Pit-Viper 1

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Got a question about CG. Should this plane have the same characteristics when balancing as most other planes do? What I mean is when I have it on the CG machine and you push down on either end, providing it's close to level, it should come back to its nuetral position and rest there, correct? Well on mine you it doesn't "rest" in one spot, if you touch the nose or tail it will fall to that end without coming back to its nuetral position. Hopefully you understand what i'm talking about.

I'm using the RCV.91 CD w/ 14oz tank, dual aileron servos and it weights just under 8lbs. It flies great it just has some really bad tendancies on landing. This thing will bounce down the runway no matter how slow or fast you bring it in. I've added and removed wieght to try and help this but nothing works. I think it has to do with the whole CG problem, just not sure what to make of it.

I'm not new to planes by no means and flown all sorts of planes from trainers to warbirds and haven't had this trouble before getting a plane to balance without falling off the balancer or bad landing characteristics. It almost feels as if there is to much wieght centered around the CG area causing it to tip the way it does, sounds weird but that's the feel it gives. Any ideas?[sm=confused_smile.gif]

Thanks Shane

Mustang Fever

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Shane-

Are you doing this with the plane upside down on the CG machine? That's how I balanced mine, and it sits perfectly level and still. Now, that's not to say that it won't go one way or the other if you rock it too far. Remember that the masses inside the plane (engine, battery, servos, etc.) get closer to the desired CG point when you rock the plane away from level, (cause they travel in an arc about the pivot point.) so the CG will change according to how far away from level you are, and the plane will accelerate off the machine if left to it's own devices, even if perfectly balanced.

The only time mine bounces on landing is if my rate of descent or touchdown speed is too high. I always try for a 3 point landing, and the worst I get under that condition is a very slight bounce. I just hold the elevator wherever it was and it settles back down. Don't be tempted to "dump" the elevator you were holding at touchdown. That's a good way to dig the nose in, and is something a primary flight instructor in full size will smack you for.

Bob

Pit-Viper 1

My Feedback: (12)

LOL, I know the feeling with those instructors. I think I did balance mine right side up, I knew better but was following a fellow builders advise. That may be why i had to actually pinpoint the balance point and hold it there or it would topple off forward or back.

Just to be sure of myself, most low wing planes are balanced upside down and high wings right side up? Thats how I've always done it anyway. Thanks for the help..

Shane

w8ye

My Feedback: (16)

I mounted my landing gear with the tapered side towards the front so the wheels would be farther back. I could touch down on the mains with the tail high without the plane bouncing back up. Didn't tip over either.

WorldTraveler

I've had two 4* 60's, and i took the items on the decal sheet that is a circle w/a plus sign in it and mounted them on the side of the fuselage, one at the fwd of recommended CG, one at the aft one. then, balanaced the planes to the center area. This resulted in a slightly nose heavy balance when flying, but the airplane balanced level. When I wanted to explore other areas of flight, I moved the CG slightly aft, which resulted in a faster response to the flight controls in pitch. Unfortunately, the demise of these excellent aircraft was MY fault, not the plane. Presently, I'm putting a Venture 60 together, from Bruce Tharpe. it's easier to see these markings when looking under the wing, and not having to look up, but at the side of the fuse.

Clint[&:]

Pit-Viper 1

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After rechecking mine upside down, [sm=tongue_smile.gif] it turned out that it was still nose heavy. In total with the RCV.91 and 3" tru-turn spinner it needed 1 1/2 oz to balance it out properly.(had to add another 3/4 oz after checking it right) This would explain why it would drop the nose so drastically under half throttle, when at landing speeds a little down on the gimble was neede to keep it from trying to lawn dart into the runway. lol I thought something was afoot after flying the 4* 40 we had as it would almost land itself. Can't wait to get this back up and try it again.


Shane

Mustang Fever

My Feedback: (2)

I think you've got it, now. Low wing= balance upside down. High wing= right side up. Usually, anyway. Depends on where all the masses are relative to the wing location.

I've got my 4*60 balanced on the rear edge of the main spar. (Aft limit, according to the plans.) Flys real nice, land or sea.

SMITTY1820

Hello Gang,

I have read alot of things about the Four Star on this thread, Alot of things have been helpful such as changing out the pushrods, axles, engine selection, and such. Can anyone help me on either purchasing or building a cowl for this plane?

