hey guys i heard someone got thier rare bear replaced for stabliser failure. i don,t no if it is true or not.a friend of mine said he saw it on this site. thank

Does anybody else have a gap between the wing and fuse? My right wing fits up against the fuse great but the left wing has a 1/8 in or so gap from the wing tube back. I've tried sanding down the front of the wing where it fits against the fuse but its going to take alot to get the whole wing flush. I guess I could sand the fuse and wing until flush but I prefer to just have the wing fit like the other out of the box.
\Maybe Ace will send me a different wing??

Both my wings have gaps (3mm) went fitted...........
Cheers
Ken

Seems like the RB is an awfull lot of work for an arf!
Tearing covering off.
Fixing landing gear mounts
Balance issues with suggested engine sizes by manufacture.
Etc., etc.
I love the looks of it but man...I think the manufacture should have done a little more R&D before introduction to the public!

Just a thought,
Jim

No not really..............
"not for beginners" is mentioned somewhere in the instructions.
All in all a pretty good model if you have an eye for detail and some engineering prowess.
That spinner alone must be worth near a 100 bucks, down here anyway.....
Cheers
Ken

...had something simular but on carefull examination , turned out to be the dowels slightly tight in the fuze holes...i altered the holes slightly and ...bingo..!

Well, just flew my xmas present for the first time today. The RB is TOTALLY AWESOME!!!!! It flew like a dream. Slowed down real nice and greesed the landings, and we had about a 13 mph wind today too. Didn't bother the RB at all.

I put an OS 160 in mine. Sweet. It really clocked along. One of our members has a radar gun but the battery was not charged. He said it looks like 120mph plus from his experience.

AND, my tail didn't blow apart and my gear didn't break out, thanks to some reinforcing based on info in this thread.

It finished at 11 lbs 4 oz, heavier than some have posted but didn't seem to effect the flying.

I have some good video. Stay tuned and I will post a link to it as soon as I process it in the next day or so.

Will also post some building tips since it is all fresh from just finishing construction.

Oh, by the way, if you are reading this thread and thinking about buying a RB, you may want to consider your runway surface. I started the plane for the first time today, with a large crowd gathered to see it fly, and the minute I goosed her a bit to start taxiing, she immediately nosed over in the grass. And this is with the 3 1/2 inch over-sized wheels. I absolutely can not taxi on the grass without nosing over. I thought my corsair was touchy on the grass, but this is a whole new game!

Luckily we have a paved runway and taxi ramp so it's not that big a deal as long as I keep her on the tarmac. We have real thick grass here in Fl and these Dave Brow Lite Wheels are soft foam which may not help. My CG is even 1 inch aft if the recommendation.......

Here's a pic from today and you can get a feel for our turf. Haven't really totally finished the plane yet but just couldn't wait to fly it today.

No one else has mentioned this problem in the thread. Any thoughts from those of you that have RB's? Is your RB touchy when taxiiing on the grass?

Ken I totally agree with you.thank you very much.have a great day.

Ken I totally agree with you. have a great day

Just started my kit tonight-

Thanks for all the info about the stab. It looks like I've got one of the later ones since the first 2 ribs are ply. The carbon tubes were a tight fit and required a bit of sanding and polishing to go all the way in without too much effort. The rearward (long) tube was about 5/16" too long and had to be trimmed. I'll probably put some ply inside the fuse at the stab mount, too, just to be safe.

My question today is about the down and right thrust: specifically, how much have you guys been reducing it? How does it fly after reducing the thrust? I will be using a YS 1.40 for power. I haven't installed the crutch or engine mount box yet and I'd like to reduce the angles of the plates rather than shim with washers after installation.

Any info will be appreciated-

Thanks!

Tony

T-pacini. I used two washers up and one washer to the left. I have an OS 160. I only flew it three times yesterday so still getting used to it but it did seem to want to climb when I poured the power to it. The down thrust may be required, not sure yet. The right thrust seemed good. With low or no power the plane tracked straight and when I throttle up, it continued to track straight.

Couple of suggestions. Glue your ply tabs in for the cowling installation FIRST. The manual has you doing it last. Also, do not assemble the battery box on top of the firewall until the very end when everything else is done. Once you install this you limit your access the the engine and inside the plane.

