building a skiff out of female mould

I have recently been able to get my hands on a female boat mould and I am in the research stage of the "how to" on building a boat out of a mould like this

my first question is out of the 3 basic resins available on the market (polyester, vinyl ester, and epoxy) what type should I use to hand lay (laminate) fibreglass into the mould. I will be applying gel coat to the mould prior to laying the fiber and resin

I have heard that gel coat will not bond to epoxy well but again I will be using a mould where I will apply wet resin to the gel coat so I'm not sure what could be the issue here.

IF anyone could assist me in any way on making the right choice about resins I would greatly appreciate it. I am aware that the ploy resins are much cheaper than epoxy but I want a job well done and i am going to do much research about this project before i begin

 

To determine the resin you first need to decide on how you plan to use the boat, plus you need to decide on the type of fiber and your budget, these all play into the resin type.

There are a few gel coats that are compatible with epoxy, but they aren't going to be that easy to buy in a small amount, but they are available. You can't use standard gel coats because the chemistry isn't compatible.

If you want a low cost easy to build long lasting boat polyester is fine, it's what the vast majority of boats are made from. VE can be used in certain ways along with polyester or alone to improve the product, but unless you going to take advantage of the benefits it's not of much value.

Going to epoxy gives you more options to make a lighter boat, or one of the same weight with greater strength, this will be at a higher cost. But again, if you don't need these benefits it's not of much value.

 

This is for the construction of a 17 foot flats boat with 14 inch high sides that will be used for fishing the marsh and bayous of south Louisiana for redfish and specks. You could basically compare the look of it to a glades men flats boat or something similar. I won’t ever be jumping land or anything crazy like that with it and I want to keep it modestly light without sacrificing strength. I’ll take strength over light weight

With that being said, seems like I will use polyester, which is what I was hoping to be able to use in the first place due to its price tag but I will always take quality over saveing a buck. As for the fiber I currently have 75 feet of 6oz woven cloth that I purchased a while back before I was contemplating this project.

I am pretty sure that it would be wise you use other weights of fabrics in the build? Correct? Shouldn’t I use mat fiber as well as a base layer to laminate over the gel coat and in between layers of the woven fabric to achieve more strength.

Also would you suggest a minimum about of fiberglass layers to use in the construction of the hull ( I know this will depend on what glass I use) if you have any suggestions on what Mat / fabric / weight cloth to use I would love to here your suggestions.

 

To be honest the 6 oz cloth is almost worthless in this build, a layer of CSM against the gel coat and then something like 1708 or roving would be much better. You would use several layers, but the actual number of layers depends on the shape of the hull and if foam is going to be used.

Foam is frequently used to stiffen a hull, it really shouldn't be, but many builders use it that way, even some of the supposedly higher end builders that demand a higher price.

 

Forget that woven. Fairly useless for the hull if you ask me.

Upload a picture of the mould.

Someone can help you better then.

 

Ondarvr is your man on this one. Give him a picture of the mould.

Personally, I’d build with epoxy. The stink from polyester is really, really bad. If you are not building in your attached garage; you can get away with poly; otherwise, do yourself a favor.

I’d make a high impact bottom and line it with a core for buoyancy and to make it a bit lighter.

Probably something like bottom outside to in 1708,1808,1708,core,1708,1808; sides less by one 1708. But don’t use my guess as your schedule !!!!! People might get upset for posting an almost here, but just trying to get op away from 6 oz woven!

 

Ok so I’m NOT going to use the woven fabric. I wasn’t planning on using foam in the construction. The mold itself has to be resurfaced since the person I am getting it from spray painted the inside. Structurally it is in great shape and has no cracks or serious issues besides the paint. I plan to sand off the paint and get to the gel coat underneath then resurface it with DURATEC. The guy was using the mold at a boat to get to his duck blind but it weights about 400 pounds and is extremely solid. I figured since it’s structurally fine I could bring it back to life with a whole lot of time and elbow grease. What are your thoughts on this ? I know it looks very ugly in the picture but I’m going to resurface it. I read that I could either sand or sand blast the old paint out. It’s peeling off any way so it wouldn’t be very hard to get to the old surface

 

You can use paint stripper and a pressure washer, sometimes all you need is the pressure washer, this will leave the surface in good shape, or at least won't add to the surface defects.

 

I like the pressure washer idea! I’ve done that in the past with other projects and it works great. I really appreciate your help on my questions. When using polyester in a mold like this would you wait for the resin to cure before you added more fiber to the mold or could you continuously wet out the mat/roving while it’s still wet on top of each other

 

the downside of solid glass is it has no flotation

Downside of core is it isn’t as strong, but u don’t have much boat for flotation.

I’d use core to get it lighter and safer.

Looks like a fun project.

 

If it’s just a one-off deal, I’d just give the mold a scrub to get it clean and knock off the loose stuff, then coat liberally with PVA and gelcoat, and lay it up.
It will come out of the mold looking like hell, but The time and effort that you need to put into bringing the mold up to snuff might be better spent sanding on the piece itself, and easier and more ergonomic to work on.
Even though the mold is heavy, check it carefully before layup to determine if it has warped or deflected. You might need to build some exterior frames to hold it to its intended shape.

 

With that being said. Could I just not gel coat it and just paint in a layer of wet resin to start laying my fiberglass then once it’s all layed out and cured pop it out the mold, fair and paint over the bare resin hull and fiberglass ? Or would this cause an issue with it coming out of the mold not having the first laying being gelcoat. Of course I would coat it like you said with the Pva to have it come out the mold and not stick. The last thing I want is for me to spend all this time and money and it stick in the mold. That would suck big time. I feel like if I could take this rout and just paint it with awlgrip or something similar I would avoid stress cracks in the gel coat later down the road. And like you said I don’t plan on mass producing skiffs with this mold. This is just for me and I got lucky to get my hands on a decent mold

 

It's much easier to use gel coat in the mold even if you plan to paint it later.

 

Ok good advice. I will stick to the gel coat. I don’t mind having to either paint over it to make it a little shiny or sand it and buff it. I just might do this instead of spending so much time on the mold if it will realease without sticking

 

Yes, that’s why I said to coat liberally, probably two coats, as sanding gelcoat is much easier than sanding resin and fiberglass, and it doesn’t make you itch.
Once you get a feel for it, you can be pretty aggressive with a large softpad and get good results.
Multi coat the pva too, it’s cheap and water soluble, and you’re not going for an immaculate finish straight out of the mold. I use a garden sprayer for applying pva, and an old (clean) wetted out sock for small parts!