Ryan ST Light Sport – Nick Pfannenstiel – Brighton, Colorado

Discussion in 'Member Project Logs' started by 32fordboy, Feb 13, 2017.

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  1. Feb 13, 2017 #1

    32fordboy

    32fordboy

    32fordboy

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    LSA Ryan ST replica, 95% scale

    Thanks for checking out my 95% scale Light Sport Ryan ST replica update thread!

    About 8 years ago, I set out to design a light sport Ryan ST replica. It wasn’t an easy road of learning and researching. This project is going slow, but at least I’m starting to see some kind of progress.

    Some of the desired goals for the airplane are:

    700lbs empty weight
    Stall of no more than 45kts
    70-100 horsepower
    Simple build with only one part requiring heat treatment
    Low build time, all things considered
    Low build cost with automotive or aero engines
    Blueprints must be made for future versions
    And, of course, it must look like a real Ryan ST, aside from maybe minor details. Even though I’m a stickler for absolute realism, I must work within the design parameters.

    Even though it looks like a Ryan ST, no part is the same. I do have blueprints for the real one, but a full size replica would have cost twice as much and is considerably more complex. Complexity adds time, which is something I don’t have a lot of. It is amazing how complex the original Ryan ST is to manufacture. Every time I look at those plans, I am so impressed with what Ryan was able to do back in 1934!

    As it sits, a lot of fabrication has been done. The tail has been riveted together, and nearly all of the weldments have been finished. Cutting and deburring things by hand has taken a very long time, but I am buying a production grade CNC router that can’t get here soon enough. There’s no way I want to cut a bunch of wing ribs by hand! So anyway, there is still a whole lot to do.

    So far, the hardest part has been designing parts for ease of fabrication/ease of maintenance. Design a part, build it, scrap it, re-draw it, rebuild it, scrap it, and on to part #3. As they say, the third time’s the charm.

    I hope you enjoy the updates as much as I have enjoyed re-designing this plane to fit the Light Sport category. Hopefully everything goes well from here on out! If anyone would like to PM me opinions or questions, feel free, as I am always learning and open to new ideas.

    The photos below show some of the completed and nearly completed weldments, my brother in the mockup cockpit (he's also the TIG guy on this project), and the nearly finished fuselage tail cone.

    Stay tuned for periodic updates.

    Thanks!

    Nick Pfannenstiel,
    Long-time forum member/lurker
     

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    Last edited: Feb 13, 2017
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  2. Feb 14, 2017 #2

    32fordboy

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    A few more photos before getting into a more current "log" format.

    One photo shows the first horizontal stabilizer and elevator made. It is overly strong (unnecessarily heavy) and I'm not happy with it, so it will be rebuilt. Note it looks almost identical to a real ST stabilizer, but has been redesigned for this lighter-weight plane.

    Another photo shows the fuselage jig I made. The jig made quick business of hanging and skinning the tail section. Notice the top of the lower skin is not yet flanged. A 10 foot brake was later used to flange the skins as required.

    And the last photo shows the lower rear tail stringers, which serve as an anchor point for the tail wheel shock.

    Nick
     

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  3. Feb 16, 2017 #3

    32fordboy

    32fordboy

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    Well, we got an unexpected surprise today when the freight guy decided to drop off the CNC kit without warning. Needless to say, most of today was clearing out space to build the CNC and trying to manage the hot rod business. Notice here the test bulkheads and other wasted parts made. These parts won't be used. They were just lessons in manufacturing. We went through 3 tail wheel housings, 2 sets of gear treadles, 3 steel bulkheads, and way too many aluminum bulkheads. The flange style on these bulkheads do not reflect the final flange style chosen. We ended up going with flutes and doubled-up bulkheads just like the real ST (thinner material for easier forming). Costly lessons, indeed.

    Nick
     

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  4. Feb 16, 2017 #4

    32fordboy

    32fordboy

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    But, at least something got done today. Torqued the tail wheel bolt, finished making the upper shock mounts, and installed the shock springs. These shocks are not like the original ST. Instead, I opted for a simple spring/rebound spring setup with nylon pucks on either side of the main spring. A little grease and nearly zero maintenance.

