Sig Kadet Mk.1, Finishing a Classic with Spare Parts

[Joker 53150]

About a year ago I saw a Craigslist ad for somebody selling a couple unfinished planes, located only a few miles from me. A quick call to get directions to the seller's place and I was on my way! When I got it, I wasn't sure what kit this was, only that it was somewhat old, well built, and very dirty. It was sitting in an upstairs storage of a commercial property, and was brown from the dust and there were (are) a couple spots of tar on it that probably fell on it during a re-roofing of the business.

After getting the planes home a quick online search informed me this was a Sig Kadet Mk.1, the early version of the plane. There was no engine in it, but holes were drilled for servos. From what I can tell, it's never been finished or flown, so time to change that!

Here is the starting point, after using Windex to clean the surfaces as much as possible. The wing has some damage to the covering, both wingtips have dents in the plastic caps, and there is still some brown staining that I haven't been able to remove. Tonight I'll try some xylene & water mixed to see if that's strong enough. *IF* I can get the wing clean I'll just patch the holes and fly it as-is for now, but if it's still extra-ugly I'll strip and re-cover the wing. Hopefully that won't happen, as the guy who built the plane did a great job covering it, and even made his own full-length piano hinges for the control surfaces. I'll get some pics posted of those later on, they're very interesting (and major over-kill). I like the design of the windows, which gives it a sort of commercial airplane feel. The cowl was cut out for a glow engine, I may leave it that way as I convert to electric, or maybe I'll get bored and try to fix or replace it with a full cowl.




From the top, the discoloration is hard to see, but you can see a hole in the covering and the tar that dripped onto the wing, plus the dented wingtip. If I re-do the wing I may remove the plastic caps and carve balsa replacements - we'll see what happens.




The wing bottom has a much larger hole, but the balsa structure is undamaged. This would be an easy patch. Here you can also see the continuous hinge the builder made. It's done using a bunch of short sections of brass, glued alternating sides to the aileron and wing. I'm not sure why he did it this way, and have never seen it done like this before.




Inside is really a blank canvas. The servo rails will probably be moved further back to make room for a 3 or 4 cell battery to fit.




The original design of the Kadet Mk.1 had a rubber band mounted wing, but the builder did most of the work to convert it over to bolt-on. The only thing that wasn't done (yet) is adding the hardwood blocks and captured nuts to run a couple bolts down into at the back of the wing. The wing itself has been modified already for the bolts.




Overall, this should be a fairly quick project (hopefully). I checked through my stash of parts and found that I've already got the motor, ESC, 3 servos, wheels, enough white covering to patch (but not completely re-cover) the wing, pushrods, etc to finish the plane. Besides covering, the only thing I may need to purchase is a pack of wheel collars for the landing gear. I'm hoping a 3 cell battery would be enough to fly this plane, but it was built for a glow engine and is fairly heavy, so I'll probably get much better results with 4 cell. I do have three 2-cell 2200mAh packs, so I can use two of them to make a 4-cell pack.

 

[rockyboy]

Wow - great find! Nice looking bones on that one

 

[Joker 53150]

Yeah, the builder did a nice job with it, and I'm happy with the limited damage considering the age of the build. My guess is that this plane is over 20 years old.

Thinking a little more about the wing covering... There are only so many good flying days left for me this year, so the wing will probably just be patched and used as-is instead of re-covering it. Hopefully I have some green covering that is close to the green used on the build, and I can use it to make a big orientation stripe on the bottom. A complimentary color would also work. The top would either be a thin color stripe or more likely a small white patch. The dented wingtips will either wait for work, or maybe I can find some way to pull the dents out and reinforce the plastic from inside, such as an expanding foam.

Too many airplane thoughts in my head, considering I'm supposed to be working!

 

[Joker 53150]

I love dealing with companies like Sig and Balsa USA due to their responsiveness and customer assistance. The Mk.1's cowl is cut for a glow motor that was never installed and will look pretty bad with an electric motor, so I e-mailed Sig at 12:45 this afternoon and 2 hours later I had a response, confirming that the cowl for the current Kadet will fit the older Mk.1. Plus, it's cheap at less than $7.00. Looks like I'll be ordering a part for this project after all, but will wait until the end to make sure it flies.

 

[Joker 53150]

First job last night was relocating the servo rails further back in the fuselage to make room for the battery pack and ESC. As it was built for glow, the builder only really needed room for the gas tank in the nose, a battery, and receiver. New rails were glued to the fuselage sides, and the new servo-mounting rails will be glued down to these pieces. Note the mildew on the balsa. One of the other planes I picked up with this one has quite a bit more on it, but it's just a bare frame with no covering to protect it. That's a future project.




