Hi guys

i test flew my new bird this weekend. all incedences are set to 0 and it is pretty accurate. i set the cg to about 35 %
i took off and had to trim it a fair bit of up elevator. to acheive and equal nose drop both upright and inverted i reduced the trim a little. however the elevators are still trimmer a little up. this does not affect downlines. they are dead straight down
where should i go from here ? should i reduce the stab incedence? should i leave it as it is ? or maybe give the motor a lil up thrust, the Seba way?

will be greatful for useful input.

Do you need mixing in knife edge? Probably you will need a little positive incidence in the wings to get better level trimming. It is usual around 0.5 degrees.

I tried to find the triangulation method that was in the k-factor few months ago. I could not find it. I am sure that someone will help us to find it.

Vicente "Vince"Bortone

A good place to start is .5 positive on the wing and 0 on the stab. Since the wings are symmetrical they do not lift at 0. Start with a little positive and it will allow the plane to more level as well will help your mixing.

Arch

Vince,

This is Bryan Herbert's site and the author of the Triangulation Trimming. Click on his welcome link and you will see the link to the article you want. Hope this helps

http://www.hebertcompetitiondesigns.com/

Larry

My Partners are setup very similar to what you describe. At first I was not happy with the uptrim, but it doesn't affect it adversely. Quique told me to trim it this way to help with vertical lines. My mixing is very minimal, and the airplane flies very true setup at 0-0.

thanks for you replies

yes i do need knife edge mixing ... the plane pitches down a bit and i get a tiny it of roll in the opposite direction of the rudder.
about changing the wing incedence though, doesnt that make things worse when i fly inverted. i mean .5 positive in upright flight is -.5 inverted? could you clarify upon this point?

Hi Alex,

The roll tendency does not have any relation to the wing and stab incidences. This is related mostly to dihedral.

The common practice suggested by ZN is 0,25 to 0,4 degrees negative stab with respect to the wing.

You have pitch coupling on left KE to the belly and zero coupling on right KE.

Seems that your plane needs up elevator on left KE, if you either move your CG forward =>will need more UP elevator then, or decrease the stab incidence then you may correct this issue, but you will "damage" the right KE qualities. I face exactly the same issue on Integral and only solution found is 10% up elev mix on left KE. My stab is set at 0,4 degrees negative to the wing.

Nikos

Let me expand on what flyncajun meant with the goofy smile. The wing will seek the same angle of attack based on speed no matter what incidence you set the wing to. If you follow the recommendations made by Bryan Hebert's trim article, you will find that inverted flight ends up requiring less down elevator, your snaps and spins will land cleaner, your elevator will have more authority without being twitchy, and you can get rid of most mixes (depending on design). Bryan's designs fly with no mixes.

No mixes.... See to believe or I should say fly to believe. I need to get one of those now.

Vicente "Vince" Bortone

Where is the article then? There's no article at BH's web site.

Can someone post ii in .pdf or .doc format?

Thanks in advance,
Nikos

http://www.hebertcompetitiondesigns....ngulation.html

here you go Niko, ive been doing my homework
i will increase my wing incedence to 0.5 or ... em some where around there. dont have a guage.
and we will see how it performs on the weekend
Niko i need more right thrust right? i am being forget ful

Hi! Oh yes you need a bit of right thrust but following Chip Hyde's theory you don't need one.... Because on inverted it becomes left thrust...So best thing you should do is to use some kind rudder mix...and bla bla bla...

Would not rather to confuse you but you will find lot's of theories, the most practical trimming charts I have found are from Pete Goldsmith's trimming article and Mike Chipchase's K factor trimming article from the 90's.

I have full respect to other people's theories but seriously we do not have enough time to make all these tests, clock is ticking and we must start practicing...

Catch you later,

Nikos

Hi,Buka.
Set your c/g at 25% of the mac, this is the most important step ,,do not use a 35% cg this is way too far back on all pattern models regardless of the design.
If your wings are 900-950 sq. and the airframe is over 10.5 pounds you will need .7-.8 pos inc.
set the stabs at zero But you will wind up .2 or so pos, if they are adjustable fly first and adjust the stabs to the elevator trim ,,,after you get the airplane
flying pure.
The airplane only needs .5 down and .5 right thrust but this is not important right now,
the only reason why you would need rudder mix ,,,,is because the airplane is tail heavy regardless of what anyone told you.
With rudder mix,you are compensating for an unstable aircarft. try to shoot a arrow with no tip ,,,I don`t care how big the fletch is it`s unstable and it wont go straight.

