Doug,

I have never been a Top Fiver like you, but I now have almost two years' experience with my RO-Jett 76 engines (and I also have a PA 75 to balance things out).

I originally built my Alouette for the piped 65 engines, then switched when I got comfortable with the big engine. I was always concerned because I built it with a longer tail moment than "normal". For a while, I thought I had made a mistake and would have to do some major corrective surgery in order to get a decent turn.

Then all of a sudden, I got the hang of the design and now love the longer tail. It really seemed to smooth out the whole pattern. FWIW, my tail moment is 18.125" hinge to hinge. My wing area is 690 squares, the TVC is 26 percent, and the plane flies at 65 ounces.

My new one will have the same basic design, but I am using Howard Rush's landing gear and will move the gear to the fuselage. I had to create longer landing gear to clear the big props and used 5/32" wire. This is a little heavy out on the wings and I want to eliminate as much rolling weight as possible.

Hope this helps and I hope to see you back at the Nats in 2007.

Ron

I think new power can both rejuvenate old designs, and maybe lead to some larger modern ones than currently in vogue.

I watched Derek Barry fly a Sweeper he and his dad built that was 93 ounces with a pa-65 side exhaust.  The motor pulled the plane superbly in both winter and summer conditions, and Derek said he would be confortable competing with it anywhere, that it flew very, very good. Being 27 and in good shape the lension and stick forces didn't bother him.   Behemouths like Patternmasters, etc might have levels of performance heretofore undiscovered from the days of ST-60s.  There are the arguments of excessive dynamic loads on the pilot trying to muscle that handle, but some guys might not mind and in fact prefer threshold of pain levels of line tension.  Further, some people may wish to adapt the size of some of the really big 70s/80s ships and apply them to todays numbers just to see what happens.  Imagine an 800 sq SV series plane.....how would it fly?   Its cool just to have the available power to find out!

Phil,

When Al moved from his 60 sized classic plane to his current crop of stunters they have grown quite a bit.  I have flown his BBQB/BBFB and it is a vary large model/  While the wng is still small in some circles the overall size and weight is quite a bit larger than your typical 60-65 sized stunter.

His newest Mustang is larger by long way.

I think he is already ahead of teh game and he doesnt even compete.

I am looking into what you were talking about with longer tail moments using smaller stabs.

Matching the control movement to the tail moment may be a theoretical consideration but I haven't found many practical problems.  I went from a 23 in. moment(cg to hinge) one one plane to 26 in. with no real problems.  The both used similar sized stab/elevators.  There were minor differences in how the planes trimmed out, but the tail moment had little effect.  In fact, the longer moment plane uses slightly less elevator travel, probably because it is balanced slightly farther back.  The longer tail moment, along with a smaller, higher aspect wing, does seem to be less likely to overcontrol in hard corners, but both planes can be trimmed to fly well by adjusting the line spacing.

The issue of larger engines "spawning" new designs has long been answered. The planes that were using ST 46's are long gone and the 60\70 designs have been in vogue for a long time.

As to the 70 size engines making a significant difference in design, I don't think so because, the difference between a ST 61 Hemi and a PA 65 and a Merlin 75 is not as great as the difference between an ST 46 and a ST 61 hemi. In short, this "round" of power increase is incremental as opposed to monumental.

Case in point, Dave Fitzgerald went up to a 75 Merlin by simply retrofitting the motor in an existing Stargazer and went on to place 2nd at the 2006 Worlds with it. As to the issue of the 90's, here what I think the delio is; the 90's can easily take significantly larger airplanes and still fly competitively.

The problem, as Al Rabe and Windy Urtnowski found out, is you start to reach the point of diminishing returns. In short, you have to hang on to the friggin thing. It appears as if you start to reach a point in which the mass and the resulting physics associated with it starts to impair one's ability to accurately place a plane in space.

The BIG difference as I and other flyers have found out, is the difference in design between a 2 stroke of ANY TYPE and a four stroke. For me, and apparently other flyers, THAT was THEE proverbial "big can of worms" from a design point. A lot of cats no longer roll with the 4 banger. I am still working on designs for the Saito 72 which is a whole other can of worms than the 56 still. Designing for the big block is a pain, but man, the power-oh the power-lol. I hate Gen Saito for corrupting me like this. He turned a good man bad.