While the glue on the side rails was curing I noticed the control horn on the elevator was screwy. It's set up backwards, probably because the builder was just going to run a pushrod into the keeper and tighten the screw, and that would interfere with the fuselage sides (the elevator pushrod on the Kadet series comes straight out the back of the fuselage, not the side as on most planes). Leaving it this way would force me to do some goofy programming in the transmitter to give me equal up & down throws, so I decided to change it.




I happened to have the same brand/size control horns in my stash of parts, so I shifted it slightly and turned it around so the horn lined up with the centerline of the fuselage. Now a standard DuBro clevis will work and give me proper throws. It'll also hide the clevis a bit, giving me a cleaner look (not that it matters much).




And back to the servo rails, the new location is 4-1/2" back from stock, which will give me all the room I need for battery placement. Like the Kadet Senior I just finished, the wing will have to come off to get the battery in/out, but it's only two screws so it's not a huge issue. In a nod to how the original elevator pushrod was designed, I used a 1/4" hardwood dowel with pushrod wires epoxied into each end for the elevator. It's functional and works well. The rudder is controlled by a standard pushrod wire in a tube, and the steering will be done with a flexible pushrod in a tube. The tube is already installed for the steering, but since I moved the servos back I'll need to replace it with longer piece.

 

[nhk750]

Holy cow, piano hinges! Thats a heavy duty setup there, just like a real airplane.

 

[Joker 53150]

Holy cow, piano hinges! Thats a heavy duty setup there, just like a real airplane.

No kidding! From what I can see, these aren't just piano hinges, but home-made piano hinges. It appears the builder took a brass rod and cut it into ~ 1" lengths, and then glued them alternating on the control surface and stabilizer. The elevator, rudder, and both ailerons are done this way. He then covered over them as the rest of the plane was being covered. Gaps are all very small and movement is smooth, so it's well done. I have no idea why he did it this way, unless it was just an exercise to see if he could do it?

 

[Joker 53150]

The Kadet Mk.1 has reached a milestone, it now moves under it's own power! Testing has been done with a charged 3S battery, and it's got FAR more power than I expected, so I don't think 4S will be needed. That'd be great, as I have plenty of 3S 2200 packs and have enough 2S 2200's to make up 1 at 4S when running them in series.

In the video it may not be obvious, but the motor mount is a bit "rough". I stacked a bunch of 1/4" and 1/2" layers of ply and epoxied them together, as I wasn't really sure what the final motor mount design needs to be. I've got a bit of down and right angle to the motor currently, but it's all a guess as the firewall has none designed into it. Maybe that's the way it should be, I'll know soon enough! But once I replace the cowl with a new one I'll re-do the entire mount accordingly.

Next up is the wing - patching some holes and installing a servo. If all goes well it should be done today. Hopefully!

 

[Joker 53150]

The wing work begins! Before tackling the issues with the covering I'm going to get a servo installed for the ailerons. It's set up with a single servo and two pushrods attached to torque tubes. Quite honestly, I'm not sure ailerons are even needed due to the amount of dihedral in the wing. My Kadet Senior works great without the ailerons, but I'll give it a shot and see what happens.

The guy who built the plane built a large bracket for a servo, although I'm not exactly sure what he had in mind for the servo installation as it doesn't really work for the various servo sizes I had on-hand. But making it work would be easy enough.




The servo needed a couple extra cross-bars, so I used some pretty old wood I had on hand from my 1/4 scale Pietenpol build. how old is it? Well, the guy who gave it to me said it was used in an original Pietenpol wing spar back in the 30's or 40's. He liked the Pietenpol I was building and sent me a chunk of wood, which became the main struts holding the wing up. I enjoy using some classic "aged" parts in my builds when I can. A little epoxy will hold the new pieces in place, and then pushrods will be installed.




After the servo work is finished, this is the biggest task left - fixing a slight tear in the wing bottom covering.




So far my plan to buy NOTHING for this build is going well, as long as my time and the electrical bill aren't figured in.

 

[Joker 53150]

....And it's finally ready for a maiden. "Finally"?? It feels like I've been working on it for a while, but it's been less than two weeks!? That can't be right.

The radio programming is done for now, but will be tweaked as needed after the maiden. A battery tray is added to the nose, and like the Kadet Senior I recently finished I have to remove the wing to change the battery, but it's only a minor inconvenience. Assuming the maiden goes well I'll order a new cowl and better wheels for it.

Now the wait for good weather begins. Tomorrow is marginal, so I'll put it off until things calm down a bit. Maybe...

 

[Joker 53150]

One final note before a maiden flight, this plane took a LOT of nose weight to hit the CoG shown on the plans. I've added about 1.5 ounces to the motor mount AND stuck a second 3 cell 2200 in the nose just to balance it! I'm hoping that the plans are wrong and that weight isn't needed, but based on how over-built this design is with a fully-sheeted fuselage I'm guessing it's accurate.

