Ron Daniels

A few years ago, I built a Tempest Mk V with bomb drops and retracts. In spite fo the fact that I mostly fly electrics, I went with a glow engine, due to the extra weight of the retracts and bomb drops.

2 years ago, I built a Sea Fury, with a brushless motor and some NiCd cells that had come on the market the fall before.

The Sea Fury is a rocket, with 0.88 HP propelling its 3.5 lbs, 10 x 8 @ 10000 RPM. The Tempest has about the same power, with a bit less efficiency, due to the smaller prop (I propped it for 15, 500 static - APC 9x5, to allow it to run at peak power, in the air).

The only time I have had engine problems with the Sea Fury was when I inadvertantly pulled a 10 cell pack off of the charger, right after starting to charge it (read, nearly completely discharged), put it in my 12 cell plane, and launched it. After 1 circuit of wondering why it was so sluggish, I landed it safely and, upon seeing the charged 12 cell pack sitting on my tool box, figured out the "mystery".

I took the Tempest to SMALL in Ottawa 2 weeks ago (5 hr drive), where I tried to fly it. After several attempts to get the engine running right (it is a very reliable, FX engine) I declared it "not field fixable", and took it home, where I discovered that the clunk line had severed where it attaches to the tube in the cap of the tank. I was lucky the engine quit on my take-off run, as there was not "friendly" off-field landing areas handy.

Now I am building another Sea Fury, which a friend will fly. It is using "this years" technology. He has supplied me with the latest motor, servos, and a Li Poly battery pack of 4200 mAh capacity.



This airplane will weigh 14.4 ounces less than mine. Considering mine weighs only 56 ounces, this is a HUGE savings. It will be very close to the same weight as a light glow set-up. The static thrust will be within 5% of the total all up weight, and the duration will be in excess of 15 minutes.

I could add back in retracts, bomb drops, and flaps, and still not be back up to the weight that I fly mine (with TONS of power) at.

The cost of this "newest technology" set-up is still about 30-40% more than a good 4-stroke set-up for the same plane, but when you add in the value of near perfect reliability, big, scale-like propellors, propellor noise only, and no glow fuels to damage your finish, this starts to look like a good value.

15 and 20 lb scale planes are now flying 15 minute flights with similar set-ups (albeit at fairly high initial costs).

Chris True was flying a big 4 HP A-10 on electric at Mid-Am this year. This thing flew for more than 10 minutes, had flaps and retracts, and let out a jet roar while accelerating to flying speed in about 50'. It was spectacular!

I wonder how much longer until electric becomes the way to go for scale airplanes, even those that are considered "high performance".

Any thoughts??


Ron Daniels

LA7flier

My Feedback: (1)

I'm starting construction of a 99 inch Don Smith P-61 twin for Scale Masters comp and am in the process of figuring out which electric setup I need. I've spoken with Larry at SR at lengh and bought his ECalc program. 24 cells per side. Still haven't determined motors or props...it will weigh between 20 and 25 pounds

Ron Daniels

I have been waiting for several months to get seriously interested in Lithium Polymer, as I can fly 8 minutes on NiCDs, and no LiPoly pack that could handle my current requirements (up to 45A continous) offered a significant weight savings, in my 10 cell airplanes. I could use large 8000 mAh ones, but didn't want a 20 minute duration, and it wasn't worth the cost or added care required during charging. Now that I can save 7 ounces on a 42 ounce plane (my Super Chipmunk) that already goes vertical, I am getting very interested in Li-Polys.

However, on the larger planes, which require "shipping containers" worth of cells, LiPoly has been very popular since it came on the scene, due to the MASSIVE weight savings avialable.

The Hacker C-50 Acro motor is popular among the guys flying the really big stuff right now. Jason Shulman used it to get 7th in the World Pattern Championships. He may be a good starting point to learn more about this motor.

It is a very powerful motor, that is generally used to swing a 20" propellor hard enough to pull a 10 pound pattern plane straight up indefinitely, but still have enough pitch speed to pull the plane along at 80+ MPH.

