15's or 18's

[RandySmith]

"Yes, Bob Gieseke fell down.  We worried about him, but then we noticed that he never let go of his pipe. ""


Yep  ya know the  winds are  pretty strong when they knock a bear flat on his butt!
 
Randy

[RC Storick]

Watching what?

So no bickering continues. I am also interested in this tread as I plan to fly my PA.65, 53 oz Viper on 0.015 lines unless the wind becomes severe then I will switch to 0.018 lines as to why take a chance on loosing my plane.

[Bradley Walker]

I think the plane needs to be 54 oz or under to have any *advantage* on .015's.  In other words, I see no advantage to flying a 60+ oz plane on .015's (quite the contrary), but I do see a 45oz plane on .018's as being at a disadvantage.

.018's on a Nobler for example...  it would just not be able to stand all that bow in the lines.

[RandySmith]

So no bickering continues. I am also interested in this tread as I plan to fly my PA.65, 53 oz Viper on 0.015 lines unless the wind becomes severe then I will switch to 0.018 lines as to why take a chance on loosing my plane.

You should have the 018s  ready to go so you can just change and fly..write down what trim changes, tip weight etc it takes, if the wind get real strong  you will want the 018s
Allan Goff  had  both 018  break at the same time flying at Muncie in strong winds. You can get a load of handle force.

Randy

[Howard Rush]

I think the plane needs to be 54 oz or under to have any *advantage* on .015's. 

I'd like to see some calculation--just of the static stuff--to show why.  I'm too lazy to do it myself.  Maybe we can goad Brett into doing it.  He knows how.

[Steve Fitton]

So no bickering continues.

Give them a little bit of room.  This is like watching a heavyweight bout, or the old Al Rabe/Ted Fancher debates on lifting tails on RC Online back in the day.  I'm tempted to get a bag of popcorn ready every time I fire up my computer!  Brad and Brett have been good about keeping the ad homineum attacks to a minimum and debating the merits of their arguments instead of just trashing each other.  There's loads of good information in the posts to pick up.  Two pros, neither of which will convince the other of the righteousness of their viewpoints but cannot resist trying anyway, makes for an excellent and informative show!

[Steve Fitton]

Yep  BUZ's  plane  weigh 50 ounces...Curt's weighed  48 ounces...someone else  had a 60 ouncer

Geez, I'd be happy to get to a 60 ouncer!  I was planning on lying about the finished weight of my Dreadnought, but, with all the weighing/pull test stuff, that may be hard to get away with.

[Bob Reeves]

I'd like to see some calculation--just of the static stuff--to show why.  I'm too lazy to do it myself.  Maybe we can goad Brett into doing it.  He knows how.

Haven't looked at the code for a couple years but Pete's calculations I transfered to LineIII has a wind speed parameter. Seem to remember asking him about it and he said something like just leave it at 0. I just entered 30 and the line tension went down.. Entered -30 and it calculated line tension at 29.2 pounds for a 64 ounce airplane.

As I said I haven't looked at it for some time so not sure exactly why wind speed is doing the inverse of what one would expect or if the result is even reasonable.. Does ~29 pounds sound reasonable for a 64 ounce airplane flying in a 30 MPH wind?

[Howard Rush]

I was thinking about 90 degrees to the wind.  Does it calculate the line shape there?

[Howard Rush]

Two pros, neither of which will convince the other of righteousness of their viewpoints...

This sort of righteousness pretty much shows up on the scoreboard.  That's one reason I went into a technical field, rather than law or sales or the clergy.

[Steve Fitton]

I was thinking about 90 degrees to the wind.  Does it calculate the line shape there?

ie, plane directly downwind?  or, as in the lines 90° to the wind (plane heading directly into the wind)

Wouldn't this become a vectors problem?  All the program has to do is calculate the relative wind to the plane and lines at any point of the circle.

[Bob Reeves]

I was thinking about 90 degrees to the wind.  Does it calculate the line shape there?

Not really, it basically assumes the wind cancels itself out for one complete lap. I can't remember how the wind parameter is used in the calculations and didn't play with it when I was writing the user interface.

