The RB clearly has many problem areas. Some are easy to fix, and others require a great deal of work. The horiz stab is definately the biggest problem area. I had to completely re-engineer my stab with longer carbon fiber rods(almost twice as long), removed the most inboard rib on both stabs and replaced it with one that was more than 1 inch wide(1/4 ply and 3/4 balsa) and then drilled two holes in them for the carbon fiber rods to pass through. The end result is that these 1 inch wide ribs are aeropoxy'd to the side of the fuse withe the rods going through them and then I aeropoxied the stabs onto that. It gives the stab something to hold onto instead of just a 3/32 rib. I also used carbon fiber pushrods for both elev and rudder to help eliminate any chance of flutter. J wortner also did a very thorough re-engineer of the horiz stab with great success. My point is that if all you did was go into the stab and add more glue(according to your previous post), I am surprised that it lasted for 3 flights.

opened up my stab on my RB and it seems that it was waste off time since the factory gluing was perfect.
Next week I will give my RB wind under its wings. I keep you posted.

Good Luck Rudi,
Again, I would suggest that you do more to the stab than just ensuring the factory glue joints are glued properly. It also needs to be "beefed" up signifigantly.
Last week I was at the field and my buddy and I got into some impromptu racing, my RB against his Lil Toni. We were both between 110 and 114 during straight and level radar passes. Then my buddy starts diving and rips off a 120 and then a 130 mph pass! Well not to be outdone I fire up the RB, takeoff and start with my diving passes, I clicked off a 116, then a 121 and my final attempt from about 500 feet straight down with mr. OS 160 wide open, I would guess at approx 125 mph, resulted in elev flutter followed by some pretty fantastic up and down oscillations. I immed pulled the power back, dropped the gear and limped my way back to the runway. I had to hold almost full backstick and full up trim to maintain level flight. I actually made a greaser on the landing. Post flight inspection revealed no damage to the plane except my elev pushrod looked like a pretzel and my JR 4131 servo was stripped.
The lesson
1. Dont dive your RB from 500 feet wide open.
2. Dont make pushrods using threaded rod. The rod is very weak, use piano wire instead with silver soldered threaded rod ends. I also replaced the 4131 with a metal geared JR 8411.

Anyway I am just returning from the field with four more flights on the RB. Still flies great......just keep the speed below 120mph and you will be fine.

Since I haven't even opened the shipping box on mine let me ask you a question. Would a set of carbon rods/titanium ends fit in the rear of the RB?



That way you aren't using a piece of wire or threaded rod. Do you have to use a piece of wire because of room considerations?

Just wondering,

Thanks
Don

One picture is the original pushrod that you can see bent at both ends. Other 2 pics are of new pushrod with piano wire and soldered threaded couplers.

A couple of more shots of the pushrod and general installation...

Hattend,
There is definately enough room for the carbon fiber rods. Although you need to have a rod with two ends for the elev. B&b Specialties sells aeroshafts with titanium ends and they also sell a titanium end that is designed for twin hook-ups. Make sure you get one that is 4-40. It is probably alot better than my set-up but Im cheap.

Thanks...That's what I needed to know.

I'll take a look at B&B

I'm not a big spender either but 15 bucks here and there on a $1000 plane seems like a good investment.

Don

Well I have to keep the plane cuz the box got messed up on the way to the shipping place so i cant sell it now so...now i gotta keep it. And I went ahead and started on the stab work, adding blocks for Rorbart 308 hinges....and im also renforcing both sides (left/right) of the stabs where the carbon tub goes in...will have some pics tonight when im done hopefully.


as for push rods im going to use 4-40 rods...because im not going to mess with wood or carbon rods. this way I know there wont be any flex in the rods....just my Opinion.

WarbirdairRacer,
I would suggest that you use carbon fiber pushrods with short lengths of 4-40(3/32) piano wire at each end. On my previous pushrod that flexed and bent, the arrowshaft did not flex or bend, only the 4-40 threaded rod at each end of the shaft did. If you make your whole pushrod out of this material it will flex. If you try to run the 4-40 wire through a pushrod tube you will have to install many support braces which will be difficult to do with the fuse already complete. The arrowshafts can be purchased at your local archery shop. I paid 20 bucks and got three of them and glued dowels into each end. You could also take Hattend's advice and buy some pushrods through B&B or central hobbies. Trust me, arrowshafts are the strongest and by far the easiest to install. Also if you want to fix the tail properly you need to lengthen the arrowshafts anyway.......so you might as well buy your pushrods since you will be at the archery shop anyways.

