RE: Top Flite AT6 ARF
 

Sorry to hear about you AT-6..... The retract boxes will fit in all Top Flite warbirds of this size. They have the same plastic boxes. The P-51 and P-47 just don't bounce like the AT-6 but a hard landing will crack the boxes.

Good luck and Enjoy.

RE: Top Flite AT6 ARF
 

Hey Ton2di,
is the field you fly out of paved? Walt Good Field is in Germantown....you should hit it up sometime man

RE: Top Flite AT6 ARF
 

badazzgti03,

Hey. If you are not busy this Sat the 23rd come pass by our field at Laurel (Freestate Aeromodelers). We will be having an Airplane of the World event. Lots of people from all over the area. I will bring my AT-6, PT-17, 1/5 Corsair, and P-51.

Tom Treese, this is for you as well if you're around the area (I know you're almost 4 hrs away.)

Ton2di

RE: Top Flite AT6 ARF
 

I have been reading this thread through and am not in the least surprised by all the complaints regarding the gear. I myself am in the final stages of the fourth mod/redesign on my kit built, OS SF91 powered T/F AT-6/Harvard and in the last year have only had approx a dozen flights, including the maiden. This one was rescued from our flying club wall and over the course of a year I gutted the plane from it's display build, (only 1/3 of the glue joints were complete) and added the OS91 on a removable tray that includes the tank, mechanical retracts, split flaps, individual aileron servos, landing lights and corrected other build errors. During reskinning the wing I built a fixture to maintain a 2.5 degree washout and the plane required NO roll trim at all.

To be true, with the correct toe-in the plane will take off and fly beautifully. It's the landings that scare the hell out of me. There are a couple of reasons that are nasty on their own, but combined add up to very ornery landing characteristics and despite my over 27 years in this hobby have made me wary to the point one exacerbates the other.

First is what follows full scale where this plane has one of the wickedest stall behaviors out there. In a heartbeat it will go from flying relatively benign to having the wing vertical or greater with no warning. This is normally designed out in a model this popular and also a strange one as I have floated the plane down the runway, (due to the second problem covered shortly) and have been in perfect control. I have talked to several full size Harvard pilots and they have confirmed this behavior in the real craft. In fact, there remains one of a pair still on our field kept in my old hangar.

This came out to bite me on the maiden as I incorrectly set the gear track and due to the wander had to keep the tail down. The plane launched far earlier than expected for the weight and climbing nose high on the prop it reached approx 10' before snapping over to the left with the wings vertical. I though the plane was coming home in a bag, but I was able to level the wings with no problem. It then snapped to the right. As the plane had descended to 4' my expectations of disaster were growing. Again, I was able to recover and before it did it again, from about 2' I lowered the nose, cut the throttle and forced it down. The gear legs bent aft were the only victims and after straightening them out I worked on raising the tail for the next attempt. Much better and after trimming it flew beautifully at less than half throttle. I kept the speed up at landing and consequently the gear legs bent again.

As mentioned, the second problem becomes obvious to anyone after the first landing attempt. I can confirm the gear legs are abysmally soft, but the Robart wire still bends and transmits more energy into the wing structure. The second landing after replacing the T/F legs the R/H forward mount ripped out. It was this flex that broke the rear tab from the Robart plastic gear body.

The result of that wire bending has the wheels travel aft and down. Despite a "Greaser" approach, at the first loading placed on the gear legs the plane will launch airborne again like a pole-vaulter. This can happen at severely reduced airspeed where that stall may come out to bite, but almost guarantees the next touch down will be hard.

My second last mod was to swap out the so carefully installed and rigged Robart mechanicals for Eflight 60-120 servoless units. I had added individual gear mounts during the build and those were torn out to install self-contained gear mount setups identical to my T/T Rare Bear. During installation I sandwiched glass cloth to the top skin and spars and this is now extremely strong. I retained the bent wire Robart legs and the next flying session saw them bend at the slightest opportunity. Due to this I'm waiting for a set of struts to allow for gear compression and energy absorption directly in line with landing loads.

Unfortunately the Eflights do not have any mods specific to the AT-6 like Robart where the gear leg can be angled forward, nor to they sell blank trunnions. Therefore, over the last week I hogged out a pair of blank trunninons from T7075 on a Bridgeport. They will be drilled for the new struts once I have them in hand and know the angles.

I will be posting some pics soon if anyone is interested.

RE: Top Flite AT6 ARF
 

I know I am, been lurking and waiting for more![:-]

Carl

RE: Top Flite AT6 ARF
 

Here you are then. I have a build thread on another forum, so I will try and keep the list short.