Guys,these are not theorys they are proven by 20 years and about 15 designs,,,, prove me wrong if you can <G>
Do you want a 5 % overall improvement in your Score? ,,,,try my Method.
also How Could I predict Niko`s trim problem in my article ,,,if I can`t give you the Cure
and by all means follow to the letter of the article ,,and let us know what happened
I have helped countless guys trim their Integrals with no, or very little Mix.
set your c/g to 25 % first...very important.
then use my method.
Here is some home work for you guys,,,
Go to Oxia `s web site, look at Christophe`s new design on the side view, he also uses the same setup I use ,,,,now
tell me if his wing is not set up at about .8 pos,,,
then admire his snaps again
Bryan

I like Bryan's arrow anology.

Vicente "Vince" Bortone

Bryan thanks for your reply and you have really predicted our trimming problems in your article. The cure seems a bit sophisticated for me at least, because if I move the CG forward I will have some opposite effects that will need to be corrected too.

You, Chip and Christophe would probably need the 0.5 points that a very, very staight line could provide in a competition and could actually win big events with an average plane.

Me an average guy (or lower) may need more stick time with his plane rather testing angles of various parts of the plane. The trimming charts I have been using have helped me to trim my planes quite fast so that I can start practicing as soon as I can. That's was all and did not have any intention to question your trimming procedure.

I hope some day I can take advantage of your trimming advice.

Regards,
Nikos

Nikos, You'd be amazed how much a true airplane can give anyone the ability to score high. The top echelon pilots can fly around mixes and flaws because they have the ability... for the rest of us the most essential thing is to start with equipment that is true. A stable airframe makes any pilot better.

Will shifting the CG forward have an effect on the snaps? I.e. will they end up deeper and slower if you're not off the elevator in time, or will the opposite occur?

Rudder deflection controls the speed of the snap in this setup. Everyone I fly with flies with Bryan's setup, and we all have to switch to low rates for our snaps. What this setup does for snaps (and spins) is makes the airplane stop cleaner with no need to lead with opposite rudder or perform miracles with the sticks in order to keep the airplane on line. The further back the CG is, the more unstable the aircraft becomes, in this setup the airplane will be more stable, lock lines better, and most importantly for your question it will recover from the stalled conditions of snaps and spins more cleanly. If you doubt me or Bryan (granted, we are biased) a few months back Brett Wickizer of the US team posted that after trying it both ways, he felt the airplanes snap better with a more forward CG. Trimming a pattern plane is a delicate balance, luckily Bryan has done all the legwork and has been kind enough to share his knowledge with anyone who wants to use it. I talk to Bryan about once a week, and any time I question something he tells me, his response is simple: prove me wrong. This is the same challenge he has made to anyone else who doubts what he has found to be correct. Try it, I can promise you that if you think you've proven him wrong, he will be able to tell you exactly what you did wrong, and what to do to fix the problem. The biggest key with his trimming concept (it doesn't really qualify as a chart) is that if you skip ANY part of it, it will not work.

I have been using Bryan's methods and they are spot on. In my opinion it is far better using 5 sessions to trim your model as suggested in the Triangulation Method rather than just keep practising schedules with a model where the trim could be improved. When trimmed properly you simply get more consistency flight after flight. if you are averaging 6 per manoeuvre and can get an average of half a point increase per manoeuvre then that is nearly a 10% increase in your scores!! Much easier than more practice - and consistently better!!

Brandon

In all honesty I did change the setup of my ship to the triangulation method and noticed a big change in the flight pattern of the aircraft, but my CG was and is still around 30% MAC. I'll shift a battery pack forward and see what I get!

Could you share what you changed and the improvements? I am sure that tracking is going to improve when you move the batteries. You will notice more in cross winds.
Good luck.

Vicente "Vince" Bortone

Matthew,

What do the ailerons control in snaps then? Not being a smart aleck, just curious.

hey guys was out experementing with incidences today. i think its flyes better with positive incidence on the wing. how ever... in the triangulation method it ways to seet the stabs to compensate the trim. well in my case that would be giving them nevative incidence since i have up trim on the elevators. please elaborat.
apart form that i have some role cupling when in knofe edge . especialy on the knife edge loop. any thoughs on that.

thanx for your replies

In a snap the aileron deflection is used to help initiate and maintain the angle of attack changes necessary to keep the wing stalled throughout. The tail steers the nose of the airplane through the maneuver. Some airplanes (not pattern airplanes mind you) can do a snap roll with only rudder and elevator.