pojarnii

Hey gang, I finally got my Jug finished and have flown a few flights with it. The first was powered by a Saito 120. It wasn't pretty and was a real handfull to get back on the ground in one piece. I promptly swapped to a 150. It pulled the Jug no problem with a comfortable amount of reserve power.

The Jug weighs about 13 lbs with the balance weight in the nose. It was glassed and painted with latex.

The plans indicate a CG which seems very far forward of the main spar. I can only just barely make it to that CG with about 1.5 pounds of weight bolted to the engine mount. I already have a brass hub on the nose.

The plane flies great but when I bring it in for landing it gets very pitch sensitive at slow speeds and when the mains touch down in a 2 point landing the plane flips Axx over tea kettle. 3 point landings are out of the question at this stage.

Also, the plane is so nose heavy during taxi that it is very difficult to prevent the tail from coming up and the prop hitting the dirt. Only a small gust from the tail will cause this to happen.

One suggestion I have heard is to build a spacer under the aft gear mount and thus move the wheels further forward. This sounds like it might work but I haven't tried it yet. Opinions?

My questions are:

What are the flight characteristics of a nose heavy plane versus a tail heavy plane? I'm no aeronautical engineer but I've been trying to figure this one out. Any help?

When I'm flying, how will I know if I can move the CG further aft? Ultimately I would like to be able to taxi without fear of nosing down and hitting the prop and I would like to be able to make some better 2 point landings with the option to do 3 point.

So far I'm really happy with the Thuderbolt and satisfied that my 9 months of work were worth the effort. Now I want to make some nice landings and taxi the plane back to the pits!

Rickles56

I have the same problem with my TF Spitfire. If I give it just a little too much power on take off or taxi it noses over. I am destroying props way to fast. I think it is just a matter of learning how to slowly add power and keep a slight amount of up elevator on it until the wind takes to the tail feathers and it can be pushed into the air. It makes for a long take off. I haven't tried using flaps yet for landing or take off but I am thinking that might help as well.
I have the same problem with landings. I keep the plane coming in fairly hot and it drops onto the mains and uses up a good amount of runway before the tail drops. My problem here has been when there has been any cross wind, which is almost always a little, I have to keep some rudder on it to keep the plane straight down the runway and the tail wheel grabs and nearly flips the plane over in a ground loop because of the short distance between the mains. Again, I think this is just part of the learning curve for these nose heavy warbirds. Adjusting the CG is going to affect the way it flies and my Spitfire is great in the air. I had to go up a size in props with my .91 4-stroke. The smaller one just didn't have the thrust to get the plane moving fast enough. It flew like a brick with short wings before I increased the prop size. Now it is much easier to handle in the air.

Good luck, hope this helps a little.

c550

My Feedback: (16)

I would ensure that you are close to what Top Flight calls for as to cg. As you move the cg aft the pitch sensitivity will increase. If it begins to get too sensitive for your taste. then move it forward a little. I have the same model with an st .75, and I needed no nose weight to balance, it is the best flying warbird I have owned. So it sounds like you have the cg very far forward. Try to move the componets aft as you don't want to add weight if you can help it.

Hope this helps,

Dave

pojarnii

Thanks for the tips guys. I went back to the bench and balanced the plane again. I used masking tape to indicate where the plans called for the CG and where I was at last flight. Last flight was a good 1" aft of where the plans called for CG. I added more weight to the nose and split the difference. Now the plane really wants to tip over on the nose at the slightest bump. The plane flew well and was a bit easier to land, however it flipped again on the roll out. This time I did some more significant damage, cracked the rear spar on the horizontal stab and bent the landing gear. I guess it shows how strong I built the landing gear mounts, they are still solid but the gear strut bent about 30 degrees.

To me, the gear is designed too close to the CG. I would like to have a tail that is much heavier during taxi. I know I don't want the CG too far aft during flight but this taxi business is really disturbing and I'm ready to try anything to fix it.

