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Servorahmen IDS servo mounts etc - step by step install?

Konrad

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As to filler is it cabosil, or milled fiber?

I see the spoon supporting the front of the control surface like a shear web. I'm concerned with the hole, or lack of continuity, in the sub spar of the wing itself in which the push rod travels.

P.S.
Sorry I see the you clearly state the sub spar of the control surface. I now assume that the hole for the push rod in the wing's sub spar was adequately reinforced prior to closing up the wing at the point of manufacture.
 
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Konrad

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By the way how do you make these nice gap seals? I've read of some lengthy processes that look to take an artist touch to perform well. I have some older ships that just have some thin plastic taped to the inside of the control surface. I'd like to try to upgrade these models to something like what you show.

All the best,
Konrad

IMG_4250.JPG
 
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Wayne

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@Konrad, be warned, those plastic gap seals held on with double stick tape (like Valenta uses) will let go sooner or later and plenty of crashes as a result. I had a plane with them, they were failing when I start my build. I pulled them off and reglued them with good results. The double stick tape from the manufacturer's is a bad idea. Glad James does not use those on his planes!!

James, looking great so far. No worries about killing the sub spar, this has been a pretty common cractive with linkage designs for a number of years now. LDS installs also take out the sub spar. On a fully moulded wing the skins, spar and leading edge make a very strong structure. I know it seems like a really bad idea, but we have been notching these sub spars or completely removing them for linkages for a number of years now.
 

Konrad

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Ah, the dreaded wipe lock!!

That's why I asked about a tutorial on how those nice radiused epoxy wipers (seals) are made.
 

Doc James Hammond

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As to filler is it cabosil, or milled fiber?

I see the spoon supporting the front of the control surface like a shear web. I'm concerned with the hole, or lack of continuity, in the sub spar of the wing itself in which the push rod travels.

P.S.
Sorry I see the you clearly state the sub spar of the control surface. I now assume that the hole for the push rod in the wing's sub spar was adequately reinforced prior to closing up the wing at the point of manufacture.

Exactly.
 

Doc James Hammond

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Aha...I'm not sure, but I think I might be the inventor of this type of gap seal MANY moons ago while still living in the UK in the late '70's with vac bagged wings.

I'm not doing any right now otherwise I'd just publish some pics.

I do remember that Joe Manor did make a really good "how to" gap seal/epoxy wiper video if someone could find it?

Here is an out of workshop mockup.
Basically it involves taping a mylar strip to the top of the control surface so that it can be slipped into the gap inner space.
IMG_8113.JPG

Then cabosil filled epoxy can be applied inside and smoothed before carefully pushing the mylar and tape inside the space. The control surface is then deflected about 45 - 60 degrees then taped down to let the surface of the mylar follow a radius while the epoxy mix cures.

Note that this picture is just painter's tape to show the method - the mylar is stiff and makes a far nice radius.

After that, take off the mylar and painting tape and sand the front of the now hardened wiper true.
IMG_6335.JPG

Otherwise next time I do some I'll take pics.

J.
 

Jose5x5

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Hey Doc, I appreciate the photos. On the IDS for the 2m Aresti. I need to start building mine. Do you have a detail build log that you can share. This will be kind of my first build. I did buy my Aresti and IDS system from aloft also.
 

Doc James Hammond

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Hey Doc, I appreciate the photos. On the IDS for the 2m Aresti. I need to start building mine. Do you have a detail build log that you can share. This will be kind of my first build. I did buy my Aresti and IDS system from aloft also.

Hey Jose, I almost finished this build, but I do have building instructions. If you PM me or email me I can send them.

There are a lot of alternatives in the instructions and unfortunately the IDS is not one of them. If you use the parts in the kit you still have a lot of choices.

Personally I DONT like to position servos in the tail but its only because I'm a bit "old skool" and there is no reason not to do this. In any case th models has pushrods installed, and servo holes in the tray.

Please let me know of you need any extra info.

Cheers,

James
 
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Konrad

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That's the process I recall. Too much epoxy and one has a permanent spoiler and shy on epoxy looks like crap.

I assume you use double sided tape to attach the mylar (acts as a glue seal keeping the epoxy off the lower skin of the control surface). The bottom of the wing can be cleaned up with solvent prior to the epoxy setting up.

