Brodhead Pietenpol Association

Original Posted By: JOEL CARROLL
Hello group,I have been folowing with interest the discussion about dragtruss bracing for the Pietenpol, and decided to share my ownexperiences with aircraft cable bracing with you.Don't worry about using 1/8 inch 7x19 galvanized steel cableand appropriate turnbuckles (if you can afford them!) for yourdrag/antidrag truss. Stainless steel would be better because of its corrosion resistance qualities, particularly if your airplaneis going to live in a corrosive environment.Stretching does not seem to be a problem in the Piets I have dealt with---except when they have been involved in an accident.About ten years ago two Piets landed from opposite directionsand ran into each other, heavily damaging the right wings of both machines. No injuries to either pilot resulted. They didn't see each other until the last second because the view ahead is limited withthe tail down. (There is a lesson here.)One a/c had 3/32 inch cable drag bracing and the other had 1/8 inch cable bracing. The lighter cable broke, but the heavier stuffdid not; a testimonial to its strength. Both were repaired and re-turned to service. It seems that 3/32 inch cable would be OK forthe outboard bay of the drag truss with 1/8 inch cable for the in-board bay, if you want to save some weight. I used 1/8 inch cable on mine (which was not involved in the above incident) for both inboard and outboard bays.Years ago, I had a 21 foot sailboat which used 1/8 inch 1x19 stain-less steel cable, thimbles, nicopress sleeves and turnbuckles tobrace the mast. Two nicopress sleeves about an inch apart wereused at each end, with the second one just covering the cable wireends to prevent snagging. Those cables really took a beating, hand-ling loads that would, I'm sure, far exceed the flight loads imposed on a Pietenpol drag truss---mainly because they were not preload-ed and gusts would snap them taut with a twang. Bending this cablearound a thimble to make a cable eye didn't seem to be a problem, either. One thing I would never use is fencing wire, and I am suspicious of any solid wire (or tie rod) which can fail completely without warningif nicked or damaged. It's much better to use aircraft quality cablesand turnbuckles for your Pietenpol drag truss. If in good condition, acable will fail all at once only when the load imposed exceeds its ul-timate strength. If protected from corrosion with a light oil, even gal-vanized 7x19 steel cable will last a long time (over thirty years in the case of my own Pietenpol). Incidentally, I used 3/32 inch SS cable for tail bracing on my a/c and it has been trouble-free. Cheers, Graham Hansen ________________________________________________________________________________Date: Mon, 26 Feb 2001 01:46:27 -0800 (PST)

Original Posted By: "Michael Brusilow"
Excellent link for a nice neat cheap and light approach! While browsingthru the parent sight I found a very good article on flying wires and howthe two main companies in the world differed in their construction method. Turns out one uses rolled threads on 316 stainless and the other used cutthreads! ( http://airbum.com/articles/Flyingwires.html ) What I have started with for my tail braces and may or may not change is3/16" 316 stainless rod threaded on the lathe with a die. With somethinglike 8 times the cross sectional area (probably only 6 times or so at thethread root) than the 14 gauge wire I would expect there is plenty ofstrength. I distinctly believe the whole rolled versus cut thread debateis great theory but much less applicable in practice unless you areengineering things to minimum diameters. I would be surprised if there isa single rolled thread on any of BHP's first several piets. To insure no one takes my word as gospel I must add I am not an engineeror have any background in the threaded fasteners industry but what I haveread on the subject does not give any outright answers like the Thoughshalt not use cut threads that is propagating in this "thread." Wayne Sippola, Winnipeg > BTW, I decided to use the Bob Barrows tail wire approach> However, I do not plan> on turning down the wires.> > Ken Beanlands B.Eng (Aerospace)> Calgary, Alberta, Canada> Christavia MK 1 #363, C-GREN> Barrows Bearhawk #468> > > > On Sun, 25 Feb 2001, Graham Hansen wrote:> > > > > One thing I would never use is fencing wire, and I am suspicious of > > any solid wire (or tie rod) which can fail completely without warning> > if nicked or damaged. It's much better to use aircraft quality cables> > and turnbuckles for your Pietenpol drag truss. If in good condition, a> > cable will fail all at once only when the load imposed exceeds its ul-> > timate strength. If protected from corrosion with a light oil, evengal-> > vanized 7x19 steel cable will last a long time (over thirty years inthe > > case of my own Pietenpol). Incidentally, I used 3/32 inch SS cable > > for tail bracing on my a/c and it has been trouble-free. > > > > Cheers, > > > > Graham Hansen > > > > > ________________________________________________________________________________