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PLASTIC STRUT FAIRINGS?

32 posts in this topic

Posted (edited)

I have been looking thru my GRAINGER catalog at sheet plastics - someone with engineering expertise in this area might be helpful.

After considering all types of material, including aluminum sheet, fiberglass wrap over wood/foam, the lexan sheet that Joey suggested,  I think that possibly the easiest material to make the fairings out of might be PVC sheet, which you can get in 1/16" (.062") thickness, easy to cut and bend, and the trailing edges can just be glued together with PVC Cement.  I didn't find a weight listed for this to compare with aluminum.  I was hoping to find PVC sheet in 1mm (.040") but don't know if anyone sells it in metric sizes.  I guess the 1mm Finnish plywood I used on my extended leading edges could be used for this and save weight, but then you have to varnish / paint it which adds the weight back.

I cant see paying Kitfox a fortune for something that is so simple to make - If we just come up with the right material. 

I could mold some with fiberglass on J3 struts, but that is so messy (and itchy!) to work with.

After I get my struts finished, I just might be the guinea-pig on this.

Anyone have other ideas?

EDMO

Edited by Ed In Missouri

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Posted

Hey, I don't have much to add to this, but I'll be interested if anyone comes up with a new idea for strut fairings. I think the idea that Joey posted might be a good one to keep weight down.

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Posted

Hmm, I'll think about this while I'm rebuilding my struts.  There was corrosion under mine where the epoxy hadn't sealed completely, so I'd like something different, that would still meet the stiffening requirements that Avid wanted.  I may look at fairing them like I will the gear legs on the Cozy I'm not building....  Make the fairing out of foam, then glass it over with a couple of layers of BID and laminating epoxy.  Should be as stiff as the spruce fairing, but seal up better with no chance of delaminating, plus not a lot more weight than the spruce fairing.

Mark

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Posted

mine were corroded really bad under the wood fairing as well.  If you live in a desert I dont think this is an issue, but if your on floats, or in a high humidity environment, I dont think the wood fairings are a stellar idea.  That is why I went to 1" .058" struts so I could snap the KF fairings over them and still have lots of rigidity.

 

:BC:

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Posted (edited)

Leni,

     How much were the fairings?  I cant find them in my KF catalog.  Were they shipped full length?

About how thick is the material?

     I took the fabric and wood off of my KF2 struts and did not find any rust - the metal looked like it only had primer on it, along with some epoxy glue and some dope bleedthru.

Thanx,

EDMO

Edited by Ed In Missouri

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Posted

Page 56 of the online catalog - 'Speed Fairing Kit' - list $295.00 part # 69119.000

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Posted

you get 4 full length pieces and a chunk of semi formed aluminum to screw onto the bases of the fairings where they come together.  The onlythink I dont like about them is they are heavy, but the speed and climb gains made them worth it.  They just snap in place at the trailing edge and you have to cut out for the jury struts.  All in all I think I had under an hour installing them.  You could do the same thing with thin aluminum and a few rivets on the trailing edge and it would be much lighter.

 

:BC:

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Posted (edited)

I wonder if there is an epoxy that would bond the trailing edges of aluminum fairing together - I don't have a lot of hair left and it hurts to get it pulled out by the blind rivet tails - don't like blood in my hair either !  Guess if you put the rivets in from the bottom side and filed the stub it wouldn't be so bad.

EdMo

Edited by Ed In Missouri

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Posted

I was thinking squeezed rivets not pulled.. for something like that all you need to do is get a pair of vice grips, file the teeth off, use an over size drill bit to put a little dimple in the faces then use a couple practice rivets to get the screw set right so you get a perfect squeeze on them. 

 

When John Stoner was building the wings here for Dakota Cub there were a few rivets he had to do that you couldn't get the bench mounted squeezer on so he made a couple tools as described above.. one made from needle nose worked great to get into small places that you couldn't get any other commercially available tool I have seen into.

 

There are lots of sealers and epoxies you can use to join the trailing edges, but I don't like relying on only glue on something like that.. a good strip of gorilla tape around the trailing edge, but not glue :lmao:

 

:BC:

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Posted (edited)

Thanks for the rivet tips Leni - I can use that soon.

      What thickness of 6061 would you recommend for the fairings?  Weight vs Dents / Warping....

I thought about just a couple of blind rivets at top and bottom (maybe center?) of struts and seal the rest with epoxy?

EDMo

Edited by Ed In Missouri

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Posted

or you could just use a break and bend the aluminum over just like the trailing edge aluminum used on the wings then you would just have to hysol them onto the struts and wrap the whole works with fabric. thats what I'm planning to do when I make the new struts

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Posted

Why does everyone hate the wood farings so much?  It's cheap, strong, easy to do and light.

