Eagler's Nest
Airframes => Single Seaters => Topic started by: Victor Bravo on June 26, 2024, 02:02:26 PM
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Greetings from Southern California,
I bought a single seat Legal Eagle from a guy in Oregon off of a Craigslist ad a few years ago. I gave a good friend of mine in AZ the opportunity to fix it up and get it flying (he had been my sailplane racing ground crew in the 1980's!) But it was too much work for him, he lost interest, and I stored it at his house for a year... and now it's coming back to SoCal for me to take a whack at putting it put back in the air.
I was privileged to have a phone conversation the other day with John Bolding, who was kind enough to share some wisdom, answers, ideas, and encouragement. He is a treasure to the aviation community!
This LE has a very low time full-case Casler half VW, so I am confident in the powerplant.
SEVERAL of the welded parts need to be replaced or re-welded. A few of the welds on the fuselage need to be re-melted. I have someone at my home airport that is qualified and equipped.
There MAY be one or two unofficial and undocumented modifications on this fuselage... he MAY have raised the wing mounting lug higher than stock. Anyone who can verify or de-bunk this please let me know, I'm trying to post a photo showing this.
The woodwork in the wing is a bit sloppy, but appears to be safe. Definitely not a showplane. I'll know more when I peel off the fabric.
There are some mechanical parts that need reworking or re-riveting, I can do that well enough.
The plywood wing leading edges are sagging inward, the original builder did not install foam false ribs. I MAY be able to install false ribs through the lightening holes in the shear web, that remains to be determined. I'd rather not remove the plywood and re-kit the wing.
Thanks for accepting me into the Eagler's Nest group, all advice, experience, etc. is welcome.
Bill in Los Angeles
Victor Bravo on Homebuiltairplanes.com and the Taylorcraft.org forum
(former) EZ Flap on Back Country Pilot forum
1956 Cessna 172
Based at KWHP San Fernando, CA
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Hi Bil, my name is Charles and I have been flying my LEXL at KCMA for 8 years. I am in hangar #21. Hope we can get together next Saturday, July 13 at 11:00 am for our monthly meeting.
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Hi Charles, I have seen your aircraft once or twice when visiting KCMA! I was storing this one in Steve's hangar before it was taken from KCMA to Casa Grande AZ as shown in the photo above.
The meeting you mentioned.... is that the EAA Chapter 723 or the VCUA ultralight club? I may or may not be able to make it, don't know yet.
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I got the Legal Eagle fuselage and wings unloaded from the trailer today and was able to look at the wing mounting. The original builder did something I'm not really happy with. I would like to solicit any opinions, advice, engineering knowledge, etc. from the group.
The original builder installed a 5 inch vertical tube on top of the main upper keel tube to raise the front wing mounting bolt higher. A slightly shorter vertical tube was added on the rear. He welded on some short pieces to "stabilize" the vertical tubes, but these only go part way up the wing mount tubes.
There is no gusset or steel plate support to prevent these vertical tubes from "swaying" side to side under load. This would quickly cause cracks and a total wing mount failure. I'm not any sort of engineer but I paid attention when my engineer friends talked... I really don't like this wing mount system! Does anyone else have this modification on their Legal Eagle?
Photos attached:
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Hi Charles, I have seen your aircraft once or twice when visiting KCMA! I was storing this one in Steve's hangar before it was taken from KCMA to Casa Grande AZ as shown in the photo above.
Normally VCUAS has the membership meeting on the first Saturday of every month but the holliday weekend moves it to the second Saturday which will conflict with EAA normally held on second Saturday of every month.
The meeting you mentioned.... is that the EAA Chapter 723 or the VCUA ultralight club? I may or may not be able to make it, don't know yet.
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I'm not an engineer, but am an A&P and an EAA tech counselor since the 80s.Here's my thought.
It's hard to tell from a picture, but to me it appears that there *may* have been a butt weld extension on the front mount. (!) Certainly the wallared out (Indiana technical term) :) hole at the top is a no no.
If it were me, I'd hack saw it off just below the hole and have a look inside to see just what is going on before deciding how to repair it.
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A retired Lockheed aero and flight test engineer looked at this wing mount today and didn't like it either. So at some point soon, I've got a hot date with a hacksaw and then another date with a welder.
The control stick and aileron control system was also not to my liking. I know that the loads are low, and I know that Leonard wanted to make weight, but there's stuff I just am not going to live with in this system. The aileron "arm" at the rear of the control torque tube sticks straight down under the airplane by 8 inches. Any weeds, brush, plants, etc. on the landing surface will impact and damage that setup. There's thin sheet aluminum and pop rivets that make up the base of the control stuck pivot. There's really thin steel strap bent at an angle into a cable connector, but the strap is loaded in off-axis bending by the elevator cable. I'm going to put a conventional aileron/elevator torque tube and pivot in.
