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Old    Jeff Walker (surfdad)      Join Date: Sep 2004       01-25-2010, 7:43 PM Reply   
e.wood, while miserable to work with, has some amazing properties in reflex, which helps "pop". Back in the day, there was speculation that the original Sunova boards had pre-fabbed skins. Not only to reduce manufacturing times, but also, it allowed higher pressures in laminating the fiberglass, but also higher heat to "cook" the resin - pressure and heat that would crush and melt the EPS core.

That's my experiement with this test section.

The "parts" involved:

Two pieces of 4 oz eglass

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e.balsa skin - two pieces to simulate panels

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e.redwood backer to simulate a flat surface and allow pressure without deformation.

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Mylar sheet, waxed to allow release - in hopes that the external surface will appear polished out of the bag.

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Breather and release.

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Old    Jeff Walker (surfdad)      Join Date: Sep 2004       01-25-2010, 7:52 PM Reply   
The process.

I wet out the two pieces of eglass.

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I missed one picture, but I laid one piece of the eglass down on the mylar and then on top of that the two pieces of e.balsa. I've applied some extra resin to the e.balsa in hopes that it would flow THROUGH the e.wood.

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Next I laid up the remaining piece of eglass. This will mimic the construction of the e.balsa compsand - glass/wood/glass.

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Then the perf ply. This will represent the inside layer and will leave an imprint in case I decide to actually glue the skin down to the EPS core.

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Old    Jeff Walker (surfdad)      Join Date: Sep 2004       01-25-2010, 7:55 PM Reply   
Vacuum pulled and heat applied :-)

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Old    Jeff Walker (surfdad)      Join Date: Sep 2004       01-26-2010, 5:14 AM Reply   
Mylar side is glossy, although I did get one dspot where the weave shows. This evening I will cut the test panel in two to see penetration.

One thing I forgot to mention above is that I "assembled" the panel to allow the epoxy to flow with gravity down through the e.wood.

Second picture - epoxy without any eglass in the matrix is not stiff like it's hyped. Epoxy is a medium soft plastic.

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Old    Jeff Walker (surfdad)      Join Date: Sep 2004       02-04-2010, 8:16 PM Reply   
I didn't get the penetration that I wanted, so I made a few changes after talking to some composite experts. One was the grade of the e.balsa. I got the cheaper B grade e.balsa that is more porous and also has a more motled grain.

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Old    Show (bigshow)      Join Date: Feb 2005       02-04-2010, 8:18 PM Reply   
Can you thin your resin?
Old    Jeff Walker (surfdad)      Join Date: Sep 2004       02-04-2010, 8:19 PM Reply   
The next change is I went with a slow cure hardener. Typically epoxy will have fast and slow hardeners and some a medium. The grading refers to the length of the pot life and length of time before cure...as the name implies, slow takes longer to cure. That extra time will allow the epoxy to soak deeper into the e.balsa.

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Old    Jeff Walker (surfdad)      Join Date: Sep 2004       02-04-2010, 8:23 PM Reply   
Two other changes, but I was sworn to secrecy on one, the second is I heated the e.balsa before applying the resin, so that as the e.balsa cooled, it would assist in drawing the resin in.

I did my resin work directly on the e.balsa and 2 oz eglass.

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Old    Jeff Walker (surfdad)      Join Date: Sep 2004       02-04-2010, 8:27 PM Reply   
Hey show, I tried thinning it like a penetrating epoxy. Anything more than 20% "thinning agent" caused the epoxt cure time to go from hours to DAYS. Impractical with my bagging arrangement. Less than 20% thinning agent helped with penetration, as you theorize, but severely reduced the strength of the resin...it felt compromised to me. This method, I HOPE, works best :-)
Old    Show (bigshow)      Join Date: Feb 2005       02-04-2010, 8:32 PM Reply   
Too bad there isn't a good way to infuse the resin through the wood. You know put the resin on one side of the wood and the vacuum on the other side.
Old    Jeff Walker (surfdad)      Join Date: Sep 2004       02-04-2010, 8:35 PM Reply   
I did heat the resin to affect the viscosity, but that isn't a change from the prior test. I laid up a section of peel ply directly over the wet 2 oz, this will give a surface to glue on. After that, some paper towels to act as bleeder - with the pressure, some of the resin will seep through the nylon peel ply. On top of that I place "bed topper" foam to act as a breather so that the vacuum is spread evenly.

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Old    Jeff Walker (surfdad)      Join Date: Sep 2004       02-04-2010, 8:38 PM Reply   
Then the whole thing, including the rocker bed slides into the bag. The finished skin will have the inside eglass attached, but not the external AND will have the bottom rocker shape, but not the concave.

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Old    Jeff Walker (surfdad)      Join Date: Sep 2004       02-04-2010, 8:43 PM Reply   
Infusion is pretty easy by itself, but I don't have an adequately sized pump for infusing, and it's not in the budget for now. You're right, that would do the trick.
Old    Show (bigshow)      Join Date: Feb 2005       02-05-2010, 7:18 PM Reply   
So how about applying the resin to the bottom side of the wood. Lay up the wet side against the foam core and then vacuum bag. Then pull the vacuum to draw the resin through the wood.
Old    Jeff Walker (surfdad)      Join Date: Sep 2004       02-05-2010, 7:43 PM Reply   
I may not understand what you're saying, so please correct me if I am wrong. One of the issues I have with this sort of construction is the the core is 1# EPS. It has the rigidity of FRESH sponge cake. :-) I can only pull to about 10 inches of vacuum, beyond that and the deformation of the EPS is SPECTACULAR! :-) Drawing through the stupid e.wood seems to require about 28 inches.

I believe that what you suggest would effectively crush the eps.

Maybe your process could be used used, just without the EPS requirement. As below:

1) Wet the opposite side
2) Lay that onto a waxed plywood, with some peel ply in between or maybe mylar so that there was no resin loss other than into the stupid.wood.
3) peel ply on the dry side with bleeder/breather
4) Affix the port so that is on the dry side and pull a vacuum to as much as the pump can muster.

I think that process achieves your suggestion.
Old    Show (bigshow)      Join Date: Feb 2005       02-05-2010, 7:55 PM Reply   
The only thing I would change is use Wonderful, Beautiful Wood.
Old    Jeff Walker (surfdad)      Join Date: Sep 2004       02-05-2010, 7:58 PM Reply   
Since such a substance doesn't exist, I will use the stupid.wood, which is readily available.

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