Planes with Heavy Wing-Load = Less Responsive?

[Kafin Noe’man]

I have a Vector with 15 oz/sq.ft of wing-load which I believe it’s considered too heavy. The question are, do heavier planes tend to fly less responsive? And does it make it harder to control the size of the maneuvers because it tends to go bigger in size? And will changing the line handle spacing help to make the planes become more responsive?

[Paul Smith]

Certainly.
It's a simple contest between wing lift to make the plane turn and mass that keeps the plane going level.
The only way to get the lift to make a heavy plane turn is to fly faster and thus get more lift.  But the judges like SLOW so you won't score as well as light slow airplane.

[Dave_Trible]

Paul's explanation is a good one.  However your airplane might also be too nose heavy causing slow or heavy response.   That is unusual where the whole airplane is overweight because the lion's share of the extra weight typically falls behind the CG which tends to make the plane tail heavy.  Maybe though you have a chunky engine and muffler or for some other reason it's nose heavy.  If the CG seems to be in range then you can surely open your handle up to speed up input.  I do a great deal of "trimming" with handle adjustments to fine tune for each airplane individually.  Then of course that handle and lines stays with that airplane exclusively.  However if the airplane is really too porky no amount of lipstick will overcome that.  Increasing speed on perhaps longer lines can make up for extra weight to a point.

Dave

As an added thought-  a good way to tell where the CG should be on your airplane is to pay attention to the glide after the engine quits.  While holding the handle neutral the airplane should maintain a fairly level attitude and slowly wind down to touch down.  If the nose immediately drops and it picks up speed with a steep angle towards the ground requiring you to apply up control then it's nose heavy .  If, on the other hand the airplane really looses speed rapidly , the tail drops or it tries to climb into a stall,  it is tail heavy and needs nose weight.  Once you have that adjusted about right then you can make whatever handle adjustments are needed to get the 'feel' you want.

[Ken Culbertson]

I have a Vector with 15 oz/sq.ft of wing-load which I believe it’s considered too heavy. The question are, do heavier planes tend to fly less responsive? And does it make it harder to control the size of the maneuvers because it tends to go bigger in size? And will changing the line handle spacing help to make the planes become more responsive?

More responsive may not help.  If you can get full movement of the controls with your current handle setting and that is not enough to make the plane turn fast enough then making it "not turn enough" sooner won't help.  With a heavy plane (and 15oz/sq" is heavy but not by an unflyable amount), there are a couple of things that can help.  Move the CG back some and increase power a bit or go to longer lines and start wrist strengthening exercises.  Heed Dave's warning.  The CG should never be so far back that you can't land properly.

Now, with the CG back it will want to stall quicker so you will need to increase the speed to hold that off.  It may want to hunt more but that is a lesser evil than stalling.  However, if you rebuild it (I saw you on Charles Zoom meeting last night), strip it entirely and find out why it is so heavy.  Typically ARF's are not that heavy.  If it is not correctable don't waste time rebuilding it.  You now have first-hand experience why a really heavy plane is not desirable.   Move on.

Ken

[Gerald Arana]

I have a Vector with 15 oz/sq.ft of wing-load which I believe it’s considered too heavy. The question are, do heavier planes tend to fly less responsive? And does it make it harder to control the size of the maneuvers because it tends to go bigger in size? And will changing the line handle spacing help to make the planes become more responsive?

Kafin; Don't worry about the weight. Heavier ships fly much (much) better in the wind! And of all the contests I've flown in (mostly RC gliders) (and won)  were in the wind.

Don't believe me? Try flying a balloon in the wind................

Also see Ted Fanciers (sp, sorry Ted) article on "light" planes. He ended adding 8 oz's (I think it was) to get it to turn a good SQ. corner.

Good luck, Jerry

[Colin McRae]

Kafin, there is quite a bit of information on SH concerning heavy models and specifically the Vector 40. And I am talking about my model which weighs 61.5 oz with a corresponding wing load of 16.5. (I wish my wing load was 15!!)

There are 2 posts about the weight issues w/ my Vector with good information.

I did not build my model so had no control over the weight. But I quickly learned how much weight paint and covering can add to a model if one is not careful. Lessons learned for me surely.

Have you tried to reduce the model overall eight any way you can? My model needed quite a bit of nose weight to allow it to have a good CG. The added lead up front was first located in the fuel tank bay. I needed to get the weight farther up front, so I added a heavy brass spinner nut which did help lower the overall model weight. I also moved lead farther forward by locating the weight inside the pocket area of the engine rear cover. This also helped. Basically, less weight placed farther forward on the model. I was able to reduce the overall model weight by around 2 oz without changing the CG location I wanted.

