hope this hasn't been covered too many times...

...i tried searching for this but i couldn't find anything. i've never owned a sailboat before. i did learn to sail a few years ago (it wasn't a cat, just an 18' hampton day sailer), and i think i remember enough to get in and out of the water under normal circumstances. i'm looking around here in southwest florida for a hobie cat for around 600 bucks. i'm guessing that, for this price range, i can expect to find some soft spots.

i've surfed and repaired surfboards for many years, and i'm wondering if it isn't possible to repair delams with polyester resin? i've fixed a ton of delams on surfboards this way, and it sure would be nice if i didn't have to learn how to work with epoxy when i'm already more than competent with the other stuff.

Cyrano,
I'm relatively new to sailing as well. I purchased and 83 H16 for around 800 bucks. After the first season I noticed some soft spots on the deck of one of my hulls. If you look around on this forum you should be able to find a ton of info on how to repair delam areas. I put up a recent post asking a similar question and had many responses that may answer some of your questions as well. Look on the 16 forum under "Delamination-Git Rot Clarification". The sailors on this forum are extremely helpful and supportive.

As for buying a boat, I think most of the people on the forum would agree that it is probably best to buy a boat without any soft spots. Delamination in front of the foward pylon is a serious structural issue. If you do get a boat and there is delamination, I would use the epoxy injection procedure that is found on this forum from Matt Miller. It has been used by many sailors and is time tested and proven. I just fixed a large delam area on my starbord hull a week ago using the epoxy, "Git Rot" , injection procedure and I have no experience working with either resin or epoxy. This stuff comes in kits and it is literaly as simple as pouring one bottle into another, shaking it up, and then slowly filing the delam area. The procedure is suprisingly simple, it just takes a little time, patience, and cold beer.

If you have any questions feel free to ask. I am in no way an expert on this subject but I did just do the repair and the hull seems solid. Good luck with finding your boat.
James

certainly appreciate your response, but i still would really like to know why everyone is advising those who repair a delam to forego polyester resin in favor of epoxy resin. why won't polyester resin work? i don't disbelieve that it won't, i'm just wondering why.

I used polyurethane to repair a soft spot I had on my starboard hull just after I got the boat. It worked really well, and after a summer of sailing it is still very solid. The foam expands just a tiny bit but not enough to hurt anything. I did the repair next to an access port so I could check and make sure that there was no damage.

I know that none of the guys on here suggest it but I do not see why not to us the polyurethane. The only problem is that it is thick. I used oral syringes that you can go to any pharmacy to get, to inject it into the hulls. In my mind that seems better than the other method because you can make sure it really spreads out to all the little spots.

My argument in favor of this type of repair is that the foam is polyurethane, so in my mind it can't be a bad thing. But i am sure some of the more experienced guys will disagree and just say go with the gitrot method.

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Cyrano,
I'm certainly not expert enough to give you a definate answer as to why one is favored over the other. I believe that one of the reasons is that the expoxy resin still has some forgiveness after it has cured. From what I understand this works well with the stresses that are placed on the bow. I've never worked with polyester resin so I can't really say which is better. Maybe the polyester resin doesn't have the flex that the expoxy has? I can say that the Git Rot stuff, when used at the right temperature, remains fluid for quite some time and is easy to work with. It is a penetrating resin and from what I can tell does a really good job soaking into the foam and bonding with the glass. It also does not absorb any water, which I have found to be the argument over foam. I'm sure some of the Old Salt's could answer you better. Good Luck with whichever method you choose. Have you found a boat yet?
James

After I read your question I did a quick search to see if I could find something to justify using epoxy resin over polyester resin. You may find this site to be helpful in answering your question.
http://redrockstore.com/resin.htm
It explains the advantages and disadvantages of both substances. It would appear that the epoxy resin does a better job bonding with the glass layers. Take a look and see what you think.
James

Folks,

I didn`t have time to read the posts thoroughly so I apologize if I am repeating someone`s advice - but I don`t think so.



...Polyester resin for delam on a Hobie ? Nope.

- the reason is really simple. Polyester resin dissolves foam - aggressively. Try it out for yourself on some scrap foam.

So, you sure as heck don`t want to inject it into a foam core structure like a HobieCat.

Another problem with polyester (assuming say a Balsa core construction) is that it can can go off too fast or too slow - especially in an injection type application where dickering with the proper amount of catalyst can be tricky. That is to say that it will harden either too quickly (too much catalyst / too high ambient temp), or, conversely, not at all because of too little catalyst in an effort to address the previous problem. Either eventuality may ruin, or at best degrade, the entire delamination repair. Epoxy tends to have a more predictable cure rate.

