Brodhead Pietenpol Association

Original Posted By: Bill Church
One of the other things that I think Bill was pointing out in his post, which I didn't catch on the first read through, is that if you are going to adjust the tail by shimming the front of the horizontal stab you will then have to adjust the tension for all of your empennage control cables. If you raise the front of the stab, the upper elevator control horn attach points are now slightly farther away from the bellcrank, and the lower attach points are slightly closer. The rudder control cable would probably need a bit of tweaking as well. Unless poor flying characteristics require you to make gross adjustments by shimming the stab (and is there evidence that a Piet built dimensionally to plans with the CG in the proper range is going to need that?), it would be probably be easier and quicker to adjust a couple cables via turnbuckles on the tail than it would be to install different shims on the stab and have to readjust the tension on 6 control cables....RyanOn Wed, Jan 6, 2010 at 11:41 AM, Michael Perez wrote:Bill, my response was based on the previous email reply, not a direct question of why cables are needed for adjustment. I took Shad's email as meaning, use the cables only to move the leading edge. That may not have been his intent, so I asked. There was no mention-of shimming. No mention was made about fine tuning either. I would not use the cables to adjust the leading edge of anything. The shim is the adjustment, the cables are the support. It sounded to me that, if the tail was not flying well, that the cables would be adjusted to twist the thing.-I am not a fan of twist. I believe my email explained itself quite well. Shim as needed, adjust cables to proper tension/correct alignment.-"...insert the clevis pin (assuming - probably incorrectly - that you're planning to use a traditional method of fastening the fork, with clevis pins). "-I thought I would make some balsa wood pins to slip into the fork and hold it there with thread.-As I stated, I have a handle on it now.------ On Wed, 1/6/10, Bill Church wrote:

Original Posted By: "Cuy, Michael D. (GRC-RXD0)[ASRC Aerospace Corporation]"
>This is confusing.You ask why you would need the cables to adjust the leading edge, and then you say that you would just shim the horizontal stab at the leading edge and re-adjust the cable tension to suit. That sounds to me like you're going to need your cables to adjust the leading edge.Every time the shimming is adjusted, all of your cable tensions will need to be adjusted as well, since the cable attachment points are not the same as the stab pivot point.A simple and effective method used by many builders for fine tuning the tail incidence , is achieved by simply adjusting the bracing cables, which DOES put a slight twist into the horizontal stab - but it is minor (probably visually imperceptible unless you're looking for it) - it is only for fine tuning.So, the short answer to your original question:"Sound, worthy idea or a waste?"would be the latter, but I guess you've already come to that conclusion.There are alternate methods possible, but turnbuckles are likely the most practical solution. If you use a swaged stud with a threaded fork, it will look nice and clean, but you'll have a difficult time making adjustments, as you'll have to disconnect the fork from the bracket, turn in or out the adjustment, then pull the cable tight to re-With turnbuckles, the tension adjustments are done with all of the cables in place. Bill C.Read this topic online here:http://forums.matronics.com/viewtopic.p ... 63#28036=- - - - - - The Pietenpol-List Email Forum -http://www.matronics.com/Na=======================" target="_blank">http://www.matronics.com/Navigator?Piet ... __________