Got some other ideas I'm gonna sketch out and see if they are viable, to simplify, reduce parts count, reduce weight, or make it more robust..
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Your call, of course.. but I've not seen a push pull setup on a LE that I liked better than the simple and lighter cable/pulley arrangement. (shrug) :)
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Well, I'm a little "old school" about primary controls. Secondary controls (throttle, mixture, trim, etc. I am a lot more willing to make sacrifices for cost or weight.
The plans-built control stick on this one has small steel tabs riveted onto the bottom of the stick where the elevator cable nicopress thimbles attach. The tabs have a 90 degree bend in them downstream of where they're riveted. The tabs are really thin as well. So normal elevator control loads pull on the tab, which puts a cyclic load on the bend, as well as putting the single rivet in 100% tension.
Another potential issue is the main aileron "arm" sticks down well below the fuselage, so any weeds, bushes, grass, etc. will try to bend it out of kilter and/or crack the arm. I am 100% aware that this is a high drag slow airplane, but that's not the kind of "drag" I'm worried about.
I'm looking into using the (Kolb style) horizontal aileron arm at the back of the aileron/stick torque tube, with vertical pushrods coming up behind the seat, actuating torque tubes for the ailerons. I can use fairly light weight materials for this, with a weight gain of a pound or so. There will be more weight removed from other areas than the weight which will be added.
A question I have for the group is whether the original "Tuffy" plastic bicycle wheels are robust enough for anything other than perfectly smooth runways. I would like to know if very many people have broken these wheels or not.
Another item is, after reviewing the plans, the upright fuselage tube for the forward spar mount on my airplane is almost 6 inches above the standard plans location. Has anyone else done this? Has anyone done engineering or load calculations on this? It's only the main wing mounting to the fuselage... :)
THANKS in advance to anyone/everyone for participating in this conversation :)
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I would also like to use aileron torque tubes. I've never seen the Kolb system but it sounds simple enough. The kitfox lite also has a push pull cable system that look light.
Jeff
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The Kolb system has rigid push-pull steel or aluminum tubes coming up vertically from the control torque tube. These attach directly to the inboard end of the aileron conrol horn which is riveted into the aileron leading edge tube (serving double duty as the aileron control torque tube). The diameter of the Kolb aileron leading edge is not sufficient for its length in my opinion, and the hinge axis is offset from the torque tube axis... a very clunky and friction-prone design. But thousands of Kolbs are flying so it is 'good enough'.
The system I am sketching out (not set in stone yet!) is about a 2 inch thin wall torque tube that runs just behind the rear main wing spar, through the space in the built-up ribs and through the one round hole in the plywood at the last full length wing rib. A nylon or Teflon bushing will support the tube at this plywood structure.
A riveted control horn (either a light 4130 weldment or a sheet metal riveted assembly) will come down vertically (through the fabric) from the outboard end of this tube, with a short push-pull tube to the aileron horn.
On the inboard end, a similar plywood plate and plastic bushing will support the inboard end of the torque tube, with a similar fabricated arm or horn extending rearward. This plywood support will be glued to the root rib. The vertical pushrods from the aileron control will actuate this control horn.
So the pilot moves the stick. This rotates the aileron control tube under the seat, which rotates the new horizontal aileron arm. The ends of the aileron arm move the rigid vertical pushrods up and down. The pushrods rotate the spanwise torque tubes inside the wing. The outboard horn on this tube rotates fore and aft, pushing or pulling the aileron control rod, which actuates the aileron.
The advantage if this is that it does NOT require any cable tension, which eliminates all built-in stresses or loads on ANY fastener, pulley, bellcrank, fairlead, and control stick. There are no cables to catch on any bushes. There is no 8 inch arm sticking down out of the fuselage.
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An LEU builder made a modification to his fuselage that added some headroom and uses the XL, 2-bolt wing attach method. When we were setting his dihedral it was so much easier to install/remove the wings compared to the LEU single bolt setup.
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VB, take a look at the Cub like controls on the XL. Still light, and gets rid of many of your (and my) concerns.
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Thanks, does anyone have photos of the XL control system handy, for me to look at and compare to what I got? I only have LEU plan set O-53, which is really kinda marginal. I have R/C model airplane plans that are much more complete, detailed, etc. than these.
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Should be quite a few photos in Chuck's Build Log. If you haven't looked through it, you should. It is very thorough.
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I found an online build log for Chris's Legal Eagle XL named Bulldog. It clearly showed the control stick ass'y.
