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Sticking micro servos to carbon


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I am building a Snipe2 (F3K glider) and need to glue some KST08N servos in position. They just stick on their side to a flat piece of carbon. I would like to be able to remove these one day if there is a problem so would rather not glue direct to the servo. I know people often wrap some kind of tape around servos before gluing into wings etc. but any suggestions for the best way to do it in this instance? All the photos I have seen just seem to have servos glued directly in position. Thanks.

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Tim

My solution is to stick micro servos directly but with something like UHU POR. On hard flat surfaces with a film on both sides and let to dry for a 10 to 20 seconds it acts as a instant contact adhesive. It will reach maximum strength after an hour but it will always be able to be prised off with a sharp knife.

Provided the servo is lying on it side and ideally 'buried' it will not move, indeed with the force required to get it out you have to be careful not to break it.

Just glued in place in foam.

Servolink2

To make fitting a bit easier I nearly always cut the lugs off the servo as well.

It works for me.wink 2

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I would have thought tape wrapping then gluing was the best method. That is how I do it.

Rough up the carbon and tape and use a decent glue like epoxy - or a microbaloons and epoxy mix for light weight and a larger glue area. Any sort of tape will do if the epoxy will stick to it OK (check on a test piece). I have used masking tape and kapton tape.

If you just use glue you might have to grind out an entire servo later (been there, done that!), but the tape wrapping makes removal a lot easier and just leaves a bit of glue to grind out

Dick

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Servo frames are widely used in F5J, changing a servo with stripped gears on the field is just two screws.

The German company Servorahmen is probably the market leader.

A Swiss company RC Solutions

produce very nice CNC cut servo frames, I have used these for tail mounted F5J servos.

There may be a weight penalty or space problem using these in DLG/F3K gliders.

You can make your own servo frames with hardwood blocks, carbon or metal strip and screws, I did this recently on a small glider.

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The forum software has rotated both of these images 90 degrees anti-clockwise but you should get the idea.

When I use frames in carbon skinned gliders I always use a load spreading base of carbon sheet (same as the ply used in the photos). If the frames are glued directly to the skin they can distort the skin under load and their position can be clearly seen and felt on the outer surface.

The other advantage of doing this is that when servo frames are glued in with the servos fitted (wrapped in clingfilm) with the radio turned on there is a risk of gluing the servo to the frame where there is not if the frame is glued to the plate.

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Thanks Geoff / Gary. There isn't room for any kind of frame in the snipe2, it's too tight on space. The servos are ones without lugs and people seem to just stick them on one side to a flat carbon plate. I will try to post a picture later. Good info to know how you do things with a bit more room though.

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Posted by Rich too on 08/01/2021 06:49:56:

I have used silicon sealant successfully, it is easily removed if necessary.

A big plus for that one Rich too.

I have some models that are over 20 years old and the servos have been tacked onto epoxy glass and carbon fibre with no deterioration at all. I think that the slight flexibility helps absorb flight/landing stresses.

Use 'neutral cure' silicon though, the stuff that smells like acetic acid is corrosive, especially to servo and Rx electronics. Just degrease all surfaces prior to bonding.

Skippy

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Posted by Brian Cooper on 08/01/2021 08:58:56:

If you want to get really posh, wrap the servo in a heat-shrink covering before gluing it into place . . This makes it really easy to remove the servo in the future. . It is also less of a struggle to clean off the old glue from the airframe.

Plus one for the heat shrink method

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Apologies for late arrival at the party - as a stickier alternative to masking tape try Micropore, a 3M product. Micropore comes in a variety of widths, but 1.3 or 2.5 cm is probably most useful for this job, it's fibrous texture (like thinner, stickier masking tape) works well with epoxy. Micropore also makes a useful temporary hinge repair (you can also use Blenderm but that's a bit more stretchy). Whatever tape you wrap round your servo, Sticky Stuff Remover is your friend.

I would also suggest 2.5 cm rolls of both Micropore and Blenderm in your First Aid kit too - you do take one with you when you go flying don't you?

Edited By Doctor Chinnery on 09/01/2021 13:58:17

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Thanks Mark, good timing I was just about to stick with servo tape ! Good to know they can be removed if stuck direct with CA. I might just do that anyway once I'm happy with the C of G. Do you run 1S or 2S ? The only way I can get things to fit is to use a 300 2S located behind the servos (nearest the wing). I can't find anything that fits in the dimensions suggested in the instructions. Not sure if this will balance without adding nose weight.

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I haven’t flown the Snipe 2 but with regular snipe and Snipe SN a gumstick 1s 600 would lay flat on top of the servos and the nose cone would clear it.

Take a look at the Giant Power lipos, found at component shop, the 1s 380 works great if you have to go smaller in battery size, still easily get a hour run time with the 4 kst 08 and a telemetry rx.

Don’t chase weight, it’s pointless, if you need nose weight then add it (tungsten putty is great) your plane will fly the same whether it’s 220 grams or 240 grams, especially in good old Blighty weather. In fact 240g is/was my favourite weight ( I don’t fly anymore but still check the forums now and then )

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