First is a rough cut of the wing structure with the gear and flap installation. Those retracts did not last long as there was a weakness exacerbated when I drilled them for the larger diameter legs. I built split flaps and tied all three into one hidden servo actuation with some heli bits to transfer the center flap outboard. Since the wing gains dihedral outboard of the center section, getting the angles right took a bit of work and creating all those half ribs out of my structural ply was the most time consuming, (I sandwich glass bid layers between two thinner pieces of plywood and weigh them down between two sheets of 1/4" plexi until cured, the number of layers counted for the amount of strength required). I use that method frequently for firewalls and other high stress structures as it rarely exceeds the stock thickness or weight, but is damned near indestructible.

Pic #3 shows the center fixture I fabbed to hold the correct washout while the lower skin was applied. What you cannot see is that there is C/F tape run in a channel in the lower spar nearly out to the tips. That wing is a lot stronger than stock now.

Pick #4 shows the engine mounting. That removable section was built with the ply layers as described and includes the tank behind the firewall so everything can be integral during installation and removal. No fuel lines to disturb. The standoff behind the engine mount is to properly space the prop to the cowl.

#5 shows the nearly completed wing and early retract install. One aileron and servo have been installed at this stage.

#6 is of the completed fuse. The hatch ahead of the cockpit hides the switch and remote glow adapter.

#7 covers the early landing light install. I have since gone to a larger single LED and reflector which is brighter and more to scale. The original lights came on when the gear was down, but to cut any power consumption they activate now if the flaps are extended.

#8 shows the radial engine with the cutout for cooling the 91. #9 is also of the same rig, but includes the roughed out air dams to keep the air directed over the head. This is my standard for cowled engines and is extremely effective.

#9 and #10 are of the self-contained gear mount. I fabbed those previously for Rare Bear, so this was a familiar process. Once I had both fit correctly they were bonded to the wing as described with layers of glass bid to create a far stronger structure. As you could see in the original the front mount pad was anchored to the open ended wing structure at the joiner ribs between the inner and outer panels and was not very rigid.

#11 is of the newly fabbed gear trunnions. One is installed at this point. They are longer than stock as the ends will be shaved at the correct angle to create a solid butt against the strut legs.

#12 shows my rather opinionated instructor and the sweaty student. Even if not immediately recognizable, you can figure out which is which by their names.

And here she is before the maiden. Yours truly wasn't smiling as much later in the afternoon.

If you need any more detail I have more pics and will hopefully have those of the final gear mod soon.

What is apparent in the flap setup are the C/F tubes used to strengthen each panel. There is no possibility of twist now. I also installed C/F rods in the ailerons, rudder and elevators for the same effect.

p.s. I have tried twice now to match the covering to paint the cowl and center wing bay cover with no luck. I'm also stuck trying to figure out some covers for the wing joints. Apparently those are not sold separately for the ARF's. If anyone has a spare set I'd be grateful.

RE: Top Flite AT6 ARF
 

Sir,

you did an excellent job on that airframe!

[8D]

RE: Top Flite AT6 ARF
 

Thanks. All that effort would feel worthwhile if I could just get it to land right. Almost all my planes are taildraggers, so I have lots of practice, yet this one makes me feel like a beginner.

RE: Top Flite AT6 ARF
 

I have 135 flights and 150 landings with my AT6 with the original retracts plus my reinforcement boxes without any problems.
I land with 40* flaps and about 1/4 throttle and just ease it onto the runway. Keep the power up till it's about one foot off the runway then ease off the power as you add up elevator and it smooths right in.
If you have a good head wind you'll need less flaps.

I hope this helps...

RE: Top Flite AT6 ARF
 

As I said, I have lots of experience with taildraggers and that includes Rare Bear, one close to the same size with retracts and NO FLAPS. It is also considerably heavier. This has a more conventional strut arrangement mounted to an identical set of Eflight 60-120's and although approaches are much faster, is a lot easier to land. If I have any complaint it would be the fact those rather tall legs mean it wants to do a goat at the slightest opportunity. I modded the pads to have the wheels slightly forward when extended, but have yet to try it out.

I suspect part of the problem here is our grass field. There would be more drag than paved surfaces and that is what forces the legs to follow their natural geometry to bend aft and down when a load is applied on the wheels. I solved the gear mount problem earlier. Now the issue is with those legs. Unfortunately I believe that travel also adds to the rearward stress on the wires simply by the fact they are forced downward during flex and that extra, before the plane has a chance to react inertially is why even the smoothest landing is likely to bend them. By opting for struts I believe the suspension will more readily absorb energy without the oddball wheel movement. I'm also hoping a strut will remain where it's supposed to regardless of abuse so the wheels retract correctly.

p.s. Tom, I was wondering if your setup also includes the center flap. Mine has two extended settings, mid flap being approx 20 degrees with full close to 45. Note, my weight is close to 11 lbs. Although the plane seems more than comfortable taking off and continuing the flight at no more than half throttle, that makes a big difference in landing.