Well got some bad news. Went to the field today and flew the RB for the third time. During a high speed pass we heard some noise and then the plane began to handle a little weird. I brought it in right away to check everything over. I came in a little hot and one of my tires caught an edge and spun on the Axel. The RB went nose down and finished its landing skidding nose down on the prop.

The Good News
I was sure I ripped the gear out but low and behold, my mount mods worked and the gear held up (spring air 103's). Pretty impressive because I came in pretty hard. I will explain how I did this in subsequent post.
The plane and spinner were unscratched thanks to the 3 bladed prop which kept the nose up as it slid down the runway on 2 blades.

The Bad News
Looking at the plane back at the bench it appeared that the horizontal stab was separating from the fuselage at the glue joint. Initially I wondered how the 30 minute epoxy could have failed. I was very careful to sand and prep the surfaces and ensured that the glue was well applied. On closer inspection back at the hanger I saw that the stab was actually separating. I cut the last section of balsa that was holding on the stab and realized that the first rib was still glued to the plane, but was torn loose from the rest of the stab.

Also, when looking inside the stab, you can see that the second rib had split.

No builder error here. I was very careful when building to assure that the CF tubes were the right length and never forced one into the stab to break a rib. Everthing was prepped and glued properly.

Thankfully I got the plane on the ground in one piece. Not sure what the solution is. I called ACE and they are doing inventory so I had to leave a message. I am assuming they will send me new tail parts, but even so, without some changes it will happen again. I think I will have to open up the stabs and reinforce, re-skin and recover to assure it will handle the larger engine (OS 160)

Some thoughts:

* One might say that the 160 is to big for the plane. Well, this is an 11 pound airplane which certainly warrants. Ace uses their 120 which is a little heavier and .2 hp less than the 160. The 160 is 36 grams and the OS 91 is 19 grams. If I use the 91, I would have to add 1 1/2 pounds of weight to the nose to balance. (plane came a touch tail heavy with the 160 and 5 cell pack in the nose. I did add a little wieght to the tail from re-inforcing, but not that much! This plane is tail heavy)

* On a previous call with ACE, they suggested that the rear fuselodge be re-inforced to avoid flutter if using a larger size engine. I laid a 3!QUOT! strips of fiberglass inside the fuselodge paralel to the stab to re-inforce. The stab mounting surface is solid.

JWortner,

That's an interesting failure mode and after inspecting my horizontal stabs it's probable cause is inadequete glue application during the production of the kit. The crack you see in the rear of the first inner rib was most likely caused by the factory slotting of the trailing edge. The factory has installed additional material in the area of the trailing edge that supports the elevator torque rods. When they slot the trailing edge, they also slot through the rib. If the tube is slightly oversized or tight in the hole, it's easy to understand how the slot can enlarge into a crack.

I opened my stabs to install additional material for the Robart Hinge Points I plan on using. After I determined where I wanted each HP, I drilled a pilot hole in the trailing edge and then marked an area on the underside of the stab to cut away the skin immediately adjacent the trailing edge. IMO, I wouldn't use the CA hinges that come with the kit, there really isn't enough material in the trailing edge or leading edges of the control surfaces for these types of hinges. My guess says the trailing edge stock is no more than 3/16" thick. I digress, after cutting open the skin on the underside I checked the integrity of the glue joints inside the horizontal stab, two of the ribs had NO GLUE bonding the skin to the ribs. After discovering this omission by the manufacturer I decided that I should cut a couple of other pieces out of the lower skin to inspect the ribs which carry the CF tubes. None of the ribs had been cracked by my trailing fitting of the CF tubes and everything looks good. I have since reglued the skins to the stabs by dribbling liberal amounts of CA into the stabs at the rib/skin interfaces and then letting the CA seek the cracks via capallary action. No more loose stab skins now.

I plan on installing the horizontal stabs with the covering off the bottom sides and the holes that allow access to the CF tubes still open. I'll mix some 2 hr epoxy with BVM Mill Fiber and glue the tubes to each rib. Then I will close the bottom of the stabs and recover them. I'm also gap sealing the control surfaces and pitching all the hardware that came with the kit and replacing it all with high quality parts. Something I've noticed over the years with the hardware that comes with kits, most of it is adequete if you build exactly to plan. The problem with the kit hardware is the sloppy fit of the clevises and the control horns and the generally below average quality of the supplied hardware. In manufacturing there's a term called stacking, basically it's the addition of the small variations that occur during manufacture. I apply this concept when I setup my control systems. Think of the minute slop in the control horn/clevis interface, add the small amount of creep in the threads of the control rod and the clevis. Add the additional slop introduced by the z-bend or clevis at the servo arm and of course we must also include gear lash in the servo itself. What you now have is a control system that MIGHT allow flutter of the control surface. Add to this, any gap between the stab/wing/vert fin and the respective control surfaces during installation, mix in high speed and presto control surafce flutter.

