Need some help (ideas, feedback) with laying up a hull(s)

[kfxguy]

I decided I want to try my hand at something a little different than just building boats. I want to make some of my own hulls. I've got carbon and fiberglass layup experience (not a ton) and I'm well equipped to do pretty much anything I need to. I have a bagging setup with a nice vacuum pump. I've turned out done nice carbon sheets. I have plenty of mold release and wax. I know the basics of the process but I want to eventually turn out some nice hulls in fiberglass and carbon. I have a set of molds to start making a little 19" mystic to start off with, sent to me from Danny. I'll post some pics this evening when I get home and open the box up. What I'd like is some tips or any insight on making the final result better.

Here's some of my own thoughts and ideas:

I don't like gel coat. To me it seems to be a weak point to cause cracks. May not be all the way through but who wants to paint a boat and two weeks later start developing cracks? That's not ok with me.

I know without gel coat it's easier to get pin holes in the outer layer. I've got some ideas for that to try. First is lay my base coat of epoxy and go over it very quickly with a small torch. It brings the bubbles out the epoxy quickly.

With carbon, my idea was (and looks like how it's done to me) is lay a thin surface coat in the mold of epoxy to get in the sharp
Edges and corners. Apply flame to get air bubbles out. Then let harden. Not cure all the way. Then lay the cloth and wet out and apply vacuum. My thought is if I don't do it this way there will be voids in the surface layer all over the place and the cabin with be right at the top too which may be rough in some spots.

I have no idea how to join the top and bottom together to make a nice strong seam and bond. Ideas?

I plan on practicing with the hatch first of course to get an idea of what different things do.

[TheShaddix]

If you do the epoxy as your first coat and let it go to tack, it won't look too good, and since it won't go into the fibers, it'll be weak. I tried this method with a carbon sheet and it came out really ugly. You're better off just brushing the mold with epoxy, then doing your carbon layup with vacuum, then you just wet sand and spray with clear. If the vacuum bagging is done properly (all the right layers of materials), then the cloth will be conformed to every part of your mold. I don't see any point in gel coat other than just to make it look nice and white. Another reason is it works well when not using vacuum since there is no way to make the cloth go into all the sharp corners by itself.

[kfxguy]

If you do the epoxy as your first coat and let it go to tack, it won't look too good, and since it won't go into the fibers, it'll be weak. I tried this method with a carbon sheet and it came out really ugly. You're better off just brushing the mold with epoxy, then doing your carbon layup with vacuum, then you just wet sand and spray with clear. If the vacuum bagging is done properly (all the right layers of materials), then the cloth will be conformed to every part of your mold. I don't see any point in gel coat other than just to make it look nice and white. Another reason is it works well when not using vacuum since there is no way to make the cloth go into all the sharp corners by itself.


Gotcha. Good info. I'll try a hatch this weekend. I should have enough material to do one. I'm waiting on some more fiberglass cloth. Don't think I'm gonna waste any carbon until I feel like I'm making a good enough part out of fiberglass.

[JimClark]

Maybe Brian will chime in on this topic.

[monojeff]

If only you could tag people like on Facebook.

[CornelP]

Here are a few things to consider:

- do not rely on epoxy alone for angles and strakes: we fill the corners and strakes with a mix of resin and fumed silica and apply on top a very thin layer of glass (40g/sqm). For added strength or deeper strakes, always fill with carbon rowing, it will add a ton of stiffness.
- the fumed silica will make the resin clouded and whiteish... add some graphite powder if the white bothers you.
- let the first coat go into gel state (tacky) so that nothing will move when you start adding layers.
- be very generous with the resin, you want to wet the layers more than needed to avoid holes. Most of the excess will go when you apply the vacuum (do not go crazy with the vacuum, you only need to set the bag and take out the excess). Always use a resin trap to avoid any clogging in the system.
http://www.easycomposites.co.uk/#!/vacuum-equipment-and-supplies/vacuum-pumps-and-equipment/professional-resin-infusion-catch-pot-small.html

- when both semihulls are in a gel state (or a bit over), remove the bag and cut the excess fibers flush to the mould flange with a sharp blade: try not to move the fibers too much and do not remove from the mould for best results.
- after cutting the excess, close the mould and apply either a glass wove strip or cut your own from a strong fiber (100-160g/sqm). For a cat, you can go with the same size as the hull heigth, it will make the added layer almost invisible.
- for the best possible strength, always close the hull when it is in gel.
Check these guys out, they have some very good tips: http://www.easycomposites.co.uk/#!/composites-tutorials
When in doubt, always ask...

Cornel

[kfxguy]

Thanks cornel for the tips. I opened the molds and they aren't what I thought they would be. They are either plugs to make molds or they are positive molds. I have a lot of work ahead of me to make the molds.

[Beaux]

How is the mold making going?

[kfxguy]

How is the mold making going?


Well I've got a rigger and a cheetah I'm trying to finish up before moving ahead with this project. I have only plugs right now and I have to order some more supplies too.

[Beaux]

Cool, just checkin.

[grsboats]

Travis gel coat is great when applied in a very thin lawyer with a specific gel coat spraygun BUT I agree that with time hairline cracks appear due to the tortion of the hull so I also do not use gelcoat on my boats.

[grsboats]

As Cornel mentioned I like to use roving fiber for sharp edges.Gill