    Nick
     

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  5. Feb 17, 2017 #5

    32fordboy

    32fordboy

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    I got a little bit done today on Bulkhead #3 Lower. This lower bulkhead is way different from the original ST, for the sake of manufacturing simplicity. The original ST had a steel tube structure that needed to be heat treated. This is fine and all, but it makes fitment of the stub parts a bit more technical and the steel tube version is way more difficult to jig up.

    The rear stub spar on this little replica was changed to a cantilever spar style, which helped control the loads in a more efficient manner. Because the wings are wire braced, the only substantial vertical load on this rear spar is due to the brace wires pulling the rear landing gear leg upwards. That load is a fair bit smaller than a bending load on a cantilever Piper wing or something similar. In addition, there is a compression load from the wires pulling the rear spar inward.

    The rear stub spars will (hopefully) be done this weekend, aside from maybe priming and final riveting. Notice the unfinished steel wing spar attachments that are on the outboard portion of the spar and the heavy steel reinforcements on the inside portion of the spar. The holes are all undersized right now and will be opened to the correct size once everything is fitted.

    Nick
     

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    Last edited: Feb 18, 2017
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  6. Feb 20, 2017 #6

    32fordboy

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    There hasn't been a whole lot of time the last few days, but a little got done today. All the holes are ready for match-drilling to the correct size and the stub spar's web has been cut. The upper and lower web will have flanges bent into it, hence the excess material above and below the caps. The web stiffeners will be added as soon as the needed material arrives. This whole unit, as-is, weighs 12.75lbs. The green stuff is masking tape to prevent marring the web.

    Nick
     

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  7. Feb 22, 2017 #7

    32fordboy

    32fordboy

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    The last couple of days have been semi-frustrating. Remember the rear wing stub spar from a post above? Add that to the scrap pile. A new design that is easier to manufacture (but very, very similar) is in the works.

    But, at least one assembly got bolted up. This is the landing gear vee, shock fork, and treadle all bolted up. I'll switch out a few bolts to the appropriate size once they get here in a couple of days, but getting this thing together today gave a sense that something might actually be getting done. The rebound spring bolt is too long, but the correct-length bolt can't be ordered until the landing gear shock height is checked with the weight of the airplane on it. The stance has to be perfect, as that is a critical part of the Ryan ST look.

    On to the next one!

    Nick
     

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  8. Mar 7, 2017 #8

    32fordboy

    32fordboy

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    It has been a little while since the last update. Well, the rear stub was slightly redesigned, built, and scrapped yet again. The design itself was fine. However, it was difficult and time consuming to build.

    Because I want to offer kits, things need to be easy and cost effective in the long run, regardless of how many times I have to redo things in the short run. So, the rear stub spar has been redesigned once more. It is now a cross between the original ST design and my webbed design. It should be very easy to build now and the weight is almost identical to the last designs. Sometimes, when looking at pages and pages of your own drawings, doing modifications and crunching numbers as you go, it is really easy to overlook a simple design in favor of a more complex one. This simple design is the one I should have started with. Apparently my eyes had glazed over when I designed the first two rear stub spars.

    As a side note, the CNC kit is really nice! As soon as I get some money I'll order the rest of the router kit. The router table is pictured here, along with what little work was done to Bulkhead 2 (drilling holes).

    Since I have been asked some questions regarding the future of the Ryan ST replica, I decided to start a website and facebook page.

    According to the forum rules, it seems I am allowed to place my website in this thread once or twice, but if I am wrong, please let me know. I will gladly take the link down if it is not allowed. Thanks!

    Nick

    www.timbertigeraircraft.com
    https://www.facebook.com/timbertigeraircraft/
     

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    Last edited: Mar 7, 2017
  9. Mar 24, 2017 #9

    32fordboy

    32fordboy

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    It's been a crazy couple of weeks! We are moving slowly on the rear spar stub, trying hard to make sure this third variation is the final variation. It is now all steel and weighs roughly the same as the aluminum stub spar. Being steel, we can manufacture it faster and be a bit less worried about a builder scratching it. The aluminum spar, while efficient enough for large companies such as Vans, really isn't the best option for my little shop. Note the rear stub spar in the attached photo is nowhere near done.

