Worlds Engine Question

[Ted Fancher]

Hmmmm.  the times they are a-changin'!  Fascinating stuff!  Enjoyed  reading it all and looking at myfive old timers hanging on the wall...they all had little tear drops dripping out their spinners!  (Well....maybe not really!)  Thanks to all for taking the time to do so.


Old man Ted

[Bruce Shipp]

Did the Sharks with pocket hinges have taped/sealed hinge lines? 

[Howard Rush]

At takeoff the DC is not activated as well as either SF function.

I noticed some extra RPM at launch from, I assume, the positive x axis acceleration feedback.

Thanks for your help with the new system. It’s pretty cool.

[Paul Taylor]

Did the Sharks with pocket hinges have taped/sealed hinge lines?

It’s my understanding pocket hinges don’t need to be taped if done as Sparky shows in his videos.

[Ken Culbertson]

It’s my understanding pocket hinges don’t need to be taped if done as Sparky shows in his videos.

I do not tape mine and some of the other guys I fly with don't tape theirs either.  The pivot is about 1/8" into the flap.  Hard to find a surface that isn't moving too much to tape and for some reason, probably the uniformity of the gap, they just don't seem to need it.

Ken

[Matt Neumann]

Matt,
Well, not really. At takeoff the DC is not activated as well as either SF function. What you are seeing is the prop I use. It is the Igor underchambered 12" 3 blade. That along with the 3520 gets it up to speed quickly.

Out of curiosity how much battery do you use?  My experience with undercamber while producing more thrust they also load things up more using more amps.  Sometimes quite drastically.  Also, how does this compare to the flat back with the amount of battery usage?

I used Igor's flat back version for awhile then switched to the Ukranian 12.5 version.  I have a couple for version of the Ukranian props that should be here any time.

[Bruce Shipp]

I do not tape mine and some of the other guys I fly with don't tape theirs either.  The pivot is about 1/8" into the flap.  Hard to find a surface that isn't moving too much to tape and for some reason, probably the uniformity of the gap, they just don't seem to need it.

Ken

Thanks. The pictures did not look like  Sharks are sealed.  I was curious because the Sharks seem to have a flat TE on the stabilizers vs. the recessed TE such as how Ken builds his. 

[Paul Walker]

Out of curiosity how much battery do you use?  My experience with undercamber while producing more thrust they also load things up more using more amps.  Sometimes quite drastically.  Also, how does this compare to the flat back with the amount of battery usage?

I used Igor's flat back version for awhile then switched to the Ukranian 12.5 version.  I have a couple for version of the Ukranian props that should be here any time.

The prop I use consumes about 2250 to 2300 mah in Muncie.
That is about 400 mah more than the flat back prop.

FWIW, Igor gave me a 12.5 dia 3 blade flat back to try. I will let him know what I think of that after I try it.

[Matt Neumann]

The prop I use consumes about 2250 to 3000 mah in Muncie.
That is about 400 mah more than the flat back prop.

FWIW, Igor gave me a 12.5 dia 3 blade flat back to try. I will let him know what I think of that after I try it.

The weird part, I was using one of Igor's 12 inch three blade and then tried the 12.5 of the Ukranians.  No difference in battery usage or need to change RPM but I immediately noticed a difference in thrust.  The thrust part I expected, the no change in settings or usage I did not.  I was using around 2000 to 2100 mA.

[Igor Burger]

The number of combinations is approximately 123 billion.  Seems like a lot!

Last timer had only one setting - sensitivity (beside the timing) and I saw several complains it is too complicated. So now we have 123 billion and I think it is still "too complicated", so no difference 

It is a significant improvement over his old one. Some have asked Igor if he would take his old ones back for a discount on the new ones. He just laughs!!

Keep them, soon it will be discontinued so I guess someone can be lucky with only one setting 

But seriously - Paul has prototype with many settings also some of them we found not necessary, final version wil have . again only that sensitivity (do not worry, there will be some back door for masochists tech guys )

And that taking back, I would like to do it, because I am sure it will be good stuff, but unfortunately it is very difficult to send things to EU, because of difficult import processing etc.

[Igor Burger]

The weird part, I was using one of Igor's 12 inch three blade and then tried the 12.5 of the Ukranians.  No difference in battery usage or need to change RPM but I immediately noticed a difference in thrust.  The thrust part I expected, the no change in settings or usage I did not.  I was using around 2000 to 2100 mA.

