combatpigg

My Feedback: (3)

There were some nasty "hingers" in some of those highly mass produced designs....the model companys were so worried about line tension at all costs.

Of course free flight and control line models need some amount of "autonomous control gimmickery" to fly their missions, but I hate to rely on special mixes and other out-of-kilter compromises to make RC sport craft behave. Evidently some RC pylon racers are set up with biased trim for their specialized usage.
If 3 ozs of tip weight makes a giant scale warbird guy happy, that's great but it's hardly a "EUREKA MOMEMENT" [X(]!!

vertical grimmace

My Feedback: (1)

Funny how competition aircraft are trimmed for their specific "mission". There is nothing so sweet than flying a perfectly trimmed CL aircraft, stunter or combat. Granted this is a matter of taste. Same goes for RC. Interesting how so many of the top aerobatic pilots are flying arf's. Part of the fun of competition is designing your weapon and then winning with it.
I have not read the article myself, but coming from the competition side and having a large CL influence, instead of adding weight to the wing tip, I would remove some from the other! (actually I would just fly the airplane properly)

combatpigg

My Feedback: (3)

VG, you can't preach BOM any more without getting labeled a dinosaur.
50 years from now, an article will come out about how much more satisfaction can be had from winning with your own model and everyone will have another "EUREKA [X(] MOMENT !!" then, too.

dignlivn

I just thought, with my inexperience and my Hog
Yawing left upon rotation. That it is was Interesting
article.


Bob

vertical grimmace

My Feedback: (1)

I found my Fokker triplane "drifting" a large degree to the left of the runway at idle-low power after lined up for final approach. I have it overpowered and with a large diameter prop. I figured it was all of these factors coming into play (P-factor, Spiralling slipstream) So I added more right thrust. Something around 5 degrees. It worked great really.
I even found my Kaos to drift quite a bit to the left at low speed with high power. Funny, I kind of find it more fun to fly an airplane that has drifting and other trim issues. Certainly not for pattern competition, but I like sport models with little quirks like this. Maybe it spins better one way or snaps better that way. I have now had 2 articles from this mag brought to my attention, but have not recieved it yet. I am excited to read this one.
dignlivn, I say go for it and give it a try. Just tape some quarters on that weigh what you want. You can always take them off. Just remember doing this will effect something else, so it is just a compromise. It just depends on how you want your plane trimmed to fly for you!

combatpigg

My Feedback: (3)

dig'n......don't take any of this personal, this forum is where to find a "cynic's eye view" about topics related to objects hurtling through the air.
It's kind of a skeet shooting range for new fangled ideas.
If you try it and it helps keep your Hog on the straight and narrow, there you go.
Where is the lateral CG at now?

dignlivn

combatpigg,


Thanks for the input.

It is balanced laterally but I will
double check it prior to trying any
wing tip weight.

Bob

Lnewqban

Bob:

I have just read the referred MA article.

The article describes an anti-torque and not an anti-yaw device.

The author explains that the device is intended to counteract the effects of the high torque of powerful 4-stroke engines, installed on heavy scale and scale-sport models, during take-off and aborted landings.
During those seconds, the velocity of the model is low, and the aerodynamic anti-torque of the ailerons is small, while the engine torque (and P-factor, etc.) is high.

It seems that the author has successfully tested this for the mentioned type of models, and he even offers a formula for tip weight based on engine displacement.

Of course, the device does nothing more that purposely unbalancing the model laterally, in order to create a static torque opposed to the torque of the engine during acceleration.

For that reason, Bob, I believe, the device does not have much effect over yaw.
While the CG is slightly moved toward the right wing, by adding tip weigh, the yaw torques created by the trust and drag forces grow bigger, but they oppose each other and the resulting yaw torque over the CG remains about the same.
Please see attached schematic.

I also consider it is a solution to avoid in an acrobatic or sport model, because its effect will reverse during inverted flight and during outside loops.

For these maneuvers, the wingtip weight, will add static torque to the dynamic torque of the engine, increasing the left roll tendency.