  1. Drill 2" holes in it down it's length.  (Chips will weigh 4#)
  2. Varnish the wood on all sides after its sized.
  3. Hysol it in place. (touch up varnish if needed) 
  4. Cover with fabric and finish it to a complete weather tight seal.

When properly finished, attached and sealed with fabric, there should not be any moisture to create corrosion underneath the wood.

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Posted

Larry,

      It may be that some of us don't have the wood fairings and are looking for cheap alternatives.

EdMO

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Posted

I haven't tried it yet, but my plan is to hysol a strip of 3/32 plywood to the trailing edge of the strut and wrap it in orotex.   Orotex is pretty easy to work with and tough as nails. It should also be a lot easier to fare out the root than the plastic  farings. 

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Posted

Larry,

      It may be that some of us don't have the wood fairings and are looking for cheap alternatives.

EdMO

 

 

If you have a few Douglas Fur 2x4s, a table saw and maybe a router you can make your own.  That's how Brett makes his.

 

If you don't have these tools, find a local cabinet shop to cut them.  (Just be sure to tell them it's a crown molding!)

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Posted (edited)

I think I will just get my aluminum supplier to shear some 8 foot strips of 6061 for me - Quick, easy, and light.

Thanks,

EdMO

Edited by Ed In Missouri

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Posted

I put strut fairings on my Buzzard and picked up about 10 mph. My climb is also much better and flying with two on board is much easier.  Strut fairings are the best thing I have done to this plane ever.  I built mine out of thin aluminum flashing from home depot.  (used the type that was brown on one side and white on the other)  I used an eight foot break and put two folds into the material.  then wrapping it around the tube I riveted it at the rear and attached to the struts with spray foam.  I used the thin aluminum to test the effectiveness of the mod.  It is certainly worth doing.

Norm

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Posted

Norm,

     How wide was the material you used for the strut fairings?  What was finished width?

Thanks,

EDMO

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Posted

I think I started with about 8 inch.  I did one break at 1 inch and the next break at 3.5 inches.  I did not think the thin material would work but when you wrap the one inch tube it forms nice.  I then rivited the bottom of the 3.5 inch piece to the one inch break which hides the rivet inside the fairing. Did this at the rear of the fairing.  I then filled the fairings with spray foam to make the fairing stay in place and add some structure.  I sprayed the foam into each end and also at the jury strut opening.  I may end up doing it again and maybe use .024 Aluminum for the material.  I am super happy with the results.  A person could tweak the planes till your blue in the face but I think I am done tweaking this bird as I have a KitFox IV to re-Cover.  Now that is another major project.  I keep adding things to the want list and so far I have put the speed tail mod on and the wide body mod.  Looking at a good cargo area mod but that is not as important as I am normally a short hop pilot.  So many planes so lttlle time.

Norm

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Posted

Instead of Hysol or JB Weld, I would like to humbly suggest using RTV silicone sealer or "shoe goo". You need to be able to remove the fairings every few years to inspect for corrosion, or cracks, or replace hardware, etc. If you epoxy the fairings onto the struts then you will be very very un-willing to remove the fairings later for routine long-term maintenance. If you hold the fairings on with a blob of Shoe Goo every 12 inches, you can carefully slice through the glue and remove the fairings without too much bloodshed..

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Posted (edited)

I thought about making mine out of aluminum sheet, using some type of Adel clamp setup at top and bottom, and sealing with GE Silicone II - that way, when you unbolt the clamp, you should be able to slide the fairings off of the upper end of the strut for inspections. But, if you blast the struts, and use a good epoxy primer and epoxy paint, then there should not be any corrosion to look for.

EDMO

Edited by Ed In Missouri

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Posted

Ed,

 

Time and again, no matter the prep, unless you live in the desert, it has been proven that these struts do corrode and do have issues when you put the wood fairing on them.  Mine were HAMMERED and I think I have pics of them on the site some place. 

 

I used the kitfox plastic fairings and they are just snapped on and I have a few wraps of gorilla tape at the lower end to hold them from twisting for the most part.  This was meant to be a quick fix when I put them on just to see if the weight gain of the heavy plastic fairings was worth it... I have been too damn lazy to put on the aluminum sheet that was supplied with the kit to fix them right.  One of these days I may clean it up and get rid of the gorilla tape :lmao:

 

A few dabs of silicone or 5200 was my plan for permanently holding them in place as EZ suggested.

 

:BC:

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Posted

Leni,

    As I said, " I plan to use aluminum sheet on my struts".

Thanks,

EDMO

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Posted

I was looking at a Challenger II in a buddy's hangar the other day and noticed some fairly cook plastic (PVC?) farings over the lift struts.  Might be something worth looking into...

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Posted

Larry,

Any way to get a price or supplier for those Challenger fairings - Might be cheaper/lighter than Kitfox?

EDMO

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