Thanks for the tip. however I have had great luck with the 4-40 pushrods like I want to install. and there is alot of room that I can install the bracing needed for them in the fuse.....I do have a couple questions tho....on the inner frame work in the fuse there is 2 holes 1 per side of frame work....that looks like the wing tube should go into...and it is all the way up where the wheel wells are. is this right? or did i F something up here? I am also thinking about adding brace for the wing tube on each side of the fuse where the tub slides into the fuse...has anyone thought of this or is this to much?

also on each wing where the tube goes in the wing is it needed to do anymore frame work inside the wing ? other then frame up where the gear is? And since I am using a YS 140 I am also thinking about making the wings non plug in's.....one con I see to this is where the wing tube goes in the fuse it is right over the servos....guess I could move the Elv. and rudder servos more back of the fuse out of the way of the wing tube. and stick the air tank and recv. way up in the front as far forward as I can get em.....BTW I am adding a second Elv. servo to it.

Has anyone with a YS 1.40 had tail problems with still to much weight in the tail?

Hi! First, thanks to all of you so I appreciate very much you really good contributions to this lovelly hobby. I have bought a Rare Bear, here at Spain (I am from Madrid, Spain) and I am in proces of construction. First, I have started checking the horizonatl stabs and opening up the balsa to put the mods inside. I will continue in next steps with the reinforcing of the plywoog landing gears and wing ribs. I would appreciate very much if you can advice me about flying skill required, so I am a little worried as far as I have been flyinbg untill now only sport aircrafts and also type F3A, similar to CAmodel's Epsilon, Eclipe and/or Chip Hyde Vission, but never pylon racing models. How slow do you think is possible to keep the Bear without droping the wing, and what do you consider is a model similar to it in terms of flying characteristics? Is it previsible enough or it drops the wing easily?

Thanks agains and best regards,

Mike

Mike,
If you are flying off grass hold full back stick as the RB begins its takeoff roll and ease off of it as you begin to see the airplane "get light" to prevent any noseovers.
As far as flying goes, its pretty straightforward. My RB is one of the heavier ones at 13 3/4 pounds. I was a little concerned at first, so on my first approach I came in way too fast and it ran the full length of the runway, Second time around I got it slowed up and it landed just fine. Its an honest flying airplane with no bad tendancies that I can tell. However it is still a heavily wing loaded warbird with no flaps and and if you balloon on the flare and lose all your airspeed you better be adding power or do a go around because it will bite ya if you dont. It does not fly like a pylon racer, it flys like a 115 mph warbird. Definately not for beginners but not anything an intermediate to advanced flyer couldnt handle. I have about 20 flights on mine now and am really enjoying it.

Ad Clark,
Thanks very much for yor clarifications. You mention "honest flying airplane with no bad tendencies", which for me means that Rare Bear is VERY PREDICTABLE and SMOOTH flier. You know, it is no the kind of plane that during flight, it gives you movements like stalls that you did not expected at all, per instance, when performing a loop meanwhile keeping airspeed over its minimum, and the plane "talks the pilot" and "notices: "eh, guy, you are slowing me to my stall speed". You know, I had a very bad experience with a plane thha, maybe due to a short tail moment and heavy tail setup (really a bad designed plane, nothing to do with pilot skill), was NOT predictable at all, and dropping winds without warning was its favoutite tendency.

Regards, and I will keep you updated about my next steps!!!!

From Spain, Mike

Hi again,
related to retracts, I was thinking about starting with the Tiger mechanical retracts, so I would like to keep weight to its minimum. After, maybe I can proceed installing some neumatics. Related to Tier ones (3008), however, I do not like so much so I expect that wires could bend easily. For all you having flawn the Bear several times, what is your opinion?

Regards,

Mike

Miguel,

I have Spring Air #116 which are 85 degree retracts with 3/16" wires. These are exteremy light weight retracts and have worked well for my RB. The only change from using the retracts as they came out of the box was to install two of the small Spring Air air tanks side by side.

There are two benefits to Spring Air retracts over most other brands of pneumatics. They utilize only one air line being air up/spring down. The second benefit is should you loose air pressure the gear will extend automatically.

I've heard the TT retacts for the RB are not adequete for the weight of the RB and the result is a lot of side to side swaying motion. These retracts only have 5/32" wires which is too wimpy due to the long gear legs of the RB.

Rich

Ditto to what Rich is saying.
My retracts are BVM with 3/16 wire gear. Definately dont go any smaller than 3/16 on the legs. I would also go "air" over mechanicals any day of the week if you can afford it. They are alot easier to install and very reliable. later.....

Miguel,

I've flown my RB about 6 times and it's a very nice handling warbird. It doesn't exhibit any bad habits even when slowed down, however it will settle into a high sink rate if you're not careful which will result in a really ugly landing event. As Ad Clark III has already mentioned, speed control is the most difficult part of landing the RB. If you lower the nose it will pickup excessive speed and once it's in ground effect ( about 4 ft off the ground) it'll just float forever.