With all that said, my understanding is that the Vector is considered a somewhat heavy model. So as others have said it needs to fly fast. I continue to work with ongoing trim items on my model. I was flying it on 60' lines (0.018 size lines). I am going to try 62' and 64' lines to reduce lap time, while still allowing the model to fly fast.

I don't know what engine/prop combination you are using, but I run an OS 46 LA and trying different props. A large diameter / low pitch prop spinning fast will help. I am currently using a 12-4 APC prop.

[Dan McEntee]

  You have to trim and fly a heavy model different than you would a lighter model of the same design. As mentioned, balance is critical, then how quickly the controls move and how YOU move them is important. The airfoil is important in all of this also You have to kind of nurse the airplane through the pattern and taking it's weight into how you fly it. Some models can carry extra weight better than others and that is mostly in the wing design and it's airfoil. Flap size and deflection needs to be more finely tuned.. If you can go through the process and get a heavy model to fly better and do the entire pattern acceptably, that greatly helps with you over all flying skills and well you can trim and "normal" model. Speed is your friend here along with momentum. If you can keep the airplane's speed up and can carry that through the maneuvers, you should have a decent flying airplane. Just keep in mind that there will be a limit. We had a club member here in the Midwest, Jason Pearson, who along with his Dad built a couple of SIG Twisters entirely out of pine, just to see if they could and see how well they flew. The finished airframes had iron covering on the wings and paint fuselage and finished out around 60 ounces and powered by an FP-40, I think.. That's HEAVY for a Twistor!! You would have to really try hard to finish up a kit to come out that heavy. I saw Jason fly his several times and he even entered contests in the Intermediate class and he did well with it. This was because the design of the airplane was able to handle it and Jason learned how precisely he had to fly it. At that time I probably would not have believed it if I had not witnessed it!! Some would tell you not to bother with a heavy model, and just build something better, but if you have it and have the desire to try, why not?? There is a lot to learn from it. If you have a crashed model that was already heavy, and trying to decide to repair it or not, there is a lesson here in that also. Repair the model and at the same time, try to figure out how to shed some weight in the process, and be careful with the reconstruction and finish to avoid excess new weight. Work on it in your spre time if your other models are good to go. If successful in the end, you will have another model to fly for just fun flying or general practice. Learning is one of the reasons why we do this stuff. You don't learn anything from an endeavor if you don't at least make an effort and try.
  Type at you later,
   Dan McEntee

[Dennis Toth]

Kafin,
The Vector is a very good flying ship, what type of power are you using Glow or electric. Is it paint or film finish. If paint you could change the covering on the wing and tail to film and save significant oz's.  A couple other things to look at. First make sure you have the flap/elevator is set up for a 1 : 1 ratio to give max lift (some have even gone a little more flap but not much). In the extreme you could add a strip of say 1/4" to each flap trailing edge to increase the area slightly. Another option is to replace the flaps with flat (no taper) square edges ones, this gets the flap working faster and is similar to the Gurney flap that some are using, (this is a vertical piece added to the trailing edge that extends above and below the flap ~1/16 to 3/32") this also gets the flap adding lift quicker.

Now if electric you need to play with two things. First is the prop - too large a diameter will slow the turn so you want the smallest diameter you can get away with. For a heavy ship (even if glow power) you want a prop that bits quickly and this is usually wide blade and under-cambered. This ship is at the very top end of what a good FOX 35 could pull. That means somewhere around a 10" diameter prop. What I have used on my electric Stuka (48" span, 38oz with battery) is an APCE 11 x 5.5 cut to 10" and pitched up to 6.25" at 9875 rpm, it pulls like a freight train on steroids (could go down to a 9 - 9 1/2 if needed to make the flight time with the lighter pack).

You next have to look at the battery pack. Diameter and rpm are the biggest impact on amp draw. When weight is critical, reducing these allows a smaller, lighter pack. I believe Brodak recommends a 4S 2700mah pack which is 8.8oz. I have used a Zippy 4S x 2700 pack and changed to a Thunder Power 2200 pack (~7oz). This saved about 1 3/4oz and even I could feel the difference in the way the ship performed. The battery back is the heaviest component for electric and when you are close on weight the one worth working to reduce size.

Good luck with you trimming and let us know what you do and how it works out.