[Howard Rush]

ie, plane directly downwind?  or, as in the lines 90° to the wind (plane heading directly into the wind)

Wouldn't this become a vectors problem?  All the program has to do is calculate the relative wind to the plane and lines at any point of the circle.

As I remember, the biggest yaw angles are when the plane is going directly upwind or directly downwind.  The shape of the lines is most different there, where the wind is either added or subtracted to the going-around-the-circle component.  There may be some closed-form way of calculating this, but I just divided the lines into one-inch tidbits and added them up.  It's a vectors problem, plus integrating all the little vectors.   

[Brett Buck]

Not really, it basically assumes the wind cancels itself out for one complete lap. I can't remember how the wind parameter is used in the calculations and didn't play with it when I was writing the user interface.

   I am almost certain that's the way the original works. I can't easily run it right now but I don't recall any way to even enter the wind as an input. And for certain you don't enter enough parameters to figure out the line tension including the effects of the wind. Or the weathervaning.

    We are still talking about "non-equilibrium" conditions here. If you assumed perfect airspeed stability you might be able take a stab at the centrifugal force just by vector addition of the velocities. But I think that varies so much from setup to setup and it's clearly not negligible that this would be doomed to failure. For instance, I get the least line tension, on average, about 45 degrees before dead upwind, even though the vector addition would suggest it was 90 degrees (nose dead into the wind). That implies that its flying faster than vector addition would suggest, for a good long time before it slows down to the lowest groundspeed. Although Geiseke's  (~700 sq in, 39 oz, and a PA65) looked pretty close.

    I think it's pretty clear that perfect airspeed stability is not what you want in the wind - while you might whip up more with less speed stability, you can also maintain the momentum better and get better "penetration" back into the wind. I have made several changes to *reduce* my speed stability over the years, on purpose, to get better penetration. It didn't work in 2003 (I was still pulling the old trick of backing off the needle to reduce the whip-up like we used to do on 4-2 break motors with wide-blade props in the good old days) but I have made some changes to reduce it further since. In other words, make it run *more like a 4-stroke*. Just have to deal with the higher downwind maneuver speeds, but the airplane doesn't open up the corners, so it works as long as you move your hand fast enough.

     Brett

[Brett Buck]

I'd like to see some calculation--just of the static stuff--to show why.  I'm too lazy to do it myself.  Maybe we can goad Brett into doing it.  He knows how.

   Uh, I am not sure how to define "better" in an engineering sense, so I probably don't. I would say from experiment that 54 is a good guess for an average case, but there are way too many variables.

   I have flown and preferred ST46 airplanes on .015s (at even lighter weights) but the improvement was almost certainly from the reduced drag with the feeble power available. But stuff like the CG and resulting hinge moments almost certainly dominate the effect. As Larry's chart shows we are not talking about huge numbers as far as stretch goes.

   Cut and Try is a time-honored engineering approach, I can't offer anything a lot better.

       I tried the both .015s and .018s on mine last two airplanes and I much preferred the .018s but I suspect it's highly variable from person to person. I would also say again that I would have been very nervous flying my current airplane on .015 in 2003. It scared me enough with .018s, and Allen Goff's similar plane on .018s broke loose altogether after having passed a 45 lb pull test minutes before. Had I known that had happened, I probably wouldn't have flown at all, no trophy is worth killing someone for. If I was going to run .015s, I would have a set of .014 solids set up and ready to use if the air got bad just for safety reasons.

     Going even further afield, I have some interesting pictures of your airplane in corners from this weekend. My "eyeball photogrammetry" sure seems to indicate that you have more flap than elevator. That might explain the hinge moment issue. I was also struck by how little deflection there was even in the (very tight) corners.

    Brett

[Howard Rush]

"I get the least line tension, on average, about 45 degrees before dead upwind"

So do the calculation at 45 degrees before upwind and 45 degrees before downwind.  Assume line Cd to be the cosine of the Cd when the wind is perpendicular to the line.  I think Hoerner said that's OK.  The hard part would be figuring the side force on the airplane, which would be a contributor to line tension.  The reason for this exercise, if I remember, is to show the difference between .015" lines and .018" lines as the airplane goes around the circle.  I'd just plot calculated leadout position variation vs. wind as a surrogate for yaw.  For a light airplane, I betcha that it's a lot-- even more if you compensate for side force, although that's hard to do.  I would expect calculated leadout position variation for the thicker lines to be 6/5 of that for the thin ones.  Maybe it would be worse if you include side force due to yaw.   I don't know.  

