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HOT COAT (fill coat)

The hot coat is mostly used to fill the gaps in the cloth weave.  It should not actually be hot.  Many shops put extra catalyst in their hot coat which makes it heat up.  This is done to save time. 

If not doing a gloss coat, prepare the laminate coat almost as if it is a hot coat.  Sand the laminate lap lines, corners, drips, and lumps very carefully before hotcoating, if not doing a gloss coat - this same sanding can be done with less perfection if a gloss coat is being applied. See GLASSING & SANDING.

Follow the steps:

1. Turn the board bottom up.
2. Wrap 1" masking tape (chemical resistant type) around the entire circumference of the board at mid rail. (Figure 18).
   
   Figure18
   
   
   
   
   
   Press the top edge of the tape down firmly and let the bottom edge hang free (lets resin drip off).  Pull the tape up every foot or so and put a  crease in the middle of the tape to make sure it does not flatten out on the board. 
3. Mix resin as before but use about 1/2 as much as when laminating.  If using polyester resin add styrene wax surface agent (wax)(see MATERIAL LIST).  The wax makes the resin set up non tacky so it can be sanded.  Wax should be added to polyester resin at a ratio of 10cc wax to one pint resin (2%).  Measuring syringes make this easier.  See RESIN AMOUNTS for help figuring amounts.  Mix this batch with a higher percentage of catalyst than the laminate. Do not use styrene wax surface agent, or a different hardener percentage with epoxy.
4. Drag a finger around top tape edge again.
5. Pour about half the resin on one side and half on the other (two continuous ovals).  On the bottom hotcoat keep poured resin at least a foot away from the nose tip, so resin will not run off. 
6. Turn the cup upside down on a dry part of the board. 
7. Use cheap (throwaway) 4" natural bristle brushes or foam brushes with epoxy. Use cheap natural bristle brushes only with polyester.  Foam brushes are roughly half the price of the cheapest natural bristle brushes and work well with epoxy resin.  Start spreading the resin with the brush as you did with the squeegee on the laminate coat (holding the brush at a 45 degree angle to the stringer). 
8. Take the cup off.  Get the resin roughly even over the flat sections trying not to let it run off the rails.  Work the resin slowly, roughly evenly over the rails, coating them lightly to the tape.  From now on cover the entire surface of the board with each set of back and forth strokes.
9. First stroke longwise one entire surface.
10. Stroke 45 degrees one entire surface.
11. Stroke 45 degrees the opposite direction.
12. Stroke one entire surface crosswise.
13. Brush two continuous circles brushing around the tape line (do not smash the free hanging tape edge into the board).
14. Check with a moveable light all along the tape line for dry spots.
15. Stroke the entire surface longwise very lightly and, slowly one time, including the rails.
    
    
    
    
    
16. Throw away the cheap brush (it will take more time to clean it than it's worth and it won't be right anyway).
17. Wipe out the cup with a paper towel.
18. Pull the tape when the resin gels.
19. When it hardens, flip it and repeat, except for the following:  When hotcoating the top remember to start all longwise strokes from the nose end.  Use slightly more brush pressure at the bottom of the curve, letting up towards the tail.  This will even out the resin which tends to accumulate in the bottom of the curve.

If applying the #16 sanded traction surface mentioned in GLASSING, do the following.  Do not put the styrene wax surface agent in the top hot coat.  Apply the top gloss coat (with styrene wax surface agent - polyester only) directly over the hot coat without sanding the top hot coat.  Remember; there is no styrene wax ever added to epoxy.  The final #16 top coat sanded traction surface will eliminate the need for a sanded hot coat and a smooth gloss coat.  When using this method, reduce the resin by two to four ounces (depends on board size) on each of the two top coats.

One weight and money saving alternative is to not do a gloss coat.  If you carefully sand the lap lines and corners etc on the laminate coat, the hot coat can look acceptably smooth.  This will not give you a board with the perfect look of a shop made board, but many people find the weight and money savings attractive.  The difference in strength is barely noticeable.  I recommend not sanding the hot coat if foregoing the gloss coat.  If the cloth is slightly sanded into, the cloth will "wick" water to the foam.

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