    Also, we are finishing up some work on the main bulkhead, BH2. Once it is finished, it'll be sent out of state for heat treating. I've heard horror stories about heat treating, but the shop's referral came from another shop here in Colorado who said they didn't have the capacity to do the bulkhead. So, here is to hoping the bulkhead comes back from the heat treating shop in its original shape.

    Who is going to AirVenture 2017? We'll be there with the fuselage on its gear in the Innovation Center. Come say hi!

    Nick
    Timber Tiger Aircraft, Inc.
     

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  10. May 19, 2017 #10

    32fordboy

    32fordboy

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    Things have been going great on this project, now dubbed ST-L, or Light-Sport Trainer. The main bulkhead came back from heat treating in Nebraska and I could NOT be happier with both the quality and service. For what I feel was a very reasonable price, they treated the bulkhead in a vacuum chamber and tested a scrap piece to check the resulting properties. You can see the bulkhead and front stub nearly done in the attached photo. Please disregard the unsightly drip marks on the shop door. We have been getting some awesome spring weather here in Colorado!

    The third BH3 lower/rear stub truss from the post above was scrapped (surprise, surprise) and traded for a fourth, much better, and finalized design (pics to come). The newest BH3 lower is very similar to the Ryan original, except there are no bolted fittings to connect it to the fuselage. The rear stub truss is a permanent part of the airplane now, which allowed us to reduce the weight and complexity considerably. This new steel design weighs a bit less than the once-proposed all-aluminum stub spar.

    Due to some confusion from at least one reader, I will clarify here: the main wing spars are NOT a steel truss! This steel truss is for the rear stub spar only. The main spars are a traditional I-beam. We've weighed the pros and cons of wood vs aluminum and ended up going with aluminum for a few reasons, at least on the prototype. Wood spars may be investigated further in the future.

    We are working diligently to make Oshkosh in late July and plan on having the fuselage there on its gear in the Innovation Center. As of now, we are getting caught up and have no major concerns about the deadline.

    More pics to come once the remaining steel parts are painted. Kit assemblies will likely be powder-coated.
     

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  11. May 19, 2017 #11

    32fordboy

    32fordboy

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    I just realized how tiny the fuselage looks in the above photo. The cockpit width around the center of the craft is about 3/8" wider than an original ST. Shoulder width is fine for me...a bit of comfortable wiggle room with my 19.5" shoulder span. I have wide shoulders for someone with my build, but understand some people have extremely wide shoulders.

    The shoulder width could be increased by about 2" if one were to use PT-20 style longerons. No doubt the Ryan is known for its smallish cockpit, but there are options for people with larger shoulder spans, including a slightly dropped seat, which would push the pilot's body further into the wider portion of the cockpit.

    I'm also entertaining the idea of offering a wide-body fuselage, but that is still up in the air, as it would change a LOT of the tooling required to make bulkheads, particularly the complex steel main bulkhead.

    Nick
     
  12. Jun 25, 2017 #12

    32fordboy

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    So much has been done since the last post. Seat structures built, new rudder pedals with toe brakes designed and built, the longerons finished up, the fuselage re-hung on the jig, seat belt attachments designed and built, the control system re-worked for simplicity, the elevator idler designed and built, designed the fuel-tank strap setup, and now we are ready to start skinning the fuselage. I've got 3 weeks to get the skins hung, drilled, pulled, deburred, primed, re-hung, and riveted. But no pressure, right? And then after that, I still have to install the seat bottoms and seat backs.

    I also did some drawings with the cowl, and it seems a Rotax 912 WILL fit with no effect on appearance IF I can use an 8" prop extension on it. The biggest extension I can find online is 6". Does anybody here know if an 8" extension will work? If so, please PM me regarding the issue. Thanks!
     