Depend which props, I guess you are speaking about that wide undercambered. That other 12x5N is designed to have high efficiency, because it is dedicated to relatively small AXI motors which cannot withstand load of that larger. And yes of course you pay by little smaller static thrust. But we are not hanging on prop so static thrust is not so important value and where it can be somehow important, for example in corners .... guess how we solve it   

And consumption of that undercambered is clear, that is how such props work, they do not unload shaft during braking (property of the airfoil) and therefore they have little better resistance in strong wind. Something is for something.

[stuntvideo]

You also need to think how easy it is to get nitro in Europe


Sent from my iPhone using Tapatalk

[Lauri Malila]

You also need to think how easy it is to get nitro in Europe


Sent from my iPhone using Tapatalk

 What is this talk about the difficulty to find nitro in Europe? It's available now and in future. Of course because of the new laws it's maybe not as easy as before, but still no problem.
I don't use nitro, but it has nothing to do with availability or price, I just don't need it. No nitro does not mean bad power, bad needling and bad stability. Quite opposite actually, at least with my technology.
L

[Brett Buck]

And consumption of that undercambered is clear, that is how such props work, they do not unload shaft during braking (property of the airfoil) and therefore they have little better resistance in strong wind. Something is for something.

   The drag bucket effect was a brilliant insight and it explained a whole bunch of things we had found using U/C props, but otherwise had no idea why. It was also one of those "how the heck did I manage to miss that for the last 10 years?" moments.

   Well done!

     Brett

[Igor Burger]

   The drag bucket effect was a brilliant insight and it explained a whole bunch of things we had found using U/C props, but otherwise had no idea why. It was also one of those "how the heck did I manage to miss that for the last 10 years?" moments.

   Well done!

     Brett

I was also surprised that time how those props can work. It was long thread  on Compuserve  in 1998. 

details are still, after 25 years, on my old pages (on bottom of the page):

http://www.netax.sk/hexoft/stunt/notes.htm

[Steve Fitton]

What diameter is the "better to beat you with" prop?

[Igor Burger]

There is always some optimum for given model and power train. Larger prop gives better static thrust and therefore better speed stability (amount of thrust change as function of speed change). That means it will pull better during climbing and brake better in diving. But it will also slow down while flying against wind, especially in upper loops during flying against wind, and that will result in slowing down overhead and thus lower line tension in hourglass, vertical eight and four leaf in strong wind. That is why there is an optimum - typically heavier model needs larger prop.

BUT ... usage of active timer which will accelerate uphill, will allow smaller prop.
BUT ... usage of weaker battery, which cannot accelerate enough (popular lions) will not allow as large timer acceleration as Lipols do, will lead to larger prop again.

... and than there is something like moment of inertia which will limit limit corners, delay acceleration and lead to precession with larger props - but that is about mass, not diameter itself.

[Shorts,David]

Once upon a time there was a rule created saying that no outside radio control or other device was allowed to change throttle, yet now we have something which is infinitely more advantageous than what the rule prohibited. 
Wouldn't make sense to change the rules just for USA, so would fai consider a rules change to rpm limiting controls only?
Otherwise everything there is no competitive future for IC.  I might propose such a rule for classic.

[Paul Walker]

Once upon a time there was a rule created saying that no outside radio control or other device was allowed to change throttle, yet now we have something which is infinitely more advantageous than what the rule prohibited. 
Wouldn't make sense to change the rules just for USA, so would fai consider a rules change to rpm limiting controls only?
Otherwise everything there is no competitive future for IC.  I might propose such a rule for classic.

And you want to rule out pipes as well? How about changing head shims to change 4-2 break, and how about venturi size changes as well?
Your concerns are way too late, but you can always submit a rules proposal to AMA, and let it be voted on.

[Brett Buck]

Once upon a time there was a rule created saying that no outside radio control or other device was allowed to change throttle, yet now we have something which is infinitely more advantageous than what the rule prohibited. 

     Not that I know of. I know that Windy and his cheering section repeatedly claimed there was such a rule, saying we put it in to "get Windy", but in fact there wasn't any restriction at all on that until about 20 years later, when the "2.4 GHz rule" was adopted.

    I also note that there was not, is not, and likely will never be a rule prohibiting feedback control of the engine through an onboard system, with absolutely identical functions as the latest Igor system, and in fact you can probably hook up a servo directly to an Igor system instead of a ESC, and use it to manipulate anything you want - carburetor, exhaust throttle, variable pi...er, never mind that last one, just disregard/ 

Wouldn't make sense to change the rules just for USA, so would fai consider a rules change to rpm limiting controls only?
Otherwise everything there is no competitive future for IC.  I might propose such a rule for classic.

