If you could please describe a wet 2 cycle or how you would adjust a needle in a wet 2 cycle?

Thanks Charlie!

I will give it a try maybe later today. We may hit 47 degrees.

To me a Wet 2-cycle is a bit past the point of a 4-cycle, where it is definitely in a solid 2 stroke run, but still leaving a nice wet exhaust trail- both in the air and on the plane.

When I put the 1958 25HP Evindure on my eight foot duck boat.  That was a big mistake!  Sorry, couldn't help it.

Richard

The ideal wet 2 run is where the engine is set just above the 4 stroke, but still leans out and pulls harder in manuevers without going lean and sagging. On the ground it may still have to be breaking back and forth a bit to get the wet 2 in the air, depending on the tank set up, prop, and other variables.

Yeah, Jim, I think of a "2-2" run.  Never in a 4 cycle, but does sound like it speeds up a touch when the nose goes up.  And depending on the engine/set up, it might be "cackling" on the ground, as you pointed out..

Oops! I forgot about the mildly irritating thread. I should have worded it differently. Just my opinion, but I think both factors come into play. I remember when I was a kid mowing lawns, I was using a 2 cycle lawn mower. Back then they always ran in a 4 stroke until you got into heavy grass, which inturn loaded the engine into a 2 stroke. Once the engine unloaded again, it switched back to the 4 stroke. Maybe I will try an old Outboard Marine lawn mower engine on my Ringmaster.  . Next time we can discuss Maytag engines. They have like a 10-2 break.

My buddies and I have fought this for years and almost every bit of engine fiddling we have done over the past 10-12 years was to eliminate this issue. Almost all of it involved the internal ballistics of the engine and fuel/air supply.

    Brett

I cannot argue that point, Brett.  But will you agree that moving the tank works to cure the problem of unequal upright and inverted lap times, if you cannot fix the internal engine problems?

Bill

Thanks, Brett.  Upright/inverted lap times seem to always be the starting point for tank shimming, and seems to work well most of the time.

Funny that the "air"makes a difference, but it sure does!  And it can be a problem when trying to "help" others in different parts of the country.  What works here real good doesn't always work exactly the same  a few hundred miles away.

Bill

Brett's remarks about tuning differences from location to location coincide with stuff that happens to even this duffer with my elderly (and loved) assembly line FPs and Tower 40s. My first few years at Brodak were full of frustration. Engines that ran well at our Philly PA local often went bananas at Carmichaels. Early on, not that experienced, thought my settings were simply bad or somehow got shifted by the trip out. After years I came to understand that somehow the air was different at the Bro and my engines (especially FPs) needed to be retuned. One thing it was usually hotter at the Fly-in. Our home field is practically on the Delaware, darn close to sea level. The body of water moderating temps while adding some water vapor (maybe?) to the prevalent breezes our wee two strokes suck. Also profiles will often setup weird vibes adding, I think, to complications.

I'm glad to see Brett refer to "vast" amounts of time spent tuning in a given engine/plane/conditions combo. It gets me when I read how real-stunt-engines don't need tuning. All one needs to do is follow the directions of the designer/manufacturer. That does not coincide with my experience. At least one top flier I know is constantly trying different venturis, head gaskets, props, fuel mixes and so forth. I've even gotten into a simplified version of this with my flea market or ebay purchased (every engine must cost $40 or less, often a lot less) FPs and LAs. Four head gaskets in an FP40 will make them run a sloppy rich 4 stroke trailing a thick Fox 35 like vapor... for instance. Even tried a few of those dished hemi heads at times. Our mini 2 strokes are simple air pumps after all. We even pull out the primitive adjustable carbs sticking in a fixed opening tube. I've been thinking lately about how simplified our little gems are compared to auto counterparts. No cam, carb, or heads to flow bench. Can't even precisely time the igniting spark. Which means, I guess, that all the incidental adjustments we can get at, head gaskets, venturi opening, plug, prop and... and... have great implications for style of run or tune we achieve.

Brett's remarks about tuning differences from location to location coincide with stuff that happens to even this duffer with my elderly (and loved) assembly line FPs and Tower 40s. My first few years at Brodak were full of frustration. Engines that ran well at our Philly PA local often went bananas at Carmichaels. Early on, not that experienced, thought my settings were simply bad or somehow got shifted by the trip out. After years I came to understand that somehow the air was different at the Bro and my engines (especially FPs) needed to be retuned. One thing it was usually hotter at the Fly-in. Our home field is practically on the Delaware, darn close to sea level. The body of water moderating temps while adding some water vapor (maybe?) to the prevalent breezes our wee two strokes suck. Also profiles will often setup weird vibes adding, I think, to complications.

