Author Topic: Tri-Gear Thoughts – Observations and Minor Modifications  (Read 3003 times)

wafer

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For those of you considering a tri-gear Sonerai, I noticed there is not too much written about construction and what to expect flying.   I am certainly not a tri-gear expert, but offer the following observations as an LTS builder whose been flying for ~ 80 hours. 

Tail dragger vs. Nose wheel Configuration

First, please do not consider the tri-gear only because you do not have tailwheel experience.  In order to get some stick time, and I do suggest you should obtain stick time before flying a Sonerai, chances are you will fly a taildragger.   You will probably find that flying a taildragger is not extremely difficult.  It is more technique to learn, and more tasks to get proficient, but certainly obtainable with time and practice.  Besides sport plane aesthetics (tail draggers do look better), to me the biggest advantage of the tail steering design is less drag.  Also, tail steering is needed if you plan to do grass strip landing.  I am not trying to talk you out of the nose wheel configuration (I love it), just do not discount the tail steering configuration because you have zero tail time. 

The most positive attribute the tri-gear configuration provides a real nice view while ground maneuvering.  And upon landing, you get to enjoy that nice view right after touchdown.  To me, it is the biggest plus for the nose steering design regardless if it is a Sonerai or not.   Some call it a safer configuration; others view it as the modern day standard arrangement.  Insurance companies consider it less risk, and factor that in the premium.  For me, I am just more comfortable with the nose configuration. 

Though some may argue looks, the biggest drawbacks of the nose wheel design is the amount of drag produced, and to a degree weight.  So let’s just say less performance.  How much?  The only way to really make that comparison is with the same aircraft flown in the two configurations. In a March 1983 Sport Aviation article on the tri-gear design, Monnett Experimental Aircraft’s performance testing yielded 2-3 mph lower at top level speed  at 75% cruise.  To date, my experience with top speed has been below expectations.  Not a disappointment, just not as fast as others obtain.  As my plane is a heavy at 650 lbs. empty, and I am another 210 lbs., I am sure there are other factors other than the nose wheel configuration that yield my 125 mph CAS at 24 inches manifold pressure performance.  Maybe I have some more speed tweaks I have yet to discover, but that is my experience to date.   If squeaking the most performance out of your bird is your main goal, maybe the tri-gear is not for you.  Is the tri-gear a “dog?”  Maybe in comparison to a light, powerful Sonerai 1, but otherwise hardly not.  My plane takes my breath away every flight.  Just consider you will lose some performance. 

The other drawback is soft field operations, as soft field is not recommended.  I do not know the details why, just that it is not recommended.  This maybe a show stopper if soft field ops are your normal intentions.

Taxing and Flying the Nose wheel Configuration

In short and per the plans, I have found the Sonerai tri-gear steering is predicable with no bad habits.   Ground handling is smooth and the nose wheel absorbs runway/taxiway anomalies very good (I am using the Sonex spring, which I discuss later).  Flight characteristics are smooth, with the minor exception of when I added a fairing, as I outline below.

The wheelbase is shorter than probably any plane you have flown, and the first few taxi runs you will say that it is quick.  But with practice, you will get use to the quickness and with time, it will be normal for you.  I did a lot of taxing before my first flight, but I would have regardless of nose or tail steering.  Just watch your engine temps if you do.  I found the high speed taxi tests to be very valuable for steering, braking, and alignment testing not to mention getting use to the attitude looking out of the plane when you are on the ground.  This is true for either configuration, just you will need to do the alignment and steering adjustments before the first flight. One easy way to check alignment, taxi down a taxiway line and shut down.  Get out and view your rudder from behind, as it is easy to see if the rudder is out of alignment.  And you want to make sure you do not get a “wobble” from your nose assembly, which is another good reason to perform high speed taxi tests.  For me, it did not happen often, but in my first 20 hours it happened a few times.  It is a light shake that gets stronger until you slow the plane down.  I have found a wobble is attributed to one of three things:  The correct tautness of each steering cable attached to the nose assembly; the nose wheel axle being tight enough to allow the wheel to spin freely, but no looser; the correct nose wheel pressure.

