DIY - Fiberglass box construction
Learn the basic technique on how-to build a fiberglass enclosure
Previous: Step 4: Make a top wood trim piece
Step 5 First layer of fiberglass
This step is easy if you have worked with fiberglass before. If not, test out your efforts on a little test piece. The experience you gain is worth the material you waste. I have seen many people try a big project like this and mess it up and waste big bucks.
Work with little strips up to 4" x 10" in size. Use 8 oz material. If you have 4oz, double it up or make two passes. Make sure to completely saturate the fiberglass with resin. The trick is to use just enough resin to saturate the mat. Too much and it will add unnecessary wait and be a little bit weaker. Too little and it will be very strong. Make sure to get resin between the fiberglass, TacMat and your wood trim ring. (This is an important step)
NOTE: A word on hardener. I probably use too much hardener. I take the recommendations and double it (or more depending on the temperature) Don't add too much or you could catch the resin on fire. Don't laugh, this example you see here started to smoke on the second coat. (I guess I used a litter more than double the recommendation)
back 
topStep 6: Let the resin harden
I
know, you can't wait to finish. Do rush! this is the time that it is easiest
to make a mistake. Notice the resin can on the wood ring. I put that
there to add some weight to make sure that there is a good bond between the fiberglass
and the wood ring. Make sure that the fiberglass is dry to the touch before moving
to the next step. If you cannot wait, make sure that it is hard but tacky.
Step 7: Add glass to the underside of the wood ring
Use thin 1" strips and "tuck them between the underside of the wood ring and the fiberglass. This is where you wish you have the lip as close as possible to the edge of the fiberglass wall. (Makes it a whole lot easier) I use the tuck method. Wet the cloth with
Step 8: Add a second layer
Repeat "Step 5" with a second layer of 8oz cloth.
Step 9: Let it Dry
I
know its killing you.
OPPS! You see this difference in color? That is because I mixed this batch a little too hot. It is still useable but if it cracked, it is dumpster food.
Step 10: Apply DynaSpray
DynaSpray is liquid Dynamat. This is a great use. The DynaSpray sticks well to the fiberglass and further reduces that fiberglass "ring" that so many people have. Here I am using the kind from the Jug, but the can also works well. When using from the Jug, use a disposable brush and paint it on. I recommend about at least an 1/8" thick or about the thickness of a nickel. DynaSpray is water soluble (won't catch on fire like other types of liquid damping material) and is non-toxic. It is also a great undercoating once dry.
Step 11: Let it dry
DynaSpray
with dry to the touch in about 2 hours. Complete dry time is about
24-48 hours. You could attach the top plate after a few hours. For
best results wait overnight to use your enclosure.
Summary
At this point, the bottom half of the enclosure is basically complete. For a little better performance, you could resign over the top (light coat) and re-DynaSpray. When you install the top plate, make sure to seal properly with wood glue or silicon.
WARNING! What ever you do. DO NOT USE LIQUID NAILS! This material outgases and is highly flammable. In other words, if you were to use liquid nails and seal the top plate and bolt the woofer in and use is you will probably create a loud explosion and possible a fire. Don't laugh, more that one installer I know has had this happen to them.
TacMat
(a Dynamat Product)
