Q&A – Fibreglassing method 1 – small areas


This is the normal method for fibreglassing small areas – typically using fibreglass tape to hull seams.

Here I document the process of coating the hull and glasstaping the chines in one hit.

Integration of different steps in this way is one of the major efficiencies of modern epoxy boatbuilding.

However if simply glass taping the seams and not wanting to coat the surface the same method can be used with the simple change that a coat of epoxy is simply brushed onto the areas where the tape will be placed rather than over the whole surface.

Preparation
The method for fibreglassing hull seams can use the same wet-on-wet approach as for large areas but with a small change to integrate the application of the glass tape.  It makes it a very clean and tidy process once you get the idea.

Fill any screw holes, allow the epoxy to cure and sand flat.  Radius the edges that the tape will be applied to.  A minimum of 3mm (1/8”) is just enough to allow the glass to wrap around without lifting.  A bit more is better – but don’t round the edges around the transom at the stern too much – the water wraps round the corner when sailing causing drag.

First Coat and the secret smoothing method
Apply first coat of epoxy to hull (pic below) or just brush it on the areas where you are glass taping..  Note the masking tape to prevent epoxy drips running around the corner onto the deck.  The finish can be quite smooth by holding the roller so it can’t turn and lightly and slowly skid it across the surface to pop bubbles and get rid of roller marks – but work from the middle of the length of tape towards the ends not from the ends towards the middle

Apply epoxy to where needed on surface.  Here I am applying it to the whole bottom

Apply epoxy to where needed on surface. Here I am applying it to the whole bottom

.Put glass tape down in wet epoxy (pic below).  I should be wearing gloves.

Place the glass tape into the wet epoxy.

Place the glass tape into the wet epoxy.

Detail of glass along transom.(pic below).  Use the roller or a cut down disposable brush (bristles not longer than 25mm (1”) to work epoxy into the glass tape – it goes clear when the epoxy has wetted it out correctly.

Dont apply extra epoxy yet.  Just use the roller or brush to push the tape evenly into the epoxy that is there

Don't apply extra epoxy yet. Just use the roller or brush to push the tape evenly into the epoxy that is there before adding more. If the glass doesn't go clear then it is time to add a bit more resin.

An example of wetting out (pic below) – the glass along transom is now wetted out and becomes clear.   The glass on the corner is being trimmed to length.

Trimming glass tape to length.  Leave a little excess - it can be trimmed tomorrow.  But if several layers will overlap it is OK to cut it short of the other tapes.

Trimming glass tape to length. Leave a little excess - it can be trimmed tomorrow. But if several layers will overlap it is OK to cut it short of the other tapes.

Roller method for wetting out (getting the resin into the glass).

Using a roller to push the trimmed glass tape down into the epoxy.

Using a roller to push the trimmed glass tape down into the epoxy.

Finished taping and second coat is put on when first gets tacky – roll the epoxy out well so as to not add too much weight – but roll a little bit extra on the tape – too much and it will run down the side.

Moving on to rolling on extra coats as the previous coat goes tacky

Moving on to rolling on extra coats as the previous coat goes tacky

When epoxy goes tacky apply a third thin coat and skid the roller to give a smooth finish.

If the weave pattern is still visible in the glass tape roll another coat to fill up the weave when the epoxy goes tacky again.

Leave epoxy to cure.

Tidy up the next day
The next day – while the epoxy is still a little cheesy (if you leave it too long it will make this hard work) set a fine spokeshave fine and get rid of the edge of the glass tape.  Keep the body of the spokeshave over the glass but set the blade with a tiny bit of depth on the edge side but no depth on the other.

Work carefully and slowly.

Then sand the glass tape using the random orbit sander and 120 grit paper.  Keep the edge of the sander lined up with the edge of the glass, but keep the sander body over the tape.  Angle the sander – concentrate a bit of weight on the side of the sander over the tape edge and keep the rest of the sander off the surface of the tape.

Finish off by sanding the rest of the bottom to a matte finish (no gloss) but don’t go through the epoxy to the timber.

Generally I brush a couple of thin (ie thinly applied – never use thinners or solvents with epoxy) coats onto any areas where I go through to the wood – allow that section to cure and give a light sand – making sure I blend the edges of the brushed area.


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