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Old Nov 09, 2005, 09:10 PM
MacYankee is offline
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Side Force Generators


Hey All-
Having recently built a 3d plane out of blue foam, I was wondering if the performance of the plane would increase if I added some side force generators? (aka the vertical stablizers in the middle of the wings) Has anyone ever modified thier 3d aerobat to accomadate these? I know a few of the very new profile/ "Shock flyers" have them.
thanks for the help!
Gordon
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Old Nov 09, 2005, 10:41 PM
shockflyer12345 is offline
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you would get better knife edge performance but you could get very good knife edge performance if the side force generators are 25% of the wing not just a random amount of the wing
Old Nov 09, 2005, 10:47 PM
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Quote:
you would get better knife edge performance but you could get very good knife edge performance if the side force generators are 25% of the wing not just a random amount of the wing
Old Nov 09, 2005, 11:21 PM
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Go for it man...what have ya got to loose, aye?!

I have 2" high SFG's on my Tribute...
I put them half way out the span, and went from L.E. to the ail. hinge line.

Now obviously that's not a tremendous amount of area, but they make a BIG difference in KE and flat rudder turns.
I can get the thing to pivot on a wingtip virtually instantly, and KE just takes a breath of top rudder...
Of course with the Tribute, you (I) have a LOT of roll couple with rudder, and that did make it worse, but it adds another new aspect to flying my rather unique "personalized" Tribute...
Old Nov 09, 2005, 11:51 PM
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would the SFGs affect the roll rate?
Gordon
Old Nov 10, 2005, 12:17 AM
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i have been thinking about adding SFGs to my funtana .40
rudder travel all way but itīs never enough, plane always fall, even at high speed.
has anybody tried something like this.?
how will SFG affect other flying characteristics.?
Old Nov 10, 2005, 01:17 AM
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I jsut maidened my ICE 3d with SFG's sunday in 10mph winds. Was not much fun, but found out a few things about them.
Knife performance requires a little less rudder.
You will find however that a larger possible different shape rudder and fuse will give similar results. Another thing I noticed was a little less tendency to drop a wing in a flat turn, but again, proper cg and a longer tail moment will also help this. If you have no roll coupling in knife, you will have little wing dip in a flat turn. Possibly a little less wing rock if you dont have a real good harrier going, but thats hard to tell in the wind.

I have flown the ICE without the SFG's but that had a different wing, so a truly fair comparison I cant say. Best suggestion, through some on and try it.

Kirby
Old Nov 10, 2005, 11:07 PM
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Gordon...I wouldn't say conclusively that the roll rate is faster, but it seems to be a little bit faster.

The low speed also seems to be improved...I think it rides on a cushion of ground effect.

I just marked the lines perpendicular to the cf spars, and pushed toothpicks thru and then stuck the sfg's on the picks with med. CA.

I made my SFG's out of deli trays...

I also have a Funtana .40 (got all 3 of them actually) and the KE is weak...
I think it would be a worth while mod. to try on any Funtana. It's not a particularly difficult thing to do...
Making them removable however would add a complication...


Edit: I think that perhaps experimenting with different size / shape / areas SFG's on top of the wing vs. the bottom might be an interesting experiment to see if it would change roll coupling.
Last edited by proptop; Nov 10, 2005 at 11:20 PM.
Old Nov 10, 2005, 11:14 PM
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Another thought about SFG's...
Who says there only has to be 1 on each surface?

Back in the mid 70's I made an original design called the "Overdose"...
It was what would now be called a "fun fly" type.
It has huge tip plates, and "fences" at half span.
It had a "Zen minimalist structure" as I used to say, and a very low fuse. with very little side area. It was light, and did a great KE because (I'm convinced) of the tip plates and fences.

A lot of different full scale aircraft have wing "fences" to restrict spanwise flow...


Go nuts! Experiment! Have fun...pretend your "Joe Aerodynamicist" and see what happens.
Old Nov 10, 2005, 11:17 PM
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SFG's can affect roll rate.
In some cases roll rate may actually improve depending on how much side force the plane generated to start with.
In general the further out you go with the SFG's the better the roll rate will be. Moving them way towards the inside will typically reduce roll rate.
One interesting thing I have found is that any coupling is worse with them mounted far out on the wing, and coupling will improve as they are moved in.
And if you have a plane with bad coupling issues, it will typically be magnified with the addition of SFG's.
SFG's can reduce directional stability especially if they are set too far forward or mounted out of alignment.
Old Nov 10, 2005, 11:25 PM
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I've noticed that Bill!
Ya know, I also think there might be a vortex generator effect going on? Maybe that effect mixes the airflow over the deflected aileron and helps efficiency, if the SFG is in a good location that is...
Old Nov 11, 2005, 01:30 AM
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I put SFG's on two of my planes. One a 32" Wingspan, and the other is a 40" span.

I made the one on the 32" the same size as one of the winglets that the 25" zagi's use. They worked best at 13cms in from the wing tip in. On the 40" size I made them 2" bigger to match the wing. I also placed them 18cm in from the wing tip. They work awesome. One the 40" they may be to big cause they affected the rol rate and made it slower.

On the 32" it made the rollrate much quicker. It snaps on it side faster than before. I tryed a flight with them and then without them and then again with them. I not only noticed the affects of the SFG's on each plane, others did too.Without them My KE's were either all climbing or always falling now they are rock solid and I can take my hands off the radio and it will just kepp going wit WOT. It is awesome ,I would recommend trying this mod out. I think I just got lucky with the place ment size on the 32" one. On the 40" I may be a little large. So I will adjust the size on the forty untill it does not slow the rollrate down, but will keep that KE rock solid.

Oh , make sure they run ture otherwise you will cause the plane to track differently. You will have problems if they are more than a 1-2MM off.
Once I made one come off in a high speed pass. We saw it coming off and it was flapping in the wind and then ripp the depron all the way down one side. It was a cool crash.

Okay, I hope you have fun making changes maybe we should post our findings on all the planes we do it on. maybe we can save the rest some troubles.

ThankS!
Old Nov 11, 2005, 07:51 AM
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Check out my Allure with SFG's. It's my 1st plane to have them, makes KE easy and seems to add some stability all the way around.
Old Nov 11, 2005, 02:36 PM
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> went from L.E. to the ail. hinge line

If you do that, you add area in front of the mean chord of the wing. That's similar to moving the CG backwards for KE flight (reducing the stability).

I guess that's wire SFG are normally swept back and often don't start at the LE
Old Nov 11, 2005, 02:57 PM
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Quote:
Originally Posted by RobinBennett
> went from L.E. to the ail. hinge line

If you do that, you add area in front of the mean chord of the wing. That's similar to moving the CG backwards for KE flight (reducing the stability).

I guess that's wire SFG are normally swept back and often don't start at the LE

So are you saying that if you move the SFG from the L.E. back say 1/3rd of the win you will have better stability?? I am trying to understand what kind of reduced stability you are talking about. Just trying to work out some quirks in a bird with SFG's. Thanks Chris


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