Fiberglass strut fairing POC

22 posts in this topic

Posted

So I wanted to see if it’s a viable option, and prove my concept. I went Uber cheap materials, stuff you can buy from Lowe’s, I did minimal man hours so that I wasn’t wasting all this time on a burner piece. Someone may poke holes in it, but I plan on scaling up. I took insulation foam from Lowe’s, cut out 2” strip by 22”. I shaped it with a wood file very quickly to the dimensions I’ve seen on this forum. 2 layers of fiberglass I bought at Lowe’s, with epoxy resin also bought at Lowe’s. Then I used short hair body filler all over. I think the body filler will add tons more sanding work, so on scaled  up version probably just add a 3rd layer. Ended up weight .18 oz per inch...calculated it for 4 8ft long struts comes out to 4.3lbs. This is a rough estimate as a 3rd layer of fiberglass may be heavier than the filler.

8220C424-7FC2-49EF-8A4E-6F161AF55717.jpeg

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Posted

After routing and shaping I added 2 layers of cheap Lowe’s fiberglass and epoxy resin made for “glazing” counter tops

E413B7CD-90A4-4755-B4F4-4EE00DEE79C1.png

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Posted

After epoxy cured I trimmed up the edges and used short haired bondo

9C2FDE38-A3C8-412C-AB1B-91237FA62022.png

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Posted

I was gonna start in on some sanding and finishing work but didn’t think the juice was worth the squeeze. I’ll use this piece to do some measuring and figment work

2A5D9014-2E56-4365-B5B9-109200562390.png

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Posted (edited)

The piece resulted in a extremely rigid foam cored fairing...somethings I’ll do different scaling up:

order good fiberglass and epoxy

Mount to a wooden dowel to keep epoxy and such from encroaching the trough and allow it to be able to stand vertical

use 3 layers of fiberglass instead of a filler layer, just adds too much labor to sand

i think I can get the same shape with a table

  saw vs hand carving 

 

 

 

Edited by Matthewtanner

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Posted

I'm looking for it in the Mike Arnold videos but he made his landing gear strut fairings by bending sheet metal into roughly the right shape but open enough he could lay the fiberglass up inside it and then he just riveted the trailing edge together. The smooth surface of the sheet metal meant he didn't have to do any surface finishing.

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Posted

 

This is the video. At about 4:40 he starts talking about fairing design and about 8:00 he shows how he bent the sheet metal to make his mold. I thought he layed up the fiberglass on the inside ( female mold) making the exterior surface of the part smooth but he used a male mold. A guy in my EAA chapter showed me how to use plastic sheet over the surface of the layup to make it nice and smooth. These techniques ought to reduce the amount of work considerably. 

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Posted (edited)

I gave this some thought after reading these posts, and will need to be doing something on my Kitfox 4 as well when the time comes.  Here is what I came up with that may work.  I figured to maybe use a couple of 2"X6"X4' boards to make the mold.  They would screw together, and unscrew to take the formed and hardened fairing out.  Cut the boards out to form the mold.  If you run boards through a table saw at an angle, you end up with a curved cutout.  Other ways to do it as well I'm sure, but that is one way to do it.  What may work, (I haven't done it yet, so can't say "will work") is lay a piece of plastic into the mold first of all, (perhaps glue it in place with contact adhesive)  then lay in the 3 layers or so of fiber glass cloth that is saturated with the resin.  Then slide in the pre cut piece of 1/8" or 1/4" plywood that will go to the back point of the fairing, and the front of the plywood will just touch the back of the lift strut tube.  May have to put something in to keep the plywood from tipping to the side.  Then slide in a piece of steel tube with packing tape around it to keep the fiber glass from sticking to it when it cures.  Once the fiberglass cures, unscrew the boards from each other, pop the steel tube out, trim off the excess fiberglass, and you can then epoxy it to the back of your lift strut tube.   I think this will work, and intend to try it when I get to that point.  Hope this makes sense.  JImChuk

 

strut fairing mold .jpg

Edited by 1avidflyer

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Posted

While ya'll are monkeying around with the fairings please remember that they are indeed structural.  Unless you address the structural issues (I made mine out of 1" X .058" tubing) then you need the wood fairings installed, or something that will give you the rigidity of the wood fairings.

:BC:

 

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Posted

Im thinking make out of some kind of good strong all weather wood, glue them to wingstruts (obviously) them make it easy by wrapping it all in 2"-3" wide trim tape from Auto Trim Design in my choice of color to match or contrast the color of plane. 

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Posted

While ya'll are monkeying around with the fairings please remember that they are indeed structural.  Unless you address the structural issues (I made mine out of 1" X .058" tubing) then you need the wood fairings installed, or something that will give you the rigidity of the wood fairings.

