How to fix gap in side of fiberglass hull

[aaronhl]

You are likely to need some kind of fairing compound and while I understand what Bondo is,I've never seen it or used it.If you mix your own compound using resin and microballoons,it won't be hygroscopic and can be shaped.Using the same resin you are repairing the hull with will be fine although for the first try you may have to experiment a little with catalyst ratios.Maybe by this stage of the process you will have realised why I prefer building a good temporary mould section on the outside and leaving as little finishing as can be achieved.It takes a lot less time to finish a 3/16" wide gel line than to create an entire surface that is fair.It does however require boatbuilding ability in a reverse shape.

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What about fumed silica rather than micro balloons, if I mix that with resin will it retain water? I have a lot of silica to use

I believe the way this section of the boat tore, it will require work on the outside even if I started with gel on the outside...

Its at an area with 3 gelcoat colors too so I don't mind having to repair outside since my goal is to repair the original gelcoat design

 

[Blueknarr]

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What about fumed silica rather than micro balloons, if I mix that with resin will it retain water? I have a lot of silica to use

I believe the way this section of the boat tore, it will require work on the outside even if I started with gel on the outside...

Its at an area with 3 gelcoat colors too so I don't mind having to repair outside since my goal is to repair the original gelcoat design

You will need to use both fumed silica and micro balloons.

Balloons make a soft putty that is easier to sand but also sags.

Silica putty is much harder to sand and doesn't sag..

I use about 90% balloons with 10% silica to get a non-sagging but still easily sanded putty.


A three color gelcoat repair is a tall order for a first timeer.

 

[aaronhl]

You will need to use both fumed silica and micro balloons.

Balloons make a soft putty that is easier to sand but also sags.

Silica putty is much harder to sand and doesn't sag..

I use about 90% balloons with 10% silica to get a non-sagging but still easily sanded putty.


A three color gelcoat repair is a tall order for a first timeer.

Ok just ordered some of that stuff, looking forward to working with that because resin and silica is sure tough to sand...

Good thing I am not a first timer with gelcoat then !! Haha

 

[ondarvr]

You'll need to sand off all the damaged glass from outside now, this area will require some glass to build it back up to the correct level of the surrounding area. Just some type of filler isn't going to cut it, it will crack as soon as the area is stressed again. The laminate on the outside is critical for it to reliably hold up long term.

Once you've filled it in with glass you won't need much filler to make it look right, so the amount of filler and sanding is reduced dramatically.

 

[yabots]

Grind a nice taper at least 10:1 ratio on the inside where you’re bonding. Use multiple layers of cloth and stagger them to rebuild the laminate thickness gradually.

 

[aaronhl]

Thanks for all the help everyone, so far this is where I am at, yesterday was a itchy day still feeling it today

 

[aaronhl]

I faired the outside surface with polyester resin+ microballons
So I plan to sand or grind down about a millimeter to then add gelcoat, the gelcoat will then be sanded and polished level to original gelcoat.
The questions are what type of edge do I need against the existing gelcoat? Should it be feathered, tapered, right angle etc ?

 

[ondarvr]

A millimeter is too much, half that is better.

It should taper out a bit, not a steep edge. An inch or so is all that's needed. More than that just increases the amount of work.

 

[aaronhl]

And what kind of tool should be used to skim only .5mm off the surface. like a 2/3" angle grinder with hard sanding pad?

 

[ondarvr]

Angle grinder, and maybe a soft pad.

 

[aaronhl]

Very good actually a 4" grinder and flap disc was what I was using before putting down the micro mix

 

[ondarvr]

This is one situation where a flap disc works ok. They tend to be slow in removing material so it's easier to not remove too much at one time.

 

[aaronhl]

it's getting there, seems like the outside fairing area is getting bigger and bigger !! I should have used the 6" air sander on the fiberglass before I put the gelcoat down. You can see where I sanded through, now with the surface flat I go go back and grind to add more gelcoat in the bare areas...have more sanding to do I am not going to leave the brush strokes in there

 

[ondarvr]

This is normal, that's why earlier in the repair I said pre gel coating what would be the outside surface wasn't of much value, you end up sanding it all off during this step.

 

[aaronhl]

I have been working in the garage on the topside spashwell during rainy days also. The way it ripped off the hull, it was flimsy and delicate. So far I took the damaged core out, reinforced the cracks, and repairs the rub rail area for new screw holes. The rub rail screws on both the top and hull had ripped through so the same repair will be done on the hull as well, cant think of much more to say but probably missing something