Why a  flat fuse side instead of a rounded  side?  the rounded type would have less wind .. resistance than flat side

IMHO you want resistance to mitigate line tension between up and down wind.  However, I am beginning to question that for active timer electrics and think that perhaps the smallest side area possible might be the best. 

I have no idea if this is true or not having flown only one such plane.  In my way of thinking, if the timer is capable of maintaining line tension and you have the power then side area of any kind is a minus.  True or just another brain fart? 

Ken

For peasant stunt , I think the best thing to use , is side mounted , tank inboard of the NVA .

As in the spraybar goes through the intake outside of the case , rather than through the case .

That way the nose is thinner in profile ! . 

One might consider feeding back ESC output current in one’s motor control system.

Just on observation I doubt it makes a ton of difference.    But the amount and distribution of side area does, in my opinion.  The airplane isn't sitting still in the wind and much of the side impact wind is deflected rearward by the prop blast.  It still has effect. 

   As far as that goes, speaking only for myself, my fuselage is designed to have a large amount of passive yaw stability and minimize sideslip, particularly slideslip from precession/power handling. That was a design goal dating back the ST46/60 days. In that, it also has the effect of reducing/minimizing any sort of lift in +-Y, since it is always trying to drive the AoA to zero. This has interesting effects at times, the only really serious problem being entering the wingover or overhead, since it want's to follow the relative wind vector - from the vector sum of the airplane motion and the wind - so it tends to yaw nose-out upwind and yaw nose-in on the downwind side.

      The latter is definitely a positive, it relieves some of the line tension in the "low" maneuvers. The former, you might think would be an advantage, by increasing the line tension on the upwind side. That it does - until you try to turn a corner upwind, then, the sudden added tension of moving the controls, whips the nose in a bit, the airplane slows down and thus increases the angle of the relative wind vector, so it tends to yaw back and forth a few times on the way up. The workaround it to be very careful not to hammer the corner too much.

      If you look at the Linheart Smith picture of my airplane starting the wingover at the 2006 NATs, you can see this effect, it has already whipped in and then rebounded nose-out. The wind was not particularly strong, maybe 5-8 mph (it got a bit more later). And you can also see that these upwind corners, which looked bloopy marshmallow soft to me by design, is still pretty snappy. The fuse is vertical at maybe 12-15 feet and you can see that there is still substantial control deflection (which is going to be snapped out of there as fast as my little fingers can move a few tens of milliseconds afterwards).



     Brett

Yep . To big a fin , and they weathervane nastilly , upwind . And Down .

theres a thing about side area Fwd. to help keep the nose up , in overheads . Eights & the like .

      But that is also unstable all the rest of the time. Right or wrong, I am doing my best to not use the lines to restrain it in yaw (or roll) to the extent possible. Unstable or marginally stable systems require the lines to provide the restoring force. Igor posted a force diagram describing it, somewhere. here:

https://stunthanger.com/smf/at-the-handle/leadout-position-66742/msg684636/#msg684636

    The problem with using the lines to stabilize an otherwise unstable system is that it keeps trying to push on the lines, which rings them up, and goes completely unstable if you get enough upset to lose line tension entirely. Putting in intentional nose-out yaw aerodynamically, stable or not,  (i.e. rudder offset) causes the airplane to yaw around as the the line tension changes, and also, heavily couples the axes due to the products of inertia trying to rotate around an skewed axes.

   Again, this is just my approach, I am sure there are legitimate differing opinions - and lots and lots of stunt BS.

           Brett

This is very complex stuff. No only shape, but also area distribution, LO position to that shape, thrust offset and especially SIZE of the model. I think I wrote something about it in the past when we developed indoors. That makes it very very visible.

Since one thing will work on large models flying on long lines at relatively high speed as Brett wrote:

    The problem with using the lines to stabilize an otherwise unstable system is that it keeps trying to push on the lines, which rings them up, and goes completely unstable if you get enough upset to lose line tension entirely. Putting in intentional nose-out yaw aerodynamically, stable or not,  (i.e. rudder offset) causes the airplane to yaw around as the the line tension changes, and also, heavily couples the axes due to the products of inertia trying to rotate around an skewed axes.

It will not work on small models:



Those indoors have little larger nose area than necessary for neutral yaw stability (as I used on my MaxBee which is designed only microscopically stable, but controlled by ridder). Plus they have LO position aproximately 20 degrees aft of the CG position. Result is permanent 20 degrees in-flight yaw making enough fuselage area to make safe line tension overhead (remember the lap time is equivalen of lap time of large models - it is designed to teach kids all figures -or even slower) on only 5m long lines. Centrifugal force (centrifugal acceleration) is far smaller than Gravity, so line tension is really maintained by only fuselage lift and motor thrust.

That extra nose area is necessary in case when modes slows overhead, lower line tension stabilizing yaw will cause nose yaw even larger so that prop thrust will cover lower fuselage lift during slow flight. Who tried those models, will tell you funny effect, that since you must run when model stalls overhead, indoor pilot can simply wait and it will once go over the head.

Those models do not have articical yaw stabilization by controlled Rabe rudders, so result is some yaw problems because of precession of that large 10" props and especially by corners causing inward yaw (I am not sure with english terms - inertial torque caused by rotating around non-pricipal axis ?)  But looks like it does not have too much problems in turbulence free air in gymn, pilot can easily adapt.

An now to the point - we tried to fly it also outside in little wind. It was very surprizing that wind does NOT accelerate it like large models, it slows it. And it does to the point that flying is impossible, it will simply stop on tops of loops. Later we found that it is much easier to fly on upwind side, where wind DOES accelerate it. It is caused by that extreme permanent yaw, the fuselage works like wind mill in the air. The same will work also on large models (that why I use relatively large yaw angle on my MaxBee = LO far aft of standard settings), but it work only little bit on large models. May be I had to write some paper about all of that, but retired people have very limited time during days :-P  Most of that is already distributed on this forum, or it was onstuka, may be it is ebough just collect some knowledge base from such threads.

That means something else will work on large models, somthething totatlly different on extremaly small models and something different somewher in between.

SPEAKING OFF WHICH


Four types of local winds are sea breeze, land breeze, mountain breeze, and valley breeze. The sea breezes and land breezes are opposites, with sea breeze occurring during the day and

So , Again , Its WHAT is WIND .

This bloke seems to be having fun ,

up to a point . 

Brings up wind Flyer Gene romero , um - Shaefer , and his Hallmark . FUSELAGE SHAPE . And John Havle's Folkerts . Designed as a ' wind capeable ' ship . Both similar side profile . They mustve considered APPROPRIATE .