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Old Jul 22, 2011, 01:00 PM
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FireyFate's Avatar
USA, AZ, Surprise
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Originally Posted by Wretcho View Post
I have read your posts carefuly and tried all of your recommendations but still having the plane corck-screw to the right on anything above 6mm up elevator throw(loop), the stabs are now more carbon then foam

They did show a heap of flex prior to the CF going in but no real change. I then started playing around with the CG, moving it back bit by bit each flight. It got worse. Pulling my hair out with this issue, apart from it the plane is great!
Somebody ought to make their own balsa and ultracote horizontal stab/elevator for this thing and see what it will really do.
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Old Jul 22, 2011, 01:49 PM
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Australia, WA, Aubin Grove
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Ok here is a thought the whole rolling with elevator input is not completely due to flex. I've been reading Scott Stoops's book Mastering Rc Flight and in there he discribes a few forces which act upon an aircraft in flight, one of which is called gyroscopic precession and I don't recall the other of the top of my head. I know when I read it, it describe this tendancy completely. I don't have the book with me at the moment so I can't go into particulars, maybe some one else could chime in.
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Old Jul 22, 2011, 02:41 PM
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Originally Posted by Ben82 View Post
Ok here is a thought the whole rolling with elevator input is not completely due to flex. I've been reading Scott Stoops's book Mastering Rc Flight and in there he discribes a few forces which act upon an aircraft in flight, one of which is called gyroscopic precession and I don't recall the other of the top of my head. I know when I read it, it describe this tendancy completely. I don't have the book with me at the moment so I can't go into particulars, maybe some one else could chime in.
Well, I fly 2 different planes designed by Scott Stoops, and his planes don't do it what-so-ever . 3DHS 41" Edge, and EPP Extra.
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Old Jul 22, 2011, 02:48 PM
Jay Bird
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Ohio
Joined Dec 2004
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Yes, but I think gyroscopic precession would only cause a yawing moment to the right and not a rolling one. When we pull back on the stick we're effectively 'pushing' on the bottom of the spinning propeller in an effort to change the plane in which it is spinning. Due to gyroscopic precession, the force is realized nearly 90 degrees ahead of where it was applied. A yaw to the right when increasing pitch is normal and can be corrected with rudder. I think what many people (including myself) see with this model is an abnormal roll to the right. I still believe the primary factor is the elevator (or entire empennage) twisting to the right from the force of the push rod.

The other three aerodynamic factors most commonly observed are P-factor, spiral slipstream, and torque. Without going into them too much, P-factor will produce a yaw to the left at high angles of attack, the spiral slipstream will produce a yaw to the left at high throttle, and torque will produce a roll to the left as throttle is increased and to the right as throttle is decreased. All of these factors are most noticeable at low airspeeds.

BTW, Scott Stoops' book really is great and I'd recommend it to anyone who wants to become a better RC pilot.

Jay
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Old Jul 22, 2011, 07:12 PM
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Waynesboro VA USA
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This rolling while looping is actually fairly common, my SU-26xp does it and so do most of the 3D planes on my clearview sim. Wish there was an easy fix. It does seem to be less of a problem for me if I pull back slowly to full travel. I thought it was a stall torque roll effect.
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Old Jul 22, 2011, 09:45 PM
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Pennsylvania
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Originally Posted by MARCOELDRAGON View Post
This rolling while looping is actually fairly common, my SU-26xp does it and so do most of the 3D planes on my clearview sim. Wish there was an easy fix. It does seem to be less of a problem for me if I pull back slowly to full travel. I thought it was a stall torque roll effect.
Probably not torque roll, being almost square (10.5x9) the tips can stall with a lot of throttle and little airspeed, they create a lot of drag, and dramatically increase torque roll to the left, not the right, this is part of the reason I run the 12X6, less torue roll, lots more thrust. Might be something not square, if the elevator is angled relative to the wing it can do it, doesn't take much, a v-stab/rudder that isn't vertical can cause it too, you can usually diagnose it by comparing an upright loop to an inverted or outside loop, if the outside loop rolls worse, check the rudder, if it seems about the same, or seems to get better, check the elevator. Sometimes if trim is off, usually with 2 surfaces "fighting" each other, like rudder trimmed to the right, and aileron trimmed to the left it can do it too while flying level at speed.

Mine has no issues at all with rolling from pulling elevator, even when stalling, just the normal left roll and left yaw from torque and the spiral slipstream on the tail. My elevator throws are about 50mm in each direction, I snap to hover, and have even done waterfalls with the Extra, moves that require a ton of elevator with no issues, I can loop as tight as I want, or as big as I want at higher speeds, without stalling, it just tracks straight, at slow speeds, and stalling, it just takes the "normal" right rudder/aileron correction.

