Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
April 28, 2017, 02:02:55 PM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: [1]   Go Down
Print
Author Topic: engine size versus wingspan  (Read 307 times)
0 Members and 1 Guest are viewing this topic.
ksn3n3
Bronze Member
***

Kudos: 0
Offline Offline

United States United States

Posts: 33

Topic starter


Ignore
« on: November 25, 2016, 12:52:22 PM »

I'm getting ready to order some plans to build a few models for some vintage engines that I have and wondering what are some good rules of thumb for engine size versus wingspan for C/L Scale.  I realize thats a bit of a loaded question amd very subjective.  Im looking for a scale model that flies at 'scale' looking speeds., i.e not so underpowered that it is staggering around the circle, and npt so overpowered that I can do all acrobatics in the book.  Something inbetween. Im looking to use a McCoy.35, Supertiger .36, and K&B .40 and building several biplanes and also a monoplane if that makes any difference.  Looking on line at both kits and plans engine sizes seem to be all over the place and inconclusive.  Any thoughts appreciated.
Logged
packardpursuit
Gold Member
*****

Kudos: 32
Offline Offline

United States United States

Posts: 723




Ignore
« Reply #1 on: January 15, 2017, 12:18:19 PM »

I think you have tumbled to one of the real unappreciated false perceptions faced by modelers. That is the ASSUMPTION that there is or must be a correlation of engine size to wingspan! It is a pervasive rule of thumb that has been widely promoted, but is patently false.

It goes directly to how we perceive an aircraft model's (real aircraft too!) size. Simplistically we refere to it's wing span as it's "size" but that soon runs into stark and often conflicting physical realities. For example a Monocoupe 90a and Beechcraft model 17 are two classics aircraft of the 1930s. They share  the exact same span(32 ft) but the latter is so much  larger in every other way. If you were modeling both, in same scale, their structure and power requirements would be quite different. A situation existing the full size counterparts, for the exact same reasons.
 
Logged
ghostler
Silver Member
****

Kudos: 6
Offline Offline

United States United States

Posts: 175




Ignore
« Reply #2 on: January 16, 2017, 09:38:16 AM »

ksn3n3, if you really want to know, if I were you, I'd get a simpler profile and fly it first. That will give you an idea of what you really want. The McCoy .35 Red Head works fine on the profile 42" (1067mm) wingspan 400 in2 (25.8 dm2) wing area Sterling Kit S-1 Ringmaster and similarly proportioned Top Flite Flite Streak. Fly on 60' (18m) lines. Adding 12 oz. to a pint of Castor oil to a gallon of standard 5% - 15% nitro RC fuel will up oil sufficiently to properly lubricate and protect these older engines. Running on a rich 4 cycle breaking into 2 cycle in stunts will give you roughly 5 second laps on 10x5, 10x6 props, which is decent for all the stunts but not too fast or slow, which is what you want. 3 to 4 oz. tank (RC clunk tanks are okay) will give you 4 to 5 minutes flight time.

Then, you will have an idea of what size plane you want based on your experience. Otherwise, it is all academic. The more modern .20 to .25 Schneurle ported engines are roughly the power equivalent to the McCoy .35. Hence this may cause some confusion in engines recommended for a particular plane.

http://www.clstunt.com/ (Stuka Stunt), http://stunthanger.com/ (Stunt Hangar), http://www.brotherhoodofthering.info/ (Brotherhood of the Ring) are a few control line forums where you can get additional inputs. Good luck.
Logged

George Hostler
Clovis, NM, US
TimWescott
Gold Member
*****

Kudos: 11
Offline Offline

United States United States

Posts: 844



Ignore
« Reply #3 on: January 16, 2017, 01:32:19 PM »

It goes directly to how we perceive an aircraft model's (real aircraft too!) size. Simplistically we refere to it's wing span as it's "size" but that soon runs into stark and often conflicting physical realities. For example a Monocoupe 90a and Beechcraft model 17 are two classics aircraft of the 1930s. They share  the exact same span(32 ft) but the latter is so much  larger in every other way. If you were modeling both, in same scale, their structure and power requirements would be quite different. A situation existing the full size counterparts, for the exact same reasons.

That goes for the real airplanes, too -- they both had radials, but the one in the Beechcraft was a honkin' big one compared to the one in the Monocoupe.
Logged
TimWescott
Gold Member
*****

Kudos: 11
Offline Offline

United States United States

Posts: 844



Ignore
« Reply #4 on: January 16, 2017, 01:42:00 PM »

Without making a huge set of rules involving weight, span, area, draggy bits (struts, wires, etc.) and whatnot, I don't think there's a good way to do this.

One thing you CAN do is to look for build articles for similar planes.  I.e., all monoplane warbirds are going to be about the same, a Piper Cub and a Taylorcraft are going to be about the same, one between-wars fighter biplane is like another, etc.  So if you want to do a Dewoitine D.500 (which is one of the planes that fascinate me) then you can figure that it's going to fly an awfully lot like a Spit only with some extra drag, and go from there.

