Bracing for the flying strut

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Tbopper
Posts: 6
Joined: Sun Dec 09, 2018 7:15 pm

Bracing for the flying strut

Post by Tbopper » Tue Dec 11, 2018 11:32 am

I bought a Pietenpol Air camper project that is about 80% complete. While looking at photos of flying Pietenpols on this site I have noticed two vertical and a horizontal bracing about half way between the fuselage and the flying strut fittings. The two up right braces go from the struts two the bottom of the wing and the horizontal one goes between the two uprights at the bottom. The plans that I have; I believe, may be an original set and they do not show the strut braces. I could be missing a page. The wings have been covered and there is no fittings on the bottom of the wing for the braces to attach. Would this be something that was added in later up dated plans or something that is added by the builder? Either way I need a plan sheet, or help in how to get it done. Thanks in advance for any reply. Tbopper

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taildrags
Posts: 274
Joined: Tue Mar 07, 2017 10:39 pm

Re: Bracing for the flying strut

Post by taildrags » Tue Dec 11, 2018 10:48 pm

Tbopper; those are jury struts. They're very simple braces that help prevent the wing struts from buckling under negative-G loads and also help prevent the struts from getting into any sort of harmonic vibration. It is generally agreed that it's best to place the jury struts either above or below the midpoint of the wing struts so that it's even more difficult to create harmonic vibration in the struts. The ones you're describing form a "U"-shape and that's the way they are on my airplane (see picture). Mine are simple 4130 steel tubes with flattened ends, attached to tabs on the undersides of the wing spars at the top and to bolts that are welded into the lift struts at the touch points on them.
jury.JPG
There are older Piets flying with no jury struts at all, as well as some with just the verticals from each strut up to the underside of the wing spars (no cross-piece between them), and I believe the UK Piets are approved with just the leading edge vertical jury strut as on Alan James's beautiful G-BUCO, here:
download/file.php?mode=view&id=643

I hope this shows up OK...
Attachments
BUCO.JPG

EAB4
Posts: 61
Joined: Mon Mar 06, 2017 2:08 pm

Re: Bracing for the flying strut

Post by EAB4 » Wed Dec 12, 2018 6:13 am

tbopper
The early streamlined tubing used for the lift struts had internal ribs (drawing #6) to counter buckling or vibration, so jury struts were not used. (and so, not on the plans!)
Today's tubing does not have the internal ribs so jury struts are commonly added to the lift struts.

Tbopper
Posts: 6
Joined: Sun Dec 09, 2018 7:15 pm

Re: Bracing for the flying strut

Post by Tbopper » Wed Dec 12, 2018 6:30 am

Thanks for your reply. Is the tabs that hold the jury struts to the wing bolted through the wing spar? I am going to have to cut an opening in the bottom of the wing covering to get at it. Looks like learning baseball stich and patching is in my future. Thanks again.

EAB4
Posts: 61
Joined: Mon Mar 06, 2017 2:08 pm

Re: Bracing for the flying strut

Post by EAB4 » Wed Dec 12, 2018 8:29 am

yes they are

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