Behemouths like Patternmasters, etc might have levels of performance heretofore undiscovered from the days of ST-60s.

Hi Steve,

I thnk you are very correct in that statement.  Trimming the line tension to suit the pilot, and having the qualities of an engine that can haul the mail in any conditions on a Patternmaster size airframe is IMHO the direction many will take to make use of the tractor pull engines like the PA 75 and RoJett 76.

Kent tysor had his test bed ARF Strega out recently.  That plane, on the first flight, got pulled through the bad air of W-S Hobby Park like it wasn't wvn there.   And he missed the needle making it fly WAY SLOW!   He could still fly the pattern with out having to nurse too much.

I thnk you are very correct in that statement.  Trimming the line tension to suit the pilot, and having the qualities of an engine that can haul the mail in any conditions on a Patternmaster size airframe is IMHO the direction many will take to make use of the tractor pull engines like the PA 75 and RoJett 76.

This cracks me up.  I remember when the big planes were said to be "too cramped" in the circle.  So, everyone went smaller.

I have been flying with the ST60 the last few times out.  Power is not an issue in stunt.  We generally use 1/2 the power available with any engine.  There are a dozen or so engines out there that will pull a stunt plane through a pattern at the highest levels in the worst conditions.

BTW, the ST 60 is right there with most everything I have flown.   Not quite the brute of a PA 75 or Saito 72, but generally easier to fly accurately with a very smooth response curve.  Any improvement over this 30 year old engine is marginal.

The bigger engines were supposed to be more quiet.  This has certainly not materialized, at least not in 2 strokes.  From what I can see ,the bigger engines are LOUDER.

Too much power does not improve the pattern.  I am sure of that for myself now.  It just gives more room for error not less.

HI Brad,

Glad I can "crack you up"!  Everyone needs a good laugh every now and then.

Also, everyone has their own "opinion", which I stated as being so.  So, in your opinion, we don't need any excess "usuable power" in our planes.  Hmmmm.... seems to go against every one that I talk with about that.  Hunt, Werwage, Gieseke, Fitz, Windy, Al Rabe, et.al., seem to have said that some extra power is quite good.  Al even made a point for me to use a PA 61 instead of a PA 51 in my Classic Mustang I build.  I'm sure the 51 would have flown it just fine, so why was he insistant that I use the 61?  More power.

The ST 60 being a match for a PA 75, in stunt use?  No way.  Plain and simple.  The PA 75 has more grunt whether on a pipe or on a muffler.  And it's as easy to run, maybe even easier if you do what Randy says.

This event is great because there are so many different preferences in how we do things.  The way you do it, I do it, or anyone else may well work, but it all comes down to what we prefer.

I have not seen the problems of installing a larger stunt engine in an airplane except for balance issues.  Taming the power is simply a prop choice, usually.  My first experience in seeing this was Tom Dixon's T-Bird II with a ST G51.  Tom can fly pretty good, so that might not have been the best example, but the plane didn't care where the wind was blowing at all at the Huntersville site where the air can be really bad.

BTW: my reference to what "Many" will use is in no way a reference to what the World Champion class fliers may or may not do.  Just the rank and file stunt flier who wants to fly the PM and assorted size planes and use the giant size engines.

Ain't this fun!
Bill <><

I guess I misunderstood, because I certainly did not mean to say "you" crack me up.  I must have misread what you were saying, so I did not mean for my comments to read as a shot to you...or anyone else who wants to fly a big plane.   I say have at yeeee!!!

Instead what I meant was that there is definitely a wave of going to larger planes (which I see as the height of irony---this cracks me up), solely because there are larger engines available all to gain what?  Power to weight ratio (certainly not noise reduction)?  A greater power to weight ratio could be found putting a mild 60 like a Stalker in a Nobler (as a fellow in Australia did in the Aussie Nats), but what is the gain when an L&J Fox 35 will pull it through a pattern with authority?

