Just read Windy's artical .90 size engines, I suppose horse power is a good thing,  but .90? Man that's a big motor...Any comments?

I've watched Windy work with the ROJett .90.....very, very impressive....not only for big and heavy aeroplanes (most hold that there is no fixing a porker), but on many ".60 size" ships as well....effortless power....

Who knows Steve
There was a time when .35 engines were the norm. Then along came the .46 size motors, many many 1970's designs...and then the ST .60 came along, then pipes and 4 strokes..and so on and so on, so now .90
Man Big Motor!!

My comment: Man, dats a big motor

Is this the same "really famous" Dennis Adamisin of Hawker Typhoon fame that won Advanced when I was a small child-huh is it? Really?

Uuuuuuuuuuhhhhh . . . . he's compensating for something?     

Here goes;

  Simple question-----Will someone tell me at what point we no longer need the airplane.  There was a thread about
Speed Stunt" awhile back, this sounds like it.

  "Billy G"   

I am of the belief that the rules in the USA must reflect those of the FAI...otherwise those that chose to compete at the World level from the US are at a disadvantage.....

The FAI seems to be a French deal, and seems to go along in an orbit all its own....they say that .90's are okay....

I kinda like my PA .65, and plan to use them for a while....but that is MY preference.....

No one says that a competitor HAS to fly a .90......

Dennis!!!!!!!

Great to see you here. I hope that you will become active again in stunt.

Keith, you are too kind - me MODEST???  You must not remember me real well!!!  I know that I have reached the age where the older I get the better I WAS!!!  BTW I absolultely love the Gulfhawk!  Strange, a couple weeks ago I was thinking about a long-time ago helping some guy with an Martin MB5 Scale model...

Tom - Thanks for the kind welcome too.  As for making a "comeback" that could be trouble.  I just found my old white pants and the only place they fit now is as a HEADBAND!


OK, back to the topic.  Why settle for a 90?  OS advertises that their 120AX is about the same size as a 90.  Saito builds a 180 4-stroke in a slightly taller 120 size case.  I have an (RC) os FT-160 twin, same size as a FT-120.  It would fit PERFECT in a Formula 1 inspired stunter with the nice cheek cowls - like a Keith Trostle Eagle.

Only a wimp would settle for a puny old 90!!!

Getting back to reality, I am thinking about some Nostalgia projects for a Fox 35, and some BIG projects for an LA40...

Bill....mayhaps I missed something in reading Winfred's piece, but I think that the point that he was trying to make is that a bigger engine/more power is more easily "dialed in" to suit the flyer's needs....

His example is a great one: when he entered the 4-stroke Seafire at the Nationals, it was powered by a (heavy!) Saito .90....the AMA rules at the time allowed a 50% displacement advantage.......Windy built an I beamer that had throttle control as well..... a lot of stuff into the airframe...and still the dry weight was 60 ounces.....

People have truied for years to pull a porky design around with bigger engines, and although notably heavy planes have done well, it probably says more for the pilot's ability that for the airframe's ability to perform with added power.

A Giesekie (sp?) Nobler flew well with Fox .35 power....the same airplane flew better with a Tiger .46, and even better with a modern powerplant like an AT .36 or RO Jett .40.....more predictable power.

 

Even though the FAI, and  subsequently the AMA, have allowed the engine displacement to grow to .90 (or is it .91??) that does not mena that anyone MUST use that big an engine.  There have been many who are saying that the airframes will grow to big to look good in our "hemisphere" we fly in if there is a wholesale run for the "biggest engine".

I can see where a larger amount of "USABLE" power can be of benefit even in a lightly loaded plane.  If the larger displacement doesn't add too much weigth to the airframe, then it can be a benefit.

Contrary to Mr. Paul Smith's assumptions that ever thing pertains to "MONEY", it could simply be a matter as simple as doing away with the "formulas" for 4 strokes vs. 2 strokes.  .91 4 strokes were already legal when the "overall" change took place!

In the end, it hasn't appreciably changed the event at all, so far.  And I do not see a trend towards creating giant aircraft to use for CLPA.

