Custom 3D Printed FT Commuter

[TaylorRAmes]

Hello all! I just finished up "version 1" of my custom FT Commuter build, so I decided I'd share some of my journey with all of you. This project started just over a year ago when I bought my FT Commuter kit...or at least when I tried to buy the kit before I got an email saying it had been discontinued. I liked Cessna aircraft and desperately needed a trainer after crashing my first two Mini Mustangs, so I wasted no time heading to the dollar store and getting supplies to build my own Commuter. Three days, a cut thumb (unrelated), and lot of scrap foam later, I finally had the trainer of my dreams. It flew beautifully, but one thought kept going through my mind.
This is going to be a pain in the butt to rebuild if I crash it.
So, with a student license of Fusion 360 and 6 months left of school (Mech. Eng. Student, Graduated in Dec 2023), I made it my goal to 3D model the entire plane so I'd never have to hand cut the nose again.
The first version of the nose took heavy inspiration from the foam kit, keeping the same lines, making use of a 3d printed motor mount, and completely disregarding the battery. Whoops. After correcting my mistake and adding some skewer holes to help align it to the plane, I hot glued it in place and took it out for its first maiden. It flew wonderfully, but what was before a modest task of transferring the design now became a red hot fury of new ideas, concepts, and features I wanted to add. I mean, I'm already going to be modelling the whole thing, I might as well do some designing of my own.
I redesigned the nose again to remove the powerpod, remove the hard lines from the foam model, and add nose wheel steering - automatic 10/10 upgrade. Then I began working on the wing. I had a video explaining the evolution of the wing, but since I can't post that here, I'll do a quick explanation of the four versions of the wing.

Each wing was loosely based on the dual airfoil design most small FT planes have - a normal airfoil (Clark Y), and a high drag, high lift airfoil at the wing tips (Some STOL NACA airfoil, don't remember which one). The airfoil was constant until midspan of the wing where it gradually transitioned to a higher lift airfoil at the tip. I also added flaps that spanned half the wing, increased the wing span by 2in, and had integrated servo mounts.

Wing V1: 1 central skewer in each wing, 2 skewers holding the two halves together and setting the dihedral. Mounts for the skewers were molded into the 3 spars which ran the entire length of the wing. It was 5 pieces, held together by superglue and the skewers, and was hot glued to the foam fuselage. This design was extremely strong, but lacked rigidity at the trailing edge where the control surfaces mount and was very heavy at >200g for the completed wing.

Wing V2: Added 1mm x 1mm crisscross reinforcing lines to the upper and lower skins to help increase rigidity at the TE. Still heavy, still weak.

Wing V3: Ditch the crisscross reinforcements, add ribs at each of the wing joints (4 total) to increase rigidity. This is the first version of the wing that flew. During a test flight, the plane was extremely hard to fly and barely made it safely onto the ground. I determined the new wing tip profile and heavy weight were both to blame - These areas were both addressed in the V4.

Wing V4: Complete redesign. I got an engineering job at an aircraft company, so I decided I wanted to use a more traditional design and use this plane as an opportunity to learn and practice new analysis techniques. I switched to a 3 section wing with two outer ribs and 1 large central rib, switched from integrated spars split at each wing section to a single, continuous spar running through each wing half, and now I'm using the continuous spar, central rib, and wing skins to provide the strength instead of the skewers. I also modified the servo hinges to use actual hinges instead of TPU and made the parts printable without support. Finally, I added the strut mount and calculated the stress reduction and new critical location the strut would provide.

