Sig Kadet LT25 Kit Bash

[Nodd]

WARNING the following includes gratuitous kit-bashing. Perfectly good models were harmed in the making of this. The following thread is intended to inspire others to have a go at kit bashing their own towplane projects. Note this is not a guide, nor do I intend to make plans available or produce alternate parts for this particular kit.

So anyway... I am a fan of the legendary Bidule. I told myself one of these days... but then reality came knocking & there went that dream. I don't have the room at home to store one of these behemoths (even the smaller one), plus I don't fly gas, plus they're a fair bit beyond my meager budget.



I did have a half assembled Sig Kadet sitting on my shelf though. I was thinking that looks precisely just like a Bidule doesn't.



Although what if we flip the fuselage upside down. Does that look more like a Bidule?



Maybe shoulder mount the wing, move the V-Stab to the end of the tail, stick a bubble canopy on top. Hmm you know this might actually be starting to look a little bit like a Bidule. Well a rather small one at least.



Time to do some serious digital doodling.




And there we go... Its a Kadet/Bidule kit-bashed sorta looking thing.

[Nodd]

Began by enlarging the wing's control surfaces. Split the TE stock down the middle & added some lite-ply ribs.



I found a nice selection of bubble canopies at Park Flyer Plastics. Made myself some rounded structure to make that work on top of the bottom of the fuselage top. Yes we're still thinking the fuselage needs to be upside down.



As this was going to be a tow-plane I built this reinforced mount thing for the custom DIY tow-release. That will sit directly behind the canopy. And yes by now you've probably figured out, I have a laser-cutter. Or more accurately I have IFlyTailies laser-cutter. Fantastic tool.



I made the tow-release out of a short length of aluminum strut, some brass tube & a push-rod. Placed the tube inside the strut, filled the surrounding with epoxy then cut a notch for the tow-line. A push-rod pops up to hold the tow-line, retracts to release it & Bob's your Uncle.



Another bonus to having a laser-cutter is I can fashion my own motor mount, complete with 3° right, 3° down thrust (sounds about right). I also cut mounting holes in the firewall for the nose wheel.



I messed around in eCalc & determined that this beefy Turnigy Aerodrive SK3 - 4240-620kv motor should have enough umph to haul some fomey gliders, possibly something a bit heavier.



Progress on the upside-down-upside-down fuselage. 20 lb dumb-bell comes in handy once in a while. I mean its not like I ever use it for working out or anything. I forget what but there's something flat under my battery-box getting flatter.

[Nodd]

In addition to a laser-cutter, I also have a few 3D printers. Another workshop-of-the-future tool I can't do without these days. This would be the engine cowl 3D printing.



The finished 3D printed, custom designed, engine cowl. Its nice & lightweight & easy enough to replace if it ever gets damaged.



Gluing the tow-release bracing to the top of the bottom of the fuselage.



The Bidule has twin tails. The Kadet did not. So time for some more kit-bashing. Designed this V-stab/rudder. Note the hole for a 9gram servo, one for each of the two rudders. Even designed myself some control horns & a jig to make sure they're straight.



The laser-cutter will cut fairly thick wood but I find its much cleaner & stronger to cut multiple parts from thinner sheeting & then laminate those on top of each other to build up the necessary thickness. These tail pieces were cut from 1/8" balsa. I then laminated another couple of layers, with opposing grain, on top of that to get my final 3/8".



Dry fitting the new tail fins. That looks kinda like a Bibule. A naked one at least.



I also made some extensive changes to the wing so that it could be shoulder mounted to the fuselage. I won't do into detail about that here but I'm pretty happy with the way that worked out. Basically there's a carbon-fiber wing rod that runs through the fuselage. Actually its not a rod its a hefty CF plate that slots into the wing between the spars. Required lots of modifications but that's something for another thread maybe.

[Nodd]

This was my first tricycle gear. And no that has nothing to do with me working for IFlyTailies. I just haven't owned any non-tail-draggers before. Anyway as you can see I'm having all sorts of fun trying to bend this DuBro nose-wheel wire from hell. I even followed the instructions at their DuBro Tip-of-the-Day video on how not to break the darn thing when bending it. I managed to break it regardless.



Several days later a replacement nose-gear wire arrived. I think its 'interesting' that DuBro sells the wire part separately, now I know why. Anyway taking my lead from Pulp Fiction, I got a pair of pliers & a blow torch & got medievil on its arse. Success!



Remind me next time I decide to install a steerable nose wheel to check see if there's room enough to get my fat hand in there to tighten all these pesky grub screws. Now I understand why you guys all say bigger is better.