Best,    DennisT

[Brett Buck]

I have a Vector with 15 oz/sq.ft of wing-load which I believe it’s considered too heavy. The question are, do heavier planes tend to fly less responsive? And does it make it harder to control the size of the maneuvers because it tends to go bigger in size? And will changing the line handle spacing help to make the planes become more responsive?

     If you mean "responsive" in the same sense everyone else does (i.e. how much it rotates in pitch for given handle input), then, no, if anything, heavy airplanes are tend to be tail-heavy which makes them more responsive or potentially unstable. Heavy airplanes will not support as tight corners when it comes to generating lift, but the tendency to be tail-heavy tends to drive you to over-controlling which then puts you closer to running out of lift (stalling).

   As before, it is very rare that an airplane is hopeless just because it is too heavy. Almost always, there are other trim or power issues that make them fly poorly and if you correct those, it will fly OK.

     As before, do not become obsessed by weight or your perception of "too heavy", it is almost certainly not causing any significant problem for you, it is trim and power that are the issues. Most beginners would be better off throwing away their scales and just dealing with the problems they are presented.

     Brett

[pmackenzie]

Certainly.
It's a simple contest between wing lift to make the plane turn and mass that keeps the plane going level.
The only way to get the lift to make a heavy plane turn is to fly faster and thus get more lift.  But the judges like SLOW so you won't score as well as light slow airplane.

Lift goes up with the square of the velocity, but so does the centripetal acceleration/ centrifugal force in a turn.
So going faster will not make a heavy plane turn tighter

The important part is to have enough power to able to counter the drag in the turn, and to pull the model up with authority when climbing.
And to have an airfoil that can generate the higher lift coefficient required for the heavier model in a given radius of turn.

[Bob Hunt]

Even a brick will fly. But a light brick will fly better than a heavy brick.

Bob Hunt

[Ken Culbertson]

This is a good discussion, but one thing is missing.  How/why did Kafin's plane crash.  He explained it on the Zoom meeting, but it was totally garbled so he may think we know why, when we don't.  Last I checked, garbling does not make planes crash.

Kafin - how did it crash?

Ken

Could inverted garbling maybe make one crash?

[Kafin Noe’man]

Hi Ken, I crashed my Vector when I was doing the Horizontal 8 maneuver.
I flew 2 times, first one was really fast 4.7 sec/lap, it had really strong tension and I was having a hard time.
And even with the fast lap time, the Vector wasn’t really responsive to the input and it made the loops to be always big.

The second flight was much nicer with 5.15 sec/lap. It was smooth until I tried to do the Horizontal 8, probably I didn’t start high enough so I would have more room for the one loop to be completed, but I was thinking the slow response thing played some roles here.

[Brett Buck]

Hi Ken, I crashed my Vector when I was doing the Horizontal 8 maneuver.
I flew 2 times, first one was really fast 4.7 sec/lap, it had really strong tension and I was having a hard time.
And even with the fast lap time, the Vector wasn’t really responsive to the input and it made the loops to be always big.

The second flight was much nicer with 5.15 sec/lap. It was smooth until I tried to do the Horizontal 8, probably I didn’t start high enough so I would have more room for the one loop to be completed, but I was thinking the slow response thing played some roles here.

  In that case, run the CG aft or (much more likely) increase the handle spacing. Wing loading almost certainly had nothing to do with it, unless you stalled the wing, too.

   As Pat notes, flying faster will not do anything with regard to the ultimate limits on the turn, but you aren't reaching that anyway. Flying faster does have other secondary effects.

     Brett

[Ken Culbertson]

Hi Ken, I crashed my Vector when I was doing the Horizontal 8 maneuver.
I flew 2 times, first one was really fast 4.7 sec/lap, it had really strong tension and I was having a hard time.
And even with the fast lap time, the Vector wasn’t really responsive to the input and it made the loops to be always big.

The second flight was much nicer with 5.15 sec/lap. It was smooth until I tried to do the Horizontal 8, probably I didn’t start high enough so I would have more room for the one loop to be completed, but I was thinking the slow response thing played some roles here.

Thanks for filling us in.  Anybody that says that they never planted one learning the horizontal 8 is probably lying.  This the first introduction to initiating a outside turn towards the ground in the learning process.  Up to now you have been doing loops starting at level flight.  In the horizontal 8 you are starting that outside loop going straight up.  It is the same loop, it just starts in a different place.  It was a very long time ago but I do remember the difficulty I had in starting the eight before the plane was in front of me which made the outside way over to the left and hard to control.  I didn't account for the acceleration from gravity and whomp.  Time to rebuild.  It is very hard to learn the transition from inside to outside if the plane is not in front of you.  After a long layoff I was again having trouble with the horozontal 8.  In a thread, Ted Fancher suggested doing the eights "high and tight" to help me regain how to center them then gradually expand them back to normal size and in the same thread Brett also correctly pointed out that when you have a problem in a maneuver it is likely that it was cause by something you did wrong earlier.  I think this is your case.  Try Ted's exercise.  It will give you confidence that the plane will do the maneuver and even more that you can do it.  It takes time before upright and inverted are just the direction the plane is going at the time, but it will happen and that fear that the ground is going to leap up and grab it does go away.

