Pressure treated lumber / Fiberglass Resin?

[Don W]

I am hoping to start replacing some decking on the side of the cabin on my 65 Chris Cavalier 30. The decking will be covered with fiberglass mat and resin like it was originally. Does anyone know if there is a problem between the chemicals in pressure treated lumber and the chemicals in the epoxy resin. I am looking to use pressure treated because it is inexpensive, the wood will not be seen when finished, it lasts forever and it the exact thickness I need. Thanks in advance. :D :confused:

[imported_Dutch]

Dan-

it will be fine as long as the pt lumber is well dried out before attempting to epoxy glass over it. a moisture meter may be a good investment. another old trick is to use two layers of .75 oz mat instead of one layer of 1.5 oz mat. put down the first layer and let it kick. then mechanically fasten it every 6 inches or so with ss screws lightly countersunk. then glass over that with the other .75 oz piece.

by the way. I dont know what your layup schedule is- I was guessing at a single mat but that sounds a bit light- you would probably be better off with 2 x 1.5 oz

[ 10-10-2004, 09:40 AM: Message edited by: Dutch ]

[Buddy]

Search the posts here and you'll find that mat is not a product to use with epoxy. The starchy binder that holds it together softens in polyester resin (styrene) but epoxy won't wet it out and it doesn't drape well. No need of mat in an epoxy layup- it is used between fabric layers in a polyester layup becuase of the poor adhesive qualities of polyester. "Correct" construction for a fiberglass, dynel or xynole fabric deck over plywood is epoxy. And yes dry PT works well with epoxy.

[Jim Mathieson]

There are biax fiberglass cloths with mat on them that are made for epoxy and ones that are as you describe that are made for polyester only.
For example Gougeons make a West sys fiberglass with mat backing.
I've used a whole roll on my Cat project and found it better for draping over a long tapered curved surface like the lower hulls. Richard Woods ,the designer of my 32.5 ft Cat recommends using 17 oz biaxial glass with mat backing with epoxy .It's easier to handle ,or mishandle ,tug on and pull especially for us amateurs.

[ 10-11-2004, 06:31 PM: Message edited by: Jim Mathieson ]

[Frank Wentzel]

I question the commonly held belief that epoxy will not wet glass mat. I used glass mat on a redecking I did on my sharpie. The mat went transparent just as fast as cloth which I take as a strong indication that I got a thorough wet-out. I did that about 20 years ago using old style high viscosity epoxy (Epon 828 with Versamid 140). If there was a wet-out problem it certainly would have shown up by now. It's funny what you can get away with when you don't know something can't be done!

/// Frank ///

[Bob Cleek]

Oh for Pete's sake, guys! There is NO place for PTF on a boat. Simple as that. I don't give a good gottdamn whether somebody's done it before or not. First, it is NOT pressure treated all the way through. It is about the quickest rotting stuff around once you get past the treating chemicals. (EG: the cut edges, unless you are going to pressure treat that too.) It is fencepost material. Cheap, bioengineered wood grown fast for the use intended... which ain't boats. It also stinks and despite the fact that epoxy will stick to just about anything, the chemicals in it can't help adhesion much.

The proper, and the easiest, repair is to replace what the people who built the boat used in the first place. You should have no problem obtaining it. Your boat will thank you for it and the repair will be done right.

Sheesh... pressure treated fir... advice almost as bad as telling a guy who has a tree growing on his place that he can make a decent spar out of it. Maybe I'll start a thread about making your own nails!

[bainbridgeisland]

I would stay away from epoxy-glassing treated timber if you can. There are some pitfalls.

Some testing has been done on glassed, CCA-treated timber. Multiple samples of epoxy-glassed CCA-treated timber were tested before and after aging. The glass wrapped timber always gave superior performance, both before and after aging.

However, a hydroxy-methylated resorcinol coupling agent was used to alter the surface chemistry of the wood so the epoxy would stick better. So you may not get the same performance. The fact that they were testing coupling agents suggests that performance was less than satisfactory.

This was work done for the West Virginia Department of Transportation to improve the life of timber guard rails. The information is from a paper: Evaluation of Mechanical Properties of Glass Fiber Wrapped CCA-Treated Wood Coupons" from the Society for Advancement of Material and Process Engineering, 46th symposium, by Anegunta, Gupta and GangaRao.

[Oyvind Snibsoer]

Just to second Cleek (as if he needs seconding...) PT lumber is low grade lumber. High quality lumber can't be pressure treated, since the chemicals are unable to penetrate the denser wood.

[MarkC]

Make your own nails! smile.gif

I have seen that done - easy :cool: - cut up scrap steel from an old car pannel (for example) with heavy snips. Heat the piece of steel till red-hot with a propane torch or on barbeque hot-rocks, then hammer the red-hot steel on an anvil or piece of heavy steel, folding the steel over on itself, then turning one end over making a nail-head and tapering and flattening the opposite end with the hammer.

As to pressure treated wood - there is an article in Woodenboat 164 Feb 2002 p. 12 Richard Jagels 'Thwarting Rot - Safely' which discuses this (eg. 'pressure treatments using waterborne chemicals' and Fixed Salts / Safer Salts and the Ethylene glycol / Propylene glycol / borate discussion also.

[PeterSibley]

Buy untreated timber, cut ,fit ,decide you're happy.Strap all the bits together and take it to the pressure treatment guy.Ask for the best and most expensive treatment.Result ...its cheaper and you get the stuff into all the end grain.

Sorry Bob, it works ...........not every boat is worth expensive timber. :D

[Bob Cleek]

Yea, but by the time you have it pressure treated, what's the savings? Some fairly decent plywood (this would be underlayment, not finish stuff) or MDO, well soaked with CPES, should provide a good surface for a Dynel or glass and epoxy deck surface. Pretty much what the original manufacturer probably used, less soaking it in the CPES. No, not every boat deserves teak or whatever, but there's no need to stoop to PTF!

[imported_Dutch]

out east here we gots PTYP. its built a lot of boats out this way and a couple of em actually lasted long enough to make it into the water

[Kev Smyth]

PT ply can be pretty good stuff- they treat the individual plys, then glue it up. Structurally it can be pretty ugly stuff, so maybe go up one size in thickness, but it will last almost forever.

[CJ]

If you do end up using the PT, be sure not to use any galvanized harware or fasteners. The new PT lumber has such a high copper content, that it causes galvanized to corrode pretty quickly.

[PeterSibley]

Hmmm Bob, here was the situation.

A mate in Brisbane who has a pretty respectable yard needed a large ponton to lay moorings and to moor customers boats to.The thing was going to get very little maintainence and basicly sit there until Hell freezes over.This is Queensland here in Oz...a very good place for Rot,kind of like Florida with a bit of Cuba thrown in.

The thing has sat there for 8 years and is just fine.It was originally assembled with cheap pine ply (1/2")and construction grade pine....money was short at that stage of the business.Screwed together with ss screws...done...complete ...finished.All parts numbered.Disassembled, strapped into bundles, pressure impregnated ,reassembled,epoxied and sheathed.

The thing has lasted very well...no rot ,no delamination.And cheap.

[Stargazer14]

OK, I got the nails down,
but finishing the Phillips heads on these bronze screws is a really taking some time!..... :rolleyes: