40% Turbo Laser (scratch built)

[forgues research]

	Quote: Originally Posted by BTerry
	In summary boost tabs just add an additional ROTATIONAL force to the control surface IN THE SAME DIRECTION AS THE SERVO FORCE. This reduces the force requried of the servo. Good thing, n'est pas? Canwe please put this to bed and get back to the Laser build without distractions? Thank you again Roger for an insightful build. plus ca change, plus c'est la meme chose.

Mais alors vous parlez francais???

[BTerry]

	Quote: Originally Posted by forgues research
	When I was doing knife edge passes at full power with my 35% yak, the rudder was controlled by the boost tab only which had a hitec HS 81 servos controlling the boost tab. No other servo input on the rudder . Roger

Technically (as you explained many, many times before in your writeup) that was a "control tab" and not a boost tab, but it very good example of the force multiplier effect of a tab assist setup.

[BTerry]

	Quote: Originally Posted by forgues research
	Mais alors vous parlez francais???

Je parle un peu de français (mal), mais beaucoup de Chinois (Mandarin).

Oh yes, and some Engrish too. Not too bad for an American of Irish/Swiss/English/Danish/Norse extraction...

[BTerry]

Roger, did you experience any hysteresis on the Yak rudder?

	Quote:
	but it very good example of the force multiplier effect of a tab assist setup.

I should clarify this term "force multiplier". I dont' want to take the time to make a drawing, sorry. Also I forgot to mention the servo torque calculator used a 1" servo and control horn to non-dimensionalize the torque force (this is important). Also the calculator had the built-in safety factor of 50%, so the actual values would be 66% of those I show with the safety factor removed. I will leave the safety factor in the calculation for continuity.

As I stated before the surface requires a certain rotational moment (torque) to move a control surface to a certain angle at a certain speed, and this can be calculated with moderate accuracy. We can also calculate the force generated by a boost tab deflected in the opposite direction of the original control surface. This force acts about the centroid of the control surface, and the torque is derived from this number. The torque required will be the force (F) acting on the surface times the radial distance from the hinge line (r) when looking at a cross=section. T=Fxr. This is the defnintion of torque.

The multiplier effect comes from the increase in the radial arm, (r), of the boost tab when compared to the control surface itself. Back to my example control surface above, the dimensions are 40" x 4" so say it is an aileron. The "centroid" would be located 2" aft of the hinge and 20" from each end, right exactly in the center. Imagine we have one single servo attached to a control horn with the connection point vertically centered on the hinge line.

The force acting through this centroid times the distance from the centroid to the hinge line (2"). So the force required to hold the surface in position will be Torque/2", or half the torque number.

Now add a 10% boost tab to the surface. For simplicity sake make the dimensions 1.5" x 10", this is close enough (9.37%). Again for simplicity assume the boost tab deflects to the same angle as the control surface, just in the opposite direction. Using the torque values above we can calculate the force exerted on the boost tab.

speed: 50 mph
angle: 45*
torque: 235 oz*in

The linear force applied through the centroid of the control surface. Again we are using a 1" control horn, so for a torque of 235 oz*in we have a pushrod force of 235 oz. Now the air force acts through the centroid to generate the torque, so the actual force on the surface is 235/2=117.5 oz. Remember this number for a minute.

Now if we take 10% of the surface and deflect it in the opposite direction and get:

speed: 50 mph
angle: 45*
torque: 8.31 oz*in

The force acting through the centroid of the boost tab is again the force/radius = 8.31 oz*in/.75" = 11.08 oz. However, this is the torque about the boost tab hinge line. Here is the multiplier effect. The CENTROID of the boost tab is located 0.75" aft of the boost tab hinge line, or 4"(control surface chord) - 1.5"(boost tab chord) + .75"(centroid of BT) = 3.25" AFT of the control surface hinge line.

Now back to the torque calculation. At 50 mph and with a deflection of 45* the control surface requires 235 oz*in to deflect. The boost tab contributes 11.08 oz x 3.25" = 36 oz*in of torque force to the surface, reducing the load on the servo by the same amount.

This is 36/235 = 0.15, or 15% of the total required torque. This may not seem like much, but if the servos are approaching their maximum load this may be enough to pull them back into a range of higher efficiency.

Run the numbers again at 100 mph and the tab adds 107.25 oz*in torque to a surface that required 940.8 oz*in to deflect. This is not an insignificant amount! Basically it adds 1/8 of the total torque required to deflect the surface.

[BTerry]

Actually I neglected to remove the surface area of the boost tab from the calculation. So the numbers above should be 211.5/36 = 17%, and 846.7/107.25 = 13%.

If we lengthen the boost tabs (chordwise) so they extend aft of the trailing edge of the control surface, this multiplier effect will increase because the centroid of the boost tab will be even farther aft of the control surface hinge line, so the radius of rotation (r) for the torque calculation will INCREASE, giving us an even larger boost effect.

Also changing the dimensions can greatly change the total boost effect. This is very important! Proper dimensions can add anywhere from 10% to 30% or more boost (as much as you want) with only a few minutes of calculations.

Does this make sense to everybody? I hope this puts an end to all the negativity.

[BTerry]

	Quote: Originally Posted by jack strickland
	The 3d stuff Ive seen approach those perameters without 900 in oz servos. There may be a little more involved here. Not trying to be negative, just want to learn.

Sorry, that is with the 50% safety factor included. The actual torque to hold the surface is not 940.8 but 627.2 oz*in (940.8/1.5).

