Refinishing a boat with a rough surface

2 weeks 6 days ago #35663 by mrcharly
So I have an old K1, Kevlar resin build I think. No foam core. Super, super lightweight, it is only 8kg.
The only flaw with the boat is that the finish on the hull is a bit rough. I think that they kept the gelcoat as thin as possible to keep weight down when it was built, to the extent that the weave can be felt through the gelcoat. 
In a few places, this is more than a bit rough.
My options are:
  • Try to paint some gelcoat on (I don't have access to somewhere warm to cure the gelcoat). Could wait for summer I guess.
  • Use a wax, like Starbright, like the dinghy sailors use, and hope that it fills in the scratches a bit and gets the surface a bit smoother. 
  • Anything else?

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2 weeks 5 days ago #35664 by Ranga
It's like asking how long is a piece of string? To give any advice more info is needed, pictures would give a better idea of what you are talking about.
If it's Kevlar that is exposed, that's not going to be easy.

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2 weeks 4 days ago - 2 weeks 4 days ago #35669 by RichardCampbell
I know a boat builder He has home built plenty of boats, and trys and finds the easy and cheap way to do thing, Not rough and dodgy, just has heaps of time to research different methods, And another guy that has built a lot of boats.
They often put small section of 2 pack epoxy resin on exposed fibres, They use peel ply cloth to remove the wax, Or you can use thinners to remove wax
They use wet and dry and get the hull glass smooth, working rough through to fine grades, They then use 2 pack paint and brush paint it on, Making sure the paint is warm, And they can often use normal exterior house paint. They warm it using an outer container with the paint in the container inside.The results they get are very good.
Being a K1, i dont know what size room you have inside, but you can heat a room up and paint it in there.
Hope this helps, and my 2 cents worth
Richard

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2 weeks 4 days ago - 2 weeks 4 days ago #35670 by mrcharly

Ranga wrote: It's like asking how long is a piece of string? To give any advice more info is needed, pictures would give a better idea of what you are talking about.
If it's Kevlar that is exposed, that's not going to be easy.

I took some photos last night - then carefully left my phone at home.

On close examination, the areas that are roughest to feel are just starting to expose the kevlar weave (no gelcoat over the weave at all).
Structurally absolutely sound.
Starting to make me think that painting over with resin then very careful sanding back with 800grit wet and dry would be the way to go. [edit] looking at this resin  epoxy coating resin
What do you think, Ranga?

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2 weeks 3 days ago #35671 by Ranga
Everything and anything is possible if you have enough time on your hands. Kevlar is by far the hardest to refinish. Yes coating with an epoxy resin will help but doing it once? Like refinishing wood you varnish and sand back and repeat until you get the finish you require.

You cannot sand Kevlar, it is an aramid fiber, it has to be surrounded by resin. All you are doing is covering over the fibers until completely under the resin. 

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2 weeks 3 days ago #35672 by mrcharly
I realised I was searching for information with the wrong parameters - my boat has very similar construction to a Wenonah canoe (sans the foam ribs). They have been around for many years, get hard racing use. So I searched for info on refinishing a Wenonah and bingo, lots of info.

Confirmed I'm thinking along the right lines. Comments say that these boats never had a 'gelcoat' as such, more of a 'skincoat'. Painting on epoxy (not polyester) resin, gentle sanding smooth, is a pretty regular thing to do with a Wenonah boat. So I think that is a sensible approach with my kayak. 

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2 weeks 3 days ago - 2 weeks 3 days ago #35676 by MCImes
If you do not have fuzz coming through the resin, your life is much easier. It sounds like this is the case. If you only refer to the rough weave pattern, then painting on a layer or 2 of epoxy and sanding smooth is your ticket.

Note, sanding epoxy to a near gloss finish sucks, so you'll want to do a nice job to begin with or else you're in for a lot of manual labor. 

Make sure you clean the boat well with acetone or some other medium-strong solvent. After rough the surface if the boat if possible. (I say if possible because you do not want to fuzz up the kevlar if the skin coat is exceptionally thin or worn). Some manufacturers put a thin layer of glass over the kevlar to resist fuzzing as the boat wears. Its hard to see since glass becomes clear with resin, but its worth a check by sanding a small spot to see if there is anything between the skin coat and kevlar. If there is indeed a layer of glass, you can sand without as much worry.

If you do more than 1 coat, you either need to apply the 2nd coat while the first is partially cured (as in firm but not cured), or else wait for a full cure of the 1st coat, then wash off the amine blush with acetone (the cloudy appearance on the surface of some epoxies after curing), then sand with rough grit sandpaper. Amine blush will inhibit adhesion of the next layer. 

Something to note - I forget where I read it, but I believe that scratches/dents/imperfections less than .008" (.2mm) deep do not affect the hull because they are inside your static boundary layer, so that water is getting dragged along with the boat whether its perfectly smooth or all .008" imperfect. Maybe a fluid dynamics nerd can confirm this. 

Currently - Swordfish S in Southern California's ocean waters
Past Boats: Epic V10 g0, Stellar SR g1, Fenn XT g1
"When you've done something right, they wont know you've done anything at all"

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