Bill <><

Dennis;

  Thank-you for an answer that I agree with 100%. Now when this Dang Magazine decides to arrive I will be able to read it with at least some understanding. Rest assured I will be back with more questions when I am armed with more info. It is kind of hard to ask a resonable question when you lack at least a basic knowledge of what you are talking about.  See you soon.

  "Billy G"   

Rich;

  I can't go to deep here, again because of lack of knowledge. I wiil see if I understand what you are saying by using this analogy. If I buy a stereo with a lot of wattage (power) I don't buy it to see how loud I can play it I buy it to hear the low end clearer. Now that means that you have the power of that engine but you don't necessarilly use it all. In the case of the stereo the power is needed in the case of the engine it is not so why use it. I hope this makes some kind of sense. I really need to see the article to make any more sense out of this.

 "Billy G"   

There are only 2 ways to get more power in a internal combustion engine.

1. RPM
2. Bigger Bang

We all know that rpm is not necessarily the best for stunt
So a bigger bang is the logical choice. You can get a bigger bang by forced induction (super charging or turbo charging) or using a bigger combustion volume (Bore and stroke)

A bigger engine produces more power at a given rpm than a smaller engine. A smaler engine can produce as much power but it has to spin faster. Again as RPM is not desireable for stunt the larger engine seems the logical choice.

In our application though you have to apply a law of diminishing returns. If we were able to get model engines that could spin a 13 or 14 inch prop steadily at 8000 or lower rpm and still put out sufficient power then we would be set. But even a 91 engine is manufactured to produce it's peak power at over 10,000. when you start reducing the running RPM you fall out of the comfort range of the engine. It becomes ineficient and many times starts behaving inconsistantly.

Say you have an engine that produces 1.2 hp at 12,500 rpm as designed. Run that engine rich and drop the rpm the engine may only put out .60 hp and will not be particlarly happy running at that speed. A bigger engine will produce more power at a lower rpm but if it is not running at it's design rpm then it still will not perform consistantly. This is the reason your car has a multi spped transmission. So the engine rpm can remain within it's operating rpm to be able to pull the load of the car. This operating range is called the power band of the engine. Full scale aircraft have variable pitch props. Plus in full scale aircraft the throttle is rarely touched once airborn and cruising speed is attained.

People can experiment with larger and larger engines but IMHO the returns will end up not worth the effort and expense, there still will compromises to be made, in addition the the larger tank, extra fuel and added weight of the power plant. So to have an engine running at the ideal RPM for stunt and able to swing a large prop at the engines comfortable operating RPM you are going to need a big engine to do it as RPM generrated power is a no go. I figure that engine will have to be bigger than a .91. So far tuned pipes are the best answer for getting power out of a smaller engine at the proper RPM. Even there the engine is really operating out of it's design range but the pipe makes up alot to offset this.

Having discussed the present use of tuned pipes in CLPA with Randy Smith (he knows a little bit about it ), Billy Werwage, and Bob Hunt, the pipe is no longer being used as a "booster", at least not in the .51 and up size engines.  It is set up to act more as a governor.  That is paraphrasing several good conversations.  A PA .61 will make all the power (and then a whole lot more) than is needed to fly my present PAMPA plane (660-670 sq.s at about 55oz.), but it can run in a solid, dependable, 4 stroke, and the pipe is set to keep it from speeding up when coming downhill, etc..  Now I do not know how Paul sets up his OS 40 VFs!  From experience, i do know the 40 VF has a different type run from the bigger PAs, the only other piped engines I have used.

I will be the first one to say that I do not claim to be any kind of expert, but I do know that it flies much better set up this way in wind and turbulence than it did with a piped .40, or even the PA 51.  Now, Bob Lampione won the '69 NATS with his foam wing Sabre, a somewhat smaller plane running a Fox 35 yet weighing close to the same as my .61 piped plane.  But he used a ST 46 when he built his new Sabre and he claims it flew much better. (oh yeah, I think he added an extra inch of span to each wing panel!)

There is something about this that I cannot explain easily, but more power available, as long as it doesn't mess up the balance of the plane, makes the plane fly better.  It does mean that you have to prop the plane correctly, but that is always the case, no matter what the set up is.  It is still a "balancing act" where everything must work together!

