How to make a hull in epoxy and fiberglass only from a mold — no vacuum

Boat about 100 ft from me built with polyester that's from 72'. No blisters in a pretty tough life, gel coat got a face lift about 5 years ago. Done right it's outlived several owners.

Vinylester boat from early 80s, just got an awlgrip face lift as it was mighty haggard looking. All in all pretty good run for 40 plus years.

Know of one epoxy boat, from 1997 that seems to be doing just fine.

Well designed boat for either of the three materials should outlast most reading this....

 

Thank you for your contribution.

Do you mean you actually touch the gel coat only one time since 1972?
What is «done right»?
(We are speaking about cruisers, sea going sailboat right? — I need to check now…)

I didn’t witness so far gelcoat without damages such as cracks or chips…
But as you do some says polyester and gel coat can be very durable while most says one have to polish the whole boat and re-gelcoat regularly, I heard every 2~3 years.

 

Commercial boat, hard life but weaker northern sun.

Waxing is rather often, re gelcoating is probably measured in decades.

Everything cracks or chips if hit hard enough.

 

Good to know.
Problem with crack in gel coat on polyester — and I guess also on vinylester on some extend is osmosis… critical not just esthetic.

 

You have your resin basics a bit off.

You said epoxy is a rather generic term because there are so many formulas. It's exactly the same for polyester and VE, only to a much greater extent. The problem hulls with blisters and such are typically done with the cheapest resins that weren't designed for marine use, or not used correctly by the members of the untrained minimum wage crew that happened to show up that day.

The polyester not being waterproof thing is something that gets passed around quite a bit. Well, nothing is waterproof, there are just varying degrees of water resistance, epoxy absorbs water too, just not as much. And if you used junk epoxy and mixed it poorly, then had it built by the same untrained crew, it would fail in the same way as some Polyester boats did.

Gel coat doesn't just fail and need to be reapplied every 3-5 years. Again, when done correctly, you have many decades before it may need more than basic attention. Hit something hard and you may need to repair it, but that's not difficult. Plus if in the future if it needs a total face lift, it can easily be painted. And gel coat does not protect the polyester from water, gel coat isn't waterproof in that way, water will migrate through it over time, and that time frame is shorter than you may think, it happens with all materials.

There can be advantages in using a particular resin over another, but the laminate schedule and entire design needs to be engineered to take advantage of what that resin can offer, just using a "better" resin doesn't automatically mean you get a "better" boat.

And as you mentioned, with epoxy you aren't going to get those great physical properties listed on the data sheet without it being post cured. The physical properties will be lower, sometimes significantly. You need to do some research to understand the exact epoxy and hardener system you're going to use, and it's the same for any of the resin types.

 

No, water will reach the resin (laminate) eventually whether it's cracked or not, it makes little difference. The thing that makes the difference is using an actual marine grade polyester or VE resin in the correct way.

 

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Listening isn't your strong suit. Your posts have monologue, rather than conversational, vibes.

Where do you get the idea that all epoxy needs to be post cured? Why isn't vinylester more popular with home builders?

 

«gel coat isn't waterproof (…), water will migrate through it over time, and that time frame is shorter than you may think»

Ondarvr wouldn’t it be precisely the reason why I heard some redo their gel coat every 3 years or so that is to re-waterproof the hull?
Despite that it is still looking good except for the chips that happen all the time anyway.

You seems to say that new polyester is more waterproof that it use to be. Is that correct?

 

Nobody is changing out gel coat every 3 years, scratch that no sane person is re upping gel coat every 3 years.

Usually the issue was absorbing water in the form of blisters. Modern marine specific resins have largely relegated that to the history books. Trying to remember the last blister I saw ground out... been a while.

Epoxy barrier on a poly or vinylester hull is very popular up here. We wax whenever we think to do it or have time and repair chips as needed.

 

No, I have never in 55 years in the industry, more than 30 of it doing tech service, product development, sales, and doing training globally for resin and gel coat, have ever heard of someone applying new gel coat every 3 years.

Water migrates through everything, gel coat is just one of those things. The chemistry of marine grade products are designed to handle the absorption.