I guess I'm just have to man up and do it! But I'll look for that video first.:rolleyes:
 
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Doc James Hammond

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That's the process I recall. Too much epoxy and one has a permanent spoiler and shy on epoxy looks like crap.
permeant
I assume you use double sided tape to attach the mylar (acts as a glue seal keeping the epoxy off the lower skin of the control surface). The bottom of the wing can be cleaned up with solvent prior to the epoxy setting up.

I guess I'm just have to man up and do it! But I'll look for that video first.:rolleyes:

Actually Konrad - once you get into it its not too bad - and yes its best to use double sided tape.

If its your first time, I'd have a lot of wipes and alcohol (the solvent kind) close by.

Also, using a small plastic bag like a cake icing piper helps a lot, and allows you to carefully control the amount being laid down. I tend to keep any tapered tubes that come on the tops of glue or sauce bottles for this job too.
Cut down and inserted into the bag then taped up or rubber banded tight to form a nozzle, they do a great job and are a little bit more controllable than just a plastic bag with a hole in it.

Also, also (!) having a shaped "spatula" to scoop off the excess epoxy helps too. I use those ice lolly sticks sanded a bit to shape. Hmmmm - "Lolly sticks" - is that what you call them in the USA?

"Resting" or using the tape to "guide" the spatula as you move along the control surface helps to get a nice even curve inside the epoxy radius and tapers it off nicely (with a little practice) towards the front.

I normally do several "scraping" scoops to get rid of most of the epoxy I don't need, as there is always too much. Then I do a final finishing run along the entire radius to define the final shape.

If you are super nervous it might be an idea to do a mock up first, using some shaped bits of wood or something to simulate the job, and let you get a bit of practice. Pretty easy to make I'd guess, and you can clean them and try again until you think you have it sorted.

After a short while you get pretty good at it.

Hope it helps!

Doc.
 
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Doc James Hammond

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Here are the last pics which are self-explanatory.

Conclusions:

This is a pretty good system that once installed is very solid and slop free, but also accurate and gives a nice lot of movement.

Its a REAL pity there are no instructions as to be honest its not rocket science, but a first time installer could sure cut a lot of corners and save a lot of head scratching time if there were some.

I'd use it every time if I could fit it in.

I'm looking forward to the 8mm types.

Cheers,

Doc J.
 

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Doc James Hammond

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I don't have photos of a full install, but here are some pictures that show the basics:

Detail of the bottom:
View attachment 325

Using an existing control horn:
View attachment 322

Using the internal "spoon":
View attachment 323

Pay attention to the geometry of the spoon, the taller side goes away from the aileron/flap hinge. In this picture, the hinge would be on the bottom.
View attachment 324

You can get a lot of throw that is very controlled when using the spoon. Best of all, the linkage can be contained within the wing, no extra drag. I honestly find these a little easier to install. The servo tray is about the same as a normal tray. The spoon just needs some material removed from the inside of the flight surface, then it all glues in.

The servo arms on these are one of the other neat tricks on these, they supply different lengths to get the amount of movement needed. You will probably be good with one of the very short arms if you are using the spoon. The cool thing about the arm design is you can use the full forward rotation of the servo without any worry of the linkage hitting the servo arm. No more crazy bent linkages and ground down clevises to clear the wing skins, etc. Yay!!

View attachment 326
View attachment 327
View attachment 328
Just noticed - on Wayne's pics, the small back bracket shown on this assembly is upside down. That will make it impossible to remove the servo from the wing. It should be the other way up with all the servo mounting tabs screwed in from the top.

See what I mean about the lack of instructions?

Cheers,

Doc.

Take look here:
 

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Konrad

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Referencing post #26 is this the video you were thinking of? And if not is this the basic process to adding epoxy wipers (gap seals)?
 

Konrad

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I now have a ship that has the preinstalled control horns, much like what Doc shows. My model an RCRCM Strega also has small hood fairings molded on both sides of the surface gap. These fairing look a bit too small to fully hide the spoons for the IDS servo mounting trays. As such I didn't think it would be worth the effort to remove the preinstalled horns.

