True but the problem is a 75 is 13 oz on the end of the stick and the eflight is 6.5. So the bulk of the concentrated weight is less for the electric. I am sure this will draw some long equation into play when all that's needed is to build one and fly it to feel the difference.
Baseline characteristics are still set in concentrated weight. But I have always said this. At Brodaks I let Joe Gilbert fly my beam-er. His exact words were scary fast turn. This is because of 6.5 oz at the far end opposed to 13. Simple to me. Now this airplane fly's with the cg 1.5 back from LE. What does this do? Great rounds and super flats,great glide and the combat turns comes from low weight. My kind of plane. All I need now is to be able to find time to fly.
Joe please chime in and give your assessment.
I don't need to barrage you with equations to tell you the above is silly. Fitzgerald's plane has the 75 in it and has plenty enough corner to win the Nats. That should be all the corner ever needed.
Sure it can win. Its the guy wiggling the handle. I can not have a opinion on how a airplane flies?
Like I said above all I had was 10%. I knew what to do I just didn't have the fuel.
This is funny. Is 13 oz lighter then 6.5? NOPE! And its all the way up front. True the battery weighs more than fuel but its shoved back. So concentrated wight is much more on the IC at the farthest from the CG. Pie are Round corn bread are square.
This is funny. Is 13 oz lighter then 6.5? NOPE! And its all the way up front. True the battery weighs more than fuel but its shoved back. So concentrated wight is much more on the IC at the farthest from the CG. Pie are Round corn bread are square.Well, I like my corn bread baked in a muffin pan, so my corn bread are round! y1 LL~
Dan you have to look at it close. The weights are about the same with my setup as a plane with a IC. But its spread out and not concentrated in one spot farthest from the CG. Whats not to understand?
Dan you have to look at it close. The weights are about the same with my setup as a plane with a IC. But its spread out and not concentrated in one spot farthest from the CG. Whats not to understand?But I am looking at it close! I've got my nose right up to the screen!
Again, then run an IC motor with a timer, put in 1/2 ounce more fuel than you might ever need, then, no advantage. It will still weigh less than the battery.
Brett
Yes, that is certainly an option, but as we all know the risk an overrun increases if it happens to go a little lean or something during the flight. Obviously IC fuel loads can be measured, but not to the exact second of desired engine stoppage.
I'm honestly not trying to start the umpteenth debate here. All I'm saying is that the electric quits at the same time, every time, without any of these IC risks.
As it is, this is unfair to IC competitors who would be penalized for an overrun against a timed electric model. Just my opinion.
Again, I just be askin'!
Type at you later,
Dan Center
OK I will tr y to illustrate this here
X represents motor/engine and Y is fuel/battery * is balance point
I will echo a comment by Howard about understanding how Moment of Inertia works. Moment of Inertia of a given mass is a function of its weight and the square of its distance from the CG. So, a greater mass a shorter distance from the CG might be better than a lighter mass further from the CG, depending on the parameters. Less Moment of Inertia means that a smaller force is required to initiate a rotation around the CG and a smaller force is needed to stop that rotation. Sort of an important factor when trying to emulate a square turn on our hemisphere.
Something that Bob Gialdini wrote about in his Olympic article in 1962.
Keith
But I am looking at it close! I've got my nose right up to the screen!
Again, I'm not argueing, just asking the question. I know that a 6.5 ounce motor weighes more than a 13 ounce engine. But they are not at the same point of the "stick." I wouldn't be asking the question if the PA.75 was as far forward as the Axi electric motor, and it's not. As I said, the PA.75 center of mass, or it's concentration of weight, is almost 2 inches further back. Maybe I should relate it as "accumulated weight" instead of "concentrated weight." To me, you can't take the weight of the battery, speed controller, timer, wire, and the extra lead you put in the nose completely out of the picture. At some point between the back end of the battery, and the prop shaft of the motor, there has to be a place where all that weight averages out against the lever that is the length of the fuselage that is behind the balance point. Think of it as a 4" thick by 3 foot by three foot slab of concete that weighs 200 pounds, and it's sitting flat on the seat of a see saw. That weight is spread out over that three foot square area, but it still weighs 200 pounds. It will take a certain amount of force on the other seat to lift it. Now take it and stand it on one edge on the same seat. I understand that the weight is concentrated in one smaller point on the seat of the see saw, but still weighs 200 pounds. Should it not take the same amount of force to lift it? If it takes more, is it a significant difference, or a barely noticeable one? The total weight of the electric set up as some have been using it probably weighs as much as 14 to 18 ounces or more including additional lead ballast. Yes, that is spread out, but it is still dead weight that weighs 14 to 18 ounces. And the weight of an engine and fuel tank is spread out also. And as has been mentioned in previous threads, some electric users are doing everything they can to get the balance point forward significantly, which translates to adding weight. The laws of moment of inertia and math may allow you to split the hair pretty fine. But again, my question is, how can you discount the additional, significant amounts of weight that is in front of the balance point at approximately the same distance from the balance point as an engine, in explaining the advantage that you think you are getting in turning a corner from using an electric set up?
