Repairing LARGE holes in fiberglass

[Ryan]

This isn't a specific question so much as a discussion type of thing. I have seen quite a few hurricane boats with holes in the hull as large as 3'x4'. Bearing in mind that anything is "fixable", is this something that can be reliably repaired, and if so, what are the philosophies about tackling such a project? I'm not concerned with the cost effectiveness of such a repair, just the techniques and methods that would be used.
The largest hole I have ever repaired was about 2"x24", but I would think that you would have to get imaginative with the larger repairs. I have even read of some manufactures repairing damage like this by putting the boat back into the original mold prior to starting the glass work. Any thoughts?

[kendall]

I used to do a lot of body work, and since I was the only one in the area who would tackle large fiberglass repairs, I was pretty busy with the kit car, BAJA bug, and offroad crowd.

What I used to do on big holes in heavily curved areas if the section wasn't available, was to make up a plug out of foam sheets that I would carve and sand to shape (surform tools and a vacuum are your best friends there!)
use trim adhesive and a hair dryer to wrap it with plastic and after waxing the plastic, use that as a form while rebuilding the fiberglass. after getting the first few layers of glass on, pull out the form and fiberglass the other side.

Friends used to call the method 'foam-a-fender', Made a complete custom front end for an old 850 spyder out of glass that way.

Results will depend entirely on skill level and preperation so actual results will vary

Ken.

[David VanDenburgh]

Hal and Margaret Roth performed such a repair after an incident in Chile, if I remember correctly. A large section of the hull required extensive rebuilding, including interior bulkheads. There's a decent description (and a few photos) in their book Always a Distant Anchorage. Probably not what you were looking for, but it's a good read and an impressive "salvage."

David

[Tim]

Actually, the incident David describes was in the Roths' book Two Against Cape Horn. A great story of a remote grounding, salvage, and repair in trying circumstances.

I'll have more of an answer later.

[David VanDenburgh]

Actually, the incident David describes was in the Roth's book Two Against Cape Horn. A great story of a remote grounding, salvage, and repair in trying circumstances.

I'll have more of an answer later.

Oops. Thanks, Tim.

Always a Distant Anchorage must have been the Bramble Cay incident. Another riveting account.

[Tim]

Repairing large holes will require a mold of some sort, against which to laminate the new material. Exactly how one creates this mold might vary from situation to situation, depending on the original part's curvature and profile, access to one or both sides, and many other factors. But the key component to repair of any large hole in a fiberglass structure is creating a mold that is sufficient to at least approximate the shape of the missing area.

On a damaged hull, for example, one way to re-mold the area for repair is to use the opposite side of the boat (in the same area) to obtain the offsets/profiles needed to repair the other side. There are several ways one could go about this, depending on skill, resources, and inclination.

The problem is, because the sides are opposite, you can't just laminate over the good side of the hull, using the hull as a plug, to create a mold for the opposite side--it will be reversed. In some cases, creating a new mold off an existing part might be a valid means of approaching the repair. It could, in some situations, even be possible to use an identical boat to create a new repair mold off the correct area of the hull, and then use this newly-created mold to place over the area to be repaired on the subject boat, thereby recreating the shape properly (or as closely as practicable, in any event).

In the Roths' grounding and repair situation mentioned above, which I might add occurred in the 1970s in a remote area of Chile only a bit north of Cape Horn, the repair was really the anticlimactic part of the whole saga. The salvage from a remote, rocky spit on which they were grounded high and dry was quite an ingenious event, but you'll have to read the book for that.

These Pictures reproduced from Two Against Cape Horn with this attribution, but no specific permission.







Repair-wise, once the boat was salvaged and brought to a Chilean naval yard, the method was to build wooden contour frames using the good side of the hull as a guide--each frame, set 12" or so on center, was scribed to fit closely to the (in this case) port side of the hull, overspanning the same area as the damaged section on the opposite side.



Then, each scribed frame was simply reversed on its vertical access--turned 180°--to recreate the appropriate shape on the starboard side, over the repair. To create the smooth molding surface, the inside face of the scribed frames was covered with thin plywood or some such.









This basic method, which of course is more involved than I can describe adequately here, would work well in almost any situation.