Also, someone suggested Epoxy has more "give" than polyester. This is not the case. Epoxy creates a more rigid, stronger laminate with less give, using less resin than with polyester.


Cheers

Dave

Captain Dave is exactly right about not using poly for the repair. I design and build 1 meter RC sailboats and do a male plug using blue foam and wood stations. After doing my first plug and getting it just right I planned to fiberglass it to make a rigid plug to pull a mold from. The first drop of polyester resin went right through the foam and before I could pull back a big glop hit the foam and ran down the side and destroyed the plug. It ate that stuff like water through cotton candy. I could just see a disaster in the making injecting poly resin into a foam core boat. Not a pretty picture.
I would suggest being patient and finding a boat without delams. I bought one this last summer in a much sparser market than Florida. It took about 2 months and looking at 10 or so boats before I found a solid '83 that needed some work but was basically sound. I did pay $1000 for the boat, but it was in excellent condition for an '83. The hulls were a little yellow, so I buffed it out (7 inch rotary sander with a wool pad) using a product called Bar Keepers Friend. It is an abrasive powder, but very fine and I believe it also has some gentle bleach in it as the hull came out white and glossy again. Be patient and find a sound boat.

Wait a second guys...Let's think about this.
If polyester resin disolves foam core, then how is the glass laminated to the foam core of say a H16 during manufacture?

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Jeremy,

It depends on the foam they used (polystyrene vs PVC or polyurethane). And, in some cases the construction method used.

What foam is used in a HobieCat is not known to me; or whether it is consistent throughout the model years.

I would suggest this is probably not something for a beginner to take a chance on. Especially in consideration of the advantages of epoxy for this type of repair.

Dave

I asked as a rhetorical question, because since Hobies are made of polyester if the foam used in the manufacture was dissolved by poly then the entire core would dissolve the first drop of resin that touched it. It would turn to a sloppy mess with no structural integrity.

The foam core used in Hobies is called Divinycell (Type H "general purpose" I think) and is basically impervious to all types of resin systems--Epo and Poly.
You might be thinking of Styrofoam, like those cheapy coolers. This type of foam is sometimes used in Epoxy surfboards and will definitely get eaten by polyester or even just Acetone.

So to clarify, the foam used in Hobies will not dissolve when polyester resin is used for repairs. (Please use polyester for general repairs and epoxy for delam everyone!)

I think the reason to use Epo in deck repairs are as stated: Reliable cure time and flow. Also Epo creates a stronger bond than poly, so it is well suited for bonding the skins back to the foam core, which is what you want to do when fixing delam.
Hope this helps.

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Great info on the foam Surf City. I was really concerned about people using the polyester resin on these boats. Good catch.

it's definitely not polyurethane, because that's what kind of foam we use in surfboards and i've done numerous delam fixes on them. having said that, if everyone agrees that epoxy is the way to go, then that's what i'll use. it can't be too much harder to use than polyester.

i bought a boat, by the way. i paid $1100 for an 87 hobie16. as far as i can tell, it's solid. the sails are crisp and tear free, but some of the plastic clips at the end of the batten holders (i don't know sailing terms--sorry) look like they've seen better days, though they aren't falling off or anything. it needs new ropes, but the shrouds are new, the tramp is new, and it came with a crappy trailer. there's no spinnaker, but i'll have my hands full just figuring out how to drive the damned thing with a main and a jib, anyway. i sailed a bit when i was younger, but it's been about ten years.

Cyrano,

You will find that a good quality epoxy is easier to mix and use (in most cases) than polyester.

The foam that polyester melts is polystyrene. PVC and polyurethanes are resin safe for the most part - although I have not personally worked much with them.

Regarding the specific foam used in a HobieCat core, I believe Jeremy has identified this and his advice sounds pretty good - in general. However, I do not necessarily agree with his logic that since the boat was intitially made with polyester, than the foam core MUST therefore be polyester resin safe. One reason for disagreeing on this is because there are construction methods where foam is added to a resin laminate AFTER the curing process - either poured/expanded or blown into place. Although this is not the case with Hobies, in other applications it might be.

One application I personally have experience with was with the construction of large RC aircraft wings. The method involved cutting the wing core from polystyrene foam and then bonding a polyester laminate skin over the foam core using epoxy. We used the epoxy due to its better adhesion properties and its polystyrene compatibility. But, all future repairs had to be done with epoxy regardless of the fact that the laminate was made from polyester.

I mention all of this not because I disagree with Jeremy - he was able to identify the foam in a HobieCat whereas I could not. I mention it because the assumption itself could lead to troubles.

-when in doubt, use epoxy.


Cheers,

Dave