looking good.

I will leave the stabs the way they are, unless I can feel the the skin has not been bonded correctly to the ribs.

Looking at all the info in this thread, I can see the stabs have been beefed up, and someone even made them massive, and used heavy duty arrow shafts.....and even then, flutter just disintegrated the tail.
I saw another on RCG where he first used the stock wooden elevator pushrod, and it snapped during flutter, and luckily he got it repaired after the crash.
He then installed 2 elevator servos, and carbon rods still connected to the stock metal torque rods, and a few flights later it fluttered again, and the whole wooden servo box structure had been torn out.....it take lots of force to rip it all apart.

Im pretty sure installing the servos in the tail with direct short linkages will solve the problem..........in time we shall see

hay guys i wanna no do i have to balance this modle inverted or upright cheers

Low wing....always inverted for pendelum effect....opposite for high wings
Paul

I have been slowly making my way through this thread for a while and was surprised to see in the last page or so the much more current post dates.

I've been building mine now since early Sept 2011 and wish I would have noticed the bits about the tail tubes earlier. I did pull the lower skins due to water damage, (the previous owner(s) had not stored it in the best location). I Gorilla Glued in the large scale pin style elevator hinges and glass clothed the entire tails with EZCote.

This is not my first build by a long shot and even before reading of the control failures had tossed the stock hardware in favor of stuff that fit my comfort and reliability scale a lot better. I have a penchant for modding and have to say this plane is custom made for that.

Working back to front, basically the same as the build, here is a list of some of the changes. Many were made before I found this thread, so I feel I was at least partially on the right track.

1) Elevator servo moved to a new plate aft of the rear bulkhead with dual 4/40 ball links and rods. There is virtually no play in the elevators, but I plan to seal the hinge gap before flying.

2) Made an entirely new rudder Pull/Pull system with the adjusters up front near the servo wheel. The setup has a ball link tension setup to relieve the servo output bearings. I threw out the brass lower rudder pivot and installed one from composite. I try to avoid any metal/metal contact if it can be avoided.

3) Completely custom receiver and power distribution mount with isolators to help dampen the vibrations. Need to run the plane to check to see if the solid engine mount will cause problems, (more on that in a bit)

4) Custom power distribution center with a separate switch and charge port for the 2S LiFE system supply and the 4 cell NiMH pack stuffed above the engine is exclusive to the Rx.

5) I never did go with the mechanical retracts as the mere thought of connecting and disconnecting linkages every session was ridiculous. I originally had RCLANDER electrics mounted, but am waiting for a pair of EFlite 60-120's and will rebuild the mounts again once I have dimensions. The R/L could not tuck the wheels far enough into the wells.

With no central servo I was able to fit the 2S LiFE pack in the tank location and lift the tank in line with the carb. I had the option of adding a pump. Hate the idea of more connections, etc. unless the advantage outweighs the complexity. It was easier to keep it simple. I dropped the tank capacity to 12oz. I run this size in the Skybolt and at the end of my normal 9-10 minutes of honking I still have 1/2 tank or more on landing. I will start conservatively in any event to check battery capacity so will be able to gauge fuel consumption as well.

6) On that note I have a pair of modded Robart struts and since I predominantly fly off grass opted to go away from scale and move the scissors to the trailing edge.

7) The cockpit and canopy are self contained and quick release to allow access to the switches, battery status indicators and remote glow. It was a ***** to build and work through the rather small cockpit and firewall openings. The leading edge of the canopy frame are fitted with 3 C/F rods and the back locks down with a pair of homemade spring latches. I wish I could take credit for the idea itself, but I use whatever I can and my friends turbine jets use a similar setup. I hope that works just as well on my Nitro Planes Seawind as the canopy on that one is very thin plastic and held down with a plethora of screws.

8) I originally tried to fit the Saito 125a into the stock isolator mount, but it just would not work very well. I opted for a composite mount that I hope has enough damping. I have a Graupner 14/8 3-blade. Unfortunately it did not fit the spinner at all and after some hacking I though it looked a bit ugly. For now I have a 2 blade wood prop for first run and break in to be replaced with a composite prop for first flights.

