Soft Hull spot...help please

I looked at some of the other posts on hull delamination repair and didn't see the technique I discuss below, so I thought now might be the time to weigh in.

First, though I have not repaired Hobie hull delaminations, I did build surfboards (using Clark foam, polyester resin and glass), and a Rutan derivative two-place foam-fiberglass sandwich aircraft (using Epoxy resin). Fiberglass Hobie Cats as well as most fiberglass boats are made with woven glass fabric and/or glass mat, Polyester resin, and often have a (foam, balsa, honeycomb, etc.) core. Most of the delamination repairs being mentioned here discuss using Epoxy resin- because Epoxy bonds to other materials better, is less viscous, kicks off (cures) slower and does not generate damaging heat that can result when Polyester resin cures.

Building the airplane required many large fiberglass layups with multiple glass layers. It was critical to thoroughly wet out each layer of glass with Epoxy resin while not overly saturating it- to maintain strength but keep the weight down. That required very low viscosity and slow curing resin. Due to the amounts of resin and the accurate mixes needed we used Epoxy pumps that had resin and hardener reservoirs. The pump would draw from the reservoirs and supply hardener and resin in the correct proportions to our mixing cups. We went one step further and put the pumps into boxes with high wattage light bulbs or small heaters. The heat lowered the viscosity of the Epoxy which flowed much easier than normal. Unfortunately I do not remember what temp we heated the resin to.

I believe applying the same principle to repairing Hobie hull delaminations would be beneficial. A less viscous heated Epoxy mix could be injected into the holes and would flow throughout the delam area much better than more viscous, unheated resin. You can find more information on this technique by going to the Experimental Aircraft Association, Aircraft Spruce and Specialty Company, and other web sites dealing with fiberglass aircraft construction. I would certainly experiment with heating and mixing the resin and hardener and watching cure times, before attempting a hull repair.

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Alan
'86 H16, Sail #89057

That's the good thing about the "git rot" epoxy. It's pretty straight foward, just add the bottle of catalyst to the epoxy, mix for one min and inject. I did my repair over the winter in, and this is just a guess, 50 degrees on average. I had no problem with the viscosity of the product and had plenty of time to do the repair. Heat will speed up the cure, cold will slow it down, but in both scenarios it will cure reguardless. Plus, it is way less expensive than having to buy the amounts needed from West System as the delam repair takes suprisingly little expoxy. But, I'm no expert, I can only speak from my experience repairing one boat, mine.

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James
86' Redline Hobie 16
Sail # 76909

Lot sof good helps coming out so thanks for that.
I'm picking up some syringes today which I hope will allow me to use more force to inject the resin.
James, thanks very much for answering all my questions. You mention you made just a couple of tracks in the foam with a nail. Even though these don't meet up, will the resin still make it to the other holes becuase of the amount of pressure we're using to squeeze the fibreglass in?
Do we actually fill the whole foam cavity up or do we just create some solid resin "shapes" which reinforce the foam space?

Thanks again everyone

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Anthony
88 H16 "Moonshine"

Yes, even though the channels do not meet the epoxy should penetrate from one to the other.

This is how I understand delamination. Hobies are made by a foam sandwich, meaning a layer of glass(bottom), a very thin layer of foam, then another layer of glass(deck) that is covered with gel cote. This method creates a strong, yet lightweight hull material. When delamination is present what has happened is that one or both of the layers of glass, for whatever reason, has lost it's bond with the foam. That is why it feels soft or sounds hollow/squishy. So when you inject the area with epoxy what you are essentially doing is re-bonding the loose glass layer(s) back to the foam. If there is delamination, there will be a "void" in the sandwich where the expoxy can penetrate.

Also, when you do the repair again, which I hope is successful, make sure you keep going back to your boat until the epoxy has cured. Sometimes, it will seem like the deck is full and you come back later to find that it will still accept epoxy, it's like it keeps sucking it up. Take a few cold beers with you or the beverage of your choice and just take your time with the repair. I literally spent hours doing mine. If you are in a warm climate, which I don't think is the case, just make sure not to leave the expoxy in the heat while you wait to see how well it took. Let us know how it goes. Like I said, I did my repair a while back and my deck is still hard as a rock after hard sailing (both lake and sea), and a steller pitchpole last weeked digging in the repaired hull. Too bad the insides of my boat are going soft too, but soon it will be time for a upgrade. But I'm going to keep sailing her till she breaks I'm afraid.

I've said it before and want to say it again, If it weren't for the folks on this forum I wouldn't have had a clue what to do about my soft hulls. Thanks to Matt Miller for his postings and the rest of the hobie community for there support to novice sailors and ancient boat owners. Well, maybe not ancient but definately older than most products you can still get support for. What a company.

