Aileron servo mounting

[Dove from above]

This is my first build a "funfly" and the wing is almost done. There was some info on the construction but none on the servo install/mounting for wing and fuse.

I realise I will need to use some rails to bridge the 2 ribs and sheet/cap around this are for the covering to attach to BUT I do not know how to position the servo.

I do not know how to pick where for and aft AND how high it should be. Do the 2 questions depend on the shape of the wing even?

I have included a "mock up" using the end cap rib and a scrap to replicate the aileron.

Also I think the servo can go top OR bottom,again I do not know which would be better.

Linkage wise I will stay away from Z bends and use small ball links or crevices.

Hope all the info needed is inc.

[Martin_K]

From me only questions, not answers.

Do you intend the servo horn to be outside the wing, or inside the wing with pushrod emerging through a hole in the sheeting/covering?

Do you intend the servo to be oriented with it's horn parallel to the wing, probably if a 'standard' servo, or with servo horn perpendicular to wing, probably if thin 'wing' servo?

[Steven S]

When I built my first plane I found this article and have followed OPTION 2 on all my builds

Aileron Servo mtg

Edited By Steven Shaw on 06/10/2019 15:27:02

[Denis Watkins]

Single servo for both ailerons, or dual servo, one each side

[kc]

There are several ways of fixing the servos 'on their side' including these -

1. is to wrap 3 layers of masking tape around the servo body and epoxy the masking tape down onto the ply plate. If the servo needs changing the masking tape is cut away. I have not used this method but it was shown in an article by Sid King in RCModelWorld a few years ago and seems worthwhile and cheap.

2. To be able to screw the servo down use these mounts from SLEC ( also by RadioActive ) These are shown in some Peter Miller designs.   Note that the SLEC photo shows them as bought and not separated from the 'sprue'  also despite the name single it looks like a set for 2 servos.  The Radio Active catalogue has a better drawing which shows how they are used.

 

Edited By kc on 06/10/2019 16:35:13

[Steven S]

I bought some of these from Banggood, but the slot are way too narrow for my servo mounting tabs, otherwise they are very nice and I plan on modifying them or the mounting tabs for another project.

[Dove from above]

Posted by Martin_K on 06/10/2019 14:55:35:

From me only questions, not answers.

Do you intend the servo horn to be outside the wing, or inside the wing with pushrod emerging through a hole in the sheeting/covering?

Do you intend the servo to be oriented with it's horn parallel to the wing, probably if a 'standard' servo, or with servo horn perpendicular to wing, probably if thin 'wing' servo?

Hi Martin, my reply to both of these would be, don't know, what would suit the type of wing I have best?

I have seen a similar model and the servo was mounted much like denis`s first picture but 1 servo per wing.

If I was to go with that setup,how do I work out the correct height and for/aft placement. if the height depends on the linkage run/position given the curve of rib,how do I work that out? I would hate to to do the rails etc only to find the linkages rod were fouling

[Martin_K]

I can't tell you what is 'best'. My intention was to encourage you to consider the options.

Denis's first picture is probably the simplest. I would be happy to go with that, you may want a sleeker look.

As for the setup, do the plans give no suggestions? I would think about what throw (range of movement) is desired on the aileron and try and work back from that. Then pick servo and aileron horns of an appropriate length to avoid interference with the wing and adjust the 'gearing' of the levers.

I do use z-bends in my pushrods, and make them up to the desired length. Easy to cut out another piece of piano wire if the result is not good. If you prefer screw adjustable fittings go with that. There is no ideal method.

[Dove from above]

With regards to wing profile and it uses a undercarriage, would you mount servo on top or bottom?

[kc]

First of all if you state the exact model you are building it will help.

I presume you mean by " 1 servo per wing" = 1 servo for the left wing and another for the right

If you do mean that then note that the servo arms point in opposite directions if using a Y lead for the 2 servos. ( right aileron must go up when left goes down! )

Normally the servo goes in the thicker part of the wing and needs to just clear the surface with the servo arm allowing for the thickness of the clevis or Z bend. The aileron horn will stick up enough so that the rod does not foul the ribs. Positioning the servo is not very critical but mounting it just behind the spar would seem normal.

[kc]

Servos are normally mounted underneath for neatness.

[kc]

This photo shows the underside of a wing with cutouts for servos - note the thin string to pull the servo leads through after covering wing and the outlet holes into fuselage. ( masking tape holds the string so it does not disappear). What you cannot see is the paper tubes to guide servo leads - tubes were inserted at an early stage iin the building! You could build in extension leads but note the plug and socket must be securely fixed together so they don't pull apart.