Mustang Fever

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I have a Precision Fiberglass cowl that I bought for mine, and decided not to use. It's new and untouched, and looks kinda like an Extra. If you want it, I'll let you have it for $15.00, which is half the new price. You catch the shipping.

SMITTY1820

I sent you an email - I am going to need your address so I can send you a check. Included in the email is my email address, thanks for the help.

Greg

Mustang Fever

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Greg:

Your email hasn't come through, yet, anyway. I sent you one with my address through the forum. I live in Cadillac. We're going to be in the Detroit area on the 24th of September. I could save you the shipping costs by meeting you somewhere on I-75 if you like.

[email protected]

Thanks,

Bob

FlyingGreg

My Feedback: (4)

My $.02.

I'm into my second 4*60 (first one got caught by a tree). OS .91 for power but I did have a ST .60 with tuned pipe for a while. Like someone else mentioned, it was way too slimey. Mine is a kit. If you have never built the 4*60 kit, you are missing quite a pleasurable build. With the exception of the balsa spar doublers, no glue is used until the wing half is completely assembled. Then you just dribble a little thin CA over the joints. All laser cut and everything fits great. The fuse and tail feathers are conventional build. the 60 is different from the 40 the way the wing is built, and I don't know about the 120. For my flying though the 60 is best. I agree with changing out the tail wheel to a Sullivan and the pushrods, although I am using stock pushrods in mine, I want to switch. Great flat spins and KE flight. Floats in for landing at a crawl. Hard to beat. I've had my current one for about 5 years.

ziomarco

Hi Flyinggreg

What prop/pitch did you use when you had the 60 in your 4 star ? I just maidened my 4 star 60 with an OS 61 SF and find the vertical very limited. I flew with an APC 12 x 6 prop.

Thanks,
Marcus

Pit-Viper 1

My Feedback: (12)

Well now I just need to get my motor back and I will be set. Decided it was to plain just orange so I through some stripes on it. Want to fly it before I stripe the fuse though. Here's a few pics. Got a couple holes in the top of the wing on a dead stick into tall grass. Didn't hurt the bottom though, damndest thing.. Seems like a descent patch job..

Shane

FlyingGreg

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Ziomarco--with the Super Tigre 60 and pipe, I used an 11 x 7 Master Airscrew. APC probably would have been better. I could barely get 12,500 with the 12 x 6 and stock muffler. With the pipe it really came alive--I'm thinking in the 15,500 range but don't remember exactly. Problem was I kept breaking the screws holding the aluminum spinner on and after losing 2 of 'em I put the 4 stroker back on.

Pit Viper--thought maybe you were a Cincinnati Bengals fan with that color scheme, but probably not if you are in Colorado-LOL (looks good).

hosam

My Feedback: (121)

Guys,

I wan tot bring life back to this thread… I just purchased my second 4 star 60 as the first was crashed due to a radio problem; its fixable but want to improve on the first one. The first one had its wing shortened by 6� (1 bay per side was taken off), 2 servos in the tail eliminating the rod flexing, battery under the tank and Rx as far forward as possible. Super Tiger 75 gave it unlimited vertical. The plane was a tad tail heavy but that is how I like to fly my planes.

Now for my questions, has any one built the wing with little to no dihedral? If so what was the out come (i.e. better knife edges)? Also thought about building the tail so it is removable, similar to all those PNP planes by Hanger 9 and the UCD 60 size, any thoughts. I will increase the length on the tail by an 1.5�, the elevators by a 3/4�, any one change the size of the ailerons? I have a Tower Hobbies 75 that is well broken in and should be great in this plane. However, I would consider a 90 if I run across a good deal. I also have a Saito 91 but want the speed and power and I don’t think the 91 can handle it. All comments would be helpful,

Cheers,
Hosam

FlyingGreg

My Feedback: (4)

