[planecrazy]

I tried making some fibreglass fairings yesterday. Needless to say I'm not real pleased with my work.

Thought I'd ask the experts what I'm doing wrong.

I started with the tail wheel bay cover. I laid Suran Wrap over the mold (I know but I thought I'd try) carbon fibre matting, using 30 minute epoxy thinned with IPA, i then laid about 3 layers of .63 oz fibre glass, one layer laying the fibre glass cross ways.
I checked the part late last night, after letting it sit all day. And I've seen card board more stiff. I must be doing something wrong or not enough. Any help is appreciated.
Also, how do you get the fibre glass to lay flat on a curve???? That one is driving me buggy!!!
Chris

[Kevin McGrath]

A couple of questions......fibreglass or carbon fibre? Fibreglass mat or cloth? .63oz ie less than 1 oz cloth the stuff used for finishing balsa? describe your mold a little better too pls.......

[planecrazy]

Ok, well first I laid 1 layer of this really thin layer of carbon fibre matt (he guy at Fibre Glass Factory said to lay it for stiffness) next was 3 layers of .63 oz fibre glass cloth.

My "mold" was a balsa block carved to the shape and the carbon fibre\fibre glass combo was laid over top of it.

I suspect that my answer lies in your post Kevin, I'm building this thing with finishing fibre glass.

Chris

[Guest]

First of all the plug or pattern must be finished to perfection no scratches or dents as perfect as you can get it. Second the surface must be sealed and the smoother the final finish the better the mold. You must not have a negitive draft or taper on the pattern or you will never get that or the finished piece out. A small positive draft is best. Then when you are ready you need to fix it to a surface such as a plate of glass then make sure the joint is sealed and a small radius between the glass and the pattern exists. At no time let any cracks or indentations at this seam remain or you will never get the pattern out of the mold.

The rest of this is the instructions for using the mold as well. You need a parting wax I use a product called Partall. It is a hard past wax and some have used a house hold or automotive hard past wax with good results. You must apply "3" coats minimum to the pattern or the mold. You must wait a bit between coats and you must polish the waxed surface each time befor the next layer of wax. After the third coat I apply a release agent usually a spray can you can get it to release without its just a bit more work and take your time. I find that 6 oz cloth works best for the finished product and for creating the mold I will use 2 layers of this 6 oz cloth then 2 layers of Automotive cloth I get mine from Canadian Tire.

Cut all the cloth you are going to need plus into 2 inch squares works best for me. The cloth will not sit or form well into any hard corners or curves so you will need a filler for the epoxy resin. Mico balloons will work or silica fibers as well. Look inside the mold or the outside of the pattern note all the corners you think will give you a hard time. Mix up some epoxy and thicken it with enough filler so that it will almost hold a shape or peak when you lift the mixing stick out. Now work it into all the sharp coners and curves to make them smoother and less sharp. as you work you will see the epoxy smooth out. Now mix up your epoxy and start to place the first 2 inch square in the mold or on the pattern. Use a acid brush and work the resin into the cloth till its saturated. Overlap about 1/2 inch with the next 2 inch piece and keep going till the whole job is finished. If you are doing a mould let the glass and resin extend onto the flat plate glass far enough so you can trim a 1/2 lip around the whole thing. If a mould let the glass and resin extend out past the lip at least 1/2 inch you will trim it off later. 2 layers of 6 oz inside the mold to make the part and 2 or 3 on the pattern followed by 2 layers of automotive should do it.

Obviously by now you have realized that the working time needed with the epoxy is greater than most hobby epoxy's allow. I ONLY use the West System and the 206 hardener that will give up to 2 hours working time. Boat supply places are the most likely places to find it.

Dennis

[Guest]

Remember to trim the extra off the mold when the glass and resin are still green (not quite rigid) The extra should be dry to the touch and just soft enough to move slightly. Trim with a razor blade out against the wall of the mold and flush with the lip of the mold.

One trick to help release the part from the mold is to take an exacto knife or something and lightly pry away the edge of the part from the lip of the mold. Carefull not to much just the edge. Now use and air nozzel and blow air down between the part and the mold you will see it releasing. Just work the air nozzel back and forth around the edge of the mold. Watch your face I have had them pop right out and hit me.

Dennis

[Guest]

Now with all that being said its obvious that for one small mold and part your looking at quite an expence. Many have made one of parts by carving and shaping plain old white styrofoam. Cut and sand to shape then fill and smooth the foam with hobby filler or the light weight spackle from Home Depot. you do not have to get to fussy as this is the inside of your part. Now lay up the fiberglass and Epoxy (only as it does not attack foam) with 2 layers. This time do not fill and smooth out the detail try and maintain that detail by cutting the fiberglass to form into those corners and such. After all has hardened sand lightly and wipe down with the solvent that you will be using in you high build primer. Spray the primer on and sand repeat till all the imperfections are filled. This is lighter than epoxy filler and easier to sand. If you have access to a good spray gun try using feather fill as it is the lightest yet. By now if any of the foam has been exposed the solvents have slowly been eating it away. You can pick the rest out or use a little of the same solvent to disolve the foam away. Wash with dish soap and rinse and dry. Paint. One word of caution here this stuff is all flamable be very careful and don't do this in the house. One other thing is that Epoxy will gas for a time. This time will be greater the less accurate you are mixing the hardener and resin. This gassing will cause pin holes in your paint job if the epoxy is not cured enough. 2 ways to reduce the chances of it happening. Cure the epoxy with a little heat like a cardboard box over a hearing vent in the house for a few days. Heat lamp or even just a work light in a closed wooden box. Be carefull of the chance of fire if it gets to hot. I use a water born primer that acts as a barrier and you do not get any pin holes as it stops the gas from getting to the paint surface.

Dennis

[Kevin McGrath]

Who in their right mind would try to follow an act like this?

[Guest]

Sorry about cutting in like that it is just I know the frustration of trying to get decent results with that stuff. I started out much the same way as PLCZY and ended up with the system that I now use. I spent hours and hours and much money before I learned. There is no easy way to do it thats why they charge what they do for cowls and such. Sometimes its just easier to carve it out of balsa and harden it with some epoxy.

Dennis

[Kevin McGrath]

No sorry necessary.....what matters is getting a good answer thread started and yours is excellent.Making fibreglass parts from male or female molds is a strange art,which is much easier to show than trying to describe here but its a nice skill to develop if you do much building particularly from plans or scratch......

[planecrazy]

All this for 3 fairings.

I think I'll just carve some balsa.

Thanks for the info, I think I'll print it, just to keep it all on file the next time I loose my mind.

Chris