RE: Top Flite AT6 ARF
 

The Top Flite Flite AT6 has three section flaps.
I also fly on a grass runway which I mow like a golf fairway.
Yor are correct, the biggest problem is the foreward strut wires. This will promote a bounce regardless of how strong the wire is. But it keeps the plane from nosing over on every landing.
Not a great design but I have managed to land it so as to minumize the bounce and bending of the wire.

RE: Top Flite AT6 ARF
 

Ours is definitely NOT cut that close. In fact part of every post flight is cleaning the grass stains from the props.

RE: Top Flite AT6 ARF
 

Hello guys,

I just purchased the TF AT-6 ARF and in the process of building the wing. I've been reviewing all the info I can so far here and RCG's on the build but am curious if I missed something on the wing attatchnment. I'm still learning and don't understand why there's nothing more than the relatively short, loose "Wing Joiners" securing the L&R wings to the Center Section. Shouldn't there be some pins or tubes or something acting to help prevent them from twisting? I seems illogical to depend on just those short Joiners and maybe the wire connecting the flaps to secure them.

What am I not clear on?

Thanks for the help...

Dick

RE: Top Flite AT6 ARF
 

It's been a long time since I assembled this plane, and this may seem to be a simple answer, but I used epoxie to glue the outboard wing sections to the center section. I also didn't want to use a servo matching device on the flaps, so I cut the center flap in two right in the center so each half is operated by it own servo.

CCF Flyer<br type="_moz" />

RE: Top Flite AT6 ARF
 

Hello Dick;
Yes you only have the two wings joiners to mate the wings to the center section. Use plenty of 30 min epoxy on both side of the center section, wings, and wing joiners. Tape the wings to the center section and let them dry over night. Also read back in this thread and you will see a lot of talk about the landing gear on this bird. They like to leave the plane even on a smooth landing. There is a guy who make landing gear box for this plane and they are a big help. I have a set on my AT-6 with over 200 landing and the gear is still holding up.
His name is TomTreese. Send him a PM to see if he still make the gear box for this bird. She is a great flyer and you will love her!! Please post pictures and let us know how your maiden goes!!
Sonny
aka
jet22b

RE: Top Flite AT6 ARF
 

I still make the retract reinforcement boxes. They ar still $36.00 a set shipped. I have over 150 landings on a grass runway without and issues.

RE: Top Flite AT6 ARF
 

I grabbed mine from our flying club wall: I had been staring up at it for MANY years and finally just had to get it airborne. Took nearly a complete gut over 10 months as it had only been assembled for display and roughly 30 of the joints were glued.

The multi-layer wing joiners within the spars were not on straight, but relatively well bonded to prevent easy removal for correction. I built up within and around each to get a continuous tie between the center section and outboard panels, but there was one critical missing area at the leading edge just outboard the retract bays. This came back to bite me within a couple of landings.

One thing I did extra was to route out the outside of the lower spar(s) and run a length of C/F rope from wingtip to wingtip. This was before the lower skins were applied, so it becomes invisible later. Once the epoxy cured you can practically jump atop the wing and everything else will fail before that spar lets go.

Obviously with the ARF this is not a reasonable action, so in your case all I can say would be to follow the instructions and understand the joiner is there to transfer lift loads only during flight and if the panels are aligned during joining they should remain that way once cured. You can add a dowel to the aft of each facing rib, but it will only help alignment and will become redundant once the ribs are bonded together.

When I make structural bonds like this I always mix in what is called FLOX, (flocked cotton). It is a short fiber we use in the homebuild aircraft trade to add strength to epoxy or poly mix. This adds bulk, prevents sagging and is relatively easy to sand to shape. If used you can control the consistency of the epoxy by how much is mixed in. The key is to wet each bond area with pure epoxy before adding the mix to ensure a good penetration of the wood.

NOTE 1: Only structural epoxies set up internal long molecule chains when curing. Laminating or "Finishing" resin does not and is used primarily to fill the weave when covering. The long-chain molecules are fine, but can be aided with the addition of other fibers.