Hosam--One of my buddies built a 4* wing that was fully symetrical rather than flat bottomed like the kit. He left some dihedral in and it flew great. I don't recall it being radicaly different than stock though. I extended rudder on a 4* 40 and it seemed to flat spin better than my 60, but I don't know if longer tail had that much to do with it. I like your idea to put dual elevator servos in tail. You might want to consider HS225 minis. I have them in an Ultimate and they work great. As far as engine and speed, why go to the trouble to make a 4* go fast? I like the OS 91 on mine. I had a 61 2S with pipe for a while, only because the 91 was on another plane and I missed flying the 4*. It went a little faster, but wasn't nearly as much fun. If you want fast, get a Shoestring, Minnow or something similar. I shortened the wing by one bay on an earlier 4* but honestly didn't notice a lot of different flying charecteristics. The neatest 4* mods I have seen have been with cosmetics. Such as cowled engine, different canopy, wheel pants, rounding the elevator/rudder profile--that sort of thing. And covering. I have mine covered like a chipmunk because I like chipmunks. My 40 size looked like a PT 19. I just don't think you will be able to modify the airframe to the point that it will perform any better than stock--at least not by much. Others may have different opinions, but that's my take. (Since you asked.)

Fuel Dinosaur

2 aileron servos. Flies great and lands like a trainer. Fuselage to tail a little weak, just put some solid balsa in between the sticks where the fuselage meets the tail. Saito 100 fine, I have FS-91S on all three of mine. One a second plane, you can shorten the wings a bit for faster rolls. WOuld leave it stock first time and use 1/2 throttle on your 100 the first few flights. Very relaxing plane to fly, flies well and there is always room for one (or three!) in your hangar.

Pit-Viper 1

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How does it fly with the Saito 100? I just converted my 4* 60 from a RCV.91CD which was way to heavy for this pane. It now ways 8lbs. even. Thing with the RCV was it would litterally drop once power was cut, instead of the usual glide like 4*'s do. Weather was a bit to cold on Sunday to try it only cause I still had the nylon rods in it and the temp was only 2 degrees above 0 with a 16 mph wind. bbbrrr The rods don't like that, besides I wanted to change out the control horns to GP metals before hand, plastic tends to get a little to briitle in these kind of temps. Gonna take the end bays off the wings as well. Should be a whole new animal when finish.

We did still get a few hours in with a PT 40 we build with no dihedral, its a rocketship with an OS.50 on it. No dihedral in the wing will change the way the 4* flies and lands especaily, this thing just floats and floats. You need to bring it in with a slight nose up from way out to get it too slow enogh to put it down, it is a blast to fly though. Straight and true..


Shane

g3steve

Mine flies increadible with the saito 91 more than enough power for the 60 and i make her dance -very forgiving plane ,ENJOY

w8ye

My Feedback: (16)

I had a OS 91 Surpass Four stroke on mine. It had plenty of power.

Darklotus

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GP metals?

Just thought I might clear something up...

The purpose of positive dihedral is to confer stability about the longitudinal axis (roll)

http://en.wikipedia.org/wiki/Dihedral

Pit-Viper 1

My Feedback: (12)

LOL get back to class... This is the guy I refer to when I use the term "we". It's his PT-40 we fly. Where you been, can't find no 4-40 rod to change out the control rods. Wonder if 2-56 rod with the nylon rod cut into 1/4" pieces and put over it every 6" then inserted back into the guide tube would be ok. That sounded weird.

Later

Fuel Dinosaur

Nice flying, relaxing plane. Have 3 Four Star 60s, all three with Saito FA-91S engines in them. I beefed up where the fuselage meets he tail section, around those "sticks" with solid small pieces of balsa and 30-min epoxy, a little weak there. I would sheet the top and bottom wing from the leading edge to the spar with 1/16 balsa or similar (thin ply, etc). That greatly decreases those grass dings and the like from poking holes in your nice covering. I did trim about 1-1.5 mm on the formers and put in 16 ounce tanks in all three. Most folks would find 12 ounces more than enough. The method to this madness is that I can fly a full 15 minutes and have plenty of fuel for a couple of flyarounds if the landing strip is occupied. Last, I think I used 3 1/2 inch wheels and can take off in grass from almost any local club with ease. Some people shorten the wings for a faster roll rate, but I would leave the first plane stock except for beefing up the fuselage to tail link and sheeting the wings to the spar. The Four Star 60 floats on landing and you can almost land it at a walk. I always plan to have a few of these planes in my hangar. Terry Joe Sprinkle (The old fuel mixing dinosaur)
\
PS - I do agree to add sturdier pushrods to this plane, 4-40 or so, forgot to add that above.

Darklotus

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yeah it did

Don't see why not. Only thing might be the bushings, are they small enough for 2-56? 4-40 would prob be the better choice tho.