That ideal airframe
What is being sold these days seems to be driven by what the guys in the market want. Traditional models are tweaked to fit the fad. A good example of this is the 3D market.
While the plane resembles the original full scale the control surfaces make up a bigger percentage of the structure. Being this is the Scale aerobatics thread I thought I'd ask what a person should look for in a new plane to make me happy, and to insure it fits the criteria for SA and IMAC. Both J-Tech and Carden (and likely others) offer a "Competition" or "Pro" series. If your building there's no end to what can be done. Buying one in a box, well some things can be modified, but there would be creative limits. After seeing a Carden Pro and a Dalton I was impressed. What are the builders doing to get these planes fly like they do? One observation (other than pilot abilities) is that there appears to be a ratio of Fuselage to Wing ratio that is close to equal. At my stage of the game, putting all my eggs in one basket (tying up all my disposable income in one kit plane) probably isn't wise. ARFs are a less expensive way to experiment, and if you don't like it you sell it off. So here is the question, what things besides the airfoil to fuse ratio (if that is indeed an advantage) should a aspiring SA pilot look at in choosing a new plane? |
Re: That ideal airframe
Guess maybe a better question is, is one particular style of airframe better suited to any particular flying style?
ie. Someone that started on gliders, probably has a different approach to stick movement than a guy that cut his teeth going from glow to 3D gas..... |
Re: That ideal airframe
Imac = Smooth flowing routines, that resembles the "Full Scale" airplane maneuvers.
3D = Helicopter, Falling Leaf, Blenders, etc. etc. etc. Traditionally, long tail moments = smoother flying characteristics, scale ratio control surfaces in the larger airframes mimic the flight characteristics of a full scale plane. In a nutshell, look for airframes with regular sized control surfaces with decent relatively long tail moments. |
Re: That ideal airframe
So lets make the best of what I have!:itsok_170: I have a AeroWorks Extra 300 (86" WS) with 26 flights on it since I bought it used. It came with a DA50-R which has been sent in to DA for the up-grades its never had. The replacement engine is a DLE55.
It is balanced at 3 7/8" from the wing tip leading edge. It flies Ok with the CG and programming that I have set up for it on a DX8. The only thing that I've encountered issues with is tucking to the gear and a slight roll-out going in both directions knife-edge. Lets start fresh!:biggrin: I have a Hanger 9 Incidence and angle meter. Sadly the odd-ball battery (only available from Horizon) is running low again. So I built my own angle meter. Not ideal but functional, affordable and here!:) I believe I've found my roll-out issue. Different throws on elevator. Seeing I'm starting fresh, I have centered both the control surfaces (neutral servo and mechanical tuning of control arms) and gone neutral with my Tx trims. From past experience, I've discovered the old set-up needs a hair of up elevator trim to fly straight and level. When I roll it inverted on a 45* up-line I have to add just a titch of up elevator to maintain my course. Adjust CG or Not? My next question is what is the most common philosophy for Tx programming? The DX8 offers 3 position switches for each control surface OR flight modes. To date, I've never used a mix to correct bad habits from any plane. Mostly because until a few days ago I wasn't aware of the "Back Mixing" that makes a simple thing like mixing Rudder to Elevator so simple. :redface: All my questions may seem pretty rudimentary. In my defense, I am 120 miles away from any organized flying club that does more than polkin' holes in the sky!!! Most of what I know about Tx programming has been picked up on my own. What I've done up until this point is program the 3 control surface switches towards me for what I like for rates to land. These rates are close to what the manufacturer calls low rates. The middle position is ~1/2 way between the manufacturers low and high rates. Leaving the high at the manufacturers high rate. So please help me set up a plane properly for IMAC. I'll all ears. (Glad my parents didn't name me Dumbo seeing my baby pictures). |
Re: Make her all she can be!
2 Attachment(s)
Here is the simple angle meter I put together out of scrap laying around. The paper clips are moved to the center of the control surface for each rate, and can be measured by inserting a compass onto the arch.
Not real pretty but...... |
Re: That ideal airframe
Brent the best way to get things set up properly is to ask anyone who has a similar setup.
Trimming takes time but it sounds like you're on the right track. First comes CG, which most do a la Peter Goldsmith trimming article. That is, ( do all trimming with as little wind as possible) pull to a 45 up line , roll to inverted and see what she does. A slight pitch down after a while is ideal, while a pitch up means tail heavy ( or perfect if you fly 3D LOL). Next I do vertical up lines and see if I need right thrust. Then I do level rudder turns ( instead of knife edge) and see what mixes I need for a flat turn. Then I start to set throws for normal flight which is done at cruising speed. Then I do my snap conditions, spin conditions, roller conditions, down line mixing for IMAC. Now of course if you change props, servos, battery placement etc it affects everything :BangHead: The best thing is pick the brain of those you admire and use the best equipment you can afford and of course use what everyone else is using. They do it for a reason....why beat yourself up? :hammerhead: |
Re: That ideal airframe
LOL Thanks Lee! Well, I wiped out the old Tx programming and did a double reset on the Tx. Much to my surprise (which doesn't take much most days) I see I had rushed to set-up and fly this one too quickly!
The Left elevator linkage was out whack a mile. Both ailerons needed a slight tune-up. I must have tweaked the Tx to match them close (which wasn't too close) but she flew pretty well with minor trim adjustments.. I then went in and adjusted the travel to match up deflections of control surfaces. The next step was to adjust the control surfaces rates and expo to "Taste"! Using the manufacturers rates as a guideline. Past experience with this bugger tells me it was touchy on the elevator. All I can do now is wait for the breeze to subside to less than 35km/hr! The hunt is on for someone who has this twitchy, slippery plane! The plane I used in my IMAC baptism flies very differently, floaty. This is an experiment, a learning process and I am willing to take chances with this airframe.... its all grins and giggles until ya turf it, right?:biggrin: |
Re: That ideal airframe
Hey Brent.
It's worth every minute spent to do the setups you're working on right now. You can make the plane behave better than you ever thought, just by proper trimming, cg, and control setups. For programmable mixes, you'll probably find that you need: 2-5% up elevator with either direction rudder 1-3% opposite aileron with either direction rudder 1-3% down elevator at idle to straighten out your downlines. CG adjustment affects most of these, so get it set to your liking as the first step. As Lee mentioned, using Peter Goldsmith's trimming chart is excellent. Long, but really worth it. Don |
Re: That ideal airframe
:yes:Thanks Don, I've already saved Peter Goldsmith's trimming guide. Will digest it when I'm done spraying, seeing food isn't very appealing during spraying season!
EDIT: Got to ride a tractor for a little bit today, until I got rained out, again! Good place to reflect on things that are important! :biggrin: Anyway, I was thinking about the un-discovered potential that a Tx may have. As technology grows, I tend to hold fast to what has worked in the past. I'm a Dinosaur!!!:Rolloverlaughing: While I am aware of aileron differential, I don't have a clue about how or if it can be used to make a plane fly better. Or is Differential a "last resort" option, or is it something that every skilled pilot uses? EDIT 2: Thanks Don the answer is in Peter's trimming guide. And soooooo much more! :yes: |
Re: That ideal airframe
Brent:
The differential requirements can be checked by pulling to a 45 up-line and rolling several times in each direction. If the plane rolls like it is on rails, you probably don't need any differential. If it begins to spiral after a couple of rolls, differential may be needed. On one full roll during a sequence, it may not make a huge difference but it can definitely help. My Carden 260 (150cc) needs no differential where my Aeroworks 260 (100cc) definitely did. I'm not sure why but suspect it is the wing height location on the fuse. Another 2 cents worth (zero value these days) Brendan |
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