NOTE 2: Microballoons are a filler material only and do not contribute to structural strength in the least, In fact it will weaken an epoxy bond by reducing the internal area for linkage for the same volume. It is to create filets, but in that case I still use FLOX as it is almost as easy to form and sand.

FLOX can be found at any structural bonding supplier such as Aircraft Spruce or West Systems. There is similar product called Aerosil.

RE: Top Flite AT6 ARF
 

Wow quick relies form you pilots...thanks very much.

I think my concern on the joining the wing was in relation to just allignment more than anything. Since most of you have not made comment with any structural concerns on that issue, I'm certtain it will be fine as long as I pay attention and take my time.

The landing gear issue is another story. After reading all the comments I was not looking that forward to installing them at all. Now, get this....I opened the package containing the gear a while ago this morning. My first impression was a bit of a shock after looking at how cheap the plastic was. I'm no expert or engineer but it struck me as no wonder it consitantly failed. OK, here's the good part - after studying it further I discoverd several stress cracks in both L&R gear where the halves had been screwed together.

I called tech support and talked to "Mike" and he said they never had problems with the gear either on this plane or the P-40, which must use the same plastic.
Anyway he said he'd replace the gear and I just finished forwarding some good photos to him.

What a shame to have to deal with something like this on such a great looking and otherwise well built airplane. Especially on a "Gold Eddition" from a premium maker.

I tried to find replacement gear in my spares box but nothing work so far. It looks like Tom T's modification may be the alternative.

Thanks for you help and promt replies, all....I'll let you know how the rest of build goes and what questions I may have along the way.

Best,

Dick

RE: Top Flite AT6 ARF
 

Just have to respond to Mike saying they have never had problems with these retracts. WOW! TOP FLITE IS IN A SERIOUS CASE OF DENIAL!

RE: Top Flite AT6 ARF
 

I agree!!!!!!!! Interestingly they replaced a set for me after the 5th landing (before I made the boxes) and at least 4 other owners early on this thread.

I have sold well over 40 of the boxes. The aluminum boxes take all the stress off of the plastic parts and they would work even if the plastic were cracked. Although, I don't recommend that.

I have also had owners of the P-40 and P-51 (same plastic gear) install these boxes.

My Hanger 9 Hellcat has a similar box but it's all metal. Never an issue in 400 landings.

RE: Top Flite AT6 ARF
 

When I mentioned all the reported failures, Mike indicated he wasn't aware of any problems. I was tempted to take exception but he seemed sincere and I didn't did not care to carry it further. I think I'll wait till I get the replacments and see what they look like. If they're undamaged then I may try to make some metal reinforcement or contact Tom and see if he can make up his mod.

Question: I installed Futaba S3004 servos in the ailerons and not getting enough throw with stock servo arms. The furthest ouside hole on the arm is being used but it's not enough to gain full throw on high rate in one direction. I assume the S9001 arms aren't any longer but not sure. If anyone else had this problem did you use a longer arm?

Dick

RE: Top Flite AT6 ARF
 

It only takes 3/4" to 1"" of throw for this a warbird. About 1 1/2" on the rudder. It doesn't take a lot of torque. I used HiTec H-475's on everything but the throttle. But I only use HiTec servos. Usually digital.

RE: Top Flite AT6 ARF
 

Dick;
I agree with Tom on the control throws on this bird!! I am using the Futaba S3004 servos and they are working very sweet!! I would say this bird fly must like the full scale model. Nice slow roll and large sweet loops!! You will love this plane and find you will take it more to your flying field than any other plane you have in your fleet!! You have any more question, please feel free to post. By the way, what engine are you using??
Sonny
aka
jet22b

RE: Top Flite AT6 ARF
 

Dick
Glad to see you're on RCU. I do have the retract boxes(New) for this plane. Shoot me a PM if interested $20 shipped

Paul

RE: Top Flite AT6 ARF
 

The aileron throws are close in one direction but I can't get more than about 5/8" in the other before either the servo arm or the tip of the control rod 90* bend strilkes the side of the servo cover slot. If the servos had slightly longer arms there'd be enough clearance.
I prefer the grace of scale flying offers so no abrupt or radical moves are on the schedule and I'm sure the recommended throws are fine...I just would prefer to have the option of using them and more than I'm getting now. Has anyone else had this problem come up? I don't really want to widen or lengthen the slots if all that's needed is longer servo arms.

I was also concerned about the wing connector blocks being a little sloppy but I think that may be intentional to help allow more epoxy or whatever adhesive is to be used not to be squeezed out thereby adding more strength.

This will be an Electric conversion with planned power supplied by a Bigfoot 60 on a 5S battery at this point.....

Thanks all ~

Dick