Composite boat-building materials & techniques

[Nordic cat]

Air entrapment during mixing is an issue, so choosing a low viscosity helps bring this down, as well as proper mixing procedures. Proffesionals often use inline mixers to avoid air entrapment.

So the conclusion is, less than 90% vacuum while infusing, then drop it to below 50% once it starts setting and getting hotter.

The panel study used chopped strand mat in the laminate, I think that this is the reason that some of the hand layups had relatively good values, as the whole laminate gets thicker. Otherwise it doesn't seem logical - but I'm not a laminate expert. Maybe someone can explain this oddity?

Regards

Alan

[cat man do]

Chopped strand mat

Come on guys, its 2008, does anyone use it anymore?

Dave

[BigCat]

"Come on guys, its 2008, does anyone use it anymore?"

Not me-but the suppliers seem to use it for testing. That puzzled me, too. Actually, I can see why you would do that for the panel test, because you use mat in hand layups, and to compare hand layups with infused layups you need to keep everything else the same-if you have 2 independent variables, you don't know what caused the results. (Comparing infused panels with hand layups was one of their goals.)

According to the engineer for my project, my panels would have the same strength in hand layup or infused layup, because the thicker panel in the hand layup compensates almost exactly for the higher properties of the infused panel that has less resin in it.

I noticed that AOC used mat and roving in their resin test, which puzzled me. Maybe the test was part of a larger series in which they wanted to compare hand layup, polyester, etc.

[BigCat]

Earlier this year, VT announced a new composite vessel design called the Fast Response Boat (FRB). With a top speed exceeding 50 knots/57.5 mph, the FRB is a high-speed armed patrol vessel for coastal defense, with diesel/waterjet propulsion. The new 48m/156-ft long, shallow draft ship will be made with a glass fiber/vinyl ester infused hull designed for a light hull weight and very high speeds. Kapadia says that VT considered carbon fiber for the FRB hull. Resin-infused carbon/epoxy and carbon/epoxy prepreg were found to save only 3 percent and 15 percent, respectively, in terms of weight, with a large cost penalty. "Some carbon will likely be used to provide localized stiffness," says Kapadia.
(From: CompositesWorld.com - High-Performance Composites - Fighting Ships Augment Combat Readiness With Advanced Composites - September 2003
)

Speaking of Mirabella V, the largest single masted sailing vessel ever built (244' long,)

Stitched multiaxial E-glass material supplied by Saint-Gobain BTI (Andover, Hants, U.K.) was reinforced with several plies of aramid and wet out with Reichhold (Research Triangle Park, N.C., U.S.A.) vinyl ester resin to form the hull skins. Airex 50-mm/2-inch thick closed-cell foam from Alcan Airex (Sins, Switzerland) was too thick to thermoform, so VT created tongue-in-groove foam planks that were fitted together to form the core, explains Holloway. To resist the high longitudinal bending forces of the very long hull, the upper deck has carbon/vinyl ester skins over a foam core, says High Modulus' Julian Smith. The deck is built up at rigging attachment points and reinforced with additional unidirectional carbon fiber to carry stress around openings. All internal decks, tanks and bulkheads were vacuum-infused as flat glass/vinyl ester, foam-cored sandwich panels, then hand cut to shape and installed.

(From: CompositesWorld.com - Composites Technology - Largest composite sailing yacht launched in U.K. - February 2004
)

[catty]

Originally Posted by cat man do

Chopped strand mat

Come on guys, its 2008, does anyone use it anymore?

Dave

Certainly usefully against the Gelcoat when infusing as contour foam print through is a real problem.

[BigCat]

Originally Posted by catty

Certainly usefully against the Gelcoat when infusing as contour foam print through is a real problem.

I was listening to a composites engineer today online at the composites seminar put online by Professional Boatbuilder Magazine-he was asked if there was a lightweight solution to print through. He couldn't think of any. I think the stuff used to prevent print through is called 'veil.'

[knottybuoyz]

Surfacing Veil or Optimat. I think there's a few other trade names for it.