My proposed assembly is a lot more akin to well-established homebuilt designs using push-pull tubes instead of cables:
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Regarding the Tuffy plastic bike wheels. I have no first hand experience but others have shared your concern and it is also my understanding that either they are no longer available or are hard to get. An alternative that many have used is heavy duty BMX wheels in the same size. Many BMX riders are full sized adults and they put all kinds of unique loads on wheels so there has been some development in the industry. The approach is to use a double wall aluminum rim, heavy duty spokes, and a hub that accepts the largest diameter bearings they can find, usually 15mm inside dia. The larger bearings enable a larger diameter axel. The typical number of spokes is 36 for a standard wheel, but 40, 44, or 48 spoke rims may be available and stronger. Also, the more times the spokes cross each other (2x, 3x, 4x) the stronger the wheel. The rims and hubs need to match of course. If you want brakes too then you will need a hub that supports disk brakes. The bolt circle for disk brakes is standard, 160mm disks are the most common and have been reported as more than adequate for a LE. Talk to your local bike shop about what you are doing and what you want. You don't want a wheel set, you want 2 fronts. They won't be cheap.
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I've always wondered about those bike wheels on an aircraft. Bike wheels are not made for much side load while it's not unusual for an aircraft to not be completely straight upon landing (depending on technique). For this reason I'm favoring the Black-Max wheels for my build. On the other hand the bike wheels give more prop clearance. I suspect a 67" prop on a Verner would make this into a big deal but with a 1/2 VW not so much. Alternative would be longer gear legs.
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The design of the gear legs should be based on the intended wheels to be used, so if you are building an LEXL and you want large diameter wheels the gear legs need to be adjusted accordingly. In addition to prop clearance the angle of attack of the wing when on the gear should be a consideration.
WWI vintage airplanes basically used bicycle/motorcycle style spoked wheels. To address side loads the hubs were 2X-3X wider so the spokes formed a wider triangle. If you are willing to design & machine your own hubs you could do the same, I've seen pictures of this in recently built ultralights.
The limiting factor is tire traction on the surface. Landing on grass or dirt the tires can't generate enough grip to overload the rims. Landing on pavement and using light duty rims there have been wheels that have bent. Heavy duty double wall rims, with heavy duty spokes have proven more durable. Bicycles have a standard fork width which limits how wide the hub can be for bicycle applications. If you want to use off the shelf parts the heavy duty parts are the way to go.
Large diameter narrow wheels have several benefits. They have lower rolling resistance, especially in taller grass, so takeoff runs are shorter, the larger diameter is smoother over bumps and irregularities, and of course more clearance for the gear.
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Side load is a peav of mine. There is a youtube video of a LE that experienced probable carb ice from an extended reduced power final approach and a low throttle ride down the runway. At the far end he decided to go around and had to land. The swerve to avoid the fence warped up the Tuff Wheels but the tire stayed on and the wheels were fine. The landing gear had to be rebuilt. Point being the GD plane is supposed to be landed straight and in the first 3rd of the runway. Where are the side loads going to be coming from to bend the rim and peel the tires off? The gear is going to fail first...
https://youtu.be/VIIRW8u8nB8?list=UUopLDNHH_5BR8eBpJgrJfAA&t=30 (https://youtu.be/VIIRW8u8nB8?list=UUopLDNHH_5BR8eBpJgrJfAA&t=30)
https://www.eaglersnest.com/forum/index.php?topic=1823.msg10351#msg10351 (https://www.eaglersnest.com/forum/index.php?topic=1823.msg10351#msg10351)
Search button is your friend...
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Thanks IflyHG & Dan for the responses.
Lots to learn from that video. I'm just a "plans-owner" at this point and yes the Search-box/button has been my friend. There is a lot of meat to find as a newcomer to an active forum. Takes time to sort it all out. Plz be patient.
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It's all good! Dint mean to give a bad/wrong impression. It's that topic in general. There has never been an issue with wheels strong enough to hold up the plane. The Tuffies are still flying today, and bicycles and airplanes were intertwined from the start of aviation... If a plastic wheel is stronger than the landing gear I'm betting just about any adult bicycle spoked wheel is never going to be as issue. There are some cross zero spoked "chopper" bike wheels that may not be suitable however. This is twice for me today I have been on a tear. Think I'll take a nap...
:emoji_u1f600:
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Bullet's double wall BMX wheels have proven to be fine. (so far) :) Many xwind landings, a couple of landing gear tests ::) etc. The very light brakes will hold at a full power runup, believe it or not.
*I don't remember* if I had to turn the axles to fit. Sue me, I'm old.. :)
(https://static.imgzeit.com/large/cbb35d12df9b6844/20230818_065720.jpg)
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Thanks Chuck,
I did a search on "Bullet's double wall BMX wheels" but there were too many results to be useful. Lots & lots of BMX wheels out there. I'm curious about the axle. Do your wheels have sealed bearings and you just used an appropriate sized bolt/stud. Never been a BMX biker so I don't know the tech.