     Quick answer is no, they probably won't take that seriously. You can submit such a proposal, but I predict it goes exactly nowhere, both because the FAI has no real rule change process, they are actively promoting electric over IC, and there is far too much invested in it to make it suddenly obsolete. Of course, no one will stop you from trying, but I consider that idea to be the ultimate example of tilting at windmills.

    I also am not quite so sure how much of a disadvantage there is, and I am sure I can direct you to people who think IC is superior. I was at a contest 3 hours ago where IC finished 1-2 over a field of largely electric, some of which used the very latest stuff (prototype Igor controller), and 3 of this years NATs Top 5. Of course, the IC setups *also used the state-of-the-art equipment* with underlying vast expertise needed to make it that way.

   Even if it is better - so what?  We handled a far bigger step forward by retaining no restrictions at all and letting the pilots decide what they wanted to use. Compare the hot setup from 1975 (say, ST46 with a 12-6 Rev-Up) to 1993 (piped OS-40VF and a carbon fiber 11.3-4.25) or 2024 (piped 61-75 AAC ). Even the lowliest $75 RC sport engine with a $2 prop (46LA with an APC) works far better than the worlds best ST46 in the most skilled hands.

      As always, you are certainly welcome to follow through with your ideas, no one has a veto power, but I think the idea is very unlikely to go anywhere, nor do I think it should. If it's better, it's better, and I think it is plenty close enough to not cause us to start banning things or trying to cripple electric development.

    Brett

 

[Howard Rush]

Wouldn't make sense to change the rules just for USA, so would fai consider a rules change to rpm limiting controls only?
Otherwise everything there is no competitive future for IC.  I might propose such a rule for classic.

 How would you enforce such a rule?  You could have the CD put a device on each plane to record timer pulse spacing during each flight.  The rule would have to specify pulse spacing tolerance.  It would be easier to issue constant-RPM timers to contestants.  We do that with fuel for F2A and F2D.  Better yet, just ban electric power.  I was going to propose a rule to ban electric power for stunt, but the horse had already left the barn. We should certainly bad electric for old time and classic (except for ignition). 

[Igor Burger]

You could have the CD put a device on each plane to record timer pulse spacing during each flight.

This is actually not enough, there is closed loop PID regulation inside the ESC and with little modified PID values so that it makes certain overshoot will still do some amount of active controll.

Keith R. tried something like that in his timer.

BTW banning electric in F2B will eliminate 3/4 of young blood in Europe, because we simply cannot fly IC on most places (and I did not mention availability of usefull engines, price of fuel and banned pure nitromethane in EU). But it will bee good way to prevent youngsters to kick our old butts on contests :-P

[Ken Culbertson]

 

But it will bee good way to prevent youngsters to kick our old butts on contests :-P

I keep arguing that the "Classic" event in the US should apply to pilots designed of kitted before 1970, not what they fly!

[Brett Buck]

  I would also add that almost no one reading this has ever come close to optimizing their IC setup, and many are still struggling with the very basic issues with consistency and setting the needle.

    The difference between the average IC system and the very best IC systems are also FAR FAR GREATER than the difference between the best IC systems and the best electric systems. So we are not just comparing apples and oranges, we are comparing apples and dinosaurs. The corollary is that many people currently running IC could make rather massive strides with pretty straightforward attention to detail and careful experimentation. Then electric will not seem like the massive advantage it currently seems. The good news it that while IC is becoming difficult to support in some senses, the best equipment and knowledge that has ever been available is pretty easy to get and has abundant information on how to proceed.

   I will however grant that it is "easier" in some ways to get a middle-of-the-road electric system to work than it is for s mrdiocre IC system, but that mostly boils down to people either not paying attention or getting caught up in the 80+ years of complete and utter nonsense associated with IC engines in stunt.

    Brett

[Shorts,David]

How would you enforce such a rule?  You could have the CD put a device on each plane to record timer pulse spacing during each flight.  The rule would have to specify pulse spacing tolerance.  It would be easier to issue constant-RPM timers to contestants.  We do that with fuel for F2A and F2D.  Better yet, just ban electric power.  I was going to propose a rule to ban electric power for stunt, but the horse had already left the barn. We should certainly bad electric for old time and classic (except for ignition).

