Newbie- Need help on mold building

[pendelton]

Hello All
I am new to your site and so far think it is great. Tons of great info on here and most of it usefull. I am interested in building my own boat and would like info on starting with the mold. Not totally new to boats since I worked 6 years on metal boats. However I am new to fiberglass. I have been searching for info on mold materials and so on. Havent found to much as far as the basics on materials for molds. So if someone could direct me to a great book or something I would appreciate it. Thanks to all and I hope to continue enjoying this site.

[jim lee]

How large of a boat are you looking to start with? Maybe you could find a mold somewhere that would be "Good enough" and have a go at pulling a part from it.

There's lots of molds sitting around. Well at least in this town.

-jim lee

[pendelton]

Thanks for the thoughts. I was thinking of trying something small first to get the hang of it. Part of the reason for starting small was also to learn something about building a mold to. I appreciate any input. Basically I have been trying to figure out the best material to build a mold out of and also to learn about structure (ie: stringers and bulkheads and so on). Thanks for the input.
Also what do you think a mold for say 16' to 18' boat would cost if I found one used laying around?

Thanks

[jim lee]

Its all in knowing were to look. From what they've been telling me here in town, many molds are "timed out". Basically no good for commercial work. At least not without a lot of work. Sometimes you can get a small one for nothing.

For example :

We picked up this Sabot mold for nothing out of a scrap pile.



But that didn't stop us from building a pretty cool little boat out of it..



Ta da!



The point of this is that it may be a good idea to try making a part before tackling a mold. This is how we got our feet wet in all this nonsense.

There is a lot of black art in tooling. Much of it is in the plug construction. We've even added some of our own.

Shut up and tell how to make a mold?

Fine, when we make a mold its typically...

Now remember -everyone- makes molds differently. Some use chopper guns, some use hand layup. Some use fancy mold making resins that won't shrink if used properly. No two mold builders will agree.

What we do..


Sealer and Lots of hand wax on plug. Maybe 6 coats? Don't use electric buffer when doing the wax. Wet a rag with PVA and wipe down the plug. Now you are ready..



A) Gelcoat, sometimes two shoots to get about 30 something mills. That would be tooling gelcoat, really tough stuff. Let it kick, but not too much.



B) Skin coat, double layer of 3/4 or 1 oz mat. Whatever we have a lot of laying about. Let it kick..



C) Now, we drystack whatever Biax is either laying about or cheap. Favorite is 1808. four layers.



D) 3/4" Balsa core. Over everything possible. There's a lot of choices here that would work, but Balsa is light.

E) Four more layers of Biax, typically 1808.



F) Now build the "Egg crate" reinforcing ridges. We've been using 1 1/4" balsa for this. Mostly because where we found that free mold, we also found a nearly infinite supply of 1 1/4" balsa. Slice this into 8" strips and build your framework on top of the drystack. Round the edges. Make sure it fits -tight-. Any gaps will cause bridging and heat and troubles. Also make sure all of the egg crate is over cored glass. If you cross a non cored section, you will see it in the mold.

G) Cover the entire framework with 1808 or whatever your using. Reinforce the corners some while your at it.



F) Add plumbing & vacuum bag the thing.



H) infuse your mold.



When your finished it should looks something like this..



Many molds need extra frame work. This is typically done by hand..



All finished, being cleaned up to make a part.


Our molds don't have the perfect surface, but what we loose in surface quality we gain in dimensional accuracy and lightness. It depends on what is important to you. The infused molds are coming out probably 1/3 the weight of the hand layup versions. For smaller molds its nice to be able to carry them about.

Good luck!

-jim lee

[pendelton]

Wow. Thanks for all the great info. I see your in washington. I am just here in oregon. Wondering if you would know off hand of someone to call or show up to to find a mold I can restore and use? Your right this stuff is all about knowing where to look and I really dont. Thanks for all the pictures and info. Way more then I could take in but I think that was your point. Again thanks and if you have any ideas on a mold to start with I would greatly appreciate it.

[jim lee]

The 8 foot dink mold and tooling, make an offer and all we can scrape up is yours. (You have to pick it all up)

-jim lee

Changed mind, If you pick it up, you can have the entire pram building package for free. We're done with it. Or at least as much of the package as we can find. Timed out Sabot mold, rebuilt seat mold, core & glass cutting templates, wood templates. Some may be missing, but none of it existed when we started, so you can make up what your missing.

-jim