Epoxy or Poly

dolluper

Captain
Joined
Jul 19, 2004
Messages
3,906
Have started taking out the old transom and I was thinking of mat on the hull with poly and ply then mat and poly then ply ,fill any gaps with microballons and resin mixture Woven roving to sides and bottom of hull then final coat of mat and poly any thoughts if this would be alright or if epoxy is actually better
 

gspig

Chief Petty Officer
Joined
Jul 7, 2004
Messages
409
Re: Epoxy or Poly

There are as many ways to glue in a transom as people doing it. I used epoxy with filler to glue first layer of ply to the fiberglass skin. I used expoxy with filler to glue the second layer of ply to the first. I used polyresin with mat to fill gaps between the new transom and the hull sides. I used poly with cloth and covered the inside of the new transom.
 

BrettNC

Petty Officer 1st Class
Joined
Feb 6, 2005
Messages
298
Re: Epoxy or Poly

For most projects I use polyester, but on the transom I used epoxy since the transom is such a critical part of the boat.
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
Re: Epoxy or Poly

Epoxy is stronger, but it's normally the wood that fails in a transom, not the polyester laminate. Poly will be fine for the repair, use mat and roving, don't use cloth. If you are bonding 2 layers of plywood together, epoxy will be better, but it's not used in production by boat builders.
 

epresutti

Chief Petty Officer
Joined
Aug 14, 2001
Messages
465
Re: Epoxy or Poly

Dolluper,<br /><br />I used epoxy on my re-build, specifically in the transom and stringers (I replaced a lot of stuff). I was, and continue to be cautioned that once you use epoxy, you can not get a good bond to it with poly afterwards.<br /><br />The rule "seems" to be: epoxy to old poly good!, new poly to epoxy bad.<br /><br />I discovered I should not gelcoat my repair because of poor bonding and that I will need to use two part epoxy, or linear polyurethane (two part) paint.<br /><br />I am OK with all the restrictions with the epoxy, it is a stronger substance than the poly. Just beware of the limitations. There are many postings in this forum on it, including once of mine, subject : "epoxy paint"<br /><br />Hope this helps.<br /><br />Peace.<br /><br />emp.
 

dolluper

Captain
Joined
Jul 19, 2004
Messages
3,906
Re: Epoxy or Poly

Sort of looks like my mind is made up now with the kind thoughts it will be poly .I threw a floor in my old beater Cutter years ago and used poly and it's still ok [didn't have a clue what I was doing] but in need of a transom now too Thanks for the thoughts guy's :)
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,310
Re: Epoxy or Poly

There's No Doubt that your plan will work with Either Poly based resins,.. Or Epoxy.......<br /><br />But,......<br />There's also No Arguement that Epoxy Is Better..........
 

Terry H

Lieutenant Commander
Joined
Sep 25, 2001
Messages
1,862
Re: Epoxy or Poly

The argument Bondo is that if your time and money are worthless than epoxy has the edge. I can do in a day with poly what it will take you a week or more to do with epoxy. I will spend a fraction what you do, and all the materials for my layup are available locally. And, if I am trying to match a gel coat finish I can do so with gel coat and make a flawless repair, no matter what size. Not trying to be argumentative so much as informative. Chief ;)
 

MercMark

Petty Officer 2nd Class
Joined
May 20, 2003
Messages
149
Re: Epoxy or Poly

Originally posted by Chief 101:<br /> The argument Bondo is that if your time and money are worthless than epoxy has the edge. I can do in a day with poly what it will take you a week or more to do with epoxy. I will spend a fraction what you do, and all the materials for my layup are available locally. And, if I am trying to match a gel coat finish I can do so with gel coat and make a flawless repair, no matter what size. Not trying to be argumentative so much as informative. Chief ;)
why the delay?<br /><br />If you laminate while the first layer is still early in the gel state, the layers will bond chemically still.<br /><br />I hope I didn't miss something. My epoxy work is done and looks fine.
 

JasonJ

Rear Admiral
Joined
Aug 20, 2001
Messages
4,163
Re: Epoxy or Poly

Like Chief said, epoxy is great if the wallet is bottomless, but epoxy is not necessary. When you rebuild your boat with poly, you are doing it the same way the manufacturer assembled it. That hull shell is cured when they glass the transom, stringers, and floor in. The secondary bond with poly is the same in that new boat as it will be with your rebuild, so you do not have to worry about strength issues as long as your resin is mixed properly and you have an acceptable amount of layers in your layup. I have never quite understood the "poly is not waterproof" arguement, considering gelcoat is basically tinted polyester resin, or is there some secret ingredient in gelcoat? That would be handy info to have....
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
Re: Epoxy or Poly

Chief, JasonJ<br /><br />You guys understand it, epoxy is great stuff, but it's just not needed in most repairs. There are times when it should be used, but there is a reason that almost no boats are made with it, the cost, health concerns and hassles aren't worth the bennefits most of the time. The reason that transoms and stringers fail is not related to the polyester resin, its how the boat was built to begin with. It was made by an under paid guy that really only cares about how much beer his paycheck will get him on Friday, and was never trained well enough to know that resin and glass needed to cover the entire piece of plywood. It would have rotted out in the same amount of time even if it was made with epoxy. Plus the boats would cost more than double what they do now.<br /> <br />If it was the poly that failed, you have boats out there with good plywood in the transom and it would only need to have the fiberglass replaced, how many posts have seen with that problem. Even when the wood in the transom is just pulp, the poly holds it together fairly well. To get the most out of epoxy, fibers other than glass, or higher grades of glass need to be used, plus it needs to be well engineered. Most of the short commings of poly are exaggerated and so are the benefits of epoxy.<br /><br />I don't hate epoxy, but I only use it when its needed.<br /><br />Sorry if this sounds like a rant, I hope I didn't offend anybody, that was not my intention.
 

cc lancer

Petty Officer 1st Class
Joined
Aug 23, 2004
Messages
371
Re: Epoxy or Poly

Most of the short commings of poly are exaggerated and so are the benefits of epoxy.<br /><br />I don't hate epoxy, but I only use it when its needed.<br /><br />Facts don't offend when some one speaks the truth. :)
 
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