I'll add this little tid bit also that I have been wondering about, propellers. Up to this point, I/C set ups have been using heavy, stiff carbon fibre props to hold accurate pitch, and withstand the constant pounding from the combustion cycles. I think pretty much everyone flying electric is using some sort of APC electric prop. Looking at these and holding them in your hand, they are genuine Flexible Flyers compared to a Bolly or the carbon prop of your choice of the same diameter. How much does this affect the flight of the airplane through the corner? It is attached to a power plant of similar power output as an engine, and attached to a model of similar size, weight and drag. I'm thinking that something has to be happening up front?? I mean, we know the old white Top Flite props flexed under load, so we know that happens, correct?
Again, I just be askin'!
Type at you later,
Dan McEntee
I too have switched to CF APC copy prop. I also know this if the nose was not longer it would need nose weight. Because I static balanced it in the normal postion on the first plane and it was UN flyable. That's why on the second one the nose is 1.5 longer and could have been .25 more and not hurt anything. At that given weight. I hope they come out with a 6 ounce battery.
Sounds like you are experiencing the same thing as everyone else. I assume you have the battery as far forward as possible?
Derek
So your saying (I think just the opposite of what I am experiencing) It would be better to have a heavy engine shorter nose than a lighter engine longer nose? Or am I understanding this wrong? Cause to be honest I didn't think it would work but it does.
I do now. But also remember my battery is 2 oz lighter than the battery in Bobs Crossfire.
I also have read and heard a lot of the Electric guys say that they are having to make the noses of their planes longer and have to run more nose weight than they did with IC to make them balance and fly correctly. I am sure that this is a direct result of the battery being so far back in the fuse. It seems to me that more weight near the CG is just that "more weight". It will not help you balance the plane, hence the extra nose weight.
It's that electric airplanes fly better with the CG farther forward than at the CG at which IC planes fly best. Yes, we included fuel. The APC prop is more efficient than most, so it takes less battery. I was figuring on the same CG as my IC plane and a hefty battery. I ended up with the smaller battery crammed as far forward as possible and a bunch of ballast in the nose. It has a low moment of inertia, but I'd sooner have a longer nose and a lighter plane.
Robert,
As I mentioned before, the 4-stroke guys found good corners with their heavier motors on shorter nose moments. The power curves of the 4-strokes are also a factor. But their wing loadings were/are still within some tolerable range for good turning performance.
Keith
What is really strange to me is when I fly IC I cannot feel any noticeable change in trim as I burn the fuel and when I flew electric I didn't notice that the trim didn't change through the flight. If that makes sense. I guess because in both cases the weight is pretty far from the nose so it has little affect on the trim. I can feel a fraction of an oz. in the spinner.
Derek
I don't know the math to figure that out.
I agree with Robert here, concentrating the mass around the CG gives far more design flexibility and 'should' result in eventually a better model.
Never thought of that! Sure, just move the Battery back beneath the Bellcrank where the CG is located!
Damn! Just tried that and now the CG isn't at the BC mount anymore. Is that OK? Should I fly it anyway? Will it fly better now? What'd I do wrong????
Ted
UHhhhhhhh...I think you missed something here. Brett said RUN a TIMER...you know one of those things that shuts off the fuel supply. They're legal and available now. Work off of a tiny little battery and very small servo. Less than an ounce of extra weight.
Shut off at the same time every time!!!
I saw a couple being used here in Tucson over a year ago! Worked very well.
I think Bob Whitely had one in his Blackbird that he used at the last team trials.
Personally I think it's a very minor problem and very reliable to measure fuel and keep the fuel system clean and set the needle properly.
