Fiberglass repair recommendation.

[Memopad]

If you want to match hull thickness, go from both sides then. Half and half, you won't have to bevel 12inches, just 6 right? Don't worry about using roving and CSM. Just simple cloth will do. Have any left overs from other projects?

 

[Ajax]

I cannot grind 6 inches around on the interior of the hull. There is a glassed in bulkhead, immediately adjacent to the hole (aft).

I can only grind 180 degrees around the hole.

 

[estarzinger]

Ajax,

How thick is the hull here? I am assuming it is pretty thick, which means that we don't have to do a really fancy repair. Edit: if its an inch thick that's great - some people would epoxy a 1/4" or 1/2" thick puck into the hole (not sure if that's possible or not with your V shape) to reduce the layups - 1/4" of layup on both sides is more than enough.

Epoxy is technically better. Polyester is 'good enough' and quicker and cheaper. Your choice.

CSM sands really nicely, saturates with resin really well, does not print thru (and is cheap 'bulk' when you have a thick laminate). It is however not strong.

As to cloth, just go to the chandler and get whatever they have. They will have something like a 15oz biax. It really honestly does not matter with this repair.

It is a simple repair and if I were doing it I would go with quick and easy in all the choices . . .EXCEPT . . . .I do think you need some repair on the outside. Just repairing it from the inside would 'probably' be ok, but would make me uncomfortable. Some cloth on the outside makes it bullet proof. A bit overfilled patch with CSM/polyester resin on the outside is easy to shape/smooth with a grinder/sander (as is epoxy filler).

A 6" circle bevel (on both sides) is plenty.

Edit: yes, do paint with barrier coat. Probably not necessary if you do the repair with epoxy, but can't hurt. Will help blend the repair into the rest of the bottom.. And you may have some exposed original hull laminate, which I presume is polyester, where you do want the barrier coat.

 

[Ajax]

Here's a top-down view of the problem.

There's a thick, glassed-in bulkhead or dam under the cabin sole/liner. The hole is immediately forward of this bulkhead, so you can only grind around about 180 degrees around the hole, on the inside of the hull.

 

[Ishmael]

If you do use epoxy, don't use CSM: the mat does not wet out properly with epoxy. One yard of 6 or 10-oz cloth will give you all the material you need to fill the hole. I wouldn't take the 12:1 bevel as gospel, if you can't make it in one section just give whatever setback you can. Because of the increased strength properties of epoxy you can get by with less structural thickness so your extreme outside layers could be entirely fairing, so you aren't sanding cloth. A mixture of 406/410 will make it so it doesn't drip out the hole but it will still sand or grind relatively easily. Make sure you put a couple of coats of neat epoxy over the filler to totally waterproof it.

 

[BobBill]

I would go with Ishmael's take. CSM sucks up resin and offers little strength...I am still having a bit of a problem imagining the repairs, but if this opening is less than a foot in dia, should not be too difficult. Remember, epoxy is very strong, when used with appropriate materials, like glass and carbon, and you can alternate layers to be biaxial etc.

There are examples galore...

I would advise this, even if practiced:

Make a list of tools and materials needed and check it twice at least;

Make another list of the procedure or process as well.

Once you start, finding later that you missed cutting a piece or are short resin/hardener, etc, it can be messy and turn the process upside down...as most of us who play with building and glass know.

You are, in a sense, dealing with serious stuff...though not so mysterious.

 

[CasualObserver]

I would never ever use polyester resin below the waterline.

Nor would I trust a shop that does.

If your timeline precludes epoxy use a vinylester resin.

 

[BobBill]

Yes epoxy is the ticket, but poly does work...I mean, aren't all glass boats poly? But, repairs are best epoxy, no doubt...better slow and safe, then wet and so on.

 

[Ajax]

Ok, the good information that I've finally got from this thread:

- Skip the CSM with epoxy.

- Anywhere from 10-15 oz cloth.

- Rotate to get the biaxial effect.

- It is acceptable to grind back 6 inches inside and outside of the hull, even though I can't get the full 360 degrees inside the hull.

- Epoxy is good.