I flew my plane without a nose wheel fairing for the first 40 hours.  I noticed no yaw tendencies caused by the nose wheel.  After adding a nose wheel fairing, I did notice a yaw/handling difference.  It was a distinct yaw to the left, which effected both my rudder pressures during a turn and the need for constant right rudder during cruise.  Bottom line, I adjusted the nose wheel steering cables until I achieved zero rudder pressure required at cruise speed.   All flight maneuvers are now predictable, but there definitely an effect attributed to a nose wheel fairing.  It is not an issue, and maybe it is my specific configuration, but certainly worth mentioning as you may have a similar experience.  Note I am using the “standard” fairing, which looks similar to the one used on the LTS prototype.   

Minor Modifications/Alterations

I built my LTS to plans with very few exceptions.  For the nose wheel assembly, the largest exception is the shock absorbing rubber sleeves.  I used a Sonex nose wheel spring, as I believe most tri-gear Sonerai builders use these days.  I fit it with no alteration to the spring. The spring takes the place of the two rubber sleeves, the aluminum washer between the sleeves, and the tube spacer that are identified in the plans.  I thought I heard John Monnett designed the Sonex spring to also be used on the Sonerai, but I am not sure if that is true.  I will say it fits and performs like it was made for the Sonerai.  You will position the spring on top of the “multiple tube build up” per plans, and secure/weld that “multiple tube build up” so the plane is level after the spring settles.  And when you level the plane, then you know how much of the strut assembly you can cut off for the total length.  This is all per the plans, just substituting the spring for the rubber sleeves.  Note the Sonex spring needs no alteration.  I did buy the rubber sleeves some years back before the Sonex spring was available, and I speculate the rubber sleeves will not perform near as good as the Sonex spring.  For hard surface runways, the spring performs very well and to date I have never experienced the spring “bottoming out.”  It does not have much travel, but evidently does not need much as it is very effective.   

One alteration I recommend is subtle.  It is the location of the compression springs, used in the cable system to control the nose steering and keep the cables taught.  Per the plans, I could not find the proper compression springs small enough to fit in the location attached to the steering head.  Maybe the compression springs available years ago were smaller, but I could not find one that would fit to the steering arm and allow full travel.  I first used tension springs that were short enough to allow the travel.  But the performance allowed for some infrequent oscillation (wobble, as described previously), and upon full tension I was concerned about failure.  So I purchased compression springs through Spruce (P/N 06-15700), and located them at the opposite end of the cable at the passenger rudder.  I have found this location and spring to work fine.   

A modification I strongly suggest concerns the cable length.  I did trial and error with the cable lengths in getting the rudder and the nose wheel to align, per plans. It took me three different lengths in the first 60 hours to get it right. The plans do not call for a turnbuckle (one on each side), but that would allow for some easy cable length fine tuning.  The key word is easy, as opposed to cutting/fitting cables to get the desired length.  After flying some 40 hours, I installed the nose wheel fairing.  I immediately noticed a difference in terms of rudder control in all aspects of flying.  The turnbuckles allow to adjust the cables for overall cable tension and comparative tension between the left and right cable.  I wound up adjusting the cables to “center the ball” in cruise flight.  I would have installed turnbuckles day 1 had I known all of this, and I strongly suggest you consider them.  Grams turns into ounces, and ounces into pounds, so the drawback is weight.  The other option is to cut/fit cables until you get your desired configuration. Look in my gallery (Wafer; 2nd page), and see the pics of the turnbuckles and compression spring locations.

I do have one addition I suggest.  I wanted an ability to easily tow/maneuver the plane by hand per some sort of a tow bar.  I did much investigation looking at how fellow EAAers configured their homebuilts and how some of the kits manufactures outfitted their designs.  I came up a simple addition of two AN490 rod ends added to the fork, located between the axle and the fairing bracket.  The rod ends stay nestled within the fairing, and are used to secure a tow bar for easy handling.  You can chose the size rod end to marry up to whatever size tow bar you desire.  I just leave the tow bar hooked up until I am ready to fly.  I know I have added some drag with the interruption on the front fairing, but the towing ability is really worth it.  Look in my gallery, and see the pics.

