How do they do that????
10-04-2007 | 03:58 PM
#26
Senior Member
RE: How do they do that????
And with the aileron deflected.
The rigid horn on the TE of the wing keeps the boost tab pushrod localized and when the aileron moves, the tab is pushed or pulled in the opposite direction.
The rigid horn on the TE of the wing keeps the boost tab pushrod localized and when the aileron moves, the tab is pushed or pulled in the opposite direction.
10-04-2007 | 04:01 PM
#27
Senior Member
RE: How do they do that????
OK, I see Bruces link is working now, and it's an excellent description. It appears to offer some numbers with it.
In our modeling application, the tab can reduce the force needed to drive any of our surfaces. With the big models those forces can go way beyond what our servo's can give. And we often wind up with 2 or 3 servos, each of which costs big bucks, working just one aileron. Not good economics. And beyond the money, it's a royal pain. The servos have to be sync'ed for one. Installed for another. A royal pain.
It's actually amazing that they aren't on every big bird of ours. Guess not many model designers know about them. Or maybe the servo mfg's are paying hush money.
In our modeling application, the tab can reduce the force needed to drive any of our surfaces. With the big models those forces can go way beyond what our servo's can give. And we often wind up with 2 or 3 servos, each of which costs big bucks, working just one aileron. Not good economics. And beyond the money, it's a royal pain. The servos have to be sync'ed for one. Installed for another. A royal pain.
It's actually amazing that they aren't on every big bird of ours. Guess not many model designers know about them. Or maybe the servo mfg's are paying hush money.
10-05-2007 | 08:36 AM
#28
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From: Woodville, WI
RE: How do they do that????
I wonder if there's a practical size limit to using boost tabs.
By that I mean, when is a control surface (and by inference the plane) too small to make boost tabs not worth it.
Would a 1/4 scale be too small? 1/5? 1/6? What about small gassers? or even down to 1.20 or smaller birds?
By that I mean, when is a control surface (and by inference the plane) too small to make boost tabs not worth it.
Would a 1/4 scale be too small? 1/5? 1/6? What about small gassers? or even down to 1.20 or smaller birds?
10-05-2007 | 11:18 AM
#30
Senior Member
RE: How do they do that????
ORIGINAL: ED STEFAN
Thanks Bruce/da Rock,
Man you guys have very sharp eyes to have spotted that on the cover.
Thanks Bruce/da Rock,
Man you guys have very sharp eyes to have spotted that on the cover.
When you've been building and drawing your own for awhile, you realize that the details are what makes the differences. And you look for 'em like they were worth money to you.
10-05-2007 | 11:29 AM
#31
Senior Member
RE: How do they do that????
ORIGINAL: vmsguy
I wonder if there's a practical size limit to using boost tabs.
By that I mean, when is a control surface (and by inference the plane) too small to make boost tabs not worth it.
Would a 1/4 scale be too small? 1/5? 1/6? What about small gassers? or even down to 1.20 or smaller birds?
I wonder if there's a practical size limit to using boost tabs.
By that I mean, when is a control surface (and by inference the plane) too small to make boost tabs not worth it.
Would a 1/4 scale be too small? 1/5? 1/6? What about small gassers? or even down to 1.20 or smaller birds?
It's actually fairly simple to establish the value of them for models.
With most of our popular, mass produced models, there will be one servo that is strong enough to drive one aileron. When we increase the size of that aileron beyond that requirement, the booster tab makes sense.
As for how small is the limit? We got servos for everything up to the big birds.
If you can drive all the surfaces with one servo each, that's the boundary.
I've never understood why there were and are so many, many big models that have 2, 3, and 4 servos on a tray driving just one rudder. And why so many elevators have 4 or ailerons use 4 or 6. Guess the manufacturers figure they sell more airplanes for 10-15% less to people who don't know there is a way the big bird they're buying could take 6 or 8 less servos.
10-05-2007 | 11:58 AM
#32
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From: Woodville, WI
RE: How do they do that????
ORIGINAL: da Rock
It's actually fairly simple to establish the value of them for models.
With most of our popular, mass produced models, there will be one servo that is strong enough to drive one aileron. When we increase the size of that aileron beyond that requirement, the booster tab makes sense.
As for how small is the limit? We got servos for everything up to the big birds.
If you can drive all the surfaces with one servo each, that's the boundary.
I've never understood why there were and are so many, many big models that have 2, 3, and 4 servos on a tray driving just one rudder. And why so many elevators have 4 or ailerons use 4 or 6. Guess the manufacturers figure they sell more airplanes for 10-15% less to people who don't know there is a way the big bird they're buying could take 6 or 8 less servos.
ORIGINAL: vmsguy
I wonder if there's a practical size limit to using boost tabs.
By that I mean, when is a control surface (and by inference the plane) too small to make boost tabs not worth it.
Would a 1/4 scale be too small? 1/5? 1/6? What about small gassers? or even down to 1.20 or smaller birds?
