8KCAB Rigging Question/Issue: Need Specialist

J

jwfoley

New member
I have a '78 Decathlon and I'm pretty sure I've got a rigging issue. It flies straight but doesn't roll as fast as I think it should. Here's the background:

During my last annual, I had the aileron cable tension adjusted from 12 lbs to 35 lbs and added spades (goal is to do acro this summer). When I got the plane back, the stick wasn't centered. Dropped it off and got that fixed (it's centered now) but then it wanted to gently roll left. From there, I dropped it back off and the mechanic/pilot adjusted the wash on the right wing. I also had him look at the aileron throw and it ranged between 16 and 19 degrees either side, up and down (I believe the spec is 24 degrees). The mechanic didn't see how he could adjust the stops in the wing. As it stands now, the plane seems to roll too slowly to the left and a better to the right but still a little slow. In level hands-off flight, I can see the left aileron is slightly up and the right is slightly down.

I'm based in Scappoose, OR (KSPB) and am looking for someone who specializes in checking the rigging in Decathlons with wooden wings. Does anyone know of someone I can contact? I'm up for flying a couple states away if it means I can get this addressed. Any suggestions are helpful.

Thanks!
 
The instructions in the Service Manaul for adjusting the travel seem fairly clear to me. I'm not an aircraft mechanic so I won't say any more on that subject.
After I bought my '79 Decathlon I had spades fitted and my mechanic told me that it was only getting about 2/3 of the correct aileron travel. The problem with mine was that the aileron gap seals had been incorrectly fitted and were restricting the travel.

Interesting that a recently rebuilt Decathlon here was discovered to have no gap seals at all. I wonder why some mechanics don't bother reading the manual.

You'd be most welcome to visit us here at YMMB - some top Decathlon mechanics are here.
 
Thanks for the reply; I appreciate the help. I took out my service manual and looked at the section on installing the aileron controls. It does look pretty straight-forward but also not being a mechanic I'm sure the devil is in the details. I think I'll head to the hanger today and double check the throws. My main concern is that I'd like the roll rate to be what it should before I start aerobatics. I'm new to the sport and am somewhat nervous to start if the plane isn't handling like it should. I also thought on my next flight I'd measure the roll rate with a stop watch to see if there's truly a difference rolling left versus right.

Is YMMB in Australia (http://www.liveatc.net/search/?icao=YMMB)? I'd be happy to find a Decathlon expert but that may be a little far from the US :)
 
If you adjusted the wash in the wings after spades were installed, you may have an issue with a spade that needs trimming counter acting the wash in the wings. I don't know if it will effect the actual roll rate, but it will sure make things feel different depending on which way you roll. I would take the spades off, and adjust the wash accordingly so the airplane will fly level without the spades. Reinstall the spades and then adust for a heavy wing by trimming the spades. You trim the spades by installing a washer between the spade and it's mounting bracket. One washer thickness is enough to cause a noticeable difference in feel.

Another good resource is aerobaticsweb.org. Sign up for the aerobatic email distribution. You can send out your post via their email exploder. It will reach a group of people with a lot experience on aerobatic aircraft.

Bill
 
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