I flew the PA 75 for pretty hard for 6-7 months, so I guess I can state an opinion about how it compares to a ST 60.  The PA 75 has way more power, no doubt.  However, once tuned to a level of "usable" power, the results are the same as with any other engine.  This idea that you can have the huge excess of power in reserve are two things:  a myth, and a recipe for disaster if something goes wrong (like missing the needle).  Heck even David Fitzgerald was running 20% nitro in his PA 75 at the last WC's.  Why?  IMHO, it was because the engine had been tuned to a stunt run, and it had no more reserve WHERE IT WAS TUNED.  The extra nitro was needed to gain a little boost from this tune point.  This result would have rung true if he had been running a .40.

There are problems associated with detuning engines.  Our 2 strokes like to be run at a certain load.  trying to run significantly less can lead to all kinds of issues (running cold, run less than steady, changing from run to run, being touchy) in fact, the opposite of what some people think they are gaining going to bigger engine.  In fact, 2 strokes like to be closer to peak than, idle, and you can make the argument that smaller engines running harder are more consistent because of this fact.  So, if you think that you can take an engine that can easily run a 16"-17" prop and stick a 12" inch prop on it and it will run better (maybe your airplane like a 12" prop) it won't.  4 strokes really like to be loaded, and unloading them can lead to all kinds of racy screaming super hot runs.

Randy can jump in here, but he does not run a bigger engine than he needs.  He has expressed these same ideas that having "enough" engine, that gives you good run with the prop you like is all you need.  Randy himself runs the PA 51.

I flew with Bob G. off and on for 20 years.  I thought he flew best on the G34 Supertigre and the PA 51.  Going to larger engines never led to an "improved" pattern.  As light and small as Bob's planes were, he could have run a modern .40 and never changed a thing, except it would not have sounded as cool.

BTW, I think a G51 and a TB II is a good choice.  I know lots of folks who put ST 46's in TB II's.  I do not see a ST 51 as a big jump from a St 46.

The best PM I ever saw was Bob Baron's.  It had a ST 60.

That is not really fair.  Todd got where he was in the competition in the first place because his equipment worked so well.

He simply got blown out in a gust that was probably 30 MPH.  The pieces of the plane did not take more than a few seconds to be blown into the corn.  The contest really should have been canceled. 

BTW, Todd's pattern was very solid to the point he got blown out.

I have seen more renowned fliers blown out while running larger engines.

Hey, big engines are cool, but if you think you are BUYING a competitive advantage over a guy with a smaller engine, you are just fooling yourself.

Bob Hunt had it right, there is a finesse component in this sport.  Flying too much engine can really screw with this component.  So, that's two things Bob and I agree on!!!!

What is the gain? The gain is that the Australian gentleman in question has won his National classic division 3 years in a row.

OK, ... uncle.... I give.

Anyway, I guess the question has been answered...  just get a Nobler and put a .60 in it and you can win the Nats.  No need for a new design.

One of the elements that we should not overlook in relation to powerplants, is the aspect of specialization.  This issue of specialization properly implemented, can lead to another element,optimization. My argument is as follows; few people would suggest that the Fox 35 is a paragon of power, but a long and intense period of specialization around this motor lead to an optimum solution, the Nobler.

Same pattern with the tuned pipe; airfoils were changed, areas were altered, props were developed, pipe tunnels were dug! Net result of specialization-optimized designs.

It would left to the Europeans to take up the mantle of the 4 stroke powerplant and VERY SUCCESSFULLY over time, by way of specialization, optimize designs for this powerplant.  I believe, based on contest record, that the Beringers series of ships is without question, of the most successful and highly optimized solutions for the 4 banger ever developed. What Luciano Compostella started, the Beringers finished.

It stands to reason that the very large displacement ships i.e. 90 size, has the potential to alter to game again, if certain limitations can be overcome-the problem of hanging on to them.  I believe they hold the potential to do something we really couldn't do that well before; fly REALLY slow. The person or persons that can come up with a really good 6 second lap\90 size bird is going to have IMHO, a kick-ass real world advantage in competition.

I have had a design for the Saito 90 "in the can" for a long time. I have not pursued it because, I don't feel confident of my ability to hang on to the damn thing knowing just what a 90 Saito can do.

 

Thanks, Greg, I didn't remember saying that!

Anyway, it's all opinion, and everyone knows the old "opinion" saying........

I think the trend of going from IC to Electric is a defensive rather than an offensive move on fliers parts.
It's much easier to practice in the public park with an electric that it is an internal combustion engine.

Jim Pollock