Hi all,

I'm having an issue with print though from my core materials while infusing.

The project is a race car body so weight is critical.

The first  section of the body was done released, painted with Duratec primer (no gel coat as to keep weight down) 2 layers 5.9oz 2x2 CF, 1/4" Baltek foam. This is slotted and perforated. Slot side down then another layer of 5.9 CF. Infused and got a great part, but the print though was not good. I've using the style of foam a bunch of times but never had that amount of print through.




So next part, used Soric.... even uglier. Had to toss that one away! This was my first attempt using Soric and while I did some test panels that came our great using 18oz CF, the part didn't share the same outcome.

Curious if anyone has used foam core just perf'd and not slotted and had success with the mold side layers wetting out ok?

Thanks for the comments

Cheers

Linz

I use perforated foam (6mm thick with holes drilled at about 50mm c/c) and have no problems with wetting out.

Hi, are you ambient curing or oven curing. Print through from the core will be much more evident if you demould too soon. The part can look fine when first pulled from the mould but a few days later the print through becomes visible, caused by the resin in the channels not being fully cured and shrinking slightly. The problem is even worse when using Soric. I add 50% onto my cure times when using a core. Even having said that with the lightweight cloth you are using I would still expect a degree of print through.

Warren

Carbon Copies Ltd

Hi... I'm just curing at room temp. Using Vinylester VE resin.

I was never confident of getting the inner layers of CF to wet out if I used a core without flow channels. But if the consensus is that with decent amount of holes....every inch or so, then I could make it work....???? hopefully??

Linz

> I'm just curing at room temp. Using Vinylester VE resin

There you have it. VE  has relatively high shrinkage (up to 10%), higher viscosity and limited pot life. VE contains lots of styrene, this limits the vacuum during infusion.
Use an infusion epoxy and you won't need the slotted core, you will have much more time for infusion and much reduced shrinkage.

Actually I wanted some shrinkage and the Composites shops close to me couldn't get infusion resin for 3 weeks!!! Ahhhh

I did use styrene Monomer to aid in the viscosity and cut back the catalysis to 1.7% by weight.

I had enough time to infuse. The first part I did use Vinyl Ester infusion resin with the same results in print through.

Linz

> Actually I wanted some shrinkage

????
Seems like you got what you asked for...

> I did use styrene Monomer to aid in the viscosity

Adding more styrene to the resin also increased the shrinkage considerably. The styrene content is the main reason polyester and VE resins shrink so much. Increasing styrene content makes the problem worse.

hmmm.. ok did not know that one. Dam!

They don't tell you that tidbit on the back of the can.... albeit I was using less than 5% Styrene as my resin was already pretty viscos.

I have recently switched from using Soric to using Amorim Corecork, with very satisfying results. The core is lighter, consumes less resin, and is equally as conformable as Soric. The best way I can describe it is as a direct replacement for Soric but one that is seemingly better in every way. So far I have not seen any sign of print-through on any of the parts I have made with it. 

Not quite sure why you would actually want shrinkage?
As this is racecar bodywork and you say weight is critical I would have waited the three weeks for the epoxy infusion resin. Result would be a stronger and lighter part with much less/zero print through.

I have done some tests in the past on the gelcoat verses paint argument. By the time you have have applied adhesion primer, base primer plus top coat there is negligible difference in weight over carefully applied pigmented gelcoat. In fact depending on who applies the paint parts can actually end up being heavier. Depending on the final colour wanted you can also just pigment the infusion resin.

Much depends on the number of layers of reinforcement, the size of the panel being infused and the thickness of the core as to the size and spacing of the resin transfer holes needed. It is also important to balance the number of reinforcement layers either side of the core, not only from a structural point of view but also from an infusion perspective. If you have more reinforcement on the mould side of the core the resin can infuse through the top reinforcement too quickly leaving the mould side reinforcement starved of resin.

Warren

Warren

Carbon Copies Ltd