Tuesday, September 15, 2020

Cutting and Shaping

Below are a few pictures from progress on Nina's wing board. 

Profile shaped, outline marked: 


Table wire cutter setup:


Rough outline cut:


After cutting the outline with the table wire cutter, a few gaps became visible where the original foam blocks had indentations:


I filled the gaps with PU foam, which seemed to worked nicely.

After the fine trim of the outline with hand tools, I marked the rail lines, and then added a layer of 6 oz glass and 1/4 inch divinycell to the top. Since this is a wing board, a full sandwich construction which is typical for windsurf boards seemed like overkill. The board will not constantly slam into waves, so reenforcing the bottom does not seem necessary. However, a typical surf board construction, which uses just a couple of layers of fiber glass on top, would probably not have lasted long. Surfers stand on their boards only a few minutes each session, while Nina usually stands on her wing boards for at least a couple of hours per session. Add full-body pumps to get going to that, and the top would quickly delaminate. Therefore, I added a sandwich only to the top. The thickness of the hard PVC foam is twice of what's usually used in windsurf boards; thicker sandwiches are stronger. Instead of using vacuum, I just used a bunch of boards and weights to glue the sandwich foam on:


The weights seemed to work well enough:

Shaping the rails was the next step. The lines where the foam blocks were glued together were a bit harder than the foam, which made for some uneven sanding, so the shape is not quite perfect - but not too bad for the second board I ever built. Here's a view from the front:

A bottom view:

Between the step tail, rails, and plenty of nose rocker, the board almost looks more like a kayak than like a surf board.

In front, Nina wanted a concave bottom, which makes for smoother touchdowns and may also help getting the board out of the water. I first had to make a little tool to sand the concave:

Here's a closeup of the concave in front:
The next step will be to put the two US boxes for the track mount in. I prepared them today by encasing them in divinycell foam:


Putting the boxes in should be interesting. I've put tracks into 3 boards so far, but they were all existing windsurf boards. Routing the foam will be much easier than cutting through the sandwich, but require being more careful. I plan to put the boxes in so the tops are flush with the top of the foam, and then add one layer of glass to reenforce the track area. But the bottom will still be weaker than in the windsurf boards, so I'll add a couple of PU foam plugs below each of the boxes that connects them to the sandwich on top. 



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