[forgues research]

Here is a video on the gound , not sure if it got loaded up

Here is U tube

YouTube - GEDC0062

Roger

[danielgpr]

	Quote: Originally Posted by forgues research
	Here is a video on the gound , not sure if it got loaded up Roger

So the boost tab on this plane is fixed and assisting a servo on a pull-pull setup?
Dan

[BTerry]

	Quote: Originally Posted by danielgpr
	So the boost tab on this plane is fixed and assisting a servo on a pull-pull setup? Dan

Yes. The control surface is moved by a pushrod attached to the servo, and the boost tab is moved by a control rod attached to the wing/horizontal stab/fuselage.

[PDK]

	Quote: Originally Posted by danielgpr
	Ok, cool. There are small enough cameras out there to mount on flight surfaces that wont damage plane and could show it in action though. Dan

Mate come on. Be realistic. The whole purpose of Rogers threads was to explain the principle of boost tabs. He has stated that countless times. He is not trying to convert anyone. Some have done everything bar directly call Roger a liar. I don't believe he has to prove anything. It is up to us to take the principle and see if it is suitable for our own aircraft and flying style. He does not fly 3d so of course cannot supply a 3d video (I posted a flight in 151).

To be honest the "obligation rests with the Prosecution". If you don't believe, then I propose you do some testing in a 3D situation. My suggestion is that someone starts their own thread to discuss and personally TEST a boost tab setup for 3D flight. Sure you are worried about cutting up a $$$$ plane, but surely someone has a hack that they can do some testing with. A simple boost tab as an extension of the current control surface should be ample. I would run a data logger and monitor the current draw of the servos (Maybe an eagletree. Not sure the sample rate will suit) which should be reasonably proportional to the aerodynamic force exerted on the surface (again test this assumption).

Then, you can test fly with the boost tab connected to the surface (i.e. disabled) and then fly with the boost tab connected correctly. With a bit of luck you will be able to measure the reduction in servo load (or otherwise?). Looking forward to your thread........

	Quote: Originally Posted by BTerry
	Roger, did you experience any hysteresis on the Yak rudder? I should clarify this term "force multiplier". I dont' want to take the time to make a drawing, sorry. Also I forgot to mention the servo torque calculator used a 1" servo and control horn to non-dimensionalize the torque force (this is important). Also the calculator had the built-in safety factor of 50%, so the actual values would be 66% of those I show with the safety factor removed. I will leave the safety factor in the calculation for continuity. Etc, Etc, Etc, Etc

Great info. Thanks.

Anyway back to the usual programming!!!
Roger. When you get the wing tube can you please post some details of the wing sockets.

Regards
Phil

[forgues research]

	Quote: Originally Posted by PDK
	Mate come on. Be realistic. The whole purpose of Rogers threads was to explain the principle of boost tabs. He has stated that countless times. He is not trying to convert anyone. Some have done everything bar directly call Roger a liar. I don't believe he has to prove anything. It is up to us to take the principle and see if it is suitable for our own aircraft and flying style. He does not fly 3d so of course cannot supply a 3d video (I posted a flight in 151). To be honest the "obligation rests with the Prosecution". If you don't believe, then I propose you do some testing in a 3D situation. My suggestion is that someone starts their own thread to discuss and personally TEST a boost tab setup for 3D flight. Sure you are worried about cutting up a $$$$ plane, but surely someone has a hack that they can do some testing with. A simple boost tab as an extension of the current control surface should be ample. I would run a data logger and monitor the current draw of the servos (Maybe an eagletree. Not sure the sample rate will suit) which should be reasonably proportional to the aerodynamic force exerted on the surface (again test this assumption). Then, you can test fly with the boost tab connected to the surface (i.e. disabled) and then fly with the boost tab connected correctly. With a bit of luck you will be able to measure the reduction in servo load (or otherwise?). Looking forward to your thread........ Great info. Thanks. Anyway back to the usual programming!!! Roger. When you get the wing tube can you please post some details of the wing sockets. Regards Phil

Phil,
The tubes are on the way, so as soon as I do the sockets I will take many photos and explain as I go forward, and since I have done this on the 34% , I will do the same on the 40%.

Roger

[PDK]

Thanks Roger. Sorry I haven't seen the 34% thread. Will look over there if it has already been done.

Regards
Phil

[forgues research]

	Quote: Originally Posted by PDK
	Thanks Roger. Sorry I haven't seen the 34% thread. Will look over there if it has already been done. Regards Phil

No worries Phil, I didn't have that many good pictures on the 34% so will try harder this time.
By the way, I do want to give credit to where its due, and Jack Strickland , is the one that showed me how to do it, and you can get the plans of either the 34% or the 40% from Jack, not expensive and easy to build.

Roger

[SmoothFlying]

	Quote: Originally Posted by danielgpr
	So the boost tab on this plane is fixed and assisting a servo on a pull-pull setup? Dan

Exactly!!! This is why we say Roger and his counterpart are just full of BS. They keep saying each surface is controlled by some foamy servo and then clearly tell on themselves when a video clearly shows a pull pull system with the boost tab is fixed and assisting the servo on pull pull. Also the other surfaces are rigged the same way. Roger you are full of BS, that is why your POS thread got shutdown. Not for folks flaming at you but because you dont show proof and when you do its the direct opposite. "Oh just believe me, I have 20 years of experience doing this". The system you show in the video will work. I believe that. But thats not what you say about all your applications. Now dont turn into a little girl and call on the mod's to redirect this thread because they'll see you are full of BS. I'm just waiting for this "40% Turbo Laser" to be shutdown.

Hey guess what fellas, my real name is Hugh Hefner. I am actually typing this from my laptop in the Grotto. No you cant have any pictures of all these beautiful women down here with me. Just believe me, I am having a ton of fun. I'll talk more about the experience later in the mansion.

[forgues research]

While waiting for the wing tubes, I started making the tail wire hardware and thought I would show the procedures I am using.

First I start off with a 5mm aluminum screw, then follow the pictures.

Now I will make the other parts such as the clevis's and will follow with more pictures.

Roger