I'm going to have to repair the horiz. stab which is going to add some weight to the tail, not what I want but it must be done. I'm at a bit of a quandry now, the plane flies better with all the nose weight but the tendancy to flip over is unacceptable. I'm thinking about scrapping the CG that the plans call for and moving the CG aft again.

Still open to ideas.

camdyson

I have the same plane, weighs 13 pounds with no nose weight except brass prop nut - it's full glassed and detailed hence the high weight. I have packed the rear rails of the retracts as far as possible whilst still retracting into the wing enough, and the CG is EXACTLY as per the plans. With the wheels this far forwards, it will taxi ok but is easily tripped on it's nose if hits a bump - needs well mown grass.
Moving the CG rearwards will help taxiing but at 13lb you're then at risk of the dreaded tip-stall. I'd just get the U/C angled as far forwards as you can and taxi carefully - they fly GREAT at your weight and the specified CG.
Good luck,

Cam

P-40 DRIVER

You should leave your plane at the facotry balance point although I would double check it with somebody competant to make sure it is where it needs to be. As for the nose overs, you can shim the rear part of the gear to rotate it forward. I think alot of your issues may be in the wire struts flexing under all that weight. A set of struts and some foam inserts for the tires might help keep the gear under control. At 13 pounds, I hope you are using flaps because your landing speeds must be high. I suspect you may never get this plane to the point where it is easy to manage, It's just to heavy to be a fun plane to fly. One thing you need to do when wheel landing is get the tail on the ground as soon as possible because you will loose the rudder fairly quickly and you will need the tail wheel to avoid loosing control on roll out. I your plane is very pitch sensitive at factory throws, you are tail heavy and if the plane seems to slow down and try to stall when coming in your tail heavy. Get some expert help to determin what the deal is with your cg before you spatter your plane.

c550

My Feedback: (16)

I think low@slow hit the nail on the head. Try using Robart struts and shim the rear of the retracts to get the wheels out front. The foam inserts are also a good idea. Asthe model moves forward the wire struts are dragged rearward(the spring in the gear wire is designed this way). Once they drag a little too far back you nose over. I have flown mine off of grass and it is managable with struts.

Regards,

Dave

Shihtzutan

I'm surprised you had any trouble at all! Mine flew perfect and landed perfect, with no tendency to flip at all! A c.g. more aft will make your controls much more sensitive. One of the issues, especially with smaller scale warbirds is that they have to fly faster to overcome drag because air molecules cannot be scaled; touchdowns are relatively faster than scale and the resistance on your wheels at first contact more problematic. Learn to settle your landings while keeping some forward momentum. I did use larger 3.75� wheels and Robart retracts, not the 650’s per the plans, the beefier metal housing (the next size up) and they worked great! If they interest you I’ll look up the number and get back to you. My jug also weighed 13 lbs. And I did not have to use any added nose weight; it was perfectly balanced with a Saito 1.50 on the nose (aluminum Tru-turn scale hub), no brass hub! So I’d say something is up with yours. My only issue was with the location of the fuel tank; I had a problem with fuel siphoning.

pojarnii

Shihtzutan,
I'm surprised that your Jug is 13 lbs and balanced without any weight at all. Mine is about 12 without weights but way out of CG. I'm going to get someone to double check the CG but I'm pretty sure I have measured right.

I'm curious what kind of struts you are using? Someone else suggested that my wire struts may be a source of problem and their arguement makes sense. I'm hesitant though to drop another $150 into this project if I'm not sure that I've found a good cure.

Thanks again all for the help.

Poj.

bigtim

My Feedback: (13)

I am currently building the 60 size jug and this is pretty interesting stuff a suggestion on struts, you can always go with Robart robo struts since you already have the retract bodies.
I decided to go with the century jet retracts for this build since I liked the scale look that they had, but I have the robostruts in my TF Spitfire and they are also fine.
you can also bend the wire you use to attach the robostruts. bend them slightly forward for more rake TF recomends this for there spitfire model to prevent nose over.
a note on my build I am using a small gas motor so servos and radio gear will be in the rear of the radio compartment I have a retractable tail wheel hoping I won't have to add weight to the tail for balance, the engine weighs 5 oz incl ignition, more than a OS 120fs so we shall see here is a pic of my engine spit in the background

SMUGator

We just maidened ours and it's definitely "tippy" at about 13 lbs. We used SpringAir retracts with RoboStruts. It rolls alright, but if it catches the slightest divot on the grass field that you have to "goose it" over, it tips. I'm going to try shimming the back rail of the mount to move the wheel forward a fraction. It flew well, so I hesitate to move the CG. Tracks like a missile when the tail is up!