Randy Cuberly
I handed it to you. I even did it for you. Here is the reference and calculator once again: http://stunthanger.com/smf/index.php?topic=30303.msg300702#msg300702 This assumes that you have Excel, but doesn't most everybody these days?I reviewed that thread a little before getting into this one, but missed the link to the calculator. Thanks for the reminder. I have the same problem with it that I had last time. I downloaded it, but can't get anything loaded into it? Am I missing some instruction somewhere? I promise I'll do my home work over the weekend, but got to figure out how the calculator works. Too late tonight and work both jobs tomorrow. Must sleep.
Moment from gyroscopic precession is independent of the length of the nose.
It's not as self-explanatory as it looked at the time. Enter numbers in the yellow cells. You can enter as many parts as you want (one per row for each configuration) to add up. The motor-battery example might help. There I fiddled with the motor distance on config. 2 to get the cg to come out the same as it would for config. 1.
I mean, it really shouldn't be a contest of who has the smallest front moment of inertia...
<snip> Eric the Merlin 40 will power your airplane easily, at 8 ounces..you also would need a little noseweight.
Randy
Oh, heck no. I wish I'd made my current dog's nose longer. I probably wouldn't notice the increased Ixx, but I'd sure notice the effect of removing the 3 oz. of ballast.Making the next Dog's hindquarters lighter would be even better (best of both worlds), you have the technology 8)
Oh, heck no. I wish I'd made my current dog's nose longer. I probably wouldn't notice the increased Ixx, but I'd sure notice the effect of removing the 3 oz. of ballast.
It's not as self-explanatory as it looked at the time. Enter numbers in the yellow cells. You can enter as many parts as you want (one per row for each configuration) to add up. The motor-battery example might help. There I fiddled with the motor distance on config. 2 to get the cg to come out the same as it would for config. 1.
Well Howard, I actually did download the sheet, and I tried to even be as even handed as I could to both the IC and the Epower, using the big PA for the IC, and the 6.5 oz epower motor and typical battery for a ship my size. I then did a little sooth saying, and decided I would use the actual effective CG of each part. The PA CG was determined off a real engine I had handy, then biased in relation to where it bolts down (pretty much the front two holes close to the larger ball bearing). I would imagine everything that "mounts" has it's own little moment as well, so I'm kinda winging it, but it should be really close. Like I've held Epower batteries, and aside from the wire sticking out the front, they feel pretty well symmetrically balanced, same for IC fuel tank, maybe a hair forward towards the mounts, so the middle of the battery should be a safe area to use as the point to locate it on your spreadsheet.
Anywho, using my Katana moments (10.5 nose moment, plus 3.5" back to CG for a total of 14" moment from Spinner ring and everything spread out in relation to that) it's darn near a wash, with the rear mounted Epower motor, but the advantage goes to the IC setup for moment of inertia with the front mounted EMotor by a about 12% (PA75 193 vs / EMotor 223).
I found the exercise very interesting, thanks Howard!
I'm not an aero designer, but I still have to say I feel this is only a small component of our design goals. I mean, it really shouldn't be a contest of who has the smallest front moment of inertia, because I think we WANT to run a certain length tail moment with a relational tail volume, and since I think we like to watch a certain average length fuselage package to make our tricks pretty and draw our shapes in the size hemisphere we play in.
So even if a lighter front end was actually possible, would we want it? I don't think so...
Example - I have 2) PA 40's, one old school, and one Merlin that weighs about like an FP. The scary thing is they put out nearly the same power. BUT... I would never want to use the Merlin in a big 670 square inch ship, even if it could pull it, since I'll just be adding nose weight anyways, and I don't think a redesign to force it to work would be to any advantage.
Still, like I said, it was a fun excerise.
EricV
Well, I fiddled with it, as you say, for a bit before I went to bed, and ran the curser all over the page and clicking on stuff. I finally noticed the tabs on top, and when I put the curser there, a box dropped down saying those functions are locked until I get a licensed copy of Micrsoft Office. I don't do any real spread sheet work, so I never knew I didn't have it. Makes me wonder how I was able to download it and open it up? Anyhow, probably wouldn't hurt for me to get it anyway. The only Office software I have is from 2001 or older, and probably doesn't have Excel on it. I'll look into that this weekend.