I'm glad to see Brett refer to "vast" amounts of time spent tuning in a given engine/plane/conditions combo. At least one top flier I know is constantly trying different venturis, head gaskets, props, fuel mixes and so forth. I've even gotten into a simplified version of this with my flea market or ebay purchased (every engine must cost $40 or less, often a lot less) FPs and LAs. Four head gaskets in an FP40 will make them run a sloppy rich 4 stroke trailing a thick Fox 35 like vapor... for instance. Even tried a few of those dished hemi heads at times. Our mini 2 strokes are simple air pumps after all. We even pull out the primitive adjustable carbs sticking in a fixed opening tube. I've been thinking lately about how simplified our little gems are compared to auto counterparts. No cam, carb, or heads to flow bench. Can't even precisely time the igniting spark. Which means, I guess, that all the incidental adjustments we can get at, head gaskets, venturi opening, plug, prop and... and... have great implications for style of run or tune we achieve.

Well, Brother Dennis, that's what makes the world go round.    Brett is a scientist, has the background, and wins NATS.  Others may not touch their engine from year to year and it still gives them runs that are better than the pilot can handle.  For them, a dedicated stunt engine that was designed to be used only in stunt, is best left untouched unless it just plain won't run out a tank of gas consistently.  Then it is a problem with the engine, not the "set up".  It's all relative.

I want my engines to run the best they can as I am sure everyone does.  And I actually do know more than I let on about such things.  But the sometimes minute changes that the real Experts experience would be lost on 99% of the guys flying stunt today, even the competition ones.  Don't even worry about the weekend warriors.

It is real easy to become extremely anal about certain aspects of this hobby.  Some HAVE to because of their missions, most don't.

AS I have said thousands of times, get the advice of the engine guy who designed the one you are using, or get it form someone who is at the top of the game and knows what they are doing.  I find that advice to be indisputable when it pertains to the vast majority of CLPA fliers.  And I worry that many of us lesser pilots hear some much about the super zoot set up that Mr. XYZ has and will end up getting committed to a nice institution with soft walls and floors because they don't even really know what a true stunt run is.  This applies up to even guys who fly locally as Experts.  Kinda like some one coming into our garage stall at Daytona an telling us to do this and that with the engine builder from Rousch standing there. 

If anyone just loves to tinker, that is fine.  Whatever trips your trigger and depending on what goals you have for the hobby.  Unfortunately, too many guys ruin a good running set up because they don't know what a good set up is to begin with.  I personally have watched "good pilots" waste a lot of time chasing something that didn't exist.  Time better spent on burning fuel.

Brett always has a set up that he knows works first time every time, if done correctly, in 99% of the inhabited world.  Randy Smith, also, as well as the others who build/modify proven stunt engines.  99% of the guys who have finished in the Top 5 at the NATS are in the same boat. 

Conclusion:  tinker with set ups if it is necessary and you know what the end result is really supposed to be.  No one is right and no one is wrong.  And not everyone will ever have to tinker with a set up if done as described exactly like the engine designer says to do. And over the years, my deduction of what Brett set out to do with the OS .20FP BBTU program, is exactly that.  A set up you don't have to "mess with" to get a run that is more than good enough for all but the less than 1% of TOP CLPA pilots.  Why fix something that ain't broke?  Unless you just want something that may not work?  Wearing Michael Jordan's own game shoes won't get me playing time in the NBA.........

But, I am aware of the fact that many want to just tinker, and I respect that.

Like I said in the beginning, "it's all relative"!
Big Bear

If an engine is known to run differently inverted to upright during flight (and most do) then why do most pilots not elect for side mounting? (Is it the' look' that suffers here?)

Surely this eliminates a know bias from the start. So a rear exhaust side mounted engine should give the least amount of drama here, no?

With side mounting it also becomes very easy to adjust the fuel head pressure by shifting the spray bar height with different venturis.

HI Chris,

I don't know about the rest of your questions, but it is simply easier for me to build the fuselage with the motor mounts glued to the fuselage sides than trying to suspend them in the middle so that engine is side mounted. 

Hi Bill,
Why would it be easier to glue the motor mounts to the fuselage sides than suspend them in the middle?