- 406 and 410 fillers.

- Barrier coat.

Estar- Yes, i think the hull is going to be pretty thick there, and I might end up doing the epoxy puck. I woud do the inside/outside repair not only for security's sake, but also because it lets me only grind a 6" bevel on the outside. That's less filling, sanding, fairing and painting.

Grinding the bevel inside the boat, is going to be difficult and require a small grinder. It's cramped, even when I rip out the V-berth and potable water system. Thank God I don't have a holding tank or black water hoses to contend with.

 

[Rain Man]

There is one problem with using epoxy for this job. Epoxy in thick layers can start to exotherm to the point of smoking and a poor bond. The solution is to stop and let it cure from time to time. However, if it cures too much, you now have an amine blush on the surface that somehow needs to be removed to ensure a good bond between the layers. Hard to do in a hole.

So, while epoxy would normally be the material of choice, polyester will be just as good because the bevel on both sides will lock the lamination in place. Because of this, bonding with the existing laminate isn't really much of an issue with either material. However, if epoxy is used, and the job stops in the middle, there is a possibility of a poor bond between the layers of epoxy due to the amine blush.

Bottom line, if using epoxy, don't take a lunch break. Epoxy will definitely be nicer to work with inside the boat than polyester. I find that it is a little harder to get epoxy to completely wet out thicker cloth, so I would stick to lighter cloth, or completely wet out the cloth before putting it on the repair, which is messy.

dash

 

[Rain Man]

....

Grinding the bevel inside the boat, is going to be difficult and require a small grinder. It's cramped, even when I rip out the V-berth and potable water system. Thank God I don't have a holding tank or black water hoses to contend with.

Borrow a dremel tool - for a small amount of work like this in cramped quarters it will be easier to control and less likely to produce damage than a grinder.

good luck!

dash

 

[Ajax]

Based on what I watched on various Youtube videos, I'll have all of the cloth ovals or discs pre-cut and other necessary materials pre-staged so that I don't have to stop.

If I use a slower hardener, will that help keep the temperatures down? I also hope to do this in the spring, when temperatures are low to start with.

 

[Grande Mastere Dreade]

If I use a slower hardener, will that help keep the temperatures down? I also hope to do this in the spring, when temperatures are low to start with.

No slow hardener means you get a longer working time...

the pieces of glass cloth in the patch is going to give the epoxy the additional strength and it takes up enough space so you don't have a large glob of epoxy in a small area which may exotherm..

to see am example of epoxy heating up... take 2oz's of WS 105 and the appropriate amount of hardener into a 6oz plastic solo wine cup and mix it up... don't ask me how I know..

you know once you do this, you're going to be looking around the boat and seeing what else you can fix.. good luck and have fun

also you'll want..

go to harbor freight and buy a bunch of cheap rubber coated gloves to wear while you're doing all this

buy a couple of bottles of 90% isopropyl alcohol , it will clean up the epoxy resin..

bunch of stir sticks from west systems.. they're very handy

plastic paint mixing cups for mixing the epoxy... ( the epoxy once hardened will pop right out )

plastic sheeting and packaging tape to keep epoxy off everything you don't want epoxied..

 

[Ajax]

Dread-

I appreciate the explanation about the hardener.

I have done some work with WS epoxy in the past. I've recored a power boat transom, a locker hatch and a cosmetic hood over a sliding companionway hatch, all with WS.

In all three cases, the stuff was very structurally sound. The powerboat transom was a cosmetic disaster. I was unable to lay up a new skin that didn't look like total shit. This is my big fear with this repair.

 

[Grande Mastere Dreade]

no worries then, sandpaper and fairing filler will be your friend..

 

[Bugsy]

Ajax,

I would like to step back for a second: I was part of the chorus encouraging you to take this on yourself (I am a complete amateur and I have done jobs similar to this, so I am encouraging you as well).

I think the consensus here is:

- just roughing up the area around the hole and slapping some plain old fibreglass would probably be an adequate solution.