If you rebuild the Vector let me pass this along.  I flew a borrowed one for a year after I lost all of my planes in a fire.  It was a bit heavy and slightly nose heavy.  Since it was not mine I learned to fly it that way.  It "tracks" very well so you need to fly it through the loops or it will open up quickly. It was set up with very slow controls and I used a very wide handle spacing.  It transmitted the pressure on the controls back to the handle so that I knew when this was happening and I could increase the handle pressure to compensate.  This may be what you describe as sluggish.  It was a pleasure to fly but I would not set a plane up that way.  I earlier commented that I did not think changing handle line spacing would help but I forgot that the one I flew was pretty wide.

Ken

[Kafin Noe’man]

Thanks all for jumping in.
It would be a very valuable lesson for me to learn.

[Ken Culbertson]

Slightly off topic but not really.  In my response to Kafin I mentioned Ted's exercise to get the feel of the 8 back.  I haven't been able to fly for a month till today.  My first flight was all over the place so I thought, Why Not try Ted's workout.  So, on the next flight I did 15 consecutive horizontal 8's with 10' bottoms and no laps in-between.  It fixed everything.  Rounds were round again, intersections in the same zip code, center flats gone.  Kafin - you have to try this, It works.  Thanks Ted and Brett!

Ken

[Dennis Toth]

Ken,
The feel for the 8"s sounds interesting, where is it on the forum? Maybe you could give more details on how it is done.

Best,    DennisT

[Ken Culbertson]

Ken,
The feel for the 8"s sounds interesting, where is it on the forum? Maybe you could give more details on how it is done.

Best,    DennisT

This is the original thread that started me using this technique.  My description is how it works for me and how I see the progression of errors/fixes.  My daughter was a competitive Ice skater.  When you see a skater "pop" a jump or double a triple it is because they made an initial error and they know that any attempt to fix it in the air is impossible.  We are no different.

https://stunthanger.com/smf/at-the-handle/overshooting-intersections/msg646044/#msg646044

 It is against all that I was taught early on "fly the pattern every time...", bla, bla, bla.  So I thought I would listen to some folks that I agree with for the most part on technique and just about everything else.    The point was to find out the cause for my horizontal eights intersections over lapping.  Brett pointed out that this sort of problem starts early in the maneuver and is a culmination of trying to fix a mistake then fixing the fix, and so on...  Ted offered a way to spot the cause and work toward a solution.  The Horizontal 8 does not wrap your lines.  You can do as many as you want in succession.    Start like you are doing the new clover and at about 30 degrees start flying h8's at about 3/4 size, Ted says "high and tight".  This puts you far enough from the ground that you can concentrate on all of the causes one at a time till you get each one right then move on to the next.  First on my list was the starting point.  You should be facing the intersection.  I was starting the first loop there.  It should be 22.5 degrees to the right.  One Opps bites the dust.  Second are the loops round?  You can actually watch your hand as you are out of harm's way.  Are you having to give it control to make the intersections? Are you tracing the path?  That will take a few reptations, but you should be starting to get the rhythm.  Lastly the one that ties it all together the actual intersection.  Getting the flats out is not as simple as not holding neutral.  It is getting the spacing of the two loops that are now round correct so that the plane needs no additional control input to "hit" the intersection point.  Lastly it gives you time to practice going from up to down in a split of a split second.  This may be the last problem area for the 1st eight, but it is the first mistake for the next one.  Doing them over and over reinforces that.   Once you have them tracking really nice small, open them back up to full size (still way up the sky) and do a bunch more then, lower the bottoms back to 5' do a couple more and crash because you ran out of fuel.

Seriously this Works!  All that rounding of loops pays off on the single rounds as well.  Hope this helps someone with the same problems, and since I also judge I can tell you that a whole lot do.  Also, I deserve -0- credit for this, I am only following the advice from those that know better.  Another side benefit is that it is a great warmup exercise after a layoff.

Ken

PS, do not try this with the Overhead eight if you are over 60.