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Delamination of fiberglass from foam core on deck of 1973 Laser

David Jenkins

New Member
I have read many Laser Forum articles on delamination. But I still do not have a sense of what might be the best resin or glue or other adhesive to inject between the fiberglass skin and the foam core. Suggestions?


I believe testing has shown that epoxy based resins have better adhesion, especially in a mechanical type bond.

Common epoxy brands are West System, System Three, and MAS, I've used all three at various times and various situations and would have no preference for this type of repair...


yea.... but its heavy and purely a mechanical bond.. if you use resin it with chemically bond the fiberglass to the foam. I did a rail repair 2 yrs ago with resin and it's still strong as my new boat... Actually... repair is an understatement. I rebuilt a 3ft section of the starboard rail along the cockpit. I am now thinking about doing the other rain on my 91 boat and I am definately going to repeat the same process.

David Jenkins

New Member
Krycek, I believe that 49208 was advocating using resin, but epoxy resin rather than polyester resin. I do not believe that there is any advantage to using polyester resin over epoxy other than the cost is less. I believe that the epoxy bond will also be chemical and that it will be stronger than the bond made by polyester resin.

I was just about to use Evercoat polyester resin when I noticed that the instructions said to NOT use it on foam. Maybe the foam melts in the chemical reaction?

A few years ago someone on this forum suggested injecting foam from a can (via a syringe) between the delaminated fiberglass and the foam core of the Laser deck. There was never a follow-up to that thread and I worry that the force of the expanding foam might cause additional delamination.

I was thinking that a small amount of a water-proof, non-expanding, temperature-resistant glue might be the best alternative.


No matter what you use, it will still be a mech. bond between the existing laminate skin/foam and the resin. You only get a chem bond in a laminate when the resin hasn't kicked off in the whole laminate (ie during the layup of the boat, each additional layer of glass or core is bonded with resin and the resin is chemically bonded to itself thruout all the layers (except obviously thru the core))

Yes, I was advocated epoxy over polyester or vinylester for the superior mech bond properties.

However, the hull and deck are built using polyester resin at the factory, so using polyester will not be an issue with the Airex foam core in the deck. The warning on polyester resin applies to specifically to styrofoam. Polyester will consume it.. (Ie bad idea to mix poly in a styro cup, or try to build a styro surfboard and coat it with poly.

If you already have poly resin, it will work just fine..

The injecting foam idea doesn't really have much merit IMHO, the foam has both lousy adhesion properties and lousy shear and tensile strength, so it will break loose from the laminate and/or pull apart itself... It other words it's a crappy bonding material


I have read many Laser Forum articles on delamination. But I still do not have a sense of what might be the best resin or glue or other adhesive to inject between the fiberglass skin and the foam core. Suggestions?
A friend of mine actually removed his deck on his 125xxx series Laser and recored it because of extensive delamination. The original foam was definitely not Airex as it should have been. It seemed very much like polyurathane which is unsuitable for core. I've seen other boats with extensive delamination and suspect that they also have the wrong core since Airex is tough stuff. If this is the case with your boat, there is no resin you could use that will work for long because polyurathane foam is just too brittle.

My friend spent about 80 hours on the re-core job which included making a jig to hold the deck to the proper shape. His result was very good, but thats a lot of time and its not worth it to most people.


In regard to the guy who did the foam in a can repair a while back... I PM'd him last year to ask him about a follow up on his project and here was his response:

"It turned out alright, but the area become soft soon again. So I eventually had to inject it with epoxy resin and now it is keeping up good."


Super Opinionated and Always Correct
As a rule, the foam does not detach from the glass reinforced plastic (GRP) layer.

It is more a case of "something has to give" and that which failed was the walls of the bubbles within the foam core.

Usually, the delamination begins under the place where your butt has plunked down on the deck over and over and over and over until a few of the bubble walls under that area finally break...

Then, after your butt has won the "I bet I can bend you" contest the deck structure becomes much weaker and it begins to flex a bit.

The flexing means "something more has to give" and the thinnest weakest parts of the sandwich laminate are the walls of the foam core.

If the foam is still young and supple enouigh, the foam merely flexes. but when the core has been sun baked for enough seasons and cured simply by time and attacked by whatever solvents there are in the atmosphere...the foam starts to pulverize.

