Monday, September 27, 2010

Beefing Up the Roof Rack Extender

From the last post, which was just the feasibility phase, it was apparent that the extender had to be beefed up. When extended, it just did not have the strength and stiffness to hold the weight of the Sunfish. I liked the PVC as the material, but it just needed to be stiffer.
So the solution was to double up the PVC and rivet a metal bar inside the PVC pipe. This made the arrangement much stiffer.
These pictures are out of order, but you can get the concept.

Above is the second PVC clamped to the first. I tried to use the PVC glue but could not get the clamping contact in place before the solvent gave out. I think maybe a construction adhesive or just caulk would work. The [urple primer and orange glue did not work.
Another view of the failed clamping process.

This is a good shot of the concept. Double walled PVC with bar rivetted inside. In order to get the outer PVC to take that shape it needs to be heated. I used a paint stripping heat gun. A torch would also work but may result in burn or too much concentrated heat.

Close-up of the rivets that go through both layers of PVC and into the bar. These will be covered by tape or padding to prevent them from scratching the hull.

Above is the original showing the bar in place and the sliced section to be used to double up the PVC.

This is the heat gun I used. Good even controlled heating. As it heated, I pushed down on the PVC to open it up and applied clamps to hold it in place while it cooled. PVC is fairly bendable when heated but it will scorch. This is one of those well ventilated space activities.

Here is the PVC sliced open on the table saw. The next one I do will not be sliced in half but just at 3/4. This way, I will be able to get some clamping action from the "C" shape of the pipe which might elimnate the need for rivets through the two layers. The "C" shape pluse construction adhesive may work very well for this. The bar will also be necessary for the stiffness.

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