And yes, a Belchfire .91 will not make a Walker Trophy winner out of a porker, but it might make it flyable. 

I'm with Dennis, though, I would just get rid of the plane and start over instead of trying to "just make it fly good"!

Dear Friends,

when discussing big motors, it might be interesting to consider one more issue; Noise.

With too wany fields having been lost, time has come for the control line community to take noise reduction really serious. Noise limits, like them or not, will be established and/or tightened. Therefore, the main reason why the F2B Workgroup has suggested to legalize bigger motors was to allow compensation of power loss due to more efficient mufflers.

Kind regards,
Peter D. Germann
FAI F2 Subcommittee Member
F2B Workgroup Coordinator

To allow larger engines to overcome losses caused by mufflers is circular reasoning at best. (Larger engine needs more muffler hence more power loss, hence larger motor and so on and so on)

Actually a well designed muffler does not need to impact power and in the case of a tuned pipe / muffler can enhance power at a certain rpm and still be effective in quiieting the engine. Anone who has put together a mouse (Moose) can muffler knows this. The deal is that well designed mufflers tend to be unsightly, not necessarily heavy nor power robbing. I think when faces with a choice between a unsightly efficient and quiet muffler and one that is restrictive  but is able to be hidden away or be asthetically pleasing. I think the latter is chosen most often, so by taking cosmetics over effective design is the root cause ofr the excuse that it is to overcome power losses due to mufflers.

Mufflers are not really high on the CLPA priority list. If as much time was spent in developing quiet high performance mufflers as has gone into tuned pipes I figure a very effective solution could be found.

Thank you Randy, Your post said basically what I was going to try and say. It's a valid point that's, up until now, has been overlooked.

I'll add a few of my own observations based on my, some what limited experience, that I hope to soon increase.

My flying buddy Jim Rhoades has been flying a Russian Arf, Really more than an ARf, since the worlds last summer. It's powered with a Discovery Retro engine, .61 sized. The engine is designed to run slow, with lots of torque at the speed it's designed to run. A very pleasant, simple to achieve run, in the classic 4-2-4 break, but it resists windup, by design.

All my recent stunters have been Stalker powered, because of the similar, though not identical, style runs. So when Walter Hicks showed me the first look at his Stalker .81 at the Golden State stunt meet, last year, I knew I would be following his experiences with a lot of interest.

He finally posted that he was running it on the bench, and it turned a 14 X 6 at 7800 max. It looked to me that this was going to be a low speed grunter engine. I figured that it would run very similar to the Discovery Retro, so I ordered one. I haven't yet run mine, too much time out of town working, but I'm looking forward to it. I figure it'll drive my next stunter in a similar manner as a piped ship, as far as constant speed goes, without the pipe, and use a more easily available, and cheaper prop. I also figure, that since I'm not an engine guy, it'll be easier for me to get good reliable runs from this setup.

I'll never need all the horsepower that could be squeezed out of a large bore, but, won't have to worry about it because the engine isn't designed for horsepower, rather it's designed for torque.

It, if it's anything like the other engines from Stalker, should be quiet, have decent run time on a reasonable amount of FAI fuel. And haul my plane through the maneuvers without much effort.

A good, reliable, engine run is more than half the battle when it comes to stunt competition.

Hi Peter, it's been a while since I've seen your name to a post. Going back to the old days when you hosted your own site.

I tend to agree that we're talking two different sides of the same issue. While I can agree with your most recent post on several levels, I do believe that you might want to consider the difference between engine designs that require higher speed and depend on that speed for horsepower and torque. Running at higher speeds, the bigger bangs will indeed be harder to muffle.

The Russian designed engines, like the Discovery Retro, and the Stalkers develop their power, torque, at lower RPM's. Prop noise is the major sound being created when I'm flying. I would get the same prop noise from an electric, possibly more, if the RPM is higher with the electric. Yes, I still get more noise than an electric, considering that I am using an IC engine, but most who watch my flight, are impressed with how quiet my plane is.

