Epoxy vs Polyester, what plywood?

[mckeemm]

Ok,<br /><br />I've spent the last two days reading and trying to understand the science of transom replacement. I gather it’s not impossible provided you are willing to put in the time. I have priced materials as best I could and I figure I can replace the transom and rotted floor stringers for $200-$300. Is this accurate?<br /><br />Question, I’m told that all these boats are built with polyester resin. So when repairing, do I use polyester or epoxy? Every second person I talk to has a different opinion. What brand?<br /><br />Plywood, These boats never had marine grade wood in the transoms and floors, still the plywood from 20 years ago was better than it is today. I stopped at the local lumberyard and asked what the difference between CDX and ACX plywood was. Blank stare! So there is not much help available there. What wood do I use?<br /><br />Any help is appreciated.<br /><br />70’s something 16’ Crestliner bowrider, $250 invested to date. Rated for 100hp<br /><br />Mark

 

[BillP]

Re: Epoxy vs Polyester, what plywood?

The Amercian Plywood Association has good info.<br /><br />apawood dot org.

 

[JB]

Re: Epoxy vs Polyester, what plywood?

Epoxy is a lot stronger than polyester but a lot more expensive, too. I favor epoxy for all repairs and polyester for things like sealing stringers and floors.<br /><br />For anything that needs structural strength you need to use Marine grade plywood and seal it well.<br /><br />There is no rule against rebuilding a boat better than it was originally built.<br /><br />Don't have a good picture of your leak holes. Is there wood behind them or are they only in the hull glass?

 

[ondarvr]

Re: Epoxy vs Polyester, what plywood?

Either way will work, it just depends on what you want to use, or feel better using. Epoxy is stronger and with epoxy it "might" last longer, but there's no way to know. Look at your boat and see what failed, was it the wood or was it the polyester resin, normally it's the wood. Even not knowing how to do it, you will be able to do a better job than they did when it was built new. You will be able take your time and pay attention to details like sealing the wood completely that are very important.

 

[Purduebarry]

Re: Epoxy vs Polyester, what plywood?

I did a key word search and found several specialty wood suppliers in my area. I spent around $40 for a 4x8' sheet of 1/2" Birch Marine AB Ply. They had AC which has a few more voids in the inner plys. I was suprised to find a few footballs in the ply but the owner of the company assured me this was the norm. <br /><br />As for the resin...I too went down this path and have decided to use Epoxy for the repairs and reseal of all floors. One point as made by another is only the wood was rotten. I might be sorry to be putting so much into sealing everything with Epoxy because the rot came from under the deck not above. I would use epoxy only because you are doing this on a transom and you only want to do it once and you certainly want it to be good and strong. <br /><br />The rule of thumb I've heard the most is Epoxy for structure and Poly for sealing. I've also been told directly from the manufacture that yes they build boats with Poly but thats when they are using a chopper gun, blasting the stuff into a mold, then gel coating the whole thing to make it look good. For my efforts it's Epoxy and I'm not looking back.

 

[JasonJ]

Re: Epoxy vs Polyester, what plywood?

You can use poly and get good results, its all in the prep. Epoxy rocks, and if you want to spend the green or can get some cheap, then epoxy is the way to go. <br /><br />That being said, when a boat is being built, most quality boat builders lay their hulls and structure. Chopperguns are generally used in the lower quality boats. What a good boat builder does is spray the gelcoat into the mold first, then they lay layers of cloth into the hull. There are a couple diferent ways this is done. The oldschool way is by hand, layer by layer until the layup is complete. The newer way is a male anf female mold. They put all the layers of cloth in, press the male plug into the female mold, and inject the poly resin. It gives a more consistant result from boat to boat this way. Then they glass in the stringers, or composite stringer grid, depending if they are going wood-free of not. Then the sole/upper section gets bonded to the hull, and they are done. <br /><br />In the end, if you gut your boat down to the hull, get everything dry, rough the surfaces, and clean with styrene or at least acetone, you will get a good strong result with poly that will be similar to production boat building. If someone tells you that they got a bad or weak result with poly, it is because they did not go through the proper steps for preperation. I did my entire rebuild with ploy, and the only regret I had was the stink. The respirator helped certainly, but it still smelled. Good luck...

 

[jesters420]

Re: Epoxy vs Polyester, what plywood?

just finished the stringers and floor used poly and it looks and feels solid as a rock. do you have a tap plastics around? that is where i got most of my materials. into it around $300 still need to paint the floor. good luck. there is a lot of information here, lots of great advice.

