Although System Three Silvertip epoxy resin was not really formulated for infusion. I was able to use a few tricks that produced nice results:
bagging the rudder ; notice the resin intake tube wrapping around the top leading edge.
The vacuum manifold was placed about 4 inches below the lower trailing edge of the rudder. This separation allows full vacuum pressure to be obtained while creating a "resin brake". (Once the resin makes it through all the glass and over all of the flow media, when it hits the double layer of peel ply, it stops flowing towards the spiral wrap vac manifold at that location)
Resin intake line: The green stuff is a flow media that is sort of like plastic bug screen but it has a raised cris cross texture that allows resin to flow edgewise through it. This allows the resin to flow more freely over the glass fabric.
the feed bucket
sophisticated flow valve
resin flow ( darker green area)
Here's the secret trick......to prevent exotherm, fill the feed bucket with small batches of mixed epoxy and pour waiting resin into a giant zip lock bag so that the surface area is maximized and heat from the exothermic chemical reaction can be dissipated quickly.
marking the flow
five minute interval marks allow me to get a feel for how long it will take to infuse completely. Notice the shorter and shorter flow progression every five minutes.
Resin brake beginning to work
Full infusion. I clamped a couple of flat pieces of wood along the trailing edge to insure that the glass overlap cures nice and flat.
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3 comments:
Allen: Looks really good. What weight did you end up with and did you use spray glue to lay dry laminates flat prior to bagging?
What was the temperature when you infused the rudder Allen?
Rick
I haven't weighed the rudder just yet but I think the strength to weight ratio is right where I want it to be. Since I'm going with the shear pin kick up rudder boxes, I should be able to ram full speed into a submerged boulder and be ok.
All of the prep work was done using light spraying of 3M-77. My understanding is that the trace amounts go into solution with the epoxy without concern. I created small test pieces using adhesives and without smashed them with a hammer and could not detect any differences in strengths of the two samples.
Ambient temp during the infusion process was around 70 F. maybe a little less. I pre heated my resin to around 85 just to lower the initial viscosity but it's a fine line to walk. As you can see from the time marks, it took more than half an hour to pull the resin all the way through and that's on the scary edge of the workable flow time even for "slow" resin. System Three Silvertip is NOT an ideal resin for infusion. It is non forgiving of less than optimum technique.
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