IMO, Aces recommendation to beef up the interior of the rear fuselage near the stab tube pass through is a red herring. IMO, the fuselage is more than sturdy enough, the problem lies with the quality of the supplied hardware and the variability in the TT manufacturing processes. Stir in the "Need for Speed" with the added differences in assembly techniques and you have the potential for problems.

Thanks for supplying the updates with pics and your experiences to date.

Rich

P.S. I'm a slow asembler/builder but I'm meticulous. If I don't veg out this week after work I should be test flying my RB this upcoming weekend.

About Taxiing in grass, you must do as is done in full scale aviation, full up elevator at all times. This helps keep the tail down but won't always counteract the resistance of the grass.

FWIW: The grass at your field doesn't really look well suited for use during takeoff/landing or even taxiing for that matter. It's just appears too long/lush/thick.

Rich

Rich,

Is there a particular brand of control horn and clevis that you feel helps eliminate this play?

Yes, I have a high rate elevator set just for taxiing, and always use full up elevator when taxiiing out of habit. Does not help with this bird.

After writing my oringinal post I re-examined the stab. I can to the same conclusion, TT cut the rib when they made the slot for the elevator hinges.

Thanks for taking the time to reply.

Which engine are you using again?

I don't have a particular brand but I tend to prefer the Robart Control Horns with the metal balls. If I'm using a standard control horn it will almost always be one made of carbon fiber filled plastic vs the typical all plastic types. I'm also partial to producing my own horns using G10 fiberglass sheet. Like Vulcan (Kerry Sterner) I have quite a bit of Ducted Fan experience and flutter was/is always an issue and where I gained most of my experience in control systems. I actually found your statement about the battery box making engine access difficult kind of humerous. I built a YA A-4 years ago, IIRC, the fuselage hatch opening was about 6" x 10" total. Everything inside that fuselage had to be snaked through that opening and installed.

Anyway here's an example of what I plan on using for the Aileron linkage. Large 1-1/4" Robart Control Horn. I'll cut the mounting flange off and then drill about 5, 1/16" holes in a pattern sort of like this:


| o o |
| o o o |

Near the end that I cut the flange off.

These holes allow glue to flow through and add strength to the joint. I'll then cement the modified horn into a piece of hard balsa that has been slotted to accept the thickness of the horn. At the location of the horn on the aileron, I cut away the skin and then cement the modifed horn into place. In some instances, if needed, I've also slotted the leading edge of the aileron where the horn mounts, it really depends on where I want the ball of the horn to be in relation to the hinge line. Once I get the horn into position, I reglue the skin and refinish the under side of the aileron. The control rod will be 4-40 based with the Robart Clevis and a jam nut, the other end will probably be a typical Sullivan or Dubro Clevis with a jam nut. I only use high end CF filled or metal servo arms. I'm also partial to using ball ends, especially if the control surfaces or servo installation doesn't allow perfect alignment.

I don't know if you've ever read Jet International or other UK based R/C Modelling mags. In these you will often see all sorts of interesting homebrew methods used on very large scale Turbine powered models. Look closely at the some of the pics in various issues and you'll see where I got my inspiration.

Rich

Hi all,
I'm still building mine and its yet to fly.
I thought I'd share my experience and method I used with the stab assembly. Firstly I ensured the both CF rods fitted neatly inside one stab then epoxied the rods into that stab placing the stab in the vertical position until the expoxy was set (around 12 hours later), this ensured the expoxy settled and set around the end of the CF rod and the ribs.
I then dry fitted the stab (the one with the CF rods set in place) to the fuse the dry fitted the other stab to determine the correct length of the CF rods for a neat fit ensuring the end of rods fitted into their appropriate ribs. When I was sure the length was right I dry fitted a few more times ensuring I could feel the end of CF rods slid into their respective ribs. I then expoxied the stab assembly together into the fuse, with the stab in the vertical position to ensure epoxy ran down to settle and set in all the ribs.
During this final part of the stab assembly I expoxied the root ribs to the fuse and ensured epoxy was neatly placed around the middle rib, holding it all together with masking tape.