I first tried to install "normal" external bearing servo trays with standard servo arms and push rods. Even with relief cuts to the sides of the clevises I couldn't get the servo arm short enough to allow full rotation of the servo without binding the control surface.
https://alofthobbies.com/external-bearing-servo-tray-for-kst.html

This forced me to take a look at the IDS servo trays. What is real nice about these is that they allow for some real small servo arms that allow us to use the full mechanical potential of the servo. This means being able to maintain the servo's resolution and power!
https://alofthobbies.com/ids-servo-tray-for-kst-integrated-drive-system.html

Luck would have it that the external bearing tray and IDS use the same servo mounting tray. This was nice as I had already glued the servo mounting tray into the wing.

But how to hook up the surface control horn to the IDS push rod? Well, I came up with this hybrid push rod. The IDS use preformed push rod fitting that are glued into an aluminum tube of the desired length. These fitting look to be of sufficient diameter as to allow me to do away with the aluminum tube. I decided to center drill the push rod fitting that goes onto the servo end of the push rod with a 0.063" drill bit and tap the bore for a 2mm x 0.4 pitch thread. This allows me to install a 2mm x 0.4 pitch stud on which the standard metric threaded clevis is attached.

This gives me an adjustable push rod that fits the standard fittings on the control surface. And at the same time allows me to use the second smallest servo arm of the IDS mount.

I need to thank Doc and Motowncali for planting the seeds to this solution.

All the best,
Konrad
1435
 
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Wayne

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Sweet, glad she worked out well for you. :) They are worth it just for those stubby arm options.
 

purview

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thx for this idea. a good combination to get closer to the spline and to use a standard prefitted horn

cheers chris
 

Konrad

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I'm suffering a rather unpleasant assembly experience with my RCRCM Strega. This kit is a glass lay up from late 2010. The issue I'd like to discuss; is that the installation of the servo mounting frame is distorting the top wing skin. I'd like to ask what process do you guys use to install these servo trays in molded wings?

Prior to these two Strega kits all my molded ships have had structural foam between the inner and outer layup fabric of the wing skins. RCRCM is using what I think of as a throw back material for this, balsa. I think this is the root of the issue I'm having.

Balsa has most of its strength with the grain (span-wise). There really is little strength across the grain (chord-wise). I'm also shocked that the balsa wing skins are made up of sheets that are butt joined. I don't see any scarf joints in the wing skins.

I fear that there is some force (hinge or glue) that is compressing the balsa sheets against the grain, causing the wavy distortion in the top wing skins.

I think RCRCM knew this might be an issue as they put what I think of as a stiffening carbon patch on the inside of the top skin to resist this force. (Mine has a patch that missed half the servo opening)

My process is something like:
Scuff the inside of the top wing to allow the glue more purchasing power. I also scuff the glueing surface of the servo frame, to make sure it is flat and the allow a better surface for the glue
I then slip the frame into the wing and mount the waxed servo to the mount with all the applicable screws. This way the frame is stressed as it would be by the servo when glued into the wing. I then align the servo and tray in the servo pocket with the help of the push rod to ensure it is aligned with the control horn. With the wing upside down and on a soft towel I push the servo against the top wing skin. And with a capillary applicator apply thin CA glue the accessible parts of the servo frame. After this cures I remove the servo from the servo frame and again apply thin CA glue to make sure I have a solid glue joint with the frame and the wing skin. After the CA cures I reinstall the servo. Flip the wing over and I'm greeted with a very friendly wing that is waving to me with its surface. :mad:

My questions are:
Is the CA shrinking when it cures.
Am I distorting the skin while holding the servo tray in place? And the CA is holding this distortion after it cures.
Should I be using epoxy and some holding fixture?

Another variable is that one of my wings is showing this distortion and the other shows little or no distortion. As these wings are built from a natural material, there may be a lot of variability in the density of the balsa. I suspect the friendly wing has “very weak punk wood" in the area of the servo mounts. This wing also has a warped aileron that I'll need to try to straighten out. I suspect there isn’t any post cure heat treatment for the epoxy before the wings are pulled from the plugs.

I was shocked that the wing skins of the RCRCM Strega are balsa with all the problems wood inherent in wood. Structural foam is rather uniform in its properties and between manufacturing batches. I'm sorry to say that I'm growing fonder of my old eastern European molded gliders.

All the best,
Konrad
1442
1443
 
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