9) The cowl is fit with a sim radial with my stock custom ducting to direct cooling air over the motor. Learned the hard way on my Saito powered Skybolt that I need to follow the exact same rules and methods we do with full size aircraft. After a dozen or so setup and test flights the 'Bolt did not finish the first run with the cowl on before the motor seized from overheating. The ducting has worked perfectly now for close to 250 flights on that one and worked just as well on my OS FS91S powered Harvard.

I will post some pics shortly, but for now I will agree with many in that this plane fell well short in design, materials and construction, to the point nearly ALL my kits required less effort to get to where I could feel I trust them. The first sign of trouble was when I removed the wing servo pods. The wood simply fell to pieces in my hands, none of the glue joints holding at all. At least they use UltraCote White. That is one of my standards, so have lots in stock.

I had quite a bit of trouble with Slimline. Getting the rather unique adapter for the 125a proved to be a ***** with 4 tries and 4 months timespan to finally arrive. The muffler is finally mounted and cowl cut to fit. Oh yeah, I don't know if they had a different supplier for the fuselage and canopy, but the paint simply pulls off the cowl even removing high grade masking tape.

As promised, here are some pics. I don't have any really detailed of the tail servo installation. That will have to wait till the tailwheel cover is off again.

hay guys i had my first flight 2 weeks ago and it lasted seconds way to tale hev.

i balanced it like it says in the man but apon take off i was hovering lol littorally!!
well i poped my dacks and went back to idle but to late, only damaged 1 wing and is being repaird as we speak.
and for those wanting to no i have a turngy 26cc in her just for fun

where is the best balancing point for this modle??? plz help and when up and going agane ill try to get some vid for you all

ta

I think other than detailing and system organization the fuselage is complete. As noted the gear mounts were notoriously substandard and with the arrival of a set of EFlite 60-120 mains I had reason to tackle this mess. One of the difficult decisions was to remove my carefully fit wheel wells, something that would cause some damage to the wing skin and covering to accomplish. Oh well.

Started with the right wing and soon had most of the hack and slash worked out. I left the remains of several nose ribs to give me some indication of position and dimensions. First was to carve out test ribs from high grade 1/8" balsa sheet. It took a few first attempts to get the contour correct with the smaller outboard ribs following along quickly. This slow first step was the same when fitting the L/G mount pad as the retract and leg had to be fit to the mount and then dropped approximately in place to get some measurements.

Then it was back to the test ribs, repeatedly measuring and cutting to get the pad to sit where intended. Again, it was the first rib that took the longest. The end result has the axle sitting right on the seam between wing and fuselage and to get it recessed enough for comfort some trimming of the original mechanical gear wire guide was required.

Transferring the balsa patterns to the ply was quick and easy with the table saw doing short work of all 8 ribs, (yes, this should be STRONG!). The first test and glue worked well and the assembly comes out of the wing complete for final bonding. There is some work to get all the ribs sanded in perfect line, but all told it came to this stage pretty well.

Time to attack the second wing. Knowing where to cut saved a bit of time and this loose assembly was sitting in place within 20 minutes. At this point I need to do some more fitting to try and get both gears as close to identical as possible. Once the mounts are bonded in place it will be time to work on a skin and gear door setup. Doubtful any of the stock gear pocket will be reinstalled due to interference with the gear offset.

A few points of note: The original wood was held in better than expected from my prior bracing, but the wood itself practically fell apart. Whatever they use for ply was seriously deficient. The second note was that the EFlite retracts are very nice bits of kit. One of the nice differences is that the mount holes are further out from center, meaning I have no interference problems with the blind nuts. In that regard I borrowed the 87 degree countersink bore and worked on both sets till the screws fit flush. Not really necessary if I had button head 6-32 cap screws.

In the set of pics you can see the sequence up to now. In the last shot you can see the assembly fit to the R/H wing. It may look off, but the leg is within a few thou of straight to the spar. Some have found it necessary to angle the gear forward to reduce the tendency to nose over. I'm hoping the fact I am using Robart gear instead of the original spring gear that would bend aft under load work the same.

Latest progress pics shows little of the attention paid to the framework to get the skin and doublers set at the correct height all the way along. As usual all the hard work gets hidden.

In the last update the gear mounts were simply held in place with clamps. Both are bonded in permanently now and the extra sub ribs to support the skin between the main ribs were installed. Next it was to pattern the skin outline, cutouts for the doors and the door bulkheads and I ran into a bit of a Homer there. I used the originals to pattern these and missed the fact they would catch the scissors on the gear legs. Of course, as you can see in pic #4 that was found after the skins were bonded down......DOH!

