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Dec 28, 2020, 04:55 PM
MattKennedy's Avatar
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Need help with a few kit building questions (Kadet Senior)


Hi. Im a relatively new member that is re-entering the hobby after 30 years. It has been so long I feel like I am starting over so I decided to start by building and flying a trainer. For a new trainer, I am building a Sig Kadet Senior kit (stick built not ARF), which brings me to the reason for this post. I am hoping I can get some help with a few questions I have during the build.

Servos To start out at least, I am building the standard 3 channel design (throttle, rudder, elevator). This is roughly a 6lb plane with a 78 wingspan and is generally considered a slow flier. Not sure its relevant but Im also planning to run a Saito .62 four stroke. After some reading, it sounds like standard size servos are recommended. I was considering using a Hitec HS-425BB Deluxe Ball Bearing Standard Servo. Wanted to just check in to see if someone more experienced could confirm this would be a good choice of servo for all 3 channels for this plane. More info on this servo here: https://hitecrcd.com/products/servos...-425bb/product

Pushrods (rudder/elevator) The kit calls for configuring each of the pushrods for elevator and rudder using roughly 24 of 5/16 square balsa with 2-56 wire epoxied on each end. From the reading Ive done it sounds like Id be better off changing the 5/16 sq balsa over to 1/4" hardwood dowels which I plan to do. The part I am unsure about is, from what I am seeing in the instructions, and on the plans, these pushrods do not seem to be supported anywhere within the fuselage. It seems you simply connect one end to the servo (I plan a Z-bend here) and the other end to the control horn using the supplied metal clevis. This may be fine, I just wasnt sure so my question here is does it seem right to run the pushrods this way without any support whatsoever all the way from servo to control horn?

Pull-pull cable routing One change I am making to this plane is to change the landing gear over to a taildragger. The tailwheels I am finding are controlled via a pull-pull cable setup. This pull-pull setup is something I am unfamiliar with. I am confused by how these cables are routed through the fuselage. Based on the photos Ive seen, it looks like the cables used in this setup are not covered by any sort of tubing or sheathing. Do they just need to be run in a straight line from the servo to control horn? With some sort of short piece of tubing to guide it where it exits the fuselage?

Hinges for control surfaces The kit comes with paper-like CA hinges for the rudder and elevator. I am not crazy about the idea of using these given the mixed reviews and experience I am reading about people having with them. I thought I should ask if these Dubro nylon hinges I am considering are a better option for the rudder and elevator on this plane? Here are the Dubro hinges I am considering: https://www.dubro.com/collections/hi...s/nylon-hinges


Thanks for any and all insights!
-Matt
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Dec 28, 2020, 05:09 PM
MAAC SAVED RC!!
vettster's Avatar
First let me say.. Welcome Back!!

The servos you have chosen are fine.

Yes some kits and ARF's ask you to use the long stick method and NO they do not tell you to support the rod.. however.. I have always added some sort of support. Sometimes Its as easy as running a piece of blue foam across the fuse.. just make sure nothing binds!

Pull Pull.. Yes they are that simple. Its been awhile but I do recall you would run the cables so they cross over each other. I believe it was for a better mechanical advantage. Im sure others with chime in here.

Hinges.. Well Matt.. they are a matter of personal preference. Yes the ones in you link are good hinges. but so are the fiber hinges in your kit. Like any hinge.. if there not installed correctly.. they will pull out. I love the simplicity of the Fiber hinge. Have them on my jets and have never had a problem.

All the best!

Trevor
Dec 28, 2020, 05:59 PM
Registered User
tubig's Avatar
Matt, I'm not familiar with the Kadet but for steerability you could just drive the tail wheel by direct connection into the rudder thereby bypassing the need for the pull-pull.

Also, how will you redesign the location of the main gear for the taildragger setup?

