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Author Topic: Baby Kadett  (Read 2029 times)
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crashcaley
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« on: June 04, 2009, 08:43:03 PM »

I decided not to do a complete build thread, but couldn't fine a general thread to put this in. I figure I'll post my newest radio control creation here. Well, it isn't designed by me. My friend John, that flys at the dry lake bed with me on sunday, scaled down this from the larger airplane called a Kadett Senorita. He calls it his Baby Kadett. It has a wingspan of 44 inches. It's is pretty easy for the build. I think his is powered by a .25 glow engine, and weighs quite a bit, maybe 3.5 pounds.

Mine will be powered by an electric motor, to be determined, as I don't know the final weight. Right now it weighs in at a hefty 6 ounces. That includes the four Hitec HS-55 servos and the landing gear. I'm hoping that it will come in around 12 ounces.

Wonder why I always build so light? Used to building for free flight rubber, I guess. Problem with light radio controlled models is that they don't like a lot of wind. But, when this puppy does get a nice day, it should float, if I've built it properly. A photo is attached for you to look at.

Caley
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Baby Kadett
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crashcaley
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« Reply #1 on: June 04, 2009, 11:56:16 PM »

Goofed on the present weight. It is a hefty 9 ounces.
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thymekiller
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« Reply #2 on: June 05, 2009, 08:24:06 AM »

Nice. Will be watching with interest. I heard the Kadetts fly pretty well. I hope to build my own later.

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crashcaley
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« Reply #3 on: June 05, 2009, 09:18:06 AM »

thymekiller, I've heard the same. I know that the big Kadett Senior flys wonderfully. The Kadett Senorita also flys well. Never seen John's Baby Kadett in the air, though he said that it had flown well, but is now giving him problems. He thinks it might be wing warps. We will see anyway. I've still got to install the pushrods to the tailfeathers, connect and check the electronics, then cover it. I'm lucky that I happened to have a brushless motor and speed control in stock. It will run on a two cell lipo, and according to the computer program, Motocalc, fly around 12 to 15mph. Stall speed is supposed to be 11mph.

Caley
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crashcaley
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« Reply #4 on: June 06, 2009, 05:42:59 PM »

More work done. Getting much closer to adding the motor and speed control you see near the nose gear.

I've added the landing gear. Twas somewhat of a chore, as I am using this and that, that I have available. The nose gear wire was skinnier than the nose gear block. So I ended up inserting an aluminum tube, flairing the ends to hold it in place, and then drilling a hole in the tubing for the screw to penetrate to the nose wire. I also had to file ta flat spot on the nose wire in order for it to get a good grip and not slip.

I got the control rods going to the tail feathers done. What I did was test fit the tail feathers with the control horns attached, then hang the wire between the horn and servo to see where it would run. I cut some hard balsa strips and inserted plastic guide tubing which the wire will run through. I fitted it all together and glued the balsa strips to the uprights holding with clamps. I tried hard to avoid curving the wires, but managed to get a tiny curve in anyway. Things seem to move fine. Hopefully there won't be any binding when there is a load on things when flying.

You might notice in the picture some black blocks on the nose. I had to use magnets to get things to balance when fitting things together.

I still have the cowling and wind screen to work on and test fit. Once that is done, I can add the motor, speed control, receiver, battery tray and battery to get the airframe balanced. That will probably change a tiny bit when I finally cover things. But, at least I won't require a lot of ballast to get things rebalanced.

Caley
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thymekiller
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« Reply #5 on: June 07, 2009, 09:31:04 AM »

As far as final balance, I think I have heard that most use a movable battery tray.? I look forward to the day when I have to deal with the issues that you seem to have a handle on. Your plane looks great. May I ask what kind of motor you are using? Also, if you change to a larger motor, would there be a great deal of re-balancing to do? With free flight, changing motors doesn't cause a lot of change. {some, but not a lot} Is it different with elect?

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crashcaley
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« Reply #6 on: June 07, 2009, 01:28:08 PM »

TK, I'm going to try using one of my outrunner brushless types, a HET Micro 6/20 and Tsunami 10 amp speed control with a two cell lipo of around 800mAh with a 20-25C rating. One problem with the motor is that it is a very high rpm rating at 1800.This is way too much for such a light model, thus my use of a two cell lipo pack. Even then, the prop pitch speed is higher than 2.5 to 3 times the stall speed of the model, which makes taking the model off very difficult, unless you are very good at throttle control to keep the rpms low during that phase.