Tom

bigtim

My Feedback: (13)

hey tom the blond looks smooth, lucky me our field has a astro turf runway and is pretty smooth its self what engine are you using and do you have a weight for it available

Shihtzutan

I used Robart 530RS and the struts to go with it. No problems at all tipping on turf with 3/-12 inch wheels. No nose weight needed with a Satio 1.50, APC 16-8, and tru-turn hub.

SMUGator

It has an OS FS 120 pumped. Don't have the weight handy but it's easy to find online.

Tom

camdyson

My struts are mounted angled as far forward as the wing allows - any more and the wheels hit the top skins and/or protrude. Couple of pics attatched. BTW, retracts are Custom Retracts - Australian - made for this kit.

Cam

US185Damiani

Gentleman,
I have had problems with the Robart wheels. They're too soft and will cause the airplane to tip over since at 13# it is akin to having flat tires. Robart sells a foam insert to install in the tire to stiffen it up and recommends it for heavier planes. I had to use it in my Corsair and it solved the problems. On my P-40 I replaced the Robart wheels with Du Bro 4" Giant Scale wheels and have had no problems whatsoever since with noseovers. If I had known about the foam inbserts for the Robarts earlier I would have used that option as I like the look of the Robart wheel/Tire much better!

Warbird Man

My Feedback: (95)

Are you balancing the plane upside down with the wheels retracted? It can make a difference. Definetly get rid of the wire gear. They can't stand up to the weight or stress.

This one is glassed, has a RCS140 "gas", CJ retracts and 3-3/4" stock robart wheels and weighs about 13-1/2 Lbs. It flies great and lands very easy without the flaps down. C.G. at shown on plans.

The plane is alittle tippy (as most all TF 47s are) I just use more up elevator to keep the tail down until it gets rollin abit and slowly let off and allow the tail to come up, Then gain some speed and pull back a fuz and let it break ground. Then I switch to a lower rate for flying. (Just make sure you switch back for landing) Or one could dial in exponential instead of switching rates.

I would use the heavier robarts as previously suggested instead of CJs as mine tend to bottom out while taxing on rough grass.

I know it cost more money for good retracts, but thats all part of flying warbirds.

Rule of thumb: Cheap retracts = pile O' junk

Also, a good .91 4stroke has plenty of power to fly this plane.

(Just my 2 cents)

bigtim

My Feedback: (13)

the robart wheels are soft my spit weighs a little lass than 10lbs and the wheels look flat, the foam inserts will be going in soon the look of the robarts is closer to scale so I will be using them for the JUG also.
Warbirdman I already have the CJ retracts and they seem pretty sturdy any other problems you have encountered other than bottom out if it becomes a issue I might see if I can put stiffer springs in them I fly off astro turf its close to concrete.

Warbird Man

My Feedback: (95)

The CJs do "OK", I think they could be built alittle better as they tend to get sloppy after awhile. The only "major" issue I've had is with the upper scissors mounting blocks to the outer strut shaft. They seem to be just crimped on and I have had a wheel turn side ways on me upon landing. (not a good thing) Fortunately the damage was minimal. I also don't think they can handle the weight they are rated at. Of course you can get the best retracts made, but if you bounce one in hard , somethings gotta give.

The TF P-47 is a very good flying plane and lands easy compared to some others warbirds. Alittle time and practice and you should have no problem "grease'n it in on the mains." ( 2pt. landing without bouncing)

aghost

My Feedback: (13)

Warbird Man - I CJM retracts on a FW-190. An upper scissor mounting block turned when I hit a really rough spot on the field. CJM recommended putting loctite on the upper scissor mounting block/strut when putting the block back in place. That seem to help considerably. Otherwise you are depending on just a tight fit to hold the scissors.

