rcfan450

I wasn't giving it rudder until I had to, which was when I started giving it more gas and it started going left. I started out giving it right rudder and it went right - the video guy didn't get the full runout - so I let off for a bit and it went straight until it started getting speed. Then I slowly had to start giving it rudder.

Either way, shouldn't the tail have come up?

I'm ok if it was my fault, please give it to me straight. I'll post the other video tonight, it hurts to watch it though, but you get the full takeoff with that video as it was from my helmet cam I was wearing.

rcfan450

This brings up a question I forgot to ask earlier. Are any of you adding engine offset (is it called cadence?) to the motor. I noticed while building this bird that the motor appears to bolt straight flat/perpendicular to the fuse. Most every plane I own has some angle to it to help with the prop wash issue.

LA7flier

My Feedback: (1)

Have to agree.....these planes require right rudder when taking off ( and in climbing maneuvers). It looks like you hit the throttle and didn't hold right rudder. I try to slowly come up on the throttle and hold right rudder til the plane breaks from the ground...also, I have found that the LA 7 coming out of the mold appears to have a slight amount of negative incidence on the horizontal tail if you drill the plugs into the indicated places.....use an incidence meter and check that you are zero or slightly positive or you will find the plane tends to climb....good luck! It is a great little flier and lots of fun!

AZThud

Mine is electric and pulls about 2500 Watts with a 16X10 prop and 12S When I built mine Iadded several degrees of right thrust above that of the Kit. Ialso changed the tailwheel and connected it via a pull pull from the rudder servo, where the tailwheel is inside the rudder.. The way I set this up is Iget a little tailwheel movement and a bunch of rudder. Ialso use a main strut off of a small EDFas the tailwheel, this gives me some rear suspension and really keeps the rear of the fuse nice and smooth. I also have Seirra Gear, on the ground the plane is pretty good.
What really amazes me about mine is that it will fly at what seems to be impossibly slow speeds and one windy day it took off before I lifted the tail, on mine Ido lift it with some down elevator. My technique is to hit the throttle pretty hard right at the start and the elevator is full back. As the plane picks up speed, Iease the elevator to neutral, and this is where the right rudder has to used, then continue forward until the tail comes up then back to neutral. With mine its about here you start to ease off on the right rudder and pull back to take off. Even with the added right thrust on verticals Ineed to put in right rudder on the way up or the plane yaws. Below is a link to a Video of mine.

www.movingmoment.net/La7.wmv


Another option is to install a gyro on the rudder, Ihave done that and it really helps, Iconfigure the gyro to a switch so that Ican turn it off or on and do not use the heading hold setting at all. Even with the gyro on, if I don't use plenty of right rudder the plane will exit the side of the runway albeit a little further down the runway.

djmoose

My Feedback: (4)

Here are quotes I've taken from this and other LA-7 threads. (I made a google doc and take notes when I read threads about a plane I'm about to build)


I have a few more questions for you:

Is this your first large warbird?
What size prop are you using?

djmoose

My Feedback: (4)

I've watched this video before and I never noticed how you can see you 'let go' of the rudder after takeoff.

Duplicator41

My Feedback: (1)

You might also check the toe in of your wheels. If you noticed from AZthud's video during take off the right wheel was off the ground before the left wheel. If your toe in is not set for either straight forward or slightly to the right (a degree or two) your plane can pull to the left. Also very soft tyres will be overridden by engine torque and it will pull to the left.

Cheers,

Andy

rcfan450

Thanks for the comments thus far. This is not my first warbird. I've had three P51's now. I liked them but went to this plane due to it's ability to not go over the nose on grass. One was the same size as this plane, the other two slightly smaller. None gave me the issues this one has.

Here's another video. It pains me to watch it.

[link=http://youtu.be/kZQhkMy4rao]Crash Video[/link]

22x8 prop
Toe in was checked after the first try
Rudder was applied to keep it straight and then full rudder just before it started going wacko, see video

I think I just need to punch it like AZThud said
I'm also going to add degrees of down and right to the motor.
I'm not going to buy any new parts tell I get it airborne!

glazier808

My Feedback: (1)

Punching it can induce larger amounts of torque when you have less airflow across the tail.  This could have a worse effect than what you have now.  It is strange that the tail doesn't come up.  Not trying to be harsh but it kinda looks like you started to apply right rudder, then let off and wasn't able to catch the torque effect in time.  I've done this myself with my 109 with similar results...