This is different than the line elasticity calculation you're doing to calibrate Godzilla's crossover point.  I don't think it needs to consider wind, although for downwind tricks, wind would favor .018s, because the added line tension due to side force would do the same thing as airplane weight to the amount the lines bow back. 

[Bradley Walker]

I'd like to see some calculation--just of the static stuff--to show why.  I'm too lazy to do it myself.  Maybe we can goad Brett into doing it.  He knows how.

Like I said, I think the advantage is the very light planes *not* having to run .018's...  Robert could easily make a 600 sq in airplane with a PA 65 in the 42 oz range for example (a T-Bird is 600 squares for example and the ST 46 was perfect for that airplane).  I know that Curt Contrada had one the first in the modern series of Randy planes that was piped powered and weighed 48 oz and it was weighed at the Team Trials.

... and as Brett pointed out, the smaller plane would not need "huge" power, quite the contrary. 

If anyone has ever flown a Nobler on .018's, you would know what I am talking about, especially if the lines had any length.  The drive is just gone, especially if the wind start blowing.

[Bradley Walker]

Curt's weighed  48 ounces

Curt's plane was smaller and lighter, and the judges did not know it... kind of shoots down the idea that "you must fly a big plane to score" idea.

[Charlie Pate]

Interesting, mind expanding on how resonance of the lines effects our stunt ships?

Have read Brett and your comments on 15's being stretchier, could be interesting to try to find the magic point of line length and airplane weight where the reduced drag is offset by the lines being too much like rubber bands.

Think of them in terms on guitar strings;if you,re a picker, and the thing begins to make sense.
long scale necks Vs. short scale necks (tuned to same pitch). .009 string tuned to E pitch Vs..012 string tuned same.
try and push a .009 now a try and push a 012 enough to raise the the pitch to the same point as you did the .009.
If you can, you probably have the strength to break the handles off your pliers.light guage hard to keep in tune compared to heavy
 Right WIL Hinton?      

[Brett Buck]

Think of them in terms on guitar strings;if you,re a picker, and the thing begins to make sense.
long scale necks Vs. short scale necks (tuned to same pitch). .009 string tuned to E pitch Vs..012 string tuned same.
try and push a .009 now a try and push a 012 enough to raise the the pitch to the same point as you did the .009.
If you can, you probably have the strength to break the handles off your pliers.light guage hard to keep in tune compared to heavy

   Certainly this sort of thing is a consideration. It's important that the line whip frequency is damped by the airplane. A lot of the value of changing line lengths is to slightly shift the frequencies up or down to keep them from lining up with the maneuvering frequencies.

     Brett

[Brett Buck]

Curt's plane was smaller and lighter, and the judges did not know it... kind of shoots down the idea that "you must fly a big plane to score" idea.

   Well, I wouldn't go as far as "shoots it down" but it certainly provides some evidence. After observing over the years, I think the judge can be counted on to identify better and worse flying regardless of other factors - including model size. I see people discussing how things "present" and what makes it look better or worse, but the scores seem to ignore that, and reflect the number and size of mistakes. So I agree - I would be surprised if anyone got short-changed because they are flying a smaller airplane. We may be able to see more evidence of that in a month and a half.

    I would point out that Curt's airplane (and Phils, during the "small airplane revolution..." a few years ago) aren't really very small at all. They are right in range of most of the planes I see and fly. David's WC airplane is smaller than Curts or Phils. They are small compared to some of the 700 sq in models flown back East (and Paul's super-giant electrics) but larger than the grandaddy of our airplane designs, the Imitation.

       Brett

[Howard Rush]

The first-mode resonant frequency of .018", 60-foot lines with a 20-oz. combat plane is square eight corners.  Thus Bob Carver would always sport fly his combat planes with .015" lines or worse.  This made for some amusing stories. 