Tim
Dec 28, 2020, 08:45 PM
Registered User
Hi MattKennedy,

Regarding the pushrods, they don't require any other support. Having built the Sig Kadet MK 2, the Sig Midstar 40, a Lou Andrews Aeromaster, and a few others all with the pushrods you describe they don't require support. Dowels are good as long as they are stuff enough but square balsa stock works great too as long as it's stiff enough. More important to me is that if you have a straight pushrod from servo to control horn make sure I've of the ends is either az Bend or the clevis is soldered. If not the control rod can unscrew itself, all me how I know

The tail wheel steering is a little more difficult due to the rudder not extending to the bottom of the fuselage, I would feed a piece of music wire through a plywood mount on the fuse up to the rudder and connect it to the rudder. It's then a direct drive.

https://www.rcuniverse.com/forum/kit...onversion.html

Post #8 is what I was trying to describe but this has a lot of pictures.

Cheers,
Brian
Last edited by flylots; Dec 28, 2020 at 08:48 PM. Reason: Found a link that might help.
Dec 28, 2020, 08:57 PM
MattKennedy's Avatar
Thread OP
Trevor, thank for for the welcome and for the advice.

Tim, controlling the tailwheel by tying it directly into the rudder can be a bit of a challenge on the Kadet Sr. given the way the tailwheel is separated from the rudder by the fuselage. Long story but Sig does make a custom tailwheel for their ARF version I could use but I called and it is out of stock until next summer. I have seen at least one custom made setup that worked similarly to the Sig version, it doesn't look that simple and I'm not sure I'm up to that task at this point. Which brings me to the number of aftermarket tailwheels that will work, it just that most seem controlled by a pull-pull arrangement.

For the main gear, I'll be using an aluminum main gear, most likely from tntlandinggear.com. Based on the experiences of the many people that have done this before on this plane, I'll likely locate it so it lines up with the leading edge of the wing (also as per ARF version). As I construct that part of the fuselage, I'll be building the necessary ply structure to support into that location.

Thank you both for your help.

-Matt
Last edited by MattKennedy; Dec 28, 2020 at 09:16 PM.
Dec 29, 2020, 08:15 AM
Registered User
for sport glow planes i like using carbon arrow shaft rods and 2-56 hardware...for added security i do add bracing in the fuse, but not totally necessary...learned this method earlier this year...have used 3 times with excellent results....
Dec 29, 2020, 08:29 AM
Registered User
For hinges I love the hinge points...these work great...I lube the center pivot with vaseline an a Qtip...there some great videos in YouTube....a drill guide is a must IMO for center

Doesn't hurt to rub a little vaseline on the covering either to prevent glue from sticking....masking tape does wonders too...still perfecting his method.

https://www.ebay.com/itm/171778465856
https://www.ebay.com/itm/333732251252
Dec 29, 2020, 08:37 AM
A Day @ a Time - Matt. 6:25-34
ruff1's Avatar
Quote:
Originally Posted by MattKennedy
...I'll be using an aluminum main gear, most likely from tntlandinggear.com. Based on the experiences of the many people that have done this before on this plane, I'll likely locate it so it lines up with the leading edge of the wing (also as per ARF version).
Welcome back Matt!

As for the landing gear, I converted a Carl Goldberg Eaglet 50 into a taildragger. I lined up the wheels with the leading edge and despite a scolding from someone on the thread it ground handles well and rotates easily for takeoff. It also helped with CG as the nose gear weight was not there, and the hand-me-down motor has plenty of power but could have weighed a couple ounces more. I can see where a tricycle gear setup could require the gear to be placed far enough back to prevent tipping, but not sure how important that is on a taildragger as long as it is forward of CG enough to avoid nose-over.
Dec 29, 2020, 08:50 AM
Registered User
I scratch built a Kadet LT-40 tail dragger. The tail wheel presented a problem as described by flylots. Here is how I did the tail wheel. The vertical wire is cut above the collar. The horizontal wire attaches to rudder. All easy to remove if needed.
Dec 29, 2020, 09:47 AM
MattKennedy's Avatar
Thread OP
Thank you all for the help and advice.