I thought that the build sequence (and this is getting off topic here) was to make a motor crutch using the first two formers regardless of orientation and then attach the sides.
I would normally chisel out accurately gridded and marked out rectangular holes out of F1 and F2 that allows for side and down thrust, slide the bearers into them, set the formers up square and glue away.

I agree that there is slightly extra effort involved but if it helps with the engine run then so be it, or if its too much to consider and the extra weight is OK then maybe radio style mounts would suit?

Anyway talk soon mate.

HI Chris,

Like I said, it's easier "for me".   it's the way I have done it for about 47 years with but one exception, a take off on the Skywriter (which worked fine).  It's just what I am accustomed to, and it works well with the Fuselage jig I use, etc.. 

I have used R/C mounts, and they also worked fine (on  "built up" profile planes)

The Europeans and Chinese use the side mount all the time and it works for sure that's well known!

But I don't see a big engine run problem using engines upright or inverted. 

Bill

Yes, Dennis,

I agree.  If a person wants to be really good at CLPA they DO need to eventually get their engines to run right with basically their own knowledge.  Some just learn quicker than others.  And some obsess about it and don't know if, or when, they do get it right.  To the detriment of flying time.

I have flown OS .40FPs in competition.  I had a really good plane around 1992 that flew extremely well with one!  I still have that engine and another .40FP and I like them both, very much. 

"Conditions" will cause problems from one part of the country to another, posts recently on that subject are interesting.

AS to "expensive", I bought one "new" PA .61 for Aaron as a Christmas present when they were first released.  Two other .61s were bought as a package deal, a .51, and a .40 (from a 2nd place NATS Open flier) for $150.  All run great, and that isn't "my" opinion.  Three of them were sold cheap because the owners did their own thing, or listened to others who didn't know, and couldn't get them to "run right".  And the second place NATS finisher wasn't one of the guys who couldn't get his to "run right", he just didn't need it anymore.  I happened to be able to afford those when they became available.  I am as "cheap" as they come.  NEver had a Ro-Jett, becuae I haven't found one for less than $200, which is my max for an engine, and then only spend that much every couple of years.

Possibly I am thought of as a "dumb jock" since that has been my life story.  Unfortunately to some people's dismay if they knew the truth, that is not the case.  It has served me well in allowing that misconception, though.  Makes it much easier to get answers.  I purposely oversimplify as much as possible when I do give "advice".  One, I don't have the "Competition Pedigree"  that carries the "weight" it always does.  But that doesn't mean I don't know, or haven't spent the time to learn.  Two, some people give advice that flies over the heads of many and in turn it causes MORE trouble.  I often quote Brett, Randy, and others, because they know what THEY are talking about and have the "Pedigree" (no offense meant in my saying that) to back it up.

I have been down the road over the years, but I have always sought out people who ARE doing things right as their records show, and I listen carefully to what they say.  I have spent the time to find out what causes problems, and found the answers to fix them for my own needs.  I don't suggest otherwise to anyone.  I strongly defend the right for anyone to do what they please in this hobby.  I just don't want to see people struggling with what becomes an obsession, sometimes, to the detriment of their flying.  If that is what they desire to do, however, that's fine too!

As to the OS .20FP, the only suggestion I have is to move to God's Country.   The have worked perfectly for those I have seen use them here.  On the other hand, NO STOCK set up I have ever used on the OS .40FP has yielded good results here, in my own experience.  Not even the one you suggest.  Different part of the country, different conditions.

It's all gravy, and as the old song goes, "It's you thing, do what you what to do......"

Just a Poor Country Red Neck member of the RNMM, here.  And remember, I am the "Original Blind Hog......" 

Take care , and good luck!  (really)
Big Bear

If an engine is known to run differently inverted to upright during flight (and most do) then why do most pilots not elect for side mounting? (Is it the' look' that suffers here?)

Surely this eliminates a know bias from the start. So a rear exhaust side mounted engine should give the least amount of drama here, no?

    Possibly cures the problem but unless you are building a round fuselage the nose construction gets pretty messy pretty quickly. And a conventional fuselage provides much less stiffness in the direction of the driving forces the engine generates (mainly up and down along the cylinder axes. And in any case, you can get engines to run with symmetry if all the internals are correct.

     Brett

Hi Bill,
Why would it be easier to glue the motor mounts to the fuselage sides than suspend them in the middle?