As mentioned earlier, the eventual plan is to re-build the motor mount once I know what is needed for side & down thrust, and I'll be able to incorporate nose weight inside it as needed. If I can't easily add the weight and have to keep the second battery, I'll just make a "Y" harness to give me a 3S 4400mAh pack. May as well use it if it has to be carried!

 

[Joker 53150]

Maiden Flight Report!

This was my second maiden flight of the day, with the first being my Mountain Models EVA Bipe. A couple things I needed to determine on this plane - if the nose weight was really needed, are the ailerons needed, does the motor need down-thrust, and are my throws acceptable.

As mentioned previously, I've got a couple ounces of dead weight added to the motor mount and an extra 2200 3 cell stuffed in the nose to hit the CoG shown on the plans. Fingers were crossed it wasn't really needed, but no chance was being taken on the maiden.

Winds were a bit higher than I'd like for a maiden, but for the size this plane is fairly heavy so I figured it would handle it well enough. I did a final check of the controls and took the plane out to the grass, and gave it some throttle. The wheels aren't quire large enough, but it rolled out well enough and after a short time it was in the air!

It was fairly twitchy and needed a lot of down-elevator, but a little trimming had it flying well at 1/2 throttle. When I gave it more throttle it really started climbing hard, but that can be fixed with some down-thrust. The ailerons worked well enough, but really weren't needed as the rudder was more than capable of controlling the flight. The rudder was also super-responsive, just like my Kadet Senior.

Landing was uneventful, other than the fact that it really glides a LOT, even with the throttle at zero. I ended up doing a couple extra circuits as I worked to get it in for a landing. Both landings done today were smooth, and that's where the ailerons come in handy as they give better small adjustments than the rudder.

So to answer the questions I had about the plane before the flight:
Unfortunately, the nose-weight is absolutely needed. However, since the motor needs quite a bit of down-thrust I'll simply re-build the motor mount into a nice box that can be filled with lead. Ideally I'd like to get rid of the second battery although that may be a pipe-dream. Ailerons aren't really needed, but since it's got 'em I'm going to use 'em. Since the wing was also built with the stock dihedral the ailerons are somewhat anemic, so I'll increase the throws. The rudder is also too responsive so I'll drop that throw quite a bit.

Part of the tail-weight issue is my fault, for moving the rudder & elevator servos back about 4-1/2", but without doing that I wouldn't have had much room to install the battery. I could have gotten by with moving it back maybe 2-1/2", but hindsight is 20/20.

With a little tweaking and a new motor mount she'll be ready for another try!

 

[Joker 53150]

I forgot to mention the repairs on the wing covering. The top was pretty easy, a small white patch was ironed on to seal the hole. It doesn't match very well as the top of the wing is still stained and a bit ugly, but I can live with it! The bottom of the wing had the big hole, as shown here. The repair was pretty simple as I didn't want to waste a ton of time making it pretty.




The extra material was removed and a couple big green stripes were added, covering the hole. The green matches fairly well to the green used for the windows, and they're big enough to be easily visible from the ground for good orientation.

 

[Joker 53150]

Waiting for the Balsa Build Along to start I'm working to finish a couple lingering projects. First up is some required work on the Kadet's motor mount. The original mount was very rough, only built as a quick piece to make sure everything was actually going to work before I spent any real time building. As I was buttoning up the project it looked like the plane was going to need a LOT of nose-weight to balance properly. It really made me wonder if it was truly that tail-heavy or if I was missing something. Turns out that the tail is made of lead, and all that nose-weight was required. I also wasn't sure about the need for down-thrust or right-thrust, as neither was shown on the plans and it wasn't built into the firewall like it is on my Kadet Senior. And of course, it needs down-thrust and a touch of right.

Now that I know what it needs, I can re-build the motor mount to incorporate these changes. I'm basically going to build a "bucket" out of the mount that can hold chunks of lead. This will *hopefully* allow me to carry only one battery instead of two, and will also clean up the mess of extra weight I temporarily attached to the original mount.

After making some measurements I drew up the main pieces on ply and started cutting. Not shown (yet) are the back pieces that will be added, or the top (assuming I add a top). After a little sanding they'll all be epoxied together. They are designed to interlock, giving me more surface area to glue.