Actually, size of the plane is becoming less of an issue as we march on. Most designs for PA 65's are in the 650 or so sq inch range. A .35 sized design from the Classic era, would be anywhere from 530 to 610 sq inches. A lot of the best pilots seem to be going full circle and returning to smaller designs for several reasons. Some of the reasons is that smaller planes seem to fit the pattern better, not pull your arm off, and can be built lighter.

Also, larger designs can look hurried in the pattern. There are many reasons to consider smaller planes.

You may be right about presentation between larger and smaller designs though.

I can agree that electrics may well be the future, and that isn't going to be all bad.

Seeing the 90 fly at GSCB at the end of last summer puts a different slant on this. The 90 puttered around in a deep four-stroke, never breaking lean. Rich Oliver continued to make the point that it allowed the old oil soaked plane (still a good flying plane) to fly slow. Something like 5.8 second laps. (Maybe Rich Peabody remembers more accurately.) The plane went over in the wingover and all maneuvers for that matter at a powerful stately pace.   The pull on the lines constant, predictable, but not excessive.

OK I'm Back;

  Nope I haven't read the article yet but I don't need it to comment on the last reply. No everyone dosen't need a big engine, and at the same time NO you don't need it to be competitive. You put a smaller plane with a smaller engine in the hands of a capable flier and he is just as competitive as anyone. He has just as much chance of winning.

 I don't believe and certainly don't agree that the person who is using the big engine is doing so only because he has money to throw away. He is doing it for other reasons(I need the article to comment further here)?

 As for the rules and ruling bodies that allow these engines, thats another topic not to be discussed here.

 I have followed this thread very closely because the idea of using these large power plants intrigues me. I will continue to follow it very closely. The article has been promised to me very shortly, it seems I was lost on the mailing list. No biggie I shall return armed to the teeth. Until then have fun and keep your back to the wind.

 "Billy G"   

A Saito 91 weighs in at about 1.2 lbs, from the bottom of the engine bearer it is 3.8 inches high. So it does not take a math wiz to figure out that plenty of weight (or tail length) will be required to bring the CG into range. And you need to have around 4.25 inch fuse depth to hide the engine to get that front row plane.

Now I do not know about you but those numbers start suggesting a rather large airframe to haul that engine around. I would offer Rabes new plane that everyone here seems to go Ga Ga over. Consider that the engine is completely enclosed in the cowling. That means the inner diameter of the cowl has to be at minimum 8 inches in diameter and even larger outer diameter. That is the size of a personal pizza at pizza hut. That needless to say makes AL's plane Big. Big enough to either require a take apart design (complicated) or a SUV to haul around. Now I do not know what the gas prices are in your neck of the woods but round here it is up at $2.92 a gallon. So having to own or buy a SUV just to get your airplane from point A to point B gets very expensive.

My second point has it's roots in "Psychology of a stunt pilot" thread. How long is it before the top fliers start using big motors in big airplanes and the time when judges start being conditioned and expect winning formulas to include only large engines n large airplanes. As these Big airplanes present so much more differently in the circle when compared to your 35, 40 powered plane how can it be even remotely be expected of a judge to be able to accurately score say a small airplane after seeing 5 or 6 large designs fly back to back. The presentation will be different enough to make the flight of the smaller aircraft look wrong.

Add to that the other rather unique American belief that bigger is better. This has deep psychological roots to all sorts of man made objects (Cars, Motorcycles, Aircraft, Swimming Pools, Houses, you name it). No sooner that reliable engines started to be made the CLPA guys that had the money started upping the size of these airplanes. Many moved to RC where you had to have pretty deep pockets to participate so the plane size explosion started there first.

Back in the day before the SUV even those who had deep pockets had two choices to get their plane from point A to point B. Station Wagon, Van. Now one thing Americans value more than anyting is their choice in cars. To participate in RC with Big planes you had to decide what kind of car you would have to buy. Station wagons were not cool, Vans even less so. So in a way that helped keep the size of the planes down except for the occasional person who did not care what car they drove over the ability to bring a really huge RC plane to the Field.

