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Old Apr 04, 2016, 05:17 PM
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Question
servo mounting: wrapped with tape and glued

This isn't necessarily a sailplane specific question but more of a general building question. My question is what is the best combination of tape and glue for mounting servos to keep them removable?

I don't really like gluing servos into wings, or anywhere really. I would much rather use wood frames and screw them in. However, one doesn't always have the right wood frame on hand and sometimes , if you are not using "wing" servos, the angle of screws is sort of the wrong direction. Two different people have suggested that you can wrap a servo with electrical tape and then glue that into the wing with epoxy. The idea being that you can remove the servo by cutting the tape. It strikes me though that electrical tape is maybe not a great choice. I don't think epoxy sticks very well to PVC tape.

Anyway, I would love to hear others opinions about this concept in general; that being servo mounting schemes that allow relatively easy servo removal and if there is an optimal tape/glue combination that is both strong but serviceable.
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Old Apr 04, 2016, 06:13 PM
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One way of doing it is to wrap the servo in some thin elastic food packing foil or similar, then you mix a thick slurry of epoxy/microballoons and mount it in the wing with excess so that you get kind of a small molded frame around it. Then you put the servo in it without glue and just secure it with some strategic dashes of epoxy around the top of the "frame"/servo, if the servo is steady in it's pocket it don't take that much to hold it in place. If you need to remove it for service the dashes of epoxy is easy accessible with a dremel grinder tool. You can do a test on a scrap piece first to see how it turns out and if you're happy with it. Just one way of doing it..
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Old Apr 04, 2016, 06:27 PM
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Not saying that there is one for all circumstances but I have yet to find an sailplane application that didn't have a servo frame available . I hate the epoxy/tape method and avoid it like the plague. Maybe look a bit closer at the assorted vendor's supplies such as Esprit and SUSA. There is plastic in addition to wood frames and I have used the plastic when space is at a high premium . They a bit less bulky and have even trimmed them for installs such a servos in the tail like on the Pulsars.

Just in case you've missed these two pages

http://www.espritmodel.com/servo-installation.aspx

http://www.soaringusa.com/Servo-Frames-and-Accessories/
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Old Apr 04, 2016, 08:30 PM
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Dunno what "quality level" of plane/gear you'll be using. But I've grown fond of hot glue. In a composite plane, with a hard crash the servo merely pops loose (like a fuse!) preventing all mechanical damage.
Glue remnants are easily peeled away compared to epoxy that needs to be ground out (especially after the 2nd or 3rd re-glue and servo then sits so much higher than before). Con: repairs can't easily be done in the field wthout making it a more permanent-type glue bond. Pro: repairs at home take 10minutes to remove old glue while gun warms, and with transmitter/plane powered up and surface at neutral trim, merely plop the servo into warm glue and wiggle until at neutral and hold for 10 seconds.
999 ways to skin the same kitty.

Edited to add: I've confirmed that freezing hot glue super cold will allow easy chipping-action removal.
Disregard entire post if flying in freezing weather.
Disregard nay-sayers that say it'll soften in a hot car...as my experience says your car will get heat-damage first!
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Old Apr 04, 2016, 09:02 PM
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Quote:
Originally Posted by Leadchucker View Post
I have yet to find an sailplane application that didn't have a servo frame available . I hate the epoxy/tape method and avoid it like the plague.
well I did say that I didn't really like the tape/glue method. My question was IF you use the tape/glue method, what is the best way to do it. For example, I was given a slope plane by a friend, and it used the tape/glue method on the ailerons. I had to change the servo arms so I pretty much has to stick with the existing method because there were tight servo pockets former with epoxy. I didn't want to grind all that out to install frames.

I appreciate the links. I have been on both those pages before.

Quote:
Originally Posted by cityevader View Post
Dunno what "quality level" of plane/gear you'll be using. But I've grown fond of hot glue.
I have used hot glue quite a bit. Pretty sure it ruined one set of servos from the heat. I tested the servos before installing them and after I hot glued them in they didn't work. This was on a 3D foamy. It was difficult getting them out. I didn't know about the tape method at that point and I swore I would never glue servos in again. I have also used hot glue on CTH flying wings. I have had servos gets loose.

I prefer epoxy but am trying to find the best tape to use. I did some more digging and found that masking tape is popular. I saw a couple of references to packing tape. Also heat shrink. But, I have not tested the adhesion of epoxy to any of them. I plan to do all that but wanted to get this thread out there to see what others knew.
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Old Apr 04, 2016, 09:41 PM
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I typically use 3M blue masking tape (wrapped completely around the servo), and a medium mixture of 5 minute epoxy and micro balloons (enough to thicken it, but not so much that it becomes a gritty paste). I've used this in composite slope planes with no problems. The only time I've had one come loose is on a hard landing where I don't get the flaps up quick enough.

To remove, I wrap a piece of wire around the output shaft, then, using a screw driver stuck through the wire (to act as a handle), I pull up sharply, and it typically pops free.

The main drawback is having to grind out the epoxy left on the bottom of the servo bay before installing a new one...but that's just a few minutes work with a Dremel. On the plus side, you are left with a nice pocket around the sides that lets you perfectly align the servo when you reinstall it.

