Use Of Polyester Resin On Wood - Don't Do It

[18rabbit]

Thom - Like you, I won’t mess with polyester resin, either...only epoxy.<br /><br />Btw, 15-in hg (mercury) is 1/2 bar (atmosphere), equivalent to about 7.35psi of pressure. 30-in of hg is an absolute vacuum having an external atmospheric pressure of 14.7psi on all surfaces. There is nothing beyond 30”hg (absolute vacuum). The 1000psi mentioned must be the total pressure over the solid surface area (total about 1sq ft), not the pressure on the (fluid) resin. The polyester resin would have cured with about 7.35psi on it.

 

[ThomWV]

Use Of Polyester Resin On Wood - Don't Do It

I have been telling people not to use polyester resin for laminating wood for quite some time now. I won't even buy the stuff anymore myself but that's just me. I ran across this posting on the Florida Sportsman web page this morning and I really thought it would be of value to some of you guys. This fellows observation confirms my own experience. Here is what he had to say:<br /><br />"I remember a thread about poly resin and it bonding (or not) to wood awhile ago, so thought I'd post some observations from this weekend.<br />I was molding some parts for my Corvette over the weekend, and since the rest of the body is polyester I was using poly for these parts. It was the first time I'd vacuum bagged with poly. I used a wood form, and being a little lazy just used a barrier layer of bag film instead of the normal sealing and waxing of the form. I didn't make the bag film sheet quite large enough, and with the pressure from the bagging some resin creeped beyond the film to the uncovered part of the wood form and into the breather. After I separated the parts (when cured) I thought I'd see if I could get the extra resin off before making the next part, and much to my surprise it pulled loose easily by hand. I know from prior uses that getting epoxy off non-waxed areas is impossible. I was really quite surprised that the poly had made "no" bond to the wood form at all, not even under 15 inches of vacuum pressure (about 1000 psi).<br /><br />-Greg"<br /><br />Greg's experince with this cheap resin is consistant with my own. I have tried all manner of prep for the wood, different brands of polyester resin, thinned and not thinned, fast or slow setting (as a function of hardner ratio) all to no good effect. If you put this stuff on wood it will come off, no question about it. Do you want that for your own project boat? Not me.<br /><br />Thom

 

[lawyertob]

Re: Use Of Polyester Resin On Wood - Don't Do It

Originally posted by ThomWV:<br /> . . . . If you put this stuff on wood it will come off, no question about it. . . .

ThomWV,<br /><br /> I keep reading that poly resin won't stick to wood...but I had to use a chisel to get the stuff loose from my old deck and old transom. How is it that Glastron was able to get the stuff to stick in 1976 but we can't get it to stick today?<br /><br />I will admit that I have very little experience with fiberglass. However, I do have experience using a chisel to try to break the old glass loose on my boat. I can't tell for sure what kind of resin they used, it looks just like plain old green fiberglass to me; however, I really doubt if Glastron was mass producing boats with epoxy resin.<br /><br />I'm not trying to argue with you, I am just trying to determine why some people keep saying that poly resin is useless with wood...while others say it works fine. I mean either the stuff works or it doesn't, so why do we get stories both ways.<br /><br />I guess for me it is akin to a situation where someone tells me over and over that soldering an electrical connection won't hold the wires together. I know from experience that solder will hold them together if properly done. Some people can't get solder to stick, but that is from them heating the solder and not the wire...not the solder's fault. To continue the analogy, I would agree that crimp and solder is BETTER (epoxy) but twist and solder (poly) should hold just fine. And for the record, I think your crimp and solder method in the other thread is great and will use it on my own boat.<br /><br />Just my $0.02 worth,<br />Joe

 

[G DANE]

Re: Use Of Polyester Resin On Wood - Don't Do It

I am almost sorry too, having experienced the opporsite. However polyester will only stick to wood as long as there is so much of it that it isnt all absorbed by the wood. Therefore polyester will bond much better to wood if you lay one or two layers of mat on the wood. Try following: Glue 2 layers of wood together with poly - joint will be weak. Try to glue 2 layers of wood with a couple of layers of mat between. It will give a strong bond. I never tried epoxy, might be far better.

 

[snapperbait]

Re: Use Of Polyester Resin On Wood - Don't Do It

"If you put this stuff on wood it will come off, no question about it."<br /><br />Hogwash....

 

[JasonJ]

Re: Use Of Polyester Resin On Wood - Don't Do It

This is definately a case of "it depends". Proper usage and lamination techniques with wood and poly are far different than just getting some on wood and seeing if it comes off. I can attest from my own experiences that the recommendation of not using poly on wood is a poor recommendation. <br /><br />Just on my own project, I once made the mistake of setting a resin bucket on a scrap piece of ply. Next day, just for the sake of arguement, I tried to get it off. Just the residue that had ran down the sides to the bottom of the bucket created a bond strong enough where I had to literally destroy the bucket, and still never got the poly off of the wood. Improperly applied epoxy will come off as well. <br /><br />It is when you use enough resin to allow it to saturate into the wood fibers that you achieve a more than adequate bond. Sometimes I wonder if poly nay sayers just cling to epoxy as a crutch, through heresay or a lack of first hand experience with poly. Epoxy is good stuff, I love it myself, but proper application of poly will yield a safe, strong end result. Maybe all the poly nay sayers sell epoxy products...

