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Wing strut covering?

12 posts in this topic

Posted

I finally got around to working on my wing struts. I filled and sanded the trailing edge to the wing strut. I then used epoxy varnish on the wooden trailing edge. It turned out so smooth that I was wondering if anyone has just painted it at this point?

Is there a benefit of fabric covering these?

Thanks,

Ron

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Posted

Maybe just the uniformity of the surface texture?

The fabric adds a little strength, but not much.

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Posted

Mine are just painted.  Not sure if good or bad.  The bottom few inches separated on the pilot side, and I was thinking I need to redo the wood fairing to fix it.  BEFORE I read Lennies advice on fast taxi, I took care of that problem, and the entire strut now needs rebuilt.  There was definitely rust between the wood fairing and the strut tube.  Now was that because the fairing wasn't secured with epoxy well enough, or did the flexing from flight stresses cause it to separate?  Would a fabric overlay helped keep them together, or at least provide another moisture barrier?  Don't know.

 

I notice that Wicks now has aerodynamic 4130 tube - shaped pretty much like the lift strut tube after the wood goes on.   Any thoughts on whether that would be a good idea to rebuild with?  I know Dean sent out a bulletin that the wood fairing was structural (provided stiffening to the strut) and should not be omitted, but would the tube in that shape provide the same stiffness?

 

Mark

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Posted (edited)

Mark,

       There have been cracking issues in the past with the streamlined tubes - That is why they were unavailable for some time - also, they are far more expensive than the round tubes.

        Piper used them on the Cub, and they were treated inside with linseed oil - finally, the FAA issued an AD that they had to be inspected regularly with ultrasound equipment - A lot of owners opted to buy new struts instead of the expensive inspections.  I have a set of the old Cub struts in my storage, but they are too heavy for my Foxy.

        Cessna, and a few others (RANS?) use an aluminum streamlined strut tube.  I think they are expensive too?

I believe that wrapping the strut tubes and the wood fairings with fiberglass might seal out moisture better, but it would add a little weight over using fabric, which may not stop moisture.    The tubes should be painted with a good epoxy before gluing the wood.

EDMO

Edited by Ed In Missouri

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Posted

Wrapping with fiberglass was my first choice when I rebuild the struts, so I'll just do that.  I could use the fiberglass finishing practice anyway.  Mixing and spreading micro is so much fun!

 

Mark

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Posted (edited)

Mark,

       I think that if you make the 1" x .049 wall struts, you could eliminate the wood altogether, and just use foam form and fiberglass - Kitfox only uses fiberglass.    I had intentions of using these old Piper struts as a pattern for making fiberglass fairings, but I think it would seal better if the fiberglass was just laid directly over the expoxied struts.   You should not have much trouble with finish if you lay the fg the same way the book says to lay the fabric on the struts, and apply a good topcoat of epoxy.

EdMO

Edited by Ed In Missouri

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Posted

Mark,

My landing gear on my Starduster Too is made of the aerodynamic 4130 tubing. I don't know how thick the walls are? It has held up since 1975 and survived some pretty good abuse, of course not by me :) other less skilled pilots of course! I would think the weight would be close to the same as the tube with the wood fairing and be a lot stronger too. I wonder if anyone uses that tubing for struts on other planes?

I'll look around...I would like to know why or why not...

Ron

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Posted

Look at the struts Univair makes for the pipers. Aero shaped tubing.

IMO this stuff would work great for lift struts, with the exception of its extreme cost.

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Posted (edited)

Extreme cost and weight - my Piper struts weigh a lot more than the 1" tubing for my Foxy. I have 4 J3 struts that I will sell.

EDMO

Edited by Ed In Missouri

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Posted

Bringing this back with an emphasis on strength. I am in the same boat and ready to cover or paint. I'm not 50/50 on what folks seem to think is the right way to these. I think paint would be easier than covering but a few I've talked to said the covering adds strength. I'm not yet convinced. Thoughts?

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Posted

If I wanted strength - and I am assuming you are talking about the strut fairings - I would cover them with a layer of fiberglass to prevent corrosion from the next layers of carbon fiber.  EDMO

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Posted

Bringing this back with an emphasis on strength. I am in the same boat and ready to cover or paint. I'm not 50/50 on what folks seem to think is the right way to these. I think paint would be easier than covering but a few I've talked to said the covering adds strength. I'm not yet convinced. Thoughts?

It wouldn't surprise me to know that fabric would add a little strength. Basically it gives it more area that is attached and could take shear loads in different directions. Not sure how much, but I have seen how fabric is somewhat structural in certain applications. However if you are going for strength I have to agree with Ed, fiberglass over it with two layers. You'd be surprised how much stronger it will get if the bid is set in the right orientation. 

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