Ken's idea above of using bulk foam shaped to the general contours is a good one too, which might work in a number of situations.

In the end, there are so many variables that might affect how the repairs were effected, but the key is that nearly any damage can be repaired, given the time, resources, and inclination. One good thing about fiberglass is how well it can be repaired, assuming appropriate and basic preparation steps are properly undertaken (i.e. removing all shattered material, forming appropriate tapers and overlap areas for the new material, and so forth).

Large structural repairs aren't for the faint of heart, and would be a lousy place for an amateur to cut their teeth, but in few cases is damage to a structure so bad that it's impossible to repair. Large holes are daunting problems, of course, and require very large amounts of ancillary work (gaining access to the area to be repaired from inside being the largest part of this). As a result, it's often not financially feasible to consider the cost of professionals, which is why these damaged boats end up as CTLs in the eyes of the insurance companies. But that doesn't mean repairs can't be effected by a skilled person who is willing to undertake them.

[Ryan]

I have to get that book, just the pictures make me want to read it!

Thanks for all the details!

[The Froon]

Are those torpedoes behind the gentleman performing the repair?

[David VanDenburgh]

Speaking of Hal Roth, apparently he died Saturday, October 18, at age 81, after a 2-1/2 year battle with lung cancer.

[Tim Mertinooke]

Speaking of Hal Roth, apparently he died Saturday, October 18, at age 81, after a 2-1/2 year battle with lung cancer.

That is truly sad news as I have thoroughly enjoyed his books over the years. Now there's a guy who who lived the dream.

[keelbolts]

Please excuse my lack of correct terminology here, but often when building a wooden boat w/ steam bent frames you attach station molds to a strongback and run 1x1s, or something comparable, from one end to the other over the molds. They act as a final fairing check & as a place to clamp hot frames as they cool.

To patch a large hole in a plastic boat, I think I'd run lengths of that 1x1/4 lath, as temporary "stringers," inside or outside of the hole and attach them to the hull. If you start & end the stringers several feet on either end of the hole, they should take on a fair curve. I might even place the lath side by side for better support of the wet glass. I'd coat my stringers with wax before attaching them. There are a number of ways I could attach the stringers, but, if worse comes to worst, I could screw them to the hull & fill the holes when I was through. If I had easy access to the inside, I'd put the lath on the outside & lay up my patch from the inside. That way I could avoid working over my head and if it was winter I could put a heater in the boat to keep me and the curing layup warm. I'd want to balance my desire for warmth with my need to breathe. You'd get some sag between stringers, less if the stringers are closer together, but you could fair as required. It's pretty much what was done to the Roth's boat, only laid up in place.

What's wrong with my plan of attack? It seems quick & simple, but I've not done it in glass so I might be missing something.

[Tim]

That plan would work in many situations, but in some instances that sort of approach might not properly replicate the true shape of the area being repaired, depending on the nuances of the part's shape to begin with. The larger the area requiring repair, the less effective this approach would be, as just because lath or strapping forms a fair curve doesn't necessarily mean that it forms the exact shape of the part of the boat that's missing.

As an example, picture a missing area that had lots of tumblehome, flare, or hollow to it; the sections of the boat on either side might not have the same profile, and therefore wouldn't re-create the missing section accurately if lath was run across the area to be repaired.

It all depends. The idea has merit, but there are definitely situations where it would not work well, or at all.

But at a minimum, you'd need to leave room for a to-the-part-side smooth surface or plywood or other material, as no matter how you go about building the you can't have gaps when you're laying up fiberglass, and the smoother the "mold", the better the part and the less fairing required. I wouldn't lay up a large seciton of hull over a series of wooden laths, no matter how close they were. Thin plywood would provide a much smoother surface, and more fair from the getgo.

Obviously there's room for many approaches to a repair such as this. Each situation would likely vary enough that there's definitely not a one size-fits-all solution. Keeping various ideas in the mental bank is always a good idea; one never knows which one will be the right one for a given situation.

[Jason K]

This is a little off topic but, based on this thread, I ordered a used copy of Two Against Cape Horn from Ebay. If you haven't read the book, get it and read it. It's a fast and fascinating read and the book is full of amazing photos.

---- Now back to your regularly scheduled thread.