wjcalhoun

Did you get your new van Mike (on topic, to transport your R70)?

microdon2

My Feedback: (47)

wjc - didn't get the van yet. Now I"m looking at my current car and liking it better. I've heard you're not supposed to get emotionally attached to your car, but I can't help it. Though I don't know HOW I'm going to fit that 103" 260 back into my CRV if I leave the gear on. (IF I ever get it working). That plane is HUGE.

orthobird

My Feedback: (1)

hello microdon, qick question for you. i have a JR 9503 radio and it can program. can you explain to me what is cause and effect of the "expo" program, on lets say the rudder or ailerons. i have prgrammed dual rates for all 3 surfaces, and it has an option for this, i just dont know what it is. ive tried to read baout it, but i just dont grab concept. could you explain to me? thank you

microdon2

My Feedback: (47)

Orthobird - increasing or decreasing the exponential setting either increases or decreases the rate of response of that control surface. So, in my example, the plane was "twitchy", or reacting too "jerky" for my liking. By adding expo (or you could say, "reducing" expo, depending on how you look at it) I slowed the rate of change of the elevators (and also ailerons). So the plane flies smoother - less jumpy - and more in your control.

When you manipulate that particular control surface, the reaction of that control surface is slightly delayed, but still comes up to the point you "asked for", but the rate of change is exponential - like an upward curved line on a graph - with the slope increasing slowly at first, and then building. Normally the rate of change would be linear - straight line - like a 45 deg angle - but that may be too much change too quickly, depending on the plane, the control surfaces, how you like to fly, etc.

At least, that's my understanding of how expo works. If anyone knows better pls chime in.

Conversely, you can add POSITIVE expo, so that your control surfaces respond MORE quickly, in an exaggerated pace, than normal. 3D pilots might use this (I sure don't).

btw - To change expo to reduce reactivity of your control surfaces using Futaba transmitters you DECREASE expo (go into negative numbers). On JR radios it's just the opposite - to reduce reactivity you INCREASE expo (go into positive numbers). (just learned this recently). Now if THAT isn't a formula for confusion and possible disaster I don't know what is.

ahicks

My Feedback: (2)

An example of how expo might be used might be when you're landing. You come in, give the plane just a hair of up elevator to slow it or to flair - and the stupid thing balloons on you. "Adding" some expo there, might soften your "up" control input to minimize or at least help control that ballooning?

I don't know what everyone else uses, but I generally will start at 35% then adjust up or down from there depending on how it "feels" from there. Aileron, rudder and elevator, and I do that on high and low rates.

lopflyers

My Feedback: (12)

[]r. I've heard you're not supposed to get emotionally attached to your car, but I can't help it.

Though I don't know HOW I'm going to fit that 103" 260 back into my CRV if I leave the gear on. (IF I ever get it working). That plane is HUGE.
[/quote]

Cant get attached to a plane either.

orthobird

My Feedback: (1)

lopflyer= do you have a picture of the plane and the car?

wjcalhoun

Ortho
More on expo, if you really want to know.

JR/Spektrum calls expo 'positive', whereas to achieve the same curve in Futaba, it is 'negative'.

Expo does not really delay the response of the control surface, but rather changes the relationship between stick and control surface, as microdon stated.

Be careful, because differnt radios use 'positive' and 'negative' differently: - JR positive, Futaba negative expo both cause a concave-upward surface-stick response curve (which is generally what you want)


So an example:
With NO expo, if you move your elevator, rudder, or aileron stick 1/4 of the way over, the surface will move 1/4 of its full travel. 1/2 stick = 1/2 surface travel, etc.

With expo as above, 1/4 stick may cause 1/8 surface; 1/2 stick-> 1/4 surface; 3/4 stick-> 5/8 surface; full stick, full surface. Just an example. Expo softens the response around the stick neutral point, making the plane less twitchy. It allows you to have large control surface motions, yet maintain fine control of the surface around the neutral point allowing larger stick movements than you otherwise could make.

I use different expos for different total throw rates: low rates->expo about -30 (I am futaba); medium rates->expo about -50; high (3d) rates->expo -60 or -70.

I also use expo on the throttle channel to linearize the throttle response which is particulary non-linear with gas engines.

orthobird

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thank you so much, this is a great explanation.

Luchnia

My Feedback: (21)

The X9503 is a fantastic radio...very nice. I am bias 'cause I have one

If I am not mistaken you can change various points along the scale of expo. I have not messed with my settings in a while so grabbing this from memory. Say for instance you wanted your throttle to react differently and have a different curve at 25% and again at 75%. You can find tune the settings for your personal preference.

