Repairs, Upgrades and things to look for.

The Smithsonian National Air and Space Museum credits the Laser 200 for bringing about a new generation of aerobatic aircraft
boosted180
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Re: Repairs, Upgrades and things to look for.

Post by boosted180 » 08 Dec 2018 14:44

Hi all. I'm new to the group and just wanted to introduce myself. I am the proud new owner of a Laser 200! I'm looking forward to learning more about this plane and making some new friends. I have some trim issues and can sure use some help. I am neither a mechanic or builder, but I have done some projects on my RV4 so I'm half-decent with working with tools. I'm unfamiliar with this plane and in particular the torque tube system for the ailerons. I would LOVE to have a plane that flies as well as yours Dave! I saw your Pitts video and the Laser video and they look great, especially the Pitts! Is there anyone in Southern California who would like to look at my plane and give me some pointers? Or even an A/P to I can pay to sort things out for me? I'm very limited on time and in general prefer to fly than to tinker. :)

Brian

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One Winged Junkie
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Re: Repairs, Upgrades and things to look for.

Post by One Winged Junkie » 13 Dec 2018 08:54

boosted180 wrote:
08 Dec 2018 14:44
Hi all. I'm new to the group and just wanted to introduce myself. I am the proud new owner of a Laser 200! I'm looking forward to learning more about this plane and making some new friends. I have some trim issues and can sure use some help. I am neither a mechanic or builder, but I have done some projects on my RV4 so I'm half-decent with working with tools. I'm unfamiliar with this plane and in particular the torque tube system for the ailerons. I would LOVE to have a plane that flies as well as yours Dave! I saw your Pitts video and the Laser video and they look great, especially the Pitts! Is there anyone in Southern California who would like to look at my plane and give me some pointers? Or even an A/P to I can pay to sort things out for me? I'm very limited on time and in general prefer to fly than to tinker. :)

Brian
Hi Brian... Welcome to the forum!

davevon
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Re: Repairs, Upgrades and things to look for.

Post by davevon » 07 Jan 2019 20:40

Hi Brian,
Sorry I didn't get back to you sooner, other distractions have kept me off the forum.

Congratulations on your new to you Laser! I'll dig around a little and see if I can direct you to someone in your area with Laser knowledge.

Post some pictures!

Dave

boosted180
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Re: Repairs, Upgrades and things to look for.

Post by boosted180 » 11 Jan 2019 00:23

davevon wrote:
07 Jan 2019 20:40
Hi Brian,
Sorry I didn't get back to you sooner, other distractions have kept me off the forum.

Congratulations on your new to you Laser! I'll dig around a little and see if I can direct you to someone in your area with Laser knowledge.

Post some pictures!

Dave
Thanks Dave. I've been super busy working on the Laser and have not had a chance to REALLY fly it. I've only had 3 short flights since I brought her home. Hopefully I'll be done by next week and will take some pictures and finally get to fly it. For now I've just installed a wedge and adjusted the spade to compensate for the left rolling tendency, but at some point, I'd like to really figure out why it's that much off. The elevator is also really heavy and I can feel it in flight. I'm guessing it's flying with the elevator slightly down and requires a fair amount of uptrim to stay level at cruising speeds. I'll mount a camera and confirm the position of the elevator in flight. At slower airspeeds (like while landing), the stick feel is extremely heavy, just to hold the elevator up. I wonder if all Lasers are this way or if it's just mine. I believe my elevator is built bigger than what plans call for and all that extra steel tubing is making it's weight felt. I'll take some pictures when I get to the hangar this weekend.

davevon
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Re: Repairs, Upgrades and things to look for.

Post by davevon » 11 Jan 2019 09:45

Hi Brian,

Sorry, I don't know who would be a good Laser guy out there to help you with your airplane.

I was steered away from the large control surface Lasers just because of the heavy control feel. But there is something to check, where is your CG? The elevator getting that heavy on landing would suggest a nose heavy condition. How heavy does the elevator feel, at the control stick, on the ground? That would be the only influence from the weight of the elevator itself.