 

[BillP]

Re: Use Of Polyester Resin On Wood - Don't Do It

I've pulled, yanked, chiseled, sanded, grinded, etc. enough poly off wood to experience how well it sticks. Those who have pulled a few transoms, floors and stringers out of old glass boats know this too. <br /><br />No offense to "Greg" but his empiracle "test" wasn't done right. If applied correctly it peels the wood off with it, just like epoxy does. If prepped and applied right it sticks...thinning to penetrate the fibers is a key factor for success. Sometimes I "peck" the surfaces with an ice pick type tool and then flood the surface with acetone to dry it out. After that comes the poly...but I rarely use poly without glass no matter what the application. Of course it isn't a glue like epoxy and isn't as strong so greater care has to be taken...as does the wood selection.

 

[jimmythekid]

Re: Use Of Polyester Resin On Wood - Don't Do It

ok heres what happened to me, if you can see in my pics in pics 3-4 you can see the big square spot with a stripe in the middle where there is no glass yet, this is where my gas tank goes. I f____ed up and measured 1/2 too short, gas tank wouldn't fit. I used 5 ply 1/2 plywood in that section. Keeping in mind that the only "prep" I did to the wood was to apply POLY resin thinned to rubbing alcohol consistancy with STYRENE NOT ACETONE applied with two applications with 12 hours in between each one, on all surfaces.Then glassed in in the usuall manner. When I went to remove the plywood to make room for the tank I discovered the thinned POLY resin with STYRENE soaked into the outermost ply and partially into the next. The wood actually ripped apart from itself before the THINNED POLY resin with STYRENE even came close to coming off the wood. If you give the wood a chance to soak up some resin before glassing in, trust me it will not just peel off without ripping the wood apart. I was told by an old timer in the boat business that poly gets its bad rep from improper application. (not letting the wood soak it up first before glassing in) and thinning it with acetone instead of styrene. I am no expert by any means, I just know that I measured wrong and getting it to come out was a real pain in the u know what. However this is only three weeks since I glassed in the section I am refering to, Don't know if it will hold up over time. although this boat is twenty years old, and the little wood that was still good that i tore out was sticking to the original POLY resin pretty well. How can POLY resin not be good if thats what they used to build the stupid thing and it lasted 20 years? I have pics to post illistrating this minor mishap however I have to use my sisters computer to do so, I don't know how to from my computer yet as I have just switched to Linux and am still trying to figure it out give me a couple days and should have them posted.

 

[lark2004]

Re: Use Of Polyester Resin On Wood - Don't Do It

I wouldn't say that polyester is 'Bad', but epoxy is (from my experiance) better. I have done considerable work with both, and find that sometimes it is preferable to use one rather than the other, but more often than not, the epoxy is the resin of choice.

 

[jimmythekid]

Re: Use Of Polyester Resin On Wood - Don't Do It

in sarasota there is a place where a customer of mine got POLY for 73.00 for 5 gallons, the same place EPOXY is 68.00 per gallon no brand names specified, I forgot the name, as I am done buying resin, I will try to find out the name of the place and pass it on.

 

[Terry H]

Re: Use Of Polyester Resin On Wood - Don't Do It

I'm gonna side with the pro-poly group. I use both poly and epoxy, tho the first time with the poly was 45years ago. Poly don't stick to all that epoxy does, but if you want to encapsulate wood, just thin the first coat then start glassin'. I think someone already said that. Epoxy is good for the amature because it sticks to most anything well, but takes a long time to cure. It will work even if you make some errors.<br />just a thought

 

[prockvoan]

Re: Use Of Polyester Resin On Wood - Don't Do It

The cost of epoxie resins around here is more the 50% more then poly resins.I used both.I would use epoxie over poly but not when it comes down to doing wood.Don't like the bluing,and having to wash in between coats.I find that I have been able to use poly resins in 35 drg weather,one thing I haven't tryed with epoxie.Thank God it doesn't get that cold here but once in a blue moon.

 

[cc lancer]

Re: Use Of Polyester Resin On Wood - Don't Do It

Shame on you Jimmythekid:<br /><br />You have now let out the secret that Chris Craft figured out in 1965. Thin with styrene cut back on the MEKP, and poly will soak into the wood.<br /><br />Look at the ten of thousands of boats that have been built before epoxy became the buzz word. And the stringers are still encapsulated.<br /><br />Epoxy is more forgiving than poly like Chief 101 said.

 

[crab bait]

Re: Use Of Polyester Resin On Wood - Don't Do It

an look at all the rot....

 

[lark2004]

Re: Use Of Polyester Resin On Wood - Don't Do It

most of the time the rot has been caused by someone drilling holes for brackets etc.. and not sealing them properly, and by some manufacturers being cheap or lazy (not sure which) and not sealing the bottom of the floor.

 

[Terry H]

Re: Use Of Polyester Resin On Wood - Don't Do It

Sounds like you got it figgered out lark.

 

[jimmythekid]

Re: Use Of Polyester Resin On Wood - Don't Do It

that funny cc lancer that old timer I refered to worked at the Chris Craft factory right here in Bradenton Fl for 32 years Ironic

 

[a_bullfrog_a]

Re: Use Of Polyester Resin On Wood - Don't Do It

also to help poly stick to wood drill multiple <br />small holes maybe halfway thru the wood. This <br />should create mini anchors points, kind of like <br />rebarb in cement.

 

[JasonB]

Re: Use Of Polyester Resin On Wood - Don't Do It

I have similar thoughts as Joe. When I gutted/redid one of my '76 Glastrons, there was no problem with Poly's adhesion to wood - at leat where there was good wood left. I will also agree that the bond between two pieces of wood is better if there is mat/cloth involved. I used 5-6 gal of poly replacing the stringers, transom, and floor in that boat and they are solid. I pretty much soaked all the wood in poly to hopefully help keep it dry. I think Epoxy is probably better, but for my projects so far, poly has done what I needed to do and I have no qualms about its adhesion.