I should note that I always reinforce the wing skin with carbon fiber to prevent any deformation when pulling the servo out.
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Old Apr 04, 2016, 10:30 PM
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rhodesengr:

I think you can see there area number of ways to glue servos in, and still have a good chance to remove them if you have to. My personal preference is any 3M masking tape around the servo, and glue it down with medium CA. I've also used 30-minute epoxy (both with microballoons, and without).

I've also used (at least once each): hot glue, bathroom vinyl caulk, Goop and Shoe Goo.

But, in the end, mounting the servos in a tray or frames, with screws, is the best.

Yours, Greg
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Old Apr 04, 2016, 10:50 PM
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WHATEVER method of wrapping the servo is used- it all ends up in the wash. It'll eventually get removed for repairs unless the entire plane is DOA. The solid adhesive sub-layer is still there, AND the wrap of choice is still there. So who cares?

The better question should be...how does one remove the few different types of adhesive available, off of the wing in order to apply a fresh servo all purty like...with/without saving the servo for re-use.

Dagnabit, there should be a sticky for emperical-measurement-posts...

Want countless flights within a few seasons? Masking tape truly is wonderful.

Hanger queen flown a couple times a year for many years to come? (I'd go for blue tape then, but my planes needing many, multiple years of life span got frames)
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Old Apr 04, 2016, 11:38 PM
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well for what its worth, I just did an impromptu adhesion test using BSI 5 minute epoxy with various materials I had on hand including:
black PCV electrical tape
3M Blue Painter tape
3M clear HD packaging tape
3M Extreme Tape
some generic Scotch-type tape (typical desk stuff)
Some clear heat shrink
Aluminum foil

I didn't do anything to clean or improve the bond

The only material that formed a real bond was the aluminum foil

I was able to pop the glob of epoxy off all the tapes but the Blue 3M tape and the desk tape were the best. There seemed to be a partial bond to the blue tape. The desktop scotch tape, actually stuck pretty well. I could not get the glob loose by picking at it. I had to peel it off the working surface and then I was able to peel it off the glob.

So this was my concern. Epoxy does not bond very well to most plastics. The Blue tape is paper so that s why its better.

I may try again but I'll wipe the surfaces down with acetone and alcohol first.

Looks like the best bet would be to get some aluminum foil tape or maybe copper. I know I can get copper foil tape. I have some at work that we use for various things.
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Old Apr 04, 2016, 11:57 PM
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Something to keep in mind with the plastic tapes is that it's got a release agent on it make it easier to peel off the roll. I'm not sure if masking tape has that, or if it does, perhaps not to the degree that packing tape has it.
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Old Apr 05, 2016, 01:03 AM
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If plastic didn't stick, then why all the threads about "can't remove epoxied in servo"?
The point of the wrap isn't to improve the stick...but to improve the RELEASE of the servo while maintaining flight loads etc. Not too much, not too little...pick yer poison.

No need to reinvent the wheel here.
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Old Apr 05, 2016, 06:11 AM
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right way is for whatever glue you use to "key" to both the servo and the wing cavity, so it makes no real difference if the glue actually bonds to the tape or not.

my favorite method is to make the cavity ~1.5mm larger than the servo all the way around, drop the servo in place and then pump hot glue only into the corners. sometimes i'll cut the lugs off, sometimes i frame around them.
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Old Apr 05, 2016, 10:36 AM
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Quote:
Originally Posted by cityevader View Post
If plastic didn't stick, then why all the threads about "can't remove epoxied in servo"?
The point of the wrap isn't to improve the stick...but to improve the RELEASE of the servo while maintaining flight loads etc. Not too much, not too little...pick yer poison.

No need to reinvent the wheel here.
so my whole point was not to reinvent the wheel. I was advised to use electrical tape and I doubted that was a good choice. I understand the goal is to be able to get the servo out but I have also had servos come loose when directly hot glued and also when wrapped with e-tape and epoxied in.

So what is "the wheel" for you? Which tape and which glue?
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Old Apr 05, 2016, 11:46 AM
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Hot glue/no tape.
Masking tape/epoxy.
Rum/Coke.
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Old Apr 06, 2016, 07:35 AM
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In DLGs we typically wrap the fuse servos in masking tape and a cotton thread. Some have reported that on extra hot days that when wrapped with just masking tape that the glue in the tape loosens causing the servo to move, albeit a tiny amount. A tiny amount in a DLG can be enough to notice a difference in flight characteristics.

I've been able to use epoxy and micro balloons on the servos wrapped in tape with cotton thread and remove them without much of an issue. You do have to use it sparingly though.

Another idea is to "make" your own frames. I have a scrap wood box that I make sure has at least a few bits of hardwood in it. They work good for sanding into a solution. If you have regular mount servos that you want flush in the wing you can make two small blocks and cut a notch for the servo tab to slide into. Then position the blocks and servo in the correct place in the cavity and glue only the blocks into place. To secure the servo just a drop of hot glue over the tab should keep it from wiggling loose.
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