Holding Repair in Place Until Cure Below Waterline

[jpendoley]

Looking for some advice from this great forum...
While stripping gel coat for a barrier coat on my blistered hull, I found a poorly applied patch over a hole (picture attached). The boat had been holed years before I bought it and the repair was poorly executed with polyester. I was apple to pretty easily peel the patch off after lifting an edge with a couple of chisels...kind of sobering when you consider its a 2 inch hole...

I intend to repair with a 12:1 bevel and multiple layers of biax (1780?) saturated in epoxy. Access from the inside is not possible. I am looking for a way to hold the patch in place until the resin kicks. This will be a 24" patch when applied and its on a curved section of the hull below the waterline but not on the keel. I considered a screw jack on a jackstand but that does not conform to the hull shape. What would you all suggest?
Many thanks in advance.
Jim

[Jammer]

Peel ply
thin plywood that will flex

screws



Patch the screw holes after the main repair has cured


or make tiny holes in the hull for thin wire, twist wire together across the repair to hold it in place, again patch holes when done with the large repair. You will still need thin plywood and peel ply


or you can epoxy some wood blocks outside the repair to use as anchor points and then grind them off when you're done


or run a couple large webbing ratchet straps all the way around the boat. You will probably have to put a couple of them together end-to-end to get enough length. Put 2x4 blocking on the top and bottom of your plywood, on edge, to get more leverage from the straps


Lots of choices

[marcjsmith]

https://www.youtube.com/watch?v=4XoeGV2KhGc

andy does a good job talking through it with a demo... but he has the best situation where hes able to lay the hull horizontal


copious amouts of tape to hold things in place peel ply would be fine as would some 1/8" or 1/16" thick lexan on the outside to help conform to the shape of the hull somewhat this is nice since the epoxy won't stick really well to the lexan, plus it would give you the ability to "see though" it while you are laying it down to make sure that the glass doesn't move

[tkeithlu]

Patch, sheet of thin plastic, foam cushion, jackstand. If the curve is too great, start adding shims to the jack stand to make the cushion press about the same everywhere.

Build in layers, not all at once. The reaction is exothermic and you're not supplying muchof a way for heat to escape.

Consider slipping a piece of aluminum into the hole, tied to a string, as backing for the first layer.

[like-a-child]

Thumbs up on Tkiethlu. Dollar Tree has clear shower curtains that work great. Pop a hole and pull that string right thru the plastic. Plastic will release perfectly when cured.

[Spot]

Musing about a 'taquito' of plastic lid and fiberglass deployed on the inside of the hull...then do the rest as other prescribed minding the no-sand recoat window for the epoxy being used.


Anyone every vacuum bag such a repair?

[Dsanduril]

Vacuum bag with shop vac? Place patch, peel ply (for convenience), cover with a plastic sheet taped all around and fitted for attachment of vacuum nozzle, turn on vacuum. If the hole is big enough may need to put a rigid bridge under the plastic and over the hole so you don't get a dimple there.

[thinwater]

Backing is great, but the most important step may be to wet-out and roll the laminate before applying it to the hull. This will avoid heavy rolling against what probably won't be a rigid backing.



I would put a few layers of 1708 on the backing as well, and then finish glassing while that is still green. In this way, the repair is mechanical locked in place, not just bonded. Yup, done it before on skinny multi hull bows. Not hard.


As others have said, use screws to pull the backing tight, and then patch those tiny holes later.

[stormalong]

A two inch hole is not a structural repair. You do not need to feather it out 12 to 1. You will be wasting a lot of time and material if you do.

I have closed up several through hull tailpiece holes that were no longer needed. They have been in place for over a decade and from the outside you will never be able to find them.

Just feather it out evenly four inches diameter larger than the hole. Start with a clean surface and start building up the patch from small to large pieces, about four layers at a time alternating between cloth and mat. Use epoxy.

[nortonscove]

Make a small patch that will fit inside the hole using epoxy or polyester. Drill a small hole and put a piece of string out through to hold it in place. Glue it in place with autobody filler. A small stick across the area outside will hold it tight while the filler hardens. Once the filler hardens start with your layers. I prefer largest first for best adhesion while others prefer to start small. I usually do one layer to start and once that dries you can begin to buildup.

[JOHNMARDALL]

I'd put a one layer patch over the small hole in the center of the wound, let it kick, clean it up with a sander or grinder and then build up a full laminate patch freehand with no mold, as you'll be on a compound curve. I'd also put some cabosil in the resin to stop sagging. However you do it, don't forget that if you intend to build the laminate a few layers at a time, for control purposes, you must be sure to wash off with soapy then clean water the amine blush that will collect on the cured surface, before applying more layers. The same thing applies to the final work with fairing compound - you must get the blush off before fairing and between fairings if more than one application is applied.


Good luck
John Mardall

[s/v Jedi]

Cut out a 4” square of light weight woven fiberglass cloth, like 8 ounce. Put some plastic on the bench, brush epoxy on then stick the square of cloth on and brush more epoxy on until fully wetted out, but no excess floats on top.

Let that cure the use scissors to cut a 3.5” diameter circle out. Punch a hole in the center, fix a string to that, apply thickened epoxy with a finger through the hole around the inside, then to the patch, then roll up the patch to get it through the hole and secure in place with the string until cured.

[Nicholson58]

Originally Posted by jpendoley

Looking for some advice from this great forum...
While stripping gel coat for a barrier coat on my blistered hull, I found a poorly applied patch over a hole (picture attached). The boat had been holed years before I bought it and the repair was poorly executed with polyester. I was apple to pretty easily peel the patch off after lifting an edge with a couple of chisels...kind of sobering when you consider its a 2 inch hole...

I intend to repair with a 12:1 bevel and multiple layers of biax (1780?) saturated in epoxy. Access from the inside is not possible. I am looking for a way to hold the patch in place until the resin kicks. This will be a 24" patch when applied and its on a curved section of the hull below the waterline but not on the keel. I considered a screw jack on a jackstand but that does not conform to the hull shape. What would you all suggest?
Many thanks in advance.
Jim

Assuming you will fill with multiple layers of glass.

Taper to obtain a larger surface area. 12:1 is good. Use rough tools to make a better bonding surface.
Cut the patches small to fit in the base hole. I would consider one thin layer just to cover the hole and let it cure.
Prepare a stack of patches small to larger to progressively fill the void.
Use a 1” wide disposable brush to mix the epoxy and to apply to the hull and to the patch material.
Add layers until the repair is above the hull surface.
Apply a single layer of polyethylene film. A T-shirt bag or crinkly garbage bag.
Press and level the film into the patch. Squeeze the excess resin out as you compress the patch. Smooth the film and resin against the hull. Make sure you work out any air bubbles and voids.
The film should be self tending on such a small patch. Tape the edges down optionally using painters tape.
The film holds the patch in place, keeps air out, makes the surface near net smooth.
When:cured, the film will release cleanly.

I use US Composite 635 THIN resin 2:1. This is zero blush epoxy for fast wet out. It has a long working time and will take 3 days to become hard in a cool climate. You can add more to the build if necessary without cleaning or sanding (zero blush)

Epoxy :Â*Epoxy Resins and Hardeners


See my photos Nicholson58 on CF for some projects.

[jpendoley]

Great ideas from everyone thank you! I have been grinding the bottom so long I think I was becoming a bit addled about the process. I’ve patched some thru hull holes before, this one is different in terms of only having access to one side and it is larger.
One thing I would add is that it seems foolish to ever do a patch like this with polyester. The bond from the previous repair was really poor.

[Mikeiso1192]

Just been researching grp repairs myself.
Try this link it goes through the process step by step.