( on the boats built in the early seventies the foam wewas a very stiuifff urethane foam and it pulverized easily. By the time the boats with 20,000 numbers were manufactured, the builders had figured out the foam thing and no boat since has had the "wrong type of foam." That 125XXX boat mentioned above is now over twenty years old. I am one of teh guys who is most critical of "building crap that wears out" but unless you guys are willing to pay a lot more for your 130 lb hulls, you can kiss of expecting well over years of trouble free sailing.)

Eventually there is enough pulverized foam such that the deck top and / or bottom skins start to slide back and forth over the foam. The sliding process breaks more foam cell walls and the process weakens the deck and allows the process to accelerate.

Eventually, the boat develops a layer of (former foam) dust between the foam and one of the layers of GRP and about that same time, the deck becomes noticelably flexible.

if you inject something to glue the deck and hull back together, that substance, no matter what substance you use, MUST soak all around the dust particles and penetrate to the healthy foam and GRP surface or the resulting bond betwen the remaining foam and the GRP will be ...well...like gluing to any dirty surface....crappy.

The main reason epoxies work so well for regluing the layers is epoxies ( such as West System) do a great job of "wetting out" the dust piles.

The bad thing about runny epoxies is they settle to the lowest point and do not span from bottom to top of a void unless you entirely fill the void.

You can either inject a ton of epoxy or you can inject some epoxy and then squeeze the surfaces together...a vacuum can be used to suck the void shut....... Fists can be used as hammers to shake the liquid all around and past the dust piles. ..you can inject way too much epoxy and suck it back out repeatedly. ( hint, pout a sacrificuial extension on your mom's vcacuum cleaner hose...maybe even place a reservoir bottle between teh vacuum hopse and your sacrificial hose...steal a two hole stopper from the science lab...Your dad did it that way and it's your turn)
You can roll the boat over and over.

But remember...sucking the void shut takes constant sucking until the epoxy cures. many laser repair hobbyists have burned up their family vacuum cleaners by leaving them sucking on the deck for an hour or three. Unfortunatly even the fast West takes about eght hours to cure up to a decent strenght under decent conditions.

Ravi used my shop vaccuum cleaner to do his boat a few eyars ago and the top of the Geenie brand 6.5 horse vac melted its housing and fell into the cannister...it was funny because the vacuum was only three days old when he ruined it.... and Yes we did simply take it back to Builder's Square...many months later Builders Square went out of business...Ravi's fault!!!

On the second try Ravi set up a beer bottle with two hoses tunning through modeling clay. One dripped epoxy in the bottom of the bottle and the other sucked clean air from the top. He also rigged a relief hole on the hose with a sliding disc that controlled the amount of bypassing air. Once the deck void is sucked shut it takes very little pressure to keep it shut so he let most of the air leak into the big hose and the new vacuum stayed cool.)

So thinka bout all the stuff in this thread and fix your boat. it isn't rocket science.

Hint: if the entire deck is delaminated, fix a part that doesn't much matter first and maybe by the time you are actually ready to repair the parts where you sit..... maybe you will actually be ready to get it right.

It sure is a lot better to say "Yeah I did that part first and screwed it up and adjusted my systems for the rest of the boat... I did the important parts last and they all came put perfectly."

David Jenkins

New Member
Thanks, Laser friends. That is helpful information.

Just FYI, on this 1973 Laser the delamination is in small (3" diameter) areas all over the deck. These cannot be noticed in daylight but only at night when the headlights of the car shine parallel to the surface of the deck.


Super Opinionated and Always Correct
These are the sort that are most easy to repair and must be repaird to prevent spreading...If in fact they are voids...

You describe a problem that could relate to lots of other causes including, the foam may have swelled and caused teh humps.

Also, the samll areas could have been caused by something as simple as splotches of resin with a slightly different ratio of catalyst or sweat dripped from the laminator.

I think the answer still goes something like this...

1. Tap on the deck with a solid objest ( I said TAP not beat) I like a tiny ball pean hammer for this task. Listen Listen and try to determine by sound wheterh the hills are swelling of the core or hollow bubbles.

2. Drill a small hole and see if it is hollow in one of the mounds....drill somewhere where you don't care if the boat is "right" or not. Try something simple like a paper clip or stiff copper wire...will it spin around under the top skin and over the foam??

3. if they are hollow?? Fill them with an epoxy like West and maybe even try to push teh domw down for teh curing process.

I say MAYBE because if teh mounds have been there a long time, pushing them down might only help tear teh foam apart when teh mounds spring back up.

Of course if the domes are solid....don't do anything