Any time you change out a motor, you will need to rebalance the airplane, if that motor is heavier or lighter. Like you said, the battery tray can be moved, if you design it to do so. What I am going to do is install that last, after covering. I will install a base plate on the floor of the airplane that is long enough for me to do the adjustment. The real key is to make sure that you can get your battery pack under the wing at CG. That means balancing the model prior to covering. Sometimes all that is involved is adding a little more wood in an area, though sometimes it requires a little lead weight. Mine seems to balance pretty well at CG without the covering and with appropriate weight to simulate motor and esc, which makes me pretty happy.

I took the model and plans out to the flying field today. Returned the plans to John, and let John look at what I've done so far. He really liked my changes from his plan, and will be doing those the next time he builds another Baby Kadett.

Caley
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thymekiller
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« Reply #7 on: June 08, 2009, 12:51:56 AM »

Thanks for the reply. I'm still in the learning phase and tend to ask questions. Will be looking forward to seeing how it turns out. Sounds like you have a handle on it.

thymekiller
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« Reply #8 on: June 08, 2009, 01:04:56 AM »

Nice looking Kadet, Caley. Be aware that after covering the airframe, it will be quite a bit more tail heavy since there's a lot more material being added aft of the CG. Just give yourself enough room to move the battery - VELCRO (hook & loop) is the stuff to use.

Pete
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crashcaley
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« Reply #9 on: June 08, 2009, 09:09:39 AM »

TK, No Problemo. Smiley I started R/C airplanes back in 2003, and have been on a learning curve ever since. Always learning something new. Kind of like free flight.

Pete, Definitely know the tail covering makes a difference. From what I've been told, for every gram of tail heaviness, you need four grams on the nose for balance. There will be help coming for that. My friend John, who did the design, is also giving me a fiberglass cowling. He makes his own cowlings for all his Kadetts.

Caley
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crashcaley
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« Reply #10 on: June 16, 2009, 06:41:39 PM »

Hi Everyone, I've finally gotten back to working on my Baby Kadet. I've not done much, but at least the control surfaces are covered, tail feathers and most of the wing. Only have the LE and wing tip to do on that, and it will be red. I am kind of short on plastic covering, so I am just mixing and matching as I go.

For those wondering what the heck are those little white strips on the flying surfaces. they are cut from an address label. I use them to mark the slots for the hinges, otherwise, these poor eyes would be struggling to find them later.

I got the cowling from John this past sunday. Really nice work. He makes all his own cowling and wheel pants.

I still have to design a motor mount. I had been waiting on the cowling, so I knew how long I would need to make the motor mount. Once I figure out how to do that, I will make a piccie and tell you how I did it, since I have to mount the outrunner motor inside the motor mount cage. This particular motor was never designed to have a rear mounting.

Caley
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crashcaley
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« Reply #11 on: June 20, 2009, 01:42:04 PM »

Not a whole lot more accomplished on the Baby. I've finished covering the flying surfaces.

But, the fuse covering has been delayed, while I awaited the fiberglass cowling from my friend John. I found the cowling didn't match my build. I must have goofed somewhere. So I will return the cowling to him, as I've measured things to make up a built up cowling. It is built up pretty much like the nose forward of the cabin. I will build a framework, then sheet the outside with 1/32 to provide more strength. The nose portion will be a sheet of 1/16 ply on which I will mount the motor. That sheet will be held on by four screws in the corners of the cowling. I will make them from basswood. If there is room, I will add a little balsa on the nose to give it a rounded appearance.

This way of doing a cowling is new to me, so I'm hoping it will work. I'm also hoping that this little motor has enough ooompf to power the airframe.

Once I get the framework done for the cowling, I will post a photo. And will post one of the finished product. Nothing like winging it as you go. Grin

Caley
PS No flying this morning. Dead calm here at my house where there isn't enough room to fly, but the dry lake bed had it blowing too hard for even the glow powered ones.
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« Reply #12 on: June 20, 2009, 02:34:12 PM »

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I'm going to try using one of my outrunner brushless types, a HET Micro 6/20 and Tsunami 10 amp speed control

Caley

I had a look on the web for your motor, and it appears to be rated at a max of 100 watts, with recommended model weights between 11 & 22 ounces. If your model weighs anywhere near your friend's at 3 1/2 lb, I suggest that your motor will be struggling to fly the model. I'm no expert on these things, and I suggest that you seek further advice before you mount the motor & finish the cowl. To put it into perspective, on my electric FF competition model, I'm using 100W to power a 7 oz model. It does go up pretty (very!) quickly, but six times the weight is likely to be too much.