The battery pack used for this is a 10 S 4 P Lithium Polymer. What this means is 10 of the 3.7 volt cells in series to provide 37 volts nominal, and then 4 of these "sticks" in parallel to handle the 50-60 A of peak current. These packs, while quite pricey, weigh about half of what a NiCd pack big enough to put out the same power would be very much heavier, and would give less than half of the capacity. Durations for hard aerobatics are in the 15 minute range , and for 17 lb 3-D type airplanes (much less pitch speed - therfore lower current draw), 20+ minutes of 3-D flying can be done on a single charge.

With this year's new high output cells, if you kept the peak current down to the 45 A range (on your twin, at 37 volts, this is a total of 4.5 HP, at about 85%-90 efficiency, not at theoretical number at a peak RPM that the engine is not running at), you can go with a 2P configuration and save even more weight. 4.5 hp on a 20 lb scale ship is plenty!

For example, the new Thunder-Power 2100's (see Hobby-Lobby, Mike Hines is using this pack personally at this level) are being used up to 45 A continuous in a 2 P configuration. For your airplane, each pack would weigh 957g, and have a capacity of 4200 mAh. 24 sub C's with a capacity of 2400 mAh would weigh about 1440 g each, and need to run at about 69.5 A to put out the same level of power. This computes to a run time of 22% as long as the Li-Poly option.

With a total weight savings of 2.1 lbs on battery alone, you could use this weight to add significant scale detail. Remember, you can save a lot of weight in your nacelles as well, as you do not have to deal with the power pulses of a reciprocating, high RPM engine.

Depending on the pitch speed you need, you may be also be able to run scale-sized 4-bladed props in flight. No more switching props for display and flying.

Another person to talk to about the Hacker/Lipoly combination would be Dave Grife. He has this in some of his larger scale planes, and gets stunning performance and duration.

Here is an example of a Hacker set-up that is being used in a Gee Bee (with thanks to the person who originally posted this on Ken Myers' web site).

Motor Hacker C 50-14XL 6.7:1
Speed Controller Hacker Master 77-3p opto
Batteries Thunder Power 3p9s
Propeller APC 20x13E
Amps 48
Flying weight 12.5 lbs.
Wing area 743 sq. in.
Wing loading 39 oz. / sq. ft.

Note that it is 3.7 V less than a 10s set-up. Note also the size of the prop being used.



Ron Daniels

Edwin

My Feedback: (2)

Right now, I only have a mild interest in electrics. How many flights can one get out of a giant scale warbird? Recharge time, and type of charger! I used to play with smaller park flyer sized planes that were fun at first but got boring after awhile. When I fly, I tend to do a bunch of flights for the day, about 5 or 6 minimum. Seems like I would need a bunch of battery packs at (high $$$) to satisfy my flying fix. Is this true? My current passion is giant scale warbirds fully decked out in the 28 to 35 lb range.
Edwin

Ron Daniels

Edwin,

I fly 45" fighters that take 10-12 cell packs of between 1700 and 2400 mAh.

I got in 14 flights on the Friday of the Mid America E-fly-in.

As for getting bored, my Chipmunk can do 500 foot vertical 8's, and I have to throttle it back to fly in formation with a .91 4-stroke powered Goldberg Chipmunk. My Sea Fury has done loops in excess of 400'. I flew the Super Chipmuk with an on-board altimeter to get a feel for exactly how high and fast it will go. Peak climb 5300 fpm, pull-up from ground level, at full throttle goes to at least 570 feet. Vertical unlimited if I go back 1 1/2 inches in pitch. There is a link to a video of some electrics in flight on my web site. These are NOT park-fliers....

For your size, with Li-poly's, you would need to charge for 1 hr before flying for 20 minutes or so. This is currently the maximum charge rate for LiPoly's. Depending on how hard you run the battery packs, and how well you cool them on board, and while resting, you would need to cool the packs up to 1/2 hr or so, before charging again. You do not want to exceed a pack temperature of 140º F or so.

If you had 2 packs, you could have one 15+ minute flight every hour.

With NiCd's, you can charge at higher rates (I generally run mine to charge in about 20 minutes), but your flights will be shorter, and wing loading higher. You still need to cool them off between flying and charging, unless you are not running them hard.

The big gas engines are still more economical, and probably the best for turn-around time between flights. But, if you live in a densely populated area (we are a sattilite city to Toronto, and have over 500 000 people in our tri-city area), the noise can cause issues.