This new wing design was weaker than before, but using actual aircraft wing analysis techniques, I designed it to take a 25G load when printed using prefoamed LW-PLA. I ended up printing the plane using Esun foaming LW-PLA which is much lighter and weaker, so the version I will actually be flying is significantly weaker. I am taking this opportunity to learn some fiberglassing techniques, but I don't expect to need that extra strength considering this is my trainer. I know how to fly, but you get the idea. It won't be doing any acrobatics. Not yet... : )

Next up was the fuselage. I made some mistakes while modeling this (Bad constraints, bad projections, oversights, etc), so I will be completely redesigning this in the future. It's pretty similar to the foam version, just with some added reinforcing frames, screw mounting holes for the nose, wing, and tail, and a strut mount. I did do the math to see what kind of loads the fuselage will see, but I am not going to waste time trying to reinforce this version. The fuselage will split in two during a hard landing and will be ripped in three during a 25G maneuver. Moving on, lol.

The tail is relatively simple - it consists of a tail boom with some integrated reinforcements, locating pins, and screw mounts for the fuselage, a stabilizer fitting where the H-stab and V-stab mount and control wires run through, and the control surfaces. Although its simple, this is the part of the plane I am mose pleased with. The H-stab is locked in place by the V-stab, the V-stab is held in with 2 screws, and the whole assembly glues perfectly into the tail boom. Simple, elegant, and very strong. It also looks gorgeous!

You can tell I got tired of writing near the end, lol. It's definitely not perfect, but when is a "Verison 1" ever perfect? You can probably see why I keep putting that in quotes. Between all the redesigns and individual parts, there have been over 350 total revisions made to this assembly, and I have spent 4 rolls of filament experimenting with the design. If anything interesting happens during the maiden of the fully 3d printed design, if I reach a milestone in the redesign, or if I remember an interesting part of the development process that I missed, I will post an update here.
Edit: Added 6 more screenshots of the V1 3D model.
Edit #2: Added 2 pictures of the V2 and V3 wing designs

 

[bisco]

well done. great write up, thanks!

 

[Morgan G]

Hello all! I just finished up "version 1" of my custom FT Commuter build, so I decided I'd share some of my journey with all of you. This project started just over a year ago when I bought my FT Commuter kit...or at least when I tried to buy the kit before I got an email saying it had been discontinued. I liked Cessna aircraft and desperately needed a trainer after crashing my first two Mini Mustangs, so I wasted no time heading to the dollar store and getting supplies to build my own Commuter. Three days, a cut thumb (unrelated), and lot of scrap foam later, I finally had the trainer of my dreams. It flew beautifully, but one thought kept going through my mind.
This is going to be a pain in the butt to rebuild if I crash it.
So, with a student license of Fusion 360 and 6 months left of school (Mech. Eng. Student, Graduated in Dec 2023), I made it my goal to 3D model the entire plane so I'd never have to hand cut the nose again.
The first version of the nose took heavy inspiration from the foam kit, keeping the same lines, making use of a 3d printed motor mount, and completely disregarding the battery. Whoops. After correcting my mistake and adding some skewer holes to help align it to the plane, I hot glued it in place and took it out for its first maiden. It flew wonderfully, but what was before a modest task of transferring the design now became a red hot fury of new ideas, concepts, and features I wanted to add. I mean, I'm already going to be modelling the whole thing, I might as well do some designing of my own.
I redesigned the nose again to remove the powerpod, remove the hard lines from the foam model, and add nose wheel steering - automatic 10/10 upgrade. Then I began working on the wing. I had a video explaining the evolution of the wing, but since I can't post that here, I'll do a quick explanation of the four versions of the wing.

Each wing was loosely based on the dual airfoil design most small FT planes have - a normal airfoil (Clark Y), and a high drag, high lift airfoil at the wing tips (Some STOL NACA airfoil, don't remember which one). The airfoil was constant until midspan of the wing where it gradually transitioned to a higher lift airfoil at the tip. I also added flaps that spanned half the wing, increased the wing span by 2in, and had integrated servo mounts.

Wing V1: 1 central skewer in each wing, 2 skewers holding the two halves together and setting the dihedral. Mounts for the skewers were molded into the 3 spars which ran the entire length of the wing. It was 5 pieces, held together by superglue and the skewers, and was hot glued to the foam fuselage. This design was extremely strong, but lacked rigidity at the trailing edge where the control surfaces mount and was very heavy at >200g for the completed wing.

