bobmarkert

bobmarkert

Well Known Member
My fairing rough work is done and now I want to work on the finish fiberglass. My question is:

If there is an uneven transition between parts do I start with a thin layer of glass cloth then finish with SuperFil / and or epoxy and microballoons on top or should I put the filler down first and then glass cloth on top. All suggestions appreciated.





Thank you
 
I put the filler on first, then the glass strips. It still required a bit more filler/micro afterwards. My thought was that the initial filler added a bit more support (although not structural).
 
I assume you're interested in filling the seam between the polyester/glass empennage tip and the aluminum.

I'm 4-1/2 years and 450 hours into an experiment...no glass fabric over that seam.

The flange on the empennage tip, and the adjacent surface area, was sanded to remove the gel coat. The underside of the aluminum was sanded for tooth. Structural adhesive was applied to the flange, the parts were assembled with clecos, and the rivets were installed while the adhesive was still wet. The goal was a firm foundation, i.e. no relative movement between the dissimilar materials. The seam was later filled with ordinary dry micro, which seems to be doing fine. There are no paint cracks at this time.

If you wish to add a ply or two of glass cloth, fill the seam first, using dry dry micro.

Work on closing and finishing the ends of the tips before you fill long seam. Mount the elevator on the stabilizer hinges, adjust them properly, and trim the ends of the tips for a suitable gap. Now fixate the elevator in trail with the stab, which will allow you to match up the profiles of the stab and elevator tips. They don't necessarily match right out of the box.

 
MeAndMyToys said:
Dan, what did you use for "structural adhesive"? What did you use for support in the open tip?
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Probably Hysol 9430. T88 would probably work fine too.

Closed the end with 1/16" birch plywood, glassed on both sides. Do a flox filet on the back.
 
What and where

Thanks Dan,
One more question please
when do I use Epoxy/Flox, When do I use epoxy/microballons, and when do I use SuperFil?

Ok that was really three!

Thanks
Bob
 
I believe Dan will say, micro balloons and super fill are just fillers and are used when you do not need any structural strength. These are easier to sand. Flox and epoxy mix is used when you need some structural strength and is much harder to sand unless you catch it early in the cure process when it is "green" or not fully cured. You can do a mixture of flox and micro balloons to make it a little easier to sand and have a little strength also...I purchased a package of super fill and used it building my plane but if I had to do it over again I would have spent that money on something else. Dry micro mix does the same thing as super fill. Spend that money on a can of fast hardener for your epoxy kit so you can have a faster cure on small batches and you can sand earlier. A choice of fast hardener and slow hardener will give you much more versatility with your mixes.
 
Thanks

Thanks Mike. I only use the fast hardener (205). Both you and Dan said "dry micro" Am I correct that that that means a very thick mixture paste made buy adding a lot of micro to the epoxy so it is not runny at all?
Bob
 
Yes, when I first started mixing micro, it would always run off from where I wanted it! Then I would mix a little flox with it to help it stay put, but that would make it harder to sand. I bought some cabosil and mixed a little of it in the batch and that would really thicken it up and it worked good but the main problem was, I just wasn't mixing it dry enough. You have to keep adding a little micro at a time to get that just right mixture.
 
I read this thread http://www.vansairforce.com/community/showthread.php?t=22931 by Dan H. About 15% soaked in my thick skull the first time I read it so I had to keep going back and reading it ever now and then. Fiberglass work is probably the most time consuming and frustrating thing I did on my plane but I have really enjoyed it and have learned so much! To think, you can build anything or any part you can dream up, using these methods and materials just amazes me! I wish I had learned this 30 years ago!
 
Bob,
here are two pics of my stab tips and elevator horns. I did not blend in the stab tip, just riveted it on. If it ever gets damaged it is very easy to remove. I should have filled the hole in the pop rivets with micro however, but actually I don´t mind how it looks. The elevator tip is roughly blended into the aluminum only with dry micro - easy to sand. Don´t know however why I did blend in the elevator tips but not the stab tips.
Whatever you do finish the elevator tips first then the stab tips.

Hermann





 
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Superfil question

Dan reports Good results with epoxy / micro filler between aluminum and glass components. I had been noticing West 105 would readily peel off aluminum skin as though there was release tape under it. SO, I read here that superfil adhered well to aluminum and assumed it used vinyl ester resin or something other than epoxy to bond to aluminum. I start filling empennage joints this week. Should I sand and etch the aluminum for micro or just use superfil and follow instructions ?
 
Larry DeCamp said:
Dan reports Good results with epoxy / micro filler between aluminum and glass components.
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Dan reported good results with Hysol 9430 between aluminum and glass.

I had been noticing West 105 would readily peel off aluminum skin as though there was release tape under it. SO, I read here that superfil adhered well to aluminum and assumed it used vinyl ester resin or something other than epoxy to bond to aluminum.
Click to expand...

Both West 105 and Poly Fiber Superfil are based on bisphenol-A epoxy resin. Retail epoxy brands buy their base resin from the same major chemical producers, as actual production of epoxy resin starts with oil and natural gas. For example, the base resin in Superfil is Dow Chemical 331; you can ID it from the registration number on the Superfil MSDS. There are lots of different resins available. Some are pumped in one door and sold in cans out the other, and some are used as building blocks, with additives by the retailer.

I start filling empennage joints this week. Should I sand and etch the aluminum for micro or just use superfil and follow instructions ?
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In general, all epoxies should be applied to a roughened surface. That's even true of epoxy over cured epoxy.

I've not studied the fine details of increasing bond strength or longevity to aluminum. There are modified specialty epoxies for the purpose, Hysol being an example. In the context of common surface and laminating epoxies found in the home shop, I have shop-checked a West/105/glass micro mix against Evercoat Rage Gold (a very popular polyester base bodyshop filler) on prepared aluminum coupons. The epoxy/micro mix exhibited far better adhesion. I would expect Superfil to be the same. Frankly, I would not expect any performance difference between mixed-at-home dry micro and Superfil, other than a significant variation in wallet mass.
 
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Similar technique

I don't know why everyone is so afraid of glass work:eek: This is the one area that is easily fixed if you mess it up!!!

I use pretty much the same process and materials as Dan. I used structural foam to cap the ends with glass over the foam. Light and easy to work with.

When the parts were riveted I used a thick blend of epoxy and micro, clecoed everything then riveted. Use the excess splooey to fill the seam. Old credit cards and hotel room keys are great for this.

For light filling, I use Evercoat 416 glazing compound. It fills nicely, is light and sands easily. You MUST insure the metal is thoroughly scuffed and clean for any epoxy or fillers to bond.

The only real difference in my technique and Dan's is that I always cover the seam and fill areas with a layer of 2 ounce glass cloth. My plane had 800 hours when sold and all glass areas were in perfect condition.

When done, use a good quality high build primer on the work. Spray a light "guide" coat of black over the primer. This is just a light dusting. Now sand and the guide coat will show you the low areas. Lather, rinse repeat:D
 
One thought for you. While I like the look hiding the seam, I realized that if my plane suffers hangar rash, it will probably be on the fiberglass parts. Thus, I didn't hide the seam so that should I have to replace a part later on, I wouldn't have to fix a lot of the paint.

Just another guy's way of getting 'er done so he could go flying.

(Granted it doesn't look as good as Dan's but then not many planes do.)
 
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