Making a Fiberglass fuse (or parts)....

[Arbo]

Ok, I have seen many skilled people here demonstrate their work, and I get the idea, I just want any tips that are out there prior to getting started.

As I understand the process:

1. Make mold.... (will leave this as one large step I have down).
2. Make parting board for mold, put mold in it and seal gaps with clay. (what type of clay?)
3. wax that whole half (mold, parting board).. do you have to treat a wood parting board so the wax doesn't soak in?
4. Coat with release agent... PVA is what I have read, I'm sure I can find it....
5. Put down 1'st layer of cloth, make it a light cloth for a smooth finish... and good resin (heard west systems many times over)
6. Now use heavyer cloth then matt or sand or something to get some substance to the mold so it won't distort. let this half set.
7. flip over and remove parting board, but leave mold in plug. Coat all this with wax and pva and repeat.

Is this the basic idea? I'm almost done with a mold for something I want to make, but will build a quick mold of something just to try my hand at it all first.

Paul

[shaneyee]

There is an alternative called the Lost Foam method. It uses a foam male mold ....

1. Carve and sand blue/pink foam to required shape.
2. Wrap with tape ( anything smooth and non stick )
3. Wax.
4. Cover with Half the fiberglass/Epoxy to be used.
5. After it cures, sand off bumps and flashing.
6. Cover with remainder of fiberglass/epoxy.
7. Fill and sand smooth
8. Pour acetone to dissolve the foam. Pull out the tape.
9. Spray paint to desired colour.

Great for One offs.

[Haldor]

Paul, you wax and buff the plug before adding the parting board. Then you put on release was on the parts you put epoxy on as you go.

Thats the basic idea.

[Arbo]

Yeah, I've heard of the lost foam thing, but I'm not interested in a one-off...

Haldor, so you don't need to wax the parting board prior to coating it with release agent?

Paul

[Ollie]

See:
http://www.scrollsander.com/Soaring-Nosecone.htm
http://www.favonius.com/soaring/index.htm
https://www.cstsales.com/How_to_Articles/fiberg0.htm

Unless you are intending to make more than two or three fuselages, the lost foam method is less expensive in material and labor.

[Gary Warner]

MY comments: (these are MY rules that I follow - not everyone will agree)

"1. Make mold.... "

It's a "plug"…

"2. Make parting board for mold, put mold in it and seal gaps with clay. (what type of clay?)"

Use modeling clay from hobby or craft store - oil based works well. Keep the clay under control and work slowly. A good accurate cut in the parting board will go a long way here. Keep the use of the clay to an absolute minimum. Any clay on the plug's prepared surface will show if not cleaned up completely. While you are making the parting board, make a "bolting (or clamping) board" for both sides of the mold out of thick plywood (1/2" at least - I use 3/4"). This is what you will run the clamping bolts through to hold the mold halves together in the lay-up process, assuming you make one piece parts like I do.

"3. wax that whole half (mold, parting board).. do you have to treat a wood parting board so the wax doesn't soak in?"

Wax the board and plug before placing plug in parting board. I use pre-laminated shelf boards. They have a slick sealed surface - no prep needed. Also, I've bought some epoxy painted particle board for a parting board, but I haven't used it yet - it has a very smooth surface. (I think it's marketed for large Grease Boards - 4x8 feet sheet for under $20) {edit: Reality check - it might have been about $40 - but it's 4x8 feet!}

"4. Coat with release agent... PVA is what I have read, I'm sure I can find it.... "

Though some will use this in the mold making process, I never put it on the plugs. This advice came from Jerry Slate (he has about 100 molds he's made in his shop). PVA comes into play during the part lay-up in a finished mold. Use a real mold parting wax if possible - West sells some. A spray called Free Kote can also be used, but I found is can leave “wet” marks in the plug (like a clean car’s finish after a sprinkle of watter).

"5. Put down 1'st layer of cloth, make it a light cloth for a smooth finish... and good resin (heard west systems many times over)"

Actually, this is a bit tricky. Mix West Systems epoxy very slowly. Add a tooling hardener if desired (for high use production molds - West or CST sells it but the part # fails me right now). Also, consider using a dark epoxy dye (black, red, blue from CST) as bubbles in the parts lay-up process will be much easier to see than with the natural light color of the mold. Bubbles are going to be the hardest part of this mold making process. Any bubble that lays on the surface of the plug is going to either leave a very thin layer of epoxy before the air gap, or you can end up with an air gap bubble without a thin cover. Either way, they are no good. What I've done is to take a mayonnaise jar and solder a nipple on the top that connects to my vacuum pump. Place the mix (still in the cup) into the jar, close the lid and pull a hard vacuum for a minute or so. All the bubbles expand and rise to the top. Once removed from the jar, skim off the bubbles on the top of the mix. Now the mix is ready for use. The entire plug needs to get a coat of the epoxy mix before the glass is added. Pour out (don't brush it on) a small bead of mix along the joint between the plug and parting plate, making sure that no bubbles are trapped under the epoxy. If you see that a bubble was trapped, stop and clear the bubble with a wooden tool or such. Then, pour the mix over the top of the plug. Let it run down the sides in a clean sheet of fluid, again keeping a careful watch for bubbles. Only use a brush to spread the epoxy when needed and be sure to stay behind the leading edge of the epoxy flow. Once the whole plug is covered, let it stand until the very first signs of kicking off. Then you can start to add glass. First a light coat. Then work up to full 6-12 oz. glass. I've been known to use glass matt (hardware store - boat/car repair section) that can add bulk very quickly. Be careful about the heat that large amounts of epoxy can generate. The last coat can be of any size, but I prefer a medium glass with a smooth surface (strings of wet glass turn into painful glass splinters when cured).
Now add and epoxy a bolting plate over your work and epoxy it well in place. Let lay-up stand for 24-48 hours.