Brian

Rosster6028

My Feedback: (57)

Ah yes, the noseover issue. My TF Gold Edition P-47 was the first one I did in 1998, powered with an O.S. 91, Robart 606HD Retracts with 3/16!QUOT! Wire, 4.0!QUOT! Wheels also from Robart. Epoxy fiberglass finish and lots of weight up front. Underpowered and tippy on takeoffs, it was my best flier by far. TF Gold Edition Spitfire and P-51 Soon followed. I mention these others for two reasons. First, Top-Flite is a complete product. Their manuals are spot on and the balance points were always spot on as well. I built 3 of their birds and each one was an excellent experience. I am now building the GS P-47 and the GS Corsair is in my possession also but still in the box. Second, every one of these aircraft, save for the P-51 nosed over. But more on that later.

The P-47 was built with 3/16!QUOT! wire gear, as I mentioned before. So was the Spitfire (The Spit also used Robart 606HD's). The ground handling on both was atrocious, but a badge of honour could be earned if you managed a takeoff in one shot. Rudder corrections had to be immediate, elevator had to be managed to as to keep the bird on the ground in order to attain flying speed, but not too much up or down for obvious reasons! A quick way to lose one of these was to take off before flying speed was achieved. I've seen it happen and it ain't pretty! The main advantage to the 3/16!QUOT! wire in the gear was the 'live to tell' situation you ended up with. I would not build one of these with struts, not this size. It's just too small and there is not enough surface area in these wings to support the 'crowbar' effect that struts create in these wings! Read on below for where I'm coming from with this.

The P-51 was built in the same manner as the P-47, except I used Spring Air retracts with Lyte Flyte 1/2!QUOT! Diameter Struts and 4.0!QUOT! wheels. VERY NICE! Beautiful, very scale and ultimately perfect. The ground handling was poetry. The O.S. 1.20 put just enough weight in the aircraft that no additional weight was required. Weight on this one came in at 12lbs, 8oz. From the maiden flight, the balance point on this one was right on! I never nosed it over. HOWEVER, here's where the fun part started. I knew before I built it that a 3/8!QUOT! diameter 6061 T-6 Aluminum strut that was 5!QUOT! Long could generate some serious leverage on the wing. I built the support mounts out of Maple (Thanks Dave Platt!) and really made a solid setup in that wing anticipating extra stress from the gear. Granted, this wing is not as thick as the P-47's, but bear with me. Sure enough, on a windy day on flight 10, I hit just hard enough on landing to crack the wing spanwise on the port side. I fixed it, but the damage was done. Later, after more flights, that side of the wing gave way, putting excessive pressure on the starboard side which completely gave way causing significant damage to the wing. The fuse was fine, so I built another wing. Same thing happened again. Do I land well - yes, but I've had better landings!

So this aircraft is on it's 3rd wing, this time the difference is the struts are gone and we are now left with Spring Air retracts with 3/16!QUOT! wire. I ran it all this last summer. No problem with the wing - it's holding up just fine, not a scratch. Ground handling, however is just like that P-47 and the Spitfire. Technically, it's complete and utter chaos. With the tailwheel tracking perfectly, it's now a game of balance with the elevator to keep that tail flying until groundspeed is adequate to take off, but not taking off too soon!

I'll get to the point now. There are two points.

First, to keep the aircraft around for a long time, use the 3/16!QUOT! wire. It takes the hit on grass fields and you just bend it back if it gets too far out of whack. The 3/16!QUOT! wire can be bent back easily be holding the aircraft on the nose, retracting the gear and bending the gear back by grabbing the wheel and using it to bend the wire appropriately so that the gear retracts into the wing. This way the stress is not so pronounced on the retracts. The alternative is to bend the gear when the gear is down - I've done this, but I've found the best technique is to torque them the way you want while they are real close to the wing. The typical bent gear would be bent either fore or aft, not right to left! If this embarrasses you, well, do it when no-one is looking. I would rather bend the gear than have to straighten the wing if you know what I mean... If however, ground handling is what you want, then struts it is.

