Resin/F'Glass/Rebuild Question

[John F.]

A friend I fish with liked my B20 so much this summer that he bought a B20 hull to have redone. The B20 needs everything--demolition, new stringers, deck, transom, etc. He's talked to a couple of f'glass guys that are local. One guy whose name he got from the guy he bought the hull from gave him a great price for doing the work. I recommended he get some detail as to materials, and the guy came back that he'll use wood or Coosa for the stringers, transom, and deck, but will use polyester resin for everything--no epoxy.

I searched through the threads here, and from what I've read, polyester resin is the wrong stuff for building and bonding new stringers, transom, and a deck. Maybe for laying up the deck, but not for bonding it in or bonding the new stringers and transom to the old hull.

Any insight/advice would be appreciated.

Thanks-

[CamB25]

John,

Ian Upton just did this to his 20 before he left for Indonesia. I'm sure he will offer excellent advice. Too bad the 25 site is gone as he had a complete picture record there.

For my project we used epoxy for all structural elements. Zero Ve so far. Poly used for deck panel fiberglassing over and under the Coosa boards to save cost.

John P. at Wharton Creek?

[John F.]

Not Whorton Creek, or any of the other places around here you may have heard of. Local guy.

[Buju]

Well, the boat was built with 100% polyester... So, based on that alone, it cannot be the "wrong stuff".

There are stronger resins for sure, such as vinylester and our beloved epoxy resin. But that great price he got in the quote will begin to rise steadily if he decides to step it up on the resin. One can pick up a gallon of polyester and mekp for about $40. A gallon of epoxy resin and the hardener is gonna be around $120. Albeit thats more or less retail pricing... but that's a substantial difference once you start looking at quantities needed to redux a B20 in entirety.
Polyester is by far the most economical route, and if the guy does good prep and good work, it should meet and exceed its required characteristics for the build, in all aspects.
There are several grades of polyester resin... I'd wanna know exactly which polyester he's using, some are junk.
And, based on the "coosa OR wood", I'm putting all my money on him using wood. Otherwise it wouldn't mentioned.
If your buddy wants coosa used, then specify it... If he does, I'm betting the price rises.

[John F.]

I understand that Bertram built boats with polyester. I was under the impression from reading here that epoxy was to be used in certain areas of rebuilds, like tabbing in new stringers. Is it fair to say that poly is fine as long as its done right, but that epoxy is preferable? Is it worth the extra cost to have the guy use epoxy over poly? He's getting another estimate from another guy, and that guy told him he'd do the rebuild with 100% epoxy and composites--I think divinicell. His ballpark was alot higher.

[mike ohlstein]

I believe that the general rule is that the poly/vinyl-ester resins are great for monolithic layup and general construction. Epoxy for its adhesive qualities.

Laminating stringers or laying up a hull? Polyester. Resetting the rudder ports or the shaft logs? Epoxy.

Epoxy is glue. Polyester is not.

[ianupton]

John -

I used vinyl ester through out.

I went back and forth, but finally decided on the 'ester resin.

I think prep work is the key to all of this.

If you look at any new built boat, they only use ester resins. They have secondary bonds throughout. Again good prep work is in my opinion the key.

Some of the tabbing could be pulled off by hand in my 20. I know my tabbing is better.

I have most of my pictures online if you'd like a like to them.

Btw, I went with coosa as well.

I just hope after all is done, I get a chance to live close to the water again.

Ian.

[mike ohlstein]

April 2009

Harry,

Polyester resin is not an adhesive and will de-bond from plywood rather easily. And Bondo has a place in my heart on the same level as chrome plated potmetal by Perko.

If you're going to make your deck from plywood, you really need to glass it with epoxy.

Br,

Patrick



April 2012

Daniel,

Polyester resin is NOT an adhesive.

For both the teak and the formica you must use epoxy. There's no practical reason to glass either side if they're to be overlaid with either teak or formica. Just prime all surfaces with thin, but fully wet, epoxy then laminate with a thickened mix of epoxy and cabosil.

Be sure to use a brand new sheet of formica that doesn't have any warp or curl to it...

Br,

Patrick

2008

http://bertram31.com/newbb/viewtopic.ph ... y+adhesive

[CamB25]

Ian - I seem to remember that you used pre-formed foam stringers for replacements, but I can't remember the brand.