- choosing the right materials, grinding to form a bevel, and planning your work is a good solution

- making a patch from both sides, a plan for the specific types and order of cloth, identifying the best resin, etc, will lead to an excellent solution

If you had gone to a yard, there is probably no way for you to know what was done, what materials, etc. and not much ability to determine if the solution was adequate, good or excellent.

Doing the work yourself, I think you can know you have an excellent solution. And if cosmetically it isn't perfect, well, there is no guarantee a yard would do any better. With time and effort, you can make your repair look good or do like I do - just hide the imperfections

Congratulations on taking this on!

 

[Memopad]

The beveling around the hole is partially to get a good bond with the new material, and mostly to blend the repair area in with the rest of the hull structurally. This isn't a structural repair so don't worry so much about it. Your boat is perfectly happy having the hole in there now, no loss of strength, everything is happy. Essentially you're just plugging this hole to keep the water out, not adding strength back to the area. So bevel what you can, whatever looks good to your eye will be fine. You just need enough of an edge so you can layer some glass in there so each layer is inside the previous. Easy peasy. Don't forget to put the biggest piece of cloth in first, and end with the smallest!

 

[stickboy]

I'm not convinced you need to make a large area bevel, especially on the inside. On the inside it doesn't matter at all, thicker is better, on the outside you can fair out the extra thickness over an area unless you want to git rid of the gelcoat and adhere directly to the glass. That bulkhead you are up against under the v berth I think you'll find isn't tabbed to the hull all the way to the centerline, it's definitely open right at the center. You might be able to cut that bulkhead up enough to slide a few layers of cloth under it. If not you could consider running your cloth up like tabbing but I'm not sure I'd want the bulkhead working against my plug/patch.

I WOULD taper the edges of the hole itself so that you aren't making a straight sided hockey puck but instead a slice out of a cone. Think of pounding a tapered plug into the hole from the outside and trimming off the excess.

Wait, is this already a flush through hull that you're pulling? if it is, that's just about the taper you want the edges of the hole to be. A Dremel will work well for this, a router would be OK if you weren't working right on the V.

Forget about the cosmetics, that's going to be so easy you'll wonder why you even considered it. It doesn't have to be pretty, just smooth and that's just a matter of sanding.

 

[hard aground]

Is the hull solid, or cored?

 

[BobBill]

Ajax is finally getting it and the advice here is good...particularly the question re cored from hard aground. Does make a big difference and adds steps if it is cored...also some minor stuff. I still do not have an idea of the size of the opening that will need to be filled.

One can make much thicker glass out of thinner layers...instead of 10-12 oz glass...a square yard of 4 oz s-glass and a bit of carbon goes a very long way...

Gloves, whatever source, the blue is safer...big box.

Slow or medium epoxy...is often simply a different hardener and mix ratio...they all heat up as the molecules begin racing around looking for a mate. Mix thoroughly, say 50 twerls each way, and not so fast as to create air born bubbles?

As implied, patience is an ingredient. Slow epoxy takes longer to kick and cure. You want to work at a pace that allows each batch to be set up on a slightly tacky former batch and create what some call a structural bond, rather than a surface bond...without the bother of removing amine blush etc. Yes, that means getting up at 3 am to work on it...the epoxy dictates the schedule...it is slow but sure, if done right.

Your concern for finish is good, but comes after the structural need, and if careful, the finish (exterior) can be finished fair...and it is under water...inside, whatever suits, especially if out of sight.

Like we noted, make a friggen list of materials and use and list the work schedule...particularly if this is not something you do every week...you get my drift. You really do not need peel ply, expensive, when kitchen wrap with some wax paper atop will serve for fairer final layer.

Last, if cool outside (4 degrees here) a heat lamp before, during and after, not too close to work does wonders.

And, almost forgot, if air bubbles appear in cloth layup, a very swift fly over with a torch or heat gun will pop them...you do not want air trapped.

Happy New year Ajax...fun and if you can note the hole size (I might have missed) please add.

A bevel from the outside, as slight as it might be, is best to offset foreign pressure...

If there is a wood core, say balsa, it needs to be dried, removed or solidified and so on. That is a PIA, but important issue.