For a bit of fun the leading edge and inboard skin make a bidirectional kick to encircle the inlet and this took a bit of time to make the skin outline follow with good accuracy. Even after wetting the wood a gell cell batt had to weigh each skin down till fully bonded.

A new pattern with a bit more room was called for and I tried to remain true to the original outline as much as possible, but nitpickers may find fault with them once installed.

This afternoon I finished final sanding one wing and decided might as well work on the covering. Luckily the prior note they used UltraCote seems accurate, as the new covering blends in well, (at least indoors).

Don't know if the second wing will be on the table right away. March break is here and the family is heading to visit. Everything sharp, sticky or even mildly dangerous is hidden away. And at this point I have not decided if anything will be done to contour the inner wells.

Down to the wire now. Early this week I decided to dress up the wheel wells and was looking for something to sheet in the openings. Light balsa was too brittle, even when wet so I opted for thin cardboard sheet, (or very thick paper depending on your definition) like those separating gangs of forms at work. Once the pattern was cut I transferred that to the paper and glued them in. Thinned some epoxy and brushed that on, letting it soak in before curing. Worked out well until I wet sanded it and found the penetration was less than hoped for. Ripped it back out and went searching again. Still had some white plastic sheeting used originally to protect the bottom of the Polaris and tried that instead. Seemed to work fine so completed the other 3 sections the same way. Saved having to sand and paint, so even though it took two attempts in the end it worked out better.

I fabbed new extensions and fished them through the wings yesterday, bolting down the retracts for hopefully the final time. Now it is routing the Y-adapters for the gear and ailerons.



With the nice weather had no excuse not to take it outside, fuel and fire it up for the first time last Sunday.

I checked the CofG beforehand and with the huge stock spinner and 3-blade Graupner prop it comes remarkably close to the aft wheel well bulkhead. However, with a 2-blade and the smaller spinner it may require some lead to fall back in range. As it stands all the changes bring the plane to close to 12 lbs sans cowling. I new all those mods were adding up. The most significant change was the gear and mounts. The Saito weighs far more than the stock recommended engine, but that's power in place of lead so no complaints.

It took some fiddling to get the mixtures close and it still needs tweaking to run the way I like, but 9000 RPM with a 14/8 prop is pretty respectable, especially considering the motor is not broken in yet and the 10% fuel is left over from last season. I hope to grab a case of 15% at the Toledo show soon.

There were the inevitable bugs that cropped up. One of the switch nuts vibrated loose and the left aileron did not work. Already pulled the extension and found the ground wire had broken at the pin. Already repaired and working to relocate the connection to reduce stress.

As for vibration, even though the motor did shake enough to make fitting the allan wrench and screwdriver to the HS and LS needles entertaining, the fuse and systems did not vibrate anywhere near the level I had feared. The tail and radio tray were relatively solid.

p.s. Sorry for the ugly grass. It is supposed to be under a foot of snow this time of year.

Looking GREAT!

Don

Looks good.

Im still modding the tail surfaces on mine...

SJN, any pics to post?

I have a few

Few more of the kit out of the box

Since im going to install the servos in the elevators, my plane will be tail heavy.

So I decided to remove some of te wooden structure behind the CG which I will not be needing anyway.

I will be using my ASP 120 4 stroke in mine.

The prop nut is a little further forward than I like, but I cant move the engine further back because of the stock rubber engine mount.

I could use a normal nylon filled mount to get the engine a little further bach, but I want to see how the included mount works out....can always change it later on.....if the plane survives

cowl fits nicely.

I want to make the acces hatch easily removable.
So I built a strutcure under it to stiffen it up.

Wasn`t satisfied with the fit of my internal bracing, and te carbon rods are easy to lengthen or shorten to get the perfect fit.

Servos installed in the elevator

My elevators sucked rigt out of the box.

One of them weighs half of the other, and the light one has no torsional strength at all.
The wood is VERY soft.
First I tried to glue a trip of carbon to the trailing edge, but it was not enough.
Instead of building new ones, I decided to laminate carbon weave into the top and lower surfacees, with bals on the outside so I easily can recover them with film.

