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A question of size

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Old 03-21-2003, 05:26 AM
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ilikeplanes
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Default A question of size

I've been flying what's usually called a 120 size scale aerobatic plane. It's a Goldberg Sukhoi (72" span 10.5 lb). It seemed huge when I was building it but still uses "conventional" R/C airplane construction and details. It seems about as big as you want to go with glow power.

I'm playing around with the idea of stepping up to the next size and using gas power. I would probably be looking at a 27% model with a 40cc engine. A Midwest Cap with a ZDZ40, for example. So, I have a few questions:
*Will I be able to tell the difference in flight characteristics between a 72" span and an 80" span model?
*Is an 80" model usually considered "giant scale"?
*How much new technique and equipment set-up will I have to learn?
*Is there a large price jump when going from something like the Goldberg Sukhoi to a Midwest Cap?
*Are redundant battery systems used in models of this size?
*Are dual servos used on elevator, rudder, and ailerons?
*Is an 80" model still OK for moderately sized fields?

Any other comments or words of encouragement (or warnings of reality) greatly appreciated.
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Old 03-21-2003, 03:19 PM
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Default A question of size

I have always been told size doesn't matter hehehe

Long morning without coffee...

It is giant scale, however by today's standard the small side.

Anyway the 80" will fly better than the 72" if built comparably well. You will see some increase in stability if kept light.

The techniques will be similar just more room to work with. You won't see the elaborate building techniques used until these planes start being built for competition. As light and strong as possible.

As far as engines go the gas engine will cost more up front, than you only pay the pump price for fuel plus oil..

Dual batteries are not necessary for a plane of this size. However a 1200mha minimum is something to think about. I also prefer 6.0v for this purpose. And possibly ignition battery and switch...

Dual servos on the ailerons and elevators, optional on rudder (good heavy duty will suffice)I have flown many 80" birds with s148 on the rudder, with out problem. However the more extreme requires the better servos.

As far a field that depends on the pilot and comfort level. If kept light depending on plane it will probably slow down enough, yet I haven't seen the field nor the pilot so its your call...
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Old 03-21-2003, 05:24 PM
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Default A question of size

My opinions from here on. Read into them what you will

When I started flying IMAC, I had a Goldberg Ultimate with a Saito 150 and standard type servos. That plane was a blast to fly and had TONS of power. However, it was difficult to fly through the Basic sequence and even more difficult to fly through Sportsman. I have since found out that with good servos, it would have been much better.

My second year I flew an Aeroworks 29% Edge in Sportsman with a BME 50 and good, digital servos. Wow, what a difference. The plane flew SO MUCH more smoothly and drew much better lines. I found myself not having to work as much to make things smooth.

Last year I flew a RadioCraft 35% Extra in Advanced with a DA-100 and the best servos I could buy. Again, a quantum leap in flying qualities. Slower, smoother, much more graceful and stable.

This year I have just finished a 40% Extra that I plan to fly in Advanced and then Unlimited. I have heard that I will see another quantum leap in performance. Can't wait to find out.

Having said all that, you will definitely notice a difference as the plane gets larger--assuming that you can outfit it with the appropriate servos. Since this message is in the IMAC forum, I am assuming that you will be flying precision aerobatics (or at least you are thinking about it!). If so, DON'T SKIMP ON THE SERVOS. You can't believe how much of a difference a good, coreless servo makes. Hitec makes some really good quality digitals that lots of guys are having good luck with. Go ahead and buy the 59xx series as these center very well and have great resolution and power. You will find yourself fighting the plane alot less. I don't have personal experience with them as I have up-to-now stuck with the trusty JR8411's.

It sounds like you don't mind building if you are considering the Midwest kits, but let me make a suggestion. I would seriously consider the Aeroworks 29% Edge with either the BME50 or the Taurus 3.2. This combination seems to fly much "bigger" than the Midwest offerings. You will only need 1 servo on each aileron and 1 on each elevator. You can easily make do with 1 high torque (Hitec 5945 or JR8411) on the rudder. I used a 1650 mAh NiMH pack (5 cells) on my Edge and I could easily get 5 flights on it. This pack should run you about $25. Put another one on the ignition. This plane/engine combination is great for IMAC sequence or for 3D. Gas will run you about $2 per gallon (after you add the small amount of oil) and you will be getting about 1 oz./min of flight time. So 5 gallons may last you all summer depending upon how much you fly.

You asked about the price jump, and honestly this depends upon the hardware/servo choices you make. The initial cost may be higher, but if you fly alot, you will save tons of $$ in fuel. And if the plane is well maintained, there is a good market for them when you choose to sell it.

Above all, have fun and don't be afraid to ask questions.

Ken
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Old 03-21-2003, 06:45 PM
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Default A question of size

Wow... I think Ken hit the nail on the head. Fantastic advice. I would only add that when considering that next airplane, do whatever possible to see it fly, or even better, fly it before you buy it. Everyone flys a little different, and everone likes/dislikes certain characteristics of each airplane.
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Old 03-21-2003, 07:40 PM
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ilikeplanes
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Default A question of size

So far so good. Here's some more info/questions. I do like building, and the Midwest kits seem to have a good reputation. As far as flying characteristics, I like straight tracking and clean snaps. I could sacrifice knife edge, tumbling, and 3D capability. At this point, I can simply not conceptualize anything larger than 80" and 40/50cc. Sorry.

