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Manual Trim, HS Spar Hole

JonJay

JonJay

Well Known Member
The Manual Trim Cable requires a 7/16" hole through the rear spar, which interferes with the Spar Reinforcement bars requiring them to be cut into. This is well known.
In short conversations with factory, it is "suggested" that this has been the case from day 1 and there has never been a "known problem" with weakening the spar at this point as a result. I know a few of you have gone with your own Electric Trim set up's like Randy, but I am really set on the Manual Trim set up as originally designed by Van's
I would like to know those with current flying RV's, how many have Manual Trim and the original cable set up that required the notching of the Spar Reinforcements?
Thanks.
 
I drilled the hole and cant see any reason why notching the center of the bars will reduce the strength of the rear spar by a meaningful amount. If I remember anything from my structures classes its that the center of a beam doesnt see much stress. Of course my plane isn't flying yet...:rolleyes:
 
Trim able

Hello. Not yet flying like Rob. I am going to change to other cable. Size hole and weight reasons,

Saludos.

Mario.
 
How much does that ACS cable weight compared to the vans cable? Is it easier to snake through the HS and elevator? I might switch mine out if it saves some weight.
 
Trim Cable Analysis

Sticking with my moto, I decided to cut into a perfectly good trim cable to see if I could modify the end elliminating the fat conduit cap and threads. Plus, I was just curious....
I clamped the conduit cap into my milling machine and started milling through with an 1/8" end mill so I could control the layers I was cutting through. The standard Vans cable is made by Tutthill and is a "light duty" grade cable. I would hate to see what a heavy duty cable is 'cause these things are very tough as is.
Most interesting is the part that is actually doing the work which is a relatively thin multistrand cable wrapped with a flat spiral wound steel casing. The whole thing only measures about 1/8". This cable is swagged onto the stainless rod end that is threaded 10/32. This cable rides inside of a nylon sleeve which is in turn wrapped with mulitple strands of steel cable and then encased in the green plastic outer sheath. One very tough cable capable of some pretty extreme and dirty environments.
I have no doubt that a lighter duty cable with similar push and pull load ratings would hold up well in this application. The ACS cable that several people have used, either connected all the way to a manual lever or to a servo should be more than adequate.
When I get the ACS product specs from thier OEM, I will post them.
 
Hi Jon,

You are correct, that link is pictures,BUT -------------
look at the pictures and you will see.
Fred
 
Trim Cable

The specs on the ACS cable are here:

http://www.acsproductsaz.com/790.htm

The dwg is for a different cable, but sheath, liner and core are the same as Acft Spruce part #05-169144. It's lighter, but I don't know by how much, and way more flexible than the "green snake". Different folks will find different ways to secure the ends of the sheath. Pop a beer and spend time looking at photos and verbage here to see how I did it:

http://picasaweb.google.com/tonyboytoo/RV3BMiscellaneous#

Use a plastic snap bushing wherever the sheath goes thru aluminum.

Eighty-two hours on this setup with no problems.

Tony
 
More follow up on Trim Cable

ACS carries two styles of cables. A multistrand cable and a solid cable. The multistrand cable is not rated for Push/pull, the solid cable is. There are no specifications available other than the end fittings are factory tested to #125 of pull for failure of the swagged end.
Van's supplied cable is a multistrand cable wrapped with a flat spiral wind. The flat spiral cable gives the rigidity necessary for the "Push" in the push/pull applications. The multistrand part of the cable gives the flexibility to withstand bending cycles, as you get when the elevator goes up and down. So, you get the best of both worlds but pay the price in the bulkiness of the cable.
The only concern with using a solid cable is how many cycles it can withstand before it is compromised. It is well known that the multistrand cable will last a long, long, time going through thousands of cycles as the elevator is exercised. This is not know for the solid cable.
I will leave it up to each of you to determine what is best for you. I intend to use Van's standard cable modified to allow it to fit through a much smaller hole in the HS spar so I do as little damage as possible to the bars.
 
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