Obviously nobody is going to ban electric.
And I was asked, how would this be enforced?
I was also encouraged that the difference between electric and IC is smaller than many believe.
I have used electric for years with Hubin and Renacle timers and recently used a timer with a separate accelerometer.  I found the difference to be a large one. However, I only flew my piped plane for 2 seasons and can't recall exactly how it controlled speed anymore. 
But enforcement is a matter of integrity.

I think the difference for classic at least would obsolete non piped engines versus accelerometer assisted timers. But that should be a separate discussion perhaps.

[Ken Culbertson]

I think the difference for classic at least would obsolete non piped engines versus accelerometer assisted timers. But that should be a separate discussion perhaps.

I could be convinced to relegate Classic to Non-Piped IC and Non-Accelerometer timers for electric.  Banning electric is just not practical if just for the noise issue alone.

Ken

[Dave_Trible]

I guess I missed the obituary about the untimely death of IC........perhaps these new full wave pipes will re-adjust the playing field a little.  Three of the the top five at the Nats were IC.   Not so much at the Worlds but IMHO that wasn't power-it was airplane design and the fact that most those who entered chose or had to fly electric.   I don't care who flies what but I don't buy the IC is doomed argument.   Now that I've got that off my chest.....

Dave

[Dan McEntee]

Once upon a time there was a rule created saying that no outside radio control or other device was allowed to change throttle, yet now we have something which is infinitely more advantageous than what the rule prohibited. 
Wouldn't make sense to change the rules just for USA, so would fai consider a rules change to rpm limiting controls only?
Otherwise everything there is no competitive future for IC.  I might propose such a rule for classic.

     Way back when, I believe that throttles and any kind of cut off or timing device was not allowed in FAI, at least that's what I'm remembering. When electric came along with the need for a timer, then that rule was eliminated. In my view, what is in the nose of the elite electric models is a programable, computer controlled robotic throttle. You can't really compare that to changing venturis, pipe lengths, or head shims. Everyone has access to the laws of physics and the hardware to tune the engine. Tuning the engine adds another aspect of human involvement and skills. The electric power delivery just requires the spending of more money and grasping the knowledge to take advantage of the technology, which seems to be constantly changing. Depending on the person involved, I don't know if using the electric power plant is any easier. I have seen people have just as much trouble and technical problems with it, sometimes more, as they do with I/C. In the 40's, 50's and 60's, when many more people were participating in the hobby, there were still a LOT of people that just could not grasp what they needed to do operate an engine consistently, and that's why there are SO many engines laying around and posted on eBay with very little to no time on them and/or missing parts. People just did not "Get It." It's probably worse today. This years W/C at Muncie, with it's large schools of Sharks swimming around in the air, is a preview of what may be instore for future events. It may get like R/C pattern, with everyone flying the same airplane with computer controlled powerplants, depending on where you are in the world. But I do not think the internal combustion engine will be come entirely extinct. people will gravitate to the technology that appeals to them, and to some of us, prepping for an official flight, and getting that bump when turning the engine over to tell us that it's alive and ready is a big part of the event. I don't know if you can make us gear heads extinct or not! If all I had available to me was electric power plants, I most likely would not participate, but go back to free flight gliders and rubber powered models. I can still pick thermals, and as far as I know, you can't buy those off the shelf anywhere!! 
   Type at you later,
   Dan McEntee

[Ken Culbertson]

I can still pick thermals....

And they can still ruin your day!

Ken

[Dwayne Donnelly]

I think it's important to point out we're talking the very top end of competition here, at most local contests glow is still very much in use, I was at a contest in July that had competitors from Canada and the US and glow far outnumbered electrics, I think there were only 4 electrics and I was the only one with a active timer, so I wouldn't worry Dan glow isn't going anywhere and most electrics don't have active timers. 

[Ken Culbertson]

I think that the migration to electric within our current community will be slow but steady, especially at the top.  However, if I were a new flier or a returning flier which technology would I choose?  In my own case, when I returned on the first day I saw a piped 75 and an active timer equipped plane flown by some local experts.  I thought I was in an episode of "The Twilight Zone" and actually quoted Will Smith out load - "I have to get me one of these!".  But which one.  As luck would have it both an LA46 and a cobra 2820 were made available to me so I did both.  Granted the LA46 was not piped but it didn't cost $600 either and the Cobra came with a FM-9 timer so I was actually apples to apples.  It wasn't till I built a plane for a Fiorotti timer that I saw how unequal they were and made my choice to go electric.  When I lost everything in the fire I didn't replace any of the IC.

That is just one man's observation.  Changing is difficult if you have mastered the piped IC.  Few have "mastered" it. 

Ken