Trax540

My Feedback: (1)

Sooo im making my first scratch 8" radial Fiberglass Cowl for a Sopwith. I turned a wooden plug for it on the lathe, and put about 5 or 6 generous coats of Carnauba wax on it.

Laid my cloth and built it up until i was happy with the thickness, mind you this is the female mold il be using to actually make the cowl itself.

Came time to seperate the two, No problem drilled a small hole in the cutout area and blew 100psi into the plug and presto it seperated from the wooden plug and i had a great female mold now to make my part.

Sealed the small hole i made ,
Now this time i put about 8 coats of Carnauba wax inside the mold. laid my glass inside for the cowl, and let it cure again overnight.

When it came time to seperate , the damn new Fiberglass COMPLETLEY melted into the female mold.

I let it cure for 24 hours so i know the original resin was not still tacky. AND i put almost 10 coats of wax on it.

I cannot figure out for the life of me why this has happend.

Btw im using Sig Polyester resin.

Any ideas why? Did i do something wrong, i followed the exact steps as i did on the plug im very very confused.

bigtim

My Feedback: (13)

not too sure of the exact cause,not being there when you layed up the molded part, but I would guess the polyester resin melted the wax and absorbed it into the mixture, resulting in the bonding of the 2 layers, it doesnt take much to get polyester resin to melt and stick well together.

there are 3 major types, laminating,sanding,and gloss,
with the laminating resin there is a tackyness to it, the reason for this is that there is a low wax content in the resin,and is primarally used for wetting the cloth,and building up thickness, and it sticks well to its self, its nearly impossable to sand because of the gummy mature of the material.

for sanding resin, wax is used as a surfacer and helps the resin harden so that it doesn't gum up, making sanding and buffing easyer, it also will harden the laminating resin fully so that there is no gumming up when sanding through the sanding resin.
sanding resin can be used for laying up parts and molds but needs to be liberally sanded to allow second coats to be applied after its had a chance to cure, before cure you can add several layers and it bonds well.

gloss resin is the hardest and can be polished to a glass like shine.

I would suggest making another female mold, and use PVA as a barrior between the layers of polyester resin,its easy to use just spray it with a airbrush on the subject, it's thin so several thin coats works well to build up the barrior, you can get it from places like Tap Plastics, a little bottle goes a long way when sprayed.

I did the same thing for my cowl I recently built, the parts separated easaly with a small amount of coaxing with a putty knife the separate the sections, 5 total.
cowl came out perfect, I was really surprised and pleased with the results, PVA rinses with warm water.

timrob

I recently was experimenting with mold making (I must say here that I am a total novice, but I learnt something that may help), and I made a 2 part mold. On one side of the plug, I used the carnauba wax on both halves (about 10 coats), and used PVA on one half, but forgot to spray the PVA on the other. The first half separated like a dream, very easy, the second I couldn't get to part at all. I even melted the foam plug, but the material I used to smoothen the plug was stuck into the fiberglass, and I couldn't get off. I learnt a very important lesson, PVA every time. Lucky I was just experimenting, getting to know the materials and what materials work best, so no harm done. The other thng was, I was using epoxy resin. I think the story is the same if you use Poly though.

Tim

KC36330

I've never used PVA myself and only use 3-4 coats of mold release wax (Finish Kare) and I've never had a problem with sticking to the plug or mold. i use both West and MGS epoxies.

timrob

I used West. I am still experimenting, and will try different methods, but in this case, the PVA worked where it didn't without. It may be the wax I am using, but I am sure it is the good stuff.

Tim

Trax540

My Feedback: (1)

Just seems very strange because i had no problems with the release from the wooden plug i made.

Yet it adhered completly into the female mold.


Ive started over now well see what happens with the new attempt.

Can Parafin wax be used for a R.A ? i could chuck the mold back onto the lathe and just use a hard candlestick to put many coats on the mold.

av8djc

My Feedback: (4)

I doubt you could get it smooth and will it release? Who knows. PVA PVA PVA The polyester resin has a large amount of styrene and that dissolves parafin. See below.

bigtim mentioned the wax additive to polyester resin. That additive is parafin dissolved in styrene. You only need a small amount to make "surfacing resin". I wopuld never use finishing resin on anything you might want to laminate later. It would be difficult to get the surface clean enough.

