I want to learn the basics of fibreglassing just for the hell of it.

Ive chosen a lip spoiler as a project as I've always liked the look of them.

My plan is to laminate 5mm MDF strips that are clamped to the boot lid to get the shape.

From there sand and cut to the profile chosen.

Then I plan to fibreglass that.

My questions are:
Mdf or plywood?
Do I fibreglass the wood inside or do I make a top mold fill it with expanding foam and then fibreglass the bottom in?
What profile do you like?

Any advice or suggestions would be great.

The pictures show the basic idea. Dont mind the tape just finished repainting the doors and they need sanding.

http://i42.tinypic.com/4r23k6.png
http://i40.tinypic.com/35aljcz.jpg
http://i42.tinypic.com/35jmadu.jpg

My questions are:
Mdf or plywood?
-MDF will swell up if/when it gets wet, but might be a bit easier and more uniform material to work with.
Do I fibreglass the wood inside or do I make a top mold fill it with expanding foam and then fibreglass the bottom in?
For a one-off probably just keep the wood inside and use a thin layer of fiberglass to keep it all together and waterproof, then smooth it out with auto body bog.
What profile do you like?
Your car, you should be picking what you like best lol
Any advice or suggestions would be great.
I've got one almost done for a flush top/rear extension that I'll be doing a mould from if I ever get it straight enough that I'm satisfied.

If you feel like it mind showing me some basic pics of it on the car might prefer that style ;)

Also would mdf swell because of resin? that was mhy main concern

I haven't glassed onto bare mdf yet, but it isn't very runny and goes touch dry within an hour usually so it shouldn't be too bad.
I have a pic of it on the boot I'm working on, but not on a car yet.
http://picturestack.com/926/209/9Zs1877vV.th.jpg (http://picturestack.com/926/209/9Zs1877vV.jpg)

I wouldn't be using the timber in the spoiler, id be using it strictly just for the mold so swelling wouldn't be an issue because you will either be taping it up or gel coating it if you want to pull the mold off once dry.

I would be glassing over the top of that, pull the mold off, remove the timber and yes using some expandafoam to fill the bottom in, and then apply a thin layer of bog over the whole lot, prime and paint.

1 - Plywood to start the basic mould..
2 - Glass over it..
3 - Pull the plywood mould out and fill your fibreglass spoiler with Bostik Expanda Foam..
4 - Bog over it - At least 2 layers, so you can sand it back and get a continuously smooth finish..
5 - Prime & Paint..
6 - Clear Coat..

Happy Days!

SuFz :ninja:

Now read this topic. Many photos and basic principles. After a couple of months I will be doing a rear spoiler. http://www.aussiemagna.com/forums/showthread.php?t=92847&page=1&highlight=

from what you and peaandham have said it seems like your saying after its full of foam and the bottom cut flush just bondo? wouldnt I need to glass the bottom in? you may have not mentioned it because it was implied :P sorry if it was.

from what you and peaandham have said it seems like your saying after its full of foam and the bottom cut flush just bondo? wouldnt I need to glass the bottom in? you may have not mentioned it because it was implied :P sorry if it was.

You can for extra strength, but not entirely necessary.

pretty sure people use MDF + Fibreglass in subwoofer boxes with no issues?

pretty sure people use MDF + Fibreglass in subwoofer boxes with no issues?

I think with MDF we're worried about swelling over time..

Boot Installs dont get battered with water.. Spoiler will cop more water in a week then the boot install will in its life!

SuFz :ninja:

pretty sure people use MDF + Fibreglass in subwoofer boxes with no issues?

Correct.

would the resin, fibreglass and paint not waterproof the whole thing? also I'll likely add some vinyl to cover the whole thing. cheers for the help guys.

Resin and Fiberglass will make it very water resistant, but if your painting it, the primer, top coat and clear will do that job.

If your vinyl wrapping well it depends on how well you wrap it.

As long as you take your time when you're building and glassing the spoiler.. You'll be fine!

Once mine is done.. I'm happy to send you some pics..

SuFz

went out and bought lots of stuff for the coming weeks :D Given all the knowledge here ive opted for the slack way of just glassing the mdf rather then making a mould and filling it.

Yeah pics would be great. will throw some in when its all done.

Fiberglass is slightly porous on a microscopic level, gel coat and/or paint on the outside should stop it. If you seal wood in there, make sure it is dry, you don't want moisture steaming up inside your lip on a hot day and trying to get out. The wooden reinforcement in fiberglass boats is marine ply, I'm pretty sure its made with a sealing waterproof glue incase any moisture gets past the fiberglass so it doesn't rot the wood, and probably stops moisture getting out too. Also, fiberglass won't usually sit flat over sharp corners unless you fiddle with it a lot.

Seriously, if you want to play with this the book referenced by redliner in one of his fibreglassing videos (linked in a recent thread posted by him) is easily worth the price ($15 or so when I bought my copy years ago).