Creative Advice Needed

[saddlebum]

I seem to see by the posts that some are confused when the word fiberglass enters the conversation so let me clarify. If I can. Also I will use the term Plastex but plasti-fix is the same stuff. Aircraft Spruce carries it under the Name Plasti-fix.

 

 

1. Unless I have to, I do not repair from the outside to minimize disrupting the finish. However if I am repainting anyway then I gouge and fill from one side then once cured I gouge and fill from the other side.
   
2. I only use Plastex (although I am willing to try one of the homemade ABS concoctions next time around) But I do not use the resin's (polyester or epoxy). because A) I find they do not flex the same and B) as stated before the do not not fuse with the base material but simply stick to it so in time it does crack. Secondly fiberglass heats up as it cures and a thick layer could actually produce enough heat to distort the ABS. ( I actually burned my finger once when I touched a big chunk of curing fiberglass). Also the resins require spot putty to refinish the surface if used on the outside were plastex does not and you can sand it perfectly flush and smooth with the original surface, adding more and sanding as required to get a perfect surface. which is great if your repainting.
   
3. When I use fiberglass tape I use the open weave drywall tape, rather than the traditional fiber glass cloths primarily because of the open weave.
   
4. First I repair the crack with the plastex and when it is semi-cured I lay on a layer of tape then bury it in more Plastex maybe add another progressive layer or two for added strength all done on the inside.
   
5. to keep the Plastex from migrating to the outside of the crack I cover the crack with packing tape, rubbing it down to eliminate air bubbles. The tape also works well to fill holes by applying it to one side while apply the plastex form the other side. And folding a piece of tape over your finger makes a great none stick surface so you can use your finger to smooth out semi cured plastex.
   

Hope this Helps answer any confusion that may exist. BTW, I am intrigued with some of the home made ABS recipes posted here and will try them for comparison. I even looked at one of my old hand crank meat grinders wondering if it would work to grind up some cut up pieces of ABS. Will have to make sure not to accidentally try to make ABS Hamburgers.

[camos]

I even looked at one of my old hand crank meat grinders wondering if it would work to grind up some cut up pieces of ABS.

The meat grinders I have seen would not do anything with ABS. Although I've never seen one, I have heard of burr coffee grinders and think something like that would probably work.

 

I cut leftover ABS pipe or fittings into half inch chunks that will dissolve quick enough in the MEKS solution. When I cut the pipe in a vise using a handsaw it is done with a cloth spread to catch the cuttings. Otherwise I use the ancient tried and true manual grinding with a wood rasp to create finer pieces. These are used to quickly thicken a too runny mix.

 

This dissolving process is not in any way fast so when I use quickly, it is loosely meant. It takes a couple of days to dissolve the bigger ABS chunks but only a couple of hours to dissolve the small cuttings. Getting the right consistency is mostly a matter of timing. When the mix in the jar is thick enough to be scooped out in a blob without running off the cutoff table knife being used as a spatula, I let it dry for a few seconds until it loses its stickiness then roll it into a 1/2" ball with my fingers. The rolling essentially kneads it and gets the air out.

 

Before prepping the ABS mix, squirt some MEKS on the area to be repaired. This will soften the mating surfaces a bit then give it another squirt before pressing in the blob. MEKS is very volatile so the outside of the blob will be a bit dry but the inside is still quite wet. The extra squirt reactivates the outside surface of the blob so it sticks better.

 

Hairline cracks or tight fitting cracks can be successfully glued together by squirting a little MEKS into the crack and holding closing pressure on it for a few minutes until it sets.

 

None of this is very difficult, it is mostly just a matter of doing it and getting a feel for the timing. Setting is relatively fast depending on how much is being used. Curing can take a day or so to get a usable strength but full strength could take a week or a month depending on how thick the repair material is.

 

A last thought, when I refer to squirting, I have a small solvent applicator bottle with a 10 gauge needle that works great.