These products are tested, a laminate is made to a certain spec, cut into sections, weighed precisely, then immersed in water for various lengths of time. Each piece is weighed again at certain time intervals to determine water absorption. The same is done with epoxy to measure the water absorption.

These pieces are also tested for physical properties before and after water immersion, plus any cosmetic changes.

Many decades ago the boat builders used resins that weren't tested thoroughly, but were very low in cost, which occasionally caused huge problems years later. And sometimes it was just the poorly trained crew using equipment they didn't understand to build boats and yachts. Both scenarios can end up being the cause of blisters, plus other problems.

As time went on the better builders improved their methods and the materials being used, and used better trained employees. This resulted in blisters and other problems being reduced significantly. Some trailer boats don't get all the best materials because they typically spend very little time in the water, so they occasionally do have problems if left at the dock all year.

If you are planning to use epoxy, the entire boat needs to be designed and engineered to take advantage of its properties. Just substituting epoxy for polyester or VE doesn't do much other than significantly increase the cost and hassle.

Any of these resins can be used to build a boat of similar strength, epoxy allows you to achieve that strength at a lower weight. And possibly significantly lower depending on the fibers chosen and the methods used to build it. But the costs skyrocket as you reduce weight.

Many, maybe even most, boats don't need to be as light as possible, the weight can help a bit. That is unless it's for competition use, then comfort and durability get moved down on the list of priorities.

On boats that are going to spend a significant amount of time in the water it's normal to apply a bottom paint, at that time an epoxy barrier coat is typically applied because it's an easy step to take to help insure you don't get blisters. But again, the likelihood of getting blisters on a hull made with marine grade products is far less of a problem.

 

Thank you for al this informations.
I’m surprised about it because so far I heard that waterproof qualities of polyester and vinylester is at molecular level.
Therefore it obviously mean that more recent resin got combined with additives.

My idea was more «if you need 1 inch of polyester resin to get the same strength of few millimeter of epoxy rein… what strength of 1 inch epoxy will achieve!»
I know it is actually about the quantity of fibers in the composite but you get the idea.

I’m interested to understand what change in design would need to take a boat made out of epoxy for engineering reasons.
If you know some source that explain that I will read / watch it.

I come back to the boat made in 1997 Comfisherman speak about. Is it a sandwich construction or a simple (monolithic) one?

 

It was panel built, almost like a metal boat. Looks alright, not molded smooth but good enough for its use. At today's prices, doubtful it would be built with epoxy now.

I'm new to glass boats, but jumped in with both feet. Got a lot of advice from a lot of folks, some good... most not. This week's order for may was drum (s) of resin, pallet of combi and case or two of core. I read and reference whatever ondarvr posts, his advice has absolutely checked out.

 

Nothing has really changed in the chemistry of any of these resins types in many decades, it's well know and been has around for a long time. The changes were in which resins the builders started using, they switched to actual marine grade formulations and better techniques.

If you want to better understand how a laminate schedule changes with resin and fiber type, you need to consult with a composites engineer with experience in the marine industry. I only know the resin and gel coat end of it well enough to go into great detail.

 

Comfisherman I’m glad you brought an example of a boat made out of epoxy (and obviously fiberglass — you would have precised if it was made with carbon fiber).
It has been done and so far it is fine, as you said.

Ondavr I though you were speaking of boat design (her hull and reinforcements design) that change depending of using epoxy rather than polyester.
Not simply about laminate schedule differences between polyester and epoxy.

 

It was built by a guy who at the time had 25 years plus of composites. Don't know who did the engineering.

I'm standing in a yard typing this that's 40+ acres of boats that are probably 85% frp. So let's call it 400 glass boats, of which 399 are polyester or vinylester maybe a couple other are epoxy but I'm unaware of them.

Point is, you can make a good Boat from all of it if designed for each material. No one material is a blanket panacea.

My application has absolutely no benefit for epoxy.

A buddy builds race canoes, he's trying to save ozs. Carbon and epoxy fits his end goal well.

Pick the design and requirements, then select material.