I have a goldberg matrix 40 and so far after 5 flights I've only had one uneventful flight! First one I ripped the landing gear out, no problem, my fault. Second flight I fluttered the ailerons and stripped two servos out. fixed that with metal gear digital servos and propped it down to a 13x4w prop down from a 12x6. Third flight was good until I pulled up from being inverted and the plane violently snapped to the right. I actually lost site of it in a corn field but somehow managed to stay steady on the controls and it popped up from the corn unscathed! Lucky, very lucky. Final flight I did nothing but take it up and evaluate the stall characteristics. Decrease power and pull up and it drops the right tip. Go faster and pull back hard and it really drops the right tip. Yet when landing it absolutely floats in like a trainer. What gives. I didn't check the lateral balance and I didn't yet check for washout in the wings. I know how to balance laterally, but how much washout should I be seeing from root to tip?
Here's a little history about me as I'm thinking maybe this plane is a step ahead of me. This is my first 3D capable plane. I'm coming from a Contender 40 that I've been flying on and off for about 10 years. It's little more than a trainer and I'm aware that the sweept LE of the MAtrix isn't as forgiving as the flat LE of the Contender. But after seeing videos of a Matrix go from level to popping up to a hover without stalling or snapping, it makes me think something is wrong with mine. If I go straight and level and yank the stick back (even on low rates) she'll snap to the right.
when this first happened I was doing an inverted harrier up high (not high enough judging from my recovery) and to finish it out and return to level I increased power (YS63, 13x4W prop) and pulled up to loop back to level when it snapped. It just seems that any angle of attack makes it snap happy, yet it will slow to a crawl on landing like a trainer. Doesn't seem right. What do you think?

Lateral balance it and check your CG.. If your lateral balance is grossly heavy on the side that keeps dropping then that is your problem.. if not then it could be a combo if your lateral balance and a CG that is too far forward..

Balance, fore-aft, is set to 5.5 inches back from LE as the manual states for a starting point. I think I'll leave that as it is, then laterally balance and check the washout. If washout is off, how do I change it? Do I twist the wing, then reshrink the covering to hold it there?

Mike

Just a thought: try a little less elevator throw. Or check your movement against the specs.

Yeah I checked and the manual says "all you can get" for the high rate throw. I understand now that too much throw can stall the wing or wing half pretty quick but I was thinking a 3D plane was designed to be flown like this. Obviously not. checking balance now. I'll update later tonight. May get a flight in this evening if the wind calms down a bit. this plane doesn't like crosswind. With all that side area and long tail moment it weathervanes pretty bad.

Mike

Double check your throws. Your throws have to be high enough to force the plane through the snap. Lateral balance may be part of the problem, but there is a point where not enough throw will cause a snap and more will get you through that point to where the plane is completely stalled. The danger zone is usually some where between 25 and 35 degrees. Make sure that you are getting a min of 40 degrees of deflection.

Checked the washout and found the left tip has zero washout and the right actually had just a hint of washin. Looks like they designed this plane with zero washout and just the right one was off. I tried to twist and reshrink the covering to correct. We'll see if it worked. I'll measure the throws more accurately today.
For lateral balance should I hold it up by the spinner and then the bottom of the fuse on the centerline. Problem is, the engine isn't on the centerline. It's about 3/16ths to the left of centerline.
Mike

The tip of the spinner should be on or very close to the center line. with the engine ofset 3/16 that should compensate for the right thrust built into the firewall. Hold the plane at the spinner tip and at the center of the fuse back at the rudder.

LAteral balance was so close to being dead-on that I didn't change anything. I guess I'll just get used to this trait of dropping a wing. I did find that pinning the throttle while I used up elevator will keep it from snapping out. If I recover from a spin then let it drop on it's own then pull out gently it tries to drop a wing. If I recover, then gas it, then pull up, it doens't drop a wing.

Mike

I'm with Brent...I think the problem is not enough throw to push beyond the stall. Also, Having the CG too far forward can make a wall tough. I'f you're trying moves like this, its time to move the CG back behind the recommended starting point.

Good luck!
Dave

whats its doing is called a accelerated stall,, see an airplane can stall at any attitude and any speed,, ask too much of the wing and it will stop flying if overloaded,,really..solution,, get the cg BACK, not forward, it will create less loading on the wing,+ less premature stall problems,, try it. i have been flying rc for 35 years,, no expert 3d but good,, and fly full scale,,CROP DUSTERS, for 20 years, good luck, and give it a try.

Hey I just flew my matrix last night and saw that it also wanted to drop a wing. I am going to try the things that you are saying. Can you explain what washout is?

flying4fun

Washout is when the trailing edge of the wing has a small twist up at the wing tip.

thanks, I balanced my and it was heavy on one side so I added so weight and I am going to fly it soon. My matrix is also pretty heavy. Satio 100 and 6v pack would this make any differance?

flying4fun

Thats odd, my review plane was a fun machine, and a real floater. Check out my video, I wrung it out.
Good luck

The YS should have plenty of power for that plane. The saito 100 would be insanely over powered. (which I love) You will probably add around 2.5 to 3oz making those changes. What does your plane weigh now and what is the wing loading?