Checking where your CG really is presents a little bit of problem. First they're all different, using my numbers or anyone else's numbers for your airplane won't work. Second and this goes along with the first item, there is no good datum to the MAC of the wing. The CG has to be related to the MAC of the wing. With RV's and their rectangular wing it's really easy, the tapered wing of the Laser is going to require some measuring. Refer back to my first post. Basically you have to get the airplane level and using plum-bobs mark the floor for references of the outline of the wing and some reference point (your datum) that can be easily measured to for your landing gear locations. Remember to start with a airplane nose to tail centerline. All the spanwise measurements will be taken from that. I used a laser level with a vertical laser line to "scribe" long straight reference lines on the floor. Everything has to be measured off the floor, you're changing a 3D object into a 2D drawing.

Here's some info on the MAC. Remember, all wing calculations go to the center of the airplane for the root chord, even when there in no physical wing there.
https://www.airfieldmodels.com/informat ... _chord.htm
http://www.nasascale.org/p2/wp-content/ ... ulator.htm

I hope this helps,
Dave

boosted180
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Re: Repairs, Upgrades and things to look for.

Post by boosted180 » 11 Jan 2019 18:29

davevon wrote:
11 Jan 2019 09:45
Hi Brian,

Sorry, I don't know who would be a good Laser guy out there to help you with your airplane.

I was steered away from the large control surface Lasers just because of the heavy control feel. But there is something to check, where is your CG? The elevator getting that heavy on landing would suggest a nose heavy condition. How heavy does the elevator feel, at the control stick, on the ground? That would be the only influence from the weight of the elevator itself.

Checking where your CG really is presents a little bit of problem. First they're all different, using my numbers or anyone else's numbers for your airplane won't work. Second and this goes along with the first item, there is no good datum to the MAC of the wing. The CG has to be related to the MAC of the wing. With RV's and their rectangular wing it's really easy, the tapered wing of the Laser is going to require some measuring. Refer back to my first post. Basically you have to get the airplane level and using plum-bobs mark the floor for references of the outline of the wing and some reference point (your datum) that can be easily measured to for your landing gear locations. Remember to start with a airplane nose to tail centerline. All the spanwise measurements will be taken from that. I used a laser level with a vertical laser line to "scribe" long straight reference lines on the floor. Everything has to be measured off the floor, you're changing a 3D object into a 2D drawing.

Here's some info on the MAC. Remember, all wing calculations go to the center of the airplane for the root chord, even when there in no physical wing there.
https://www.airfieldmodels.com/informat ... _chord.htm
http://www.nasascale.org/p2/wp-content/ ... ulator.htm

I hope this helps,
Dave
Using the W/B information that came with the plane, my calculation puts me a little aft of the midpoint in the CG range with me sitting in the plane. According to the numbers, the plane is definitely not nose heavy. One of the past owners had to lose weight to prevent an aft CG with him in the plane. The stick feels very heavy on the ground - heavier than any other plane I've flown. If you held the stick neutral and let it go, it would spring forward with a lot of force as the elevator drops. When lifting the elevator by hand, it's very heavy and if you let it go, it would drop hard. It's noticeably heavier than 3 One-Designs I've looked at, and two Pitts I've flown. I know it's not a great comparison b/c it's a different airplane, but they're also steel tube and fabric construction. My RV by comparison is feather-weight (both in stick feel on the ground/ in the air, and also the physical weight of the elevators - no doubt in part because they're counter balanced, but the aluminum construction is also much lighter than the steel tubing/ fabric I'm guessing).

I'm quite sure it's not a nose-heavy plane that's giving the heavy stick feel. I'm almost certain that it's due to a physically heavy elevator. I'm almost tempted to build another elevator - perhaps out of carbon fiber or fiberglass? I have builder friends who fly composite aircraft who tell me it's "easy" to build another elevator. Umm... maybe for them, but not for me! Haha. Or just build another steel and fabric elevator, but reduce the size? The other problem is that the tubing in my elevator is also a little bowed. It was definitely not built straight and true.

I'll go to the hangar on Sunday and take pictures/ measurements and post them. Does anyone else feel that their elevators/ stick feel are too heavy?

davevon
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Re: Repairs, Upgrades and things to look for.

Post by davevon » 11 Jan 2019 20:49

Brian,

Does your elevators have servo tabs like a Pitts S-2B? Some of the larger Laser elevators incorporated servo tabs to help boost the elevator.

Are your elevator gaps sealed? I've come up with a tape method which is virtually zero friction.