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Check out this link (if it works) https://www.eaglersnest.com/forum/index.php?topic=2197.msg13624#msg13624 (http://"https://www.eaglersnest.com/forum/index.php?topic=2197.msg13624#msg13624"). It shows Chuck making axels to fit the bearings in the hubs.
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Perfect!
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Well.... I was looking at the inside of the wing on my new-to-me LEUL, and I saw something I want to ask the forum brain trust about. I remember reading something on this forum about making sure you do not touch or notch the main spar caps when you're drilling the holes for the aluminum spar root fittings. On at least one of my wings, it appears that the bolt is "perilously close" to the spar, as had been mentioned on another build thread.
Can someone verify whether the bolt location in these photos is or is not in a safe location? I cannot imagine that the hole for this bolt does not "notch" or weaken the upper spar cap underneath the plywood plate.
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Check out this link (if it works) https://www.eaglersnest.com/forum/index.php?topic=2197.msg13624#msg13624 (http:// https://www.eaglersnest.com/forum/index.php?topic=2197.msg13624#msg13624""). It shows Chuck making axels to fit the bearings in the hubs.
The link doesn't work for me... Did you do it like in the "how to post" video?
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I didn't watch the video so probably not. I used the "insert a link" button on the tool bar and then populated the URL and display fields. I had tested the link by copy/pasting it into a new tab to verify it went to the right post. I just tried it from your reply and of course it didn't work for me either. :-\
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Testing.. page 20
https://www.eaglersnest.com/forum/index.php?topic=2197.285
it went right to page 20
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Thanks! Yes. Indeed it did, but it is a materially different link this time compared to the first...
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Can anyone with knowledge please address the structural flight safety question I posted last night, in Post #26 on this thread?
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I just clicked on the link and it also went straight to Page 20.
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The last link works for me the first one sent did not... No big deal.
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Can anyone with knowledge please address the structural flight safety question I posted last night, in Post #26 on this thread?
I'm not an engineer, but there are several pieces of wood coming together right there with plywood gussets essentially making them all one piece.
If that is a L.E the wing spars and ribs are pretty much identical to mini-max and have been tested empirically tested. If it is an XL it was engineered by an expensive licensed aeronautical engineer. Put the hole where the plans say.
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Those photos are of my LEUL that had been built by someone else and reportedly flown. I do not have any opportunity to re-locate the hole without major structural modification.
I am only asking whether this is the same problem that I had read about in one of the previous threads the other day, and if this problem is a known safety risk.
I did not bookmark or note which thread or post, which I now regret.
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Well.... I was looking at the inside of the wing on my new-to-me LEUL, and I saw something I want to ask the forum brain trust about. I remember reading something on this forum about making sure you do not touch or notch the main spar caps when you're drilling the holes for the aluminum spar root fittings. On at least one of my wings, it appears that the bolt is "perilously close" to the spar, as had been mentioned on another build thread.
Can someone verify whether the bolt location in these photos is or is not in a safe location? I cannot imagine that the hole for this bolt does not "notch" or weaken the upper spar cap underneath the plywood plate.
*I know nothing about the LE* but I'd say that it's been flight tested. (shrug) If that is what the drawings say to do, I don't see how you couldn't drill through the spar cap.
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Those photos are of my LEUL that had been built by someone else and reportedly flown. I do not have any opportunity to re-locate the hole without major structural modification.
Dunno about the rest of your question but moving the hole is not a problem. Just plug it with a dowel with epoxy --re-drill. Simple as that.
The Tailwind guys do it this way when the lift strut holes have to be moved in the main spar. The Tailwind is a 200 mph airplane.
I would warm the wood and coat the hole as many times as necessary to let it soak in as much of the epoxy as it will and sand and rinse with distilled water. Same with dowel.
I you like I could try and look up the info from the TW site, but you trust me don't you..?
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I took on a Pitts project one time that had a hole drilled in the wrong place. I did essentially what Dan says, although I ground a couple of spiral grooves around the dowel to keep it from pushing all the epoxy out. It's been aerobatted for 40 years..
VB, maybe what you have read is about drilling into the lower spar cap at the lift strut on the XL?
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THANK YOU all for the replies on this. I'm just trying to be conservative, speaking as a non-engineer and a pilot who has probably used up eight of his nine lives doing a couple too many stupid things in my youth ::)
I looked at the hand drawn plans and it clearly shows the bolt hole to be right on the glue line between the upper spar cap and the heavy diagonal brace, with 1/8" plywood on both sides.
So my initial fear (careless workmanship during the build creating a catastrophic structural flaw) is not valid.
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VB,
One more thought on spar holes...
It goes without saying I guess, but still better said than not...
The absolute last thing you want is to have a hole egged out to let a bolt through...
Dowel it and re-drill the correct size hole in the right place.