PhotoShop time. Using one of my 'wood-frame-model' photos from earlier I set about digitally trying out some color schemes. I ended up with this red & beige layout that I thought looked quite nice. The name 'BIDETTE" was me trying to be clever by combining the first part of Bidule with the last part of Kadette. I sent off the lettering CAD to Callie Graphics, she agreed to cut my awesome logo in adhesive backed vinyl.



Happy with my design I started the covering job. I recall being really good at covering once upon a time. I have a lifetime's worth of experience covering all sorts of models & yet these days I'm lucky if I get anything wrinkle free. The joys of getting older.



The tail is looking pretty good though.



With the covering done it was time to move some electronics around & see where she'd balance. I have a proper balance stand (not shown here), this was more of a stick the battery here & there, hold her up with my fingers on the CG & see what's what kinda session. I was amazed to find I could balance her just by positioning the electronics. I wasn't going to need to add any weight, always love it when that happens.



I laser-cut a few trays for my electronics to mount to. Note the GPS antenna in the rear. That will give me airspeed & altitude telemetry, handy for towing I figured. I also have an amp monitor that will give me the load & voltage of the traction pack. Again, helpful for aerotowing maybe. I can program the radio to yell at me when necessary.



This receiver has built-in on-demand stabilization if I choose to enable it. I have several other models with gyros but to be honest I almost never end up turning it on. But for a tow plane... I thought it would be nice to offer my customers a nice silky smooth ride, even when its blowing a bit.

[Nodd]

All done. Time to take the all important photos 'before' the maiden. All that hard work, at the very least I want a nice picture to remember her buy. A bunch of balsa sticks & a large garbage bag just aren't the same.



Quite happy with the way she turned out. You can't tell that the fuselage is upside down at all.



Moral support from my trusty co-pilot Roger. And pro photographer Alan of shootsnaps ready to document the carnage... ehh I mean first flight.



IT FLIES!



Initial feel is she's under-powered which was odd as the motor is plenty big. The big 'tundra' tires & the thick Spring grass made the takeoff run longer than I expected. Climb rate was also rather lack-luster. But she was flying & felt really good. No weird tendencies, everything was working great. Plenty of control authority, she also felt nice & light which was a relief. A really nice flying plane. Not sure what was going on with the power though. We did attempt an aerotow of an Easy Glider. That was best described as 'a very scale tow'. LOL, barely able to climb & the ground roll was stupid-long. But it did tow a glider!

[Nodd]

A lot of head scratching & a couple of weeks later, some changes were made. The most obvious is the name change. Apparently the guys at the field immediately nick-named her 'bidet', as in one of those butt-washing toilets. That wouldn't do so we flipped the names around & came up with Kadette/Bidule... Kadule. Not sure why that version didn't occur to me in the first place. Much better.

I spent some more time on eCalc looking into the flight performance issue & discovered apparently I was smoking crack that day. She needed & could handle a much more aggressive prop. This one was only pulling maybe 1/4 of the watts available. Actually the motor is so darn powerful I had to go with a three blade (not shown here) to get anywhere near the motor's real potential. Not enough ground clearance for a bigger two blade.

Subsequent trips to the flying field with the new three bladed prop yielded much better performance. She was able to tow no problem.



Just for kicks, here's the 'Kadule' next to Harvey's stock Sig Kadet. Watching him fly his was one of the reasons I got this kit. They sure look different now.



Out playing with the big boys. Apparently mine is somewhat smaller.



So I finally got my Bidule (kinda). It was a lot of fun working on this project & I'm quite pleased with the result. Let me know what you folks think.

[Sinkhappens86]

Awesome work man!

[stevekremer]

Nice Chris!!

[kjkavaney]

excellent project...Kudos....

[gwneuz]

Fantastic! Thanks for sharing. What kind of filament did you use for the cowling?

[Nodd]

Thanks everyone.

The engine cowl was 3D printed using regular PLA filament. I think that was 3D Solutech Real White PLA Filament 1.75MM but Solutech seems to have gone out of business so I don't use their filament any more. Slicer settings were set to a single wall thickness with a 12% infill. I did consider making the cowl stronger by using more infill & maybe triple wall thickness but I wanted to keep this fairly lightweight. Plus I don't expect this cowl to take a much abuse being a tricycle gear aircraft. The cowl is unlikely to ever hit the ground unlike tail-dragger models that tends to fall over on its nose a fair amount. And of course the beauty of 3D printed parts is they're easy to replace, just print another if need be.

I did run into the usual issue with 3D printed parts out in the sun, the top of the cowl sagged just a little last season but not bad enough that I feel like re-printing it. I do try to keep my 3D printed stuff in the shade as much as possible, especially darker colored stuff. Its fine when its flying though.