AZThud

Really shows up doesn't it, Ikeep it on a bit more now at least until the speed builds up after the gear is up and Istart to level off.

Cheers

djmoose

My Feedback: (4)

So, my honest opinion is that you need to:

1. add the right-thrust
2. try to use a smaller prop (however you're limited by your engine)

About your prop, you're using a 6 inch larger prop then AZthud is using. Most people are using an 18x8 or 18x10 on a 30 or 38 engine. A bigger disc is only going to make prop wash and P-factor worse big time. I would try to PM someone who is running a 50cc engine and see what prop they're using and how hard the takeoffs are.

I personally think you're making it way harder to takeoff with a 22 inch prop.

About your takeoffs...they're not easy. I'm not trying to talk down to you because I'm working on it too and I have a Top Flite Staggerwing that kinda does the same thing. Taking off isn't always easy and a scale plane is much harder to keep straight before ROG then an aerobatic plane.

Let me also say I've never flown the LA-7 but I'm putting together mine with a Zenoah G38 and plan on a 18x8 or 10. So, I'm not saying my opinion is the end-all correct assumption on your issue. You asked for opinions and I'm sharing what I've seen and experienced with other planes.

I hope this helps and again, thanks for sharing.

I'm very glad that you're sharing all of this because I'm very interested in hearing how the right-thrust helps. (I haven't mounted my engine yet)

SU-31 flyer

I agree with Glazier808 Quote: "Not trying to be harsh but it kinda looks like you started to apply right rudder, then let off and wasn't able to catch the torque effect in time." I can see no side rudder when plane torks left. Also if the plane leaves the ground without enought flying speed you can not hold the Prop tork which it looks like on the grass field take off. I also hear major motor increase after plane is already in trouble. I had a student that held elevator on taxi and never release it causing the tail to stay down and plane to leave ground early. Was hard for him to break. Try to feel if your doing this.

Hope all this helps its a very nice looking plane. Wish I could weather like that I'm not good at detail.

kiwibandit

Hey there fan450,
Really sorry to see you having so much grief on take-off. Have a look at my vid link. The video is taken from the side-lines so you should be able to get a better idea of speed and attitude at lift-off
I have over 50 flights on this bird now and it is one swwweeettt flier.
Power is a Saito 53cc 5 Cyl radial turning a 20x8 carbon prop.
Even from the side you can see lots of right rudder being needed and kept fed in right until you break ground. I like to get the tail up early and gain ground speed until I'm ready to launch.
Another trick to try is a small amount of flap will also help lift the tail. I don`t recommend this though until you get a better feel for the aircraft.

Have a look and let me know what you think.

http://www.youtube.com/watch?v=R2RzJJuAlk0

The Kiwi bandit
Trev.

rcfan450

Great sounding motor Kiwi! Just when I thought I had seen every LA-7 video on youtube I see another.

Ok, so I've taken a few notes and reviewed the video and accepted all your comments with gratitude.

1. ELEVATOR was totally being applied almost the whole time on the grass runway. I didn't even realize I was doing that. This must be a habit from my P51s in fear of nose over. I think that is a huge problem which I must consciously make sure I DON'T DO!!
2. Prop was actually a 22x8 chopped down to a 20x8 on the grass runway flight. It was an old knicked prop that I shaved, balanced, and put on the shelf for a "high probability of breakage flight"... mission accomplished. :-)
... so ya, prop may or may not have been an issue, I agree that it is a bigger prop than what most have on this plane and therefore....
3. I will add a couple degrees (or more) of right thrust to the motor.
4. I will also add a couple degrees of down thrust to the motor
5. Along the same lines as #1, I must get the tail up. So far with the tail being down and takeoff I can't add right rudder very much cause the wheel traction overrides the wind on the rudder and the plane will turn right, until the wheel loses traction, and then rudder takes over at which point it's too late.... you've seen the video. So, get the tail up soon so I can apply right rudder the entire time. I may have to actually give down elevator for a ways to do this. This will be totally agaisnt my normal unconscious flight controls so I gotta be on top of things.

