Primo Longboards: The other half of our shop

My sons are into longboard skateboarding and have launched a business.

They are carbon fiber molded decks.  We fabricate them alongside our boat projects.
Here are some photos:

Sup Plug: Step #6

Gel-coat overcoat.
After extensive sanding of the first layer of gel-coat, the plug is ready for the next layer.
With each layer, the number of issues (divots, surface blemishes etc.) are fewer.
It the following photos you can see areas that we added fairing on top of the first layer of gel-coat.
Once today's coat is added, the problems will be down to a handful.
I expect we will have one more pass.

Today's coat is a grey to contrast with the blue under-layer.

SUP Plug: Step #5 Gel-Coat

The SUP's plug is getting close to the uniform surface we are after.  But from experience we know there are problems that are hard to detect.  One thing that really helps is to spray on a layer of gel-coat.

By giving the surface a uniform color and material, the eye has a much better chance of spotting problems.

With this first layer of gel-coat, we will add a tint color.  Pure white is just too hard to see differences in.    

We also added a wax sanding aid to the gel-coat.  This allows the surface to cure hard so it is easier to sand.

After this layer hardens, we will continue sanding.  What else.

Here is white gel-coat in spay cup and a concentrated
blue tint color we add.

Here are the cup gun parts.

Mixed, assembled and ready to spray.

SUP Plug: Step #4: rounding the rail edge

To achieve a uniform rail edge we do a few different operations.   The initial plywood bend has to be a uniform bend.  Once this is accomplished the next step is to use a router with a radius bit to cut the sharp edge off the ply.  I used a 1/2 inch radius with a bering guide.
As the fairing progresses on the side wall, we roll a palm sander over this edge.  The ply is harder than the fairing material and it slowly brings the rail side wall into conformity.
Once the rail starts to look fair, we then move to this step:  Applying fairing material with a curved spreader.
Just a cheap plastic spreader will work.

We bend it and evenly follow the rail edge with the material.  This fills in voids and gives us a skim coat to hit with additional sanding with a sponge.
The whole process takes a lot of sanding.  No way around it.

And more fairing...

After several passes with sanding between layers of fairing, the bow was getting close.  But alas, I sanded through to the foam.  I've struck foam!  No major deal.  I scraped out the offending soft spot and filled with Bondo.

The side rails are getting close.  It is to the point were the variations are not visible to the eye.  But if  you run your hand along the rail, you can feel subtle high spots and depressions.
When we feel these areas, we mark them add a spot fairing and next will move to long board sanding.
To this point we have been using a palm sander and a course grit sanding sponge.

Sanded through to foam.

Filled cavity, ready to sand again.

Side rail.

SUP Plug fairing: Step #3

The new Sea State board we are molding is in the first stages of fairing.  The substructure, built of wood is as close to fair as possible.  This is helpful.  It allows us to keep the fairing materials we will add thin and get to the finish sanding stages sooner.  If there are underlying rough spots in the plug's structure, you can spend a great deal of time fixing it.  It pays to go slow and not create problems that have to be dealt with later.

Today we are giving the entire plug a skim coat of fairing material.  Later today it will get a sanding and an additional fairing coat.  After that is sanded we will decide if additional passes are needed.  Once this process is completed, it will be time to move to spaying gel-coat.  Gel-coat bonds to the plug and provides a surface that can be sanded and buffed to a high gloss.

These two photos show the bow of the SUP before and
after a bit of fairing.

The dimensions of the board are:

12' length

32" max width

5" thick

The estimated volume will be about 230 liters.  This will be a stable board for novice riders up to 275 pounds.

Here is an overview of the bottom of the SUP's plug..