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How to install servos in a foam core wing?

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How to install servos in a foam core wing?

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Old 06-21-2004, 08:34 PM
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Someone11-RCU
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Default How to install servos in a foam core wing?

I have a CA Models Widebody 40, and now I'm at the point where I cut out the sheeting/foam for the servos in the wing (foam core wing). The instruction manual that is available at camodel.com.ar does not clearly describe how this works. From what i can conclude, it says to sheet the cut out, and add hardwood blocks for screws, but thats all. I'm not sure on how this would work; does anyone have pictures of their installation that can help me figure this thing out?

Thanks, Brian
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Old 06-22-2004, 05:34 AM
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Default RE: How to install servos in a foam core wing?

Brian, Cut the sheeting with a razor blade just large enough for a servo. Remove the sheeting and cut out the foam (You can use a razor or a soldering iron). Then glue some plywood scraps where the servo screws will go.
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Old 06-22-2004, 06:30 AM
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Default RE: How to install servos in a foam core wing?

Here's a nice and elegant solution:
[link]http://www.mindspring.com/~cramskill/flushmt.htm[/link]
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Old 06-22-2004, 10:47 AM
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Default RE: How to install servos in a foam core wing?

CA Models has the hole cut out big enough so the entire servo can be placed in the wing... which leaves only the servo arm above the wing. So what I'm thinking, is that I can sheet the interior walls, and then install hardwood blocks on the ends of the box, which allow it to screw into. Here
's a pic of what im working with....
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Old 06-22-2004, 10:50 AM
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Default RE: How to install servos in a foam core wing?

Thanks for your help!
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Old 06-22-2004, 12:34 PM
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Default RE: How to install servos in a foam core wing?

No box necessary, just add two plywood strips for the screws to bite into
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Old 06-22-2004, 01:55 PM
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Default RE: How to install servos in a foam core wing?

Mike,
That's a great method, but I wanted the servos to be inset inside the wing how the instruction manual shows it. I feel this would make a cleaner look, and maybe a little more streamline. This is the picture in the manual that shows the installation:
Would I just glue hardwood blocks on the sides?
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Old 06-22-2004, 04:05 PM
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Default RE: How to install servos in a foam core wing?

I am building a super reaper and discover this thread.
I was asking myself if prebuild box to be inserted in foam wings for servo mounting exist......

a kind of square box with a cover and the servo fixed on that cover with only the servo arm extruding.

exactly the same setup than on the link above, but prebuild in composite material and ready to use.

do you know a manufacturer making that ?
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Old 06-22-2004, 05:05 PM
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Default RE: How to install servos in a foam core wing?

ORIGINAL: MinnFlyer

No box necessary, just add two plywood strips for the screws to bite into

I prefer the load on the servo to be from front to back rather than a side load.
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Old 06-22-2004, 07:37 PM
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Default RE: How to install servos in a foam core wing?

ORIGINAL: 8178

ORIGINAL: MinnFlyer

No box necessary, just add two plywood strips for the screws to bite into

I prefer the load on the servo to be from front to back rather than a side load.
I'm not sure what the advantages or disadvantages are for having the servo mounted sideways. Now that you mention it, it concerns me because I'm using Hitec 645's which put out over 100oz of torque, which is now making me think that it might distort the foam which the hardwood block is glued onto. I still haven't put servos in yet, but maybe I should mount it a different way? Hmmm... any ideas guys?

Thanks for your help and time!
-Brian
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Old 06-23-2004, 10:17 AM
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Default RE: How to install servos in a foam core wing?

suggest a piece of plywood glued to side of back and front of the box would help, don't forget to cut the foam out. dick
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Old 06-23-2004, 11:07 AM
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Default RE: How to install servos in a foam core wing?

Cut a 2 1/4 in. square hole, about 1/4 in. deeper than the thickness of the servo. I use a soldering gun with copper house wire shaped to the size of the hole you need. Line the inside with 1/16 balsa, only up to the top of the foam. Glue in the corners, 1,4 sq. spruce or aircraft plywood the full depth of the hole, up to the foam. Make an aircraft plywood cover the same thickness of the foam, 1/16 or 3/32. to go in and sit on the corner posts. Mount the servo on the inside of the cover on 1/4 in. or thicker plywood rails. Cut a slot in the cover for the servo arm and full movement. Screw the cover down with wood screws into the corner posts. Hope this helps.
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Old 06-23-2004, 11:32 AM
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Default RE: How to install servos in a foam core wing?

Brian, Ok, I see what you're trying to achieve. In that case, yes, you could add the hardwood blocks to the inside.

If you really want to clean it up, take a look at the great "How To" that Caffeenman has on his site about making hatches. You can't do it step by step cause his is designed for a built-up wing, but you should get enough info from it to figure it out.

http://airfieldmodels.com/informatio...ruction/08.htm
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Old 06-23-2004, 10:37 PM
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Default RE: How to install servos in a foam core wing?

Flypaper2, your idea with the copper wire is great! I will try it for this job.

Do you guys think I shuold try to turn the servo the other way, so the load will be from front to back instead of side to side? Why can't I just mount it sideways like it has it in the manual?

Thanks to everyone for the helpful links and insight!
-Brian
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Old 06-24-2004, 09:13 AM
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Default RE: How to install servos in a foam core wing?

Brian:
The servo mounts need to be towards the front and back of the wing. If It's parallel with the wing it will tend to rock back and forth on the rubber grommets. If I understand you, you want it parallel with the wing as per your picture?
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Old 06-24-2004, 12:08 PM
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Default RE: How to install servos in a foam core wing?

The manufacture suggests a parallel servo setup. I don't think I would be able to mount it perpendicular to the wing because the airfoil is too thin. I could use Minnflyer's original method with the hardwood pieces atop the wing, but I really like that inset look. Right now, a hatch setup seems like too much work. Would that rocking mess anything up, or affect the servo's performance?

Thanks,
Brian
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Old 06-24-2004, 12:50 PM
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Default RE: How to install servos in a foam core wing?

ORIGINAL: Someone11-RCU

CA Models has the hole cut out big enough so the entire servo can be placed in the wing... which leaves only the servo arm above the wing. So what I'm thinking, is that I can sheet the interior walls, and then install hardwood blocks on the ends of the box, which allow it to screw into. Here
's a pic of what im working with....

Someone - That is the way to go. You want to box up the entire hole and then epoxy in 1/4 square hardwood stock as servo rails. This is typical of CA models. I do this in my GS CA kits and it works flawlessly. Without the torque boxes, the sheeting by itself is not strong enough to hold the servo torque over time and it will fail. Build the torgue box with 1/16 balsa, using epoxy to the foam. This is bullet proof.

Make sure you don't put the servo so deep in the hole that your ball end or whatever you chose to attach to your arm interferes with the wing skin.

DP
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