BadSplice

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Hi all,

Wasnt exactly sure where to post this, but since Im looking for any tips, I thought it might be a good place

I bought a nitro models Kangaroo when they were having their "Black Friday" Sale, because I thought it looked kinda cool, and I want something faster than anything Ive got so far.

I am mostly very impressed with how it was built. It looks straight and feels strong, the covering was well applied, and it was obvious that wood glue was used throughout, rather than hot melt. The parts interlock well and all the joints look really tight.

Here are some pics of the plane right out of the box.

BadSplice

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The first problem I ran into was that the nose wheel retract rails werent right. They were build for a main gear type retract, and the hobbico ones I have would have stuck waay out of the body. Also, I wanted the wheel to be fully inside the body when retracted.

I thought it would be fun to make a new bottom for the body that would curve to make room for the wheel. Im still thinking of making a door that swings down in front of the wheel, and covers it when up.

I tore all the bottom sheeting off the plane and got to work.

First, I had to cut out the retract rails and move them farther up into the body. I put them in, reinforced them with some tri stock, and carved out a bit of the former to make the spring and actuator arm fit.

BadSplice

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Next I cut out former caps for the bottom, and so far only notched them for the center stringer. I glued them onto the bottoms of the existing formers, and also added a chunk of bulsa to the underside of the nose cone. (to attach the stringer ends to and continue the new curve to the tip of the nose) I glued the first stringer in, and that's as far as Ive got so far on the bottom.

My plan for the other stringers (was going to do 3 total) was to put them over the tops of the former caps, and trace along them to mark where to cut the notches. This way, I cen get them in just the right place to be on the sides of the door for the nose wheel. After all the stringers and sheeting are formed and on, then I will cut out the door area and the formers underneath. I just thought it would be easier to make a continuous curve, and then cut into it instead of trying to make the curve right and leave the wheel well open. Make sense?

By the way, I am freehanding all of this so far. I have no plans, except for in my head, and Im mostly working with a pencil, square, and xacto knife. I just hope I can get sheeting to curve over this

BadSplice

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I also had to do some customizing for the fuel tank. In fact, it would have been really hard to install it had I not ripped off the bottom I installed it facing forward, with the lines running around the bottom to the firewall. I made a spacer ring out of 1/4" ply for the hole in the firewall so a fuel tank stopper fits in the hole. I attached the lines from the tank to that. I wanted to seal off the firewall, so sparay from the engine (there seems to always be a mess around the engine) doesnt get back into the body. Also, the back of the engine sits very close to the firewall, and I didnt want the fuel lines to kink or wear against an edge from bending sharply. (and I just thought the plug was kinda neat)

BadSplice

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so, up till now, Ive been going on the plan that I would soak some bulsa sheeting and try to form it around the new bottom Ive made here when the time comes. So, now the time is here. I have all the formers and stringers glued in, and smoothed out, and Im ready to put on the sheeting.

First, Im trying to decide how to meet up with the sides of the body. Right now, theres sort of a notch where the curve of my new formers meets the sides of the body. (Sketch 1)

I could either: Butt the sheeting up against that gap. (Sketch 2) (the edge of the sheeting would butt against the bottom edge of the side sheeting)

or I could sand the sides of the body to continue the curve of the new formers, and have the bottom sheeting Overlap the bottom edge of the side sheeting (sketch 3)

Any suggestions?

Also, should I run the grain lengthwise, and attempt to cover the whole bottom at once? Or should I try to cover the bottom in sections with the grain going sideways? Or, should I butt together enough pieces to cover the whole bottom at once with the grain going sideways?

BadSplice

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Well, I had to go ahead and do it. I went with the first option, just butted the sheeting up against the edge of the side sheeting. If I had it to do over again, I think it would have been much easier if Id overlapped the sides.

I didnt do such a great job of going around the bulge. I mostly got the sheeting where I wanted it. I dont think I had enough framing under the curve, but I didnt want to get too heavy... So now I added some bulsa filler, and did a bit of sanding, starting to look pretty nice, though Im afraid the weight is starting to stack up. I will probably abandon most of my grand ideas for a door system, as moving weight back for balance on this plane isnt much of an option, and all of this is up in the nose.

Heres what I have so far.

steinericj

Very nice work! I also purchased one during the Black Friday Sale. I am very impressed with the quality. I am currently building the AK Models / Nitro Marie Mustang so don't plan to start building my Kangaroo for awhile. I was planning to put an OS46FX in mine. What are you using? Good luck on you build. I'll be following this thread closely.

JustErik

Nice work indeed. I'm anxious to see how it turns out. I'm not sure facing the tank rearward is a good idea, however. It seems like the clunk will not be able to draw fuel when your going up or when the fuel level drops. I could be wrong, but it's probably a good idea to retain some ability to get in there and move it around after the fact.