There is no doubt that a 35 lb fighter as electric is still an expensive proposition, compared to a gasoline engine, but I don't think that there are many technical short-comings to such a project, anymore.

In my size (45" range) electric has been practical for several years. Over the last couple of years, I have seen tremendous growth in size and performance in the "common" airplanes seen at electric meets.


Ron Daniels

LA7flier

My Feedback: (1)

Wow, Ron. I'm impressed. You appear to really know your stuff. Far more knowledge than I currently possess. I'll run your thoughts through the ecalc program and let you know what it predicts...total wing area is something like 1100 sq inchess and I love the props you suggest. One thing I have heard about the LiPolys is their tendancy to explode requiring careful handling.

Ron Daniels

Hence the cautions about charging no more quickly than 1 hr, and keeping the pack temperature below 140F.


Ron

Edwin

My Feedback: (2)

I think I would like to build a small camera platform in the 40" range for electric. I have a small credit card sized camera that would work nicely and I could fly it in my backyard. This, at the very least, can keep a foot in the electric door for the future. Something like a cub or champ. It would at least keep some interest in it. At this point I only have infrastructure for smaller battery bricks. But should work.
Edwin

Heavy Date

Electric modeling has really come a long way in the last few years. I remember the old Kyosho electric zero from the late 80s. Not a bad flying plane, but the flight times were pretty awful.
I have seen a few newer electric conversions and it is amazing! I saw a GP Lancair doing touch and goes for at least 15 minutes and looked to have plenty of power left.

There is only one thing missing, sound. To me it just is not the same as an IC engine. Maybe Ram will come out with a sound board with recordings of Merlins or big Pratt radials. Now that would be the ticket!
Hans

bosssman

My Feedback: (35)

I have to agree 100 percent with Hans on this one - after getting back into the hobby after being out for some time, I am AMAZED at the advancement in engine technology in the ability to "replicate" the sound of the real thing and its ability to swing scale appearing props DURING flight. Still, to some, the sound won't be an issue. In my car hobby, there is NOTHING like the sound of well built V8 American motor, while others these days love the sound of a 4 cylinder Honda motor taching at high rpm. As has been shown, there is room for EVERYONE in this hobby and I am sure as advancements are made in the electric motor arena, so will people that love scale planes WITHOUT the fuss and mess of an IC powerplant find their place.....

randy

dottney

My Feedback: (2)

Guys take a look at the discussion areas in Ezonemag.com. This whole thing is electric. Large stuff is being flown with electrics all the time. LiPo technology is still maturing. I personally still fly NiMh & NiCad. The Lipos are still a bit pricey and a bit fragile. I'm flying a 54" Ziroli design P47 on 10 Nimh cells just as well as it flew on an old OS .50 2 stroke. I sold my last "wet" powered plane a couple weeks ago and am totally electric now. Large stuff is definitely in my sights.
BTW there's a whole section here on the universe about glow to electric conversions.
Dave

CorsairJock

My Feedback: (90)

A quiet revolution is in the making. LiPo batteries will allow one to convert ANY warbird to electric power, while weighing no more than it's fuel powered counterpart, have the same available power, and being able to fly for 15 minutes or more on a charge. The down side (besides the expense of batteries) is than you cannot fly it again and again on the same day. Perhaps a few times a day, several hours apart.
While lacking engine noise, it would be much easier to hear simulated machine gun sounds (such as available from RAM).
There have been other breakthroughs, such as affordable brushless motors, but LiPo batteries are the giant leap that electric powered aircraft needed to allow them to catch up to fuel power.
LiPo battery technology is relatively new, they will only get better and less expensive as time passes.

Jim Finn

My Feedback: (2)

In many aircraft the sound heard on the ground is from the prop. (Espicially commercial acft.) Electric powered models replicate this a LOT better than do the IC powered ones.

JAkridge

I have a nephew in AZ that sold all of his glow stuff over a year ago to go elec power. He has all the trick stuff.
And paid dearly for it !!!! He has tryed to push me for a month or two to give elec. a try.
I just finished a 54" twin profile plane and he has went wild to try to make it elec. 5.5 lbs with glows in it.

In the year alone that he has made the switch newer and better elec. equipment has come out, and more on the way.
He has some wild 3D planes. All Sweet Flyer's...........

