I am currently building a Big Bird from Skybench, and I'm contemplating the type of spoiler setup I want. Which type would you recommend, the string pull type, or one where there are two servos, directly controlling each spoiler? The glider has a 100" wingspan, and I won't be using it for compititions, just on a lazy Sunday afternoon.

I'd go with the 2 microservos directly at the spoilers.
Easier to adjust, easier to assemble the plane at the field, and the weight penalty is minimal.
Make that almost "non-existent"..

I just checked on Skybenchs's website, the Big Bird has 820 sq.in wing area, and Skybench states a flying weight of 42 oz with spoilers, which gives you a wing loading of
7.4 oz/sqft.
Suppose that is with a single Hitec HS-85BB for the spoilers, if you install 2 spoiler servos ( HS-85's at .77 oz ea) you total weight will go from 42 oz to 43 oz, with the additional wiring.
Your wing loading will be 7.55 oz/sqft....
I have never understood why people subject themselves the the hassle of hooking up the spoilers to a single central servo, with the strings or whateverfor such a minimal weight saving.

Thanks for the reply MTT

I planned to use two micro servos (hitec), one for each spoiler, when I got the kit, I guess I over analyze things, and just wanted a second opinion...

It's easier to hook two lines over a servo arm in the fuse than it is to plug in one or even two servos to a harness. Also you don't start breaking the wires in the conectors with just the lines.

I leave the retaining screw out of the servo arm and tie the lines to the arm. The lines and arm come off with the wings. Have yet to have an arm come off of a spoiler servo.

In some cases I will use small servos (smaller than the metal gear 85's) at each spoiler blade but mostly for retro fits where it's impossible to route the lines/tubes. I also use a different connector (AMP) for the connection.

I have two RES sailplanes.

My Spirit has the servos in the wings, in the spoiler bays. They are no name servos about the size of hs-55s. They work fine, but I had a lot of trouble getting them even until I moved the plane over to a comptuer radio and put them on separate channels. Because the arms are small, they only open to aobut 45 degrees, but they work fine. I may try to put different arms on them to get more lift of the spoiler, but so far it has not been worth the trouble.

My Sagitta 600 has a single HS-81 in the fuse to pull strings to the spoilers. Frankly I found this easier to set up and easier to adjust. Pretty simple to attach them at the field. No need for a computer radio to help adjust the left and right spoilers.

With a servo in the spoiler bay, if you use osme kind of control horn system to directly connected to the spoiler, the spoilers are positively locked down on launch. The strings don't hold the spoilers down but under normal flight they don't seem to come up. there is a 1/4 oz weight on each spoiler keep it down and to help it close.

If you plan to do a lot of inverted flight or loops, I would go with servos in the spoiler bays directly connected to the spoilers. Otherwise, I would do the strings.

If you are doing an ARF, it will be easier with the strings as the tube they put in the wing is usually not large enough to pass the wires easily.

Good luck whatever you do.

I have a two servo setup on my Skybench Astro Jeff that I am building. If you would like pictures e-mail me with the ok. Loran

hi chocks, i have a maurauder and the spoilers are opened with a string from one serve in the center of the wing so you only have one wire to plug in. i am just building it but i think it will work ok. the only problem is the holes for the spoiler line tube which goes through the small part of the ribs. look at mm glider tech and you can get a picture.