When I was first considering building my own airplane, I settled
on the Glastar. I didn't know anything about composite (fiberglass)
but, then again, I didn't know anything about building airplanes
either so I figured I was OK. I liked the fold-up wings and figured
I could trailer the airplane the way Minnesotans trailer their
boats. And so I sent my $1,500 deposit for the the tail kit. The
next day, the company went bankrupt.
I took that as a sign that composites were not for me and as
I've worked on my RV airplane over the years, I've considered
it divine providence that I didn't subject my family to the chemicals
or the mess of building a composite airplane. Oh, and I hate sanding.
But as ye olde airplane project gets closer to finishing, fiberglass
cannot be put off any longer. There are empennage and wing tips,
and the canopy fairings, not to mention a big honkin' piece of
fiberglass that covers the engine.
I read as much as I could about fiberglass from Tony Bingelis,
I also read -- many times -- one of the best online tutorials
about working with fiberglass -- Fun
with Fiberglass. And a year or so ago, my friend Darwin Barrie,
perhapsthe RV world's premier fiberglasser thanks to his years
assembling RC airplanes, wrote a
terrific piece on the RV builders Yahoogroup. I also stopped
in to the composite workshop during AirVenture 2008, and I bought
Sam James' Fiberglass 101 video, which, while interesting, didn't
really help me that much in preparing to make my fiberglass fairing
for the canopy of my RV-7A. Another interesting source is Leo
Benetti-Longhini's how-to on installing
the rudder fairing, which he wrote in 2000.
As you may know if you read
Letters From Flyover Country, I've pretty much finished the
fairing project. It came out pretty well, but wasn't without hassle,
and I think I could've done better if I'd been better prepared.
So maybe this will help you on your RV fiberglassing efforts.
This article, of course, is not intended to do much more than
scratch the surface and provide some additional tips. There are
far better places, for example, to learn the basics of fiberglassing.
A great source is the supplier-of-choice: West Systems. Their
user manual has vital information for working with epoxy.
West is primarily a boat-building/repair company, but you'll find
fiberglass is fiberglass and doesn't know its final purpose.
In this article we once again visit the best and brightest RV
builders -- you. I asked subscribers of RV Builder's Hotline to
share their tips on working with fiberglass.
So let's go to the tips!
In
all probability, your first encounter with fiberglass will be
either enclosing the ends of the horizontal stabilizer tips
Matt Dralle, owner of the RV List, recently completed some of the fiberglass work to enclose the open ends of the tips, then mounted them to the vertical stabilizer, elevator, and rudder.
"I took a very minimalist approach to fiberglassing the empennage tips on my new RV-8 project," he told met." I figured its an airplane made out of rivets and screws; why should I try to hide that fact when doing the fiberglass work on the tips?
He's sent along some pictures, adding he's "very pleased with the look and function of the tips. It was also a whole lot less messy than glassing over that tip-to-surface intersection. Best of all? I know I'm not going to end up with a crack in my paint job down the road where the fiberglass tip intersects with metal - there's a natural one there already. Another benefit is that all of the tips are attached with screws and platenuts. If I ever have to remove or replace a tip, I won't have to completely ruin the paint job in the process."
Here's a few pictures.
But here's the problem I ran into when adding my tips. I didn't pay attention to the drawings where it said to trim back the flange of the outside rib on the horizontal stabilizer. You've got to pay attention to the drawings in the early part of the project because if you don't, it'll impact the end of your project. On the tips, there's a molded recess, but if you want only to attach them without glassing over the intersection, you have to trim that recess to allow for a flush fit. In my case, this meant having an edge distance problem on the fiberglass. I made sure to add in an aluminum strip on the inside of the tips, and extended them slightly, angling them higher to fit over the flange of the outboard rib.
The first extensive fiberglass work in an RV is usually
the canopy windscreen fairing. The Van's instructions are pretty
complete on the latter. Last month, Van's support guru Joe Blank sent me a very nice guide.
Here is the way I prefer to finish out the fiberglass strip on either the slider or the tip-up style canopy.
Once the multiple layer glass cloth/epoxy layup is completed/molded and set, if you haven't defined the strip width already using tape, do that now. I prefer to use black electrical tape. You can make nicer curves and contours, and the epoxy won't wick under the tape edge. You can vary the width of the fairing a bit around the corners to make it look more esthetically pleasing to the eye. Lightly sand the area to eliminate any high zones. Next, mix up a baseball sized amount of either micro-balloons (glass beads) or a product called "Superfill" (from Spruce).
