Thread: Fibreglass guard repair

MS, are you saying aluminium foil won't stick, or does it have to be waxed for 100% release.

I read somewhere that Mr Sheen is a good release agent, any comments?

Ken

Hi Ken,
Sorry your having problems. Bollie gave me some flat sheet fibre glass the other week when he was moving, would you like me to cut a bit and send it off to you?

Dave

I don't know about Mr Sheen, but I don't work in the industry. Though I'd think that anyone in the industry would be using the correct materials in the first place.
I can understand not wanting to spend too much money on a small repair like yours, particularly if you don't intend to do anymore.
Why not try Mr Sheen as an experiment? If you use some sheet metal or smooth melanine coated chip board and just try it out before you attack your repair.
Another thing that would also work would be to use some metal or board and roll out a thin layer of plasticine on it. Put the plasticine against your repair area (with the board still behind it) and lay up on that. You would just have to be gentle when rolling it out that you didn't roll a dent into the plasticine. Once the resin is cured the plasticine would peel away from the resin.
regards
bollie7

DJ, I wondered if flat sheet fibre glass was available, that might be the go.

How thick is the sheet you have? My guard is approx 3-4mm thick. I would need a piece approx 100mm sq.

If I had had any experience with fibre glassing, I wouldn't be asking so many questions, it's a whole need ball game for me.

Ken

Aluminium may stick, but it won't react or melt from the polyester resin and it's very easy to sand off (and you need to sand the surface of the resin anyway for a really good paint bond (or leave the aluminium there for that 'industrial' look!!). Much safer that having some plastic there that is ok for the first ten minutes but then gives in to the resin solvents.

Carnauba wax is a good release agent, but if you are going to be spray painting, keep the Mr Sheen in a safe place, like not buying it in the first place - silicone is a right pain to chase out of a 'to be painted' area.

DaveJ, you mentioned you have some fibreglass sheet. Can you get back to me with the average thickness?

I will send you my address via a PM.

When doing fibre glassing, I presume that a thick layer of the mix is applied first with a disposable brush, then allowed to partially dry before applying the glass mat. How long will the mixture take to partly set?

Ken

Watch this:

How to Repair Fiberglass - YouTube

Note about that video - you don't need the gelcoat if you are going to be painting (gelcoat provides a self-coloured finish).

You can also use marine epoxy to repair fiberglass instead of polyester resin but you need to check that the mat is compatible (sometimes the binder used for chopped strand mat prevents a good bond).

Fiberglass mat is sold by weight; you simply apply more layers till it's the thickness you need. The more the mat weighs, the stiffer and less conformable it is - so heavy mat is good for flattish areas, but it's real hard to get it to turn sharp corners.

The important points not covered in that video - wet the fiberglass out thoroughly with the resin when applying; fiberglass goes clear when wet with resin - however, you don't want too much resin (it's just a waste of resin as resin by itself has no real strength and is brittle), which is why they sell consolidating rollers. (hint - stipple it down well, especially corners, with the brush, but be wary of the resin starting to gell and the brush picking up mat!)

There are a number of different types and weights of fiberglass cloth - the most common is chopped strand mat (unidirectional fibers), but the woven cloth is stronger and drapes better than chopped strand mat. There's also a grade called surface tissue which is used under surfaces that will be gellcoated for a finer finish.

Fiberglass mat in small quantities via ebay is about $10 per square meter, or your local boat store will have some. Perhaps the worst place in the word to buy it from is hardware stores!

Has anyone here used a product called Kahglass? It's a polyester resin reinforced with fibre glass and retails for around $25 for a 500ml tin with hardener.

It is supposed to be less messy, and easier to use than fibre glass and resin.

Ken

Originally Posted by neksmerj

Has anyone here used a product called Kahglass? It's a polyester resin reinforced with fibre glass and retails for around $25 for a 500ml tin with hardener.

It is supposed to be less messy, and easier to use than fibre glass and resin.