It is sort of like swinging a hammer and you decide for the first part of the swing you want to go slow and then after 50% you decide to go fast and close the gap up on the distance as well. Not the best explanation, just the only one I could think of right now There is a guide on youtube that explains expo and does it very well. Just do a search to find it.

Also, the X9503 will allow you to change servo speeds, an example would be slowing down the servo speed for LG retracts to give it a more realistic movement.

ahicks

My Feedback: (2)

Quick note, maybe others are not bothered by the elevator trim changes as your speed changes? If it does bother you (like me, I've been *****ing about this wing since I started flying it), you might try doing as I've just done and install a washer between the firewall and motor mount on the 2 upper bolts. This will give you some additional down thrust, and will likely force you to elongate the lower cowl mounting screw holes.

What the down thrust does is the faster you go, the harder the engine pulls the front of the plane down, pretty much neutralizing those elevator trim changes with changes in air speed. Have only had it out once since the mod, no downside noticed so far. It does not balloon noticeably when power is reduced at WOT (that can be a problem sometimes). Inverted flight still requires a lot of down, no difference there, but everywhere else it acts like it's much more neutral, like a symmetric wing! Very little trim change from a walking speed to full bore! No more feeding in down elevator to keep your vertical climbs vertical?

The amount of down thrust necessary to do this is often something you need to play with. I used washers that are about 3/4" x .020. So not too much required for my 20cc RCG using an APC 17x6. More or less power and more or less pitch will affect your down thrust requirements. E.G. a faster plane may require a little more down thrust/thicker washer, a slower one, thinner? FWIW, -Al

Luchnia

My Feedback: (21)

Let me see if I got this straight. You add down thrust to bring the nose atitude down more as the speed increases? If the nose is up too much what other problems would that cause?

I have a plane that flies reasonably well except when it knife edges it goes toward the wheels and it does not feel as smooth as it should be. It is balanced well yet still seems to have a slight feel of being tail heavy, yet it isn't.

I am not pleased with the way it flies compared to my other planes. The least little bit of elevator seems overkill on it and seems you need to over correct. Hope that makes sense and you guys have some ideas. I was wondering if the engine angles had something to do with this. If so, that would be worth its weight in gold because that would be an easy fix.

ahicks

My Feedback: (2)

Without down thrust, this wing (or any other semi symmetric or flat bottom wing), the faster it goes, the more lift it produces. Down thrust works exactly the opposite. The faster it goes, the more lift is canceled out. If the 2 forces are balanced, you get a neutral plane? One whose elevator trim needs don't change with changing air speed?

A plane that wants to turn (tuck) towards the gear on knife edge is not unusual at all. Kinda like having to hold some down when the plane is inverted? Regarding holding some down while inverted, a lot of guys like that. Gives them a sense of direction?

I think both are related to CG. A plane doing both the gear tuck and needing down while inverted are probably slightly nose heavy. You can confirm by doing the 45 degree inverted climb out. If the plane falls out of that quickly it's nose heavy. If it increase that 45 degrees to something steeper, it's tail heavy. Whether or not to change it, and how much, are going to be determined by your flying ability. I wouldn't mess with it unless you're pretty comfortable in the air. If that's the case, 1/2" back is what I'm using, and I've heard others here are doing the same.

The elevator is pretty sensitive on this plane. Do you have it at the suggested throws mentioned in the manual? 35% expo works pretty well for me.

landeck

My Feedback: (1)

On my two Revolver 70s I have not had any pitch sensitivity to speed. It holds the same elevator trim at all speeds. You may have a little less down thrust built into the firewall or with your larger engine you are covering a wider speed range than I do.

Bruce

ahicks

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Thanks Bruce, I was wondering about that, what others flying this plane might be experiencing. Was hoping for some feed back! What are you using for power? Propeller pitch?
-Al

microdon2

My Feedback: (47)

ahicks = I like your suggestion about the washers. My current Rev 70 has an OS 120 4s and I've noticed it does pull up slightly on WOT, probably for the reason you cite. I might just try that. Though it'll through out of whack my perfectly centered spinner! (unless I move the cowl..)

Was flying my Rev 70 yesterday as a guest at a new (for me) club - Floyd Bennet Field in Brooklyn. Pretty cool setup - they get to use 1,000 ft of one of the old runways (this airfield was a military base in WWI and WWII). This club is renowned for guys flying expensive jets, and giant-scale planes. So I'm flying the Rev 70 - second flight - am at about 80 ft, pretty much over the runway, when suddenly the canopy flies off. It starts floating \ tumbling down, falling towards the pit area (where there were plenty of people). I and others shouted "heads up - falling piece!", and I landed the plane, no problem. A guy brought the cowl over to me - surprisingly little damage. I asked if it had hit anyone or anything and he said it didn't - bit of luck there!