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  13. Jul 17, 2017 #13

    32fordboy

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    Getting there!

    One thing I am starting to learn is that Ryan STs were lumpy, bumpy airplanes. Looking through historical photos, you quickly understand that Ryan wasn't making show planes. They were trying to manufacture as many as possible, as cost-effectively as possible. I wasn't happy with the "puckers" around the rivets, but upon comparing them to real Ryan STs, that's just the way they were. Being in the show car industry, it bothers me, so I'm going to massage the metal a bit after Oshkosh. It is pretty easy to get the puckers out, just time consuming. BUT, it'll totally be worth it.

    The skinning process was difficult. Every part of this plane has been cut by hand, and that means every hole was drilled by hand. The kits will be computer cut, more than likely set up for easy match drilling, and I am desperately looking for ways to tweak the fuselage construction process in a way that allows jig-free assembly. Essentially, future builders won't have to endure the headaches I did. I want this plane to be something a beginner can build, so any ideas are welcomed.

    We should still be able to make Oshkosh as planned this year. That is, with the plane on the landing gear. The gear should be hung today or tomorrow, then I can focus on getting the headrest installed (hopefully). Then the seat bottoms and seat backs...I'm starting to realize how much is left to get done in four days, so...out to work!
     

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  14. Aug 4, 2017 #14

    32fordboy

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    Oshkosh was crazy, but we made it back alive. We didn't even back the trailer into anything! The rear seat on the ST-L now needs to be removed and finished, the front seat built, the rudder pedals modified for greater passenger clearance, and the wing stub drag truss needs installed (a few observant people at AirVenture noticed the missing drag truss).

    We were able to confirm the inside IS indeed more spacious than even an original STM (the STM has the longerons on the outside) and the plane will fit someone at least 6'5" tall, potentially even taller.

    More build progress to come in the weeks ahead. We now have a goal of getting this thing done by next AirVenture. I hear the snickers already, but at least we have a goal.
     

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  15. Oct 5, 2017 #15

    32fordboy

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    Progress on the actual construction of the ST-L has slowed a bit since AirVenture. But the designing hasn't stopped. Taking feedback from Oshkosh, it was time for a short break to fine-tune the design with larger customers in mind.

    We already knew the plane would fit someone of 6'5" comfortably. We also know that despite the 95% scale, the cockpit of the replica is roomier than an original ST-M. To give more margin for comfort, we redesigned the rudder pedals and modified the forward cockpit.

    We also finalized the shoulder harness attachments (the original ST didn't have shoulder harnesses, but the ST-M did). The baggage capacity has been fine-tuned, as well. This plane is going to have FOUR options for baggage, depending on the engine used. The main baggage compartment is VERY large for a tandem plane so compact.

    Though construction has slowed since Oshkosh, we have made AWESOME headway, including a few things we can't yet publicly discuss. With some design work finalized, we can now move forward with more construction.

    And one last thing: the CNC machine is done! All we have to do is hook it up to the computer.

    Here are photos of the instrument panel blank and the front seat back. The tabs on the instrument panel will be behind the panel once permanently installed.
     

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  16. Nov 1, 2017 #16

    32fordboy

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    IMG_20171012_134613303.jpg IMG_20171025_164140954.jpg IMG_20171028_173329301.jpg IMG_20171030_154549036.jpg A lot has been done in the last few weeks. With AirVenture 2018 just around the corner (so it feels), we have every day until then planned out on the calendar. In the last few weeks, we got the front seat back installed, the forward baggage compartment mostly built, the fuel tank shape finalized, a 1/6 scale cowling test mockup started (yes, that is a Rotax 912 in there), and the new/improved horizontal stabilizers started. The stabilizer ribs were pressed and fine-tuned by hand. Just like other kits on the market, we plan on pressing the ribs and the builder will fine-tune them (about 3 minutes per rib). In the coming weeks, plan on seeing the stabilizers completed and the cowling test finished.
     