There may be something wrong with wretco's plane, but outside of the few things I know can cause that issue, it's hard to really suggest much without some pics looking straight from the tail, or a short video closeup of the throws, they might help to see what is going on. Limiting the plane to 5mm throws really handicaps the plane, there is also the possibility that you don't have enough throw, 10mm or so throw might give you just enough to pitch into a tip stall(and the Extra will stall abruptly) when the wing goes above the critical AOA, but not enough throw on other surfaces to control the plane through the stall. It could also be something like unknowingly pulling the right stick to the right instead of straight down(very common with newer aerobatic pilots), raising the resistance of the sticks can help.
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Old Jul 23, 2011, 07:01 AM
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Waynesboro VA USA
Joined Dec 2010
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Alucard,
You may have something there with the stick not being pulled straight back, at least in my case. It wouldn't take much deviation to produce that sort of roll. The natural tendency for a thumb flier would be to pull to the bottom right rather than bottom left especially in the heat of the moment. My Extra was used and came to me set for maximum throws (rods in outside hole of servo arm and inside hole of control horn) In static testing I am seeing the entire horizontal stab and elevator being pushed back perhaps a 1/4 inch on the control horn side. Probably need to check the tape. I plan on doing your tail stiffening soon as I can get a bit better at landing this beast. Thanks for all your info.
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Old Jul 23, 2011, 12:02 PM
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Originally Posted by MARCOELDRAGON View Post
Alucard,
You may have something there with the stick not being pulled straight back, at least in my case. It wouldn't take much deviation to produce that sort of roll. The natural tendency for a thumb flier would be to pull to the bottom right rather than bottom left especially in the heat of the moment. My Extra was used and came to me set for maximum throws (rods in outside hole of servo arm and inside hole of control horn) In static testing I am seeing the entire horizontal stab and elevator being pushed back perhaps a 1/4 inch on the control horn side. Probably need to check the tape. I plan on doing your tail stiffening soon as I can get a bit better at landing this beast. Thanks for all your info.
Didn't even think of this, or the way I built this plane being different from the manual. The tape will keep the elevator from flying off, but can allow some slop fore and aft, same with the wings, other designs like the CZ Yak's bolt on tail with spar are much better. The V-stab has a long cutout, and plastic plates glued in, so there is precious little foam actually keeping it straight. The tape just holds it in place, doesn't add any strength or rigidity, wouldn't matter if it was a warbird, matters little if you keep the throws small, but it does matter if you are flying the plane hard, and pulling big rates. I use CA for the elevator. First thing, as soon as it comes out of the box is to make sure all surfaces are flat and level, a warped aileron or rudder can cause goofy coupling, and is far easier to fix before the plane is together, it will also affect all other measurments. Just push the surface centered, look down it, or lay a flat edge on it to see if it is warped or twisted. If it is, then warm it evenly with a hairdryer, and gently twist it straight, it will spring back a little, so you need to twist a bit past straight, make sure it looks good, then let it cool, warp gone.

I line it up, and use a steel drafting ruler to make sure that the same length of H-stab is sticking out of each side, and that the tips are the same distance to the centered aileron tips, measure again to make sure the H-stab tips are the same distance to the aft end of the wing pockets, and by eyeballing it looks parralel to the wing when viewed from behind, once it in place, I use 2 peices of painters tape to hold it in place, flip the plane over, re-check my measurements, and drip thin CA around the plastic elevator mount on the underside, just a drops on each side, then push the upper v-stab together with the tailwheel bracket on the underside, just enough to hold it firmly after 10 seconds, don't use kicker. Next I flip it upright, set it on a flat surface with the wings on pretty much anything that will hold it level, can't trust the landing gear to be perfectly level, in fact it is easiest if this is done before installing the gear, shoeboxes, peices of wood, a CG or plane stane, pretty much anything works as long as it is level, and on a hard, level floor. THe bottom of the elevator is glued with just a couple drops, and can be broken free if needed, but the top should be free to move. Measure to the wings to make sure they are level, then measure to each side of the elevator, they should be the same, if all is well, add a couple drops of thin CA to the top, just like the bottom. If one side is off by a little, twist it straight by hand, then while holding it, add one drop of thin CA on each side, press together, and re-check. If it is out by a lot, then find out what is wrong, plates glued crooked are usually the cause, pull them off, straighten them, and re-glue them.

