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Nick Jackson

Wing servo installation terror

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Nick Jackson

I'm about to install wing servos in Servorahmen frames in a new F5J model. Is there a consensus on
(a) gluing frames in empty and screwing the servo in later or
(b) installing frames with the servo in place with suitable measures to keep the epoxy off the servos?

This will be the first time I've wrestled with IDS.
And I'm still sorting out the hash I made of my last frame installation: decided to have the servos in place when gluing the frames (for accuracy, to avoid distortion of the wing service and to stop epoxy seeping into the space for the servo). I used cling-film to protect the servos. This failed spectacularly, when I found that  3/4  servos were faulty and would not centre properly and needed to be replaced ....  but were firmly attached to the wing skin. I'm having to demolish them in situ to get them out - expensive and irritating with the standard pushrods used last time and I dread to think about a repetition of this with an IDS system.

Any tips (practical or therapeutic) gratefully received please.

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thermaldoctor
2 hours ago, Nick Jackson said:

I'm about to install wing servos in Servorahmen frames in a new F5J model. Is there a consensus on
(a) gluing frames in empty and screwing the servo in later or
(b) installing frames with the servo in place with suitable measures to keep the epoxy off the servos?

This will be the first time I've wrestled with IDS.
And I'm still sorting out the hash I made of my last frame installation: decided to have the servos in place when gluing the frames (for accuracy, to avoid distortion of the wing service and to stop epoxy seeping into the space for the servo). I used cling-film to protect the servos. This failed spectacularly, leaving me with 3/4 dodgy servos which would not centre properly needing to come out but firmly attached to the wing skin. I'm having to demolish them in situ to get them out - expensive and irritating with the standard pushrods used last time and I dread to think about a repetition of this with an IDS system.

Any tips (practical or therapeutic) gratefully received please.

Hi Nick glue in the frames with the servos bolted in place otherwise they will take up the natural curve of the airfoil and bolting in a flat servo afterwards will distort the  skins.

Use small dots of masking tape to cover up the screw holes on the bottom of the mount otherwise you can get small pimples in the top skins where the screws are located.

Lightly cover the servo in some sort of grease but really rub it around well with your fingers. Get in all the nooks and crannies of the tabs. Also apply small amount of grease to the screws too. Always put an old servo horn on so you can pull on it with pliers to get the servo back out more easily. If it is your Infinity you are talking about don't use the IDS horns for this use a normal servo horn.

The way I make it as neat as possible is to use a small paint brush to brush on the laminating resin to the underside of the frame and around its lower perimeter. I then also use the same small paint brush to brush on the resin where it makes contact with the wing skin (approximately). This wets out both contact surfaces nicely. Then I wait for the same laminating epoxy mix to start curing and go almost like sticky toffee. In this state it will still bond perfectly to the mount and wing skin because you already wetted them out but it wont ******* out everywhere.  I use a small flat headed screwdriver or spatula to scoop out and blob on the epoxy. You don't need too much just have to judge it. Aim for a bead of approx 2mm along the middle of each side of the mount. You could of course use colloidal silica or micro balloons to thicken the mix after you have wetted out the frame and skin to get the same effect if you wanted.

By doing it this way my installations have become neat and reliable without any trouble ever getting a servo back out or causing marks on the shiny outward side of the top wing skins. Whilst I am sure some may not want to do it my way, or indeed may disagree with my way I am sure you will find everyone will agree you need to glue your mounts in with the servo fixed in place. 

Hope this helps

Neil

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oipigface

(Thermaldoctor’s reply arrived as I was writing this.)

The primary issue is getting the geometry right, which means that things that are fixed and cannot be adjusted need to be fixed right. Put the servos in the frames with all the LDS components in place. Link up the surfaces, and make sure that everything can be lined up correctly. Take it all apart, then put it in again pretending that there’s glue on the frames or skins. When you are absolutely sure that the setup can be installed correctly without making a mess, apply glue, put it all together, weight it down, and treat yourself to a beer.

Edited by oipigface
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Phil.Taylor

0. lots of masking tape around the servo hole - right to the LE & TE - epoxy always goes where it shouldn't 

00. set up the servo arms for the throws you need

1. wrap servos in cling-film 

2. fit servos in frames - with the screws tightened up fully

3. dry fit the servos/frames - mark on the masking tape where the epoxy needs to go, and an alignment line(s) for where the servo horn should be

4. thin layer of epoxy on wing skins where frames will go, more on the mounts themselves - really don't need large amounts though

5. servos in - line them up - weight them down till the epoxy sets (ballast is good for this)

if you cant get servos out which were cling-film wrapped something is very wrong! - it is possible to end up with a bit of epoxy around the servo lugs, which of course you cant cling-film, but I've found a gentle tug on the servo horn with a  pair of pliers will release the servos from the mounts - nothing sticks to the cling film so the servo body wont stick to the wing skins (now - someone prove me wrong with extra-sticky cling film that sticks to epoxy!)

Phil.

(2* - if you don't fit the servos to the frames first - when you fit the servos the screws will push up the fixing epoxy & cause bumps on the surface - seen it done, looks very bad, is very bad - also, if you do subsequently remove the servos, file the screws down a bit before refitting them to avoid the dreaded bumps when fully tightened)

 

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Nick Jackson

Wow. Many thanks to all respondents for confirming installation should be with the servos in place and for taking the trouble to provide such detailed advice - extremely helpful to me and I'm sure there are great tips here for others too. Much appreciated.

(Will fill you in on how it goes when I've done the business but my schedule means it'll be a while. Clearly not a job to rush.) 

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Nick Jackson

Servos went in fine using the advice in this thread and seem well anchored - thanks again. I'm too chicken to try removing them unless and until this becomes necessary but I'm fairly confident that they will come out if the need arises.

I prepared the servos with several coats of spray-on Screwfix white lithium grease before fitting (including a final coat with the servos screwed into the frames and the frames masked off to avoid getting the grease on them).

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RSH

Hi Nick,

I used these frame in my Shadow 2 wings and installed the servo in the frame before sticking into the wing to ensure correct  positioning/alignment of the pushrod.

I also wrapped he servo carefully in clingfilm and then used vaseline on the screws (in case the epoxy squeezes up through the mount).  This worked well.  You could also smear vaseline on the servo before wrapping in clingfilm if you are still concerned about sticking.   

One point i would make is to  firstly scuff up the underside of the frame to allow the epoxy to key onto the frame.  I then use minimal amounts of 24h epoxy to start with as this prevents some problems.   I then lay the wing on something soft and add weights to the top of the servo to keep it down and in place.

Once cured and disassembled, i add a small amount of epoxy to front /rear external edges to ensure strong joint.

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