For Now...I need the smells and sounds of my gas / glow stuff in my Warbirds.......But I'll keep my eye on this elec. stuff.

Uncle Heinkel

With all due respect to electric guys, I'll switch when an electric motor sounds like a four stroke engine.

H.

CorsairJock

My Feedback: (90)

This year (2004), our club moved to a new flying site. It is at a grass runway airport, surrounded by farmland. Several small planes (Cessnas, etc.) fly from it. The nearest house is about 1000 feet behind (as in, we don't fly in that direction) our flight line, there are no houses in front of our flight line for about a mile. There is an active train track track about 2000 feet in front of our flight line.
And yet, we are getting complaints about noise.
This is why electrics are so popular in Europe: too difficult to find a flying site where people won't complain.
I also love the sound of 4 strokes, even tho they don't sound anything like a P&W R2800.

Edwin

My Feedback: (2)

When I was a kid, we used to stick poker cards in the spokes of bicyles to try and sound like a motorcycle. <g> naah! Still wouldnt sound right.
Edwin

Kmot

My Feedback: (24)

I have yet to hear an electric motor that sounds as satisfying as an IC engine.

Ron Daniels

I have to admit, I also love the sound of a 4-stroke.

My favourite 4 stroke sound is the sound of my old pre-Surpass OS .40. It has the exact same output as my 10 cell brushless electrics (11 x 8 at 8300-8500 RPM), but does sound better at 1/2 throttle. It is also quiet enough that it it difficult to hear, if there is a lawn mower nearby.

I last had it in a 41" Hawker Typhoon (fully enclosed in cowl, exhaust and all!).

In terms of sound, I'd rank my 4-stroke Typhoon first, my electric Tempest 2nd, and my .25 FX Tempest Mk V 3rd. As nice as the FX sounds at 15 500 RPM, it does not sound like a fighter.

I have not used my .40 4 stroke in 3 years. I haven't used my .48 Surpass in 7 years. As much as I like the sound, I can't be bothered to make a fuel-proof airplane for it, and haul out all of the glow support equipment to the field. Once you get used to not cleaning your airplanes, you get a little spoiled....

When I can hear my electrics, the big 11" props make a satisfying sound. You can hear the difference in sound when the prop is "digging" in climb, or when you are doing snapping or tumbling manuevers. Diving produces some very scale-like sounds at times. The big 20" props make some very, very cool prop noise on the bigger electrics.

I don't mind the sound of a big 50-100 CC gassie running at 6000RPM, but muffling one of those to a level that does not give non-R/C people cause for complaint is often difficult to do, without destroying the scale illusion with a large, external muffler.


Ron Daniels

nekked_man_2000

I still have questions about longevity. I've been playing with speed 400 stuff for a couple of years, and have had several battery packs stop performing in that time period...I have a Goldberg Cub with a Saito 50 on it that I now fly only ocasionally, but used to fly it regularly, it has had many many gallons of fuel run through it in the last 10+ years I've been flying it, and now sometimes I might not fly it for a year...in that time I've had receiver NiCads go bad in it...Will any electric setup last this long? I have nothing against electrics, I dabble, but it'll be a long time before I give up my gas. And, I have a gearbox that almost sounds like an old engine growling around up there!

skier

Make sure you cycle the NiCads every once in a while. They will last longer and be much happier if you do.

rcmiket

Has anyone have any info on pricing the switch a warbird of any real size to electric? From what I've seen and read this is a costly switch. All the electrics on the market now are under powered ( to keep the price down) so wahts the story?-Thanks Mike

Ron Daniels

The life span of NiCDs can very greatly depending on their construction, your usage and the cooling they get.

If you use a type of NiCD that is not a "rapid discharge" type cell in a high current, quick charge application, you will not get a lot of cycles before it is "pooched". If you get, say 8000 RPM with a high current type cell, and you try a freshly charged cell (assume same cell count) of another type, and get less than 7500 RPM, or so, this can be an indication of the resistance in the second type of cell being higher at the currents you want to run. Don't use the second type of cell. Chances are, it will heat up, and give you a short life, on top of lowering your performance.