:BC:

 

You're probably right Leni,  my Kitfox 4 project flew for about 640 hrs with no fairings, but it does have the 1" lift struts.  JImChuk

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Posted

No probably about it, at least for Avids.  Dean addressed that in one of the newsletters or a service bulletin.

While ya'll are monkeying around with the fairings please remember that they are indeed structural.  Unless you address the structural issues (I made mine out of 1" X .058" tubing) then you need the wood fairings installed, or something that will give you the rigidity of the wood fairings.

:BC:

 

You're probably right Leni,  my Kitfox 4 project flew for about 640 hrs with no fairings, but it does have the 1" lift struts.  JImChuk

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Posted

While ya'll are monkeying around with the fairings please remember that they are indeed structural.  Unless you address the structural issues (I made mine out of 1" X .058" tubing) then you need the wood fairings installed, or something that will give you the rigidity of the wood fairings.

:BC:

 

that was my goal was to use fiberglass to strengthen it, if not I was just gonna use foam with duct tape, which is what I’ll probably do for all the other tubes

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Posted

On this same topic, what kind of wood was used in the original fairings? I think I'll just have some made.

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Posted

I believe it was Spruce.  I just bought a truckload (literally) of Spruce when Wicks had an inventory clearance auction last month.  I need to remake the fairings, since I found some rust under mine, and there is no way to get them off without damaging them.  I had priced the spruce several times, but never bought it because it pissed me off that shipping was almost twice as much as the spruce I needed (long length, UPS no likee).  I thought I was getting a small cartload from the picture on the internet, but it was a BIG cartload - filled the 8' bed of my pickup to the top.  I was afraid I'd have to take the cover off!  Admittedly, a lot of it was oddly cut, but I still ended up with enough good stuff to make a lot of parts from.

The trip to get it cost about the same as shipping the pieces I really needed, but I got a lot more (plus a few other things - you know, auction!), and the spruce was really cheap.

Mark

 

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Posted

I just used clear pine from Menards. Pick a few boards up and buy the lightest ones and that look strait.  Think you could also use Mahogany that usually feels lighter yet but I wanted the strength of Pine. 

100_1127.JPG

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Posted

Got weight on those bad boys? Honestly probably just as light and waaaaay easier to make

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Posted

Got weight on those bad boys? Honestly probably just as light and waaaaay easier to make

Its been a while but I think by drilling the holes I got them all to 1.37lbs each

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Posted

I talked to a local cabinet maker about having some fairings made. He said he could do it. Haven't heard back yet on the cost.

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Posted

when you install the wood PLEASE make sure you prep the tube well (media blast is best) epoxy them on good then completely seal it up!  Wood holds moisture, moisture next to metal tubes leads to.. drum roll please..... rusted and pitted struts!

There are pics way back on the forum somewhere of mine that were rusted and pitted when I got them.  Since I was going for float ops and would have water spray all the time I went with heavier struts and used the plastic fairings from kitfox.  This allows the struts to "breath" and any moisture to dry out.  If I were to do it again I would probably just replace the struts and use the stock tubing and fairings as I added a lot of weight to my bird.

If you hangar your plane its probably not that big of a deal as everything has a chance to dry out completely.  I leave mine out in the elements year round.

:BC:

 

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Posted

when you install the wood PLEASE make sure you prep the tube well (media blast is best) epoxy them on good then completely seal it up!  Wood holds moisture, moisture next to metal tubes leads to.. drum roll please..... rusted and pitted struts!

There are pics way back on the forum somewhere of mine that were rusted and pitted when I got them.  Since I was going for float ops and would have water spray all the time I went with heavier struts and used the plastic fairings from kitfox.  This allows the struts to "breath" and any moisture to dry out.  If I were to do it again I would probably just replace the struts and use the stock tubing and fairings as I added a lot of weight to my bird.

If you hangar your plane its probably not that big of a deal as everything has a chance to dry out completely.  I leave mine out in the elements year round.

:BC:ut

 

I got a couple of sets of struts off a Taylorcraft a couple of weeks ago for free. They look just fine and that's the rub. The A&P that gave them to me said the service life was up on them so he replaced them with new. He said you can have them X-rayed to keep them flying but they charge you $400.00 dollars just to X-ray them. We run into the same problem with our struts once they are complete; there's no cheap and easy way to tell if they haven't been compromised by the elements over time.

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Posted

original struts for cubs and t crates have the service life and xray requirements.  Univair and a few others have made "lifetime" struts.  One good thing about cub or tcrate struts is that they are longer than what we need for ours so you can cut the ends off, look in them with a borescope and then cut them down to the length we need for ours.  Most times you can get the old struts free.

:BC:

 

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