Wing V2: Added 1mm x 1mm crisscross reinforcing lines to the upper and lower skins to help increase rigidity at the TE. Still heavy, still weak.

Wing V3: Ditch the crisscross reinforcements, add ribs at each of the wing joints (4 total) to increase rigidity. This is the first version of the wing that flew. During a test flight, the plane was extremely hard to fly and barely made it safely onto the ground. I determined the new wing tip profile and heavy weight were both to blame - These areas were both addressed in the V4.

Wing V4: Complete redesign. I got an engineering job at an aircraft company, so I decided I wanted to use a more traditional design and use this plane as an opportunity to learn and practice new analysis techniques. I switched to a 3 section wing with two outer ribs and 1 large central rib, switched from integrated spars split at each wing section to a single, continuous spar running through each wing half, and now I'm using the continuous spar, central rib, and wing skins to provide the strength instead of the skewers. I also modified the servo hinges to use actual hinges instead of TPU and made the parts printable without support. Finally, I added the strut mount and calculated the stress reduction and new critical location the strut would provide.

This new wing design was weaker than before, but using actual aircraft wing analysis techniques, I designed it to take a 25G load when printed using prefoamed LW-PLA. I ended up printing the plane using Esun foaming LW-PLA which is much lighter and weaker, so the version I will actually be flying is significantly weaker. I am taking this opportunity to learn some fiberglassing techniques, but I don't expect to need that extra strength considering this is my trainer. I know how to fly, but you get the idea. It won't be doing any acrobatics. Not yet... : )

Next up was the fuselage. I made some mistakes while modeling this (Bad constraints, bad projections, oversights, etc), so I will be completely redesigning this in the future. It's pretty similar to the foam version, just with some added reinforcing frames, screw mounting holes for the nose, wing, and tail, and a strut mount. I did do the math to see what kind of loads the fuselage will see, but I am not going to waste time trying to reinforce this version. The fuselage will split in two during a hard landing and will be ripped in three during a 25G maneuver. Moving on, lol.

The tail is relatively simple - it consists of a tail boom with some integrated reinforcements, locating pins, and screw mounts for the fuselage, a stabilizer fitting where the H-stab and V-stab mount and control wires run through, and the control surfaces. Although its simple, this is the part of the plane I am mose pleased with. The H-stab is locked in place by the V-stab, the V-stab is held in with 2 screws, and the whole assembly glues perfectly into the tail boom. Simple, elegant, and very strong. It also looks gorgeous!

You can tell I got tired of writing near the end, lol. It's definitely not perfect, but when is a "Verison 1" ever perfect? You can probably see why I keep putting that in quotes. Between all the redesigns and individual parts, there have been over 350 total revisions made to this assembly, and I have spent 4 rolls of filament experimenting with the design. If anything interesting happens during the maiden of the fully 3d printed design, if I reach a milestone in the redesign, or if I remember an interesting part of the development process that I missed, I will post an update here.
Edit: Added 6 more screenshots of the V1 3D model.
Edit #2: Added 2 pictures of the V2 and V3 wing designs

this is incredible, great job!

 

[FlyerInStyle]

