Four Star 40 Question
 

I'm building a Four* getting closer and closer to being done, (It's my first kit).

I'm trying to figure out how to mount my aileron servo. The Fuse servos were a piece of cake because of the servo tray that came with my radio system, but I'm not quite sure what exactly is the correct way to mount one in the hole in the wing.

Anybody with a 4* have a picture of how they mounted theirs?

(Also posted in the kit-building forum)

RE: Four Star 40 Question
 

The aileron servo is mounted by cutting a hole in the center of the wing, behind the spar. DON'T CUT THE SPAR!

You dig out part of the wing ribs at center to let the seve slide down.

The sevo top sticks out of the wing.

scrap ply (or the pre-cut ply pieces..) are epoxied to the wing and drilled for the servo mounting screws.

Read the directions in the booklet... shows it quite well.:eek:

***

On my 4*40... I opened the hole a bit wider than "normal" and stuck in 2 servos side by side, using one for each aileron. this allowed me to computer-mix flaperon function ( 10% flap, 90% aileron) to trim the ailerons. For my plane I found that the aileron alignment guide had my ailerons drooped just a little from where the airplane flew perfectly.

RE: Four Star 40 Question
 

I looked all over in the book, couldn't find an answer. Everything else about this plane is very well documented, and maybe I just missed that part.

I've got the wing ribs cut out (as the directions say to do), but after using the template that was provided the hole is big enough to let the whole servo fall into the hole, not just the bottom part. That was the source of my confusion, I couldn't find anything about what I should be mounting it to.

RE: Four Star 40 Question
 

I built my 4*40 with one servo for each aileron rather than a centrally mounted servo driving both ailerons. This makes the plane more responsive in roll, is very easy to do, and only has the weight penalty of the extra servo; it also allows you to set up flaperons if your radio allows. You will find a ton of advice here on how to do this if you search for "dual aileron servos", and I'll be glad to help if you email me. The basic idea is to install each servo on a plywood hatch cover that will go in the rib bay in front of the center of the aileron, and bring both servo leads out to the center of the wing, where you will either connect them to the receiver through a y-harness or to two separate channels, depending on your radio's characteristics. As for the hatch itself, it's easy enough to build your own, but there are some ready-made units as well.

If you don't want to modify the kit for dual aileron servos, the procedure for installing the central servo would be: make sure your servo will fit in the mount before assembling it, making provisions for clearing the side where the wires exit the case (you want a small clearance all around rather than a snug fit); CA 1/8" strips of plywood under the mount (i.e. on the opposite side of where the screw heads will go) so that the screws will have something to bite into and so won't work themselves loose from vibration or stress; dry-fit the servo mount on the wing to ensure that the pieces fit and sit well against each other; finally, glue the mount together and to the wing with 30 minute epoxy.

On a separate subject, the 4*40 is notoriously week in the tail area, particularly the area where the vertical fin meets the fuselage. It would be a good idea to reinforce this area with fiberglass prior to covering, and to install the "optional" fillets in the fin/stab joints.

Good luck,

Juan M. Villaveces

RE: Four Star 40 Question
 

There should be 2 pieces of ply about 1/4 wide 1/16 thick and 3/4 to 1 inch long. those are the supplied servo rails for the aileron. epoxy in place to support the servo. Drill the holes and screw the servo in place.

for radio installation... remove all servo arms from the servos. plug them all in the correct channels and then turn on the radio system. Set the rim levers (or computer trims) to centered.

Now you can adjust things.

RE: Four Star 40 Question
 

Look in your bag of small bulsa peices for a rectangle piece that seems to fit nice over the hole in the wing.

Cut away "ONLY" the covering away from the hole in the wing.

Now CA/Glew the rectangle piece onto the wing.

Now you have a mount for the servo, just screw it into place.

There is a picture of it in the book. If you need another just let me know and I will try to post one.


Tom
Pearl Harbor HI

RE: Four Star 40 Question
 

Thanks guys.. I think I got a working solution. Still couldn't ever find anything in the manual, but I managed with what you guys said in the thread and some scrap plywood.

Thanks for the suggestion about the vertical fin.. I think I'll definately be putting those braces in now.

Here's a related question just for curiosity's sake:

The hole in the wing is only about half a centimeter short of being able to fit two servos in there instead of one. A couple of you guys mentioned that you're are running independant servos for their ailerons. Is there an advantage to having the servos mounted in one place instead of the other? (like one centered on each wing half in a hatch like condor mentioned, or both side by side in the middle like FHHuber? Or is it just a preference thing?

I was just thinking that it would be very simple to add a 2nd servo later if I wanted by moving the one that's in there over to the side, and cutting the hole just a tiny bit bigger.

RE: Four Star 40 Question
 

This is just my opinion. Two servos in the center section are better than one out on each wing, as long as putting them in doesn't weaken the center section too much. Servos in the wing act like a barbell: hard to start rolling, hard to stop. If their weight is in the center, the moment arm is shorter, therefore the plane responds better. OTOH, the key advantage of servos in the wing is short, slop-free linkages, so the advantages of moving them to the center will really apply only if you can maintain the same kind of linkage "authority"; in a plane as small as the 4*40, I'd say go for the center.

Just my .02... I hope it's useful to you.

Juan M. Villaveces

RE: Four Star 40 Question
 

I just built one.

Its not actually spelled out in the manual, but if you look at the drawing it shows how its done.

Wings

RE: Four Star 40 Question
 

The whole reason I put 2 servos in the center rather than out in the wing bays... it was EASIER.

Out in the bays will spread the mass out a bit... this takes a little load off the center joint in HARD pull-outs. Might be the difference between the wing surviving or snapping in half. (mighty hard pull to snap the 4*40 wing... like... 30 G's or so.) The mass being spread also has an effec on rolls... slows the rotational acceleration of the model. Max roll rate is the same... but it takes longer (or mofe aileron deflection) to get it rolling and longer (or more opposite aileron) to stop the roll.

The mass of a standard servo... not going to be a HUGE effect on either count... but it is there.

If you have the spare servo... go ahead and drop it in. If you place the servos right... youcan use the center 4 screw holes for a single servo... or all 8 scre holes for 2 servos. then you can play and see which you like better. ;) (I eventually went back to one servo... after finding the ideal neutral angle for my ailerons.)

RE: Four Star 40 Question
 

Cool, thanks guys.. I'll give it a shot.