Building a new one out of steel tube and fabric would be the only way to go. It's a known entity. Carbon or aluminum would require considerable engineering and testing to be 100% certain. I tried weighing my elevator at the T.E. in neutral but got inconsistent results. Although the elevator will fall pretty hard if you dropped it (low friction) the weights I was getting were a few ounces, which seemed too light.

Unless the original builder measured where the MAC really is relative to your datum their numbers don't mean much. Mine was off by 3/4" from what they thought on the W&B data. If you were anywhere close to being tail heavy the elevator forces would be very light regardless of the size of the elevator.

For comparison, the Vans RV's airfoil is not tolerant of being tail heavy, someone in the backseat of a RV-4 and the elevator would be pretty light. I inadvertently flew my RV-6 with the CG 1.5" behind the aft limit. The W&B with the airplane wasn't right. At 1.5" aft it was divergent in pitch. I had to lock the stick against my leg to keep it from going to full up or full down. My passenger pulled some stuff out of the luggage area and got it to neutral stability and it landed fine. By the same token I've flown a Pitts S-1T 2" aft of the aft limit (on purpose) and it handled fine, maybe a little close to neutral in yaw. The gap seal on the rudder had enough friction that the rudder would stay where you put it. Stalls upright and inverted were normal. I didn't try any spins.

Before I would start cutting up tubing I would confirm where your CG really is and then move it back and see how it feels. Two items to be concerned with as the CG goes aft, pitch stability- does the airplane return to a stable trimmed airspeed on it's own and does it recover from spins as it should. You can sneak up on both of those pretty safely.

Dave

boosted180
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Re: Repairs, Upgrades and things to look for.

Post by boosted180 » 13 Jan 2019 22:59

Testing to see if I can embed this image.

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boosted180
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Re: Repairs, Upgrades and things to look for.

Post by boosted180 » 13 Jan 2019 23:23

Dave, yes I have servo tabs on the elevators. I called them trim tabs, but I guess the proper name is servo tabs? Trim tabs would be like what's on the RVs? My plane is definitely not tail-heavy. I will try to figure out the CG when I get a chance. But for now, if I mounted a camera and look at the elevator position in flight, that would tell if the heavy stick feel is from a physically heavy elevator vs. a nose-heavy plane, right? If it's flying with elevator down and trim up to maintain level flight, that would indicate a heavy elevator? If it was nose heavy, we would see the elevator up to maintain level flight.

I had a short flight today and the elevator stick feel isn't horrible (still heavy and requires a bit of up-trim in flight), and much heavier feel as airspeed drops, but not as bad as I thought. What bothers me more though is the heavy aileron feel. The roll rate is quite good, but it just feels like there's a lot of inertia (like there's too much mass in the ailerons). Takes some time/ effort to get things going and to stop. Take a look at the photo of the spade. Those are lead plates and I'm assuming was added intentionally for flutter avoidance? I'm not very familiar with the flutter issue so please enlighten me. My ailerons are also covered in 3/32" ply, which would add a lot of weight, right? Is this common in the Lasers? All the 1D's and Pitss I've seen are just covered in fabric.

You can also see the very slight bow in the elevator forward tube. And there's a bow in the trailing edge of the right aileron also. I added a wedge and shim on the spade and now it flies level.

I only have had 5 short flights since I brought her home. The heavy stick feel and "mushiness" really bothers me. (Especially in roll. Pitch isn't too bad except when coming in to land at low airspeed). What I do like about it compared to the RV is that it flies much more neutrally. And fast roll rate! If I can get a better stick feel, I would REALLY enjoy this plane!

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boosted180
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Re: Repairs, Upgrades and things to look for.

Post by boosted180 » 13 Jan 2019 23:29

I measured the "weight" of the elevator at the trailing edge and found it takes 4.6lbs of force to hold it up in neutral position. I'll measure my friend's 1D when I get a chance, but just based on how it felt, I would guess it's almost half. And my RV requires zero force to hold it in neutral (it's light anyway, but the counter-balance design definitely helps).

And the hinge-line is not sealed on any of the control surfaces.

Oh and another small problem is there is a very slight amount of slop in the top hinge attachment bushing in the rudder. It's not enough to see, but if you pushed on the rudder, you can just feel it. How important is it to fix this?

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