[IRGuy]

I hesitate to post any comments here because there are plenty of regulars here who have done orders of magnitude more work with vinylester and epoxy resins than I have.. but I did recently complete a rebuild of my B33 in which I used almost 3 gallons of epoxy. Three things I did learn though during the past 2 years however bear noting here...

1 - Epoxy seems to shrink over time.. even after it seems to be completely cured.. there is a flat panel on my flybridge where I epoxy filled several screw holes, and sanded them smooth to the touch.. 3-4 months later the boat was painted, and on the shiny paint surface I can see very minor, but still visible, depressions where each patch is.

2 - Epoxy will bond to vinylester.. vinylester WILL NOT bond to epoxy!

3 - Epoxy has excellent gap filling properties.. vinylester does not. This is why cold molded boats are built with epoxy.

I welcome any comments more knowledgeable people here might care to make.

[ianupton]

The stringers that I used were from http://www.preforms.com/

I was very happy with the product.

Ian.

[Tony Meola]

I think at the end of the day only time will tell us.

I have talked with a couple of glass guys who learned from the best. One was taught by Jack Henriques another laid up glass for Vicking Yacht. I knew the guy who worked for Henriques pretty well. He was well respected for his glass work. He claimed if you know what you are doing you don't need to use epoxy.

Who is right, lets see in about 10 years we will know.

[Peter]

Most of the consumer polyester resins you can buy at the local boat shop or hardware store contain lots of solids. This effects the properties of the resin in both layup and performance. Basically they are junk. They also contain some additives to extend shelf life which may reduce thier performance as well. A good shop needs to buy better resin than the local hardware or marine store junk.... but the stuff has limited shelf life, so your basic home owner DIY guy probably doesn't want to buy 5 gallons of it. There are a lot of good suppliers out there.

Also most polyester resins you can get at the Home Store or Marine Store contain a wax additive. This is used to block air from reaching the exposed surface of the polyester layup and inhibiting the curing process. Not surprisingly it is called "Air inhibited" when there is no air-barrier (suchs as the the wax additive, or a female mold, or wax paper, or plastic sheeting) .....and when air-inhibited the exposed surface stays tacky forever.

If you use a polyester resin with a wax sufacing agent you will never get a really good bond for the next layer even if you prep the dickens out of it. That is beacuse the molecular chains are completely cross linked and the only bond you can get is by mechanical means. Like rouging up the surface and sanding off the wax which then creates a bit of a griping surface for the next layer. But it is just a mecanical bond, not a chemical one.

BUT there are resins readily available and used throughout the industry that do not have wax. For these the air exposed surface never fully cures, or at best continues to cure pretty much forever..... the molecular cross linking is incomplete at the surface exposed to air.... and it always feels tacky to the touch..... and the next layer of polyester applied over it bonds by not only mechanical means but also by cross linking to some of the molecular chains.

Surfers call the wax added resin "surfacing resin" or sometimes "sanding resin" and the non-waxed "laminating resin" so you might hear these terms used. It can be confusing because the surfers tend to use a different venacular than boat builders, but a lot of information is available from that angle and the two lexicons are sometimes mixed together in discussions. Also the surfing community is a great source for a variety of different HIGH QUALITY resins (poly and epoxy) in small quantities suitable for the home boat shop.... but you need to decode the lingo.

It is important to NOT USE waxed resin for laminating or things will likely delaminate no matter how carefully you think you preped and sanded.

The wax agent can be bought seperately and added in the shop to the last layer of resin to make a hard curing surface.

Epoxy sticks to cured poly just fine...... poly doesn't like to stick to cured epoxy.
Poly sticks to itslef just fine if the previous layer IS NOT waxed. Poly doesn't stick to itslef quite as well if the previous layer was protected from the air when it cured by wax, or a mold or a covering of wax paper or plastic.... or was deep within the lamination originally and thus not exposed to air.

If it were me, and I was talking about bonding new stringers into an old polyester hull where I probably have to prep the inside hull surface by grinding down through the top layers of accumulated grime and into polyester underlayers that were fully cured at the time of the original build.... I'd spec epoxy for the stringer-to-hull bonds.

Polyester or vinylester is fine for layup of new parts... or for places where you are more or less just filling in holes or tabbinbg in non- structural trim.... but not expecting structural stresses..... but get "laminating" resin for the layups and add the wax which you buy seperately for the top layer only.

Peter

[Raybo Marine NY]

we have thousands of poly repairs standing the test of time,transoms, stringers, decks, run aground damage etc.

its just as much about procedure as it is what materials you are using