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James
86' Redline Hobie 16
Sail # 76909

Just looked at your album James and the pictures help heaps. What size holes did you drill? They look reasonably bigger than the "small" holes suggested by the Hobie technical help. All depends on what "small" is, I suppose.

We're just heading into summer now so I'd we hit about 80F+ yesterday so the resin is curing reasonably quickly. I got too much hardener in the first batch so it went off in about 5 minutes so changed the recipe and the next beatch took about 20 minutes before it went off.

Will have another try this afternoon and let you know the result.

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Anthony
88 H16 "Moonshine"

5/32 for fill holes

1/8 for breather holes

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James
86' Redline Hobie 16
Sail # 76909

Another technique to keep everything together after injecting the epoxy and to avoid injecting too much and creating a bulge is to drill a hole all the way through skin-foam-inner skin. Then insert an "L" shaped rod. After epoxy has been injected and spread around (best to do this with hull on its side) stick the "L" hook in and pull the sandwich together until everything hardens. Remove the hook and plug the hole.

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Alan
'86 H16, Sail #89057

Has anyone an opinion on whether I should redrill the original holes or drill new holes to try this process again? Just popping out to get some syringes now which should allow me to put more pressure on the resin than a squeezy bottle. Gunna fix this hull once and for all this afternoon!

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Anthony
88 H16 "Moonshine"

Okay, now I see what should happen.
I drilled some 4mm holes. Made some paths in the foam with a bent nail/bent wire. Used some 60ml (not sure what the imperial equivalent is) syriungs bought from the veterinarian's surgery I squeezed in lots of resin and it even came out the other holes, just like the manual said it would/should.

Thanks heaps for your help.

Lessons learned: Use a syringe, not a squeezy bottle. Make tracks in the foam - not sure if this is necessary with the syringe as you can get heaps more squeeze than a bottle but certainly helped. Don't put too much hardener in each batch!

A couple of holes seemed to take an endless amount of resin so I wonder if I've peirced the inner layer. I guess the thing to do here would be to dribble a bit of resin in every few hours until it blocks the inner hull and then I can fill up the cavity that is left?

All up - used about 700mls of resin - one hull required holes 3/4 of the distance in front of the front pylon, the other had a soft spot around 1 foot long.

Now just gotta sand 'em back, apply the gel-coat, and then go sailing. Any problems if I go sailing before I apply the gel-coat? Gel-coat is on order (I live in a small town) and I need to go sailing on Saturday (tomorrow is Friday and it is Thursday night here now).

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Anthony
88 H16 "Moonshine"

You can sail without the gel. But, definately make sure you've given the epoxy enough time to cure, which I think by Saturday it will be solid. You really dont have to apply gel over it, but I certainly understand that you probably want to. Just remember, gel doesn't adhere to epoxy very well. So make sure you sand off any excess that got on the hulls. Or, if you want to go the extra step this is what I did. Take a slightly larger drill bit than what you used for the holes and drill "dimples" into the repair holes. Now, I mean just barely make an indentation in the holes, not even through the first layer of glass. Then fill the dimples with polyester resin, or marinetex. That way when you go to gel you know that it will adhere. Gel does adhere to polyester resin. That way your repair is almost invisible. Have fun sailing Saturday. I've been hating having to be at work during the day as we've had three straight days of wind up to 20 mph.

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James
86' Redline Hobie 16
Sail # 76909

Thanks abbman. I've actually used fibreglass resin in all the repair becuase I'd read that expoxy & gelcoat don't really work. I guess the resin may take on a bit of water but cn always dry out next week before I gel-coat it.

First sail of the season down here in NZ. Summer's arriving! 15 knots forecast and reasonably flat ocean so should be a good day. Thanks so much for all your help.

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Anthony
88 H16 "Moonshine"

I had several large areas on the sides of my 1980 h16 and I repaired them with west system. I ended up drilling about 100 holes on the side of one hull and and about 50 on the other (2 inches apart) and they are still doing well 3 years later.
Later I found a small delaminated spot on the side and I tried the Gorilla Glue, the delam area was only about 3 inches in size and the gorilla glued area is still ok in that small spot. I wouldn't use in in a much larger delaminated area.
John G.

Be very careful with Gorilla Glue- it is a polyurethane glue that when activated by moisture (normal curing) it foams/expands to many times its original volume. If excess glue/foam can't expand out through the holes it can actually cause the glass and foam to separate and.or create a bump in the hull at that point.

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Alan
'86 H16, Sail #89057