Just waiting now for my ST G2300 and springair 703's to arrive so I can finish her off.
Cheers
Ken

Ken,
When is your target date for flying? After what I found, and what Rbeav533 found when he opened his stab up, I would be very concerned about trusting the integrety of the stab. Us much as I hate to, I am definatly cutting into my replacement stab and beefing it up.

The other thing I noticed and will do to eliminate play when I rebuild is to fab a bushing of sorts to brace the elevator control rod where it comes throught the fuselodge and then does a 90 degree down to the control horn. If you use the stock hardware for this it is a rod with 4 hinges, 2 for each surface. The rod enters the back of the plane through a rather large hole. I can see a little play in mine where is comes through this hole. I am going to make a little notch in a piece of material, sort of like a U shape in which the inside of the U is the diameter of the rod, and glue that inside the fuse to help eliminate that play.

Hopefully by the end of the month. I know the G2300 is on its way and should be here any day now, but the Springairs I have no idea. A friend of mine ordered a set of 301's for his L39 a few months ago, was speaking to him just before xmas, he mentioned he was still waiting for them.

I'm yet to be convinced the stab needs any reinforcing, time will tell I guess. I think attention to detail with the stab, ensuring correct length rods and making sure epoxy gets to all the right places, it appears to be very solid, I know mine is.
Being an old speed freak I know the importance of correctly hinged surfaces with no play, so I also changed the elevator control linkage. I can post some pics if anyone would like to see them.

Also I think someone mentioned earlier about the increased load on the tailplane due to the built in down thrust, I think there are good points also.
Cheers
Ken

Ken,

I'd be interested in hearing/seeing your elevator control system changes. I still haven't decided if I'm going to stay with the stock single servo location and long rod to the elevator horns or converting to dual mini servos mounted in the rear of the fuselage. I do like the idea of having dual servos on the elevator for redunancy, but the propensity of the RB to be a bit on the tail heavy side is working against this mod. Maybe I should measure the actual weights of the components and calculate the impact on the CG. Or I can take the easy way out, like the Nike ad says - "Just Do It " and add nose ballast if needed.

Rich

JWORTNER,

After reading your stab-failure post I had a close look at mine: the root rib popped out easily (not much glue) so I pulled the sheeting off one side to have a look.

The first 2 ribs are ply and the rest are balsa. 3rd rib has a ply doubler at the rear with a hole for the rear carbon tube. There's daylight between a few of the ribs and the sheeting, too. I'm not taking a chance with this one and will just go ahead and make a new one (probably sheeted foam). Or I could "finish" the half that's still good, do it up as a plug, make a mold, then go the composite route. I'll just have to hang a bit more "meat" in the nose to make up for the beefier stab!

Thanks for all your posts..........I'm convinced that you saved my airplane!

T-pacini,

I wouldn't go to all the trouble to produce a new stab. Since you have the lower sheeting off the stabs, just reglue the upper skins as needed, reskin the lower side and recover with CG Ultracote.

Rich

Hey Guys!

I've been reading the thread every day while I'm waiting on my retracts from Sierra. Hoping Darrel ships them soon! I think he has them finished.
Now for my dilemma...I posted earlier that I ran 30 min epoxy down into the stab liberally prior to inserting the corrected length CF tube. I then epoxied the stab to the fuse and filled in the joining edges as well. NOW...I'm worried that the stab itself is not properly glued together.
What is your suggestions to get glue in there. Should I cut away skin while attached to the plane? Or drill a couple of holes and liberally force Thin, Medium or Heavy CA into the suspect areas? Then plug the holes with epoxy and re-cover.
Thanks for the help!!

Dudley

Greetings again!

I know I seem to be needy, but I really want to finish this bird right. I currently have the elevator and rudder attached with the stock hinges. They are tight, with no gaps, but I'm still concerned after reading the recent posts. Should I cut these and re-install more quality insertable hinges?

Also, what do you guys think about the long balsa rod with wire attachments to operate the elevator? I'm using a Hitech Digital ultra high torque servo with metal horn.
I'm running an OS 160 as well.
Thanks for your input.

Dudley