And since cost was a factor most CL guys had more planes VS really big planes also they were more likely to be tradesmen so they already had Vans or Station wagons and they would load them up with a half dozen planes or more to haul to the Field. Then along came the SUV and the mass media played on the American belief that bigger is better and sold a ton of them, each model bigger than the next. At one point one out of every four car sales was an SUV. All of a sudden you had a car big enough to get your Big stunters to the Field and still arrive in masculine style.Big plane, Big Car, the male ego out in full parade. The appearance of Giant Scale, Larger 3D RC planes directly coincided with the increasing popularity and proliferation of the SUV. You did not have to put up with the embarrassment of showing up at the Field in a old Station Wagon (long since unpopular that they are scarcely made) or Yikes! even more wussy a Mini Van.

No you do not need a big plane with a big motor, but the price to get to the top levels of CLPA has risen enormously, it can not be denied. No it is not on par with the cost of entry to be in the top 5 at say NASCAR or other motor sport, but to be competitive at the top levels of CLPA has become not unlike those other motorsports except in on way you do not get sponsor money. The cost to the individual in time, equipment, and travel makes it waaaay to expensive for most participants in CLPA. So at those levels you had better be able to keep up dollar for dollar with the other guys or don't even bother. Is it a wonder why there is such a resistance to change in this activity? One just has to consider $60.00 propellers $400 engines etc. So it is not surprising one bit when in other threads people suggest making a masters class or Pro's class etc just for the fliers who want to participate in that end of the activity. Or start making displacement classes in CLPA. You know 29-40, 45-60 61-75 Unlimited of course this like just about every like wise suggestion has always been shot down, (Interestingly usually by the same people every time) So I am not suggesting it just using it to highlight a point.

I close my argument with the following observation, In a post above it is mentioned that these monster motors are being used in Pattern Master, SV 11 and similar airplanes. Just think about that comment. Those are already belong to the larger group of CLPA models. The Pattern Master can not be considered compact. And it is just going up from there. These days the pattern master is at the smaller size end in CLPA competition and is even being quoted as being the norm. That type of psychology is what will ever prevent anyone who competes with the big boys incapable of winning at the highest levels no matter how well they perform. Without the 91 sized plane and subsequent monetary investment he does not stand a chance.

Is this why some say they have been stuck in advanced for years? I wonder, is it really that their skills are not good enough or is it that they can not afford the cost of moving up?

I've got big engines and small engines.  Right now, my interest is in applying the overpowered principal to more modest size planes.  In other words, what happens when you put a light 40 with good power to weight(PA 40 Ultra lite, or a Brodak 40) into a smaller plane.  Applying some of Al Rabe's principles and it looks like a 400-450 sq.in. plane, weighing in the 35-40 oz. range, might work quite well.  It will have a similar power to weight of a 90 powered 65-75 oz. plane, similar wing loading so it should handle wind about the same.  The only thing I can see is it may require a bit more span to keep down the drag in maneuvers.

I did not say anything about the UNIT PRICES of these things.  The issue is the VOLUME consumed.

I started building a 60-sized Magnum stunter, and it's quite obvious that it's going to cost more than twice the cost of a typical 35-40 size airplane.   If I go ahead and finish it, it'll still be a "1/2A" compared to the 91-powered behemoths that are impending. 

On the plus side, they'll give the electrics a well-deserved thumping.

My bad.  I thought we were seriously discussing the cost of building a modern PAMPA plane!

Bigger engines are NOT easier to run, IMHO.  This is especially true of the 2 cycle engines.

"With great power comes great responsibility"

In other words, you only need so much HP to fly an airplane of a given weight and drag , the rest is just reserve, the more reserve the more trouble you can get into.

The 4 strokes take to being "choked down" better than a 2 cycle, also.  A 2 cycle is a very heat critical animal.  Choke down a big 2 cycle motor, it has trouble staying lit.  This forces the need to run bigger props, which creates more GP, blah blah blah...  Unless the bigger engine is just gutless, then the added displacement does nothing.

On the bigger 4 cycles it was possible to venturi down the engine and get a smaller engine "like" response.  It did not find this to be true on the larger 2 cycle engines.  So much is put into the "SOUND" of a 4-2 run....

All this being said, I really look forward to someone proving me wrong!!!  I think the increased engine displacement rule is GREAT!!!