Conclusion. I honestly think if I give it down elevator to make sure tail comes up soon, and then right rudder the entire time I'll be ok. But just to be sure I'm going to add the engine thrust down and right as well. I'm not sure what to do about the prop since the motor calls for that size. They want a 22x8 - 22x10. I may have read it on here but someone said they thought you should run a 20x8 cause technically it's just two 21cc motors, which normally run much higher rpms. I'll have to investigate that some more I guess.

rcfan450

PS - Anyone used these before. My air retracts are fine for now but for the price these aren't bad.
http://www.arfpros.com/ESM-LA-7-80-W...SMLA7-80ER.htm

glazier808

My Feedback: (1)

I think your on the right track.  Getting the tail up and in the airstream early will help.  You could put the tail wheel on a separate servo, so you can reduce the throw to it without reducing the rudder.  I do this on some of my planes.

rcfan450

Not a bad idea. I thought of a gyro too but I'm outta channels on the remote... unless I got rid of the smoke. I can't give up on the smoke that quick though. I willing to break a few more props before I do that.

AM6

Rcfan,

This model will fly at very low speeds, and the tail will come up pretty much as soon as your are rollingif not 'held down'.

Perhaps turn your rudder rate down a little, and avoidovercompensating and squirelling as the Rudder though quite small IS effective.

Goes easy onthe throttle, and you should be airborne within a few yards...But still go easy on the throttle until speed is built up.
If a ground loop starts, shut throttle immeadiately and start afresh....never a good idea to try to fly out of a ground loop situation.

It looked to methattorque(amount of) was your biggest issue probably.....One of the disadvantages of being so overpowered if not managed properly.

These are a doddle to get airborne on something like a 180 fourstroke swingingan 18'' prop where your 'available power' is far less.

Might be also be worth getting used to taking off across the front of you, with the anticipated 'lift off' point directly opposite to where you are standing (goes for landings too).
This way you are not toolong a distance from your model, and can see exactly what is going on at this vital point....

Happy Landings.
AM6

rcfan450

I agree completely. Both times I've kicked myself for just giving it all she had at the end. I know better than that and should have shut it down the second it started turning. Bone headed move for sure.

I'm not so sure my heavier plane will be off the ground in a few yards though, I sure hope it does once I get the tail up quicker and use the rudder more effectively though. More expo on the rudder is not a bad idea either.

Just ordered a 20x8 prop, not sure it'll be here by the weekend, we'll see. I could have it ready for another try if the prop shows up. Not sure how that'll effect the motor but that's the least of my worries right now. I just want the dang thing OFF the ground!!

Prekin

My Feedback: (19)

Kiwi,
your La-7 with the Saito, sounds very nice! I like it.

kiwibandit

Be careful with the expo settings. Too much expo (30% or more) will make the control surface act too much like a switch. It can make it react too hard.
Personally - I only ever use a max of 25%. But that is only my opinion. Before I got into flying big warbirds - I had a 1/4 cub. With a big flat bottom wing like these, you really learn rudder control. A favourite move was coming in with cross-wind and side-slipping all the way to touch. Sounds lame I know, but it teaches the necessary skills needed here.
Keep trying my friend. The reward will be well worth the efforts. Don`t be put off.

Kiwi Bandit
Trev.

rcfan450

Plane is fixed. Slight down and right thrust added. Just waiting for 20x8 prop to show up now...

I gotta say, I'm shocked how strong this plane is. Any of my other planes (mostly balsa/ply frames) would have died on the second crash.

Check out my "custom" weathering.......the chips and such from crashing....I'm going to airbrush those and attempt to make it look old and used and oily.

fockewulf37

My Feedback: (102)

Rc fan, one way to stop a ground loop is to put you tail wheel on a separate channel. This way you are able to use rudder without over correcting . This has worked well on Me109s. Once you line up on the runway just turn off the tail wheel. A lot of times ground loops start by the movement of the tail wheel when to try to correct with the rudder.

rcfan450

All 9 channels are being used. I really like this idea though and may attempt to figure something similar out (like just a different servo so the rate can be much slower) if the above corrections I've made don't work.

sgrady

My Feedback: (5)

Nice