Hello all! I just finished up "version 1" of my custom FT Commuter build, so I decided I'd share some of my journey with all of you. This project started just over a year ago when I bought my FT Commuter kit...or at least when I tried to buy the kit before I got an email saying it had been discontinued. I liked Cessna aircraft and desperately needed a trainer after crashing my first two Mini Mustangs, so I wasted no time heading to the dollar store and getting supplies to build my own Commuter. Three days, a cut thumb (unrelated), and lot of scrap foam later, I finally had the trainer of my dreams. It flew beautifully, but one thought kept going through my mind.
This is going to be a pain in the butt to rebuild if I crash it.
So, with a student license of Fusion 360 and 6 months left of school (Mech. Eng. Student, Graduated in Dec 2023), I made it my goal to 3D model the entire plane so I'd never have to hand cut the nose again.
The first version of the nose took heavy inspiration from the foam kit, keeping the same lines, making use of a 3d printed motor mount, and completely disregarding the battery. Whoops. After correcting my mistake and adding some skewer holes to help align it to the plane, I hot glued it in place and took it out for its first maiden. It flew wonderfully, but what was before a modest task of transferring the design now became a red hot fury of new ideas, concepts, and features I wanted to add. I mean, I'm already going to be modelling the whole thing, I might as well do some designing of my own.
I redesigned the nose again to remove the powerpod, remove the hard lines from the foam model, and add nose wheel steering - automatic 10/10 upgrade. Then I began working on the wing. I had a video explaining the evolution of the wing, but since I can't post that here, I'll do a quick explanation of the four versions of the wing.

Each wing was loosely based on the dual airfoil design most small FT planes have - a normal airfoil (Clark Y), and a high drag, high lift airfoil at the wing tips (Some STOL NACA airfoil, don't remember which one). The airfoil was constant until midspan of the wing where it gradually transitioned to a higher lift airfoil at the tip. I also added flaps that spanned half the wing, increased the wing span by 2in, and had integrated servo mounts.

Wing V1: 1 central skewer in each wing, 2 skewers holding the two halves together and setting the dihedral. Mounts for the skewers were molded into the 3 spars which ran the entire length of the wing. It was 5 pieces, held together by superglue and the skewers, and was hot glued to the foam fuselage. This design was extremely strong, but lacked rigidity at the trailing edge where the control surfaces mount and was very heavy at >200g for the completed wing.

Wing V2: Added 1mm x 1mm crisscross reinforcing lines to the upper and lower skins to help increase rigidity at the TE. Still heavy, still weak.

Wing V3: Ditch the crisscross reinforcements, add ribs at each of the wing joints (4 total) to increase rigidity. This is the first version of the wing that flew. During a test flight, the plane was extremely hard to fly and barely made it safely onto the ground. I determined the new wing tip profile and heavy weight were both to blame - These areas were both addressed in the V4.

Wing V4: Complete redesign. I got an engineering job at an aircraft company, so I decided I wanted to use a more traditional design and use this plane as an opportunity to learn and practice new analysis techniques. I switched to a 3 section wing with two outer ribs and 1 large central rib, switched from integrated spars split at each wing section to a single, continuous spar running through each wing half, and now I'm using the continuous spar, central rib, and wing skins to provide the strength instead of the skewers. I also modified the servo hinges to use actual hinges instead of TPU and made the parts printable without support. Finally, I added the strut mount and calculated the stress reduction and new critical location the strut would provide.

This new wing design was weaker than before, but using actual aircraft wing analysis techniques, I designed it to take a 25G load when printed using prefoamed LW-PLA. I ended up printing the plane using Esun foaming LW-PLA which is much lighter and weaker, so the version I will actually be flying is significantly weaker. I am taking this opportunity to learn some fiberglassing techniques, but I don't expect to need that extra strength considering this is my trainer. I know how to fly, but you get the idea. It won't be doing any acrobatics. Not yet... : )

Next up was the fuselage. I made some mistakes while modeling this (Bad constraints, bad projections, oversights, etc), so I will be completely redesigning this in the future. It's pretty similar to the foam version, just with some added reinforcing frames, screw mounting holes for the nose, wing, and tail, and a strut mount. I did do the math to see what kind of loads the fuselage will see, but I am not going to waste time trying to reinforce this version. The fuselage will split in two during a hard landing and will be ripped in three during a 25G maneuver. Moving on, lol.

The tail is relatively simple - it consists of a tail boom with some integrated reinforcements, locating pins, and screw mounts for the fuselage, a stabilizer fitting where the H-stab and V-stab mount and control wires run through, and the control surfaces. Although its simple, this is the part of the plane I am mose pleased with. The H-stab is locked in place by the V-stab, the V-stab is held in with 2 screws, and the whole assembly glues perfectly into the tail boom. Simple, elegant, and very strong. It also looks gorgeous!

