Fiberglass Dinghy - Fiberglassing


I decided to use ‘vacuum bagging’ technique  for fiberglassing over the foam.  This would give a tight fit and accurately conform to the complex shapes of the hull and interior.  The vacuum bagging process would also yield a lighter weight boat with good ‘strength-to-weight’ characteristics. 

My plan was to spray the fiberglass resin and then immediately vacuum bag the boat.  The hull exterior and boat interior would be ‘glassed’ in 2 separate operations, then the gunnel would be glassed to complete the hull.

I arranged the fiberglass and tested the bagging process.  Everything seemed to be OK, so I tried doing the interior of the boat first.

The first attempt at vacuum bagging did not come out so good.  So, I needed to do some rework on the interior and re-engineering on my fiberglassing process.

One of the problems was that I was not able to spray the fiberglass resin fast enough.  So, I built a spray gun that would spray a gallon of resin in about 3-4 minutes (photo lower right).  It seemed to do the trick and I could spray the 2 +/- gallons of resin needed for each side of the hull in about 8-10 minutes.  I also cooled the resin before use, which gave a longer working time before it started to set up.

The hull exterior proved to be an easier shape to vacuum bag, and I had re-engineered things so that the vacuum operation worked out much better.  Here are some photos of the exterior after the glassing operation.

Here is the gunnel being glassed (photo - right), which completes the ‘rough’ hull.  For small areas, such as the gunnel, I used plastic drop cloth material and taped it tight to conform to the desired shape.  The vacuum was not really needed for these small areas.  As I gained experience, I found that I could roll the fiberglass through the vacuum bag, which resulted in excellent wetting of the fiberglass mat.

At this point the rough hull was pretty much done.  It was time to move onto sanding and finish work of the hull.

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