Epoxy over polyester?

[santa666]

I have a 1968 runabout I'm redoing. I've got ALL of the wood out of the transom and stringers...<br /><br />I am pretty certain it is a polyester an glass fabric boat...<br /><br />Can I use epoxy resin and glass fabric/mat to re-install a new transom and stringer/floor system? <br /><br />I understand about sanding/grinding to a "fresh" surface for bonding purposes, and want to protect the new marine grade plywood. I just want to make sure No water gets to the wood parts... <br /><br />I've heard that the polyester resins permit (eventual) water passage and DO NOT want that...

 

[CalicoKid]

Re: Epoxy over polyester?

Your boat is almost certainly polyester. Epoxy adheres to existing polyester probably better than more polyester would so you will be good with epoxy. Surface prep is the key to good adhesion. Water intrusion is via osmosis and will not be an issue with either resin unless you leave the boat in the water long term or let the rain and snow collect and sit inside the boat.

 

[fishingdan]

Re: Epoxy over polyester?

Yes, use epoxy. It is more expensive, but the lack of fumes alone is well worth it in my book.

 

[crab bait]

Re: Epoxy over polyester?

epoxy is best all around.. easy,strenght, rot protection, work time ( pot life ) ,all except cost.. <br /><br />one very important thing.. most cloth an mat are for poly resin only..<br /><br />MUST use the type for epoxy..

 

[santa666]

Re: Epoxy over polyester?

...Hmmm, that brings up a good question. This is to be strictly a trailer boat without mooring. <br /><br />Should I just go polyester and save the money? I've just reviewed the prices for marine grade plywood and HOLY-CR*P! Its $80-$110 a 4X8 $heet!<br /><br />Also I have 3/4 of a gallon of INTERLUX 2000e left over fron doing the big boats hull. Can I use this stuff in the bilge to prevent osmosis from the occasional dribbbles of rainwater and condensation? <br /><br />I am %100 on surface prep and have/use enough sanders and grinders for a battalion, so no prob there.

 

[BillP]

Re: Epoxy over polyester?

If cost is a factor do it in polyester and wet wipe the surface with styrene before glassing. It will work fine. Just make sure you prep well.<br /><br />IMHO epoxy isn't as user friendly in some respects as poly. With rare exception and a short term window, epoxy needs to be sanded between coats (poly laminating resin doesn't) and kick times cannot be dialed in to meet the exact work time. Any resin sitting too long on vertical surfaces sags, runs off and makes you baby the job until it kicks. Thickening it to prevent sag reduces strength or makes wet out impossible. Poly can be catalyzed to kick immediately after you finish glassing OR it can be hot coated to make it kick immediately. <br /><br />For the trade off to epoxy you get gluing, gap filling, flexibility and increased strength. Technically you can use thinner (+/- 35%) layups with epoxy to get the same strength as a poly layup.

 

[swimmin' for shore]

Re: Epoxy over polyester?

Santa, I think it's all a matter of what you want to spend, what you plan to do with your boat, and how you plan to store it. I don't use marine grade wood in my boats because it's just too expensive. I like pressure treated ply, personally, and it's 1/3 of the price. Is it as good? Absolutely not? Am I going to own this boat for the 10 years or more that it takes to tell the difference? Absolutely not. <br />For the average boater, pressure treated ply and polyester resin will work. I have a very inexpensive epoxy supplier, so I've done my boats in that, but if I had to pay 90 dollars a gallon and more for west system epoxies, it would never find it's way into my boat. In your case, I'd let your budget and planned usage be the deciding factor.

 

[santa666]

Re: Epoxy over polyester?

swimmin for shore- <br /><br />Since you use the cheep stuff could your name be more appropriate than just a nice online handle? I know, that was a cheap shot-What did you expect from SANTA666? <br /><br />Anyway, jokes aside I already have some marine grade plywood left over from a hardtop for my (bigger) offshore salmon trolling boat... Considering that stuff is SO good and SO expensive (comparatively speaking) I'd like to at least use up what I have and then try maybe to get some AB exterior (where?) Home depot, or MEANRADS!? <br /><br />So, I think polyester is my ticket and then an amalgation of marine grade and the AB with reinforcing fillets/gussets/tape, etc..<br /><br />Its a shame I don't have a 115 to hang on it (yet.) What do (you) people think of Mercury outboards? <br /><br />I go on Lake Michigan and want to be DOUBLY sure of my boat- 10 miles offshore is VERY far to have a hull malfunction. <br /><br />I am under a time crunch as I want to be down at Lake Michigan power plant here trolling for the FAT Browns in the warm water this January, (if I can get it straight just what I want to do...) <br /><br />Too bad I can't post pics here- got a 19.10 brown this summer...

 

[swimmin' for shore]

Re: Epoxy over polyester?

That's harsh, man. LOL. Let's hope and pray that it's just a name. Swimmin scares the fish, and I'm really against that.<br />You can get some AB at Home Depot, Menards, a local lumber yard. Cost-wise, it's probably cheapest at Menards. Both epoxy and polyester have temperature requirements for laying them, which you probably already know. If you're on a time crunch at this time of year in the midwest, you might want to look for a heated garage to work in. <br />Re: Merc outboards-check over in engines forums, but I suppose that the quality of Mercs has changed over the years, and you'll need to specify the year, model, etc...Those guys who frequent the engine forums are wizards.

 

[santa666]

Re: Epoxy over polyester?

Yeah, just kidding name wise...<br /><br />Ok, MEANRADS! it is... AB exterior grade pressure treated.<br /><br />Ok, I've heard good things MERC wise and will check the engine guru dudes over there. <br /><br />Thanks again.

 

[BillP]

Re: Epoxy over polyester?

santa666,<br />Prior to composites about 95% of glass boat builders used standard ac exterior ply in the floors and transons. If glassed properly it lasts forever. Now the better ones use pressure treated ply for floors, transoms and stringers and rot never happens. Don't sweat if not using marine ply.