You can tell I got tired of writing near the end, lol. It's definitely not perfect, but when is a "Verison 1" ever perfect? You can probably see why I keep putting that in quotes. Between all the redesigns and individual parts, there have been over 350 total revisions made to this assembly, and I have spent 4 rolls of filament experimenting with the design. If anything interesting happens during the maiden of the fully 3d printed design, if I reach a milestone in the redesign, or if I remember an interesting part of the development process that I missed, I will post an update here.
Edit: Added 6 more screenshots of the V1 3D model.
Edit #2: Added 2 pictures of the V2 and V3 wing designs

do you think this would work from just regular pla? or abs? also what do you think of doing a foam and 3d printed version, where like 3d printed formers so the foam is perfectly ing the right shape, with foam skins for lightweight

 

[FlyerInStyle]

also could I get the files for this? sorry if I missedd you saying where they were in your writeup

 

[TaylorRAmes]

do you think this would work from just regular pla? or abs? also what do you think of doing a foam and 3d printed version, where like 3d printed formers so the foam is perfectly ing the right shape, with foam skins for lightweight

Due to some of the additional stiffeners/supports I added to compensate for the very soft foaming LW-PLA, a full-PLA or ABS print with this exact design would be too heavy to fly well. Additionally, due to some mistakes and modifications I made when mapping out the basic fuselage profile, it would be exceedingly tail-heavy with no room to shove the battery forward.
I hadn't considered using foam in the construction in the past. The initial goal of this plane was to be fully 3D printed, so I wanted to stick with traditional designs. However, following the crash of this plane during it's maiden flight (spoilers, update coming soon), I am considering experimenting with small-diameter carbon fiber rods and 3d printed bulkheads to form the general shape of the fuselage.

 

[TaylorRAmes]

also could I get the files for this? sorry if I missedd you saying where they were in your writeup

This design is nowhere near ready for distribution - a fact that was made clear during the maiden flight and subsequent test flights using the fiberglassed wing (More spoilers, only the wing survived on account of it being fiberglassed and the fuselage being hilariously flimsy. I REALLY rushed it). To satisfy my urge to fly, I have redesigned the wing to utilize a carbon fiber spar and will be testing it out on my modified Mini Guinea, but if it flies well, I have a plan to convert it back into a fully 3D-printed design.
As for the fuselage, I will be experimenting with the bulkheads and carbon rods as mentioned in the previous reply, and I will in all likelihood adopt a similar design scheme to the new wing - assemble the substructure and then glue/fasten on the skins (SO MANY SPOILERS).
A big issue I need to tackle is whether or not I will be gluing the wing and fuselage skins to the substructure (ribs and frames). No glue means its easier to assemble and repair, but unless I use lots of screws, I can't rely on the skin for strength (heavy). Maybe I'll glue individual skin sections together and only use screws as the major joints (Outbd and inbd wing, nose, fuse, tail). Thats fine for the nose, fuse, and tail, but if I design the wing to have a monolithic spar and rib design like I had intended for the 3D printed version, that would mean each half of the wing would be one piece like the previous designs. Perhaps I could split the wing near the strut mount and fasten the outbd portion. This would make it easier to print, but under the 25G load, the attachment fasteners would need to take 15+ lb of force. Not impossible, but it is a potential point of failure, especially due to the repetitive cycling from the aileron and any wing tip strikes during normal taxi.
This post was originally meant to be two lines long, lol. Now you can see why I haven't yet provided an update - far too many questions I need to answer first.
TL;DR: I anticipate the new design will be suitable for distribution, but I have a lot of work to do before then.