Well Howard, I actually did download the sheet, and I tried to even be as even handed as I could to both the IC and the Epower, using the big PA for the IC, and the 6.5 oz epower motor and typical battery for a ship my size. I then did a little sooth saying, and decided I would use the actual effective CG of each part. The PA CG was determined off a real engine I had handy, then biased in relation to where it bolts down (pretty much the front two holes close to the larger ball bearing). I would imagine everything that "mounts" has it's own little moment as well, so I'm kinda winging it, but it should be really close. Like I've held Epower batteries, and aside from the wire sticking out the front, they feel pretty well symmetrically balanced, same for IC fuel tank, maybe a hair forward towards the mounts, so the middle of the battery should be a safe area to use as the point to locate it on your spreadsheet.
Anywho, using my Katana moments (10.5 nose moment, plus 3.5" back to CG for a total of 14" moment from Spinner ring and everything spread out in relation to that) it's darn near a wash, with the rear mounted Epower motor, but the advantage goes to the IC setup for moment of inertia with the front mounted EMotor by a about 12% (PA75 193 vs / EMotor 223).
I found the exercise very interesting, thanks Howard!
I'm not an aero designer, but I still have to say I feel this is only a small component of our design goals. I mean, it really shouldn't be a contest of who has the smallest front moment of inertia, because I think we WANT to run a certain length tail moment with a relational tail volume, and since I think we like to watch a certain average length fuselage package to make our tricks pretty and draw our shapes in the size hemisphere we play in.
So even if a lighter front end was actually possible, would we want it? I don't think so...
Example - I have 2) PA 40's, one old school, and one Merlin that weighs about like an FP. The scary thing is they put out nearly the same power. BUT... I would never want to use the Merlin in a big 670 square inch ship, even if it could pull it, since I'll just be adding nose weight anyways, and I don't think a redesign to force it to work would be to any advantage.
Still, like I said, it was a fun excerise.
EricV
Humm only 3.12 oz of fuel?
Humm only 3.12 oz of fuel? Do-ah! Alas if my battery weight includes the wire and deans (which it does) Include tank weight and plumbing too along with at least 6.5 oz of fuel. SO as just a guess instead of the 3.1 figure its closer to 8.5-9 Not that is makes any difference but it would be nice to see the numbers.
No not really the Merlin NEVER EVER EVER uses more than 5 to 5.5 in my ships, and it will never use anywhere close to 8 ounces, the tank and 5 to 5.5 ounces of fuel weighs 6.2 ounces.
I
the tank empty weighs at least 1 oz and the plumbing weighs something. So your using 2 oz of fuel? Static CG is all hypothetical. Actual CG can only be read in flight. My CG is way forward. I thought this was about moment of enurtha not CG
The figures Eric gives are for a 75 not a 40 and doesnt a 75 weigh more that 11.5? there is also a lot missing in his figures like the coupler and part of the pipe in front of the CG. not that I even know what all this means. All I know is how my plane reacts.(http://stunthanger.com/smf/index.php?action=dlattach;topic=31792.0;attach=129772;image)
This discussion is all well and good. But I think the plane feels , turns and stops easier with the concentrated weight spread out over the legnth of the nose rather then in the first 6 inches. Not that my opinion matters but I like it. Now if they can just get the battery weight down some more.
Anyway you cut it a 6.5 engine on the nose ring is lighter than a 12 OZ engine in the same place. All I know is how it relates in the handle. Sure you can get the same thing with IC but directional stability diminishes as you move CG back
Anyway you cut it a 6.5 engine on the nose ring is lighter than a 12 OZ engine in the same place. All I know is how it relates in the handle. Sure you can get the same thing with IC but directional stability diminishes as you move CG back. I am not the one who brought this up. I have both set ups and I like the IC as well. I am just experimenting with this too see if its going to suit me. Eric brought up the comparison.
Yep I like both also, and the only thing that really matters is how it works for you, and how you like it, the exercise that is going on for years now on people telling others how much better their system is, and your sucks is really counter productive, especially when bogus numbers are used and other don't understand how this related to moments of inertia. We would all be better off building and practicing more !
Randy
I have it on the scale right now motor with wires is 6.6 oz. I guess I will have to dig out my /75 and fill the tank and weigh The stuff all over. But if I remember correctly it was 3 oz heaver in the ready to run mode than the power 25 setup.