SCALECRAFT

My Feedback: (13)

Did your polyester resin exotherme (spelling?) and over heat, thereby melting into your surface coat?? Remember, its just a wax, PVA could have been your "insurance". Too much catalist maybe. ??

Mold releases that have never given us problems over the 25 years of playing with composite are Rexall Wax and PVA. I have model molds of composite wings, fuses, cowls, spinner, ect. that are like the day they were made.

I have used polyester, prefer epoxy.

Steve

Trax540

My Feedback: (1)

That was 1 of my thoughts, The chemical reaction does cause a good amount of heat and it is possible that it melted into my base through the wax.

Basicly im chalking it up to the RA, whether it wasnt enough or incorrect type. Its been a learning experience and i still have my hardwood plug to start fresh.
This time PVA

aeroanalysis

If you are serious about learning composites, use epoxy, not polyester. People use polyester resin because they can buy it at the local autobody shop or home improvement store. That's not a good reason. Order a kit of J Greer laminating epoxy and you will pay the same price per gallon as you are paying locally for your polyester resin. have fun.

trooper-rat

My Feedback: (4)

Have you tried using silicon moulds? A good mould release spray with a silicon mould is so forgiving and can be used 100s of times if you take care of the mould.

Just a suggestion.

Here is a link, not recommended per se, just a link to provide example:

www.reynoldsam.com/

Simple process: www.youtube.com/watch

Louis9624

Use epoxy. Polyester resinbreaks up wax and transfers it to the surface, where it forms a thin film. This airtight film, or barrier, helps the resin cure underneath it. It has nothing to do with temperature. If you must use polyester, there are other mold release agents that are not wax based. Tap Plasticshas one in a spray can, I forgot the name.....Pol-eas I think. It's expensive but works great.

tenacious101010

My Feedback: (97)

I have made a few molds and found that a cheap and effective mold release is a mixture of dishwashing liquid and water spread on a mold will work great, just let it air dry and make sure you have the complete surface coated. Maybe about a 50/50 mix. When you pull the part off, you just need to rinse the soap away. Not sure how this compares to the professional mold releases, but it worked for me.
Good luck with your project, Denny

NCIS

I use Evercoat Mold Release. I've never had an issue!

Barry

sidgates

My Feedback: (2)

On one of the small molds I have made I accidently left my heat lamp very close to one side of the mold after doing my lay up. The heat lamp apparently melted the wax on the lamp side and the part was very difficult to separate from the mold where the lamp was. The mold was repairable.

Now after doing a lay up I let the part cure at room temp for a couple of hours then I apply heat to speed up the curing process. My current project is the F-94C. You can see my mold construction at:
http://www.gates-sid.com

Sid
Denver, CO.

SCALECRAFT

My Feedback: (13)

Hi Sid. i saw your site.

Nice work. I didn't see any alignment key ways molded in on your parting board. How do you get your mold 1/2's aligned perfectly.

Steve

Roguedog

Hey Trax,

I'm sure that this is covered in this forum as I beleive I read it here. PVAis not just a mold release it seasons or helps cure the polyester mold as well. I read how lots of people never needed PVA and there waxing technique work just fine. Seems polyester has several chains of molecules that have not completely cured after harding. They're just looking for some new resin to bound too. I suspect that could be from incorrectly using the hardener, e.g. too much or to many drops. Those that have had no problems may have meticulously measured the harder and therefor had better results. I myself have over used the polyester hardener to speed up the curing process only to chemically burn the polyester resin with a exothremic reaction, the resin actually turned yellow and in one instance the leftover in the mixing bowl started smoking than cracked and shattered.

Same can happen with epoxy left in the mixing container although when spread out epoxy dosn't seem to exhibit the heat problemsthat polyester resin has. Too much hardener may very well have caused the wax to melt, although polyester tends to heat up anyway. A thinnly apppliedgelcoat either sprayed on or brushed on and allowed to cure might keep the wax from melting as well.

Use 3 or more coats of PVAon top of you wax and you may have better results.

Bryan