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  17. Nov 14, 2017 #17

    32fordboy

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    It was a busy week getting the CNC up and running in addition to fitting the horizontals to the fuselage. I wouldn't say it was difficult to fit the elevator and get hinge alignment just right, but it did take some slow work and attention to get it right. The upside of this aluminum stabilizer set up (vs. steel tube) is the look of originality and weight savings. The downside is that it takes a bit more time. But the results are totally worth it. I just love it when stabilizers have a nice symmetrical airfoil look, as opposed to being a flat slab.

    A lot of the stabilizer parts must be drilled by hand on assembly to get a perfect "to-the-airplane" fit. The root attachment bolts, hinge tube bolts, wire reinforcement, etc. It takes a steady hand, a good eye, and lots of drill bit size stepping up to the final reaming size. While you can get good results if you work slowly, I'd like to find a better technique for those who prefer an easier/faster method. If you have any ideas, feel free to let me know.

    Here is a video of the CNC doing its job on some early tests. It is cutting out the torque tube clamps.

    https://www.youtube.com/channel/UCzSD0h_Uz532L9rGxJY845g
     

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  18. Nov 29, 2017 #18

    32fordboy

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    It's really starting to look like a plane! It is also looking much larger and more robust. There is still a small amount of work to do to the tail surfaces, but they are nearly done. One may notice a slight difference in the tail surface hinges. The horizontal hinges are similar to those found on many planes of the era. A friend suggested going with safety straps on the hinges, which you'll see on the verticals here. The safety straps will be standard on all hinges once kits start rolling off the line.

    In other tail-related news, I've decided it would be a good idea to start a weight analysis on welded steel tail surfaces for those who might want a pre-built setup. The steel surfaces would be quite a bit heavier (by about 8 lbs), so we won't know if it is possible until we can test fly the prototype, checking for aft stability.

    Anyhow, I thought it was a good time for a photo update now that the verticals are on the plane. Some time in the next month or two, I'd like to push the plane outside and do a short video walk-around.
     

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  19. Jan 17, 2018 #19

    32fordboy

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    A lot has been done in the last several weeks.

    The optional forward baggage compartment and fuel tank design have been finalized. The aim for this replica is to have a higher useful load than the original. To utilize that useful load for baggage, the tank and baggage compartment are very much related to each other. It's the odd shape of the tank that allows the huge area above it. The current estimate is a full week's worth of clothes and toiletries for two people, but we'll know more once the tank is installed permanently. If I end up installing the optional rear baggage behind the front seat, the baggage capacity will be HUGE.

    This void above the tank also allows an optional expanded fuel range if the forward baggage compartment is shortened. And for the record, the fuel tank does sit behind a firewall, though the picture seems to suggest otherwise. Not pictured in the photo is the fuel tank sump, which prevents fuel starvation in any flight attitude and keeps water at a low point when the plane is parked.

    We also managed to figure and install the wing stub's drag truss. You'll notice the drag tube is reversed from the factory ST. This was done to control the landing loads in a manner that is more efficient. In addition, the complicated compression struts of the original ST were deleted. The compression assembly was replaced by a heavy tube at the top of the landing gear V. Again, all part of seeking that design efficiency.

    Lastly, you'll notice the wings have been started. These wings are a departure from the originals, which had wood spars and other differences that will be covered in a future post.
     

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  20. Jan 30, 2018 #20

    32fordboy

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    It has wings!...kinda. Getting the wing structure trued-up on construction had me very nervous. What if the wing panel wasn't drawn square on the table, despite my best efforts? What if I somehow messed up the fuselage and didn't get that square? Would I need to compensate in the wing structure to bring things back into alignment? What if I mis-reamed the bolt holes for the root attachment during assembly? Checking and re-checking everything for squareness, it was decided the wings could be built square on the table per the plans. Not only was it easy, but it worked! Everything is essentially square once mounted to the fuselage. At least so close that the air won't care, and neither will the eye.

    I have to mess with adjusting the right wing stub a bit tomorrow, but everything is looking really good so far. We're aiming to have an order for wires placed by the end of the week. Since the wires are custom-built, there is no room for error in measuring.
     

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