I agree! I like them both there is no comparison as far a torque to a 75.
guys, its not about what prop the endine COULD swing, its about the prop you DO swing,, Random guess, you wont be flying your PA airplane with a 16 inch prop,,
the Eflight 25 setup ( with a 4S pack) is pretty capable of flying a lot of ST 60 sized airplanes,, its not weak by any stretch,, I flew the setup in a 72 oz airplane and while I am not an expert pilot,, I could tell I was not lacking power,,
remember,, it takes x amount of power to fly X airplane through the pattern,, having an abuncance beyond that certainly is great,, but it still only takes the same amount to perform,,,
That being what it is,, the eflight 25 in a 630 tyo 650 inch airplane in mid 60 oz area is a pretty solid combo,,
This is all I was saying look close E= engine F/B = fuel battery
IC 12.5 E -------6.5 F/B-------->LE------CG =19 OZ
EP 6.5 E -------12.5 F/B-------->LE------CG =19 OZ
Same weights just the the heavyest weight is closer to the CG. Concentrated weight is what sets up base line. This is not a debate about power or which on is better. Heck this has nothing to do with the title of this thread NOTHING.
This is all I was saying look close E= engine F/B = fuel battery
IC 12.5 E -------6.5 F/B-------->LE------CG =19 OZ
EP 6.5 E -------12.5 F/B-------->LE------CG =19 OZ
Same weights just the the heavyest weight is closer to the CG. Concentrated weight is what sets up base line. This is not a debate about power or which on is better. Heck this has nothing to do with the title of this thread NOTHING.
Sparky should be very proud that he’s done something not many of us can, and that is build a plane that came out as planned with the exact feel he wants.
Never thought of that! Sure, just move the Battery back beneath the Bellcrank where the CG is located!Hi Ted,
Damn! Just tried that and now the CG isn't at the BC mount anymore. Is that OK? Should I fly it anyway? Will it fly better now? What'd I do wrong????
Ted
"So sure, just move the Battery back beneath the bell crank where the CG is located as long as the CG can be maintained by say perhaps reducing a corresponding amount of weight in the tail. (Just ruminating here outside of the above extreme example, keeping the moments intact and getting weight off the tail may be as simple as sacrificing looks and deleting anything further aft than the elevator hinge line except for the elevator itself of course.) "Hi Randy,
Sure you can do that, and instead of moving the nose moment for 10 to 11.5 inches, you can now move it out to 18 inches so the plane will balance.
Randy
"and it's been lots of folks' experience that the electric CG should be half an inch to an inch forward of the IC CG. So it gets kinda complicated."
Hi Howard
Is this figured with a battery in the EC plane and no fuel in the IC plane? or are you calculating the IC CG with fuel in it? I am curious if they are not close to the same place when fueled.
Hi Randy,
I am talking about mass redistribution and the lessening of the moment of inertia not arm length.
If you 'could' reasonably redistribute the mass more around the CG without changing its location, and here the battery pack is a darn good start, would you not entertain a new model design to suit?
I used half a tank of fuel in the IC plane and a battery in the electric. For 4 oz. of fuel to move the CG of a 64-oz. airplane an inch, the center of the tank would have to be 16" forward of the new CG, wouldn't it?
Its not the turn rate I am looking for anyway its the feel.
Hi Ted,
when I said -
"concentrating the mass around the CG gives far more design flexibility and 'should' result in eventually a better model," you go on to say that you tried it and yet only moved mass rearward, and used that as a basis of criticism?
So I gather that you don't agree that centralizing the mass would be of benefit?
I do, and here we have the opportunity of using truly discreet components, with electric we can seriously use the greater mass of the fuel cell anywhere (within reason) as movable ballast (and this is what I truly got out of Roberts assertions) and that flexibility 'should' result in a better model.
So sure, just move the Battery back beneath the bell crank where the CG is located as long as the CG can be maintained by say perhaps reducing a corresponding amount of weight in the tail. (Just ruminating here outside of the above extreme example, keeping the moments intact and getting weight off the tail may be as simple as sacrificing looks and deleting anything further aft than the elevator hinge line except for the elevator itself of course.)
And how many models need lead in the tail to get the CG just right? Wouldn't it be nice to be able to keep both the lightest wing loading AND maintain the CG by simply shifting a necessary discreet component instead of adding a (possibly) unnecessary lump of lead?
And that is only covering pitch, what about using the battery mass to control roll for the vertical CG and tip weight?
Thanks.
Just being facetious, Chris.
One of the fascinating aspects of the amp/ohm breed is the flexibility (as you suggest) for experimentation the fixed mass hardware opens up. Thus far, however, I've not seen any substantively different aerodynamic layouts that have turned judges' heads.
