New part...

General Composites Discussions Composites Talk
#1

I am curious about laying up a boat hull.

A friend of mine who used to build chopper gun boats did the following:

Sprayed gelcoat and waited overnight for it to kick.
Laid in a layer of chopped strand mat and waited overnight.
Then they sanded off the nibs with 16 grit floor sanding paper and acetone wiped the inside of the glass.

Then they would lay roving in high stress areas, and spray chop into the hull to whatever thickness was required.

I am curious about this as the how its made tv shows, and online videos I’ve seen of boat production spray the mold, wait for it to gel up and then start laying the full thickness of glass… I don’t know if they wait overnight before pulling the part or how long it has to sit.

I’d like to spray gelcoat and wait for it to start gelling up and start laying glass to the finished thickness the same day, and preferably be able to pull the part the same day!

Thanks… I’ve been doing a lot of reading about how each step is done and what all it takes, but it seems like a lot of primers and how to’s lack the time line.

Thanks,

Zach

#2

“Some things are worth waiting for, sh*t normally turns up in double quick time”

Rich Hall.

#3

It is perfectly possible to produce multiple parts from a mould in 1 day or 1 shift. I have seen mould cycles as fast as 8 minutes, using a heated and cooled mould, using an RTM or RTM light process.

However, there is quite a challenge in controling dimensional stability and surface quality.

For boat hulls the process your friend performed would be more desirable, from a technical point of view:
-the gelcoat has had time to reach a sufficient cure, thus helping surface quality
-the first layer can be used with a different resin (vinylester) to improve osmosis resistance. (please also use ISO-NPG gelcoat for best resistance)
-only after sufficient cure of the skin layer the bulk of the laminate is applied.

The How it’s made shows are edited and will never tell the full story. Although they do have some nice footage every now and then. I hope you do not believe everything that is happening at Orange County Choppers or Hell’s Kitchen either…

If you want to setup a high speed production facility, get some reps of high quality suppliers in, and have them guide you through their product lines to select tooling materials, gelcoats and resins that work in those environments.

#4

Thanks for the replies guys,

I’ve made plenty of xxxx in my day, but I’ve also had pretty good success when it comes to learning from other peoples mistakes.

Herman,

Thanks, I’ve been having a tough time as most of the introductory polyester books don’t get into enough depth of the process… and Cooks Composite book is geared toward helping keep the process up and going when it goes wrong.

I’ve been dealing with composites one, but I’m not a big enough fish for them to do much teaching of their product lines.

I’ve been trying to find a detailed schedule, as in a time table of the process. Some people spray the gelcoat, come back tomorrow… others are laying a skin coat after an hour. Lots of ways to do things, and maybe no right way…

Thanks

Zach

#5

Thanks for the help guys… Built the mold.