Then I saw the problem - the two wooden "legs" that come down from the cowl and house the blind nuts has both pulled out of the cowl - they were still screwed into the plane. I had repaired this cowl from a previous crash and fabricated those two legs. Evidently the epoxy I used to hold them in wasn't strong enough. Go figure. Now I need to re-anchor them better.

Fortunately I had a second plane - my CG Sukhoi \ DLE 30 - so I could still fly.

btw - they still let me join their club!

lopflyers

My Feedback: (12)

Oh no, same thing happened to me with one of those wooden legs, it keep loosing up until I put a lot of epoxy in there. Now is uneven and a pain to screw. But it has not come off again.

You are lucky that they are not mad at you, both clubs that I fly from here has a rule against flying over the runway unless you are approaching for landing

Luchnia

My Feedback: (21)

I only have two planes out of my entire fleet that have any issues flying straight at pretty much any speed. There are minor issues with speed changes, but nothing big. The two that fly a tad odd for me, are my Twist and the other my Funtana X100.

The Twist does some odd stuff, but I have it over powered so I think that has a lot to do with it. The Funtana X100 pulls toward the gear doing a knife edge and does not fly to my liking. I did not assemble the Funtana. I bought it from someone else. It is balanced well so that is not the issue.

The rest of my planes fly extremely true. I was flying my Edge 540 30cc yesterday and I could fly that plane a thousand feet or more straight as an arrow - hands off the radio for the most part. Comparing the Funtana to the rest I am wondering if there is engine angle issue, or something about the plane itself, but she is sound as can be so I am not sure what is up.

ahicks

My Feedback: (2)

I had a Funtana with a 26cc RCGF for quite a while. Not the best flying plane I ever owned either. Still had a blast with it. I think the other scale 3D types (Extra, Yak, Slick, etc) are much better, but the best I've flown for pure horsing around fun to date has to be a gas powered profile I have. I've scattered balsa bits with this 67" OMP Fusion twice now during the 2 seasons I've been flying it. So fun I keep putting it back together! Getting pretty brave with it, so it's days are likely numbered. Mojo will replace it when that happens.

This Revolver is still coming around. Learning more about each time I fly it. Doubt it will ever peg the fun scale meter like a profile might, but the meter climbs a little more each time out? I bought it as a "go to" plane. It's already serving that purpose as well as I ever expected it to! -Al

landeck

My Feedback: (1)

I had a Magnum 91 four stoke in the first Revolver and an OS 95V four stroke in the current one. The Magnum flew the plane well but the OS provides much more power.

Bruce

ahicks

My Feedback: (2)

So it sounds like you may be right. With the engines you've used/are using, the firewall is set properly, leaving you with the correct amount of down thrust, so you wouldn't notice the issue. When you go with more power, more down thrust is required to stay neutral. Makes perfect sense. Thanks, -Al

wilinfla

My Feedback: (5)

I just got my Revolver today, this thread is going go take me a long time to read tough! I plan to electrify the Revolver as my first electric plane. I am impressed so far with the plane and I am looking forward to getting it in the air.

Will

Sbach342Guy

I thought elevator input was required to maintain level flight in pretty much any throttle position other than mid throttle? I've always been told to trim for level flight at mid throttle. Anything above mid throttle should cause your plane to gradually rise. Anything below mid throttle should cause the plane to slowly lose altitude.

lopflyers

My Feedback: (12)

Ditto

Luchnia

My Feedback: (21)

This was my thought as well and just about everyone I know that flies RC, even the large scale guys say the same. I always trimmed my planes out for mid throttle level flight and not on windy days because I would have to re-trim anyway. The Rev 70 that I had was smooth as silk with the 91FX on the front for power. Never an issue with hands off flight around mid throttle.

What I found was that some planes require more elevator input than others as far as level flight at different speeds. Some will fly through most of the envelope without much stick movement while others just won't do it. I was thinking that the characteristics of the plane. What plane does not usually climb slightly when you add throttle thus increasing speed except for maybe a few designs? I would think a pattern plane would have the best chance of straight flight at different speeds because of its streamlined design.

Some of you experts throw some extra meat on this plate so we can tell if our planes are not set up right

BTW, I want another Rev 70, but I am not paying the price they are asking right now. If they have another special where I can lock it in around 200ish, then I am on board.