I've never been a person who championed the "zero ounce per square foot wing loading" as the pathway to stunt nirvana, believing that a balance between mass, lift and control response is more important. The wing loading of major championship winning aircraft over the several decades of my involvement provides thought provoking, if not compelling, evidence for that perspective.
My gut feeling is that the damping provided by mass at the extremes will ultimately prove to be desirable for precision maneuvering by control systems other than those driven by complex intel directed inputs. Thus far I've seen no substantial innovation in the layout of even the most competitive examples. I'm the first to admit, however, that my current state of activity and, therefore, first hand exposure limits the landscape of my perspective.
I fly very little any more and only have a few hops on other peoples' electrics--none of which appeared to exhibit significant breakthroughs in terms of performance although most were "solid" stunt ships.
On the other hand I've judged quite a bit since the "revolution" including a number of guys who have been "top guns" with whatever they fly. Thus far I've not seen anything I consider to be breakthroughs in scoring as a result.
It is, of course, early in the revolution.
Just a quick thought.
There are almost literally thousands of examples of CL aircraft that display exactly the parameters that Chris, Robert and others are discussing. Mass and CG concentrated in almost exactly the same place with wing loadings as close to zero as is likely possible.
They're called combat ships. The fuel cell right on the CG and the motive force pushed back as close to it as possible. The two units, power and fuel, probably comprise...what, Howard, 60% or more of the total TOGW?
Yup, they turn on a dime but pretty much need to have that streamer trailing behind to be even remotely capable of precision maneuvers.
Is this the future of stunt design envisioned by the event's leaders in the amp/ohm era? Not trying to be snarky here, it's just the most logical destination of the train Sparky is conducting.
Ted
Is this the future of stunt design envisioned by the event's leaders in the amp/ohm era? Not trying to be snarky here, it's just the most logical destination of the train Sparky is conducting.
Ted
Or..... a StuntWagon with the nose and tail moment shortened !! :-)
Randy
Hi Randy,
you must admit that is an extreme example mate.
I have seen an electric (glow converted design) model with the battery pushed back as far as the front of the bell crank and the owner mumbling to himself that he wished that he could push it back even further. And the model has the same moments as the ST 46 glow version and still flew very well as electric with a rearward battery pack.
Anyway, I see the point of maintaining the length of the moment arms for smoothness - I 'get' it.
But I can't help but feel that movable ballast must eventually be used as an aid - canard Blue Pants anyone?
Uhhggg ! I would really try to discourage anyone who was trying to make really fast control setup in their stunt ships, This cause many problem of control, stability and big problems in the wwind, as you would need to push the CG even farther forward, and run a very nose heavy ship..
Regards
Randy
Hi Chris
LOL maybe a little extreme, and it is good to have flexibility in designs, I just DO see much to gain in putting the battery at the CG on a conventional single engine stunt ship...maybe a twin would benefit? or yes a canard !! ;D ;D ;D
Randy
That's what makes this Hobby go around I can run what I want. I know how to make it work. If I remember and I do Didn't Jimmy Castle win the Nat's with a plane and a 3 inch bell crank? I had 2 of his airplanes with that set up.
Yes you are correct, you can run whatever you want, matters not to me, I am just trying to give good advice.....If you run a nose heavy plane however, you will need to fly huge amounts of practice, Like Jimmy did.
You will also have to be very careful in high winds so you do not have the plane pushed into the ground, like Jimmy did. THe high winds will loads the controls of that type setup and at some points you will not be able to put enough control input to keep it out of the ground. That is a fact and it is just one you will need to be careful in winds.
;D ;D ;D
Randy
The 4 inch bell crank came into being because of the heavy nose weight. Everyone thinking they need to over power the wight by leavering it. I don't have that feeling of all that concentrated weight. You are right , I will never be right, You win but I will do it my way anyway.
And here's me thinking that bigger crank arms were about linearity of controls and less stress on linkages.
Didn't know about it battling CG issues.
Hi Sparky
I am not using the 1.5 inch horns either, I use 1.25 inch on both 35 and 65 sized airplanes. Using the 1.5 inch slows down my controls too much, and I would have to move the output hole out farther on the bellcrank to compensate.
Randy
I did not say you were. I am stating how the 4 inch bell crank came to being. It came into existence because of trim issues. Just like lowering the lead outs to be in line with the pipe. Whats good for one setup is not always best for something totally diffrent.
