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 » 01 Feb 2019 12:04

Thanks Dave. I'll measure everything, weigh the plane and also put some plumb bobs to get some accurate measurements and determine MAC and CG in the next few weeks. I only have half a day in Ft. Lauderdale before we get on our cruise, so I guess we wont be able to meet up next week. I just thought if you happen to be in or near Ft. Lauderdale, we could meet up, but it's ok.

I had a chance to fly again last weekend, and I guess it's not as bad as I thought (but still definitely lots of room for improvement). My main complaint the lack of precision on the roll axis - there's too much inertia and difficult to stop rolls in a crisp manner. Point rolls are very hard to do well - in fact even my RV4 does better point rolls. I'm sure a lot of it has to do with the fact that it's a new airplane to me and over time I'll learn to fly it better. Although on the other hand, I have had very little time in the Pitts and Extra and those right off the bat definitely felt better and less lethargic on rolls.

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

Post by boosted180 » 04 Mar 2019 12:05

So I looked into the rigging and systematically disconnected each component to isolate where the friction is coming from. And it's the bushings. Photos attached. Is this typical with all torque-tube Lasers? Too bad there's no way to use ball bearings instead. That would completely fix the problem. For now, I used fine grit sand paper to smooth out both the tube and bushings. I was thinking of maybe polishing the tube tomorrow, but what to use and would it make a difference?? But even with the light sanding so far, it feels much better already. It was really rough before.

Any recommendations on what to use for lubrication? I have all-purpose grease. Is that good enough or is there something better? And do I use it on both the inside and outside of the bushing? Looks like it's designed to move within the U-shaped bracket and aluminum block.

The other area contributing to the heavy and "sticky" ailerons is one of the ribs is rubbing against the torque tube. I'll sand that down tomorrow and that should help also. It'll be tricky getting in there though. It's the second rib from the root I believe. I was thinking of wrapping sand paper around a tube and rotating it in there to sand it down.

Here are the photos:

https://drive.google.com/open?id=1gH4RL ... qnlp27YrlT

https://drive.google.com/open?id=1bB3M0 ... P7GLpFMxXu

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

Post by Guicensoni » 05 Mar 2019 02:10

Hi Brian, your elevator looks really oversized, that would it self explain your heavy wheigt feel, then in low speeds the huge area at the prop wash would justfi the heavy feelingns... the torque tube style ailerons are heavier than other hinged styles, mine is slightly heavy and have some inertia due to the same construction method thad was used in yours.

Best regards

Gui Censoni

davevon
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Location: Vero Beach, FL

Re: Repairs, Upgrades and things to look for.

Post by davevon » 05 Mar 2019 05:23

Hi Brian,

The strap hinges are definitely less than ideal. All the surface area and the larger diameter all add up to more friction. My plan if I went to carbon ailerons would be to eliminate the torque tube in the aileron and use self aligning ball bearings. Keeping them lubricated is noticeable in feel.

Your setup is different than mine. Your bushings appear to be nylon or delrin, mine are bronze and indexed to the straps. How much vertical and fore and aft play do your hinges have? Mine had a little and I shimmed it out. Any play can add to flutter. Is there any play spanwise? The bearing at the aileron horn should be controlling that.

With the plastic bushings I would definitely polish the torque tube. Nothing should be rubbing anywhere, not quite sure what's rubbing on yours. I tried to find the best lubricant, looking at all kinds of greases, but in the end ended up using good ole STP. May not be the very best, but is seems to work well. It does migrate well into the hinge and if you don't use too much doesn't drip out.

Dave
aileron hinge.JPG
aileron hinge.JPG (257.35 KiB) Viewed 1146 times

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

Post by boosted180 » 05 Mar 2019 12:07

After a good polishing of the tube and cleaning up the bushings, and applying a lithium based all-purpose grease (only thing I had lying around), I put back the left aileron today. It made a very noticeable difference. On a scale of 1-10 (10 being completely friction free), it was a 3 before and now I would say it's a 6. (for comparison my RV4 feels like an 8.5 or a 9! On the ground, I can easily move the stick with my forefinger and thumb and move the ailerons up and down at the trailing edge with my pinky)

I also sanded down one of the ribs that was rubbing on the torque tube - BUT I ended up sanding down the wrong one!! So next weekend I'll have to take it apart again and sand the correct rib. And finish the other aileron.

Hopefully this will make it acceptable enough so that I can enjoy flying for a while. There's a shop locally who can machine me some brass bushings to use in place of these nylon bushings (or delrin, I'm not sure) . I was told it'll be much better.