Peter
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crashcaley
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« Reply #13 on: June 20, 2009, 02:56:36 PM »

Peter, Weight isn't the problem. RTF weight will be around 15 ounces. What I'm worried about is pitch speed, which can make launching by hand or taking off from the ground almost impossible, it that is too great. The motor is rated at 1800kV, though one of my model airplane programs has it listed at 1660kV. That means no more than a 2 cell lipo pack. That pack will be an 1100mAh pack. I much prefer a larger one to handle any surge in current, and also to give me more air time.

As for John's models and in particular his Baby Kadet, he tends to use the denser balsa in the 10+ pound range because he powers his models with glow engines. Lots of shaking going on with fuel engines. And, he uses Ultracote, which is a pretty heavy plastic covering. I use Coverite Microlite, which is about half that weight.

Caley
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« Reply #14 on: June 20, 2009, 08:45:59 PM »

50 watts per pound is, IIRC, the suggessted power for a good TRAINER. So, if the BK ends up with an AUW of, say, 20 ounces, you should be better than OK. With 2 cells, you can spin a slightly larger prop. Do you have the KV of the motor (I don't have my ScorpionCalc or my motor comparison chart at hand)? What is the recommended prop for the motor?

Pete
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« Reply #15 on: June 20, 2009, 09:20:28 PM »

Pete, kV is mentioned in post 13. This motor is used for both small heli's and small airplanes. Props recommended are 6x3 to 7x4. 7x4 provides to much power, and the prop I have on hand, a 6x4 is just a little too powerful, but may be workable if I use the throttle properly on T/O. I used Motocalc, which is pretty good. It gets me in the ball park. I just wanted to use the equipment I had on hand, instead of having to go out and purchase another motor/esc combo.

I wish I understood my brushed motors better. Would be nice to use some of them. I've got a couple of matched pairs, so maybe someday I can build a twin for these brushed motors and use my 8-cell 1950FAUP packs to power them. Anyone got a nice plan for a twin?  Smiley

Caley

Oh yes. I've nearly gotten the core framework for my cowling done. That's after designing one, and having trashed it because I was stupid and used the cowling as a guide, instead of the nose section of the fuselage. Second one is a much better design, though with a lot of wood in it.
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crashcaley
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« Reply #16 on: June 21, 2009, 04:47:13 PM »

Well, I goofed again, and forgot that I had already added thrust incidence into the rear firewall. But the big goof is my inability, for some reason to build something correctly. I got lucky in a way and I was able to flip the crooked nose I made around 180 degrees to get the near correct thrust incidences. Unfortunately, the nose points off to the right a lot. So I will be mounting my motor off center in the nose to get it residing in the fuse thrustline.

But, I am going with this, and hope that using the flying surfaces adjustment, I can get this puppy flying straight and level. If not, I'm threatening it with a new nose job, and with that statement I have it shaking on its landing gear.  Grin

You'll note in the picture the fiberglass nose that John made for me. Mine is based on that. I just made mine so it could accommodate the motor. All I have to add to the structure is the 1/16 to 1/8 inch ply, mount the motor and then mount it onto the front of the nose with four screws. The motor sits behind the forward ply firewall. The difficult part will be getting the motor centered where I want it. More learning to do.

Caley
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crashcaley
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« Reply #17 on: June 21, 2009, 09:37:34 PM »

I finally got the front firewall done. Thank goodness for the Dremel and its versatility. Could never have gotten all the holes done and in the right spot without it.

You can see what things look like from the front with the motor, prop and prop adaptor/nut installed.

The only problem is that what I thought would be sufficient prop incidence isn't there. So I will have to shim the firewall to achieve the desired angles. Thank goodness I designed the ability to do that with this nose contraption.

I found that I will not have the ability to add a nice curved add on in the front. It is the same problem as using the fiberglass cowling John made for me. The prop adaptor shafts aren't long enough to extend for that nicety. But who cares. As it is, it looks fairly good.

Caley
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thymekiller
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« Reply #18 on: June 22, 2009, 07:57:16 AM »

Correct me if I'm wrong. If you need to change prop thrust angle, on this plane, you adjust the furthest forward bulkhead with shims? That's what the outer screws are for?

