Discussion Sticky: FAQ/Advice/Help with getting started

[jsnaphook]

WELCOME!

Thinking about getting into the world of high performance airplanes? You've clicked on the right thread. The goal here is to have one place to read through to get answers to frequently asked questions about how to get started and which airplanes are suitable for your needs. Are you going to fly purely for fun/sport, or are you thinking about working your way up to competition? How much money are you willing to spend? Answer these questions and others can provide you with useful information, advice, suggestions/recommendations to hopefully get you pointed in the right direction.

Have fun.

Juan
Thread starter, not an expert

[MDreamer]

Hi,
In F5B style planes which servor is best for elevator, flaps, aileron?

Maayan Dreamer

[jsnaphook]

Hi MD,
Sometimes what's "best" is what will physically fit in your frame that is strong and light, still gets the job done. The overall "best servo" may not work, so you go with the next best. These servos work well for me.

Elevator: HS-65MG
Ailerons: HS-85MG, HS-125

Juan

[Andy W]

I am not a fan of MG on high-performance models. Metal gears wear and develop slop, which leads to flutter.
..a

[Masterpiece]

Originally Posted by jsnaphook

Hi MD,
Sometimes what's "best" is what will physically fit in your frame that is strong and light, still gets the job done. The overall "best servo" may not work, so you go with the next best. These servos work well for me.

Elevator: HS-65MG
Ailerons: HS-85MG, HS-125

Juan

I'm a big fan of the HS-65's BUT usually in the HB gearing. As Andy said, metal gears will wear and so I prefer the Karbonite gears. The 65's centre real nicely too (so far). I have heard mixed feelings about the HS-125, BUT I like them .

[Giz]

I think you need to ask the mod to make this a sticky.

[MikeAnderson]

Thought that an article I wrote for our Model Aeronautics Association of Canada (MAAC) magazine last April, would fit rather nicely here:

Extreme Electric Flight

Mike Anderson©

In July 1987, Keith Shaw proposed a few new rules of thumb for electric flight in his Electric Sport Scale article published in Model Builder magazine. For sport aerobatics you needed 40 to 60 watts per pound from the battery and you’d need 70 to 100 W/lb for "good" aerobatics. In the electric flight world of 1987, the best motors were DC (brushed) with cobalt magnets and could deliver 75% of the battery’s power to the prop. Big, high current batteries were 1750 mAh NiCd cells that get you a 3 and a half-minute flight at 30 amps. Now fast-forward twenty years.

The latest generation of LiPoly batteries are rated to deliver 50C currents for short bursts of 3 to 5 seconds and with capacities around 5000 mAh, that means 250 amps to the motor. The latest AC (brushless) motors can deliver 90% to 95% of that power to the prop. Nowhere do these two facts work best together than at the extreme performance end of electric flight; F5B, AKA racing gliders.

Visit the FAI website (www.fai.org/aeromodelling) and you’ll soon discover that F5B competition rewards planes, pilots and equipment that climb the fastest and fly the fastest. Pilots fly laps between pylons with the motor off, but need extreme power to climb to height again to re-enter the course. They can make no more than 10 climbs in 200 seconds to about 400 to 600 feet altitude and they want to be going FAST when they enter the course, snap off their motors and fold their props in tight for a gliding speed run. When that’s all over they climb one last time to glide before making a spot landing exactly ten minutes later.

Wings and tails are hollow-moulded in composite structures of carbon fibre, kevlar & fibreglass, producing a thin, tough wing that can slice through the air like a Samurai sword. Fuselages are moulded in different combinations of the same materials. An empty airframe weight of 650 grams would be considered heavy.

At the last F5B world championships held summer 2006 in Pitesti, Czech Republic, world class F5Bers were pulling over 250 to 300 amps for 3 second bursts out of 16 NiMH cells that were delivering power in the 500 W/lb range. Climb rates were close to 10,000 feet per minute and velocity entering the course would be in the 130 to 150 MPH range. Many teams showed up with dozens of 16 cell packs, many with the intention of flying the pack once then trashing it, knowing that the abuse of a single flight would render them useless for further competition. Several competitors simply pushed too hard and had packs either venting or popping cells in flight. Speed controllers were overheating and planes were seen trailing smoke.