I wonder if there's a practical size limit to using boost tabs.
By that I mean, when is a control surface (and by inference the plane) too small to make boost tabs not worth it.
Would a 1/4 scale be too small? 1/5? 1/6? What about small gassers? or even down to 1.20 or smaller birds?
It's actually fairly simple to establish the value of them for models.
With most of our popular, mass produced models, there will be one servo that is strong enough to drive one aileron. When we increase the size of that aileron beyond that requirement, the booster tab makes sense.
As for how small is the limit? We got servos for everything up to the big birds.
If you can drive all the surfaces with one servo each, that's the boundary.
I've never understood why there were and are so many, many big models that have 2, 3, and 4 servos on a tray driving just one rudder. And why so many elevators have 4 or ailerons use 4 or 6. Guess the manufacturers figure they sell more airplanes for 10-15% less to people who don't know there is a way the big bird they're buying could take 6 or 8 less servos.
I was thinking from an aerodynamic perspective. Can a smaller model gain agility with boost tabs without have to increase control surface size?
For example, can a big ol' trainer, that should really have a larger rudder area, gain rudder authority by just adding a boost tab to the rudder? Thus eliminating the need for possibly extensive modifications.
10-05-2007 | 01:02 PM
#33
RE: How do they do that????
ORIGINAL: vmsguy
I was thinking from an aerodynamic perspective. Can a smaller model gain agility with boost tabs without have to increase control surface size?
For example, can a big ol' trainer, that should really have a larger rudder area, gain rudder authority by just adding a boost tab to the rudder? Thus eliminating the need for possibly extensive modifications.
ORIGINAL: da Rock
It's actually fairly simple to establish the value of them for models.
With most of our popular, mass produced models, there will be one servo that is strong enough to drive one aileron. When we increase the size of that aileron beyond that requirement, the booster tab makes sense.
As for how small is the limit? We got servos for everything up to the big birds.
If you can drive all the surfaces with one servo each, that's the boundary.
I've never understood why there were and are so many, many big models that have 2, 3, and 4 servos on a tray driving just one rudder. And why so many elevators have 4 or ailerons use 4 or 6. Guess the manufacturers figure they sell more airplanes for 10-15% less to people who don't know there is a way the big bird they're buying could take 6 or 8 less servos.
ORIGINAL: vmsguy
I wonder if there's a practical size limit to using boost tabs.
By that I mean, when is a control surface (and by inference the plane) too small to make boost tabs not worth it.
Would a 1/4 scale be too small? 1/5? 1/6? What about small gassers? or even down to 1.20 or smaller birds?
I wonder if there's a practical size limit to using boost tabs.
By that I mean, when is a control surface (and by inference the plane) too small to make boost tabs not worth it.
Would a 1/4 scale be too small? 1/5? 1/6? What about small gassers? or even down to 1.20 or smaller birds?
It's actually fairly simple to establish the value of them for models.
With most of our popular, mass produced models, there will be one servo that is strong enough to drive one aileron. When we increase the size of that aileron beyond that requirement, the booster tab makes sense.
As for how small is the limit? We got servos for everything up to the big birds.
If you can drive all the surfaces with one servo each, that's the boundary.
I've never understood why there were and are so many, many big models that have 2, 3, and 4 servos on a tray driving just one rudder. And why so many elevators have 4 or ailerons use 4 or 6. Guess the manufacturers figure they sell more airplanes for 10-15% less to people who don't know there is a way the big bird they're buying could take 6 or 8 less servos.
I was thinking from an aerodynamic perspective. Can a smaller model gain agility with boost tabs without have to increase control surface size?
For example, can a big ol' trainer, that should really have a larger rudder area, gain rudder authority by just adding a boost tab to the rudder? Thus eliminating the need for possibly extensive modifications.
10-05-2007 | 08:10 PM
#36
RE: How do they do that????
ORIGINAL: vmsguy
I wonder if there's a practical size limit to using boost tabs.
By that I mean, when is a control surface (and by inference the plane) too small to make boost tabs not worth it.
Would a 1/4 scale be too small? 1/5? 1/6? What about small gassers? or even down to 1.20 or smaller birds?
I wonder if there's a practical size limit to using boost tabs.
By that I mean, when is a control surface (and by inference the plane) too small to make boost tabs not worth it.
Would a 1/4 scale be too small? 1/5? 1/6? What about small gassers? or even down to 1.20 or smaller birds?
As I said, I use a boost tab that looks like the scale trim tab on the rudder of my scale WACO's. It works, and I can use a reasonable servo. If you are doing anything of at least a normal .40 size it will work fine too. In fact, you could use them on a 1/2A size. I wouldn't expect for them to have much value on the typical park flyer, due to the lack of speed with one of these. Air flow is the necessary force required for them to be effective.Bill, AMA 4720
WACO Brotherhood #1
