Poly or Epoxy?

For a delamination I had on my 1979 H16 (on both hull decks just infront of the front pylons) I used polyester due to its lower viscosity (i.e., it flowed better). I wanted the best coverage between the glass layers so I used 14G needle in inject the resin into a small hole in the center of the delamination (the hole just penetrated the first glass layer into the foam, but not the second glass layer under the foam) untill it ooze out holes I had made on the sides of the delamination. After the repair the hulls remained solid, though I did tend to avoid standing on the repair.

Use epoxy. It's better for bonding, which is what you're trying to do in the case of delam. You're bonding the core back to the fiberglass skin. Epoxy will flow just fine. Plus the longer cure time will allow you to make sure you get the epoxy into every nook and cranny before it kicks off. While you're injecting the resin, have someone flex the soft spot to "pump" the resin around the hull. Also, be sure to wear eye protection as the resin has a tendency to squirt out of the vent holes.

sm

Here are the holes I drilled.

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1974 Hobie 16 (not to mention my age, but that's the year I graduated from High school)
1993 Hobie 17 For Sale
JMBoatStuff

If you mask off the holes ahead of time, you will save yourself a lot of clean up work.

sm

Not following? Do you mean mask off the center area so the resin doesn't get in the non-skid?

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1974 Hobie 16 (not to mention my age, but that's the year I graduated from High school)
1993 Hobie 17 For Sale
JMBoatStuff

I mean place a 2" x 2" wide piece of masking tape over each hole and punch a hole through it (actually what I would have done would be to put down the masking tape first and then drill through the tape and into the deck). This way when the epoxy oozes up out of the vent holes, it doesn't get all over the deck and into the non-skid. Otherwise you'll have blobs of epoxy around each hole and all in the non-skid. You're going to want to have some paper towels handy too to wipe up excess epoxy. You may even want to mask off the whole area with tape and news paper. Once the epoxy gels, you can peel up the tape. This can be a fairly messy job because your going to have epoxy coming out of each of the holes.

sm

Gottcha, very good point and I think a little slow some days.

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1974 Hobie 16 (not to mention my age, but that's the year I graduated from High school)
1993 Hobie 17 For Sale
JMBoatStuff

To anyone reading this forum down the line:

Simply put...the info about epoxy and polyester resins that fastcat has put out on these hallowed Hobie forums is 100% bad advice.

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Ha! You two crack me up! Jeremy, Fastcat, I appreciate all the advise you two post.

Me being a newbee to any type of glass work (although I am an engineer and have taken many materials classes) my chemistry experience is low.

Before I read all the Posts between you two and the other Hobie gurus (just did that last night) Tap Plastics advised me to use epoxy to repair my crack/fault ridden 86 redline 18. I have now repaired almost all the cracks under the lip, sucked in epoxy in cracks in the leaking dagger well seams and have added at least 1/8" to the very worn bottom.

The hulls being white, I have added some white coloring to the epoxy to help with the color matching issues. (Not sure why I don't see people doing this more often with epoxy).

Now comes my issue of Gelcoat. The epoxy I added to the dagger wells and underside lip around the front cross bar (with layered glass) are not visible when the boat right side up. The epoxy I put on the bottoms is visible although match pretty well. Should I try to spray these areas with gelcoat and blend them in with the existing/remaining factory gelcoat? If I chose not to use gelcoat, will the epoxy discolor over time if I left it alone?

I have read the posts about sanding/cleaning the cured epoxy before the gelcoat application but I have put in way to many hours now to create a problem for myself now.

Thoughts?

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H18 '85
H18 '89 "Knotty Passion"
H20 '96 "20/20 Vision"
Fleet 259 Central Coast California

Your gelcoat dilemma is pretty much at the crux of the polyester vs. epoxy debate, and the reason why polyester based products (and not epoxies) are recommended for laminating and external surface repairs. If the pigmented epoxy is a close enough match, I'd just leave it as is. Otherwise, maybe paint (white appliance spray paint?), but then you get into issues of mix-matched gelcoat & paint and it becomes a mess if you or someone else has to do work down the line.

On another note, you should be sure to do internal reinforcing of your hulls using fiberglass cloth at the front crossbar (through the access port). And also install the upgraded shroud anchor plates if they haven't been installed already. 1986 is a known problem year for 18s, and by the sounds of it, yours has (had) some problems.

sm

Yes, Thank you.

It looks like to me that the previous owner added the reinforcement plates after the damage happened. The work I have done under the lip is to suck the epoxy into the cracks while creating a vacuum in the hulls. Some of the cracks were very leaky and large so I included some fiber cloth to help create a bond. I am planning on adding the epoxy and cloth on the inside also once I flip the boat back over. I am hoping to do all this without adding more than a few pounds to the boat. My plan is to use this boat only on lakes and keep my '81 H18 for sailing on the ocean. I just don't think this boat will hold together on the California Coast.

Don't like the idea of paint.

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H18 '85
H18 '89 "Knotty Passion"
H20 '96 "20/20 Vision"
Fleet 259 Central Coast California

My boat is an '85 and has the same cracks by the crossbars. Simply sucking epoxy into the cracks is not sufficient to fully and properly repair this damage. You really need to grind back the damaged fiberglass and re-build the hull structure by laminating new glass. The tensile strength of epoxy is only a fraction of the tensile strength of glass fibers, so the epoxy will just crack if the damage isn't properly reinforced. You need to add glass to both the inside and the outside if you want the repair to hold up.



Neither do I, but it may be your best option if you aren't satisfied with the appearance of the pigmented epoxy. Using gelcoat is likely to cause problems. The other option would be to grind off the epoxy and re-do the repair with polyester.

sm

Man I can't catch a break, even when I agree with Jeremy (i.e., use polyester) he disses me. WOW and really Jeremy 100% bad advice - you must of gotten beat up pretty bad on the playground as a kid or your whitie tighties are binding. Maybe lack of attention in kindergarden during people skill training. What is interesting is that in the 28+ years that I have repaires my boats (I tend to run into things at a greater frequency than one would like), I have YET to have a repair fail. Can you say the same?

I am not dissing anyone, but you guys sure hijacked this thread!

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1974 Hobie 16 (not to mention my age, but that's the year I graduated from High school)
1993 Hobie 17 For Sale
JMBoatStuff

Diss away! I've spent over 20 years in the sailing industry. My first job in the bizz, was gelcoat application and glass at a boat yard near the Hobie factory. I've repaired hundreds of Hobie hulls. I've done things the wrong way, learned, and made them right. I've seen my customers do repairs thousands of wrong ways, waste money, waste time, and wind up with an inferior product.

Not that any of this matters, but when some backyard repair guy wants to go head to head, and spread the absolute wrong way to do things, on forums that will be on the internet indefinitely, I find it insulting. I mean what's the motivation? To look cool, like he knows something?

I'll tell you my motivation. To teach people that they have the ability to do these repairs on their own, the right way, without spending a ton of cash. That all they need to do is have a little knowledge, and they can be self sufficient, get their boat on the water, and have a good time. The ability to repair gel and fiberglass is a really neat skill set to have.

Here's my latest fiberglass project. This 33' boat was damaged in the Tsunami. I cut out the sole and glassed in some traditional floors.





The rudder was ripped off, so I built and relammed a new rudder tube.

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