Composite control drive installation

[Konrad]

I just spent the better part of a day grinding out legacy control horns from my modern composite ship.

I’d like to learn why composites ships haven’t fully moved away from the classic control horn we first became familiar with way back in the days of balsa wood models?

I see an opportunity to make a better product. By furnishing a pocket for modern control drives such and RDS of IDS we can have stronger and easier to assemble models.

As it is I had to cut into the bottom laminate of the top skin of the control surface. With heavy carbon layup it is possible to remove the fiber control horn and grind out a pocket for the IDS without too much surface damage. But on lighter glass layup I’m finding that it is all but impossible to make the IDS pocket without some surface finish damage. On my last such model, the Gremlin, the skins show heat damage from the rotary cutter and there are a few break throughs on the outside skin.

I see no need for a modern moldie to still be set up for the classic control horn. Is there reason that composite OEMs don’t offer their control surfaces with pockets to accept IDS or other drive system? Having the control surface set up for the classic control horn appears to me to cost a lot in potential strength and results in a lot of installation stress for the assembler/owner.

Some OEMs leave off the control horn. This is great as it minimizes the chances of the rotary burr damaging the wing while trying to remove the classic control horn. But this still leaves the inside skin needing to be removed to make room for the needed pocket.

I’d like to put forward that the OEMs of composites offer their controls with the pocket supplied at the time of manufacture. A pocket like I show would offer 25% more fibers across the drive area of the control surface, as the inside skin need not be cut. It would still offer those that want to use the classic obsolete horn that option. Without forcing those of use wanting the benefits of a modern drive system suffering the strength loss.

Some may want to read this sister thread.

Servorahmen IDS servo mounts etc - step by step install?

Hi Guys, I'm fitting out an Aresti 2M aerobatics plane right now, and I'm using the Aloft supplied Servorahmen type servo IDS system with 2 x try out "mystery" (read "Chinese") wing servos and 2 x KST wing type. Problem I quickly found is there does not seem to be any full...

forum.alofthobbies.com

 

[Wayne]

We usually request no control horns for our larger slope ships here at Aloft. For the models with moulded control horn bumps, I do prefer those models come with the horns preinstalled as they are a pain for the end user to install. My thought is that the planes with the moulded bumps will use control horns.

We can certainly look into creating a pocket for the IDS systems, but that may be a little tricky due to different sizes etc, but I bet something could be made.. Just a removal of core material and some more glass or a little carbon patch would help.

 

[Konrad]

That control horn hood is another issue. Again tied to the antiquated classic horn.

That is my concern in that the removal (rework) of the surface from the default control horn runs a huge risk of surface damage. Then there is the strength issues. If the default is for the IDS be it the OEM own or the Servorahmen brand it would make a better ship. Now if for some reason someone want's classic horn the option is still there. Just that those of us seeking a more modern approch aren't compromised.

Patch, do guys have a process to add a cloth patch while installing the spoon?

A big plus for ordering your inventory without the horns install if possible.

 

[Wayne]

There are a few really planes I have seen that come with full linkage solutions, basically just drop in the correct servo. This comes with a very high price tag though. Other than that I can't think of anyone doing something along these lines for a reasonable price. It would be nice to see.

The other issue is many manufacturers are shy to lock in on a given servo for their planes. Often times the life span of the plane is greater than the lifespan for a given servo. With this said, yes there are some rather standard features to something like a wing servo, but sadly they will have slightly different demensions or different splines. It is a challenge to say the least.

I think a plane with a "servo adapter" tray moulded in and a provision for the linkage pocket is a nice idea and could be accomplished. Will see if I can get any upcoming designs on board.

 

[Konrad]

That's another issue, how was the model intended to be assembled? Yep, Valdimer Models does have well engineered and outfitted models, well worth the cost. I'd like to see OEMs list what was used or intended to be used for assembly during the CAD and prototype stages.

The issue here isn't so much tying anyone to any specific equipment. Rather moving the default configuration that offers the full benefit of modern fittings.

I'd like to see where the OEM provides a relief, pocket or whatever where the continuity of the fiber skins is maintained. Cutting a relief in the skin core (balsa or foam) and allowing the two laminate skins to bound, seem to my eye to be a much better default than what we have historically seen. This configuration does not limit one to any particular brand or drive yet still allows for the antiquated control horns should one still want to use them.

Let's throw away the horn! Or more to the point, don't cripple the model by defaulting to the use of horns.

All the best,
Konrad

 

[Konrad]

I don’t mean to be picking on Aeroic model, it just so happens that I have a lot of their aircraft on the build bench right now.

What I’m showing is what I think was placing unnecessary risk of damaging the skins and finish of these light weight skins to remove ill advised control horns (antiquated tech).

These models really do show us what levels of performance we can achieve with modern molded models. But to saddle us with control horns and servo arms that limit the useful motion of the servo is counter productive, and adds drag. To any OEM here, please it is far easier to glue in horns than it is to remove them! Control horns are so 20th century! If one must offer horns please please leave them off in the 21st century.

I fail to see why the customer today needs to deal with the obsolete tech of yesterday.

Disclaimer:
The photos is of damage to the wing I had to remove the improperly installed Servodeharm spoon. What comes across in the photo is often what we see when we have to remove the factory installed horns. (The real damage from the horn removal didn't show up in my photos).

The live hinge fail as a result of having to over stress the hinge to get the rotary tool into the control surface (not a normal failure mode).

For me these are simple items to repair. But to someone without the tools or experience in composite and paint repair this could be very disheartening.