Landing

My final comment is about how nice this plane lands.  Upon rounding out after the runway numbers, the plane slowly quits flying and settles upon the runway. It does not float much. Though the landing characteristics are not due to the nose wheel configuration, after the main wheels touch down the nose wheel takes over and you have that nice view I described earlier with good visibility of your surroundings of the entire airport.  I added a YouTube video link below of final approach, landing, and some taxing.  Note the nose wheel touches down just before the runway 1000 foot markers.  My little Mobius camera is located above my head, located 6 inches above my eye height, and 6 inched forward, so what you are seeing is better visibility than what you actually see when flying…but you get a good idea what to expect.

Hope this helps some of you considering or building a nose wheel Sonerai.

Mike “Wafer” Then

https://www.youtube.com/watch?v=HBa6DO284og



Mike "Wafer" Then
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acrojohn

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Wafer,
   Excellent PIREP on the LTS.  I have a little over 100 hrs in an LTS and can confirm just about every one of your characterizations of the design and performance. The LTS I did the Phase 1 testing on was, and still is,   the easiest airplane to land that I have ever flown.  I typically approach at 85-90 mph, over the fence at 80 mph, flare to capture the descent just above the runway and let it settle in when it is ready.  It just settles in like no other airplane. It has never just given up and dropped in like a C-150 being ham-handled.  Also, once down on the mains, the nose can be held off easily with little back pressure to help slow the plane down aerodynamically.  This saves brakes pads and high speed taxiing with the nose wheel on the pavement reducing the opportunity for the shaking you described.
   Most of my time is equally split between tail draggers and tri-gear configured planes.  Forward visibility is highly over-rated.  There is none when my Acro 2 is on the ground.  You adapt by looking elsewhere and using peripheral vision quickly.  While I haven’t flown the Sonerai 2 with a tailwheel, I’d have to offer that the way the plane settles predictably to the runway seems to make it a natural for full stall landing.  Once rolling out, tracking is a matter of educating your feet.  As you stated, it is just a matter of getting proficient with a different technique – not harder.  The Sonerai 2 LTS is just a nice all-around airplane.  I enjoyed reading your report.
John
AcroJohn

sshelo1

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Thank you both, Wafer and John, these pireps are some great motivation and I can't wait to get my S-II back to flying status!!! We need more pilot reports, AND video from all who are flying! I'm sure you know how great it is to see others enjoying their planes and it helps us get out to the hangar/workshop and maintain progress! Thanks again.

Jared in NC
Jared

Thaddeus

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Great posts.  One of my projects is a IILT on gear but that is about it.  I also have a completed and flyable IIL but the turtle is too low, I'm 6'1".  Wafer, does the stretch solve a height issue?  Your photo seems to show you sitting a little close to the top in the IILTS.  Does anyone have experience is "stretching" a IIL or IILT?  BTW, nice plane.
"It seems wisest to assume the worst from the beginning...and let anything better come as a surprise.” 
― Jules Verne, The Mysterious Island

Soneraifred

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The turtledeck height on the II Stretch is 2" higher than the II Original, per the plans.  On my IIL, I raised the turtledeck height 2" to suit my height (I'm 6'-0").  The rule of thumb that I've preached for a long time, is that you can raise the turtledeck height as much as you want, within reason, but you must also raise the height of the vertical tail at least the same amount, so that you retain good rudder control and yaw stability.
Fred Keip
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Pttim

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Excellent write up Mike, I originally built mine as a tri-gear solely because I had no tail-wheel experience I eventually succumbed to pier pressure at the airport and removed the nose-wheel after multiple rides in a cub and subsequently getting my tail-wheel endorsement.  Fred's comment about raised turtle decks,  I have something to contribute about that, but I will do it in another post.
Pttim
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mhflyit

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Great report Mike! Thx
Matt

wafer

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   Thanks to all for the positive comments.

   I hope no one took I was trying to say the LTS is a better plane to land than a tail dragger.  I have never flown a Sonerai tail dragger, but assume it lands virtually the same.  Which is nice!  I was only making observations based solely upon the tri-gear design.

    John – Thanks for the confirmation on design/performance characteristics.  Though built to plans, I often wonder if what I am experiencing is just for my specific Sonerai.  I am about 85 mph over the numbers (still learning to slow down while keeping good final approach visibility), and as you attest this little plane just does not want to float.  I have found my best glide speed to be 85 mph, which I try not to dip below while in the pattern. 

