I need to build a fiberglass cowl for a 40% Jack Strickland Laser. I have made the styrofoam plug. is there a How too thread that shows you how to lay down the fiberglass?

My first attempt ended up

Now I need to make a new plug.

Tony

Originally Posted by tonyc9075

I need to build a fiberglass cowl for a 40% Jack Strickland Laser. I have made the styrofoam plug. is there a How too thread that shows you how to lay down the fiberglass?

My first attempt ended up

Now I need to make a new plug.

Tony

First thing,
did you cover the plug in anything like wax paper or parafin wax. That will make the plug easier to remove.
Second,
What kind of glass and resin did you use. I would say 2-4 layers of 1oz.-1.5oz cloth should be enough.
Third,
How did you attempt to remove the plug.

Finally,
Im guessing you had some bad bubbles and dry spots. My secret for that issue is to roll the fiberglass down with toilet paper. It pushes the glass down and removes extra epoxy or polyester resin.

Good luck,
Jon

Tony, if you want to do it right, pay a little like I did with this fantastic Manuals:

www.fiberglassmoldmanual.com

Just go there and You will see!!

What I attempted to do was build a cowl from Styrofoam, and then cover the Styrofoam with glass cloth. After the cowl hardened I intended to remove the Styrofoam plug leaving the fiberglass shell.

Mistake 1, I did not use epoxy, used polyester resin. Melted the Styrofoam and destroyed the plug.

But even if it had not melted the Styrofoam, my application of chopped glass cloth to the plug did not look good. It had lumps to start out with.

These pictures are not mine, they belong to a plane build by Sensei.
This is what I would like to do.
I hope its OK to repost a couple of his pictures.

Chopped glass will do that. It is a real pain to mold and really not to strong. You want to use the weaved stuff which Im now sure you know. And epoxy is much easier to work with, doesnt stink easier to finish.
Good luck
Jon

Originally Posted by tonyc9075

What I attempted to do was build a cowl from Styrofoam, and then cover the Styrofoam with glass cloth. After the cowl hardened I intended to remove the Styrofoam plug leaving the fiberglass shell.

Mistake 1, I did not use epoxy, used polyester resin. Melted the Styrofoam and destroyed the plug.

But even if it had not melted the Styrofoam, my application of chopped glass cloth to the plug did not look good. It had lumps to start out with.

These pictures are not mine, they belong to a plane build by Sensei.
This is what I would like to do.
I hope its OK to repost a couple of his pictures.

Two plies of 8 oz/yd overall with buildups around the lips and bolt flange.
Epoxy for sure.
You can use a low temperature iron on film as a barrier between the foam plug and the fiberglass... even wax the plug once covered with good old carnuba wax.

Originally Posted by Mithrandir

Two plies of 8 oz/yd overall with buildups around the lips and bolt flange.
Epoxy for sure.
You can use a low temperature iron on film as a barrier between the foam plug and the fiberglass... even wax the plug once covered with good old carnuba wax.

Do I cut the glass cloth into strips? Lets say 1inch by 12 inches. I am thinking that because the entire cowl is curved the cloth will not change direction without puckering? Strips would allow laying up in different directions.

While you could do it in strips it wont look so nice inside. Doesnt matter much for the mold as long as you dont get voids etc.
For the final layup from the mold you pull from your plug:
First I'd suggest getting some 3/4oz cloth(Tower has it) for the first layer...the finer weave will show less print thru which is where you can see the cloth, its also conforms well.
Second, I'm guessing the chopped glass you mention is whats called matt cloth, once wet you will find its the most conformable so its good to build up the tight radiuses like at the cowl opening.
You should plan on using 4-5 pieces of cloth (2-4 oz) ..instead of strips..like one for the top, bottom sides etc. Of course, overlap your edges.
Use slow cure resin, I prefer epoxy as its better for holdung cloth on surfaces. Use will need either a roller or squeege to get the resin worked in and air bubbles etc out.
Use either a squeege or the blotter method to make sure you have NO extra resin which could run and of course adds weight. Once you have the cloth fully wetted out, you cant pull out too much resin.
Did I mention that epoxy wont melt your foam?

Originally Posted by tonyc9075

Do I cut the glass cloth into strips? Lets say 1inch by 12 inches. I am thinking that because the entire cowl is curved the cloth will not change direction without puckering? Strips would allow laying up in different directions.

If you are going to use the lost foam method get crow foot weave cloth. It will conform much easier than regular cloth. 3 layers of 3.2oz. should work well. If you think it is too soft after the form is removed add some 6oz regular glass cloth to reinforce it on the inside. Use epoxy laminating resin (I like west systems). Get your materials from a composite supplier not the hobby shop. You will get much better quality products.

Mark