Questions:
*Why would the elevator need more servo power than the rudder? My experience is exactly the opposite for non 3D flying.
*Is hand starting the norm for gassers?
*There are several 40/50cc engines available. The Fox sure looks good. Why doesn't it get more press?
*With 6 bolt prob hubs, how do you drill the prop?
*14-15 pound sure seems heavy for 1100-1200 sqin. Is this normal flying weight for 80" models?
*Is it advisable to run the radio and ignition off different packs (electrical isolation)?
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Old 03-21-2003, 09:50 PM
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Default Re: A question of size

I have had the CGB Sukhoi and the MW Extra. The sukhoi was glow and the Extra was gas. You will find that the flying and presentation is the same, the equipment is the same and I would recommend dual battery packs for the receiver for both. The big difference I experenced is that you have to conserve energy and present good on glow and the sukhoi. With the Extra and gas, you can fly an extremely quiet and slow routine and with the gas engine, you have the power to go verticle as strong as need be.

Originally posted by ilikeplanes
I've been flying what's usually called a 120 size scale aerobatic plane. It's a Goldberg Sukhoi (72" span 10.5 lb). It seemed huge when I was building it but still uses "conventional" R/C airplane construction and details. It seems about as big as you want to go with glow power.

I'm playing around with the idea of stepping up to the next size and using gas power. I would probably be looking at a 27% model with a 40cc engine. A Midwest Cap with a ZDZ40, for example. So, I have a few questions:
*Will I be able to tell the difference in flight characteristics between a 72" span and an 80" span model?
*Is an 80" model usually considered "giant scale"?
*How much new technique and equipment set-up will I have to learn?
*Is there a large price jump when going from something like the Goldberg Sukhoi to a Midwest Cap?
*Are redundant battery systems used in models of this size?
*Are dual servos used on elevator, rudder, and ailerons?
*Is an 80" model still OK for moderately sized fields?

Any other comments or words of encouragement (or warnings of reality) greatly appreciated.
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Old 03-21-2003, 10:27 PM
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Bill_Higgins
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Default A question of size

The 80" Midwest series is an excellent choice. My first competitive IMAC bird was a Midwest Cap 232 with a Moki 2.1. If I would have known what I know now about gas engines I would have used a different engine.

You will be able to feel differences each time you jump in scale.

"Giant Scale" as a standards term is usually associated with being "IMAA" legal which I believe is 80" for a monoplane. (someone correct me here If I'm wrong) but in other circles seems to be centered around the 40% birds.

The amount of "Technique" and setup you have to learn depends on how competitive you want to be.

It's been a while so I'm not sure on the price points.

I personally wouldn't go redundant on battery, but I would definitely use good servos and use a separate servo on each surface.

Sure.....You should be fine at fields with moderate size runways.
(250-350ft)

Bill Higgins
San Antonio, TX
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Old 03-23-2003, 03:30 PM
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Default A question of size

*Why would the elevator need more servo power than the rudder? My experience is exactly the opposite for non 3D flying.
Technically you dont, but if you use a single servo for the elevator, it has to be mounted in the fusealage with a long pushrod. With a larger size bird, this will flex while "pushing" the control surface, producing undesireable results. With two servos, you elimintate this because they are mounted very close to the control surface itself, and you can tune each elevator to be exactally the same as the other, for optimal performance.

*Is hand starting the norm for gassers?
Yes, although with the 50 cc class, and maybe some 80-100cc you can use a starter with about a 4-1 reduction pully assembly to acquire the appropriate torque to turn the motor.

*There are several 40/50cc engines available. The Fox sure looks good. Why doesn't it get more press?
The fox motor is fairly new, and fox is mainly known for their glow motors. I would definitely reccomend a BME 50, or a DA 50, I have run both and they are completely awesome! the bme is a little lighter than the DA but the DA produces tons more power!!

*With 6 bolt prob hubs, how do you drill the prop?
The motor company that you buy from usuially will sell you a prop jig to drill all the holes relatively perfectly. Desert Aircraft stocks one that works very well, but i am sure you can get them elsewhere as well.
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Old 03-23-2003, 05:11 PM
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ilikeplanes
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Default A question of size

Well, after giving it much consideration on this rainy weekend, I've decided that I'll stick with 72" glow models for now. The small step up to 80" gas models represents a doubling of cost. It just isn't worth that much cash to me at my personal stage in the hobby. After all, I do have a mortgage.

Now, if the "micro gas" engines (25-30cc) continue to develop, that is another story.

Thanks guys.
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Old 03-23-2003, 10:36 PM
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Default A question of size

Sell the house and buy a big plane..............


Ok, You can't really do that.

I have a Hanger 9 edge with an RCS 140 gas engine on it and it flies great, there are other planes out there of this size that you can use a small gasser on also.

I also have a Great planes extra (PW) with a BME 50. This plane is fantastic and will do anything you ask of it.
The price is not all that bad either.

Bill Higgins:
nice to see you here. Did you get to see my photos of the JR Challenge http://www.scaleaerobatics.com/jrchallenge2003/
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Old 03-25-2003, 02:32 PM
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Default A question of size

>> Bill Higgins:
>> nice to see you here. Did you get to see my photos of the JR >> Challenge http://www.scaleaerobatics.com/jrchallenge2003/

You bet, I drop by at least 2 or 3 times a day. Great Pics and Report. Look forward to seeing you guy's again next year.
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Old 04-02-2003, 12:51 PM
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Default A question of size

zenoah do a 26cc petrol engine which is ideal for the 70inch span aerobats. I dont know about us prices, but its around 200 in the uk which is comparable to some of the big glows. Then you immediately start saving in fuel costs.


Maybe thats your way forward until you feel the need to go bigger ?
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Old 06-15-2003, 12:03 AM
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Default A question of size

ilikeplanes, what did you go with?
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