Ken

I have used it. On cars strangely enough. I threw out a tin last year. It was rock solid. It is easy to use and hardly messy at all. Mix it on a bit of disposable plastic, it comes out of the tin like paste. A bit of scrap metal to dig it out. Squirt out a bit of hardener, mix and do the repair. The hardener sqeezes out like toothpaste out of a tube and you just sqeeze out the length required based on quantity of mix. Throw all the messy stuff in the bin. With fibreglass you need a brush to apply the resin. It is not easy to clean it. You can buy cheap brushes and chuck them but using disposable scrap is better and you don't get sticky fingers near as much. Kahglass would be my choice for your repair. It would not be as strong as normal fibreglass as this would have much more fibre laid right across the repair. I doubt you would need that much strength tho.

Dean

If it's an area that gets vibration and the occasional use (such as a belt guard) I'd reinforce it with a bit of aluminium mesh at the very least (car shops sell mesh that's supposed to be used to help bog holes). Personally, I'd do it with resin/mat so it's got the maximum chance of survival!

Mmmmm sand the whole outside back to bare resin, then drape some carbon fiber cloth ($20 per square meter) over it and resin that up for a real high tech look!!! A pimped out lathe!!!

I've cut back the damaged areas, and am ready for the big fix. What's seams tricky is that I have to glass around a bend that's also radiused.

I'm thinking maybe a mixture of Karglass to get around the corner radius, then fibre glass for the flat section.

Here's a pic so far. I've reworked my plaster or paris mould so I have something to lay the matting up against.

Ken

Ken
I think this little project is starting to blow out of proportion in complexity.
In spite of what I've said in my earlier posts, after looking at your latest picture I really think the quickest and easiest way to fix this would be to cut a bit of aluminium sheet to the correct radius as the missing bit but longer to fit inside the guard, with a couple of "tangs" that can be bent to 90 deg to fit inside the curved bit. Give the surface of the metal a good rough up with emery, then a good clean with acetone or thinners, and then epoxy it in place with a good quality epoxy (Araladite or similar) Once the glue has set properly fill the outside with car body filler, sand back and paint.
Job done.
I've very roughly drawn some lines on your latest picture to try and show what I mean.

I once repaired the gearbox case of an old Honda 90 bike, where the chain had come off and punched a hole into the case about the size of a average postage stamp, by glueing a bit of 2mm aluminium sheet over the hole on the inside of the case, with body filler only. When we sold the bike years later and after countless hours thrashing around the paddocks it still was not leaking oil.

regards
bollie7

Or -

1) Borrow a pair of the misses' pantyhose (if she asks, just tell her it's 'cause they are so comfortable!)
2) Cut 'em up and stretch 'em over the area to be repaired, securing with clamps or stout gaffer tape or by fitting over the part entirely (whatever works!). Just make sure they won't slip off!
3) Mix up a small batch of resin (like 50ml or so)
4) Paint the pantyhose over the repair area with the resin
5) Leave to cure
6) The next day, build up the pantyhose repair from the inside with fiberglass
7) Sand and putty to a paintable finish.

Brushes wash out quite well in acetone/paint thinner if you get them into the thinners before the resin starts to gell.

I used to do this to make water shields for speakers in car doors or make custom speaker enclosures. And if anyone wants to know how it was done, you fixed it with a pair of pantyhose!!

Example - How to fiberglass (subwoofer enclosure) - YouTube (the interesting stuff starts at about 2:50)

Finally, I got around to repairing my fibre glass belt guard. I'm doing this in several steps.

After clamping the plaster of paris mould in place, I mixed and applied a generous coat of Kahglass into the corner radius using a strip of stiff 3mm leather as a spatula. When that's dry, I'll lay up some strips of fibre glass matting.

6 minutes have passed, and the Kahglass has set already. The picture looks a mess and shows one of the spring clamps, and the white plaster mould. The brown area is the Kahglass.

The picture is looking into the inside of the guard. It's a bit hard to fathom out.

When time permits, I'll lay up the glass in strips, followed by body filler where required, undercoat then paint. Should be as good as new, hopefully.

Edit. I left out a couple of steps. The plaster mould was given a coat of aquadhere, followed by a coat of the good old fashioned Joseph Liddy clear wax.

I'm hoping this will ensure the plaster of paris mold will just lift off cleanly.

Edit2. Oops, just removed the spring clamps expecting the plaster mold to fall off, wrong, it's well and truly stuck. What do I do now? If I force it off, it's likely to crack the Kahglass, this stuff dries brittle.

Ken