I prefer the Superfill, as it's light, the right consistency, and is very predicable. Using a 4x6" piece of plastic or cardboard as kind of a squeegee, apply the filler to the taped off area. You can start in the middle and work to the outer edge or start on one side and work to the other, as it really doesn't matter. (I call this arts and crafts at this point ;-) Symmetry is the name of the game here, to simply make both sides look the same. If an area looks too low, then add a bit more material. If an area looks to high, then use a bit more pressure on your squeegee to scrape it down. Use the squeegee action to form a nice smooth surface. Once you have enough material on and are reasonably happy with the results, step away from the work! Let it set up for a day or so.
The next day, come back and inspect the work and determine if there are any high/low spots that need to be addressed. Circle these with a sharpie so that you only try to repair these spots. Once everything else looks acceptable, it's time to sand. Fabricate 3 sanding blocks from wood that approximate the shape of the fairing in the center, halfway to the outboard edge, and at the outboard edge. I simple cut several pieces of cardboard that mimicked the shape and held them up to the the fairing.
Using progressively finer grits of sandpaper and the blocks, lightly sand each zone until you get the exact contour you like. Once that looks acceptable, paint the fairing with a filler/primer (rattle can works fine). Once primed, the painted surface will highlight any other defects or contours so that you couldn't see otherwise. If everything looks acceptable, then peel the tapes off and clean up any areas that need it.
Hope this helps.....
Bob Trumpfheller of Colorado sent
along a different idea for the fairing -- a removal windscreen fairing for sliders.
This method has the advantages (over the permanent method) of
easier finishing (on the bench) and easier wind screen replacement
if needed, it says on the
Web site.
James Kleen of Savannah has a somewhat different approach on
his RV-8. He's sent along a lot of pictures. Roll your mouse over
the image to see his captions.
Also sending along some pointers was Dave Smith of Libertyville,
Illinois. Dave is building an RV-7 and you can find his step-by-step
guide on
his blog.
Bill Schlatterer, down in Maumelle, Arkansas has provided a terrific
set of tips.
Do it neatly, it saves a lot of time later.
Buy rolls of the glass tape, it is much easier to use. Suggest
one roll of 2” and one 3”.
Buy one of the pizza cutters from ACS, I could not believe how
easy it cuts a perfectly straight edge. Always cut the larger
braided edge off the tape as it makes the transitions much smoother.
Use slow hardener in the epoxy, it gives you more time to work
the glass.
Use lots and lots of peel-ply. You don’t have any amine
blush and it is ready to go with no sanding although I usually
did sand again with 80 grit paper.
Use layup edges made from 10 to XX layers of cheap electricians
tape to get nice clean edges on the glass layups. This assumes
you want a 1/8 inch edge instead of sanding down to a flush finish.
I really like the 1/8 edge with black urethane windshield adhesive
to finish off the edge. For large areas such as the canopy edge,
I actually layed one long layer of tape on another, matching each
edge until I got about an 1/8” thickness.
That’s about 12 layers for 3 layers of 8oz glass. Not to
say sanded smooth doesn’t look a little slicker, but each
his own. (#3272) It takes about 12 layers of electrical tape to
make 3 layers thickness of 8 oz glass.
If you just need short strips for finishing the sides or canopy
edges,…. Do it simple. Take a cheap roll of electrical tape
and cut it one time through the center. Then peel off 1/8 thicknesses
and stick them together, then finish with one layer of the 3M
blue vinyl tape over the top to eliminate the joints.
When you want it right, use the 3M blue vinyl tape ($10 a
roll). It’s much stronger than electrical tape and doesn’t
break as easy when removing. This is the stuff to sand down to
if it’s your final layer.
Use a standard 3M sanding block for the curve sanding and
put the paper on the top and bottom. Now you can do the curve
or flat block sanding. (#3230) No need to make a special block.
These are about $6.
Buy one of these handy 3” random orbital DA sanders.
They make doing the windshield curve a piece of cake. This one
is by Chicago Pneumatic. (#3320)
I used black pigment from ACS in the epoxy so that the parts
that showed on the inside would look very finished. Notice in
this picture that the blue tape is the glass line and the black
is actually the glass with black pigment in the epoxy. It looks
like it was just painted on from the inside. I did that anywhere
you could see glass from the inside. They also have a white pigment
for the final coats.
After you glue your canopy closed,… don’t panic.
First get a straight edge razor blade and slip it under the edge
of the canopy strip. Slide with your hand or use a block of wood
to push it along the edge. If you used mold release wax and are
a little lucky, a good tug later will open the canopy. BE SURE
you have something at the back of the canopy that you can grab
strongly to pull on.