I would add more right thrust to your Astro Hog instead, in order to compensate for any strong left yaw during take-off.
If the undesired yaw happens only right after take-off, then throttle-mixed or manual right rudder may be a better solution for your model.
If left roll is not the problem, and you are an aerobatic pilot, then the device will just make proper trimming more complicated for you.

As you, I believe it is an interesting article; however, the application of the device is limited to some models only.

Regards!

dignlivn

Thanks for the knowledge and help.


Since my last flight I have re set up my
ailerons mechanically and on the Tx.
It's rained here for the better part of
2 weeks. Hope to fly this weekend and
see the effects of my work.

I have a Saito 82 on the Hog and it weighs
8lbs. Once the prop unloads it flys good,
but I did have lean on the right aileron
the whole last flight. Thus the reason for
re working of the Tx and linkage/throws.

Should the need arrive for more work
I will try some Shims on the Engine mount

Thanks,

Bob

chuck993

seems to me to be overkill, why not use throttle control and Rudder...

dignlivn

Chuck,

My Hog flys Slow.

Bob

vertical grimmace

My Feedback: (1)

Generally p-factor and spirally slip stream are more powerful forces than torque. Torque seems to be the default term used by most, but is not the primary cause of yaw issues. Especially at the low speed, high angle of attack, high power situation experienced right at takeoff. Again, right thrust is a good trim idea here. Adding weight as stated above will cause rollout in loops and poor vertical lines.

rmh

Powerful factors
I have played around with some electric models - holding them vertically and adding/ reducing power - moving them at angles to see how much the moving prop actually affects directional stability
First - torque really shows up. you have to retrim the tx to get the model to hold stationary in a hover
these are small modesl with a max. of 20 ounces of static thrust and I hold em with thumb n finger in a "balanced state and try various trim settings -just to see what's going on.
the physics are the same tho as larger models irrespective of power to weight setups
slipstream is not all that big a force on these.
the gyroscopic actions are pretty easy to watch but the torque is the most noticable
On these models the power to weight is far greater than the Astro Hog setup mentioned
I had a Hog with an old (at the time, new ) FoxEagle 60. nice models to relax with and fly.
The worst problem on takeoff with any underpowered or low powered model is the time from no forward motion -to the point where the angle of attack on the prop is at exact 90 degrees to line of flight and the wing aoa is at lowest angle-whilst still furnishing lift
This is why the std procedure on an old tail dragger is to kick th tail up as soon as possible to reduce wing drag and put the prop at it's best (90) angle for max thrust and least gyro / advancing,retarding blade/etc.,effects angle.

vertical grimmace

My Feedback: (1)

I would agree with torque on a small electric model as the prop size (diameter) and power to weight are almost ridiculous compared to a standard model. Like I have said, I think it is fun to compensate for these factors. Once you understand them and feel them occuring to your model it is fun to compensate. If you watch video of Warbird fly-ins, almost all models head left on takeoff.

HighPlains

My Feedback: (1)

That's why it is good to have the crosswind on the right side of the airplane.

otrcman

Dick,

I'm always trying to learn something new. In your comment about kicking the tail up as soon as possible, are you talking models or full sized ?

Dick Fischer

HighPlains

My Feedback: (1)

Unless your tail dragger had very short landing gear or a excessively big prop, you can crank in a touch of down elevator trim to help get the tail flying. Once the tail is in the air, you can drive the airplane for as long as you want on the main gear with the rudder and it will just build speed without flying off. When you get either flying speed or the end of the runway, just pull back and fly. It doesn't matter what size the airplane is.

Of course it helps to have the main gear in the right location. Too far forward tends to ground loop. Mostly because the CG can get outside the wheel track.

pimmnz

Just checking my collection of Joe Nall and WOD vids, and it seems that the warbirds exhibiting the left turn on take off had a non-operational anti yaw device fitted to the back of the model...
Just as an aside, I have an Astro and a more mild mannered aircraft on the ground and at take-off would be hard to find. One of the rules that must not be forgotten is the one that states that at low speeds and high AOA's rudder is the preferred directional control. Try taking off, after ensuring that you have around 30 to 45 degrees of rudder movement, without using aileron. An Astro will actually fly quite tidily as a RO model, assuming original dihedral, of course. I am encouraging the use of rudder here, it is actually useful for stuff other than taxiing on the ground...
Evan, WB #12.

rmh

either one

HighPlains

My Feedback: (1)

Actually if you go back to the late 50's, the rudder was generally used as the main steering control on the pattern airplanes of the day. Ailerons were reserved to do rolls. This was when 8 channel reed control was top of the line.