What size tank are you all using? I am using a Saito 82.

The plane flies great now that I fixed the slight warp in the wing. Very capable plane. I love it. YS63 runs strong and reliably. I used the included fuel tank for my 63.

Mike

congrats! How much deflection are you getting on your surfaces? Did you change them?

Im REALLY suprised no one else mentioned this.

My $$ is on your elevator setup. check them for flex. I ended up ditching the pull/pull system they used and put 2 servos in the tail becuase i found it almost impossible to get the flex out of the control horns.

At certain attitudes and high loads, they WILL flex, and it will snap to the weaker side, everytime. yours does the right, mine was the left.

Best way to test this. Come by for a low pass at about 1/2-3/4 throttle. chop throttle to idle and pull into a wall. If it tips when going into a wall your elevator halves either are not matched or flexing. This is only accurate if your plane is laterally balanced as well.

Ther stock horns that mount onto the aluminum tube for the elevators suck, they flex like mad. I could hold one elevator 1/2 flat to the tail, and move the other side to full deflection they would flex THAT much.

Decent plane, i have a YS .63 on mine with a 13x4 prop, really fun for a mix of pattern and mild 3D. but lacks in many areas of 3D performance.

Airframe itself is nice, but goldbergs hardware for the plane is piss-poor, and that's being nice about it.

Even if you feel it's flying better now, check those elevators for slop, i have yet to see a matrix without issues with the setup back there.

Hmmm. Interesting points you brought up. I haven't really tried a wall since I've been half scared it will snap out like it used to. To hover I'll do a more gentler wall, then cut the throttle to stop climbing. I bet if I yank the stick back it will still drop to the right. I wonder if it is flexing in the elevator setup. Dual elevator servos are an option for sure, but for now I'll make do with the stock setup I think. On the other hand the snap to the right only would occur at partial throw on the elevator. If I pull back full up it doesn't seem to do it, so I'm not sure if flex is the issue. Still for $109.00 I'm complaining on the flight performance. I too switched to the 13x4w prop on the YS63. Nice vertical and makes for slow landings compared with the 12x6 I had on it originally.

Mike

Hey guys bad news I was out flying the other night and a guy with a trainer was there and we had a mid-air. I was pretty mad but you can't blame anyone for it. It smoked my right wing off and I tried to land it but it came down hard. Funny how they are hard to land with one wing. O well if you ain't crashing you ain't flying.

I think that you are right on about the elevator flexing.

flying4fun (i think)

that sucks flying4fun. I too had a handlful landing my Matrix with two stripped out aileron servos. somehow one aileron would move down only and it was enough to control it to get it back.

I'm considering sticking two servos in the tail for the elevator, but I'm not sure where to stick them. Does anyone think the fuse it too narrow back by the bellcrank exit holes to put two servos? That would make it easy since the pushrods are already there and cut to length.

Mike

I too has some minor snapping/tip stalling issues until I sorted out the elevator flexing. Now that I've got it worked out, I can be abusive the elevator at just about any attitude and throttle setting and it doesn't want to drop a wing. If I yank on the elevator in level flight I get a wall, in a downline I get a parachute, etc.. The only time it has a minor tendency to try and flop out is if I get a little out of shape doing waterfalls.

A rearward CG REALLY helped out with high alpha stability. I started out at 5.5" from the LE and now I think I'm at or a little beyond 6.5". It really locks in to harriers now and I noticed less and less rudder pitch coupling the farther back I moved the CG. It's still very friendly to fly and I could probably stand to move it back a little more.

I have triple rates setup - low rates for more pattern-like flying, high rates and then my all-I-can-get-on-every-surface rates.

I have a Saito .82 w/ Cline Regulator and the tank on the CG. My stock tank lasted a few months before it finally started leaking under pressure. I replaced it with a Sullivan 10oz. I've bounced around between about a dozen props and I still keep coming back to the APC 14x5N. It's by far the most well-rounded prop for everything I like to do. The 14x4W tends to feel a little dull to me and it tends to want to wing rock a little with it. I tried a few wood 14x6's but it was a bit fast and twitchy.

I'm bummed that it's been discontinued. I'm tempted to by another and let it sit on the shelf. I know I'll want another if I turf this one.

Your correct, it is to narrow to mount them there, but i did it anyway. I added a small balsa box topped with light ply to the fuse where the servos mounted to give them enough room mounting them bottoms pressed together coming out each side of the fuse. Just cut back the covering, and used Med CA to attach them.

Just be careful cutting the mounting holes if you go with 2 servos, they MUST be equally spaced from the elevator and on the same vertical plane or you will create a differential in throws.

This also shoots your CG all to hell, but that's easy enough to correct to where you want it. My tank is CG mounted with a 5cell rx pack in front of the tank for balance.