Edited By kc on 06/10/2019 20:01:07

[Martin McIntosh]

For a fun fly I would say that the method used by Dennis is the easiest. Even many scale models, including my own, use this. The thin wing ones are made for ailerons but require mounting on a screw in plate. I`m afraid that you just have to work out the depth of the rails for a given model and build a box round them if needed. A good starting point is 1/4" balsa capped with 1/16" ply for them.

If you can find any of my build blogs or photo albums they show quite a lot, the most recent being the Fieseler Storch.

[Martin_K]

By "funfly" I am imagining something that is going to be doing multiple short flights, possibly with low level aerobatics, touch and go, etc. It follows from that prettiness, if it has any to start with, may be short lived. Exposed servos no problem there. For a soaring glider I would want something different.

The wing profile looks nearly symmetrical but the convention of the pushrods exiting the bottom of the wing sounds O.K. as you say the plane has undercarriage. If you were belly landing on rough grass you could make a case for the servos and horns being on top of the wings. Would probably still get vegetation jammed between the fixed and moving surfaces however, which happens to me all the time!

[Dove from above]

Thanks guys, I am not a forward planner so have not even got any linkage stuff yet, not looked at aileron horn types etc.

I don't know if I should wait and get all the stuff then do a layout OR just get on with making the servo rails and capping, going with the height being all of the servo horn showing. servo standing up,not flat on side.

[Nigel R]

Going by that really thick wing section, this is something that I would personally mount the servo upright in, just as you say. No hatch. Just leave a servo sized hole, with the rails close enough to the surface, so that the entire servo horn is above the wing surface. You can get the servo mounted right away and sort the pushrod later.

I would absolutely use a Z bend at the servo end - get a pair of Z bend pliers, it makes it easy - as they will not bind when the servo rotates, this could be important on a funfly with 45 or 60 degrees of movement. Also no danger of anything coming undone or slipping etc. Other end of pushrod, metal threaded clevises.

[kc]

A bit of forward planning saves messing up a nice model later just to fit the essential parts. For the servo arm to fit it needs the bush to clear the surface which then allows enough clearance for a metal clevis to fit. Plastic clevis can be fatter and some need clearance for the split pin too.

When building a wing for wing servos it's important to build-in a way to get the servo leads through. As we don't know what model you are building and therefore the scale of the photo you show it's difficult to say for certain but it appears that the holes already there may not take the plug fitted on a servo lead.

A Futaba type servo plug needs a 9.5mm wide hole , while a non Futaba without the extra tongue needs 8.5 mm. The socket on an extension lead needs a 12mm hole. Using plain wire and crimping a connector on when inside the wing  is not something most of us want to do!

Edited By kc on 07/10/2019 11:13:58

[Dove from above]

KC, I did make a woopsie on the rib holes. I forgot to enlarge the inboard ones. Rather than make a bad job trying to enlarge them I intend to have the hassle of taking the plugs off then thread. I know its a faff but I like extra unnecessary work : )

[kc]

Crimping the servo plugs requires a crimping tool and needs to be done well. Cutting the servo extension wire (not at the very end ) and resoldering the wires would be easier. But I would suggest cutting an access hole in the sheeting and some hacking at the holes with a scalpel to let the plugs just pass through would be safer! Cutting an access hatch with the scalpel held at about 45 degrees to mitre the sides would enable a hatch to be replaced easily. ( the same technique as used to repair damaged wing sheeting )

In the photo I showed the very thin strings were passed thro by tying a weight ( bolt actually) to the string and upending the wing to allow gravity to do it's stuff.  Then once the thin string goes thro then the wire is attached and pulled back thro.  Rather similar to the idea a friend of mine said he used to rewire his house - he said he starved the cat for a week, tied a string to him, put the cat under the floor boards and dangled a bit of fish where he wanted the wire to come out.  Simple -  but gravity is less smelly.

Edited By kc on 07/10/2019 19:14:30

[Denis Watkins]

Follow the advice of KC as there is a small real chance of spoiling the electrical contact

Balsa is more easily altered at this stage

[Martin McIntosh]

In your case I would carefully remove the plug shells with a scalpel in order to thread the wires through. Just lift up the locking tabs, remembering that you need to do this twice for each wire since there are two plates which require sliding out. When refitting, push the tabs back in and test with a good pull. This only works if you do not have extentions of course.

[Dove from above]

Martin, you are correct. I did not clearly say about removing from the case.