When all is straight, run a light bead of thin CA to the edge of the mounting plate(just needs a very small ammount, too much will drip out), it should flow into the joint, hold the plane on it's nose, and add a couple drops in-between the plates on the top and bottom center of the h-stab. hold it gently together to allow the glue to stick, then use a bead of medium or thick CA on the seam between the plastic plate, and the h-stab, and hit it with kicker, re-check everything, and it should be perfecctly straight, completely rigid, and the only thing that may flex is the entire tail itself, or unsupported surfaces, which would have the CF mods to correct. In the off chance that you need to remove the elevator, it isn't as simple as peeling tape, but slipping one of those break off knife blades under the plastic, and kinda scraping aggainst it can work once, then you have to chip out the CA, and go through it again, for most, if there is a problem where the fuse needs replacement, just buy a fuse and elevator together, if the elevator is damaged, it can be cut and taken out easier if it is destroyed. If you take the time to line everything up, and pay attention to the details, you will get a better flying plane as a result, goes for everything. Of course if you are still buying airframe parts all the time, and crash often, then maybe the difference in rigidity won't be apparent to you, and it won't be as important as having easily replaceable components, if that is the case, just beat it up, learn, and have fun, and do the mods AFTER you are confident with the plane. In a lot of cases, for the smaller 3 cell foamies, I glue the wings in too, makes them stiffer, and you can still usually replace servos if needed by peeling tape, wrapping string around the lead, pulling it through, tying to the new lead, then pulling it back in, all without taking the wings off. If one is damage, and cannot be fixed without replacing, you just have to end up cutting it out. For those that seldom crash, and when they do it's either just a minor bump without damage or a big foam shredding disaster that needs an airframe, the rigidity of glued parts can be really nice, and definitely noticeable.
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Old Jul 23, 2011, 12:44 PM
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Pennsylvania
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882 Posts
Did a quick video of my throws, the elevator has my CF/epoxy reinforcing of the joiner, embedded .5X3mm flat CF in the elevator, 2mm CF rod in the V-stab, elevator glued in, and all hinges slotted and taped, just the mods I have explained in the last few posts. The moving surfaces don't twist, and are perfectly straight, the attatching stabs don't move either, makes the plane fly far better than stock with only a couple bucks worth of materials, and an hour at most in work. I do ave a knife edge mix, so you can see the elevator move a little with rudder, this is due to the mix, not flex.

Extra300 throws (0 min 46 sec)
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Old Jul 23, 2011, 05:46 PM
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Waynesboro VA USA
Joined Dec 2010
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Alucard again great info! I have a Word Document saved with all your recommendations in it. This should definitely take care of the slop in the tail. I made 2 flights earlier today and managed to do decent landings both times without nose stands or knocking the gear off. Used an Aeromaster 11x6 both flights and was very pleased with it. Probably will go to APC 12x6 after I get the landings down pat. Managed to pull off a fairly low KE lap around my landing area. Really loving this plane more every flight.
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Old Jul 23, 2011, 07:09 PM
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Hey guys, my buddy at the LHS had an Extra 300 hanging up, and I mentioned I was thinking of getting one (mostly have warbirds and micros) and he let me take it home to fly it and see how I like it. Well right off the bat the right wheel came off on take off and I didn't even get off the ground.

I removed the landing gear and decided to HL it. Plane flies nice, really fast too. Fun to fly. When I landed in the grass I snapped the prop. I noticed it likes to come in pretty fast and I tried to flare it after I cut the motor, it didn't hit real hard but still snapped it. No biggie just gotta get a new one. Not sure about the wheels, maybe they need some locktite. Thoughts?
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Old Jul 23, 2011, 08:27 PM
Jay Bird
jshall755's Avatar
Ohio
Joined Dec 2004
127 Posts
Yeah, just use some blue loctite on the wheel nuts.