7. flip over and remove parting board, but leave mold in plug. Coat all this with wax and pva and repeat.

Yes, except for one important thing. Before staring the process, use a cone shaped dremwel grinding stone and cut in small and shallow divots around the outer flat parting surface you just made. They should be about every 6 inches or so. What they do is create a locking effect between the two mold halves. The bolts will not be accurate enough to insure correct alignment between the halves. These divots will have perfect matching counterparts when the second side is lay'ed-up. Be sure to wax the divots well. Don't forget the bolting plate on the second side too. When the two sides are finished, drill bolt wholes about every 3 to 6 inches apart (1/4" drill bit works well) depending on the size of your mold. Don't drill into the divots you made. Marking the bolt plate with "safe" drill points will help, when making the divots. Once finished, a large knife will separate the two halves.

Doing the lay-up is a whole other thread.

[BMatthews]

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Excellent post Gary. Thank you for sharing these tips. The bits on the resin pour and wait to kickoff are new to me and are worth their weight in gold I'm sure.

For the glass going on over the kicking resin I assume you use a fresh mix of resin at that point? I also like the coloring being added to see airbubbles easier. Do you suggest adding some colorant to the resin used to lay up the mold coth? I can see you wouldn't want that on the first skin pour but for the cloth backup I can see that a dark mold would make it much easier to see airbubbles in the layup.

[Gary Warner]

Originally posted by BMatthews
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Excellent post Gary. Thank you for sharing these tips. The bits on the resin pour and wait to kickoff are new to me and are worth their weight in gold I'm sure.

For the glass going on over the kicking resin I assume you use a fresh mix of resin at that point? I also like the coloring being added to see airbubbles easier. Do you suggest adding some colorant to the resin used to lay up the mold coth? I can see you wouldn't want that on the first skin pour but for the cloth backup I can see that a dark mold would make it much easier to see airbubbles in the layup.

Thanks for the kind words. With this information you can do a mold that is equivalent to someone with several under their belt. Though there is no substitute for experiance in this sep-by-step intensive process.

The glass is there only to reinforce the mold structure, not to provide a finished surface. Defiantly, get a "gel coat" on first. As for waiting for it to kick off, keep the time table close. Start the glass building as soon as the glass won't float (I guess "sink" is a better way of saying this) down to the plug. If you wait too long, West epoxies develop a "wax" like surface and further epoxy layers won't be as strong. See West documents for details.

The color dye should only be used in the gel coat. It doesn’t even need to be on the parting surface - just where you will be laying up your parts. You will want clear, normal epoxy for the layers of reinforcing glass. Many pots of epoxy are going to be used in the process. Only the gel coat and the first pour over the parting plate needs to have mixing bubbles removed. Small (very small) bubbles in the glass lay-ups won't effect the mold. Though, large bubbles should be removed and the glass needs to be fully wetted out.

As I think you said, you won't be able to see air pockets in the mold lay-up if they were colored. The down side to using color in the gel coat is seeing bubbles that may be laying on the plug. It's not that hard to see trapped bubbles as they occur if you carefully watch the gel coat as it's being poured on. Also, the gel coat does not need to be opaque. Translucent will give a good effect for seeing bubbles in parts lay-ups. It makes a world of difference in laying up parts. If you have a mold that was already made "clear", it can be helpful to spray paint the outside of the finished mold with black to get that darker effect. It's best in the gel coat.

[davidfee]

What I've done is to take a mayonnaise jar and solder a nipple on the top that connects to my vacuum pump. Place the mix (still in the cup) into the jar, close the lid and pull a hard vacuum for a minute or so.

This is the single best tip I've seen in years. Don't know why I didn't think of it myself! Nobody has a bell jar laying around... but this is dead easy! THANK YOU!!

-David

[BMatthews]

Gary, thanks again for "Volume 2".... :D

Another hint for anyone that also does their own auto work. You can buy a cheap (relatively) little hand operated vacumn pump called a Mity-Vac. It's normally used for brake system bleeding but it also will pull a mean vacumn that would work great in conjunction with the Mason jar vacumn pot idea. They come in two styles, a basic plastic version and the Pro metal one. Canadian prices are $50 for the first and $90 for the Pro. US will be considerably cheaper. These pumps work super and will pull a surprisingly high vacumn quite quickly. They also come with a guage on the pump so you can see what you're doing and if there's any leaks. I think some folks have used these for vac bagging as well but if there's a leak at all you'll bust your arm keeping the vacumn up.

Hope this adds something...

[ArnoldC]

{edit: Oops! I see Arnold C was the last one logged in on this computer - I've got to get him to logg off before going home :D }

BMathews,

Good idea about the hand pump. Some modelers are not willing to say "any price goes" like me.

BTW, the reason for the jar instead of a container that you can't see through is that depending on how big the bubbles are and how full the mixing cup is, they can over flow the mixing cup when expanded. Seeing this over flow can allow you to adjust the vacuum to avoid a mess in the jar.

Also, I've never had a jar implode, but it's fair to say that safety dawning’s should be used.

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Davidfee,

Glad to share. I can't say I thought of it though. It was shared with me by a flying friend that was in the tool/die business before he retired. He didn't descride the exact process, but he said that they would put glues under a vacuum to get rid of the bubbles. The jar idea was mine and a bit of logic said that the bubbles would just raise to the top of the mix. I tried it and it worked.

Gary Warner
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