Second, and this is the cool one; change the throw on the elevator. Yep, You read correctly. I learned something on the Spitfire that worked wonders. I did a kind of 3D thing where I have the ability to put in lots and lots of UP. I did this with the spitfire and it was a different plane. I save this only for takeoffs. I have several different flight modes. The 1st is takeoff mode and the only difference between the takeoff mode and flight mode (2nd mode) is that the elevator throw is at the maximum I can physically get. Since you are re-doing part of your stab, you might consider beveling the stab - or increasing the bevel on the elevator to allow for increased throw. Why have I done this!? I can attest to the P-51 working very well with this. When I have full UP, that tail sure as heck stays DOWN on the deck like glue. I give it no choice, with the increased deflection, the prop wash definitely keeps it that tail down. The trick is to keep the tail down but not make the aircraft get into the air too early.

All of this makes you a better pilot, these .60 size airplanes are not easy to fly until they are in the air, then they are fine. Then you have to land. Keep flight mode on, the elevator throw is less important on landing, but increase the throw once you are down in order to taxi properly.

The Giant Scale Warbirds that I am building and have built all use struts - Robart and Sierra Giant. The Top-Flite P-47 Giant Scale is in build and Robarts will go into that. These aircraft have much, much greater surface area and a lot more strength going for them and struts wont' be a problem.

Epilogue: The P-47 was lost two years ago to engine failure after takeoff - it stalled and landed on very hard dirt at the end of the field. The Spitfire was sold. The P-51 is still going strong and is my last .60 size warbird. I moved to an area with a club with a much larger field and am progressing in a collection of much larger aircraft... The hunt goes on...

Rosster6028

My Feedback: (57)

Here are the pics of the aircraft I wrote about in the last post.

Man did they fly!

larry@coyotenet

My Feedback: (21)

Gentlemen, your problems with the TF-60 size P-47 are simple to understand when the plane weighs 13+ pounds! Having built and flown the same plane for five years with none of the problems you are having, but flying at a weight of 8 1/2 to 9 pounds I can tell you that those extra 4 pounds make quite a bit of difference in the performance of the plane. Mine and the same plane in the bubble canopy version that my flying buddy has both flew very well with ST-90's, actually somewhat overpowered, at 9 lbs and a field elevation of 5,000 feet. Both needed no weight in the nose to balance. On the other hand a 13+ lb TF-P40 and a 14 lb TF-P51 both flew as you described. If built per TF's plans they will come out under 10lbs even if fiberglassed and with cockpit kits and pilots. Having started building warbirds back in the early 70's when kits were nowhere as good as they are today and engines were about half as powerful you got used to making them as light as possible. Some wise man once told me "Build planes to fly, not to survive a crash." He was right, there is no substitue for light.

Larry

Rosster6028

My Feedback: (57)

Larry has a point. These 3 were my first three warbirds. I built them to crash. I simply did not know how much stress an airframe could take. That P-47 I lost? The wing was intact. I had my two eldest daughters (25 and 40 lbs each) jump up and down on and point load the wing when the tips were supported above the ground. The wing did not break. It didn't break no matter how hard they tried. Here's the thing though. I've only seen one TF bird like this come out as light as Larry reports. One.

It did fly well, however.

The bottom line:

If you are still building, build really light. If you have already built, then Larry's assertion about light weight is a moot point. The aircraft will fly, but she'll fly real scale, with the quirks and everything that goes along with it.

The only thing about light, however, is that you may now have an overpowered aircraft, which, in my opinion - in the wrong hands - can be worse than an overweight airframe.

SMUGator

Mine is my first near scale warbird and is heavier than I'd like at 13-ish. The reasons are well documented on other threads. I think I could fully detail it and hit 11 lbs or so on a full do-over. I don't see how you'd do it with the engine I prefer in the FS 120, w/full retracts and gear doors, detailed cockpit and pilot, and a good job on surface details and panel lines for much less than that. If it can be done, please coach this rookie up.

Tom