Fiberglass seat help

[Heartbreak kid]

So I am considering building my own fiberglass seat and have made a positive mold from wood and foam. From reading a lot of builds I feel really good about all aspects of the build except the most important part: the glass. I feel like most threads kind of gloss over this part...and having never fiberglassed something before I am a little confused.




1) Specifically what types of cloth and resin would most people recommend? How do I look for them at the hardware store?


2) When I am cutting my cloth some people seem to cut it in the general shape and some seem to use strips? Do they need to overlap if I cut them the shape of the mold? How much overlap do I need?


3) Should I be able to lay down all of my cloth including all the layers without it drying (Im shooting for 5-6 right?)



4) Lastly it will be starting to dry and I will attempt to bush any imperfections to the edges with a squeegee correct?


Sorry if these seem like kinda of basic questions...I have just never seen fiberglass done before so Im having a hard time visualizing the process. Thanks.

 

[dean owens]

looking forward to the answers to these questions myself. plan on doing my own seat in the future and have no clue what i'm doing.

 

[VonYinzer]

If youre just doing a one off glass seat you can buy both chop mat and cloth from AutoZone. Also get a big can of resin. Cover the mold in a flexible plastic tape or even saran wrap. Just keep it SMOOTH. Ive had luck with laying the chop down first. Cut it into small strips, and overlap. Than lay the cloth (also cut into pieces but as big as you can without folds) over it. Keep it wet at all times. Dont let the resin set. Do whatever you can to get rid of all bubbles. Do at least three layers of each. When it sets finally, sand it smooth and use a thin layer of GOOD body filler to do the final smoothing. Use as little filler as possible. Than, a good high build primer. Sand it smooth again, than lay some etching primer. Wet sand it smooth. Should be good.

 

[kneedragger74]

I did what Von has written and my seat turned out great (IMO ). I used saran wrap and used a heat gun to melt wax from candles and bruhsed it on the mold for a good release. It was all easier than I had thought it would be.

Dan

 

[cr8zy1van]

Kid,


Resins do not dry. There is a chemical reaction between the resin and the hardener that occurs (exothermic, so it creates some heat) This is what actually sets the resin. This can catch you by surprise in a couple different ways if you aren't aware of it. It can actually melt plastic mixing cups and destroy certain molds if mixed too "hot" - too much hardener. Your best bet is to mix just enough resin and hardener as you need... and keep an eye on the temperature of your work space. A hot day will make resin "kick" or harden a lot faster than a cold day. A trick to use on hot days and working outside is to put your resin into the fridge... this will retard the kick... and give you more working time. That being said... follow the instructions and you will be fine!
Also. Thicker areas will create more heat when it cures so will cure faster than skinny areas. Wait till your thinnest area is completely set before trying to remove from your mold.


(I am assuming you know that you need to protect your mold from the glass) Better to use extra release agent than ruin your mold and have to start over.


The glass needs to overlap. Larger pieces is better... more overlap to ensure fewer weak spots. Chopped mat should be ripped apart not cut so it can adhere better to surrounding parts. Thinner cloth can be used as your first layer to make sure you get into all the nooks of your mold. The chopped mat can be used to build up large areas that need support. The cloth will also stretch so you can really work it into the shape you want. I don't usually like using a squeegee on small projects. Its too big and can't get into all the voids of molds. A disposable brush works better for me. (and a squeegee is a good idea when you are worried about the final product's weight... getting all the unnecessary resin out will save weight, but its really unnecessary for small one off seats)


Some resins adhere to ANYTHING including previously cured fiberglass. For small projects like a cafe seat you could lay everything all at once and have it cure once. If you do not want to clean up cured fiberglass resin... and it will get all over... mask the area or put down some newspapers at least.


Here are a couple great threads on using fiberglass... Long but there is a lot of good information on both.


http://www.dotheton.com/forum/index.php?topic=6339.0


http://www.bayarearidersforum.com/forums/showthread.php?threadid=145975 - Thanks to FunJimmy for this link. It is great even if you know what you are doing with composites.


Here is a youtube clip that shows a brush instead of squeegee being used. Not too much technical detail, but good overview of the steps involved.
How To Fiberglass - Mold Layup


And another with better narration
how to make a simple fibreglass mould

And lastly... life is adventure, try it a couple times and you will be a pro in no time.

 

[Heartbreak kid]

Thanks a bunch...that helps alot.

 

[Heartbreak kid]

So I used floral foam and wood for my first mold but almost wish I had gone with something a little better than the floral foam. Considering maybe making another mold. I see a bunch of foams being used....does anyone have and recommendations for foam?

 

[rockcitycafe]

don't use autozone crap, anyone who does fiberglass work will never be seen using that stuff, even in an emergency
its styrene content is anyone's guess and how long it's been sitting in the can is also a matter of chance, as to when it will harden and how much it will shrink, it's a crapshoot

the best cheap modeling foam seems to be the polyisocyanurate foam sold as insulation at the hardware store, it's backed with foil, and comes in 2" thickness, the foil can be peeled off and sheets laminated to get your thickness

it carves easily, sands well, won't melt with exposure to polyester

technique-wise, get your foam straight before you even open a can of resin. this advice will likely be ignored, but it's the best advice in this comment

get a couple fiberglass rollers, once you start laying up torn sections of mat, the rollers will help you to even out wetter sections which will stand higher than your desired profile

a good thickness for a seat will be about 4oz per square foot (4 layers of 1oz, 3 layers of 1.5, 2 of 2, etc) of mat in the bump, about 6 in the seating area or any areas that may flex

for filling, wait until your resin cures fully, a couple days at least, and block sand the surface with 60 grit, this will knock down a lot of the highest areas and keep the seat from weighing 10lbs (8 of which will be filler)

use dyna, or some other professional grade filler, don't use bondo, it will just clog your sandpaper. when mixing, use a flat palette to mix, don't whip the filler, fold it with the paddle, it keeps little bubbles from being trapped. use the paddles to fill the low spots, the high spots will still be visible as bare glass.

block sand the whole part again, use your hands (not eyes) to read the surface, mark low spots or high spots with a sharpie, and add filler again

block sand the whole part again.

repeat, repeat, repeat

at some point, you may want to do a guide coat sanding, but with curved surfaces, reading with your hands is usually the better method.

when you're done, invite your auto painter friend over for beers and ask his honest opinion

then repeat repeat repeat.

after a few visits of the paint guy, you'll probably have something good



(and there's no reason to use a release agent, your foam isn't a mold, it's not going to be used again, and can be removed by using the back of a claw hammer and just chunking it out when the seat is finished, release agent will just make it harder to get a good surface on your laminate)

 

[Starboard M]

Couple questions from a glass newb:
On average, how much fiberglass is needed for the typical seat? I plan on doing a seat pan, and bubble, and would rather do all the glassing at once and not have to go buy more in the middle of things. I saw 8 square feet per package at my local auto parts place. Is one enough, or do I really need two?

How many layers are people doing? I guess it depends on what you are covering/using as a base, but 3 coats, or 10+?

Also, when purchasing, will a resin come with a catalyst, or do I have to buy that separate? For just a one off seat, how much will I need? Any particular kinds to use? Im reading about people using a jelly type, and a couple others I dont remember.

 

[ndromb]

Nice videos.