     Thaddeus – Thanks, but I would call my plane a 15 footer (15 feet away, looks good….any closer and you see the flaws!).  As Fred mentioned, the LTS (or LS) plans incorporate 2 more inches in the turtle deck area.  I am 6’1” with a 34” inseam, and find my head pretty close to the canopy.  But we are all different, so you really need to try one on for size.  BTW, the stretch design also adds 18” more in total length to give 6” increased passenger room over the original Sonerai II design.
Mike "Wafer" Then
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Pttim

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No offense taken Mike!  Try 100 over the numbers  it will float for what seems like an eternity! ;D

I imagine they both land the same, very controllable and always exciting.  Dave Wilcox said years ago when I flew with him his best glide was 90, I wouldn't slow down below 85 until on final.
Pttim
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Kevin R.

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FWIW, I fly 100 mph on downwind, 90 mph on base, 85 mph on final and bleed off to 80 mph over the numbers.  I have the Sonerai II wing on an S-1, when I pull the throttle to idle at 85 mph there is no appreciable sink, just a nice glide.  At 90 on the base to final turn I pay attention to keeping the turn well coordinated...with little to no back pressure.

Kevin

jdawg1975

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So as I'm purchasing more material for my plane I need to decide whether to go tricycle gear or taildragger.I have no taildragger experience. Heck I don't have my ppl yet but have tons of training.mostly from running out of money and starting over.this isn't a poor man's hobby.I have 120 plus hours in 172s 150s and Cherokee's.of which have cost me about 7 grand over the years.I really want a taildragger. We have plenty of grass strips here in Florida. In Indiantown we have I believe the biggest one in the us.it's more than 5000 feet if I remember correctly. But I have read some posts from people who claim the sonerai requires significant skill to land as a taildragger. Then other people say it is no big deal.Is it like making a carrier landing or something?Are the controls that touchy your gonna nose it over or groundloop at the slightest mistake or is that exaggerated?  I really need to know because I'm going to start purchasing fuselage materials soon, maybe a tailwheel and spring etc or a sonex spring and hardware for a nosewheel.thoughts please

Jason

wafer

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Jason-

     A simple thought -- if you want to use a grass strip, then do a tailwheel. 

     Sounds like you have made the commitment to build a Sonerai. You will need stick time anyways given your hours in C-152/172/P-140, so add the tailwheel endorsement at that time when getting stick proficient.  Much written on this forum on tailwheel landings, and certainly most Sonerai owners fly a tailwheel configuration.  But I think no one can tell you what is right for you.  Maybe get a few flights now in tailwheel so you can better understand the tailwheel procedures and make your informed building decision.  Like I suggest, you will need to build some stick time regardless, so that will not be wasted flight time.  Ideally, get your stick and tailwheel proficiency sharp before your first Sonerai flight.

    Best of luck!
Mike "Wafer" Then
SII LTS

Pttim

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My suggestion is to build the fusalge with the main gear mounts for both configurations. If you change your mind later it's no big deal to convert it as I did.  If you for nose wheel I still have all the parts for that as I never used mine. Check my gallery you will see the nose wheel.
Pttim
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wbpace

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That's exactly what I did.  The fuselage differences are minor.  There's a couple of extra tubes on the sides of the passenger and pilot areas, and an extra tube on the floor near the firewall. One tube from the fuel tank spider goes to the extra forward tube instead of station 0.

So you will take a minor weight penalty, but you will gain the ability to postpone the decision for a long time (until you mount the gear) as well as be able to convert from one to the other if you don't like your first choice.

I will likely go with the taildragger configuration because I think it looks a lot better.  But who knows?  I might still chicken out and change my mind.  The point is: I can.

O'Bill

jdawg1975

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Thank you everyone for the input, I will make it both ways.I'm pretty confident though after researching that I can learn to land the taildragger safely.Landing was always my strong point, though in tri gear.I always greased them, my instructors used to make me bounce the airplane on purpose to learn how to do a go around.I'm gonna try the tailwheel configuration first.I found an instructor how does eaa webinars close to me with a super decathlon. I hope this is comparable enough to a sonerai .he wants 1500 for a tailwheel endorsement and extra for aerobatics.I just have read a lot of horror story's and it made me concerned but I'll do my best to learn and if it's not for me I can always  go nose gear.Thank you all for your help.Pittm if it doesn't work out maybe I can buy your nose gear .

 

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