[Robertcateran]

I reckon I can live with print through rather than the extra weight of chop strand. Under water, the anti-foul smooths it out, and on the decks, it helps with grip. On the side , it can be a pretty pattern.
Robert

[Robertcateran]

Originally Posted by Nordic cat

That was a "no-answer". You asked a very specific question, and he replied with some general statements.

I suggest you ask him to specify vacuum levels at different temperatures.

How the pressure in the wetted out part rises to atmospheric pressure, while the whole part is under vacuum, is difficult for me to comprehend. Pressure is force per unit area, how that changes with the atmospheric pressure exerting force on the outside must be one of the new wonders of science

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Alan

There is also the cohesive properties of the resin, glass matrix
Robert

[cat man do]

Very rarely have I ever seen print through of glass on boat that was built without gelcoat or choppies. (epoxy comp)

I have seen evidence of it in dark paint areas, but it is not advisable to use dark colours anyway.

I also would rather a thin screed of bog, some highbuild and paint than the large associated weight of choppies and gelcoat.

Dave

[BigCat]

Originally Posted by Robertcateran

There is also the cohesive properties of the resin, glass matrix
Robert

Since no one talks about the resin breaking free of the fibers, but rather about the elasticity of the resin, I think we can safely assume that the resin adheres sufficiently well to the glass or other fabric that the issue doesn't arise--assuming that that is what you mean by 'cohesive' properties. Your idiosyncratic term 'cohesive' is not clear. Do you mean tensile strength? It's in the published specifications, as is elasticity.

Call me a wild and crazy guy, but I'm guessing that if the Swedish navy thinks that an infused VE resin / e-glass laminate is 97% as good as an infused epoxy laminate, it really is.

[Evan]

I built vacuum bagged panels for the bridgedeck cabin on my catamaran. Triaxial fabric over a 3/4" corecell core. I tried going without surfacing veil, but couldn't get a smooth finish. The surface veil is about 1/4 oz mat, and does suck up resin, but it provides a smooth surface against the mold table. The resin rich surface also provides a barrier against pinholes in the triaxial fabric weave.

[catty]

Originally Posted by BigCat

I was listening to a composites engineer today online at the composites seminar put online by Professional Boatbuilder Magazine-he was asked if there was a lightweight solution to print through. He couldn't think of any. I think the stuff used to prevent print through is called 'veil.'

Dead right there Big Cat. We started with Veil and ended with hand laid up 600gsm CSM against the gel over a production run of 20 odd hulls. It certainly didn't get rid of it but made the print through less obvious. By the way the resin used was vinyl-ester.

[BigCat]

"glass fiber/vinyl ester infused hull designed for a light hull weight and very high speeds. Kapadia says that VT considered carbon fiber for the FRB hull. Resin-infused carbon/epoxy and carbon/epoxy prepreg were found to save only 3 percent and 15 percent, respectively, in terms of weight, with a large cost penalty."

Can this be true? It's from Composites World, so it's not the usual clueless reporter writing who doesn't really understand the story-

[fastcat435]

Originally Posted by Nordic cat

Air entrapment during mixing is an issue, so choosing a low viscosity helps bring this down, as well as proper mixing procedures. Proffesionals often use inline mixers to avoid air entrapment.

So the conclusion is, less than 90% vacuum while infusing, then drop it to below 50% once it starts setting and getting hotter.

The panel study used chopped strand mat in the laminate, I think that this is the reason that some of the hand layups had relatively good values, as the whole laminate gets thicker. Otherwise it doesn't seem logical - but I'm not a laminate expert. Maybe someone can explain this oddity?

Regards

Alan

We put the to be infused batch under vacuum before infusing to get the air out and it starts to boil shortly when all the air comes up. Makes a big difference .
I guess we ahve our own technique
we keep the laminate under 98% vacuum for 24 hours prior to infusion and this compacts the laminate, we infuse with 98% and one all is infused and the resin is coming our we will drop the vacuum in steps of 5 % to 75 % , when ready we connect all points to the vacuum source , also the infusion pipes to make the vacuum level the same all over .

Greetings

Gideon

P.s. alan keeping the laminate under vaccum for 24 hours saves us 150 kilo of resin over infusing immediately after putting full vacuum on
we have tried both