Boost Tabs for servo help
 

I have been using Boost Tabs on all of the control surfaces of my aerobatic aircraft to help out the servos. Which means you can use smaller servos to the job of normally large servos.
I was wondering if anybody else use these. I can tell you they are very effective..

Boost Tabs
 

That is such a coincidence. I was just out at an airport (full size) and saw a experimental Bi-Plane with those little add-ons. I asked about them and a pilot said they help, but not sure if they were worth it. (on a full size plane, that is)

I wanted to try and install them on one of my RC planes and see what happened. Did you design them yourself? Or does someone sell them.

mike

Boost Tabs for servo help
 

I use tabs also. Very affective. Getting the throw is the most delicate part. Not enough ,and they dont do anything. To much and the servo has a hard time pulling the control back to neutral. Patty Wagstaff wouldnt have enough muscle without the spade tabs.

Boost Tabs
 

I made my own. Not very hard to make but in this day and age where everything and its Grandmother is ARF, I can understand the apprehantion.
Read on my web site. http://www.geocities.com/roger_forgues/Boost-tabs.html

Boost Tabs for servo help
 

I've done this quite often. Yes, they let a smaller (less powerful) servo do a big job. I did find that you want to limit the size to 10% of the moveable surface area though or you will get hunting around neutral. I seem to have best results when the tab always stay in line with the neutral position. This is easy, just make the distance from the horn to the pivot points equal at both the fixed and the moveable horn. On excessively large surfaces, it also helps to statically or mass balance the moveable surface, especially on ailerons or a hard landing can cause the excessive momentum of the large surfaces to strip the aileron gears.

Boost tabs
 

You can see here where they are in the elevator and the elevators where balanced.

http://www.geocities.com/roger_forgues/test.html

Boost Tabs for servo help
 

I am using active boost tabs on My HOB Extra 300L. They seem to work very well, the Plane is extremely responsive, Basically like power steering.

Boost tabs
 

Nice installation. Now that I see yours, I wish I would have made mine another color also.

For the boost tab clevises and such, I use 1/2a material to keep it light and the push rods, I use 0.080 " aluminum welding rods. They are very light. You want to keep things light in that area.

Boost Tabs for servo help
 

I haven't done a lot of experimenting with my settings yet, I'm still getting used to the sensitivity, Once I'm more comfortable I will try fooling around with different settings

Boost Tabs for servo help
 

If I may, I did notice that you might have too much throw in the boost tabs. Just my opinion. Normally, it is suggested to have only 30% throw on the boost tabs versus the actual control throw.
Too much throw, might make it hard to trim since its boosting too much and it wants to keep searching for center.

Boost Tabs for servo help
 

Thanks for the input, maybe I'll tone it down a bit, It is pretty touchy

Boost Tabs for servo help
 

On my old Groundpounder they are 10% of the aileron area also. At full aileron deflection the tab is about parallel with the wing chord line.

Boost Tabs for servo help
 

I have not experimented with different amounts of throw. I've set all mine up so that the trim tab stays parallel with the main surface no matter how much deflection. This give no feedback at neautral yet max at max throw. It is also easy to set up, just make the length of both the fixed and moveable horn identical.

Boost Tabs for servo help
 

That's basically what I have, Is yours fairly sensitive. What type of aircraft is it on?

Boost Tabs for servo help
 

On which controls do you use Boost Tabs, and I would like to see pictures if you can.

Boost Tabs for servo help
 

I have tabs on each aileron and on the Rudder. I built the rudder oversize so I was a bit worried I might have overdone it, so I built a tab on it. The Elevators would have required two tabs due to the split design, and I didn't want too much weight in the tailso I didn't put them on. I don't know if you can see in the attached photo, the linkage for the rudder

tabs
 

I can see a bit, looks like a nice installation.

Boost Tabs for servo help
 

I wrote the article that Roger refers to.
http://www.geocities.com/roger_forgues/Boost-tabs.html
"Labor Saving Devices for Overworked Servos, by Carl Risteen. It is still in print, in Air Age's "How-To's, Vol. 2. One nice thing about boost tabs is that they can serve as ground-adjustable trim tabs, to help trim out those inevitable small misalignments and warps. These show up in the form of a model that is in trim over only a narrow speed range. Trim it at half power, and it goes out of trim at full power, and vice versa. I am sold on trim tabs, and frequently use them with a linkage that makes them perform as boost tabs as well. I find that boost tabs can lighten servo load by up to about 85%, before non-linearity gets objectionable. I set their travel quite low at first, and gradually increase travel until I get just enough boost to do the job - too much can be very bad, forcing the servo to work in reverse, trying to restrain the control surface from deflecting on its own. The usual evidence of this is that the model refuses to trim out, due to linkage slop allowing the control surface to move a bit off center in each direction.

Boost Tabs for servo help
 

Your article in "Air Age How To" was excellent, and was the reason I tried the boost tabs, I have also included boost tabs on my Super Chipmunk during it's rebuild. It is quite a bit more responsive now than before. Thanks for the idea's

Boost Tabs for servo help
 

Carl,
I have put your name as the author, as I didn't know it was you that wrote this, Someone pointed this out so I put it in.
Very good article, thanks for writing it.