They had a manual addendum for that problem:
http://www.horizonhobby.com/ProdInfo...t_Addendum.pdf
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Old Jul 23, 2011, 09:01 PM
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Originally Posted by MARCOELDRAGON View Post
Alucard again great info! I have a Word Document saved with all your recommendations in it. This should definitely take care of the slop in the tail. I made 2 flights earlier today and managed to do decent landings both times without nose stands or knocking the gear off. Used an Aeromaster 11x6 both flights and was very pleased with it. Probably will go to APC 12x6 after I get the landings down pat. Managed to pull off a fairly low KE lap around my landing area. Really loving this plane more every flight.
Thanks for the compliments. I can be a bit neurotic about stiffening planes, but the biggest problem with foamies compared to balsa is almost always the inconsistencies that come with flexing, and to a lesser degree the weight. The goal is to use the smallest ammount of glue and CF to get the largest improvement in rigidity. With most planes, you can just wiggle the sticks, and watch what moves that shouldn't, then figure out a way to put a strip of CF or CF rod to oppose that flex. If you watch a video of the tail flying around, you can see just how little movement is needed to roll or loop a plane, so even a small amount of flex, or assyetric movement can cause a big issue with handling. You don't want to goo too overboard with adding peices though, the glue weighs just as much if not more than the carbon, and being about twice the distance to the CG from the nose means that you may have to either add twice the ammount of weight to the nose to balance the plane, or push the battery all the way forward(it is only 1/4 the distance to the CG, and even then, you can only move it so much. The roughly 20" of flat and round CF and glue adds probably 1/4 oz to the tail or 7 grams, meaning you would need 1/2 oz of weight in the nose to counter it, or move the battery forward about 1/2-3/4", luckily there is room for this, and my plane flies best with the battery about 1/2" from full forward, stock, it was about 1" back to get the same CG.

With the 12X6 prop, the tips pretty much have 0 clearance with the fuse level on a hard surface. Larger wheels only lift the body 1/2 of the increased diameter, so if you go with even 3" wheels over the stock 1 3/4" wheels, it only raises the fuse a hair more than 1/2". Raising the gear is a better solution, raising the gear 1/2" raises the prop clearance 1/2", you can either bend the stock wire gear to get more clearance, straightening it, and bending it down, fab up some new gear from a length of wire, or the 3rd option I figured I would screw around with after reading your post, and thinking about all the peopehaving a tough time with the Extra in grass. I had a CZ Yak commit suicide back around January due to a faulty stock elevator servo, still have the parts and hardware that was left, bought another PNP Yak, and figured I'd have a few spare parts. Turns out the much larger CZ Yak landing gear sorta fits Instead of lifting a mere 1/2" like 3" wheels would, it lifts the plane a full 3", and widens the track from 11" to 15". Just have to widen the slot in the gear plate from 1 1/8" to 2 1/16". There would probably be a ton more stress on the plate, so unless you have already epoxied the crap out of it, it probably wouldn't last one lading before getting twisted out. It does add 10g of weight stock vs stock(removing wheel pants ought to cut a few grams), mostly from the much thicker wire of course it will also PO the scale nazis. Painting the Yak wheel pants orange now, can't wait to see how it flies with the bigger gear. Took some pics after the initial measurements, it was just placed in the gear mount channel, being I haven't cut it out yet, so when completed it will sit about 1/2" lower, really doesn't look too ridiculous, and will make running a 12" prop, or flying off of grass a problem of the past.

stock gear with 2.5" dubro wheels.
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Sitting on the Yak gear
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Doesn't look too insane. Basically 1:6 scale gear in a 1:7 plane. If it still flies good, AND vastly improves ground handling, it just may be worth it.
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Quote:
Originally Posted by tamiyafan1975 View Post
Hey guys, my buddy at the LHS had an Extra 300 hanging up, and I mentioned I was thinking of getting one (mostly have warbirds and micros) and he let me take it home to fly it and see how I like it. Well right off the bat the right wheel came off on take off and I didn't even get off the ground.

I removed the landing gear and decided to HL it. Plane flies nice, really fast too. Fun to fly. When I landed in the grass I snapped the prop. I noticed it likes to come in pretty fast and I tried to flare it after I cut the motor, it didn't hit real hard but still snapped it. No biggie just gotta get a new one. Not sure about the wheels, maybe they need some locktite. Thoughts?
lot of early models had that issue, the little wheel nuts were soft, stripped easy, and backed off easily, lock-tite or CA will help them stay put. Swapping off the wheel pants, and going with something bigger helps ground handling on grass, then just use wheel collars to keep them in place.
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Old Jul 23, 2011, 09:32 PM
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Waynesboro VA USA
Joined Dec 2010
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Looks good to me. Course I'm not a Scale nazi. If it keeps from knocking the tips off the prop I'm all for it. The wider track would be a help too. Here is a pic of mine with 3 inch lite wheels.
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Old Jul 23, 2011, 09:52 PM
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As it turns out, the Yak wire gear would go up into the battery compartment(hump in the center is about 1/2" taller with only 1/4" of room to spare, won't work without some extensive bending or cutting and welding. Well, at least it looked promising, caught it while measuring, before putting the saw to anything, so scratch that. Although If I get some time to play around with my welder, might still be able to make it work, and without cutting into the stock gear plate.
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