BMatthews

I haven't seen the article but from the reference to adding an ounce of weight to the tip I'm sitting here shaking my head in disbelief. It may or may not have some good effect at takeoff but there's one thing such a weight will do for sure. And that is to make the model want to turn towards the heavy side. To counter this in level flight the ailerons will need to be slightly trimmed to provide a little more lift on the heavy side. But wait! Lift is a dynamic thing that changes with speed while that weight is going to be the same amount at high speed and low. So now you've got a side heavy model that'll want to bank to the left in a dive where the speed is high and will want to fall off to the right while in a climb or glide where the speed is low.

Oddly enough this sort of trim effect to counteract weight is the same thing we have in pitch to provide stability. A model with a positive pitch stability is set up to be a little nose heavy and then we set up the stabilizer to counteract this. The resulting stabilizer/elevator lift is speed sensitive while the weight is not. So if the model goes into a dive the tail will return it to a stable speed and level flight. If the nose lifts for some unwanted reason the speed falls off and the model drops the nose to return back to the stable trim speed.

It works well for pitch but it is not something we want in the roll axis. As many of you others have suggested this is a bandaid for problem that is far better handled in other ways. In fact I'll go so far as to call it a really bad idea.

rmh

It is easier to "sell" bad ideas than good ones.
My Seniorita is sooo good at self correcting .
-I won't get into phugoid oscillations- which are the result of setting up a good idea -well- nice slow ones anyway.

bogbeagle

In favourable weather conditions, it is common full-sized practice to begin the take-off with considerable forward pressure on the control column...so as to raise the tail as soon as possible.

(usual caveats apply)

BMatthews

Hmm... I thought I'd stuck a reply on this thread.... must have been the other related one or I hit the wrong "submit" button...

Deliberately altering the lateral balance like this is not the cure. It MAY, and I don't even agree with this part either, have some positive effect at takeoff but it'll have far more detrimental effects in flight. Easily enough to far outweigh any momentary issues at takeoff that are far more easily and correctly dealt with by using a bit of rudder, smoother application of power and paying attention to the cross wind situation.

What's bad about it in flight? Simply that the weight will make it want to turn to the right all the time. To counter this you need some aileron trim. So now your wing has what amounts to a warp in it to offset the weight. But weight issues are static while lift is related to speed. So if you set the aileron trim to compensate for one speed the model will want to turn towards the weight at lower speeds and away from it at higher speeds. Just like a warped wing would do. It'll also show up when you do a pullout from a dive or loop where the results will be anything but smooth thanks to the complicated accelerations of the offset CG location and lift skews from the "warped" wing. I won't even go into sport stunt flying where when you go inverted the tip weight and aileron trim required for upright will now add up and produce a strong roll towards the heavy side.

All in all the idea of using a tip weight to aid in takeoffs is a really, really, really, really, really, really, really, really, really, really BAD idea. I'd use harsher language about it but I consider myself a polite moderator and all those "really"s should help you get the point Frankly I'm shocked such an article would show up in print. It shows a distinct lack of aerodynamics knowledge and flying time on the part of the folks selecting articles for inclusion.

Archie League

I finally replaced my 9 year old Cap232 with an Edge 540. I sold the Cap. The new owner commented to me how difficultthe Cap232 wasto take off. I really hadn't noticed. I kinda thought it was a *****cat. I guess that means I am an anit-torgue device. One man's *****cat is another man's nightmare that needs an anit-torgue device.

Apparently airplanes adjust their behavior depending upon the skill level of the pilot. They only act poorly when they know they can get away with it. I think a shock collar placed around the fuselage, just in front to the wing, would be as effective as the anit-torgue device. That way, the airplane will know that it had better behave.