 

[TaylorRAmes]

Summary of events since the original post
Oct 6:
Maiden flight of the completed plane. I had some issues with my 3D printer, so the nose was printed from PLA. Other than some beefed-up mounting lugs, it was identical to previous designs. I started this project by designing the nose, so most of its issues had already been ironed out. I accidentally broke the tail boom and cracked one of the tail-fuselage attach lugs during assembly (hence the beefier lugs being tested on the nose), so rather than waiting, I added a layer of fiberglass over this section. The wing also has a single layer of fiberglass since it wasn't designed for the weaker Esun LWPLA.
I took the plane out for its maiden flight, but I was already noticing numerous potential issues. First, I moved the nose wheel mount backward in a previous revision, so I couldn't move my battery far enough forward to get a slight nose-down CG - it was about level, if not slightly tail heavy. I also forgot to adjust the nose gear, so I had to add a lot of right rudder and right trim during takeoff. Finally, I knew the tail geometry was off. The horizontal stab was angled down a few degrees in the model relative to the horizontal plane, but I forgot the wing was also angled slightly up.
All of these errors meant I now had a tail-heavy plane with very pitch-down authority and an excessive amount of left rudder immediately after takeoff. The plane struggled to gain lift due to the high weight, pitched to a high angle of attack once it was airborne, and then stalled the right wing when I tried inputting left aileron to correct the roll from the excessive rudder. This resulted in the plane falling 8ft in an inverted dive towards the ground, completely destroying the fuselage, snapping the vertical stab, and cracking the aileron and flap mounts on the wing (though not enough to prevent future flights). The only part of the fuselage to survive was the torque box created by the gear mount, receiver mount, and tailboom bulkhead. Had it not been for the fiberglass repair, the tail would have been ripped off as well.

Nov. thru Dec:
I strapped the wing to my Mini Guinea with some hot glued motor mounts and took it out for a flight. The wing flew alright (some tip stall tendencies, but I expected this), and survived more than a few "oh crap" moments where I was diving towards the ground and added full power and full elevator to avoid crashing. I did snap the center carry-thru in half on my first landing, but that's because I strapped the struts together with rubberbands on the first outing. That meant the provided zero support in compression, so the weight of the motors snapped it upon landing. I hot glued a new strut mount to the fuselage to fix this and flew the plane a few more times until l stalled the wing high up, entered a diving spin, and was not able to recover. The plane landed primarily on its nose and wing tip. This crash wound up severely cracking multiple control surface mounts to the point where they either won't stay in place or would surely rip the wing skin during flight, so I've decided to retire the fiberglassed V4 wing for good. I do plan on performing a destructive test of the wing to see if my calculations match the actual strength.

Dec. 15 thru Dec 26:
I redesigned the wing again to add proper ribs and mounts for the control surfaces, removed the STOL airfoil at the wingtip in favor of Clark-Y (easier printing, will experiment with different wingtips to prevent tip stalls), and switched from a stressed-skin design to a dual carbon fiber spar design. The purpose of this V5 wing was to give myself a good baseline for testing the wing. I wanted to focus on the flight characteristics, so I used carbon fiber spars to avoid doing the required math for the spars and strut. I also switched to a 2 spar design so I didn't have to glue the wing skins on. No glue = completely modular and repairable. The issue with this is it is heavy and takes up a lot of space internally which would otherwise be used for bigger servos or internal electronics.

Dec. 27 thru present day:
Following some comments made by FlyerInStyle and my subsequent pondering of future wing designs, I decided to abandon the V5 wing testbed and redesign it to be fully 3D printed. However, once the V5.3D wing is finished, I already have the parts modeled and printed to use this wing permanently on my Mini Guinea.
I began by confirming the design of the ribs was adequate for the control surface loads. Then I sized the single main spar to take the full 25G load. With the help of a dumbell, I did some physical testing to confirm the spar could take the required load (No good pics of the test that passed, unfortunately). Finally, I sized the lugs in the center of the wing to take the full load of the outbd wing section.
With the new lugs attaching the outbd wing, that will allow me to return to a stressed-skin design like I had in the V4 wing to save weight, but I can also replace just the outbd section of wing if it gets damaged instead of replacing the entire wing. This greatly reduces the time required for wing repairs and revisions.