BadSplice

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Thanks for the replies

I am planning on using an Evolution .46 NT at first. Its been a really strong engine, so Im hoping it will be enough. I also have an OS 46FX, and thats also a great engine, if the evo works out, the OS should be fine. If it needs more power (I want this thing Fast) I have a ringed OS .60 SR waiting for a chance to be crammed in there

I wish I could make it so I could access the tank later, but I didnt want to make too many hatches. I figure, worst case I can tear off some of the rear bottom and fix it easily enough. I tried to put the tank together really solidly so there would be no issues. Actually, it is pointing forward. I read somewhere that that was necessary, for just the reason you mentioned, the clunk needs to go to the rear. The tank plug you see on the firewall has lines on the back that run around to the other end of the fuel tank. Used larger diameter tubing inside so it would hopefully not affect fuel flow.

Heres a few more pics of the bottom, almost done filling and sanding. Planning to put some monokote over the door area, then Fiberglass over that to make a piece of molded Fiberglass the exact shape of the bottom, then cut that out to make the door.

steinericj

Good point about the fuel tank! I wouldn't have thought to put the tank in backwards but it makes perfect sense. If you didn't put it in backwards you would probably loose fuel supply on a vertical climb out.

JustErik

Maybe I'm missing something. In the following pic, the black arrow points in the direction of flight, right?



If so, it sure looks like the tank is facing rearward. I really think the opening of the tank should face forward, that is, in the direction of flight. Am I totally on the wrong track here?

BadSplice

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sorry to say, but yes actually, the arrow is pointing towards the back of the plane. Since the plane is a pusher, everything inside is backwards.

Looking at that pic again though makes me realize it is long past time to clean off the table again

JustErik

LOL...Now I get it. Somehow the fact that it was a pusher escaped me. I'm not familiar with the plane in question, but that's no excuse, right? It looks like you've got it all figured out. I'll just sit over here under the dunce cap and wait for mor progress reports.

BadSplice

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Hehe, dont feel bad On 99% of planes, that would have been the front. And I cant exactly say Ive got it all figured out yet More like Ive muddled through most of it so far.... hehe

Ordered the retract servos (going to use 2) and the servos for the elevator, and to make the rudders, as well as a 50' spool of wire. Ive read enough about connection problems Ive decided to go to soldering my own extensions, rather than buy the plug in ones. Im a little iffy about having 2 servos hooked up to the elevator, and I dont want to buy a matchbox also. I read a thread somewhere about using 2 channels on your radio for the 2 servos, and using the travel ajusts to make the servos match up. ( I have the Futaba 7Cap) Hopefully that works, I'll already have enough gadgets in this plane. I dont want it to end up too heavy, or it wont go fast enough

Prolly wont get much done today unfortunatly, after work we have our club meeting tonight. Planning to take the plane for show and tell, and to see if anyone has any great ideas for me

steinericj

I also questioned the need for two servos on the elevator. If you decide to go with one, you'll probably need something strong to overcome the force from the propwash. Good luck!

BadSplice

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I thought about just using 1 servo, but I was afraid of the surface "Twisting" under the force. Because of the Prop, you cant easily make the pushrod push on the center of the elevator. (or even close) I was afraid if I just had the pushrod connected to one end of the elevator that the prop wash would twist the other end.

Wonder if I ought to make another elevator out of stiffer material. With all my mods in the nose, Im not too worried about adding a small amount of tail weight. And because of the shape and configuration of the plane, 1 oz on the tail only = 1 oz on the nose, instead of 1 oz in the tail = 3-4 oz in the nose. Like when you have a short nose and long tail.

Im very interested to see how the elevator feels with the propwash hitting it all the time. With the rudders and elevator so close, should be kind of like Thrust Vectoring. Mebbe I can do some 3D (Saw an awesome video of a guy hovering, flat spinning, and generally flipping a large turbine jet (Mig 29) that had to have had Thrust Vectoring)

BadSplice

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Got a bit more done tonight. I think I'm pretty well done with filling and sanding the bottom. I will go over it with finer paper before covering, but the shape is nice and smooth.

I started in on the landing gear setup. Unfortunatly, when I tried to bend the wire for the mains, both of them broke before reaching 90*. Either I will get new wires, or the axles that slide on to the end of these, I haven't decided yet. Adding the curve to the bottom of the plane made a bit more room for the main Retract Servo, but still is a very tight fit. I took a pic of a standard servo sitting there, hopefully the retract servo is that much shorter. If not, I can carve a bit out of the last rib in the wing, and the corresponding hole in the body to make the wires sit higher.

BadSplice

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I have some options for the front gear door.