I know the definition of insanity and I don't want to keep doing the same thing over and over expecting diffrent results. So I am headed a diffrent direction. Not to say I could not make it work with IC cause I have in the past.
And sure you could make it work with IC,and even better as you could have a lower moment of inertia with a super light IC setup.
Randy
I am stating how the 4 inch bell crank came to being. It came into existence because of trim issues. Just like lowering the lead outs to be in line with the pipe.
You are flying an airplane on the end of lines made springy both by elasticity and sag due to drag. The less the lines move per degree of control deflection and the lighter the airplane, the more effect the line springiness has, and the drag part gets really nonlinear and yucky near the Netzeband Wall. I wrote a program to calculate this stuff a year or so ago. I'll write it up one of these days. Although I can't show you numbers yet without some effort, I think that a big, light stunt plane with a 3" bellcrank that doesn't move much relative to the flaps will be difficult to fly accurately.
I don't need a program to tell me that, just a little common sense.
Derek
I don't need a program to tell me that, just a little common sense.
I have not written a paper nor do I have a program or math equation to prove my theory.
...Capt Jack Ridley convinced Yeager that by changing its angle of incidence in small increments, he could control the craft without having to rely on the elevator. This had never been attempted at extremely high speeds but Yeager was game to give it a try on the next flight....
Having no common sense myself, I resort to calculation. Gary Letsinger, from whom I learn something every time I talk to him, said (approximately), "The most important thing you get from calculation is insight, not answers." This line stretchiness exercise has been pretty revealing so far, but I have more work to do. Meanwhile, I'm putting a 5" bellcrank in my next dog, and it will move through a big angle.
I haven't measured solids yet, but I want to. I was arranging to borrow some to measure, but I got distracted painting a stunt plane or something.
Just a quick thought.
There are almost literally thousands of examples of CL aircraft that display exactly the parameters that Chris, Robert and others are discussing. Mass and CG concentrated in almost exactly the same place with wing loadings as close to zero as is likely possible.
They're called combat ships. The fuel cell right on the CG and the motive force pushed back as close to it as possible. The two units, power and fuel, probably comprise...what, Howard, 60% or more of the total TOGW?
Yup, they turn on a dime but pretty much need to have that streamer trailing behind to be even remotely capable of precision maneuvers.
Is this the future of stunt design envisioned by the event's leaders in the amp/ohm era? Not trying to be snarky here, it's just the most logical destination of the train Sparky is conducting.
Ted
Back to inertia:
There may well be an optimal moment of inertia for a given stunter, and maybe it's not the minimum.
You have a new one on the paint stand? In only one year's time? I don't believe it.
Derek
Before the fire we had a 5000' roll of stainless solids. I would have been more than happy to donate some in the name of science. Not sure if I have any old lines hanging around any more. I use the carbon steel now I wonder if there is any difference in the two when it comes to strength.
Derek
Well this is my last post on this subject. I had a 48 oz piped plane and it DID NOT feel like this one. This years plane is 10 OZ heavier at 58. So if your saying that my IC was lighter on the nose it did not feel like it. It had the same feeling I have been fighting for the last 20 years. It also had a shorter nose same tail moment as I am flying now. Approx same wing area. I had also converted it to Electric before crashing it. It crashed due to mechanical failure. My mistake in poor retro fitting the fire wall.
This being said on how it equates into handle feel if this has higher numbers it don't feel like it of act like it.
All the numbers on paper and all the speculation mean nothing. What means something to me is how it feels.
Plane design has to take into account the entire matrix of the stunter. and the design needs to be optimized for that, instead of worrying about only 1 thing.
I agree on the light part, my planes of the size you have are 48 to 54 ounces in weight at the same size or larger (640 to 655 sq in.), and they had 8 to 9 ounce motors in them, used 4.7 to 5 ounces of fuel, very light weight ahead of the CG.
Robert,
You said somewhere in this thread the planes of recent past have not given you the "feel" you want but the new rig is going in the right direction as far as feel goes.
If you don't mind my asking, what is the "feel" you are after? Can you describe it?
I do not expect much at the NATS as I have had only but a few flights this year. Went out this morning and it was a Gail wind. So what ever happens happens.
Well a PA .65 dont weigh 8-9 oz it weighs 11.7 less header less pipe. If it weighed 6.5 I would use it. Of coarse I am wrong as always.
When the IC weight comes down under 9 OZ that feeling will start to go away.