I am happy with the new V5.3D wing, but there are a few changes I need to make before moving on to the rest of the plane.
Issue #1: The tolerance between the lugs in the center wing are too tight, and they are slightly undersized. When I was trying to remove the outbd section of wing, I ripped some of the lugs in half. This might have been due to some slightly wet superglue, but one of the lugs on the other side is also cracked. I didn't account for the layer lines causing some additional weakness when I was designing these. This is the next issue I intend to fix.

Issue #2: Due to there only being a single spar and the wing skins only being one wall thick (0.4mm), the wing has very little resistance to bending about the vertical axis (wing tips moving fwd/aft). During installation, I cracked and bent the trailing edge skins in some areas. To fix this, I am going to add a rear spar along the trailing edge of the ribs. This will increase bending resistance about the vertical axis, add stiffness to the ribs to make installation easier, and increase the torsional rigidity of the wing due to aileron or flap loads.

Issue #3: The skins are very flimsy, deform easily, and are prone to cracking with normal handling. The skins actually exhibit intermediate diagonal tension with very little torsional load (Diagonal skin wrinkling) which is very cool, but considering how inconsistent single, interrupted wall prints can be with this material, having two walls side by side will be a great improvement (Plus the extra 0.1mm can't hurt). This will make the skins stiffer, less prone to cracking, and increase the torsional stiffness of the wing. This change has already been implemented into the 3D model and will be tested on the LH outbd wing during the maiden flight (testing not actually required since the V4 wing also had 0.5mm skins and had no issues with torsion or deformation before fiberglassing).

The new wing will go on its flight test within a week or two. I just need to print the new LH outbd wing and make a replacement nose for the Mini Guinea.

Edit: I also corrected my load distribution math for the wing which resulted in slightly lower overall loads (See attached picture). Score! I just have a basic lift distribution in Desmos which I then use to calculate the wing shear (lift) and moment distribution along the entire wing. This takes into account the strut location, lift reduction near the wing tip, and the shrinking wing chord outbd of the strut. It is by no means perfect and doesn't do any actual aerodynamic calculations (that's outside my wheelhouse), but it works.

 

[TaylorRAmes]

Small update:
I increased the clearance between the skins and substructure to facilitate assembly, increased the lug widths on the aileron side by 0.5mm each, increased the clearance between the lugs to facilitate assembly, and added a rear spar to increase the wing's bending stiffness in the forward/aft direction. I also removed the center trailing edges to make the wing compatible with the new fuselage mockup (in very early stages; I am currently cleaning up the exterior loft from a model I found online).
I accidentally glued the carry-through to the RH wing and ripped the skin trying to remove it, so I am nearly finished reprinting an updated version of the RH wing. I would have just replaced the flap structure, but the new lug design was incompatible with the old aileron lugs, and the wing was already partially damaged.
I ran out of superglue, so I won't start the (hopefully) final assembly until this weekend. I still need to rebuild the mini guinea nose and fix the nose gear before the maiden flight. The nose is big enough, I might just make a quick and dirty nose wheel steering mod and knock out two birds with one stone. I also just got my RV12is and assembled the fuselage, so we'll see which one gets priority. If I play my cards right, I could potentially have two functional RC planes at the same time! A historic event for a chronic can-kicker/modifier like myself.

 

[TaylorRAmes]

I had a less-than-successful maiden flight...mostly because the plane didn't leave the ground.
I assembled the new wing, printed a new nose for the mini guinea, and all my gyros and differential throttle were working perfectly.
Unfortunately, Mother Nature is a spiteful mistress. The wind caught the right wing and drove the left wing into the ground. Due to a springy front nose gear, the left prop struck the ground and ripped the motor mount in half. I had not even remotely considered that load case when I was making the mounts, so I'm not surprised it broke.
It's not all bad though. I was already revising the motor mount for the updated wing (the old ones I have been using take some coaxing to fit), so I'll just fix the strength issue at the same time. Should be ready for a re-attempt next weekend.

