Timing of steps before infusion

Mr Rxcomposites you said "I use a surfacing mat after gel coat. It serves two purpose, one because it has such a high resin content and two, it serves as a reinforcing layer for the gel coat. Next would be CSM300 then CSM 450 with VE resin to reduce or eliminate print through of succeeding WR. So far no problem with high quality gel coat used (LR approved). No osmosis, no blistering. First two layers of resin rich mat was enough as a barrier coat."

But our plan to use a barriercoat behind the gelcoat ( Atlac e-coat 65) was not to improve the water resistance (which also does) but to improve cosmetic appearance by reducing fibers printhorough, as indicated by DSM resins.

But it might not be necessary and become another thing to do, I have always been in doubt in regards to using it or not.

 

If it is not meant to be a barrier coat, then it is useless. VE is such a good barrier coat as the molecules are tighter and the resin is much more elastic plus it is much more chemical resistant.

ISO gel coat has only 2.5% elongation, hence the surfacing mat reinforcement. VE is 4-5%. It also has low shrink cure which makes it superior in reducing print through.

It is a compromise in design. The outer layer receives the highest stress and highest impact resistance. That means use of uni or wr fibers in the outermost layer with a high stretch resin. Because of cosmetic requirements, gel coat is used and a barrier coat of resin rich mat. In design, anything less than 300 grams/m2 is not counted as structural layer and serves only the cosmetic and water penetration requirements.

I guess you have to make some test to reduce manufacturing cost.

 

I'd be going white all over & spray the topsides in the ice blue in PU later

Jeff

 

So you think that as an avoider of printhorough a layer of 1 mm thick Atlac e-coat65, which is a sprayable material with no fibers in it will do nothing and would therefore be a useless step ??

( the price of it not being an issue since it is not a lot of material )

 

... using RRT-Roller resin

RX, Is that a Surfacing tissue/veil that you're using or like a 225gram split strand chop? Where I did my apprenticeship(quite a while back now... Using R/BRT-Roller/Brush Resin Transfer) both were pretty standard in any lay up. The tissue was a bit troublesome especially if put on shimmery side down.... I wonder that it's fallen out of popular use.... although I still buy & use it.... maybe I "old fashion fella"

Ondarvr, What are your thoughts on those .... is there "better/newer/convenient" materials? Especially for infusion?

Regards from Jeff.

 

My experiences so far with surface veil tissues (assuming is the same thing as a surfacing mat) is they are a pain to use, quite difficult to laminate smoothly and quite frankly, being so thin I very much doubt they can have any use as to avoiding printhorugh, IMHO they may do something in regards to creating a barrier against water permeation, but I can not see why they could any better than for example a 225 g/sqm which is also very resin rich and much thicker, being then a thicker barrier against moist and thicker to prevent printhorugh of fibers

 

Surfacing mat or veil is in the 30-50 gr/m2 whose primary purpose is a reinforcement layer for the gel coat, a tie coat if you like. It is difficult to layup but I believe in its function so it is always in my layup schedule.

The 225 gram variety is a light mat, neither structural nor a veil but is usually laid up as part of the reinforcing layer before infusion. You usually find this as the interfacing layer in the biax. It is noted as biax with mat. I have seen racing boats built this way. SM (veil) then a light mat, all hand layup before infusion. It is a trade off. They need the boat to be as light as possible and the boat is usually dry, pulled out of the water as soon as the race is over.

 

Good surface profile on infused parts can be tough, the higher fiber content exaggerates the fiber print. Barrier coats and veil (there are several types) all help to block print by moving the bulk of the fiber further from the mold surface. Barrier coats have become popular because they are easy and quick to apply in production, plus offer very good print blocking and water (blister) resistance. Blister resistance is also enhanced when the fibers are moved further from the part's surface. 40 years ago there were actually some much better surface veils, they almost dissolved in the resin and laid down easily with no wrinkles, I used it a great deal. I still have a small 6" wide roll from back then. It was discontinued due to the high cost of manufacturing it.

When customers ask about how to achieve "the best surface profile" on an infused part it's hard to answer because every customer has a different level of expectation. I always say to make several test panels in the exact way you plan to make the part, switching barrier coats, fabrics, laminate schedules, resins, catalysts, etc. to see exactly what the surface will look like with each combination and then choose the level of "the best" that fits your needs and budget.

You can normally get to 80% of where you want to be rather easily, the next 10% takes some work, the next 5% takes hard work, time and money, the final 5% can be very difficult and costly.