Thread: Fiberglass and MDF sub enclosure walkthrough

notice in this picture:



There is a bump in between the two subs from a bad cut in the center divider. That and where there was a seam in the fleece, it didn't stick together the way it should have. Lastly, since it was "just for fun" I didn't budget what I should have to get this done, and ran out of resin way earlier than I thought.

So if I were to do it again, I would have redesigned the center divider, and bought more resin, and mat.

Too bad . . . you had a nice plan and a nice setup on the worklog. It would have been fun to watch it grow. I'll watch for your new box.

Originally Posted by slash

Good work up, but I only have one thing to criticize, the use of fleece...

I am not flaming you or anything, but wanted to state this for newbies to fiberglassing.

expandable polyester like swimsuit material or spandex is much better than fleece for fiberglass work. It is so much easier to make complex curves with, and you can stretch it uber-tight holding it down with CA Glue or staples.

When applying resin on spandex type material, you do not have to use as much, thus reducing some of the costs involved in enclosure fabrication. Fleece soaks up way too much resin and gives people a false sense of security because of the thickness and the it is strong as a rock attitude after the resin dries. I have seen too many people crack boxes because they used fleece, then not enough fiberglass cloth for strength.

Yes, we all know that the number of layers of fiberglass cloth laid down gives you the strength to your structure. Fleece just gives too many people a false sence of security. A sub enclosure has to be balls-to-the-wall solid, with enough layers of fiberglass.

I just wanted to make this point so that newbies to fiberglass don't fall under false sense of security. Once again, not to be as a flame, just informational.

As noted here:

Originally Posted by monkeyracer

7. Strech fleece (or alternate material):
I used a polyester based fleece (since the resin is polyester based) that I purchased at wal-mart in their remnant section, it won't matter what color or pattern it has, since there will be many layers of fiberglass mat on top of it. As long as it stretches, and has a polyester base, other fabrics may be used.

Other fabrics may be used. I got my fleece for a couple bucks, but in the grand scheme of the project (and maybe what led to my failure) the extra couple bucks for spandex would have been outweighed in the savings in resin I would have not had to use. Also because it stretches farther than the fleece, I wouldn't have had a seam and the issues associated with it.

To the n00bs: The base layer just needs to start the shape, there is not supposed to be any structure yet, that's where the actual fiberglass comes in.
Since hindsight is 20/20, I now wish I used a thinner base layer like slash mentioned, and I may have actually completed the project.

My next box will be made of MDF, and covered in the same carpet as the trunk. Since I don't really need any crazy shapes (just a box) MDF is less expensive and a little easier to work with.

I don't want to discourage anybody reading this thread from trying this out for themselves. The best way to learn something is by making mistakes, and learning from other peoples' mistakes.

After you stretch your material, but before you lay down any resin, measure the interior volume (CF, cubic feet) of the enclosure. If it is not right, rearrange the supports and/or move the sub ring in or out and re-stretch the fleece. As long as it's pretty close (check the sub's recommendations) then you'll be just fine. It's a little bit of a hassle, and if it's your first time trying a fiberglass box, it would be a good idea to buy extra fabric just in case. I used autocad to help estimate the size of the box, but with the complex curves, it's almost impossible to get it down to the cu. in.

Poly fill helps to "trick" the sub into behaving like it's in a larger box since the back waves are slowed down and don't negatively affect the front wave of the sub. If you were to scream into a pillow, it will sound like you are farther away than you actually are since the poly fill in the pillow slows down the sound waves, and reduces their amplitude. Really you would want to do this if you made the box a little too small.