 

[bisco]

bummer! all the best with the remaiden!

 

[TaylorRAmes]

Maiden flight complete!
The wing did okay, but it still has some bad tip-stall tendencies. I purposely induced a stall and the plane immediately rolled over and entered a sharp dive. I recovered, but it was a lot closer to a full hull loss than I would have liked. On the bright side, the wing didn't snap and I see no signs of damage to the wing joint lugs. Score!

Nasty Stall Recovery

Unfortunately for this wing, my landing left a lot to be desired. I came in very fast since I'm not familiar with this wing's slow speed performance, so the plane slammed into a curb. Why did I land towards a curb? I don't know. Why didn't I move 5ft to the left where there was another 50ft of parking lot before the curb? I don't know.

Bad Landing

The damage to the wing isn't all that extensive. Although I added an aft spar to take fwd/aft bending loads (like you would see from a frontal impact), I didn't give those loads anywhere to go. Since the aft spar wasn't secured to the carry-thru, the wing skin was ripped apart and the wing pivoted around the main spar.

I'll modify the aft spar to add some screw holes for the carry-thru, add a fwd wing support on the fuselage to take thrust and crash loads (instead of hot glue), and I'll experiment with some different detachable wing tips to improve the stall tendencies. I'm currently considering a slip-on wingtip that increases the chord length for the last 1-1.5in of the wing and/or adds some washout.

 

[TaylorRAmes]

Progress is ongoing! My printer was down for a while due to some software issues (and a mistake I made while performing some maintenance. Der)

I reshaped the leading edge profile of the outboard wing. I originally took the lazy route and just offset the inboard wing profile to the size I wanted and shifted it forward slightly. This led to a very pointy leading edge and thin shape. After doing some research, these are both terrible qualities to have when you want to prevent tip stalls. I rounded the airfoil back out and am now using a constant radius leading edge. Coupled with the shorter wing chord, this should at the very least provide more gentle and predictable tip stalls.
The other options I had considered (under-cambered outboard wing, undercambered wingtip with longer chord, washout) all would have either been extremely difficult to print, alter the overall shape of the wing drastically, or increased the loading on the already slightly undersized wing joint lugs. Hopefully this strategy works, lol.

Another change I just finished was adding mounts in the carry thru for the forward and aft spars to react impact loads.

Now I just need to reprint the wing to test out these changes. Should be fun!

 

[TaylorRAmes]

I got the new wing printed out, just procrastinating on putting the servos in (the boring part, lol).

Since I'm replacing the old wing, I decided to do a test of the wing joint to see how much load it would take. I've done tests in the past to show the spar and assembled wing could take 25G, but I've only relied on analysis of the wing joint up until now.
Based on the math I have so far (incomplete, only considered net section failure and hoop stress), it predicted the joint would fail at 22-25G depending on what fitting factors I applied.
I secured the plane to the table and started loading.

50%, 75%, 90%,100% of 25G moment (weight at wing tip). Success! Look at the flex! 50% of vertical shear and 100% upbending moment.

Now to find the ultimate capability of the wing joint with 100% shear (4.5lb on the outbd half of the wing).
50%, 75%, 100%, 125%...SNAP at 145%. (weight at ctr of outbd wing, 4.5lb at 100%)

But it wasn't the wing joint. Due to some infill, the spar near the wing joint failed at 100% of its design load, only 65% of its analytical load. No big deal since it still it's 25G rating (and I've verified the spar math with prior physical tests), but interesting to see how much of an effect the infill had.

But the spar is not the star of the show here. The wing joint hit ~145% of its analytical rating without failure. It is definitely close to failure (screw holes are elongated), but we'll beyond the design load for the wing. I'm guessing there is some extra bending/plastic deformation adding to the ultimate capability.

Now that the old wing is well and truly destroyed, it is time to finally put this thing together and fly again.