The Bunt

[Peter Jenkins]

Posted by Bob Cotsford on 20/10/2018 09:16:43:

This is made worse because we're concentrating on the elevator while also trying to add throttle and worrying about the ground so it's easy to allow the ailerons to wander.

It can help to use a lower rate, trust the model, it will happily fly around an outside loop if you let it - provided it has power to pull it round or airspeed to carry it.

Bob raises the interesting point of allowing the ailerons to wander. If you fly thumbs, then as you push the stick forward, the geometry of your right hand (assuming Mode 2) holding the Tx will result in the almost inevitable introduction of some right aileron. I cured this by moving my hand around to the base of the Tx so that as I pushed my thumb forward it just needed to go straight forward and not swing in an arc. The better solution for me was to transition to using a tray and learning to fly thumb and finger fashion.

I have watched pilots fly thumbs who were unaware that they were moving the ailerons when the pushed the stick forward, or pulled the stick back for that matter. So, as suggested above, get someone to watch what you do having briefed them on what they should be looking for - inadvertent use of the aileron. It is amazing how much easier it becomes to fly a bunt or loop accurately. Most discussion about models screwing out of the loop/bunt, once you have eliminated problems with aircraft set up, are due to the introduction of aileron inadvertently. Since you don't know you are doing this it appears to be a model fault rather than what it really is, a pilot fault.

[john stones 1 - Moderator]

Yep it's pilot fault, odd that we can do inside loops nice and big without screwing them though eh, make it a push towards the deck, and anxiety creeps in and it gets rushed, that's main cause.

[Adrian Smith 1]

Interestingly, albeit slightly off subject, I have to keep concentrating hard when doing a couple of ascending rolls going into a stall turn. As a mode 2 er I have this tendency to introduce a fraction of up or down elevator when rolling upwards leading to a "wobbling" appearance. It took me a while to work out what I was doing, but I have corrected this error ....... mostly anyway.

[john stones 1 - Moderator]

Posted by Adrian Smith 1 on 20/10/2018 11:12:52:

Interestingly, albeit slightly off subject, I have to keep concentrating hard when doing a couple of ascending rolls going into a stall turn. As a mode 2 er I have this tendency to introduce a fraction of up or down elevator when rolling upwards leading to a "wobbling" appearance. It took me a while to work out what I was doing, but I have corrected this error ....... mostly anyway.

Yep, I tend have some up held in, without realising, do em in front instead of on end, to break the habit.

[Adrian Smith 1]

Yes, John good suggestion

Just shows that after years of doing something well I started a bad habit without realising it.

[Martin McIntosh]

One thing I was shown how to do when I was a beginner in F3A was how to trim out any corkscrewing on an outside loop. This does not work with inside ones.

At height, fly the model down wind directly away from you, close the throttle completely and gently push down so that airspeed is maintained to the bottom of the loop. Don`t even breathe on the ailerons. Often, one wing will be low at this point so note which one and add weight to the other until the model exits with the wings exactly level. Other factors are of course at work here such as misalignments but it is a good starting point. Yawing to one side could be a side thrust problem and nothing to do with lateral balance.

As has been stated above, if someone else can do it with your model then you are almost certainly panicing and stalling the model with too much elevator.

[Don Fry]

Does not a forward C of G make a bunt hard work for the airframe. At the point where the nose is being dragged up to vertical, the back of the aircraft is acting as an air brake trying to overcome the nose. Hard work for the motor.

[Peter Miller]

Having read all this thread I took my "Little Miss Hony Tonk" to the field this afternoon. Nice conditions but obviously the breeze was a little stronger at about 300-400 feet as the model drifted down wind faster than expected based on ground level speed.

Once at a civilised height I simply applied full down elevator and the model did five consequtive tight bunts across the wind. No corrections needed. I Just froze on full down and never moved.

I must be doing something right

Mind you, that model is great. THis afternoon the only time it flew straght and level was while it was flying inverted figure eights. The rest of the time it was just tying knots in the sky

[Former Member]

[This posting has been removed]

[cymaz]

Getting the wings level before the start of the bunt is a great help. Throttle management and where you start to open up the throttle is a major element too.

[Peter Miller]

I can do square loops and square loops with half rolls on each leg. Square bunts with that model should be no problem so add in the half rolls just for fun,

In my bunts above I just had full power at the start and left it there.

[andyh]

Posted by Peter Miller on 20/10/2018 08:49:39:

I also use NACA 1424 or NACA 1434 sections.

if my understanding of NACA airfoils is correct, those sound a tad on the thick side!

has the Miller TLAR section fallen out of favour?

[Paul C.]

Posted by Peter Miller on 20/10/2018 20:26:19:

I can do square loops and square loops with half rolls on each leg. Square bunts with that model should be no problem so add in the half rolls just for fun,

In my bunts above I just had full power at the start and left it there.

This is just the sort of model to join the hangar with my Ballerina, hoping to get it completed by the end of the year but holidays are slowing me down on my building. LMHT looks to be just my kind of model , aerobatic without being an animal .

Paul.

[onetenor]

The more dihedral a plane has the harder it is to bunt, Dihedral is intended to keep a plane upright hence flicking out of the outside loop. Reduce or eliminate the dihedral and the job is much easier.

[Peter Miller]

Andy H

I have been using those sections for quite a long time now. They are thick enough for my liking but are flat bottomed from the spar back for easy building.

They are not really thick. Clark Y is 12% and that is a bit thin for aerobatics as far as I am concerned.

I am sure that many experts will have a different opinion and probably righlty so. I just use what works for me and it does seem to work well.

Onetenor.

Lttle Miss Honky Tonk has very little dihedral which is probably why it is so good at bunts. JUst checked. 58" span and only 5/8 under each wing tip.

Paul C

You are going to love this one.

This afternoon I am going to take "The OHmen" to the field and see what I can do with that in the bunt ans square loop department

Edited By Peter Miller on 21/10/2018 08:23:31

Edited By Peter Miller on 21/10/2018 08:25:28

[cymaz]

My Wot4xl will bunt very happily. It has a thick wing, no dihedral.

[Don Fry]

My Flair Fokker DVII will bunt happily. Doesn't look pretty though. No dihedral, virtually no elevator required to hold inverted, light wing loading, Laser 75.

[andyh]

Posted by Peter Miller on 21/10/2018 08:21:51:

Andy H

I have been using those sections for quite a long time now. They are thick enough for my liking but are flat bottomed from the spar back for easy building.

They are not really thick. Clark Y is 12% and that is a bit thin for aerobatics as far as I am concerned.

I am sure that many experts will have a different opinion and probably righlty so. I just use what works for me and it does seem to work well.

NACA 1424 & 1434 have 24% & 34% thicknesses respectively. I suspect you meant 3413/3414.