I thought that the build sequence (and this is getting off topic here) was to make a motor crutch using the first two formers regardless of orientation and then attach the sides.
I would normally chisel out accurately gridded and marked out rectangular holes out of F1 and F2 that allows for side and down thrust, slide the bearers into them, set the formers up square and glue away.

I agree that there is slightly extra effort involved but if it helps with the engine run then so be it, or if its too much to consider and the extra weight is OK then maybe radio style mounts would suit?

Anyway talk soon mate.

The fuselage is usually just a box.  There's no reason that the doublers supporting the engine bearers cannot be on the top and bottom instead of the sides.  Engine and tank access hatch is then on the side instead of the top or bottom. 

The fuselage is usually just a box.  There's no reason that the doublers supporting the engine bearers cannot be on the top and bottom instead of the sides.  Engine and tank access hatch is then on the side instead of the top or bottom. 

Well, except that the fuselage is usually a box with straight sides, but a top and bottom that need to be tapered to look nice.  Laying the engine on its side means that you have all that nice strength of the bearers floating well away from the fuselage sides that might benefit from them.  I'd consider tying the bearers to the formers through holes, then tying them to the fuselage sides with a false top & false bottom.

(I didn't describe that well.  Here, let me think it really hard .... OK, got it?)

Well, except that the fuselage is usually a box with straight sides, but a top and bottom that need to be tapered to look nice.  Laying the engine on its side means that you have all that nice strength of the bearers floating well away from the fuselage sides that might benefit from them.  I'd consider tying the bearers to the formers through holes, then tying them to the fuselage sides with a false top & false bottom.

(I didn't describe that well.  Here, let me think it really hard .... OK, got it?)

Tim,
I understand your concerns here but to me its all about attaching the motive power to the lifting surface the best way possible and then the 'look' of the model is sculpted to suit.

Just view some of Al Rabes models to see how 'floating bearers' can be designed to work with an inverted engine mount and with a side mounted motor a similar ploy can be used although I would prefer to use the angled out thrust on the bearers to contact the inboard fuselage wall, that gives quite a large surface area that is very close to the nose/wing joint and it becomes very stiff in the process.

Cheers.

...I've seen many a $250 to $400 engine run so so at contests. Needled too lean or too rich, incorrectly shimmed tank, poor prop choice, insufficient break in, etc. I've seen $40 engines run sweet with useful power throughout the pattern, $40 engines that run well contest after contest, season after season. Don't know how a CL competitor can get around the need to learn the basics of getting a wee 2 stroke to work right. No matter the cost of a given engine there are fundamental tuning issues to be mastered.

No worries Dennis!  Keep flying and burning fuel in your $40 dollar engines, and keep practicing.  Someday, all on your own you will tumble to the conclusion that you need a better motor.  You will have reached a new level of enlightenment like the seagull in Richard Bach's book, and you will know that we are right!

  Maybe we are talking about the same thing or miscommunicating. Most of the vibration is from the up/down motion of the piston and counterweight. Yes, you could counterweight it perfectly but most aren't.

    Brett

Hi again Brett,
We are talking about the same thing here and I agree with most of what you say.

The crux of the matter is that you could probably get more engine choices behaving themselves symmetrically 'if' they were mounted side saddle and its not that difficult to engineer a fuselage that will be stiff enough to combat the vibes on that plane of operation.

Please note that I state 'stiff enough' and not that side mounting would be the stiffest possible solution with the least amount of material used. There seems to be many ways to over engineer builds so that its more than possible to get a very satisfactory and stiff side mount snout on the model.

One point I don't see eye to eye with you here though, you can not perfectly counter weight any single cylinder piston engine by just using a conventional crankshaft.
Its always a compromise between the weight of the piston/con rod moving vertically against the circular motion of the crank weight.

As soon as you achieve perfect primary balance at TDC and BDC the secondaries at 90º and 270º double in amplitude to produce a twice rpm speed 'buzz' so characteristic of most four cylinder car and bike engines (but I highly suspect you know this anyway mate.)

It just that I see side mounting as the most logical mounting system available and especially so with rear exhaust engines.
It places the engines weight outboard thus obviating a small percentage of the needed tip weight, allows the fuel head to be exactly inline with the spray bar at all times (both vertically and horizontally) and stops the internal ballistics of the engine from operating asymmetrically. Its also easier to clear a flooded engine and that is very important with four strokes and diesels.

And yet the biggest opposition to it seems to be appearance and the break from tradition but I rather like the look of the Yatsenko type models and their ilk, don't you?