 

[mckeemm]

Re: Epoxy vs Polyester, what plywood?

Thanks Guys,<br /><br />I made the decision to bite the bullet and get started last night. I moved the boat into the garage and started ripping out the rest of the floor and the foam. I pulled about two thirds of the foam out and only about 20% of it was water logged. The stringers are only rotted in the aft six feet with the exception of the center stringer, which is completely done front to back. <br /><br />I plan to go to work and get the rub rails off on the weekend and hopefully get the gazillion staples out and take the top off.<br /><br />Around here no one knows what CDX and ACX plywood is, they never heard of it. They are recommending marine ply at $128.00 a sheet. The alternative is exterior grade fir at $50.00 a sheet. That’s where I’m leaning.<br /><br />Also, I may have jumped to conclusions when I said that the boat was a chopped glass construction. When taking a good look at the inside of the boat it's finished with a heavy roving on the last layer. <br /><br />Mark

 

[tashasdaddy]

Re: Epoxy vs Polyester, what plywood?

the fir will last as long as anything else. just be sure all sides and edges are sealed. the basic difference is the glue used to make the plywood. all wood when exposed to water will eventually rot. thats why you seal it.

 

[mckeemm]

Re: Epoxy vs Polyester, what plywood?

Here is a link to some pictures.<br /><br />http://pg.photos.yahoo.com/ph/mark_mckeeman/album?.dir=87c3re2&.src=ph&store=&prodid=&.done=http%3a//pg.photos.yahoo.com/ph/mark_mckeeman/my_photos%3furlhint=actn,del%253as,1%253af ,0

 

[JasonJ]

Re: Epoxy vs Polyester, what plywood?

Exterior grade should be fine. Thats all ACX or CDX is anyway. Don't know if you know, but all those letters mean is the quality of the finish and what grade is. For example, A means one side has a void free, smooth, finish. C means the other side is more rough, not as visually appealing, and X means Exterior grade. Same with CDX. My opinion is CDX is fine for structure and anything not visible. Its ugly, but the rough surfaces are better for bonding glass to. ACX is better when you have to actually see the wood.<br /><br />I am guessing the exterior grade wood your lumber yard has is probably ACX. You can just tell by the way it looks. Either way, as long as the wood is exterior grade, you are okay.

 

[Tail_Gunner]

Re: Epoxy vs Polyester, what plywood?

Flooring costs<br /><br />1. 3 sheets marine plywood $60.00x3 $180<br />2. West systems epoxy & hardener $75.00 x3 $225.<br />3. West systems fillers $30<br />4. Fiberglass tape and cloth $75<br />5. Good respriator $45.<br />6. 4 1/2 grinder and diamond blade $85<br />7. 3m 8609 $60.00<br />8. 8lb foam $300.00<br />-------------------------------------------------<br />Be careful....$1000.00<br /><br />Edit: $200 carpet...and on and on and on....

 

[mckeemm]

Re: Epoxy vs Polyester, what plywood?

Thanks all,<br /><br />I finally got to the bottom of the plywood debate. The American Plywood Association set the standard for plywood grading for American manufacturers. Guess who does it in Canada...The Canadian Plywood Association! The system is similar to the US and the common plywood grades are Exterior-unlimited outdoor exposure, Exposure 1- short term outdoor exposure and Exposure 2- indoor use only. I also found out that the exterior good one side fir uses the same glue as marine ply. Since all wood will rot and the glue is the same I'll use the fir at one quarter the cost of marine ply. <br /><br />I also think I'll use polyester resin for sealing and for the structural repair. That's what the rest of the boat is built with. I will take the time to clean and seal every piece of wood as well as the floors before installing.<br /><br />It will be better than new while keeping the cost reasonable.

 

[Purduebarry]

Re: Epoxy vs Polyester, what plywood?

How about some pics Mo?

 

[mckeemm]

Re: Epoxy vs Polyester, what plywood?

OK Guys,<br /><br />Here are some pics.<br /><br /> http://pg.photos.yahoo.com/ph/mark_mckeeman/album?.dir=87c3re2 <br /><br />I'm spending the next week or so getting the trailer fixed up and repaired so it will support the boat better for the rework. Right now it's flopping all over the place when I walk inside and I have a tire that goes flat every 2 days.<br /><br />I'll get the trailer tuned up and the bearings greesed and lights working just in case I find another "bargin" I need to pick up!