If thisd plane ever goes in, the elevators will be the only thing undamaged for sure.....they are now tough as nails.....and ofcourse a gained a little weight at the worst place possible.
But all have to live with it.

I also deliberatly made my elevator trailing edges very blunt, hopefully to reduce the tendancy of elevator flutter.


This is where I have got to for now.....I have not touched it for about a month.
I have a few other projects that im building on at the moment too, but il get back at this awesome looking plane soon

SJN, a blunt trailing edge is a relatively inexpensive counter to flutter, but as a fixed wing and heli pilot and maintenance engineer I know of other places more effective to look into. My friends also fly turbine jets well into the 200MPH bracket so I use them for confirmation and ideas. To be honest that is where I got the idea for the cockpit hatch.

First and foremost is NO SLOP in the controls or hinges. This is the reason I ate the weight penalty and moved the servo above the tail gear. Other than structural weakness a control surface that has play will inevitably reach resonance at some airspeed and/or engine/airframe induced vibration. If not dampened out it can quickly amplify till destruction. Even if both the stab and control surfaces are extremely rigid, a minor flutter may not be recognizable from the ground, but will play merry hell with the linkage and servo mechanicals.

I see from the pics you have the thicker stab joiners. Sure wish mine came with that mod.

Just a quick update. Hit the Toledo Show on Friday armed with the diameter for the wing joiner tube. This was not one of the higher items on my "Lust List", just something to keep an eye open for. Well, as it turns out I found a booth with 30mm C/F tubes for sale. Considerably less than what I had found online, but $55 still hurts![]

Did a quick check when I came home and the tube definitely did NOT fit into the wing without a sledge getting involved. I put it aside to work on other projects and when relaxed let the thought bang around. I did have a steel tube around that was slightly too small and the light went off! I glued a 2" strip of 800 grit to one end and wrapped it around, cutting some off till the wrap fit tightly in the wing. Several hours of work on both the wings and sanding the tube finally has a nice easy fit. My friend suggests graphite powder is used to lube the bits when they are field assembled and take apart. I will have to try that out.

NOTE: I also found the other wing had the same problem that the bulkhead at the end of the wing receptacle was toast. Seems T/T added a ply doubler on the fuselage side of the last rib to anchor the assembly, but that soft balsa rib definitely does not cut it as a tube stop. I cut out another lite ply end plate and with a LOT of difficulty fed it through the wing opening to rest against the end of the tube. Holding it in place I carefully dropped both thin and thick CA to wick the plate to the end. This was done outside for better lighting and there was some inevitable mess on the inside of the tube. Back at it with the abrasive wrap for a bit. This would have definitely been a lot easier to do with the wing skin off and something else T/T skimped on. Just hope I found all the critical weaknesses before they come out in flight.

That should not be too far away. Weather is getting better and I can only think of a couple more minor items to tweak before first flight.

Well, it's down to guts, timing and weather now. I had to add over 1.5 lbs of lead to the nose to balance and moulded it into bricks to fit within the front of the battery extension over the motor. There is one smaller piece mounted on the front externally and that will be removed at the time of cowl installation. I will try a few flights with it off to check systems and settings.

Due to the added stress I braced the battery box down to the firewall.

Hopefully should have pics and vids soon.

p.s. I've had nothing but trouble with the retracts on the Harvard. Their geometry has them traverse down and aft under landing loads and they act like pole vaults on even the smoothest touch down. I've ripped them out and another set of those beautiful Eflites are coming, along with a better set of Robart legs. I'm going to copy my mount mod from the Bear to that one and the plan is for this plane to finally land as well as it flies.

Good luck on the maiden.

This is a fantastic looking plane
(this one is not mine....but just a nice picture )

I'll jump in here. My second Rare Bear is just about ready to fly, pics to come soon. This one is electric, E-Flite Power 110, Castle 75HV, 8S 5,000's. No visible screws for the cowl, hatch, tailwheel cover, etc. Just finishing up the decals. It is the updated kit with the extra stabs. I moved the elevator servo to the tail.

My first Rare Bear died after a full-throttle dive fluttered the elevators off of it. I knew it was a possibility, and I figured it was better to find out during the maiden...and I did. It had an O.S. 160FX in it. Pics of the aftermath below.

Sessholvlaru, did you have the stock elevator linkage on the ill fated first one?