Fibre Glass Repair

[Esser]

Ok, I need to move the intake location on my cowl. I have no experience with fibre glass what so ever and was wondering if anyone could point me to a starter video and what supplies I would need for th8s type of repair. If it goes well I may make a plenum for the engine and if that also goes well I may even try fibre glass wing root cuffs....

I understand the theory of it, wet out the cloth and let cure, but there seems to be a lot of choice for materials.

[AirFox]

I sent you an email Josh. Hope it helps.

Scott

[jmodguy]

youtube is your friend!
There are several suppliers that have how to videos on youtube. Not a difficult process but there are some things that are good to know before you begin.

[David47]

youtube is your friend!
There are several suppliers that have how to videos on youtube. Not a difficult process but there are some things that are good to know before you begin.

That’s how I did my first fibreglass attempt. YouTube is my Encyclopedia, but with “moving pictures”....

[HighWing]

Josh,
I wanted to send a few tips I picked up after many years of working on lots of relatively small projects. Keep in mind that what I mention I use is only an example of what I have found that works well for me. I am sure others have techniques and materials that work equally well for them.

First - I have mostly used rather small quantities of epoxy resin in my typical projects. For mixing, I almost exclusively use the 2 Oz. portion cups you see near the catsup dispenser in fast food restaurants. I buy them at Sam’s Club. I also use a stainless steel “cement” spatula similar to the ones a dentist will use - http://www.ottofrei.com/Spatula-Norustain . The resin I typically use has 4:1 ration resin to hardener ratio and is what is referred to as a super hard resin vs. the more pliable resins used in structural components and adhesives. I find it is easier to sand when micro-balloons are added for surface finishing. There are hand pumps available that can be screwed to the top of the containers for ease of dispensing. https://www.tapplastics.com/product/...s/epoxy_resins . For portioning, I use an Ounce scale accurate to .001 Oz. with a 20 Oz. capacity. Placing a cup on the scale then powering it up will show 0.000 in the window and I will add a small amount of hardener. Multiplying that by 5 will give the final weight needed for a correct mix.

Fabrics come in many weights and physical characteristics. The heavier weights will typically be used for structural components. For the typical airplane projects, I most often use what is called a Modified Twill. The weave is such that it will more easily adapt to compound curves. It can also be cut on a bias similar to the bias cut finish tape used in fabric covering for adapting to sharper curves. Two or three layers of the lighter weight fabric will adapt more easily to a curved surface than a single layer of a heavier fabric. https://www.tapplastics.com/product/...rglass_fabrics

Micro-balloons can be mixed with the resin to create a “Bondo” like filler that is very easy to sand. It may take several applications to get the perfect surface we will want on the outer surfaces of our airplanes.

For cutting cured fibarglass, I use a Dremel with a diamond disk tool. It cuts cured fiberglass very easily and can be followed up with a drum sander for final edge finishing. To prep the edge of an existing fiberglass structure that is to be modified, a die grinder with a Flap Wheel works well to scarf the edge of the existing structure for a strong lap joint with the new lay-up.

The typical clear plastic packaging tape can be used as a separator. Example, when I made my wing root to windshield cuffs, I covered all surfaces that would be exposed to the curing fiberglass with the tape. I laid the glass on the surfaces similar to the technique described below but using a needle like wire to pick up the lay-up for shaping and after curing the lay-up can be easily removed for trim and finishing. If you are concerned with the packing tape adhering too strongly to a painted surface, a preliminary layer of thin masking tape will help there. The use of car wax as a separator works as well, but it should be applied in five or six applications - cured layers to ensure easy separation. A spray separator is also available for application over the wax for a surer separation without damage to the underlying surface. PVA Mold Release can be sprayed or applied over the wax by using a very soft brush.

One example: A project when working on my friends Lancair IV. He wanted to permanently install an oxygen system. The oxygen tank and regulators were to be installed below the shelf behind the rear seats. He found the tank about an inch too tall and needed an adjustment to the height of the shelf. What we did is cut a hole in the shelf that would accommodate the top of the tank. The edges of the hole were scarfed with the flapper wheel to create an edge from zero thickness on the bottom of the shelf at the cut out opening tapering to full thickness at the top over a distance of about half an inch. We then took two sheets of vinyl cut several inches larger than the hole. On the vinyl we placed a layer of fiberglass cloth about two inches wider on all sides than the outer measurement of the scarfed area on the shelf. Resin was added to saturate the fiberglass and another layer was then laid on the first. More resin was added where needed on the new layer and then a third layer was added. On top of those layers we laid another sheet of the vinyl sheet. A plastic squeegee was then used to remove all extra resin. We then used a pair of scissors to cut the lay-ups to the approximate size of the cut hole with about an inch and a half overlap. Resin was brushed onto the scarf; the bottom layer of vinyl was removed and the lay-up was positioned over the hole and the top layer of vinyl removed. Using a gloved finger, the glass lay-up was pressed downward to create the joint in the scarfed area, then the lay-up was moved upward in the middle to create the bubble that would create the space needed to accommodate the oxygen system. By careful tapping top and bottom, a fully attached edge and a smooth lifted surface was created requiring minimal finishing after curing. After curing, the flapper wheel was used to remove all glass extending beyond the scarfed area, then with a micro-balloon mix the surface was prepared for finishing.
I really enjoy fiberglass work as it has many possibilities and is one technique that is very easy to repair when the outcome proves short of expectations. It just takes time. On the Lancair it was our routine to do the prep work during the bulk of the day, then when it came close to quitting time, we would do our layups to cure overnight.

[Guy Buchanan]

Try this as well.

[Mcgaero]

Hey Josh, you have some good advice here and I can't add much...
I use West systems epoxy and find it works well, you can buy slow, medium and fast hardener which I find handy. Slow hardener is great to give you some more working time for larger Jobs.
West systems is used a lot in the marine industry too so its usually easy enough to buy.

[Esser]

Thanks for all the replies everyone. Epsiecially Lowell for his detailed post. I’m going to try to pick up some supplies today and make it hopefully this week.

At least where this repair is going it will never be seen

[jtpitkin06]

Not a video but a complete manual for free from West System

https://www.westsystem.com/instruction-manuals/