KaP2011

My Feedback: (17)

I remember reading an article years ago, I believe in RCM, about sheeting foam core wings with fiberglass. The difference with this method is that you lay the fiberglass out on a large peice of glass like a window pane. You then spread out the epoxy as you would when glassing a wing. When the epoxy is cured you peel it off the glass and you get a semi-flexible sheet that is very smooth on one side and very coarse on the other. You then sheet the core as you would if you were using balsa sheeting. I never tried it on a wing core but I did make a smaller peice about 12" X 12" and used it to strengthen balsa formers. I laminated a peice between two 1/16" balsa sheets and cut my formers from that. They came out very strong and light, worked really well.

Anyone use this technique to sheet a wing?

karolh

Never heard of that method before but it sounds like a great idea especially using it to strenghten formers.

vicman

My Feedback: (10)

It gets even lighter when you pull a vacuum on it.

KaP2011

My Feedback: (17)

I've never tried vacuum bagging. I've read several articles on it, it dosen't seem to be very hard or take much equipment. Some plastic sheeting, tape and a shop vac. I've always used balsa to sheet wings with titebond glue. I once sheeted a little combat wing with construction paper. I thought the fiberglass on glass method sounded pretty good, you get a nearly ready to paint surface. I've got some cores for a Bill EvansWiseguy Simitar that I think I'm going to try the method on.

vicman

My Feedback: (10)

Trying not to go off topic but it's a little more than a shop vac. I made my first pump from a refrigerator compressor.
Other than that you got the idea and it is indeed pretty simple once you get all the stuff together.

KaP2011

My Feedback: (17)

The reason I've never tried the vacuum method was because it didn't make sence useing a shop vac because the only way to hold the vacuum was to leave the shop vac running.

vicman

My Feedback: (10)

It won't give you quite enough suction even if you did.

aspeed

A friend of mine did the fiberglass over the glass surface and glued it onto ribs.  They came out 'fairly' good.  If you were to glue it onto a foam wing, PU type glue may be lighter than epoxy.  If you don't want to do the vacuum bag thing, a maybe 4" thick piece of foam rubber on the top and bottom of the wing witha piece of plywood over top to keep it even. It should hold it fairly evenly, with likely a bit of sloppiness at the LE and TE. A slightly better way may be to impregnate  the cloth with epoxy or whatever, and put a piece of waxed mylar, .010 to .020" thick on top and bottom and vacuum or sandwich  as I mentioned before.  I haven't tried these ways yet, I have too many planes in the shop to smash up first.

vicman

My Feedback: (10)

Usually with a foam core you have the shucks (or outside parts the wing was cut from), I use these to help in the clamp sandwich under vacuum. When I glass over the wood I use a clear film from Hobby Lobby similar to mylar (and cheaper) with wick material around the edges as a non-stick barrier between the shuck and glass layer. I get a super smooth surface.
I have also used this over solid sheet wings with carbon. It looks just like it came out of a mold.[8D]

invertmast

My Feedback: (23)

Yup,
like this:

speedracerntrixie

My Feedback: (29)

The easiest way to do this would be to wet out the fiberglass on a peice of waxed 5 mil mylar then place that on the core fiberglass to foam. Place the core with the glass and mylar back into the shucks and vacuum bag or weight down. Once cured you can peel the mylar away and have a very smooth surface.

rcmichael

My Feedback: (21)

You may want to take a look at the fliteglass website. They sell pre-made sheets of composite fiberglass in various sizes. I use it and it is a big timesaver, and saves weight. I cover balsa framed up or foam with it and I have had great success with it.

91zulu

My Feedback: (2)

Could you post the site link for the glass sheets

speedracerntrixie

My Feedback: (29)

Check with your local commercial door company. They are always doing strorefront door upgrades and usually toss the door glass. As per code it is 1/4" tempered and is ideal for layups.

vicman

My Feedback: (10)

Invert,
Like this too.
This was actually my first attempt with CF over balsa. Now I sandwich in kevlar for the hinge and have a seamless top surface. I use this method for making quickie v-tails.

KaP2011

My Feedback: (17)

I did a search for the fliteglass and couldn't find anything on it. Seems like I've heard of it before.

nonstoprc

My Feedback: (90)

It depends on the bag chosen.

I once applied the method with a 36" long bag that can be sealed (like the space bags). Over the duration of cure (about 1 hour), I ran re-connect the vac to the one-way valve twice to maintain the best vacuum. At the end, the skin glued to the core very well and the wing is absolutely strong.

The bag material has to be relatively thick as it will be pushed against the edge of the skins. Thin material will not survive the process. Some sanding on the edge to smooth it out is a good idea.

vertical grimmace

My Feedback: (1)

ACP composites sells everything you need for this. Cheap vacuum bag systems, resin, fiberglass sheet.Carbon mat as well. I love their bag system. It works very well.