Model design (and full-scale design, for that matter) really falls into having a "works every time" formula that always generates the same basic plane, shamelessly copying someone else's engineering while just changing the aesthetics, or doing some complete experiment and going through numerous revisions before you hit a successful combination.  Since there's a lot of similar airplanes out there, there's a lot of opportunities to find stuff to borrow.

(And please, please, don't make a 48" span Piper Cub with a 40 in it.  A Cub should not fly like a P-51).
Logged
LOUCRANE
Bronze Member
***

Kudos: 5
Offline Offline

United States United States

Posts: 32



Ignore
« Reply #5 on: January 24, 2017, 07:35:12 PM »

ksn3n3 (did I get that right?)

Most modern (and older) engines used for scale flying have throttles. That alone offsets the "ultimate power" problem: you can throttle back if you go so fast you are uncomfortable. As mentioned above, "realism in flight" is a factor if you are being judged.

A "Piper Cub" type model should look slower than a Spitfire of Mustang. And vice versa.

Scale models, in my opinion, should be heavier than stunt or other sport types. When you slow them down, you need more Angle of Attack (nose high flying attitude.) A typically over-powered CL model doesn't do that, nor does it land at reduced throttle. "Realism" again...

Too much power, as I said, is not really a problem if you can throttle back. Too little IS a definite problem; if you get into a bind punching throttle may help you recover.

I have other ideas about "realism" for CL scale models... Flying 'flat' in a circle that would require significant bank for a "real" airplane? Hmmm... The associated skills and abilities needed in CL Scale flying are charm enough - the other stuff is secondary. (IMO.)
Logged

/LOU
packardpursuit
Gold Member
*****

Kudos: 32
Offline Offline

United States United States

Posts: 723




Ignore
« Reply #6 on: January 27, 2017, 12:29:57 PM »

"charm enough"
I like that!

IMHO- biggest detriment in CL scale flight is generally too much speed for the prototype modeled. Lighter wing loadings allow for slower and SAFER speeds, however,  CL scale designs and plans are not known for promoting lighter wing loadings. Simply throttling back an overloaded airframe is not always practical, either  aerodynamically or esthetically.

 I think it telling that the traditional view of over coming too heavy a model is to simply add more power. Something the model engine industry has promoted  and gladly provided, for years.

Speaking of industry, How many of us old timers still think  .049 power is adequately serviced with a model airframe in 16"-18" wingspan range? Outfits like Scientific pretty much drummed that into our collective consciousness. Never mind it is simply not specifically true. I tend to think the 18"span norm stems more from the fact  half a stock sheet of 1/8" or 1/4" x 3" balsa is 18".
Logged
packardpursuit
Gold Member
*****

Kudos: 32
Offline Offline

United States United States

Posts: 723




Ignore
« Reply #7 on: February 05, 2017, 11:34:38 AM »

I've always thought, If its enough power for RC it's about right for CL Scale. I seem to recall a couple of VK 1/6 RC scale WWI kits being flown as CL scale and using .60's for power. Personally, I think a good .40 in a VK Nieuport   COULD BE an excellent match, on 60 ft lines.
Logged
ghostler
Silver Member
****

Kudos: 6
Offline Offline

United States United States

Posts: 175




Ignore
« Reply #8 on: February 05, 2017, 07:14:19 PM »

Back in the 1950's, there were a number of free flights that were also for control line. The 30" (760mm) Goldberg Ranger 30 cabin used a Cox .020 Pee Wee for FF and .049 Babe Bee or Golden Bee for CL. http://www.outerzone.co.uk/plan_details.asp?ID=3830 You'll see photos of my Ranger 30 there as an FF. Berkeley scale kits had dual or triple designations, too. Some of those later became the Sig Craftsman series.

On all these in general, the engines used for CL were smaller than normally we are accustom to. There is a drawback, which is wind penetration. Calm weather permitting they did fine.

Regarding Scientific standardizing 18" (460mm) as the standard wing span, a half sheet of 36" balsa, in the 1950's and 1960's, kits were very cost competitive. These kits were sold in the thousands then. The market targeted school age boys. Older boys nearing adulthood and adults of course would opt for the larger and more expensive aircraft. The stand-off scale full fuselage looks of the Scientifics, with real decals and clear windows and canopies were very appealing. I was very excited when I got a Scientific Hellcat for my 11th Birthday. Kits then were under a couple bucks each. Also, you must remember that many of these kits were designed prior to the Cox more power .049 engines. The less powerful .049 OK Cubs are shown on many Scientific 1/2-A CL's.

Back then, there wasn't the stigma of a noisy unmuffled small engine in a school or public park like there is now. It started IMO shortly after the Vietnam War. People prior looked at it as healthy noise and that a child was occupied and staying out of trouble.

The RTF CL's IMO are also responsible for standardizing the 18" to 21" wingspans.

Although a novelty, personally I'm not into the so called scale flight speeds in control line. If I see a Fairchild Ranger cabin doing 5 second laps on 60 foot lines, even engaging a loop or inverted flight, I think it amazing and enjoyable. Control line is different enough that the fact it flies and flies well is enough to suit me.
Logged

George Hostler
Clovis, NM, US
Pages: [1]   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!