Prepping for Glass

/ Capt Kise

As mentioned in the previous post, I’m playing some catch up when it comes to writing these. This gives me the benefit of hindsight when writing, and for this stage that will be very beneficial to the reader who is looking for guidance on their own build.

SHAPING FOAM IS EASIER THAN SHAPING FIBERGLASS/FAIRING COMPOUND!!

Now is the easiest opportunity to spend some extra time getting the hull shaped and fair. Later on it becomes more more labor intensive to remove material. When I finished this stage, I felt I had it really close to being perfect. Later on after I got the glass on and fairing compound I found myself spending hours fixing some things that could have been done in minutes if I was only working with foam. So, if you taking on project like this, I strongly recommend taking your time on this stage.

Here are the steps I went through to take the boat from a bunch of screwed together roughed in foam, to being ready for glassing.

The fist step is pretty straight forward, Go around cutting and sanding all the overhanging foam and extra glue. Two tools that work really good in this process are pictured in the photo above (flexible saw and the block plane file).

Next I began to remove the screws that held down the foam to the frame beneath. The thinking here is that once its all glued together, then it should stay in place with out screws. Any screws left in the foam will begin to get in the way as you sand the hull fair.

Pay close attention when removing the screws and look for any mocement in the foam. For me the running pad popped up when I pulled the screws so I had to get on the underside and secure it back down.

The common next step after removing the screws is to fill the holes left behind as well as all the other holes and gaps with a mixture of epoxy and glass bubbles. The issue with this is once you put a bunch of epoxy filler on the hull, you now have two different materials with different hardness that make it more challenging to sand. So rather than removing all the screws and then going straight to putting filler in the gaps/holes. I recommend taking some time to get the hull shaped as you remove the screws.

Its important at this stage to put focus on getting the hull shaped. I’m not nescesarlly referring to making sure the measurements match the drawings, but rather that everything is smooth and transitions well. For me, I used a combination of measurement tools but relied primarily on the feel of running my hands over the area and looking for shadows using lights at different angles. This helps you see where you need to sand.

Using a laser to get the center line trued up. Notice all the different sanding tools…
You can see all the voids are filled with the a combination of epoxy and glass bubbles. This will take a few sessions to get everything filled. After it drys you may notice you need to put some more in the holes.
I went around the boat with a black marker and marked the areas that needed more filler. I was then able to work more quickly once I had a batch on the clock.
Fiberglass and tight corners don’t go well together. The outside corners will need to be rounded over slightly and the inside corners will need to have a filet put in them made from epoxy/glass bubble. This is really important because if you leave these corners like this, you are guaranteed to get air voids underneath the fiberglass that will need to be sanded out and repaired (not fun).
To get the filets in the corners I mixed up a batch of epoxy and glass bubbles then dumped into a zip lock bag with a hole cut in a corner and applied it like frosting a cake. Then I followed behind with a popsicle stick to get it smoothed out.
After I put in the filet, I came back and sanding it all smooth.
During this stage I prepped a flat spot in the bow for the bow eye. It was really difficult for me to find the exact bow eye I wanted but once I got it I used to as a template to make sure that my pad would be big enough. Also, this should have been sanded down a little more, I ended up with a bubble up here because the corners were to tight.
Here is the hull with all the corners rounded over or filleted.

Next it was time to install the form for the return flange. This forms the outer/upper boarder of the hull. For this I made a template spacer out of foam to make sure I had about the same distance from the foam to the return flange (PVC trim piece from Home Depot). More important than the space between the boat and the outside form was that the outside form would be straight. This way even if the boat is not perfectly straight, it will appear that way and be easier to marry to the deck later.

The PVC worked well except in the stern corners, for that went back to old fashioned pinewood. I used trim screws to secure everything and then wiped it all down with wax to keep it from getting stuck to the boat.
After the outside form was installed, I had another inside corner that needed to be filleted. On this particular outside corner I wanted there to be a round over showing when the forms are removed after glassing. To achieve this, I used a pre-fabricated wax fillet role and pressed it into place.
Last step before glassing the hull is to coat all the foam with “neat” epoxy resin (that just means no fillers). This is a very important step because it helps saturate the foam before glassing. If you don’t do this, the foam can pull the epoxy from the glass when you do your layup. It’s like why you wet the ground before you pour concrete on it, same idea.
And there you have it! A hull ready for some fiberglass or in this boat’s case, some basalt!

I still have few more post to get caught up to my current progress, but I feel like I have some momentum so maybe I’ll get them out before to long. Thanks for reading!

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