After gluing and a quick sanding, this is the basic design. A couple more pieces will be added across the back which will be bolted to the existing bolt holes in the firewall, and I'll also drill some small holes and insert some hardwood dowels to help pin the pieces in place for extra insurance. The weights I'm using are the typical strips of 7 gram stick-on's, and I'm removing the adhesive back to make more room for lead if needed. I had one new 6 ounce package of weights on-hand, and after removing the adhesive back I found there is easily room for 24+ ounces of weight in this box if I filled it! MATH TIME!! A typical 2200 3 cell is about 8 ounces, and I had one added for weight sitting slightly in front of the CoG. There was also about 7 ounces of weight attached to the previous motor mount. To achieve proper balance with the new mount I know I'll need to add the 7 ounces back at the motor mount, and will probably need about 5 ounces at the motor mount to account for the weight of the extra battery being removed. It's farther forward of the CoG, so I won't need the full weight of the battery and should achieve a net savings of about 3 ounces. It still bugs me that I need to add approx 12 ounces of dead weight, but at least the plane handles that weight well.

 

[rockyboy]

I guess you've been getting into my head with these Kadet Seniors... cause at the RC auction this weekend when they got to the very last item and the crowd was pretty well gone or distracted, I picked up this for the price of a good pizza



Yes, the other half of the wing is in the bag under the body, and looks just a clean as the first half. Even came with servos and a receiver. Just needs a little cosmetic work, and a power system. Was even converted to electric already and has a battery tray and x mount style firewall and t-nuts. Really just a steal

What motor are you using in yours? I have read these will fly really well anywhere with anywhere from 50 to 100 watts per pound power, which is a pretty wide range.

 

[Joker 53150]

I guess you've been getting into my head with these Kadet Seniors... cause at the RC auction this weekend when they got to the very last item and the crowd was pretty well gone or distracted, I picked up this for the price of a good pizza

Yes, the other half of the wing is in the bag under the body, and looks just a clean as the first half. Even came with servos and a receiver. Just needs a little cosmetic work, and a power system. Was even converted to electric already and has a battery tray and x mount style firewall and t-nuts. Really just a steal

What motor are you using in yours? I have read these will fly really well anywhere with anywhere from 50 to 100 watts per pound power, which is a pretty wide range.

Dang, a Senior for about $20-ish?? Nice score! Mine is set up with a 5 cell 5,000mAh battery and Turnigy G46 motor (about the same as a .46 glow). 5 cell is kind of an oddball, but I'm running that same battery and motor combination on an electric Astro-Hog and a 1/4 scale Pietenpol, so at least I've got multiple uses for the batteries. It carries the weight of that battery with zero effort. If you have a lot of 3 cell 2200s you may also look at going 6 cell 4400 by running them in parallel and series. Again, that kind of weight would be no problem.

Yours is set up with ailerons and a 2-piece wing, that'll certainly make your life easier transporting it.

Do I smell a "rescue thread" in your future?

And for those who haven't seen that build thread, here's a link:

http://forum.flitetest.com/showthread.php?33539-Sig-Kadet-Senior-Rescue-amp-Rebuild

 

[Joker 53150]

I did some more work on the motor mount on the Kadet, and was able to get it mostly finished. Once I know it's how I want it some LockTite will be added to seal the deal.

Now the part I'm super-ish happy about....! I put a single 2200 3 cell as far forward in the battery bay as possible, which puts it right up against the back side of the firewall. With the prop and cowl installed I dropped the 6 ounces of lead into the new motor mount "bucket", along with about 8 fender washers (about 3-4 ounces), and it balanced! That's about 2 ounces LESS than I was expecting, probably because all this weight was all about as far forward as it could be, compared to the extra battery I had which was much closer to the CoG.

So now I just need to clean it up a bit, LockTite the bolts, and secure the weight so I can get it back in the air to test it all out.

I also noticed that the front nose wheel and strut have quite a bit of weight on them due to all of this extra weight, so I'll go through and make sure the entire steering assembly is ready for action. A couple hours in the shop should have it all ready to go, can't wait!

 

[rockyboy]

Do I smell a "rescue thread" in your future?

And for those who haven't seen that build thread, here's a link:

http://forum.flitetest.com/showthread.php?33539-Sig-Kadet-Senior-Rescue-amp-Rebuild

You betch'a

With that sized motor in mind, I think I have one with an 60amp ESC that's been sitting in my junk drawer since the very first RC auction I ever attended 3 years ago. I'll need to double check that, but if I'm right I won't even need to buy any new gear for this plane! :applause:

Thank you!

 

[Joker 53150]

You could probably get away with a 4 cell setup if needed. I can't recall if I went full power with the 5 cell on mine, and it cruised easily at 1/2 throttle once airborne.

 

[Joker 53150]

The rhinoplasty on the Mk 1 is done! Here are the before and after pics, and it becomes obvious that the motor is about 1/2 cm too far out, but I'm not going back and re-building the motor mount for that. Thanks to Sig for keeping so true to their original design that the cowl for the current Mk 2 Kadet still fits the early models. So not only does the new cowl hide the motor and slightly ghetto motor mount, but it's also nice & white compared to the aged and yellowed original cowl. Now all I need is some good weather to see how the updates work out.