Option 1: An open bay with no doors. (obviously the easiest and lightest, but most drag and least "cool factor")

Option 2: A door at the front of the bay that swings forward along with the gear arm, and the rear half open with no door.

Option 3: A door at the front of the bay that swings forward along with the gear arm, and a door on the rear half that swings back. Rear door would be driven by the retract servo. (afraid that the door on the back will "scoop" and just get ripped off, for that matter, slightly worried about the front door for that reason)

Option 4: A door at the front of the bay that swings forward along with the gear arm, and bombay type doors on the rear. (would either require yet another servo, or some complicated mechanism to drive off of retract servo)

Option 5: Bombay type doors for the whole compartment. (again, servo or mechanism required, but probably maximum "cool factor")

Some pics to help visualize...

BadSplice

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I also started on the rudders. Here is what Im thinking of doing... Used some aileron stock I had sitting around. Does this seem like the right way to go about it? or should I make new fins that have the rudders built into them. (or mod the existing ones that way)

Threw in a couple profile pics of the body to show the new shape

steinericj

With all the mods you are making you'll have to put the word experimental in front of Kangaroo. The rudder idea sound very cool. Probably be able to do flat turns with them. Aileron stock should be fine. I checked my vertical fins and they seem stiff enough. Only question I have is where are you going to put the servos? That wing must be getting crowded. I have been looking for other threads or possibly a U Tube video on this ARF but am unable to find anything. Have you seen anything? I've see jet versions of the Kangaroo fly here in Pennsylvania but never a pusher version. Hope to have my Mustang done in a few weeks so I can start the Kangaroo. The weather has not been good for flying here in the Northeast. Good luck!

BadSplice

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I haven't been able to find anything else on this plane either, which is part of what has motivated me to keep putting everything in this thread.

The wing is indeed getting a bit crowded, but I found a good place for the rudder servos. I made hatches on top of the wing just outboard of the center of the vertical fins. (I am getting good at making these hehe) I plan to have pushrods running up to the rudders about 1.5" from the bottom, this way, the linkage will clear the aileron. My only concern is that the pushrod will be at about a 45* angle to the control surface, instead of the ideal 90*. I may use a ball link to keep them from binding when they twist.

I am thinking of making hatches for the aileron and elevator servos also. I dont much like the idea of the servos hanging out of the body on what is supposed to be a fast plane. I was also thinking of putting the elevator servos right into the horizontal stab. I am using Hitec Hs-81s for the elevator and rudders, as they are fairly powerful, and fairly small and light as well. The small servos will just fit into the stab, making the linkage very short, and also making it so it doesnt cross the line of the prop. Im hoping that moving all this stuff back will help offset all my mods in the front, without adding undue extra weight.

As for the name, I've never been too thrilled with "Kangaroo". I think the plane looks alot like the ParkZone F-27 Stryker, and I usually use 77 as my number on planes; so I was thinking of calling it the X-77 Striker. What do you think?

steinericj

X-77 sounds good to me. Not sure if you saw the attached link. Looks like this guy is adding rudders also. Not sure when I will be starting my Kangaroo. Good luck!

http://www.rcuniverse.com/forum/m_67...tm.htm#6732742

BadSplice

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well, Ive been picking away at various things, but I havent made a ton of solid progress. I decided to take a stab at making a fiberglass piece to be a gear door for the front. But when I went to get some fiberglass, both of the local places I knew carry it were out. So I decided to get creative... hehe

First I drew out the desired gear door, then stretched a piece of saran wrap over the whole area, making sure there were no wrinkles. Then I took a piece of really strong paper towel material (has some kind of cloth woven in) and cut it to size. I mixed up some regular 1 hour epoxy, and spread it really well into the cloth, squeegeing out the excess, then let cure for 24 hours.

Next I cleaned it with acetone really well (the epoxy releases some kind of paraffin right?) and did another layer with some strips of fine fiberglass cloth I found somewhere After this cured, I found that I had a nice thin piece of "fiberstuff" that is reasonably strong, but quite flexable.

Now the quandry is how to make a good gear door, or even IF ill make a door. any ideas?

BadSplice

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Heres some pics of the Rudder servo hatches, as well as my start on the elevator servo hatches.

BadSplice

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I also got the retract system all installed and setup. Ended up having to make new struts for the mains, but I like them better without the coil, though I had to bend them creativly to make them close all the way, man those wings are thin.

I stripped the covering off the bottom, and plan on re-covering it in Cub Yellow. (have an extra roll from another project, hehe) Originally, the plane had the same colors on top and bottom. I know from experience that that is a visibility nightmare. Hopefully this will contrast well. Thought about doing the rudders in yellow, but that would put 4 different colors on the tail fins, so I decided to just stick with black for now