Custom CF Wood Hybrid 2.0

[lizzard]

edited.....

[littlesmith]

edited quote and reason for response

[littlesmith]

The big mold failed as some have read in the last posts, this is my last shot. This is 1.9 Kilo gelcoat in 1 mixing batch, so at least it won`t be seperate layers this time.
I`m not gonna heat cure this and not wait as long as the last time (which was recommended in the pamflet), as soon as this is slightly firm and still tacky, the fiberglass backing will go on.
I will put around 7 square meters of fiberglass on this, then some aluminium foil as a heat retention core, then close it up with more fiberglass, and some cement to make a curved back for the heating blanket to cure the actual bodys.
If the back of the mold has the shape of a bicycle helmet, the blanket can go over it without folding or hard angles that can potentially damage the heat spirals inside.

[littlesmith]

Applying fiberglass on the 2nd mold attempt, while the gelcoat is still tacky but semi cured.



The whole mold covered in 1 layer of fiberglass, bonding it to the tacky gelcoat. At this stage i waited untill the gelcoat was firm enough to handle the tapping of the brush without distorting shape.



This picture is mid process when i had to change gloves, so i had a picture opportunity that would not distract me.



This mold has 7 to 8 layers of fiberglass now, crossing eachother on every layer. The making of this mold went well. Now i will wait 3 days and then i will build some supports and give it a round back for the heating blanket.

[rogthefrog]

For those of us without CF knowledge, can you please explain why the mold is made of fiberglass and epoxy?

[littlesmith]

Originally Posted by rogthefrog

For those of us without CF knowledge, can you please explain why the mold is made of fiberglass and epoxy?

Hi.

The first thing to apply is a gelcoat, this will be the surface of the mold. Gelcoat comes in epoxy version and polyester version (i am using industrial epoxy tooling gelcoat that can become 120 degrees Celcius without distorting). Gelcoat is hard but not strong enough to be a mold by itsself. The fiberglass is applied on the back of the gelcoat and will become like a hard shell when the epoxy that has been impregnated into the fabric cures. When all goes well it will be 1 solid mass that can be released from the mastershape (plug). Epoxy has part A and part B, and when you mix them it will become very hard. You could make a mold from carbon fiber instead of fiberglass but that is 10x more expensive, it`s not really needed for a this mold. Epoxy without the fiberglass fabric would be hard but brittle.

[littlesmith]

Always precut the materials, you don`t want to be fumbling around while you are on the clock with mixed epoxy resin. Never let yourself be rushed and lose focus.





Aluminium heat retention core applied, it has epoxy between every layer.



Aluminium heat retention core applied, and sealed with more fiberglass and epoxy.

[littlesmith]

I didn`t like that i could push the new aluminium foil + epoxy + fiberglass stack down 2 millimeters with my finger, so im compressing the stack.

Mold with peelply (so the bag does not stick to the composite stack).



Putting a spiral hose :



Making my own bag by folding a vacuum foil sheet on itsself.



Put that sucker under vacuum.

[littlesmith]

To make it clear what im doing (i made this in paint, i`m not a graphic designer ) :

[littlesmith]

Compressed mold stack released from the vacuumbag and peelply removed, semi cured (it`s hard but it still needs 1 day to fully cure.



Carbon fiber woven round tube :



Cut the carbon fiber round tube



Determine where the round tube is most flush to know where to cut the other end.



Mark the exact posiotion of the tube crosshair style, but not writing in the glue area.



Marked around the tube anyway.



Make the top of the little tube round to recieve the carbon fiber round tube.



Snug like a glove in a glovebox (yes, i made that saying up, and i can live with that).



Heavy duty stuff.



Now we wait...

These carbon fiber round tubes are made so the neck to body angle can not move or bend during the release operation (the last mold broke in that location). It also increases general dimentional stability. The guitar shape will be seperated from the constructed negative mold in a few weeks, i have left space in the neck area for some cement mass so the heat can travel to it uninterrupted. The entine back will have a round shape like a bicysle helmet.

[rogthefrog]

Originally Posted by littlesmith

Hi.

The first thing to apply is a gelcoat, this will be the surface of the mold. Gelcoat comes in epoxy version and polyester version (i am using industrial epoxy tooling gelcoat that can become 120 degrees Celcius without distorting). Gelcoat is hard but not strong enough to be a mold by itsself. The fiberglass is applied on the back of the gelcoat and will become like a hard shell when the epoxy that has been impregnated into the fabric cures. When all goes well it will be 1 solid mass that can be released from the mastershape (plug). Epoxy has part A and part B, and when you mix them it will become very hard. You could make a mold from carbon fiber instead of fiberglass but that is 10x more expensive, it`s not really needed for a this mold. Epoxy without the fiberglass fabric would be hard but brittle.

Got it, thank you.

[littlesmith]

Reinforcing the joint. I don`t think it`s necessary, but i rather have overkill then under.... something.





Taping off an edge to stay clean. This area will get the last layer of fiberglass to cover the cement.





This is fase 1, it will get one more layer that will make the mold nice and round when this layer has dried.

[LouieAtienza]

Originally Posted by littlesmith

Reinforcing the joint. I don`t think it`s necessary, but i rather have overkill then under.... something.





Taping off an edge to stay clean. This area will get the last layer of fiberglass to cover the cement.





This is fase 1, it will get one more layer that will make the mold nice and round when this layer has dried.

Cool... do you take out the plug before adding these stiffening components?

[printer2]

Do you have to heat your composite lay up in your mold?

[littlesmith]

Originally Posted by printer2

Do you have to heat your composite lay up in your mold?

I bought an infusion epoxy, the planning was to use it with that big mold, but that one failed.

The product says 48 hours on room temperature then 15 hours at 70 degrees Celcius. It still becomes hard without heat curing but the mechanical properties get better when you follow the instructions.

First I`ll make 1 body without heating this new mold. If that is strong enough i might nog heat the mold at all with the other bodys. The main focus is getting 8 bodys out of this mold with consistent quality. The mold can`t distort or warp, which could happen in some cases.

I`m not sure if this heating blanket directly on a composite mold is a good idea. In an ideal world the mold would be an aluninium cnc routed block, then you can put the heating blanket on without any potential melting issues.

The epoxy used in the mold and geltcoat can both handle 120 degrees celcius without warping If you followed the instructions, which i didnt because this second mold didnt have heat on the gelcoat. So i have no idea how close my gelcoat layer is now to optimal and how close my properties are to optimal. This is all heavy science, way above my paygrade. I just mix the 2 components.

If the gelcoat and expoxy in the mold still have natural properties without the heat, then this new mold should not warp when its brought to 70 degrees celcius and back for 7 seperate bodys, i`m just worried about the blanket directly on the underside of the mold.

I can`t risk damaging this mold, so if the first body is nice, without heating up the mold, i might continue that.