At this level of competition, F5B has become the Grand Prix of aeromodelling sport. The FAI will be considering rule changes to reduce the competitive pursuit of power-at-any-cost, by installing a watt-minute limiter on every plane. In its simplest terms they are fixing the size of the gas tank. You can burn all your watts at once, or pace yourself over the eleven climbs. The result is expected to be power levels that don’t cause catastrophic equipment failures that can lead to personal injuries or property damage.

The FAI is also considering allowing LiPoly batteries. In the Fall of 2006, LiPoly battery cells started hitting the market with incredibly low internal resistance – the 5000 mAh, 50C, 250 amp types. Low internal resistance means voltage stays high under 50C loads and less internal heat is generated. These batteries will deliver high amps without overheating, weigh half as much as the 16 cell NiMH packs and deliver better climb rates because of the weight reductions.

At about the same time, motors have been coming out, specifically design for this event, that don’t even reach their peak efficiency of 94% until they are pulling 190 amps! Their efficiency doesn’t drop off much even at 250 amps. The challenge is to prop the motor to keep below the 60,000 rpm limit and keep the current in the 200 to 250 amp range, otherwise you’re not making the best use of the motor.
Speed controller development hasn’t been standing still either. Castle Creations offered an ‘experimental’ 300A ESC in January 07 and were sold out in days.

Combine these developments and we will be looking at planes flying at 700 watts per pound this summer. They will climb at 11,000 feet per minute, have almost 5:1 thrust-to-weight ratios and reach 150-mph motor-on velocities then gently land at slow speeds. Motors & batteries won’t be dangerously hot and participants & spectators alike will be safer. Welcome to the new world of extreme electric flight.

[flying evader]

just reading it made me feel like go flying!

Very nicely written. Kuddos on your writing skills.

Interesting approach on the servos. So you guys are using karbonite instead of MG?

if MG eventually wear out, what's the lifespan?

I've always used MG.

[Andy W]

They don't "wear out", they wear - and develop slop, which can lead to flutter at high speeds. Honestly, I find MG to have more slop to begin with - they have to be manufactured with some play to allow them to mesh, whereas nylon have a little "give" to them. I've not used the new HB's in high performance applications myself..
..a

[glucoseboy]

I think karbonite is the way to go for this application. I've used HS-65HBs on my Trex 450 helicopter and found them to be strong and very precise. The only downside is that I have stripped servo gears on crashes. HS-65MG are a favorite among Trex owners because they resist crash-induced strips.

Somehow, I think if you crash a hotliner, whether or not your servo gears survive is probably way down on the list of repair items. Besides, changing servo gears is pretty simple.

[gp125racer]

OK, Im looking at getting into some performance flight strictly for fun right now.

Ive order my stevens aero adrealine rush that Im going to gear with a gws 3900kv inrunner or a medusa 5300kv inrunner. I consider this platform something in which I can get used to a little more speed than which I am now.

What would you all consider a good entry level plane that allows growth into more speed etc? Ive had my eye on the slipso400 as I love its looks and it seems to perform very well.

Im looking to spend approx $350 including motor, esc, servos, receiver, and plane (kit, arf, etc)

I appreciate any feedback you can provide. Ive been reading the threads for a few days now, its incredible how fast these planes can really move out.

gp125racer

[jsnaphook]

Originally Posted by Giz

I think you need to ask the mod to make this a sticky.

I figured I had to do something in addition to just starting a thread. If someone can point me in that direction, I'll make it happen.

Juan

[jsnaphook]

Good point on servos with metal gears. I guess I haven't flown my airplanes enough to have some wear and develop slop. I'll replace them as soon as they don't function to my liking.

Juan

[defendedbear]

How big a difference between digital servo's or analog. Are the digitals worth the extra money. Do they center better, act faster?

[glucoseboy]

Originally Posted by defendedbear

How big a difference between digital servo's or analog. Are the digitals worth the extra money. Do they center better, act faster?

In general, digital servos are quicker and produce more torque than their analog counterparts. However, that is a general rule, you need to check the specs on the individual servos to really whether a particular digital servo is faster/stronger than a particular analog servo.

Also, note that the increased speed/torque that digital servos bring comes at the price of higher current draw. Most ESC's built-in BECs cannot provide enough current to drive 4 digital servos.