[Video] Large Scale Mold Making - Part I

Step 4 Glue

Each section uses a 2X4" cutout for indexing and alignment. This ensures that the plug goes together straight and true (sometimes with a little adjustment).

Use a foam safe glue. Since last year, 3M changed the label on their "77" spray adhesive. The only change was the word "foam" -- after a test sample (comparing last year's can and this year's), we determined it to be safe in smaller dosages. 3M 90 will melt this foam on contact. As always, test first when working with your materials (especially new ones).

Our friend from Lockheed recommended 3M 74. Not available at the local hardware stores, but I'll remember that for next year and special order it.

Before spraying, wax your alignment "dowels." This will help the sections to slide down easily and prevent the glue from sticking together. Re-wax every few sections as necessary.

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Application
Spray an even fog over the edges of both faces to be mated and then spray a little bit in the center. It is key to get a good stick on the outside edge so that when it is sanded, you get a good gradient without separation. The key is (according to our composites master) to find the line between too little and enough. Remember that too much (of this glue formula) spells melted foam.

Once an even coat of adhesive is sprayed down, align your sections and stick down. We let the glue set for a few minutes with bricks on top to ensure a good bond.

When aligning, pick an edge to follow. In our case, we wanted the leading edge of the 2X4 to line up the whole way. So before sticking down, we lined up all three of our alignment 2X4's on their leading edges - then pressed down. Once we figured this out, we got perfect results.

Comments

[TimmyMiller]

aye, she be seaworthy alright. : D :P