KaP2011

My Feedback: (17)

Thanks for the tip about ACP Composites. Prices well within the budget of the average modeler. I'll be placing an order.

rcmichael

My Feedback: (21)

The website for fiberglass sheets is fliteskin.com. If it doesn't come up try the Warbirds Over the Rockies from 2012. It was a sponsor I believe and if you click on the fliteskin products logo it will get you to the website! By the way the Warbirds over the Rockies is a great event with some topgun quality warbirds.

sensei

Just to elaborate on this good method, sometimes the shucks and or wing core are in not so perfect condition so what I have done was this: I purchased enough .025" thick aluminum sheet from Aircraft Spruce & Specialty, I then placed the wing shuck on top of the aluminum sheet and traced the shape of the shuck to the aluminum sheet, next I carefully cut the sheet with snips making sure I did not snip all the way to the end of the snips thus causing wrinkles in the aluminum sheet. Note: this can also be cut with a large pair of sharp Wiss scissors or an inexpensive air cutter from Harbor Freight for those with an air compressor. The next thing I do is spray a very light coat of 3M 77 spray adhesive on the aluminum sheet and the mylar then place them together, I make these mylar covered caul plates for both the top and bottom sides on the wing core. Now I perform my layups on the caul plates place the bottom one in the shuck, place the wing core, place the top one and the top shuck, now I bag and vacuum. These caul plates act as mylar covered hard mold surfaces only in a reverse process and supported by the shucks on the backside, however because the aluminum sheet is only .025" thick the vacuum bag causes the sheet to conform to the wing airfoil without transferring all the imperfections of a not so perfect set of wing cores and shucks. Keep in mind that if you have minor holes or deep gouges in the core; then these should be filled with a thick resin and micro slurry as part of this layup process and bagging operation or these will show as voided areas.

Bob

rgburrill

fliteskin.com does come up.   It looks like a great way to do fiberglassing.

KaP2011

My Feedback: (17)

Fliteskin.com came up that time. It looks pretty much like the fiberglass sheet I was talking about in the beginning. I had not considered using it over open areas. I may try that on something in the future.

MTK

This technique builds a bit heavy for the desired stiffness. I did exactly this recently to a stab and was disappointed at the weight build up

The best technique for Lightness first, strength, stiffness and finish is still using good ol' contest grade balsa and finishing with silkspan or Esaki tissue and dope. It's old, tried and true technique that has withstood test of time

BUT if one doesn't much care for weight, then this is perfectly fine

billf

Here's a variation on this good approach. I have been fiberglassing autogyro blades for quite a while. Usually the cores of the blades are hot wire cut. The SG6042 airfoil seems to work well for autogyro use.
Take two mylar sheets (7-10 mil thick) that are slightly wider than the coord of the blades. Tape the sheets together along the long edges. Turn the sheets over, wax the surfaces.
Lay light fiberglas (3/4-2 oz cut on the bias) on the mylar. (bias cut fiberglas imparts excellent torsion resistence) Spread two part, slow cure (2 hour) epoxy on top of the fiberglas and squeegee (with a credit card for example) until it looks almost dry. Lay the foam blade core with the trailing edge of the foam at the junction of the two mylar sheets (right over the masking tape. Fold the mylar/fiberglass over the top of the blade (or wing) Rubber bands can be used to keep the sandwich together. Slip the sandwich into a polyethylene
silo chute liner. (These are sleeves that are extruded tubes about 16 inches in diameter and are used by farmers to throw silage down from the tops of the silos, can be purchased from farm supply stores.) Seal both ends with window putty, stick the vacuum tube into one end and pull the vac. The lower bed of the foam block used to wire cut the blade can be used underneath the sandwich to help conform the final part. By the way, it's a good idea to slip a flat hard board INTO the sleeve and under the sandwich. This gives a good flat surface when the vac is pulled. It turns out that only about 5 inches of vacuum is plenty (more can crush the foam).
After about 8 hours the assembly will be stiff enough to take out of the vacuum but overnight is better. The one drawback to this method is the leading edges are not usually completely enclosed in the fiberglas. Sanding will smooth the edges, but the very front parts are not covered. It is a good idea to have a hard wood or balsa leading edge built into the assembly before glassing the give a good surface to be sanded.
One disappointment: When the mylar is peeled off, the surface of the fiberglas, it looks beautifully smooth and shiny. BUT it is full of minute pinholes that need to be filled.
For some reason the epoxy does not fill completely through the weave of the fiberglass during the squeegeeing. I have not tried coating the mylar with the epoxy first and then
laying the fiberglas on top and squeegeeing.
One point in using slow curing epoxy: It gives a lot of time to 'mess' around with the assemby portion of the sandwich.

Hope this is clear.
Bill