[RandySmith]

 ""I would point out that Curt's airplane (and Phils, during the "small airplane revolution..." a few years ago) aren't really very small at all. They are right in range of most of the planes I see and fly. David's WC airplane is smaller than Curts or Phils. They are small compared to some of the 700 sq in models flown back East (and Paul's super-giant electrics) but larger than the grandaddy of our airplane designs, the Imitation.

       Brett"""


Hi Brett

The small plane revolution happened a little bit earlier here than a few years ago. For me I went toward smaller planes in 1978 after designing and flying the 725 sq in "Stunt Crafts". The first large SVs were 750 725 then 700 then down to 650. The Vector of 1985 was 627 sq in. and that is were the Staris , Satona, and Shrike came from. Those are 630 to 640 sq in.
Dale Barry had one many years ago that he used a PA 65 in, as did several others. I think Dale won the NATs with a 637 sq in Shrike and the 65 PA.
 Curt used the big PA 40 , but could have used a 51 or 61.
My Vectra, from 1987, used a 40 but had a 51 and 61 in it, it was 647 sq in, but seemed to perform as well with a hi powered 40 as the larger cube motors. I gleemed from that  test maybe matching the power plant to the plane , could  give as well if not better results than stuffing in all you could. This works for some designs but  is not conclusive on other. I know my KATANA  perform no better or worse with a 65 in it rather than the stock 51 it has ran .
It was interesting about 15 years ago Brian Eather asked for plans to my Vectra Dreadnought. after getting them his comment was "why so tiny".

Regards
Randy

[RC Storick]

  I would point out that Curt's airplane (and Phils, during the "small airplane revolution..." a few years ago) aren't really very small at all. They are right in range of most of the planes I see and fly. David's WC airplane is smaller than Curts or Phils. They are small compared to some of the 700 sq in models flown back East (and Paul's super-giant electrics) but larger than the grandaddy of our airplane designs, the Imitation.
       Brett

Insert the
 Nobler  

By the way Bart is a emotion on this board if you can find it.

Nobody get upset this is a funny response (at least in my warped mind)

[Brett Buck]

My Vectra, from 1987, used a 40 but had a 51 and 61 in it, it was 647 sq in, but seemed to perform as well with a hi powered 40 as the larger cube motors. I gleemed from that  test maybe matching the power plant to the plane , could  give as well if not better results than stuffing in all you could. This works for some designs but  is not conclusive on other. I know my KATANA  perform no better or worse with a 65 in it rather than the stock 51 it has ran .
It was interesting about 15 years ago Brian Eather asked for plans to my Vectra Dreadnought. after getting them his comment was "why so tiny".

   My comments were mildly ironic, of course. And both Curt and Phil did something a bit different - smaller wings but about the same size fuselage. I though they were much better proportioned compared to the 4' 2x4 fuselages and with disproportionately large wing things that we have tended to build over the years.

    As long as we only have 70 to work with there's got to be an upper limit,and I think we have pushed it. I sure can't see them getting a lot bigger, but I can see them getting smaller And regardless of size, I think if whatever you do lets you make fewer mistakes, it's going to score better.

     Brett

[RandySmith]

"""And both Curt and Phil did something a bit different - smaller wings but about the same size fuselage. I though they were much better proportioned compared to the 4' 2x4 fuselages and with disproportionately large wing things that we have tended to build over the years.""""
"


I agree that the look is better than the 725 sq in  pencil fuse planes I have seen. The Satona fuse is also really quite a bit smaller than the Katana. Even though it still looks 60 size, The full size Katana is 46.9 inches nose ring to tail. Its  little Brother the Satona I designed  at 44.22 inches ring to tail and is about 25 sq in  smaller on the fuse total. the  Katana has 250 sq in of  fuse area  and  the  Satona  has 225.

I can attest to the fact that 25 to 30 more squares on the fuse make a whopping difference in very high winds.
Even though both turn very hard and flat in all conditions ,The  Satona is much easier  to place maneuvers in 20 plus winds than the Katana , from just the aspect of  handle pressure  from the kite  effect!

Regards
Randy