Flylots - not sure how I missed your reply last night when posting my reply but did. Thanks for the advice regarding the pushrods and securing the clevis. Noted. That thread you pointed to with the custom made tailwheel is encouraging. Its not all that different than the way Sig themselves do it with the ARF. I was a little unsure about whether I could fabricate something myself that would work but that looks fairly straightforward. Maybe I'll give it a try. Thanks again for going to the trouble of posting the links, etc. Extremely helpful.

RCPilot - Thanks for sharing the method for using arrow shafts. I will explore further. Regarding those Robart hinges, I had seen another recommendation for using those in my reading/research but was unsure whether their design might result in a larger than normal gap between say the vertical stabilizer and the rudder itself. Basically the gap between the fixed and movable control surface being hinged. Hopefully I am saying that correctly. It seems like the actual hinged part at the center is on the larger side? So when you use these, can the gap be the same size it normally is with say a CA hinge?

Ruff1 - Great to hear you have had success locating the main gear similarly. Great to know.

ETPilot - I can see where you added the collar and horizontal wire but did you also bend-up that entire tailwheel gear in that photo including the spring portion or did you find some existing product to start with and then extend it vertically somehow? Would love to know more. I haven't found much in the way of what I guess I would call "vertically oriented" tailwheel gear.

All, thanks very much for all the feedback, guidance and advice.
-Matt
Dec 29, 2020, 10:40 AM
Registered User
Quote:
Originally Posted by MattKennedy
Thank you all for the help and advice.



RCPilot - Thanks for sharing the method for using arrow shafts. I will explore further. Regarding those Robart hinges, I had seen another recommendation for using those in my reading/research but was unsure whether their design might result in a larger than normal gap between say the vertical stabilizer and the rudder itself. Basically the gap between the fixed and movable control surface being hinged. Hopefully I am saying that correctly. It seems like the actual hinged part at the center is on the larger side? So when you use these, can the gap be the same size it normally is with say a CA hinge?


-Matt
ifyou notch and or bevel the control surfaces you can have a tight gap as with any hinge....Robart makes three sizes...for glow planes i use the size i posted, would be medium..they make a smaller size for foam/elec models, and a large size, for big gas 3d planes and more
https://www.airfieldmodels.com/infor..._points/03.htm
heres a good how to https://www.youtube.com/watch?app=desktop&v=R_IKon3CiDM

good luck with your Kadet
Dec 29, 2020, 04:02 PM
MattKennedy's Avatar
Thread OP
OK. Thanks again for the help RCpilot.
Dec 29, 2020, 04:06 PM
A Day @ a Time - Matt. 6:25-34
ruff1's Avatar
Matt,

I fashioned a wire into a tailwheel assembly on the Eaglet 50. Started by bending a 90 degree piece to be epoxied into the rudder, then ran the wire down into the fuselage at the same angle as the hinge line. I had enough wiggle room to ca the hinges no problem. Created a hardwood piece to go under the fuselage, then a wheel collet to secure the wire from being pushed up. After that some appropriate bends to the tailwheel axle.

I don't have a good picture of the tailwheel setup but happy to snap a pic if you would like to see it.
Dec 29, 2020, 04:28 PM
Registered User
gene6029's Avatar
Matt, I have the ARF Kadet Senior and made it a tail dragger. I use standard Futaba 3003 servos. The pushrods are balsa with wire ends attached with epoxy and thread and a clevis on each end. I drive the tail wheel with an extended wire that runs thru the rear of the fuse and into a 90 degree bend that passes into the rudder. The motor im useing to train people with is the lowly LA .40. Ill try and post some pictures to give you an idea of where i located the landing gear. The Kadet will do loops and aileron rolls easily with the LA .40.....Gene
Dec 29, 2020, 04:44 PM
Registered User
gene6029's Avatar
Here is a picture of the tail wheel. You can see the wire that goes up thru the fuse towards the rudder. Also you can see the balsa pushrod and wrapped threaded rod with clevis....Gene


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