The Epoxy Manifesto

[JasonJ]

Re: The Epoxy Manifesto

Actually, I love epoxy, but my bank account preferred poly when I did my project. I would use poly again in a heartbeat, because it works well when properly applied. I will also say that epoxy is better, and easier to deal with. I use epoxy on all my small jobs. <br /><br />My next project will be an aluminum hull so I won't have to deal with with any of it except to seal ply floor sections...

 

[jessgonz33]

Re: The Epoxy Manifesto

Concerning the resins:<br />1. Epoxy : Best, completly waterproof, most strength<br />2. vinyl ester resins : better, waterproof, stronger than polyester<br />3. Polyester: Somewhat brittle and NOT waterproof. Weakest of all three.<br /><br />I like West System the best. Have used it in marine environment for 20 years. It stretches and will take an impact better. The main drawback to polyester is that water vapor will penetrate the resin. No so with epoxy or vinyl easter. Vinyl ester is probably the most cost effective for large projects.<br /><br />Jess

 

[rayiow]

Re: The Epoxy Manifesto

now i am totally confused....you all say a big no no to gel-coat sticking to resin yet i get all my resin and gel-coat from a boat builder who make 50ft+ catamarans and the basis is gel-coat in mould then resin and fibreglass matting over top.am i missing something here?,i am not questioning you guys just voicing my now confusion,this resin is blue before hardener is added.

 

[Ralph 123]

Re: The Epoxy Manifesto

Don Casey Tip #29 <br /><br />Polyester or Epoxy Resin? <br /><br />What kind of resin you should select depends on the job you are doing. Polyester resin is excellent for fiberglass lay-up--building a boat, for example—but it is less ideal for repair work. Polyester laminating resin doesn’t fully cure while exposed to air, so when it is used for lay-up, every application joins to the previous one on a molecular level. You end up with what is essentially a single substance encapsulating multiple layers of glass fabric. <br /><br />When you are doing a repair, you need for the resin to also function as an adhesive—gluing the patch to the surrounding surface. Polyester is not very good at this. Epoxy resin, on the other hand, is a first-rate adhesive. Because of this, as a general rule you should use epoxy resin for all repair work. <br /><br />The exception is when the repair will be finished with gelcoat. Epoxy adheres tenaciously to cured polyester but the reverse is not true. The bond between an epoxy repair and an overcoat of polyester gelcoat will not be strong. Use polyester for repairs that will be gelcoated. Cost can also be a consideration. Epoxy is three to five times more expensive than polyester. This is relatively insignificant for a small repair, but where the damaged area is large, using polyester resin significantly lowers the cost of the repair. <br /><br />Grinding (sanding) is essential regardless of which resin you choose, but if, for reasons of cost, you elect to make your repair with polyester resin, it is imperative to grind the repair area especially heavily. First wipe the surface thoroughly with a dewaxing solvent, then use a 36-grit disk to grind everywhere you want the resin to adhere. Heavy grinding can somewhat offset polyester’s weaker adhesion. <br /><br /> http://www.boatus.com/boattech/TipResins.htm

 

[rayiow]

Re: The Epoxy Manifesto

thankyou ralph i understand it alot more now,sorry if i sounded abit thick.

 

[cc lancer]

Re: The Epoxy Manifesto

rayisleowight:<br /><br />There is 10 million boats in the US. So lets say there is 9 million that are made with polyester resin, and being liberal, very liberal, that there are 1 million made with epoxy.<br /><br />As a logical person, do you think these 9 million are subject to sink at any moment, because they were manufactured with polyester resin?<br /><br />So what does your friend, who builds 50 foot catamarans say? Since a cat has more stresses on the hull than any other type of hull?

 

[BillP]

Re: The Epoxy Manifesto

Here's my slant on poly and epoxy... <br />Poly is easier to work with because you can adjust the kick time to each job. It isn't sensitive to hardener ratios. That means you don't have resin running off verticals like stringers and making a dry laminate. You can followup immediately after glassing with a "hot" coat to kick the job off. Poly is not a glue or gap filler so prep and fit of parts need to be more accurate. Poly comes in "laminating" or "finishing" types. Laminating stays tacky and lets you glass days or weeks later without sanding. Finishing resin requires sanding after it kicks if more glass is applied later. Wiping down with styrene before glassing makes a chemical bond superior to wiping with acetone. Poly is cheaper and there is more selection in mat weights. Water intrusion on trailer boats doesn't happen so worrying about it with poly is a waste of the mind.<br /><br />Epoxy is less user friendly to me for glassing but more friendly in the prep arena. It's holding power makes up for those places that are difficult to prep...such as between the weaves in woven roven. Epoxy has to mixed exactly or it suffers strenth. This also means you are at the mercy of whatever temps and humidity do for kicking time. Kick times can be somewhat adjusted by using different hardners but they still lock you in to the temps and humidity factors. This makes you stay with the job and nurse resin while it drains off vertical surfaces (like stringers). It can be thickened but that doesn't make the problem go away very much. Most epoxies need sanding if additional glass is added later. Some mfgs claim not to need sanding but I've not tried them and they are far a few between. Epoxy will not wet out the same mat used for polyester resin. If you try it will result in a dry and weak lamination. There is a special mat for epoxy use. The additional strength of epoxy means you can reduce the lamination shedule by xx%. Industry used to say 35% but I don't know what it is now. That can offset cost and labor somewhat when compared to polyester.<br /><br />Bottom line to me is to use polyester where I don't need the superior gluing and gap filling factors of epoxy.

 

[craze1cars]

Re: The Epoxy Manifesto

Count me as a big fan of Raka, Inc. <br /><br />Buy it, you'll like it. <br /><br />Hardly any fumes at all...just a slight "peanut butter" odor that fades quickly. Easy to work with, predictable and consistent, reasonable price, great personal customer service, shipped right to your door. Not available in your local store...

 

[geekomatic]

Re: The Epoxy Manifesto

Hmmm.Interesting posts for the last few days.I actually have begun to experiment with the smelly poly stuff a little more.Not on my boat of course.Got a canoe that needed a little work.<br />Lieutenant Bill and Admiral Ralph, You both have great points.The poly stuff never seems to harden, nor does the smell ever seem to go away.I can add layer upon layer of this stuff and it appears to all "become one with itself" but it stays tacky.Now, what I did was go back and add a liberal layer of epoxy resin with fabric on top of the poly.My objective was to build up the floor of the canoe and get rid of that uncomfortable "dip" when I stand up in the thing when it's floating.Looks like it cured hard as a rock,but it's also quite flexible.The stench has vanished as well.Works like a charm and the great part is that I did it outside with a stiff breeze going. The little Coleman Scanoe (ever heard of one?) now seems to be solid as a rock.I actually feel comfortable standing up in the thing to take a river-whizz while I cull the trout herd.On a very satisfying side note: While laying down the final layer of fairing epoxy, It seems that fourteen unlucky mosquitoes (Yes, I counted) became trapped in the final layer.It reminds me of ancient prehistoric ants that were trapped in amber.They look pretty cool, so I'm gonna leave 'em.Besides, I really hate those little *******s.