For my 45" warbirds, you can get a used Astro 05 G in excellent condition, a 40 A speed control (new) and a 10 x CP 1700 pack all for about $130-$150. This is comparable to the cost of a .30 4-stroke, and it will swing an 11 x 10 APC-E prop at about 7200-7400 RPM.

For about $270, you can go with an AXI 2820-10 brushless, with 40 or 45 A controller, an the same battery pack. You will pick up about 1-2 minutes of flight and another 6-800 RPM.

Up in the 60" size, the price goes up, but used Astro brushed motors are still quite viable, provided you know how much thrust you need and how much pitch speed you need before you start. The Aveox virtual test stand is a good, public use, tool for estimating thrust and pitch speed from prop and RPM. You can adjust the cell count and motor type to get your prop spinning where you want it. The output wattage can also be read from the results. If it is within the range of the motor you plan to use, multiply by about 1 1/4 for Astro Cobalt brushed, and by about 1 1/5 for a AXI-type brushless to determine your estimated input watts. Divide this by 1V/cell to determine your estimated current.

You can take your glow prop and RPM and put it in first to determine the output wattage of your glow set-up to see how it compares. Remember, though, 400 w through a 12" prop on a 60 MPH airplane is going to be more efficient than 400 W through a 9 " prop on the same airplane.



Ron Daniels

nekked_man_2000

I raced remote control cars in the late '80's, got about 3 years out of the average NiCd pack, using them every weekend at about 2 to 3 charges on each pack a night. That was fast charge with a low tech charger using a digital volt ohm meter to watch for the peak myself...worked really well, as long as you didn't forget to keep an eye on them. Currently for the speed 400 stuff, I'm running 2 8cell 1100 mah HeCell NiMh packs, rotating them, using a peak detecting charger. For what I wanted to do, flying close to the house in open fields on ocassion, this works pretty well. I have probably 30 flights each on these packs, and have had one of them for probably close to a year, and so far no problems. My dad bought two of these packs at the same time, and one of his has gone bad...2 cells of it anyway. I could fly these planes just as well with a Norvell for about the same price as one battery pack...for a very long time without using much fuel, but I do like playing with the electric stuff...but that's what I still consider it, playing. For me to get serious about it, the cost would go way up to get equal performance to the I.C. motors, but I enjoy sometimes just taking the plane and transmitter, two charged battery packs..no mess, be back home in time for dinner.

I hope I don't come off wrong, I'm not putting down electric stuff, a lot of it is very impressive. It's just not for me right now....who knows about the future?

Ron Daniels

Hi Nekked Man,

I agree, for equal performance, electric is still more expensive.

However, the fact that equal performance can now be achieved shows how much electric power systems have matured in the past few years.

Park-fliers certainly have some appeal to them. You get to fly without needing a large field, and, if they are electric, very few people who live near the park get concerned about them from a noise point of view. You do want to pick an empty park, as you can run into some safety issues if kids are around, because models are a "kid magnet".

I just bought an new motor from Hobby Lobby. AXI 4130-14(higher RPM/cell thant 4130-20). I think I'm going to use it to swing a 16 x 14 at about 7000 RPM. It may go into my 61.5" Hawker Typhoon to begin with, and then larger stuff later on. It has enough power to fly a plane as large as a Senior Telemaster, if I run it on 24 cells, with about a 1.5:1 belt drive. I'm pretty excited about this motor.

My Super Chipmunk is my current favourite plane. I ROG's off of grass at 1/2 throttle, does up to 400' loops, does amazing snaps and tumbles, and goes for 6-8 minutes. I very much enjoy my fighters, but I did not build them with a good hand-hold for self-hand launching, so I need a helper. One is not always available.

With the big AXI, I will be able to build fighters large enough to ROG (grass) with retracts, and full functions. I will still have the fantastic reliablility of the electrics, the "warning" of fuel low (power decreases before you run out completely - some of my glow engines run great right until....out of fuel), and the ability to fly right up until the time I leave the field. When you don't have to clean, you don't need to budget time for that step.

I've also heard a rumour that my club has received a noise complaint. If so, a move towards quiet electric planes may help extend the "life" or our field.

If you guys want to know more about the big AXI, I can post my findings here when I start testing it a bit later in the fall. I need to clean out my work-shop before I do any testing. This thing will blow stuff everywhere!!



Ron Daniels