Note the temporary ADEL pull handle-
top rear. I had to put a screwdriver through it and really tug
to get it open. Recommend putting some Boelube on the locking
pins as well so they slide out of the plastic retainer blocks.
Here's Bill's pictures:
Walt Ray - Minnesota has helped build a Lancair Legacy and he's building an RV-6A. So he has had more than his share of glass work. " I try to
mix only enough resin to do the task and not waste material," he says. "Wash
the bond area with acetone before sanding and after curing prior
to another bid.Do not use spot putty to fill minor defects prior
to finish painting.Use dacron bleeder ply to control excess
resin. Use of electrical tape to mask area from resin works
fine. I use drywall sanding grids for sanding cured glass as
it works better than sandpaper. Permagrit tools are a great
timesaver for large tasks."
Says Walt:
For small jobs a quality plastic bag works fine for release
film/masking.Be sure to coat the area with resin before mixing
in thickening agents to fill an area.It might take several applications
to complete a task to your satisfaction which is why you will
always find thetime to do it over if you rush the job the first
time.
When I was shaping my seven layers of fiberglass on the canopy fairing (I followed the Van's instructions), I split a 4" PBC pipe in half to make the initial radius. Down the line, however, I found the 3M sanding sponges to be helpful because you can shape them to the radius.
In Jacksonville, Florida, Torello Tacchi, an RV-10 builder
has some experience with fiberglass, a good thing since there's
a fair amount of glass work on a "10."
Nearly all of my fiberglass work is performed using West Epoxy.
I made a mold for an overhead console using the cabin to make
a mold. The mold was made from cardboard and shaped with drywall
joint cement, and finished to a smooth surface. To prevent the
joint cement from permanently sticking to the cabin, I used
brown packing tape. Just about nothing sticks to it, accept
another layer of the same tape.
The male mold was sealed and waxed using floor polishing wax. Floor
polishing wax leaves a fairly heavy finish, and makes for easy
removal of the female molds. In addition, it's easily cleaned
off. A female mold was made using West Epoxy with slow hardener.
Polyester resin would have been cheaper, but from past experience,
it would work it's way through to the joint cement, and prevent
it from setting up.
Once the mold set is was removed and left with copy of an overhead
console female mold. I finished any imperfections using Bondo,
and waxed the female mold to produce an overhead console. Two
layers of glass were used to keep things light. To add strength,
West 404 filler was added to the epoxy mix. Used slow setting
so as to maintain flexibility. Once set it was removed. Provisions
for fastening covers and epoxied in before final assembly onto
the cabin.
While I found fiberglass messier than I would have liked, Laura Hoover, an RV-7A builder in Virginia, says "I actually sort of like doing fiberglass because it requires patience, finesse and unlike aluminum most mistakes are fixable. I attended Sam James workshop at OSH, bought his video and took his advice and used Awl-Fair instead of Bondo as a filler. My husband taught me also but I found I had to develop my own techniques by trial and error just like I did with the rest of my building skills. The reward came Oct. 21 when, after six years, our plane leaped into the air and flew perfectly. Our faces hurt from the RV grins!"
One of the problems I've noticed when perusing the Internet for particular advice on fiberglassing, is there aren't that many sites with in-progress building photos. It's a pretty messy business to risk a good camera.
But Cash Copeland of Oakland, who's built an RV-6, has sent along these images of his work when he glassed in his nav lights.
One last point: Don't get rid of your fiberglass tools when your plane is done. Dan Hopper, an RV-7A driver in Walton, Indiana, flies out of a short, rough grass strip and says every now and then, he needs to repair damage to the wheel fairings. Recently, he needed a way to clamp a layup to keep it tight against the inside of the fairing:
I looked around for something to use, and came up with this trick. Fill a zip-lock type freezer bag with sand or equivalent. I used kitty-litter because that's what was handy! It was heavy enough to do the job, and the epoxy didn't stick to the bag. It did a great job of compressing the wet layup which makes the repair stronger and lighter because you can use a minimum of epoxy. I'm sure this sandbag trick could be used for many other fiberglass jobs.
Eventually, you'll work your way to the cowl. RV-10 builder Deems Davis has extensive documentation on his Web site with ideas for this area, at least for "10" builders.
An album contains several pictures of a modification he made to his lower cowl. He also fabricated his own center console to match a fiberglass instrument panel he purchased from Aerotronics. Here's the beginning of an album that describes the steps.
Clearly, you'll want to practice a lot before trying this at home.
I hope you've found this article a little bit helpful. Clearly there's a lot to learn in handling fiberglassing, but it can be done and after a few layups, you'll feel more confident.
I'll be keeping a list of resources here for the archives. If you have a favorite online resource for fiberglass information, please send it along.