In flight the RB is a great handling warbird, mine displays neutral roll stability and is a little neutral in pitch (Probably slightly tail heavy). It does require that you fly the plane, it basically stays in the attitude you place it. My RB seems to like quite a bit of rudder input to make nice balanced turns. If you don't get enough rudder in during a turn the RB skids. It doesn't do anything unusual, it just doesn't look good if you don't use the rudder .

Rich

Hi again!
Just one question. I have bought Robart 605 neumatic retracts, with 3/16" wires. The seller has recommended me to install 90º retracts so despite of wing diedral, the real Rare Bear has not the landing legs completelly perpendicular, but with some angle. Please, I have just read that you are installing 85º which I did not noticed, so it is my first aircraft with retracts. Please, do you advice me to change to 85, or with 90 it could perform also properly?

Thanks again in advance and very best regards,

Miguel

Miguel,

The real Grumman F8F Bearcat has an extremely complicated main landing gear. If you compare the distance of the LG in the wing from the centerline of the fuselage to it's length, you'd see that the gear is longer than the distance. So how does it retract ?? The gear has an additional trunnion, ie the upper arm/trunnion retracts outwards the LG leg retracts towards the fuselage. This is how Grumman was able to get the extra long gear into a shorter distance. This extra trunnion is responsible for the somewhat splayed out look of the LG on the Rare Bear. So yes it would be OK to use a 90 degree retract vs an 85 degree version. I used the 85 degree retract because I had a new set laying about.

Rich

Here's a Pic of the upper trunnion, you can clearly see that the trunnion retract outward towards the wingtip. Also note the outer edge of the oil cooler opening in the wing root.

Picture Courtesy of www.avweb.com

Here's a link to the article about the actual aircraft: http://www.avweb.com/news/columns/182122-1.html

I am in the process of building a TT Rare Bear and have followed the threat, but have two questions I sure could use some help with.

1. I have a Saito 120S I plan to install and I am in the process of test fitting now. Has anyone successfully installed this engine with out removing cowl for head cut outs? If so is it necessary to allow for aditional cooling exhaust? It appears that the engine needs to be mounted 90 degrees with the head and plug facing the left side for best clearance and exhaust. Can anyone comment here?

2. I have a new pair of Spring Air 103 HD retracts with oleo 3/8 struts and am stumped. This set apparently id setup to receive oleo struts directly and in fact the Robarts will insert about 1/2 inch and bottom out, but then they are too short. The Spring Air oles are longer and would make up the difference, but will not go in with out being significantly relieved.
What am I missing here? can anyone enlighten me please?

If you look on page 42, post 1040 there is a picture of the underside of my cowl and the cutout for the exhaust. Also look at page 43, post 1054 at the cutout on the front of the cowl to allow more cooling air in from the front. The darn spinner looks cool, but I found that it blocks alot of the airflow. The only other hole in my cowl is for the glowplug. This is for the 160 however, not the saito. I would think with your setup it shoud be similar? My retracts are BVM with wire gear so no help there. Post some pics of your progress

Thanks AD, I am still not sure I can make the Saito 120 fit with out relieving for the heads. This is the first time in 30 years I will have to mount the engine with the head on the left side... just seems unusual, but frankly matters not.

Has anyone tried an inverted mount with the 4 stroke and are there any issues other than those associated with a 2 stroke for inverted mounting?

Hello to all... been a while.
Finished my Bear last winter. Just got up the nerve to fly her. OS-160, Sierra Retracts.
Everthing checked and perfect.
1st flight.....Like a rocket! Wanted to climb. Dead Stick...perfect landing....end of rollout, right gear collapsed. Flipped plane over....no damage..........(So I thought...huge mistake)
Fixed Gear, refueled, got engine tuned and rolled out for second flight. (Lessen here: when you flip a plane over, you must take off the canopy and check to see that everything is in tact. What I ultimately found out was part of the ply frame broke when it flipped. I had extra weight here with a Sullivan Smoke module ect in there. It must have shifted toward the tail without me knowing it)
Plane took off, and immediately, we were in huge trouble...tail heavy...big time...She snapped back and forth several times and then nosed toward earth.....
End of story...

On the positive side...The wings and gear mounts held up very well, The stab looked great with the mods, but with the engine getting driven all the way throught the firewall and ripping through the fuse...she's a total loss.
That's why they call this a hobby...I have some great pictures of her, she'll be remembered. I think next winter, I'll build a Cactus Aviation Bearcat. Now that's a thing of beauty.
See tag line below! Next!

In the Hangar: GP PT-17 w/Saito 180, GP P-40 w/Saito 100, H9 PTS P-51, GP Ryan STA w/OS-91, GP U-Can-Do w/Saito-100, H9 Arrow Trainer w/OS-46.
On the Bench: H9 Corsair w/Saito-100, Giant Scale Planes F-6F Hellcat w/OS-120.
Crashed: GP Lancair w/Saito-82, Thunder Tigre Rare Bear w/ OS-160, 4-Star 60 w/OS-61, 2 Nexstar Traniers.