Optically clear gel coat

[entx]

thread327-131655

Hello All,

I am looking for the same results without having to apply a clear varnish later.

My tentative process is to use Hawk Ind. Hi-gloss clear P/N 1904-045 as the first step (I am waiting to hear back from the sales rep on whether or not a tie coat is needed to transition to epoxy resins). These parts will be using Pro-Set 117LV resin and CF using RAVTM with a post cure per resin manf. I am not too concerned with UV resistance as most of the time they will eventually get top coated by my customers with either opaque paint or a urethane clear coat that has UV inhibitors in it...

I would like to have a nice glass smooth finish(assuming the mold is perfect of course) that is also as optically clear as possible. Yes I know I am looking for that all elusive holy grail, but I have to keep looking...

Does anybody have any suggestions? Any help would be great...

 

[entx]

Sorry typo...VARTM not RAVTM

 

[canada911]

I am also really interested to this question...

Is there another way to do for clear coating then spraying it on the part AFTER the demolding?
Does someone know of a Successfull method of doing it directly inside the mold like we are doing with gel coat?

 

[Compositepro]

While what you seek is theoretically possible, practical considerations lead almost always to the use of a clear coat that is post applied. The effort to maintain a mold surface to a perfect gloss is not easy. Making VARTM parts with no surface pits (trapped bubbles) is not easy. These pits are filled by a post applied coating but will be visible under an in-mold coating. Fabric print though is caused by resin shinkage during cure and will be very visible in a glossy gel coat. A post applied coating covers print-through because the gloss surface is created by surface tension of the liquid coating.

There are so many things that can cause surface imperfections. With a gelcoat type of application you must start production with a perfect mold surface and be very careful at every step to not damage it. With post applied coatings you fix everything at the end. And the ultimate quality of the gloss surface that is possible with a post applied coating is greater than is possible with a gel coat.
So a lot depends on what you hope to achieve.

 

[entx]

Now that I have done some samples to determine what has worked and what will not work..coming up with an optically clear composite part is not too difficult...Like "compositepro" said the mold surface has to be perfect...which to me was the key... Because what surface your mold is, will be replicated into every part thereafter... So first and foremost make your plug absolutely perfect...use good quality gel coats that can obtain a high gloss for the surface of the finished mold. Once you have pulled the mold and allowed it to cure...you can then color sand it with 1200 and finer grit paper and buff it to a high gloss....

Using clear gel coat does provide a clear coat as long as you don't spray it too thick...a 20-30mil coat will produce as clear of a coating as needed. Yes you do get print through on the finished part..which is fine because at the end of the day you will always spray a urethane clear coat on top for UV protection. The clear gel coat acts as a primer for the urethane and allows you to sand the gel coat smooth without exposing the fibers...so all in all it provides a very good clear part...

Air bubbles are not present if you take your time and make sure the bagging material is completely sealed...this takes practice on working with the material...if it's sealed completely you will have a very high quality part...if not..it will be riddled with bubbles...