I think I will go out and buy an outrunner motor. Any size. Just to play with. It should seem easy, but I struggle with the idea of mounting an electric motor from the front. The entire outrunner thing just hasn't "set" with me yet. Duh !! Embarrassed Any chance you could post a pic from above. ? Is it correct that the motor leads on your plane go all the way to the front, where the mount is? I "get it" with an inrunner. I am missing something with an outrunner. Embarrassed

Yes, a dremel is one of several tools that remind us how awsome those people were back in the day. These days , kits, parts, advise, and tools, seem to be everywhere. I don't think that "back then" it was common to own several hundred bucks worth of tools and such. Advise came mostly in the mail and from friends. I am constantly amazed when I see those old clips. Most of that stuff was all hand made, each notch, joint, etc. If you wanted/needed a different prop, you made one. Today, there might be 25 different props ,under 5 bucks each, just for rubber power alone. And proven results of each are just a click away. Same with servos, hinges, etc. Hats off to the early fliers.

thymekiller
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crashcaley
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« Reply #19 on: June 22, 2009, 10:05:46 AM »

TK, Looking from the pilots perspective, if I wish to add right thrust, I would shim under the left side. In this case, I also need down thrust, so I would have to shim on the upper portion also. So I will probably have to have a larger amount of shimming in the upper left hand corner to get things right. I will play with it until it looks right, then glue basswood strips and then sand the angle in. Yup, that's what the outer screws are for.

TK, most new outrunners have a mount that comes with them. It bolts on the back and then you just screw it on the firewall. Mine is older and only has the front mounting system. Because of this, I ended up mounting it inside a cage, behind the front firewall. This motor I have is probably six years old, so it is one of the original designs.

Yes, the wires go to the front of an outrunner motor, because unlike an inrunner motor with the center portion turning, an outrunner outer casing turns. Doing this way allows you to swing larger props.

Here's one link that may help http://www.rcuniverse.com/magazine/article_display.cfm?article_id=956 & Greg Covey is a super knowledgeable person. You might try Googling about the different type motors and their differences, advantages, etc.

I too, am amazed at the absolute skill and patience of the modelers of years past who had very little in the way of tools, other than some very basic ones. I could have spent several days making that forward firewall by hand with just a simple saw, hand drill, sanding block and round file, but the Dremel allowed me to do it in about an hour, once I had made the template.
Doing the template actually took me more time, because I had to make it as perfect as possible.

Caley
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« Reply #20 on: June 22, 2009, 11:51:06 AM »

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if I wish to add right thrust, I would shim under the left side.

Caley

Are you sure? Perhaps it's the photo, but it looks as though the motor is bolted to the back of the front bulkhead. If that's the case, shimming the left-hand side (from pilots eye view) will give left thrust, and the top will give upthrust.

As I said, it's difficult to tell from the photo, but I would double check.

Nice looking build though!

Peter
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crashcaley
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« Reply #21 on: June 22, 2009, 12:07:38 PM »

Peter, the photo is from the bottom of the fuse. Sorry.I had to do it this way to show TK where the wires ran to, though it is difficult to see as I beefed up the structure to ensure any vibration would be absorbed by a stronger structure.

I'm sure about the shimming. If I am in the pilots seat I want to shim on the left to make the right tip of the prop move right and back a tad. The motor is bolted to the front firewall on its backside. I've been doing electric rc for about six years, so this is a pretty easy thing for me.

I've already glued two 1/8 strips of very hard balsa on the top edge and left edge. Couldn't find any hardwood, so very hard balsa will have to do. I will sand an angle and test fit and keep doing that until I come up with the two thrust angles I like. I know 1/8 is a bit thick, but I'd rather start with a lot of wood, and work down, than have to keep layering, which can make things weak.

Once those are at the correct angle, I will build up the remaining parts of the front to achieve a flat mounting surface.

Caley
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« Reply #22 on: June 22, 2009, 03:46:24 PM »

OK, The mod is done and everything back together. Tough the picture shows what looks like a huge angle, it is really only 3 to 4 degrees of both right and down thrust. That should allow it to fly with some adjustment with the control surfaces. I've got ailerons, rudder and elevator to work with. Hopefully things will work out, or it is back to the adjustment board.

Caley
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« Reply #23 on: June 22, 2009, 04:38:58 PM »

I was interested in what things weighed right now, with just the fuse to cover, add the front windscreen and add the receiver and batter. It is a robust 13 ounces. So my guess of 15 ounces RTF were optimistic, and will actually be around 16 ounces.

I was also interested in how the CG is doing. I was quite surprised to find it balances spot on without any nose or tail weight. So, the addition of the covering and windscreen will balance those two items. That means that I only have the receiver and battery to position properly, very close to CG. Talk about luck.

Sorry for the clutter picture and the trash can in it. Real photographers never do this to others.

Caley
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« Reply #24 on: June 23, 2009, 01:50:32 AM »

Thanks for the link and the pic. I will figure it out. Gonna build my first r/c this winter. I think that when I can hold it in my hand , I will get a better grasp. Sometimes ya' gotta jump in and try, in order to understand.

Good news about your plane balanceing without alot of added fuss. It looks great.

thymekiller
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