BTW, which STP are you talking about for the grease? Apparently they make a few different kinds.

I have zero slop in the hinges. I did find a tiny bit of slop in the rod end links that connect to the torque tube to the pushrods behind the seat. I'd like to replace those if someone here has a part number or can tell me how to search for them. I'll get photos later this week.

I read the Tolve report and from what I understand, the gist of it is to NOT put all the balance weight in the aileron tip counter-balance, but put the bulk of it in the spade, which is a specific distance forward of the hinge-line and inboard of the wing tips, correct? They gave exact numbers in the report, but it's specific to that airplane. Percentage-wise, how do I know how much weight I need in the tip counter balance and the spade? There's two lead plates in each of my spades and it's pretty darn heavy and just by feel, my ailerons are over-balanced (wants to tip forward). I read that you reduced your spade weights. How did you figure how much was safe to reduce?

Thanks for all the great information so far!

davevon
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Location: Vero Beach, FL

Re: Repairs, Upgrades and things to look for.

Post by davevon » 05 Mar 2019 21:45

Brian,

I would make the bushings out of bearing bronze. It's a little harder than brass and in some cases has a porous surface to help contain the lubrication.

The STP I use is the thick engine oil treatment. Back when I was a kid Andy Granatelli did a TV commercial for it :-)

Leon tested several Lasers and found them to all be about the same. The way the wing spar was wedged into the fuse made the biggest difference. His recommendations are very conservative giving the wing/aileron a flutter speed of over 400 mph. His numbers are based on the length of your ailerons. The longer the aileron the greater the weight on the spade arm. If you were to fly it without the spade arm weights I would keep the airspeed less than 140 mph, when I did it I kept it below 120... It was only to test aileron trim prior to spade trimming.

On my aileron linkage I replaced everything with ball bearing rod ends. These are spherical rods that have ball bearings in them, never knew that such an animal existed. All the bolts were replaced with close tolerance NAS bolts. They fit the holes of the rod ends much better. The rod ends are MS21151 and MS21153 See: https://www.gen-aircraft-hardware.com/s ... 167&id=168

I don't recommend reducing your spade weight.

Regards,

Dave

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

Post by boosted180 » 08 Mar 2019 05:45

Ok. Thanks Dave. I have another question. It looks like the rudder strap hinge and bushing are a one-piece deal. There's some slop in the top one. There's no way to service this without cutting the leading edge of the rudder then, right? So I was thinking of cutting a piece of the tube off, sliding the bushing/ strap off, replacing then putting back on and welding a new piece of tube onto the original. Is there a better solution? To me it doesn't seem like a whole lot of slop, but I do want to get it fixed at some point, just not right now. Do you think it's a safety issue with flutter? Apparently it's been flying like this for who knows how long by the previous owners.

https://drive.google.com/open?id=16e9zS ... YieVAAMDiT

https://drive.google.com/open?id=148jLC ... diV9Becnr5

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

Post by davevon » 08 Mar 2019 09:18

That should come apart, at least the strap should come out. I’m on the road so I don’t have pictures available of mine. I did shim the top rudder hinge. I used aluminum can stock as shims and so far so good.

Dave

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

Post by davevon » 09 Mar 2019 22:41

Your hinges look like the earlier welded design. I don't know if there is much you can do with them... I've attached a couple of shots of mine which are of the Pitts - Christen Eagle type.

In looking for more info on strap hinge designs I found a couple of sites of interest.

http://www.2wings.com/m12/faq/tailcontrl/tailcontrl.htm

https://bearhawkforums.com/forum/bearha ... nge-design This one has a tidbit on lubricants that looks interesting.

Regards,

Dave
Strap Hinge.jpg
Strap Hinge.jpg (133.33 KiB) Viewed 1082 times
Hinge setup.jpg
Hinge setup.jpg (230.52 KiB) Viewed 1082 times

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

Post by boosted180 » 10 Mar 2019 07:07

Great idea regarding the aluminum soda can for shimming.

Are your bushings straight bronze or the oilite (oil-impregnated bronze)? How do your controls feel? I saw a video of yours and it looks amazing! If I can get that setup in mine, it would awesome! Do you know where I can buy or custom make bronze bushings to replace my nylon ones? If I can buy the entire setup including straps, and the blocks that goe on the other side of the bushings, that would be ideal.

I called a few places and no luck so far. One guy said he can fabricate some for me, but estimated about $600! And not sure if fit would be exact. The advantage of soft materials like nylon or delrin is that there's a bit of give so if alignment is not precise, it will still fit.

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