it will fly straight away assuming it's trimmed.